SUMMARY REPORT MERCURY CONTAMINATED SITES · 2015. 2. 24. · To conduct the soil vapour sampling used, thin metal insertion rods were used to introduce samplers employing Gore-tex®

SUMMARY REPORT MERCURY CONTAMINATED SITES NICOLE Technical Meeting 4 December, 2012 Brussels, Belgium Event hosted by Solvay

Report compiled by Marianne Blom, ENVIRON

Report on the NICOLE Technical Meeting: Mercury Contaminated Sites

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Acknowledgements

NICOLE gratefully acknowledges:

• The speakers and chairpersons for their contributions to the meeting • Solvay, for hosting the venue in Brussels • The members of the Organising Committee:

o Laurent Bakker - TAUW, the Netherlands o Roger Jacquet – Solvay, Belgium, Chair Organizing Committee o Thomas Keijzer - Deltares, the Netherlands o Oliver Phipps - ERM, UK

NICOLE is a network for the stimulation, dissemination and exchange of knowledge about all aspects of industrially contaminated land. Its 100 members of 20 European countries come from industrial companies and trade organizations (problem holders), service providers/ technology developers, universities and independent research organizations (problem solvers) and governmental organizations (policy makers). The network started in February 1996 as a concerted action under the 4th Framework Programme of the European Community. Since February 1999 NICOLE has been self-supporting and is financed by the fees of its members. More about NICOLE on www.nicole.org

http://www.nicole.org/�


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Contents 1. Introduction 4

1.1 General .................................................................................................................................. 4

1.2 Background: Mercury in the Environment ............................................................................ 5

2. Opening session 7

3. Characterization and Investigation 8

4. Modelling, Risk Assessment and Remediation 16

5. Concluding Remarks 25

1: List of Participants NICOLE Technical Meeting

Appendices

2: Program NICOLE Technical Meeting


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1. Introduction

1.1 General

This year’s technical meeting on mercury (Hg) contaminated sites’ was held on 4 December, 2012, hosted by Solvay at Solvay’s offices at Rue de Ransbeek 310, Brussels, Belgium. The meeting was held following growing interest among industry and an identified need within NICOLE to collate and assess information on the management of mercury contaminated sites.

Over the past decade and in the near future, it is anticipated that numerous industrial sites where mercury is used or has been used will be closed, triggering a need for investigation, characterization of soil and groundwater quality and a likely need for management measures for human health and/or environmental risk. Mercury (Hg) contamination at industrial sites is commonly associated with current/former chlor-alkali plants, however there are also other industrial applications of Hg-compounds, e.g. wood impregnation, oil and natural gas production, batteries manufacture and recycling, other manufacturing activities (thermometers, electrical switches, Hg-lamps), Hg-based catalysts, etc. Investigation and remediation techniques to date have ranged from generic approaches to metal contamination management and remediation, to increasingly Hg-specific selected approaches.

Hg has properties (liquid metal, surface tension, vapour pressure) which make it unique and which render characterization of Hg contamination at industrial sites a challenge. Distribution, transport and migration are unlike that for other (inert) metals found at industrially contaminated sites. Characterization is furthermore challenged by Hg’s unique behaviour in the environment.

From a regulation stand-point, Hg has been listed as a priority hazardous substance in the EU that is subject to phasing out (see the Section 2 Opening Session below). In this regard, the EU Council and the European Parliament on 22 October, 2008 adopted the regulation on the banning of export and the requirement for the safe storage of metallic Hg (regulation (EC) No 1102/2008). The export ban has been in place since 15 March 2011. Hg use will be allowable in future under only strictly controlled cases. In addition, the United Nations through its United Nations Environment Program (UNEP) aims to reach an internationally legally binding treaty on mercury in the near future.

This technical workshop on Hg contaminated sites was aimed at the identification and dissemination of state of the art strategies, techniques and technologies which support the management of mercury contaminated sites while also minimising risk and maximising sustainability.

Following this introductory section 1, this summary report contains the following sections: • Section 1.2: prior to addressing specific topics presented in each session, section 1.2 provides

a summary overview of Hg in the environment, as a means of setting the scene • Section 2: Opening Session • Section 3: Morning Session on Characterization and Investigation of Hg contaminated sites • Section 4: Afternoons Session on Modelling, Risk Assessment and Remediation • Section 5: Discussion

The report summarizes presentations and discussion which arose at the workshop. For a review of the full presentations and abstracts, please see the NICOLE website (www.nicole.org).

This report reflects the conclusions of the NICOLE network meeting and the outcome of discussions. This document does not necessarily reflect the opinion of NICOLE and/or individual NICOLE members or member organizations.


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1.2 Background: Mercury (Hg) in the Environment

Prior to presenting the individual presentations in Section 3 below, this section 1.2 provides a global overview of Hg transport and behaviour in the environment, as taken from the subject matter outlined in the speaker presentations. Some of the information presented here represents background information included in speaker papers and not necessarily presented at the meeting. In addition, references are provided for further reading and/or tracking.

The second and third presentations given by Valérie Guerin (BRGM) and Dick Brown (ERM) respectively included fundamental principles to bear in mind when conceptualizing and characterizing Hg-contaminated sites.

The conceptual cycle includes various forms in which Hg may be encountered and identified during investigation, and the many routes of Hg transport and distribution in the environment. These were not extensively discussed during the technical workshop, however it is worth noting that in addition to distribution through direct spills on to land, Hg can notably be distributed as particulate matter through air, and re-deposited on ground; and/or Hg can react, change species and/or physical state, and relatively easily migrate across environmental compartments of air, water and land.

The cycle extends well beyond the boundaries of a single industrial-property. While these further reaching processes and considerations may not at first glance appear to be of immediate concern for the average soil investigation project, the further reaching processes keep Hg on the public agenda. Also, because Hg arises and is investigated in so many environmental compartments, it is key for soil researchers to be aware of the public dialogue, wider-reaching studies, and key concerns on Hg-toxicity; as these clearly affect policy formation and clean-up expectations for land-based contamination. For further discussion of this matter, see Section 5.

During the course of investigation of industrial properties and during the review of the presentations given at the NICOLE technical meetings, it was key to identify and understand at an early stage the physical and chemical form of Hg potentially present. As noted in various presentations, Hg species typically found at industrial properties are:

• Liquid metallic Hg (particulates, vapour) • Hg salts • Organo-Hg compounds

In addition, characterization of the speciation and the site geochemistry and biology are, as also stressed in presentation nr 3 by Dick Brown (ERM), key for a) fundamental understanding of the system; and b) development of remedial objectives and approach. The significance of speciation is illustrated in the Pourbaix diagram for Hg and Cl and S (Cl and S are not uncommon elements found in combination with Hg at industrial properties). Note that the diagram below is an example of Hg for one system. Other bio-geochemical systems would yield other Pourbaix diagrams and Hg-speciation reactions

:


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Figure taken from presentation 3: Hg Pourbaix Diagram with Cl and S

Hg speciation is a key consideration in the assessment of surface (water) systems; and should be considered in land-based systems as well.

Mercury speciation and fate and transport are key considerations in the assessment of surface (water) systems; and mercury behaviour and speciation is noted to be receiving specific additional attention through the research institutions, for example the internationally formed project group (BRGM, funded by Ademe; SCK-CEN funded by OVAM; the SGI funded by SEPA; and CLAIRE) for enhanced knowledge in mercury fate and transport for Improved Management of Hg soil (ImaHg), which is scheduled to present a report in March 2013.


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2. Opening session Session Chair: Roger Jacquet, Solvay

The workshop was opened by Roger Jacquet, chair of the NICOLE working group on Hg and industrial contaminated land. Roger welcomed the audience to the technical meeting. The technical meeting was set up following the expression of a growing interest in Hg, partly driven by legislative and regulatory developments in the European Union (EU). Key regulatory developments within the EU include:

• Regulation (EC) N° 1102/2008 banning export and on requirement for the safe storage of metallic Hg, in place since March 2011;

• United Nations Environment Program to reach a legally binding treaty on mercury – on going. There is an aim to reach agreement by / in 2013;

• Voluntary commitment of EUCHLOR to close or convert chlor-alkali* plants to the membrane technology by 2020 --

o acceleration of closing of mercury cell chlor-alkali plants, o post closure management issues;

• Hg in the EU is a priority hazardous substance; * Other industrial activities using or formerly using mercury include wood impregnation, batteries, manufacturing lamps, electrical switches, mercury based catalysts

in addition to national and local regulatory developments which may be in place within the Member States.

Roger noted an upcoming conference for those interested in further tracking the global dialogue: this is to be an International Conference on Mercury as a Global Pollutant on 29 July - 2 August, 2013 in Scotland (www.mercury2013.com).


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3. Characterization and Investigation Session Chair: Roger Jacquet, Solvay

The morning session of the technical workshop included presentations which can be grouped to have addressed primarily characterization and investigation

of mercury contamination at industrial properties.

High Resolution Passive Soil Gas Sampling for Elemental Hg Characterization Jason Cole, CH2MHill, Germany; Greg Schaefer, CH2MHill; and Jay Hodny, GORE & Associate

Presentation Nr. 1

The presentation by Jason Cole concerned field investigation of elemental Hg, through the use of a soil vapour sampling technique that is relatively cheap and easy to apply over relatively large sections of properties, for a wide-scale initial assessment of elemental Hg

A case study presented concerned an 11-hectare military facility that had been in operation since the 1950s. Historic releases of Hg were thought to have arisen, as a result of maintenance, breakage, and disposal of Hg manometers. Access to potentially impacted zones was complicated by building/ paving structures and underground services. Application of the passive soil vapour survey allowed the investigation team to access difficult areas for an initial screening, and to narrow down the number of soil boreholes potentially needed, of > 300 boreholes, to 20 boreholes.

. The results of the soil gas sampling can subsequently be used to narrow down and select high impact and/or potential source areas for the more expensive soil (borehole) sampling and analysis.

To conduct the soil vapour sampling used, thin metal insertion rods were used to introduce samplers employing Gore-tex® membranes at selected soil depths across a relatively tight grid (lateral spacing of ca. 4.5m to 6m between sample points). The advantage of the Goresorber® samplers is that these are inert, water-proof and vapour permeable. The borehole is subsequently corked, the sample taken and analysed. A drawback of this approach is that analytic and field tests do not yield Hg concentrations. The information collected concerns total mass adsorbed to the sampling membrane. Extrapolation to (likely) concentrations is difficult and subject to error, and direct comparison of results with regulatory standards (which are usually expressed as concentrations) is not possible.

Available technologies and new insights to better characterize Hg contaminated sites Valérie Guérin, BRGM; Valérie Laperche, BRGM; Jennifer Harris-Hellal, BRGM; Daniel Hubé, BRGM; Hossein Davarzani, BRGM; Hubert Leprond, BRGM: Thibauld Conte, BRGM; Jean-Philippe Ghestem, BRGM; Romain Millot, BRGM; Manfred Flum, SolGeo AG, DE; Jörg Schäfer, EPOC-University of Bordeaux, fR; Harald Biester, University of Braunschweig, DE.

Presentation Nr. 2

The presentation given by Valérie Guérin opened with a brief overview of a conceptual Hg cycle for soil (i.e. land-based environments), followed by a presentation of testing results for on-site and laboratory technologies performed by the authors to characterize Hg at contaminated sites. Due to physico-chemical properties of Hg, the characterization of Hg-impact is often incomplete and subject to significant uncertainty.


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With regard to field investigation, it is recommended that investigators aim to collect samples which provide best information on in situ conditions. Undisturbed core sampling (freeze to preserve if necessary) is preferable to trial pits. Trial pits lead/allow for condensation processes and for displacement of drops, giving in false spatial information on Hg distribution.

Soil

A test case was presented.

In addition to taking core samples for later laboratory analyses, it is possible to immediately apply field testing for Hg-characterization. Two types of field instruments were discussed which complement each other with regard to method detection ranges:

• Lumex RA 915+: equipped with a pyrolysis attachment RP 91C (AAS). The instrument yields data in the range of 10 ng/kg – 200 mg/kg; i.e. samples with more than 200 mg/kg Hg can be problematic.

• Field portable Xray fluorescence analyser (FPXRF). This instrument yields data for concentrations of Hg from 10 mg/kg and higher.

Application of field testing for both soil vapour and soil can give immediate preliminary information on (possible) Hg partitioning between gaseous phases and the others forms (particulate, inorganic form, etc).

Other observations and conclusions: total Hg concentration provides little information on risk. Information on the mobile fraction of Hg is key for risk of volatilization or leaching (and therefore risk).

Chemical methods used for soil speciation include leaching and extraction, however these are not easy to implement and there are difficulties in the interpretation for sequential extraction. A physical method use for speciation (pyrolitic) has proven useful for HgS and Hg0; but appears less applicable for Hg chloride salts (Hg2Cl2 or HgCl2). The test case site had "Hg-Cl”. [See the presentation 3 for further discussion on the importance of conditions, speciation and solubility.]

Analysis of water samples is usually carried out in the lab rather than in the field. However some field testing is possible. As a note on field work during water sample handling: use of Teflon bottles washed with HCl acid is recommended as a good means of preventing cross contamination. Ensure the (conservation) acid used is Hg-free, as acids can also serve as a source of various contaminants, including Hg.

Water

With regard to water speciation, the team distinguishes among the various forms of Hg arising from various means of treatment of the water sample (e.g. filtration of sample and treatment with BrCl2 yields information on HgD = Hg°+ HgR + HgC; however acid digestion followed by analysis yields information on HgT = HgP+HgD):

• HgT = total • HgP = particulate • HgD = dissolved Hg • HgR= reactive • Hgo = gaseous • HgC = colloidal / residual

Analysis of water samples for methyl Hg was accomplished with the use of isotopic tracers and GC-ICP-MS analysis.


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Soil Vapour

Gas characterization was accomplished with the use of sample analysis. Various techniques were used for sample collection and analysis, including passive and active gas sampling in the field for laboratory analysis, and direct (field) sampling and analysis using a Lumex. Results obtained using these different methods were comparable and produced consistent results. The greatest variation in results obtained was related to the time of day of sampling, which highlights the importance of temperature differences during sampling.

Ongoing projects and studies on Hg within the BRGM include: • Diffusive gradient thin film testing (DGt) – thiol-DGT is specific for Hg analysis • Use of mercury isotopes: to improve understanding of Hg transformation at polluted sites • Study of the composition of microbial communities as an indirect indicator of (de)methylation

potential Presentation Nr. 3 A Geochemical Framework for Mercury Contamination at Former Chlor-Alkali Plants Dick Brown, ERM

Dick Brown opened his presentation by differentiating between metal and organic Hg. When dealing with metal Hg, mineralization sometimes takes place, leading to incorporation of Hg in the soil matrix. This is a challenging situation to address, more difficult than a situation when organic Hg is on hand (such as in environments where methylation or methyl-Hg is a concern).

Identification of the geochemical conditions at a site, in relation to Hg; and the resultant Hg-speciation is key. Remedial objectives for Hg cell plants should:

• Aim to create a non-mobile, geochemically stable Hg form; and • Address Hg exposure issues arising from Hg vapours, dissolved Hg, and methyl Hg.

A summary of a mercury cell production process was given, as background information for the audience. This illustrated that sources arising from mercury cell (i.e. Hg-alkali) sites are:

• Liquid Hg • Hg vapors – blow around and deposits giving larger footprint • Waste containing Hg, especially from brine purification • Hg methylation

Active Hg reactions reviewed were those for redox reactions and for methylation-demethylation. Factors affecting Hg speciation were noted to include:

• Redox* • pH* • Precipitation • Complexation • Microbiology * See Pourbaix diagrams. Also, alkalinity also has effect on dissolved organic matter which can be transported by groundwater. The mercury is adsorbed to the organic matter and leads to facilitated transport of mercury.

Speciation on the basis of the redox and pH conditions has further effects, as the solubility of the various Hg-compounds can vary strongly.


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Hg methylation was also summarized. Methylation depends strongly on bacterial (biological) activity. Methylation and methyl-Hg formation can be challenging and in this regard unpredictable.

To mitigate Hg impact, it is key to determine the Hg biogeochemistry – and speciation, therein also identifying the (pre)dominant and most stable form of Hg at the site. In addition, determine the ambient geochemistry as over time this will theoretically dominate the system due to buffering. Remediation techniques should be directed at transformation of Hg to an appropriate / acceptable form.

Examples were subsequently given in which chemical speciation was assessed on the basis of sequential extraction. The test cases presented pertained to climatically different sites with different dominant Hg-species identified, different geochemical conditions and different remediation solutions.

Questions from the audience concerned methylation. Methylation was discussed to take place slowly but steadily and to be key in marine environments*. In soil / land-based systems, other factors probably play a larger role. The speaker was requested to comment on this. An observation was also raised on marine environment depositions of Hg. Discussion also took place on the roles of chloride and sulphide – and the fact that these are important factors controlling action; and on the importance of organic matter if available such as humic acid**, e.g. for wetlands.

* Note from meeting reporter: methylation and demethylation are key to aquatic and sediment environments in general, not just marine. The dialogue was probably intended to discuss aquatic environments in general.

** Note from meeting reporter: probably primarily key for organic Hg

Presentation Nr. 4 Mercury Prills under a Former Chlor-alkali Plant: significance, distribution, migration and remediation Bacci Eros, University of Sienna; Roberto Pecoraro, Versalis S.p.A; Fabrizio Salatti and Alessandro Battaglia, AECOM Italy

The speaker, Dr. Bacci Eros, opened with a brief overview of regulatory drivers in Italy which have been in place since the 1970s for the reduction of mercury (Hg) escape to the environment and the counteracting of historic spills to the environment (a principle of ‘perdite sconosciute’, i.e. lost unknowns, are negative must be accounted for). A case study was subsequently introduced, concerning a former chlor-alkali plants for which decommissioning commenced in 1991.

The plant operated from 1957 – 1991, and the remaining building structure has a floor surface area of 5,000 m2. The depth to the saturated zone is 8 meters from surface. There is an estimated 40,000m3 of vadose zone. The position of the public officials was that some 580 tons of Hg0 have been lost to the environment / soils.

Angular drilling was used to reach and assess the unsaturated (vadose) zone. Limited extent observations were made of Hg droplets. The underlying groundwater zone was also identified and no Hg was identified in groundwater on the basis of the investigation activities.

An assessment was also done of the building floors, entailing desk work (structure, type and condition of floor) and field sampling. Hg was identified to have permeated cracked floors, although in different form than Hg identified on/ within the surface layer of uncracked floors. This and further field assessment was used to identify three high concentration (‘hot spot’) areas of Hg impact. The entire floor was subsequently removed, high concentration areas remediated (excavated) and a soil vapour ventilation/ extraction system applied to address residual Hg vapours in the vadose zone. Limited groundwater abstraction and air stripping was also put in place for low concentrations identified of Hg in groundwater however overall the team’s conclusion was that metallic Hg did not migrate into the aquifer, primarily due to Hg’s high surface tension of 415 mN/M, which severely restricted the ability of


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the Hg-spills to infiltrate and migrate. No methylation or irreversible oxidation was concluded to have taken place.

The presentation further explored means of possible Hg spreading, through solution in water, diffusion, advection with water etc and touched upon the occurrence of Hg in other nearby environments (surface water bodies). Overall, a conclusion was drawn that metallic Hg’s reaching groundwater signified containment and a stop to further vertical Hg spreading.

Questions from the audience concerned:

• Methylation processes, particularly as these arise in surface (water) systems, and the extent to which methyl-Hg can be measured in local fish.

• A comment that metallic Hg does flow in groundwater. In a case cited by the audience, and later presented at the workshop – see presentation nr 6 --, metallic grade Hg was identified 5.5 meters below surface. Small droplets were observed at the site however Hg was also identified in groundwater. Overall the findings arising out of the specific case study in the presentation, particularly concerning the inability or difficulty for metallic Hg to travel or give rise to significant Hg-contamination in groundwater, were noted not to pertain universally.

• Has an estimate been made of the time needed to reach local remedial objectives through the soil vapour venting at the high concentration source areas (hot spots). The response from the speaker was that this estimate was not made.

• How was the system protected above ground / ex-situ. The response was that (ground)water was first removed, and following this Hg in soil vapours was addressed. Activated carbon was used to filter the air/vapour. The remediation system was first used in the northern building section, and then the southern.

• Range of Hg-concentrations in groundwater near the former cell-production areas, and on the type of plume that arose of this. The response was that a plume with a migration length of approximately 25 meters arose. The rate of flow was inferred to be 0.5 to 1m / year.

• The type of soil / sand encountered (this was a sandy coarse and fine-grained soil).

Presentation Nr. 5 NEBA for the evaluation of remedial alternatives of mercury contaminated site Eliza Bizzotto, Fabio Colombo, Aldo Trezzi, ENVIRON Italy

‘A sustainable remediation project is one that represents the best solution when considering environmental, social and economic factors’

– NICOLE SR working group -

The presentation opened with the above quote from the NICOLE sustainable remediation working group. Remedial actions can significantly influence not only the (target) polluted matrices, such as soil and groundwater; but also the surroundings – the other natural resources and services offered by the surrounding landscape and ecosystems.

There are several tools or type of tools that can be used to assess effect and/or sustainability of an action, ranging from framework tools, traditional means of quantifying impact (investigation, modelling, risk assessment) and tools for the decision-making process. NEBA (net environmental benefit analysis; also known as a Net Ecosystem Service Analysis (Nicolette et al, 2011)) falls into the last category and offers a useful approach for management /decision-makers to compare options.

NEBA comprises a formal quantification of the change in assets provided by the environment to people (as “ecosystem services”), when considering the implementation of different remedial scenarios and


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the (resultant) changes to expenditure and predicted risks. Ecosystem services can be quantified and can be defined as services that contribute to economic welfare (contributions to the generation of income and wellbeing) and to the prevention of damages that impose costs on society. Examples were given in the presentation, and an overview was given of the many areas contributing to ecosystem services assessment and identification. Applying NEBA can lead to lower total expenditure remediation in the longer term, however application of NEBA does require detailed assessment (i.e. shorter term expenditure).

NEBA is best used at sites where: • The contaminated site may have a potentially significant ecological value or may be

surrounded by areas of naturalistic interest • The proposed remedial actions themselves can be environmentally damaging • The benefit of the remediation appears to be disproportionate to the costs of the remediation • Remediation actions appear to provide a marginal benefit or no net increase in ecosystem

service value for the effort expended (e.g. marginal contamination) With regard to Hg-contaminated sites, NEBA would necessarily rely on a considerable amount of site-specific information. Crucial steps in a NEBA lie in the planning phase, when selection of metrics (using monetary and non-monetary parameters) occurs for the quantification of changes of ecosystems services for each remedial alternative. The selected metrics are used to define conceptual site models, identify data gaps and uncertainty sources, and develop well-founded understanding on causality of processes. In many cases, uncertainty in risk assessment is handled through the use of conservative assumptions which may predict a risk when, in fact, no injury is occurring

A case study was presented for Augusta Bay, in Italy (Sicily). The bay and its sediments had been identified to be contaminated with Hg and with other compounds. In 2008, a large scale dredging project was proposed and developed on behalf of the Ministry of the Environment, wherein no consideration had been given to the effects of the projected dredging to ecology or other aspects. Globally, concerns had nonetheless arisen concerning bigger picture effects of intensive dredging. A need was identified for a conceptual site model as a framework to understand the bay. Data gaps were identified concerning methyl-Hg, sediment & chemical stability (which were poorly understood), ecological conditions, risks and risk analyses relevant to the system, hydrodynamic and sediment transport information, and temporal effects. The figure below summarizes processes and aspects that were included in the conceptual site model. The figure has been reproduced not only to present an example of a conceptual site model used for NEBA, but to also illustrate, once again, the significance of placing Hg in context in a cycle and in site-specific conditions supporting an assessment of speciation and the bio-geo-chemical assessment of site setting. Also, as a detail, it is noted that the bio-accumulation and toxicity effects of methyl-Hg to human-beings is under review. At present, it is primarily known that methyl-Hg bio-accumulated in the aquatic environment can pose problems for terrestrial species largely feeding on fish/ shellfish.


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Figure: Sample of a Conceptual Site Model for the Bay

Following completion of the conceptual site motel and the NEBA for the Augusta Bay case, it was concluded that large-scale dredging was unwarranted as a remedy for Hg, and inappropriate.

Another case was presented for the Lake Maggiore Watershed, an extensive watershed area for which it had been identified that historic industrial activity in the watershed, including former chlor-alkali plants, had likely led to the identified Hg and DDT in sediment and fish in the watershed. As a result, fishing was banned in 1996 in the watershed area / rivers. In 2007, the Italian Environmental Ministry requested an evaluation of a dredging/capping option for all of Pallanza Bay (approx. 20 km2, with a water depth of up to 150m) into which the rivers in the watershed flow. The net ecosystems assessment included extensive field work, i.e. extensive studies of sediment (chemical characterization, profile imaging; transport and transport modelling); bathymetric and topographic surveys; toxicity testing; fish and benthos sampling; ecological risk assessment; baseline characterization. The assessment was then used to identify and assess three sets of remedial scenarios, ranging from monitored natural recovery (MNR) to capping and dredging. A scenario of MNR combined with Riparian Rights enhancement was concluded to be appropriate and provide the least damage and most net eco-system benefit. Graphs were further presented to demonstrate results of the studies and the conclusions that can be visualized. The NEBA for Lake Maggiore was summarized to have been used as a basis for discussion with and among regulatory bodies and public; and to have been a positive contribution to the dialogue and decision-making processes on the area. The NEBA approach proved to be a defensible basis of support for environmental management under sustainability principles, integration of environmental, social and economic aspects and communication among stakeholders.

Questions and comments from the audience concerned the following:

• A factor which was not addressed / highlighted in the overall NEBA (or in the presentation) concerns the fate of dredged materials -- what would have been done with the dredged materials. The speaker acknowledged this and explained that traffic and land use required that a large


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volume of sediments (dredged materials) had been incorporated in the actual NEBA. Stakeholder input / value was taken on board and proved useful for this consideration.

• Quantification of health benefits or ecological health benefits for the removal of Hg: was it possible to quantify these. The speaker replied that the identified risk was low as the contamination actually lay at depth (quite deep in the sediment profile).


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4. Modelling, Risk Assessment and Remediation Session Chair: Laurent Bakker, TAUW, the Netherlands

This session focused on the modeling, risk assessment and remediation of Hg at industrial properties.

Presentation Nr. 6 Modelling the DNAPL spreading behavior of pure phase elemental mercury in soil and groundwater systems for risk-assessment and remediation approaches Annemieke Marsman, Niels Hartog, Thomas Keijzer and Thomas Sweijen, of Deltares, the Netherlands

An introduction was given on dense non-aqueous phase liquid (DNAPL) and pure phase Hg. The presentation is aimed at the presentation of the team’s efforts to research and describe pure phase (metallic) Hg behaviour in soil and groundwater.

As a means of background, • Various (former) industrial processes including chlor-alkali plants have contributed to Hg-

impact to soil and/or groundwater. The number of plants using Hg in manufacturing processes has however significantly decreased in recent years. Hg identified at these sites is often present as pure phase elemental mercury (Hg0), and may be encountered at considerable depths in soil and groundwater. Hg-behavior as a DNAPL supports efficient removal and facilitates assessment of risk for groundwater quality.

• Hg-behaviour has not as yet been fully characterized or described. According to the speaker, there is relatively little to no research on transport of metallic-Hg. One study was identified by the team dating to 1988 – Migration of elemental Hg through soil from simulated burial sites. More recently another study has been completed, by Devasena & Nambi (2010).

The Deltares project team has been focusing on characterization of Hg-behaviour in the saturated zone. The team used the Subsurface Transport over Multiple Phases (STOMP) modelling program; and developed a model to allow for Hg and PCE comparison. A two-phase flow in a saturated system was chosen. The parameters used were chosen to be similar to and offer a basis of comparison with Devasena & Nambi’s earlier study. These concerned density, viscosity and interfacial tension with water, in dyne/cm; for water, PCE and Hg.

Key research questions were/are: • What are the main controls (wettability, viscosity, heterogeneity, spill mass) on the risk of

subsurface spreading of Hg DNAPL? • What controls the depth to which Hg infiltrates? • Will there be residual phase of elemental Hg left in the zone passed by the pure phase

product? • What is the extent of lateral spreading?

Modelling simulations results suggest very quick Hg infiltration in a moderately fine-grained sand – of 1.5m3 traveling 3000 cm in 50 hours for Hg. The comparable simulation for PCE suggested 1000 cm in 50 hours.


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Figure: Results for PCE and Hg in medium fine sand

The team also modelled a 10-hour travel time but varied the viscosity and density in Hg by substituting those assigned to PCE. The results showed a slight effect on Hg-infiltration when viscosity was changed, but simulated significantly reduced infiltration when modelling Hg travel using PCE-specific density.

Varying the soil profile into a fining upward sand, different behaviour was exhibited for Hg-infiltration when compared with PCE-infiltration. PCE infiltration slowed down upon a grain-size change from fine to medium, while Hg infiltration continues at depth across grain-size changes.

Similarly, the introduction of ‘loam’ (= silt/clay) lenses identified delayed and slightly altered but continued infiltration by Hg.

Field testing was done to assess patterns and the chance of residual phase Hg after pure phase Hg has infiltrated or passed by/through a soil medium. The field testing involved the advancement of a CPT-cone equipped with a camera. Low level of residual phase was identified for Hg in soil. See the questions section further below concerning the possibility that the CPT cone may have pushed a drop of Hg down the hole.

Modelling results identified to date: • There is much faster vertical flow for Hg DNAPL than for PCE DNAPL • There is lesser horizontal spreading of Hg when compared with PCE DNAPL • There is less residual phase Hg when compared with other contaminants such as creosote. • The high density of Hg has the largest influence on vertical distribution • More study and laboratory work is needed of specific Hg parameters • The significance of the on-going research for remediation is: relatively small plumes of Hg

contamination develop, at large depth, with almost no residual DNAPL between a spill source or DNAPL area and the plume. It is important to develop insight on the location at depth of the Hg DNAPL


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Questions from the audience and discussion concerned the following: • Possible effects of the CPT cone having dragged Hg down into the soil profile. How did the team

control for this? The possibility that the CPT cone dragged down a drop / drops of Hg cannot be entirely ruled out, however the CPT was noted to have been equipped with a camera

• Effects of possibly modelling the same weight of PCE vs Hg, instead of volume (as Hg mass is approximately 8 times that of PCE, i.e. modelling volume signifies modelling the equivalent of 8 times more Hg mass than PCE)

• Role of the saturation zone for infiltration of Hg (through unsaturated areas). • Was interfacial tension reviewed particularly with regard to effects of / on Hg penetration through

the unsaturated zone? The response was that the point was important and that the research team had not yet reached the point of translating results from field to model.

• Effect of wetted surface for soils – wetting affects polarity. If soil or the medium through which Hg must travel is dry, the Hg turns its hydrophobic side to the outside.

• Is it possible to examine ‘immunity’ (i.e. resistance to reaction or effect) between organic fluids and Hg fluid? Are these analogous?

Presentation Nr. 7 In-situ remediation of Hg-Zn contaminated soil and groundwater by using immobilisation technology implemented by in-situ grouting: 2 case studies Pierre Yves Klein and J.D. Vilomet, Sol environment, France

The presentation addressed two case studies in France of remediation programmes for Hg contaminated sites.

Case Study 1: in eastern France – a former battery production site for which an immobilisation slurry for Hg and Zn was designed, applied through in-situ treatment by impregnation using grouting technology.

The case concerned a former production plant for electric batteries. The plant operated 1960 – 2005 and made use of zinc-carbon technology. The property has a surface are of 6.2 hectares (ha) and is located alongside a creek. The site building has a footprint of 0.6ha. The property is to be redeveloped for new social and economic activities.

The soil profile consisted of 35 metres of fluvio-glacial aluvium on a granitic substrate. The groundwater table was encountered at 3 meters below ground level (m bgl). The creek was inferred to serve as a drain for the aquifer.

Hg and organic pollutants had been identified at the site. The highest identified concentration of Hg in soil was 260 mg/kg and for zinc 190 g/kg. Groundwater had become impacted by TPH (5.6 mg/l) and Zn.

The remediation strategies chosen were to treat TPH in groundwater through in situ bio-remediation; and to treat Hg, Zn, Cu in soil through immobilisation, in an effort to protect (spreading to) the aquifer resource.

Soil samples were collected for laboratory testing involving the development of a slurry suitable to bind and immobilize the Hg. Testing of the slurry was done for rheology and for hardening (the slurry must harden in-situ within a required amount of time). Following this, leaching tests were done for metals, including Hg, Cu and Zn concentrations, and evolution was also tracked in addition to Hg because Cu and Zn are key parameters when working with binders.


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Once the slurry had been developed, the slurry was introduced to the project site through the drilling of 158 boreholes and sealing of 1840 grouting wells. Grouting was also driven sleeve by sleeve from depth upwards using inflatable straddle packers. The system was subsequently tested and monitored through sampling and analysis / leach-testing of treated site soils. Groundwater quality monitoring was expanded to include Hg. No significant concentrations were identified in groundwater for Hg. Zinc was also monitored and was shown to decrease in concentration within one year.

Case Study 2: a laboratory study on soil from a former chlor-alkali plant, to develop a means of chemical immobilisation targeted at effects from the treatment (through the introduction of binders) for Hg transfer to gaseous phase (i.e. air/vapour).

Mercury (Hg) contamination had been identified in soil and groundwater. As a result there was identified risk to human health, from risk of Hg transfer to groundwater and to soil vapour and air.

The remediation strategy was aimed at chemical immobilization. Laboratory testing was done on two samples, and subjected to 24-hours of leaching (L/S = 10).

Various formulations consisting of cements and additives were developed and tested on further soil samples, and the treated samples were subsequently leach-tested and compression tested. Releases to air / vapour were also tested, by isolating selected samples in a bag, running air by the samples using a pump, and passing the collected air through an activated carbon filter. Concentrations were observed to significantly reduce in time, e.g. over a period of 120 days.

Conclusions drawn were that chemical immobilization of Hg contaminated soils can lead to reduction of leaching to water; and to a reduction in vapour transfer. In situ treatment by impregnation grouting is effective to treat porous soils that are not easily accessible.

Questions from the audience concerned the stability of the binders (these were explained to last a long time); testing of the permeability of the soils; and on the environmental settings of the Hg – for the first case there were Hg-Zn amalgamations and it appears unusual that Hg should not have been identified in groundwater; and concerning the second case there was discussion on the need for speciation of Hg. There was also a discussion on the chance that Hg droplets in the field may have been displaced during introduction of the remediation system; and on the chance that metallic Hg may have evaporated during laboratory testing off of treated samples for subsequent capture on to the plastic bags used during vapour testing. Further discussion ensued on the details of the air / vapour testing, rates of flow etc. Questions also arose on the costs of treatment, i.e. grouting technology. The reply was that expenditure is not unusually high, comparable with other standard treatment techniques.

Presentation Nr. 8 Mercury Site Remediation Frank KARG, HPC Envirotec S.A., France

The presentation opened with an overview of the Hg challenge, including a summary of environmental and toxicological issues, extent of Hg distribution in the environment, and listing of industrial sources of Hg contamination. An overview was also given of known cases of site contamination by Hg, e.g. cases in Germany where contamination with has arisen from former production of wood conservation products, through the use of HgCl2 and PAH tar oils; former chlor-alkali sites; etc wherein soil and groundwater, and also buildings and demolition debris / fill matter in soils and infrastructural works may have become impacted. Remediation technologies entailing complete excavation, re-landfilling/disposal etc are available however these options can be costly.

The speaker Frank Karg noted as an aside that there is draft guidance published by Euro Chlor on decommissioning of mercury chlor-alkali plants. The final version of the guidance is expected in 2013.


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A review was given of the chemistry and of the speciation of Hg with S and Cl, including a review of the Pourbaix diagram (as also presented in earlier presentations for the NICOLE technical workshop); and of bio-transformation and bio-accumulation reactions for methyl-Hg.

Consideration of Hg-reactions is of fundamental importance.

Remediation methodology should be based on: • A complete historical survey to understand potential for Hg distribution and bio-available hot

spots and plumes; • An environmental study to characterize geological, hydrogeological, geochemical and risk-

target aspects; • Site investigation results; • Site specific risk assessment • Site specific remediation targets • A technical and economic feasibility study • Identification of a potential need for monitoring • Site remediation options

There are ‘traditional’ engineering solutions for remediation (e.g. dig and dump) and there are newer style/currently well-developed in situ options (reactive barriers etc). Hg remediation options require Hg-specific solutions.

Case study – in Marktredwitz/ Germany: use was made of specific a mix using TM15- trimercapto-s-triazine™, which can be purchased from Degussa Chemical Industries. The substances make use of the principle of sulphur binding of Hg. The binding process has been found by HPC to be nearly irreversible. There are several other applications for TM15-trimercapto-s-triazine™ -- generally, the speaker has found that 1 kg of pure Hg can be fixed by 5 to 6 litres of TM15.

Application is possible as a spray or through infiltration. Verification of efficiency is achieved through leaching tests of treated soil samples from the project. More than 1830 tons of Hg-contaminated soil have been treated in HPC’s experience. The treatment time is short -- 10 to 12 minutes. Per 7.5 t of contaminated materials, approximately 160 l of TM15 solution has been needed in test batches.

Case study – confidential site in Normandy, France: in-situ stabilization of Hg was accomplished through the use of specific micro- or nano-metric phosphates and sulphides. The preferred micro- or nano-particles were iron-sulphide and iron-phosphate particles and specific stabilizers, which were cheaply procured from the agriculture industry for animal feeding. Production of the iron-sulphide and stabilizers was possible on site. The technology is currently undergoing patent review. The specific


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process and remediation option for the site in Normandy was based on the option to stabilize Hg through FeS-binding.

In situ treatment was realized through percolation of iron sulfide solutions. This was also used on contaminated sludge and river, lake and sea sediments. The technology relied on ion exchange, where Fe is replaced by Hg or where Hg2+ is converted to Hg0 and then sorbed on to Fe sulfide.

The reaction however relies on bacterial activity – sulphate reducing bacteria (SRB). The SRB are however the same bacteria that can lead to methylation of Hg. Stable Hg-formation is

desirable and methyl-Hg formation is not. The remediation option was therefore developed to optimize production of stable Hg. Prior to or in conjunction with application of the FeS remediation technology, ‘hot spots’ of Hg-contamination were also excavated and disposed off-site.

A third case study concerned contaminated groundwater in Germany. The project was completed in collaboration with an University. Treatment was realized through passive treatment on specific zinc-copper (Zn-Cu) alloy granulates. The alloy granulates were used for treatment (alloy-adsorption filter) of groundwater. Hg replaces Zn during filtration. The team accomplished reduction of Hg (HgCl2 had formerly been used as wood impregnation), from 60 µg/l to 0.01µg/l. Other alternative alloys are also possible, as needed.

Conclusions drawn were: • The effect of irreversible Hg binding and stabilization via element exchange between Hg and

Zn, etc. and in-situ stabilization via TM15® or n/µ-FeSn and specific alloys offers an option for treatment of Hg contaminated site in a cost efficient manner. In-situ-application of a Permeable Reactive Barrier (PRB) is currently on-going.

• Successful application of these techniques is possible if these are founded on useful site investigations (contaminant characterization) and risk assessment

• Treatment improvement and optimization is ensured through field testing and pilot projects Questions from the audience and discussion concerned the toxicity and stability of the TM15 molecule; challenges which arise when Hg is not in ionic form – how would one handle dissolved Hg which is not in ionic form; organic binding; and the preparation of alloys. Zero-valent metallic Hg is even more easily adsorbed and fixed by the specific alloy-adsorption filter.

Presentation Nr. 9 Remediation of a Former Chlor-Alkali site in the Netherlands Stany Pensaert, DEC

The presentation focussed on a case study in the Netherlands but also provided brief overviews of other examples of Hg contamination and remediation.

The presentation opened with a site in the Netherlands, remediated in 2011 (a former AkzoNobel site located in Hengelo). The property has in the past been used for salt abstraction, since the 1930s. Chlor-alkali production also took place at the site, and was terminated in 2006. The former chlor-alkali processes produced chlorine, hypochlorite, sodium hydroxide and hydrogen amongst other substances.


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In addition, the industrial site has formerly been used for the production of chlorine derivatives such as lindane. A section of the site continues to be used for salt abstraction.

A review of the chlor-alkali electrolysis production process using a Hg-cathode was given. Spills of cathode but also of NaOH, to which Hg can be attached, have occurred at the subject site. A review of the EU directives and Eurochlor guidance was also given.

The subject site is located along a major canal. An identified groundwater plume of contamination appeared to be flowing towards the surface water. An estimated 40,000 m3 of contaminated soil was in place, with a highest identified Hg-concentration of 1,200 mg/kg (average of 12 mg/kg). Hg in groundwater, which was encountered at a depth of less than 15 m bgl, averaged 10 µg/l.

Key criteria (clean-up standards) used at the site during remediation were 7 mg/kg Hg in soil as a target level for industrial sites; the soil intervention value of I25 mg/kg; the groundwater intervention value of 0.3 µg/l; and 5 µg/l as the target for the adjacent canal.

The remediation approach selected was based on the following: • The client AkzoNobel has a policy of recycling / re-using materials to the extent possible, under a

cradle to cradle (C2C) principle; • Preliminary laboratory scale studies had been carried out by several previous parties concerning:

soil washing, thermal desorption; electro-reclamation; and stabilisation/solidification (immobilisation)

• Soil washing was identified as a best potentially cost-efficient option Field investigation including the digging of trenches was carried out to further characterize contaminant distribution. Laboratory scale testing of soil washing was also done, with differentiation among gravels, sands and fines.

The remediation design was based on the following test findings: • There was limited volume of gravel in the soil; • Wet separation of sand reduces Hg concentration by 50 to 75 %; • Further Hg reduction by scrubbing of sand was realized, up to 90 %

Hg in floor cracks was identified to be difficult to reach.

Design also relied on the company’s (DEME’s) prior experience at other sites both with Hg contamination as well as building of mobile soil washing units. Prior recent experience with Hg-contaminated sites entailing soil washing included excavation of soil contaminated with Hg at an industrial property in Antwerp, and an industrial property in Bengtfors, Sweden.

The Hengelo (case study) excavation concerned 60,000 tons of soil (to groundwater level). A geotextile and clay liner were introduced to support the remediation. The excavation hole was backfilled with certified uncontaminated (‘clean’) soil. Excavation groundwater that arose during remedial works required treatment, through sulphide precipitation.


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Excavation was accomplished in phases. Excavation entailed clearance, avoidance and/or removal of underground utilities; debris sorting; and gravel screening; prior to passing sorted soils through the on-site mobile soil washing unit.

The clean-up target for soil of 7 mg/kg proved difficult to achieve, and criteria were (re-)set to a range of 7 to 150 mg/kg. A total of 100,000 tons of soils were excavated: a) 10,000 tons were washed to < 20 mg/kg; b) 3,000 tons were washed to < 7 mg/kg; and c) the remainder was landfilled

Groundwater treatment: groundwater arising from the project had a relatively high pH, and contained both dissolved and non-dissolved Hg. The water was treated through sand removal, aeration and flocculation and coagulation / flocculation with HCl and FeCl3 and sulphide; decanting; sand filtration; and granular activated carbon.

A note was made on occupational health and safety in the field. Hg droplets were encountered in the field, and these were removed through vacuuming. To control

spreading of particulate Hg, soil was moistened and stockpiles were covered. Hg vapour monitoring occurred in the field with the use of mobile equipment and fixed monitoring points. Personal protection included the use of protection for dust (e.g. P3 dust filters and protective clothing / suits); and the use of Hg filters during excavation of hot-spots. Bio-monitoring of all workers on site was also done.

Lessons learned:

• Site investigation of chlor-alkli sites is not straightforward. Nugget effects of Hg arise, XRF equipment offers good testing means, and groundwater sampling and analysis must be subject to destruction (i.e. the groundwater sample is ‘preserved’ for metals with the use of an acid which serves to also dissolve metals which may be included through

particulate matter) to avoid obtaining false negatives. In addition, other parameters relating to the former chlor-alkali production were encountered but not necessarily expected, initially. A protocol should be elaborated.

• Metallic soil washing technology can cope with removal of metallic Hg from soils with removal efficiencies between 70 and 80 %.

• The remaining Hg concentrations in the sand mainly consist of non-mobile compounds. Further speciation studies are on-going.


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A final case study was also shown, taken from a property in Lokeren, Belgium. A former industrial site known for its superior treatment of rabbit furs was identified with Hg contamination. The project received significant attention, as Hg was also identified to be relatively widespread through the surroundings. The source of Hg at the property lay in a company trade secret – which entailed the treatment of rabbit / hare furs with Hg nitrate. The Hg contaminated soil totalled 13,000 tons of soil that was excavated for soil recycling / washing. Of this, 8,000 tons of soil were ultimately land-filled; 3,000 tons of soil were immobilized and then landfilled. Immobilization was accomplished through the reduction o Hg leaching from 2 – 4 mg/kg to below 0.3 mg/kg DM. Groundwater treatment was based on micro-filtration.

Questions from the audience concerned the presence of ionic Hg at the case study (Hengelo) and on the oxidants tested; on Hg encountered in groundwater and the manner in which this was handled – and on the likelihood that organic Hg was also in place, it is thought in solution, and it is thought that this then precipitated once destruction (with acid) of the groundwater samples / streams to be treated was completed. There was also discussion on alternatives that may have been applied, e.g. thermal treatment. There was also discussion of clean-up levels. Some discussion is on-going among public bodies on re-evaluation of allowable levels (internationally), however this will continue – for future resolution.


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5. Discussion and Concluding Remarks

5.1 Discussion

The workshop presentations created a diverse pallet of topics pertaining to Hg-contaminated sites. Presentations were given on practicalities of field investigation, and on the mercury-specific aspects which make investigation challenging; and on field remediation of Hg-contaminated soils and groundwater. Presentations were also given on research into mercury behaviour, fate and transport in soil and groundwater. Research was based on the use of field and laboratory testing, pilot testing, and modelling to simulate and study mercury spreading in the saturated zone. A common theme throughout the project presentations was the importance of understanding the conceptual model for Hg – including characterization of the form of Hg present as well as the site conditions and speciation / predominant Hg-reactions at the site.

Remediation techniques presented and discussed include ‘known’ techniques from other types of remediation projects, such as soil washing, pump and treat, soil vapour extraction (SVE), dig and dump; as well as technologies aimed at the fixation or immobilization of mercury in situ rather than the removal of mercury from soils and groundwater.

• The fixation / immobilization techniques make use of especially formulated grouts and/or chemical compounds which are available on the market specifically for remediation. These techniques do not address the removal of Hg (i.e. no clean-up concentrations involved) and instead address the potential migration and exposure routes for Hg releases to the environment and/or human health. The techniques are aimed at physico-chemical fixation and immobilization of Hg in-situ.

• The more ‘traditional’ or wider spread techniques of pump and treat, SVE, soil washing etc involve the remediation of Hg-contamination until a target or clean-up level , usually risk-based, is reached. The clean-up targets are not always attainable. For example a soil washing project that was presented entailed a target clean-up value of 7 mg/kg. With a removal efficiency of 70% to 80%, the target of 7 mg/kg was not reached. The residual mercury was assessed to be a non-mobile form, giving rise to a recommendation for monitoring of the residual risk.

The workshop discussions did not address additional or alternative methods which may have been subsequently applied in addition to the above, however the theme of residual Hg contamination is common to all or most of the remediation scenarios discussed. Monitoring of residual contamination, albeit residual Hg in non-mobile form, was commonly proposed as a means of managing this residual risk. The situation of having residual Hg is expected to continue in future. It appears therefore that a means or systematic approach is needed for: a) assessing residual risk arising from residual Hg; b) criteria for evaluating the need for monitoring of residual Hg-risk; and c) management of Hg-monitoring programmes. A well-developed systematic methodology may prove useful in the future to also ensure a consistent approach.

The workshop included discussion of alternative sustainable approaches to remediation. Remedial actions can significantly influence not only the (target) polluted matrices, such as soil and groundwater; but also the surroundings – the other natural resources and services offered by surrounding landscape and ecosystems. There are several tools or type of tools that can be used to assess the effect and/or sustainability of an action, ranging from framework tools and traditional means of quantifying impact (investigation, modelling, risk assessment) to ‘tools’ for strategic decision-making. A presentation was given on net environmental benefit analysis (NEBA), also known as Net Ecosystem Service Analysis (Nicolette et al, 2011). NEBA entails a comprehensive characterization of contaminants (in this case Hg) in the environment in a manner that offers (policy / strategic) decision-makers a tool to compare remediation options.


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Environment and ecology can be viewed to offer ‘services’ to human-beings. NEBA comprises a formal quantification of the change in ‘assets’ or value provided by the environment to people (i.e. “ecosystem services”). Ecosystem services can be quantified and can be defined as services that contribute to economic welfare (contributions to the generation of income and well-being) and to the prevention of damages that impose costs on society. To complete a NEBA, comprehensive studies are needed to properly characterize a system. Following this, the NEBA is done for various remediation scenarios, to arrive at an identification of a net optimized benefit to human beings and ecology. This may entail the leaving in place of Hg in contaminated strata in favour of the benefit to ecology that would otherwise be damaged by remediation techniques, particularly if emission / spreading of Hg in the setting at hand does not present an actual risk. NEBA should not however be used to avoid taking remediation options. NEBA is best used at sites where a contaminated site may have a potentially significant ecological value or may be surrounded by areas of natural interest; proposed remedial actions themselves can be environmentally damaging; the benefit of the remediation appears to be disproportionate to expenditure and cost of remediation; remediation actions appear to provide marginal benefit or no net increase in ecosystem service value for the effort expended (e.g. marginal contamination).

A theme common to all the discussions on remediation is the situation that Hg may remain in place following remediation or evaluation of net environmental benefit; particularly if the Hg is essentially immobile or immobilized. However, a consistent means of monitoring and managing for this type of residual Hg and/or residual risk would be prudent.

5.2 Conclusions

Key conclusions arising from the presentations concern the importance of the following:

Characterization

• Properly characterizing Hg distribution and occurrence at an industrial site, on the basis of historic land use review and empiric / intrusive site investigations;

• Understanding the environmental systems, site setting / conditions and bio-geo-chemistry;

• Understanding Hg speciation and the major speciation processes occurring at a particular property (not only for Hg but also for other ions);

• Tracking temperature and weather conditions, and maintaining consistent timing in field sampling of sites contaminated with metallic Hg. Temperature acutely affects the gaseous phase in which Hg may be encountered and therefore significantly affects investigation results;

• Proper characterization of the situation to support development of remediation strategies. Remediation strategies will often be developed around the pre-dominant Hg-reactions and speciation processes, making use of reactions needed to immobilize or convert Hg into a more manageable form.

Remedial Solutions

• There are traditional remediation techniques used in Hg-remediation, with good success for Hg removal. These techniques may, as with other remediation approaches, result in some residual Hg-contamination which is subsequently monitored as a means of ‘after-care’, particularly for residual risk;


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• There is newly developed remediation technology on the market for the immobilization of Hg, through the introduction in-situ of the immobilization substances (grout mixes, or specialized products designed for Hg immobilization). These have proved to work nicely for the immobilization, however the techniques entail the introduction and addition of substances to the soil and the Hg remains in place albeit in immobilized form;

• Not all remediation situations warrant a direct technical resolution directed at the immediate removal of Hg (e.g. excavation, treatment, capping/dredging in the event of sediment, etc). Management options or alternative approaches directed at eco-system conservation (such as NEBA) may be considered. These approaches can be used to factor in other social, ecological and environmental concerns to provide for a whole-system analysis of the costs and benefits of remedial solutions under review.

• Good characterization of the Hg-system and reactions at a particular site or setting is useful in support of the remediation approach to be chosen, but also for the monitoring of residual Hg that may be needed. A means or systematic approach for assessing residual risk arising from residual Hg and for management of Hg-monitoring programmes is needed. A well-developed systematic methodology may prove useful in the future to also ensure a consistent approach.

Guidances and regulations continue to be developed for Hg. In addition, it is noted that there is an international Conference on Mercury as a global Pollutant scheduled for 29 July - 2 August, 2013 in Scotland (www.mercury2013.com) and that the UNEP has targeted 2013 as a year in which to reach legally binding agreements internationally to address the mercury issue.

http://www.mercury2013.com/�


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Appendix 1. List of participants NICOLE Technical Meeting, 4 December, 2012, Brussels, Belgium

Van Achter, Hervé Tauw België NV Belgium Ambrosini, Paolo Saipem S.p.A. Italy Arentshorst, Paul AgentschapNL NL Bacci, Eros University of Siena Italy Bakker, Laurent Tauw BV NL Bangels, Stefan RSK Belgium Battaglia, Alessandro ERM France Bauraind, Laurent Antea France van den Belt, Rick Witteveen+Bos NL Bianchini, Andrea AECOM Italy Biegansky, Frank URS Germany Biester, Harald TU Braunschweig Germany Birnstingl, Jeremy Regenesis UK Bizzotto, Elisa ENVIRON Italy Blom, Marianne ENVIRON NL Bondgaard, Morten Region Midtjylland Denmark Brown, Dick ERM USA Buvé, Lucia UMICORE Belgium De Buysscher, Geert ENVIRON Belgium Cazaux, David Solvay Electrolyse France Cole, Jason CH2M Hill USA Darmendrail, Dominique BRGM France Debelle, Jean-Pol CEFIC Belgium Dijkshoorn, Pieter ERM Belgium Duque Correa, Ana Maria HPC Envirotec France Euser, Marjan NICOLE Secretariat NL Flum, Manfred SolGeo AG Germany De Fraye, Johan CH2M Hill UK Gevaerts, Wouter ARCADIS Belgium Gomez Arevalo, Francisco Javier HPC Envirotec France Govaers, Suzy UMICORE Belgium de Groof, Arthur Grontmij NL Groot, Hans Deltares NL Grundfelt, Bertil KemaktaKonsult Sweden Guérin, Valérie BRGM France Habashi, Nahal Saipem S.p.A. Italy Haerens, Bruno URS Belgium Belgium Hayes, Tom Ecologia UK Van Herreweghe, Samuel MAVA/EnISSA Belgium Hintzen, Ulrike HPC AG Germany de la Hougue, Christel UPDS France Hube, Daniel BRGM France Jacques, Diederik SCK-CEN Belgium Jacquet, Roger Solvay S.A. Belgium de Jong, Klaas HMVT NL Jubany, Irene Centre Tecnológic de Manresa Spain Karg, Frank HPC Envirotec France Keijzer, Thomas Deltares NL Klein, Pierre-Yves Solenvironnement France Koschitzky, Hans-Peter University Stuttgart Germany Lambié, Beatrijs Antea Group Belgium Laperche, Valérie BRGM France Lawless, Richard WSP UK


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Leterme, Bertrand SCK-CEN Belgium MacKay, Sarah WSP Environmental UK Maerten, Kris Regenesis Ltd. Belgium Maier, Joachim ICF Environnement France Margueret, Armelle French Ministry of Environment France Marsman, Annemieke Deltares NL Matz, Pierre Solvay Research and Technology Belgium Merly, Corinne BRGM France Metz, Jérôme DEC Deme Env. Contractors Belgium Mezger, Thomas Akzo Nobel NL Moll, Ulrich LyondellBasell Industries France Nicolaes, Tom ARCADIS NL Van Nieuwenhove, Karel Antea Group Belgium Noël-Debaecker, Elise Shell Int. Petroleum Company France Nováková, Petra GEOtest NL Ohlsson, Yvonne Swedish Geotechnical Institute Sweden Ooteman, Kevin MWH NL Parkman, Rick URS Corporation Ltd. UK Pecoraro, Roberto Versalis Italy Pensaert, Stany DEC Deme Env. Contractors Belgium Petersen, Jan Region Syddanmark Denmark Pfennig, Jean Louis The Dow Chemical Company France Phipps, Oliver ERM UK Pijls, Charles Tauw NL Richard, Jan-Helge TU Braunschweig Germany van Riet, Paul Dow Benelux BV NL Rijk, Inge Witteveen+Bos NL Roeloffzen, Anton DCMR NL Roger, Alain BURGEAP France Ross, Ian FMC UK Roussel, Hélène ADEME France Salatti, Fabrizio AECOM Italy Schelwald-van der Kleij, Lida NICOLE ISG Secretariat NL Schöndorf, Thomas HPC AG Germany Sévêque, Jean-Louis UPDS France Sinke, Anja BP International UK Slenders, Hans Arcadis NL Stiels, Christian Econ Industries GmbH Germany Van Straaten, Mark MAVA Belgium Su, Nan NICOLE NL Sweeney, Rob CL:AIRE UK Thomas, Alan ERM UK UK Trezzi, Aldo ENVIRON Italy Übler, Christoph BASF SE Germany Underwood, David Shell UK Valle, Paulo ERM Belgium Vanhove, Bart CH2M Hill Belgium Verhaagen, Paul Grontmij NL Villalobos, Maria José HPC Envirotec France Visser-Westerweele, Elze-Lia NICOLE SPG Secretariat NL Voogd, Leon MWH NL Wandor, Dave Dow Chemical USA Wang, Guoqing Nanjing Inst. of Env. Sciences China Wängberg, Göran IVL Sweden Wilson, Alan ERM UK


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Appendix 2: Program NICOLE Technical Meeting 4 December, 2012, Brussels, Belgium

Chairman Morning Session: Roger Jacquet, Solvay, Belgium 09:00 - 09:15 Opening, welcome, introduction

by session chairman

09:15 - 09:45 High-Resolution Passive Soil Gas Sampling for Elemental Mercury Characterization Jason Cole, CH2M, Germany

09:45 - 10:15 Available Technologies and New Insights to Better Characterize Hg Contaminated Sites Valérie Guérin, BRGM, France

10:15 - 10:45 A Geochemical Framework for Mercury Contamination at Chlor-Alkali Plants Dick Brown, ERM, USA

10:45 - 11:15 Coffee break

11:15 - 11:45 Mercury Prills under a Former Chlor-alkali Plant: Significance, Distribution, Migration and Remediation Eros Bacci, University of Siena, Italy

11:45 - 12:15 Net Environmental Benefit Analysis for the Evaluation of Remedial Alternatives for Mercury Contaminated Sites Elisa Bizzotto, ENVIRON Italy

12:15 - 12:30 Discussion

12:30 - 14:00 Lunch

Chairman Afternoon Session: Laurent Bakker, TAUW, the Netherlands 14:00 - 14:30 Modelling the DNAPL Spreading Behavior of Pure Phase Elemental

Mercury in Soil and Groundwater Systems for Risk-assessment and Remediation Approaches Annemieke Marsman, Deltares, the Netherlands

14:30 - 15:00 In Situ Remediation of Hg-Zn Contaminated Soil and Groundwater by using Chemical and Physical Immobilization Technology Implemented by In Situ Grouting Jean-Daniel Vilomet and Pierre-Yves Klein, Sol Environment (Soletanche-Bachy group), France

15:00 - 15:30 Discussion

15:30 - 16:00 Coffee break


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16:00 - 16:30 In-Situ Stabilization Experiences on Mercury Contaminated Soils, Sludge, Sediments & Rubble and Passive Groundwater Remediation with Hg-Stabilization via Adsorption on Low Cost but Effective Alloy Materials: Case Studies in Germany and France Frank KARG, HPC Envirotec SA, France

16:30 - 17:00 Remediation of a Former Chlor-alkali Site in the Netherlands Stany Pensaert, DEME Environmental Contractors (DEC NV), Belgium

17:00 - 17:30 Discussion and conclusions

17:30 Adjourn


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Previous NICOLE events: Data Acquisition for a Good Conceptual Site Model, Carcassonne, France

10-11 May 2006

Making Managmenet of Contaminated Land an Obsolete Business – Challenges for the future (NICOLE 1996-2006 Ten Year Anniversary Workshop), Leuven, Belgium

5-6 October 2006

Redevelopment of sites – the industrial perspective. Akersloot, the Netherlands

14-15 June 2007

Using baselines in liability management: what do upcoming Directives require from us? Brussels, Belgium

15-16 November 2007

Sustainable Remediation, London, UK

3 March 2008

Environmental Decision Support Systems, Madrid, Spain

9-10 October 2008

Basics and Principles of Environmental Law, Brussels, Belgium

31 March 2009

Sustainable Remediation - A Solution to an Unsustainable Past? Leuven, Belgium

3-5 June 2009

From Site Closure to Disengagement, Douai, France

18-20 November 2009

Contaminated land management: opportunities, challenges and financial consequences of evolving legislation in Europe, Trieste, Italy

5-7 July 2010

Emerging contaminants and solutions for large quantities of oil contaminated soil (Technical meeting), Brussels, Belgium

4 November 2010

Operating Windows for site characterisation, Copenhagen, Denmark

25-27 May 2011

Rotterdam Revisited; a renewed look at soil and groundwater management, Rotterdam, the Netherlands

16-18 November 2011

Water in Contaminated Land Management, the challenge of preservation of our water resource, Baden-Baden, Germany and Lauterbourg, France

13-15 June, 2012

For a complete overview of all networks meetings that have been held from the start of NICOLE up to now see www.nicole.org.

http://www.nicole.org/�

Documents

SUMMARY REPORT MERCURY CONTAMINATED SITES · 2015. 2. 24. · To conduct the soil vapour sampling used, thin metal insertion rods were used to introduce samplers employing Gore-tex®