Remediation of Heavy MetalRemediation of Heavy MetalContaminated SoilContaminated Soil

Presented by:Presented by:Jamal suliman elgosniJamal suliman elgosni

Under supervision of Dr Maher George NassemUnder supervision of Dr Maher George Nassem

IntroductionIntroduction contamination of soils has

become a serious problem in areas of intense industry and agri- culture. HMs are deposited in soils by atmospheric input and the use of mineral fertilizers or compost, and sewage sludge disposal. Soils polluted with HMs pose a health hazard to humans as well as plants and animals, often requiring soil remediation practices. Conventional remediation methods usually involve excavation and removal of contaminated soil layer, physical stabiliza-tion (mixing of soil with cement, lime, apatite etc.), or washing of contaminated soils with strong acids or HM chelators (Berti et al., 1998, Steele and Pichtel, 1998)

Heavy metal (HMHeavy metal (HM))

Sources of Soil ContaminationSources of Soil Contamination soils in both industrial parks and near small

factories outside the parks are affected by a wide variety of contaminants. The most serious sources of soil contamination are (EPA/ROC 1994): 1. Heavy metals in hazardous waste, including materials from chemical production, dyeing, electroplating and heat treatment, the production of batteries, metal treatment, mining and extractive industries, scrap yards, service stations and tanning 2. Hazardous organic waste materials, including those from medical centers, oil production and storage, and paint and pesticide production3. Corrosive metal waste materials, including those from acid/alkali plants and chemical engineering works.

Sources of heavy metals in soils and Sources of heavy metals in soils and their expected ionic species in soil their expected ionic species in soil

solutionsolution..

METALS AT CONTAMINATED METALS AT CONTAMINATED SITESSITES

• Approximately 75% of Superfund sites for which Records of Decision (RODs) have been signed contain metals as a form of contamination. Some of these sites contain mixed metal-organic wastes for which metals might not be the primary contaminant of concern.

• The most common metals found at contaminated sites are (U.S. EPA, 1996b), in order: lead (Pb), chromium (Cr), arsenic (As), zinc (Zn), cadmium (Cd), copper (Cu), and mercury (Hg). Figure 1 summarizes the frequency with which these metals occur at Superfund sites.

Figure 1. Metals Most Commonly Present in all Figure 1. Metals Most Commonly Present in all Matrices at Superfund Sites (from U.S.Matrices at Superfund Sites (from U.S.

EPA, 1996)EPA, 1996)

The range of contaminant concentrations and the physicaland chemical forms of contaminants will depend on activities and disposal patterns for contaminated wastes on the site.

The contamination level of trace elements in The contamination level of trace elements in rural soils of the worldrural soils of the world

Remediation can be achieved in Remediation can be achieved in several ways: physical, chemical several ways: physical, chemical

and biologicaland biological• Physical methods of remediation include

verification, encapsulation, soil washing, artificial ground freezing, and electro kinetics

• The chemical methods use chemical treatment to remove or decrease the availability of metals to living things and groundwater, and they include neutralization, solidification

• Biological methods make use of plants and microorganisms to remedy metal contaminated soil

Soil amendments for remediationSoil amendments for remediation

• Recent research has shown that chemical amendments, such as synthetic organic chelates, can enhance phytoextraction by increasing HMs bioavailability in soil thus enhancing plant uptake, and translocation of HMs from the roots to the green parts of tested plants (Epstein et al., 1999; Huang et al., 1997). Of the chelates tested, ethylene diamine tetraacetic acid (EDTA) was often found to be the most effective (Blaylock et al., 1997).

• The addition of EDTA enhanced accumulation of HMs The addition of EDTA enhanced accumulation of HMs in green parts of the test plant. However, EDTA addition in green parts of the test plant. However, EDTA addition also caused leaching of Pb, Zn and Cd through the soil also caused leaching of Pb, Zn and Cd through the soil profile and had toxic effects on test plants and soil profile and had toxic effects on test plants and soil microorganismmicroorganism

Chelating compounds

PhosphatePhosphate compoundscompounds

• Phosphate compounds enhance the immobilization of metals in soils through various processes including: direct metal adsorption by P compounds, phosphate anion-induced metal adsorption, and precipitation of metals with solution P as metal phosphates

Depending on the source, soil application of P Depending on the source, soil application of P compoundscompounds can cause direct adsorption of metals onto these can cause direct adsorption of metals onto these compoundscompounds through increased surface charge and enhanced anion-through increased surface charge and enhanced anion-inducedinduced metal adsorption. Metal adsorption onto apatite is metal adsorption. Metal adsorption onto apatite is facilitatedfacilitated through the exchange of Ca2+ from the apatite through the exchange of Ca2+ from the apatite particle with theparticle with the metal cations in soil solutionmetal cations in soil solution

•Liming materialsLiming materials

• These include calcite (CaCO3), burnt lime (CaO), slaked lime (Ca(OH)2), dolomit(CaMg(CO3)2)and slag (CaSiO3). The acid-neutralizing value of liming materials is expressed in terms of calcium carbonate equivalent (CCE), expressed as a weight percentage of pure CaCO3.Liming, as part of normal cultural practices, has often been shown to reduce the concentration of Cd, Pb and other metals in edible parts of crops. Similarly, liming serpentine soils containing toxic levels of Ni has been shown to alleviate the phytotoxic effects of Ni. In these cases, the effect of liming materials in decreasing metal uptake by plants has been attributed both to decreased mobility in soils (through adsorption/precipitation) and to the competition between Ca2+ and metals ions on the root surface.

Organic compostsOrganic composts• The major sources of organic composts

include biosolid and animal manures livestock manure and other organic wastes, especially when they are composted in the presence of sewage sludge Most manure products contain low levels of heavy metals (except Cu and Zn in swine manure and As in poultry manure).

Manure byproducts that are low in metal Manure byproducts that are low in metal content can be content can be used to immobilize metal contaminants in used to immobilize metal contaminants in soilssoils

CONCLUSION OF SOME CONCLUSION OF SOME RESEARCHESRESEARCHES

• After 30 - 40 years of intensive use of fertilizer in lowland areas of West Java, including rock phosphate, the concentration in the soil of heavy metals such as lead and cadmium still remains below toxic levels. However, these elements are sometimes present naturally in rock phosphate, so that continuous monitoring is needed. • The results showed that vetiver grass could grow well on soils contaminated with high concentrations of lead and cadmium. By concentrating the contaminants in its roots, the vetiver grass reduced the concentration of lead in soil by as much as 38 - 60%, and cadmium by 35 - 42%.

POLLUTION OF SOIL BY AGRICULTURAL AND INDUSTRIAL

WASTE

RELATIONSHIP BETWEEN HEAVY RELATIONSHIP BETWEEN HEAVY METAL CONCENTRATION IN SOILS METAL CONCENTRATION IN SOILS OFTIAWAN AND UPTAKE BY CROPSOFTIAWAN AND UPTAKE BY CROPS

There is no clear relationship between the concentration of cadmium in brown rice, and the amount of cadmium extracted from the soil by 0.1 M HCl. This means that the 0.1 M HCl extraction method is not suitable for predicting the uptake of soil cadmium and its presence in rice grain.Exchangeable (or available) forms of cadmium and lead can be transformed into unavailable forms if the soil is amended with manganese oxide, calcium carbonate or zeolite. The concentration of cadmium in the soil solution, and levels of cadmium extracted by DTPA and EDTA, decreased significantly when the soil was treated with calcium carbonate. Treatments of zinc oxide, however, had no significant effect.

REFERENCESREFERENCES 1.Chaney, R.L ., S.L . Brown, J.S . Angle, T.I . Stuczynski, W.L . Daniels, C.L . Henry, G.

Siebielec, Y.-M . Li, M. Malik, J.A . Ryan and H. Compton. 2000. In situ Remediation/ Reclamation/Restoration of Metals Contaminated Soils using Tailor-Made Biosolids Mixtures. In Proc Symposium on Mining, Forest and Land Restoration: The Successful Use of Residuals/Biosolids /Organic Matter for Reclamation Activities (Denver, CO, July 17-20, 2000). Rocky Mountain Water Environment Association, Denver, CO

2. Diah Setyorini, Tini Prihatini and Undang Kurnia,2002 .POLLUTION OF SOIL BY AGRICULTURAL AND INDUSTRIAL WASTE. Centre for Soil and Agroclimate Research and Development, Jalan Ir. Juanda No. 98 Bogor 16123, Indonesia

5. Zueng-Sang Chen,2000. relationship between Heavy Metal Concentrations in Soils of Taiwan and Uptake by Crops. Department of Agricultural Chemistry National Taiwan University Taipei Taiwan, ROC, 2000-03-01 106

3.Joonki yoon,2005. PHOSPHATE-INDUCED LEAD IMMOBILIZATION IN CONTAMINATED SOIL . A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE 4. Nanthi S. Bolan Santiago Mahimairaja and Julien Lefeuvre,2003.

Remediation of heavy-metal contaminated soils –to mobilize or immobilize?. Institute of Natural Resources, Massey University, and Marseille University, France. New Zealand Science Review Vol 60 (4) 2003

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