Water Research Australia Research soluti ons through collaborati on July 2015 Page 1

Fact Sheet Shining light on pesti cide monitoring

Pesticide use in AustraliaPesti cides are widely used in agriculture, forestry, recreati on grounds, gardening, home and industry. Pesti cide use can be regular or seasonal depending on the life cycle of the target organisms and the nature of the environment surrounding them. Their applicati on regimen can be aff ected by a variety of environmental factors such as sunlight, rain, temperature, microbial acti vity, soil type and pH.1,2 These factors can aff ect pesti cide half-life and persistence and consequently have implicati ons for the volume of pesti cide applied, the rate of uptake by the target organism and the mobility of the pesti cide on the soil and into surface and ground waters.3,4

There are four major categories of pesti cides: herbicides, insecti cides, fungicides, and plant growth regulators. The Australian Drinking Water Guidelines (ADWG) also consider rodenti cides, nemati cides and miti cides to be sub-categories of pesti cides.2 Figure 1 illustrates the annual relati ve pesti cide usage in Australia in 2002.3

The main herbicide of choice in Australia is glyphosate. Also known as RoundupTM, glyphosate is a broad spectrum, non-selecti ve herbicide. Atrazine, simazine and hexazinone are selecti ve herbicides which target broad-leafed weeds and grasses1 and are used to a lesser extent. 2,4-Dichlorophenoxyaceti c acid (2,4-D) and 2-methyl-4-chlorophenoxyaceti c acid (MCPA), paraquat dichloride and diquat are also noteworthy in that they are used, but in smaller quanti ti es.3

The most commonly used insecti cides are the organophosphates, which include parathion methyl, cloropyriphos, dimethoate, profenfos and iazinon. The second most commonly applied insecti cides are the carbamates, of which metam sodium is the most famous derivati ve. Both the organophosphates and the carbamates are neurotoxic and act as acetylcholinesterase inhibitors in animals. Lastly the pyrethroids and pyrethrins are less commonly used.3

Fungicides are used to treat a wide range of fungal diseases, including seeds on fi eld crops. About 20 diff erent fungicides are used in Australia, most commonly mancozeb and captan.3

The main plant growth regulator used is ethephon, which is an ethylene gas generator that opti mises pest and blemish-free fruit crops.3

Figure 1. Pesti cide use by category in Australia 3

The need for pesticide monitoringPesti cides can be found in natural waters at concentrati ons ranging from nanograms per litre (ng/L) to milligrams per litre (mg/L) mostly as a result of rain and fl ooding events post-spraying. However, spray drift , off -target damage, accidental spills and emergency use may also result in water contaminati on.2,5 The bioacummulati on of certain pesti cides may occur in the food chain depending on the mode of acti on of the pesti cide, its physicochemical properti es and its abundance and persistence in the environment.2,4 Depending on the dose and stage of development of the exposed organism, pesti cides can be harmful to their nervous, endocrine and reproducti ve systems.2,6–8

Pesti cides may also be present in sources of drinking water and occasionally persist through treatment at extremely low concentrati ons (ng/L-µg/L). The Nati onal Health and Medical Research Council (NHMRC) has established aestheti c guideline values and health-related guideline values in the ADWG for short and long-term exposure to pesti cides in

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drinking water (ng/L-mg/L), respecti vely.2

The detecti on of such low concentrati ons requires the use of highly sensiti ve analyti cal methods and frequent sample collecti on prior to scheduled analyses. Currently there is no integrated pesti cide monitoring or reporti ng system in Australia. Instead, water uti liti es individually monitor for certain pesti cides and investi gate when a pesti cide has been detected above the recommended guideline value.2 The list of pesti cides monitored may vary between water uti liti es, states and territories.

Catchment-to-consumer monitoringCurrent pesti cide monitoring technologies (Table 1) involve scheduled grab sample collecti on, ti me-integrated sampling, and fl ow-event-triggered sampling followed by laboratory analysis using mainly high performance liquid chromatography (HPLC)/gas chromatography (GC) coupled with mass spectrometry (MS).1,9,10 Despite being the best current industry standard or practi ce, these monitoring methods have spati al and temporal limitati ons. Scheduled sampling may miss or underesti mate polluti on episodes that occur at certain polluti on hotspots or between sampling events. The temporal limitati ons of these methods can limit the ability of water authoriti es to react and track the polluti on back to its point source, as there is oft en a signifi cant ti me lag between sampling and laboratory analysis.9-11

Ideally, catchment-to-consumer monitoring should involve sensiti ve analyti cal methods for conti nuous real-ti me on-site water monitoring. Portable monitors placed at fi xed strategic locati ons can facilitate conti nuous monitoring and investi gati ons. Analogous remote sensing technologies have been deployed in the fi eld to conti nuously monitor for other physicochemical water quality parameters such as temperature, pH, and dissolved oxygen. However, the conti nuous on-site monitoring of organic pollutants such as pesti cides has not yet been commercially implemented in the fi eld due to the complexiti es of portability, detecti on sensiti vity, sample matrix interferences, sample preconcentrati on challenges and instrument maintenance issues.12 PhD student Ana Marti ns has been looking to

Sampling Advantages Disadvantages

Grab sampling Accurate at a specifi c ti me and locati onInexpensive and can be planned ahead

Intermitt ent sampling may miss worst-case scenarios Results may be biased

Time/Flow-Integrated

Accurate over a longer period of ti meInexpensive and can be planned aheadDetects relati ve changes in concentrati on over ti meLong-term average exposure patt ern

Underesti mates peak concentrati onExpensive depending on the type of sampling (passive/acti ve)Passive sampling needs more research before it can be used routi nely/commercially

Flow-event-triggered

Inexpensive but cannot be planned ahead Sampled at uniform intervals of fl ow volume Detects absolute concentrati on per fl ow volumeShort-term peak exposure and durati on

Inaccurate at low fl ow volumes Flow-dependent sampling may miss the exposure patt ern of conti nuously applied pesti cidesExpenditures are subjected to unpredictable parameters (eg. weather)

address the technological challenges of pesti cide monitoring in her thesis at RMIT University.

Recent research: Development of a portable instrument for real-time on-site water monitoringThe three main challenges posed by conti nuous on-site monitoring of organic pollutants in water are: analyti cal sensiti vity, robustness and miniaturisati on. Portable instruments have to be much smaller and more robust than their laboratory counterparts and yet must deliver equally sensiti ve analyti cal results. They must operate on a fl ow-through regimen with accuracy and reliability. Real-ti me monitoring of pesti cides demands microanalyti cal methods that are specifi c, fast and sensiti ve enough for the detecti on of low concentrati ons (ng/L-µg/L) in small volumes of conti nuously fl owing sample.13

SAW Device

Micropump

SAW driver circuit

Reaction Chamber

Photomultiplier Tube

Figure 2: Miniaturised FIA-inspired prototype showing the SAW Micromixer, micropumps, driver circuit, photomulti plier tube.13

Examples of sensiti ve microanalyti cal methods suitable for fi eld instrumentati on include chemiluminescence and fl uorescence detecti on. Luminescent reacti ons can be specifi c to certain functi onal groups or molecules and react in small quanti ti es at fast ti me scales without the need for large quanti ti es of solvents.14 The light emitt ed by these luminescent reacti ons can be captured by portable light

Table 1. Advantages and disadvantages of the current pesti cide monitoring strategies.9

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detectors and correlated to the concentrati on of analyte in a fully automated system. Flow injecti on analysis (FIA) systems are among the most promising candidates to perform luminescence microanalyses in the laboratory. There have been few att empts to miniaturise FIAs into portable systems.15–17 A miniaturised prototype of the instrument developed at RMIT University is shown in Figure 2.

The challenges of miniaturisationMiniaturisati on poses a challenge to conventi onal FIA systems, as passive mixing is less effi cient at the microscale where laminar fl ow regimes predominate over turbulent fl ow. This has an impact on the yield of the luminescent reacti ons as these are diff usion-limited and have lower yields under laminar fl ow conditi ons.18 To overcome these limitati ons, WaterRA student Ana Marti ns has developed a micromixing system that uti lises surface acousti c wave (SAW) technology to drive acti ve micro mixing (Figure 3) in a portable microfl uidic platf orm.13

Figure 3. Image of the chemiluminescent reacti on between the test substance L-proline and the chemiluminogenic reagent Tris(2,2ʹ-bipyridyl)dichlororuthenium(II) hexahydrate. The circular moti on demonstrates the enhanced mixing achieved using surface acousti c waves. The energy of the waves is transferred to the liquid to drive acti ve mixing.

The technology uti lises nanometre amplitude high frequency (megahertz MHz) electromechanical waves that propagate on the surface of a piezoelectric crystal coupled to a custom-made micromixer chamber. The SAW micromixer chamber is fully transparent and can be customised for the analysis of diff erent sample volumes at diff erent fl ow rates. The transparent chamber is fi tt ed with a sensiti ve light detector (photomulti plier tube) coupled to data logger soft ware (LabView) for the real-ti me analysis of chemiluminogenic pesti cides (See Table 2)19.

As Figure 4 shows, the use of the SAW device has increased the mixing index by approximately fi ft een fold. In the laboratory, the system has successfully detected 0.02 µg/L of the test substance L-proline and 1.0 µg/L of the pesti cide glyphosate (ADWG Health Guideline Value2 1.0 mg/L) in ultrapure water. The system can be fully miniaturised into

Table 2: Chemiluminogenic pesti cides19

a handheld microfl uidic platf orm that weighs under 150 grams. Coupled to small fi eld computer or remote data logger and associated parts and reagents the total instrument weight could be less than 2.5kg. The next phase of the study will be to incorporate an in-line solid phase extracti on method to eliminate interferences from surface water samples prior to analysis. In the future, the system may uti lise molecularly imprinted polymers as a sophisti cated extracti on step to target specifi c pesti cides for sample preconcentrati on prior to analysis.20–23

Figure 4. SAW Micromixer chemiluminescent enhancement13

Enhanced microanalysis and its applicationsThe proposed microfl uidic platf orm is highly versati le and can be uti lised for the analysis of any chemiluminogenic species in the liquid phase. It can also be fi tt ed with an emission source and excitati on/emission fi lters to perform enhanced fl uorescence microanalyses (Figure 5).12 In this case, the instrument may be uti lised to monitor the concentrati on of any fl uorescent species: molecules, toxins, biomolecules, immunoassays, bead-based assays, viruses, bacteria, organelles, and single cells. Single cell monitoring is an ever growing fi eld in medical diagnosti cs and pathology extending from liquid biopsies to the environmental monitoring of waterborne pathogens,

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such as viruses, bacteria and protozoans.24–26 The proposed system has been patented and granted a Victorian Technology Development Voucher for further development. It has promising applicati ons ranging from environmental monitoring to medical and point-of-care diagnosti cs.

Figure 5: Projected adaptati ons for fl uorescence analysis.

References1. Gallen C, Devlin M, Thompson K, Paxman C, Mueller J.

Pesti cide monitoring in inshore waters of the Great Barrier Reef using both ti me-integrated and event monitoring techniques (2013 - 2014).

2. NHMRC N. Australian drinking water guidelines paper 6 nati onal water quality management strategy. Nati onal Health and Medical Research Council, Nati onal Resource Management Ministerial Council, Commonwealth of Australia, Canberra 2011.

3. Radcliff e JC. Pesti cide use in Australia. Australian Academy of Technological Sciences and Engineering, 2002.

4. Greenhalgh R, Baron R, Desmoras J, Engst R, Esser H, Klein W. Defi niti on of persistence in pesti cide chemistry. Internati onal Union of 1980.

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8. Smith R, Middlebrook R, Turner R, Huggins R, Vardy S, Warne M. Large-scale pesti cide monitoring across Great Barrier Reef catchments-paddock to reef integrated monitoring, modelling and reporti ng program. Marine polluti on bulleti n 2012; 65: 117–127.

9. Bundschuh M, Goedkoop W, Kreuger J. Evaluati on of pesti cide monitoring strategies in agricultural streams based on the toxic-unit concept—Experiences from long-term measurements. Science of the Total Environment 2014; 484: 84–91.

10. Schä fer RB, Petti grove V, Rose G, Allinson G, Wightwick A, von der Ohe PC et al. Eff ects of pesti cides monitored with three sampling methods in 24 sites on macroinvertebrates and

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11. Trainer E, Roberts S, Read S, Adams P. An Evaluati on of the Standard Post-Rain Pesti cide Monitoring Program for Surface Waterways. 2010.

12. Storey MV, van der Gaag B, Burns BP. Advances in on-line drinking water quality monitoring and early warning systems. Water Research 2011; 45: 741–747.

13. Gracioso Marti ns AM, Glass NR, Harrison S, Rezk AR, Porter NA, Carpenter PD et al. Toward Complete Miniaturisati on of Flow Injecti on Analysis Systems: Microfl uidic Enhancement of Chemiluminescent Detecti on. Analyti cal chemistry 2014.

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15. Adcock JL, Francis PS, Barnett NW. Acidic potassium permanganate as a chemiluminescence reagent—A review. Analyti ca chimica acta 2007; 601: 36–67.

16. Galeano Dí az T, Acedo Valenzuela M, Salinas F. Determinati on of the pesti cide Naptalam, at the ppb level, by FIA with fl uorimetric detecti on and on-line preconcentrati on by solid-phase extracti on on C< sub> 18</sub> modifi ed silica. Analyti ca Chimica Acta 1999; 384: 185–191.

17. Gámiz-Gracia L, Garcia-Campaña AM, Huertas-Pérez JF, Lara FJ. Chemiluminescence detecti on in liquid chromatography: Applicati ons to clinical, pharmaceuti cal, environmental and food analysis—A review. Analyti ca chimica acta 2009; 640: 7–28.

18. Mansur EA, Ye M, Wang Y, Dai Y. A state-of-the-art review of mixing in microfl uidic mixers. Chinese Journal of Chemical Engineering 2008; 16: 503–516.

19. Gámiz-Gracia L, Garcí a-Campaña AM, Soto-Chinchilla JJ, Huertas-Pérez JF, González-Casado A. Analysis of pesti cides by chemiluminescence detecti on in the liquid phase. TrAC Trends in Analyti cal Chemistry 2005; 24: 927–942.

20. Sun Z, Schüssler W, Sengl M, Niessner R, Knopp D. Selecti ve trace analysis of diclofenac in surface and wastewater samples using solid-phase extracti on with a new molecularly imprinted polymer. Analyti ca chimica acta 2008; 620: 73–81.

21. Jenkins AL, Yin R, Jensen JL. Molecularly imprinted polymer sensors for pesti cide and insecti cide detecti on in water. Analyst 2001; 126: 798–802.

22. Djozan D, Ebrahimi B. Preparati on of new solid phase micro extracti on fi ber on the basis of atrazine-molecular imprinted polymer: Applicati on for GC and GC/MS screening of triazine herbicides in water, rice and onion. Analyti ca chimica acta 2008; 616: 152–159.

23. Amalric L, Mouvet C, Pichon V, Bristeau S. Molecularly imprinted polymer applied to the determinati on of the residual mass of atrazine and metabolites within an agricultural catchment (Brévilles, France). Journal of Chromatography A 2008; 1206: 95–104.

24. Ding X, Li P, Lin S-CS, Stratt on ZS, Nama N, Guo F et al. Surface acousti c wave microfl uidics. Lab on a Chip 2013; 13: 3626–3649.

25. Wu Y, Nie F, Xia D. Chemiluminescence assay for the glycoprotein tenascin-C based on aptamer-modifi ed carboxylated magneti c carbon nanoparti cles. Microchimica Acta 2014; : 1–6.

26. Adcock JL, Terry JM, Barrow CJ, Barnett NW, Olson DC, Francis PS. Chemiluminescence detectors for liquid chromatography. Drug testi ng and analysis 2011; 3: 139–144.

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