The Fate of Pesticides in the Environment

Transcription

1 The Fate of Pesticides in the Environment Brent Clothier & Steve Green Environment Group, HortResearch Palmerston North

2 Soils the Final Frontier A Special Section in Science (v 304, 11 June 2004), Fiona Profitt (p1617) writes Soils are a sponge for pesticides and other nasty compounds filtering down from the surface. Yet experts have only a sketchy idea of how the ground copes with this toxic trickle. Regulatory agencies are crying out for data to improve assessments of environmental health risks, as there are literally tens of millions of chemicals in use out there. The US Geological Survey and a handful of other agencies are planning an ambitious mission: a soil geochemical survey of all of North America

3 Land intensification often requires irrigation, & a greater use of agrichemicals What happens to the soil and the water underneath?

4 New Zealand Wine - Riches of a Clean Green Land Herbicides are used for weed control Fungicides for mildew and botrytis cinerea Insecticides for mealy bug, rollers & mites CCA-treated posts are used as vine supports

5 The Push & Pull for Better Pesticide Practices The Push The Resources Management Act 1990 Section 15 (1) No person may discharge any (a) Contaminant or water into water; or (b) Contaminant onto or into land in circumstances which may result in that contaminant entering water The Pull EUREPGAP (Good Agricultural Practices) 3. Crop Protection b. Choice of chemicals #1 Is the product appropriate? Major Must c. Advice on quantity & type of pesticide #1 Recommendations been given by qualified advisors? Major Must

6 Where do the chemicals go? (from Sarmah, Müller & Ahmad, 2004)

7 After landing on foliage Degrade to harmless substances. Degradation enhanced by sunlight & temperature. Wash off the foliage. Enhanced by rainfall soon after application. Remain on the foliage then the leaves fall and breakdown All of these processes are affected by pesticide chemistry

8 After arriving on the soil Degrade to harmless substances. - Enhanced by short half-life, plus warm & moist soils Leach through the soil Exacerbated by high rainfall, free-draining soils, low soil organic matter, pesticides with little attraction to soil organic matter Accumulate in the soil Long-lived pesticides strongly attracted to soil organic matter

9 Chemical properties of each pesticide Table A3. Pesticide profile and properties. K OC is a measure of pesticide mobility, T½ is a measure of pesticide persistence, and LD 50 is a lethal dose for a 50% kill (see text for details). Pesticide ai Type Profile Koc Half life T½ [d] amitrole H Non-selective control of annual & perennial weeds buprofezin I Control mealy bug, scales and whitefly captan F Broad spectrum control of fungal disease chlorothalonil F Broad spectrum control of fungal disease chlorpyrifos I Broad spectrum control of most insects Oral Dermal LD 50 LD 50 [mg/kg rat] [mg/kg rat] Toxicity > 1,100 >10,000 Harmful > 23,200 > 5,000 Low > 9,000 ~ 10,000 Low > 10,000 > 10,000 Low > 135 > 2,000 Poison diquat H Contact herbicide to control > 230 > 500 Poison annual weeds dithianon F A protectant fungicide > 630 > 2000 Poison Risk depends on mobility & persistence. Hazard depends on toxicity

10 SPASMO Modelling Pesticide Fate: Predicting Where & How Much? M A (1-f A ) f W M F Plants e (-KF.t) M P Resident mass M A = applied M F = on foliage M S = in soil f A M S Soil (-KS. e t) M D Mass losses M P = volatilization M D = degradation M L = leachate Modelling to predict build-up f L Water M L Modelling to predict leachate

11 SPASMO Verified: Residues on Horotiu silt loam Picloram [mg/kg] Hexazinone [mg/kg] Procymidone [mg/kg] 15 data 0.1 m 10 Model 0.1 m Day 15 data 0.1 m 10 Model 0.1 m Day 15 data 0.1 m 10 Model 0.1 m 5 Hexazinone [mg/l] Hexazinone [mg/l] Hexazinone [mg/l] 0.6 data 0.2 m Model 0.2 m Day 1 data 0.6 m 0.8 Model 0.6 m Day 0.25 data 1.5 m 0.2 Model 1.5 m Day Day Soil residues at 0.1 m leaching degradation exchange Hexazinone at depth leaching degradation exchange Data from ESR [Murray Close]

12 The SPASMO model pesticide fate Mass applied [kg-ai/ha] MTcrop MT soil Bentazone on pasture Year Bentazone is highly mobile but rapidly degraded in soil. It has a low risk of leaching Mass applied [kg-ai/ha] MTcrop MTsoil Mancozeb on onions Year Mancozeb is strongly adsorbed, moderately persistent in soil. It has a low risk of leaching 40.0 Mass applied [kg-ai/ha] MTcrop MTsoil Copper on onions Copper is strongly adsorbed and does not degrade in soil. Continued use of will lead to accumulation Year

13 (Report to Auckland Regional Council & Environment Waikato) Modelling to assess the risks 1e+0 Maize on a Taupo soil Pesticide Concentration [mg/l] 1e-1 1e-2 1e-3 1e-4 1e-5 1e-6 1e-7 Metribuzin Metolachlor Cyanazine 1e Short term risk Time [y] Elevated risk

14 The Growsafe Calculator: Pesticide Risk Reduction for Soil & Groundwater A Sustainable Farming Fund project by the NZ Agrichemical Education Trust involving the Hawke s Bay Regional Council, Greater Wellington, Environment Waikato, Tasman District Council, and Marlborough District Council. Plus support from Gisborne District Council, Auckland Regional Council, Environment Canterbury, Otago Regional Council, Horizons Council, Environment Bay of Plenty, & the Northland Regional Council, that is 12 Local Authorities, plus Vegfed NZ Winegrowers Zespri International NZ Pipfruit NZ Fruitgrowers Federation Arable Food Industry Council NZ Avocado Growers Summerfruit NZ Agcarm

15 The Growsafe Calculator: Pesticide Risk Reduction for Soil and Groundwater Coverage over 12 regions in New Zealand Some 31 crops considered Spray diaries for 143 different pesticides A total of 149 combinations of crop-by-region Daily weather records over 30 years used Some 5-8 named soils per region A total of 28,399 SPASMO simulations, each 10,950 days Rankings of products in terms of o Short-term leaching risk o Long-term leaching risk o Short-term soil build-up o Long-term soil buidl-up Impact of number of applications

16 Critical Values in Water 3m Few pesticides in the New Zealand Drinking Water Standard. If not Our Critical Values developed from Acceptable Daily Intake values from the Australian database Average person weight & their likely daily intake of groundwater (MoH) Details provided in Background Information

17 Short & Long-Term Leaching Risks Short-term, on 10% of (worst) days, Amitrole exceeds the CV. The next, Terbuthylazine is at 50% CV. Long-term, on average over 30 years, nothing approaches 10% of CV. Terbuthylazine is the riskiest.

18 Impact of Soil Type on Leaching On the stony Omahu gravels, if apples were grown, Terbumeton is a long-term ris Just down the road, on a Twyford silt loam there is little leaching risk from spray-diary usage

19 Soil Build-Up Short & Long-Term Risks 2.0 Mass applied [kg-ai/ha] MT crop MT soil Bentazone on pasture Year Bentazone is highly mobile but rapidly degraded in soil. 4.0 Mass applied [kg-ai/ha] MT crop MT soil Mancozeb on onions Year Mancozeb is adsorbed & persistent in soil. The number of applications is critical 40.0 Mass applied [kg-ai/ha] MT crop MT soil Copper on onions Copper is strongly adsorbed & does not degrade in soil

20 Short & Long-Term Soil Build-Up of Pesticides Mancozeb, here applied 15 times a season, will over the short-term, build-up in the soil. Because Mancozeb does not degrade quickly, it will continue to build-up. One application of copper poses a risk

21 Legacy Risks from Former Practices Dip Formulation Solubility [mg/l] Koc [L/kg] half life [d] AFR index Lindane DDT Arsenic Dieldrin Diazinon Aldrin Cypermethrin Mobility depends on Solubility and Koc (in solution, or sorbed to soil) Persistence depends on pesticide Half-life (degradation, leaching) (SMF Project: Guidelines for the the Management of Sheep Dip Sites)

22 Modelling to Assess Pesticide Fate 1000 Soil residual [mg/m 2 ] Arsenic Dieldrin Lindane Diazinon Year (SMF Project: Guidelines for the the Management of Sheep Dip Sites)

23 Modelling to Pesticide Fate Dieldrin Movement to depth (still rising at 6 m after 40 yrs) Some degradation Dieldrin resident in soil Dieldrin concentration [mg/m 2 ] m 0.2 m 0.5 m 1.0 m 3.0 m 6.0 m Year (SMF Project: Guidelines for the the Management of Sheep Dip Sites) C 12 H 8 Cl 6 O

24 The Pesticide Problem around the World Tonga A NZAID/EU projec Tongatapu s fresh water lenses

25 Summary: The fate of a pesticide is a result of a complex interaction of soil, crop, weather, & the pesticide properties, plus spray practices New tools are being developed to identify at-risk scenarios, current & legacy, that are likely to cause problems of leaching or accumulation These new tools could help users identify chemical alternatives & better practices that are more environmentally friendly