Pesticides in Nursery Runoff: Sources and Transport Processes

1. Pesticides in Nursery Runoff: Sources and Transport Processes Jay Gan Dept. Environmental Sciences UC Riverside, CA 92521 jgan@mail.ucr.edu 909-787-2712

2. Outline Nursery and pesticides Current issues How does it happen? Governing Processes

3. Nursery in CA(2001) Production sales: $3.17 billion 10.6% of CA agricultural output 2nd among all CA agricultural products 21.3% of the U.S. nursery/floriculture total (11.9% for FL) Retail sales $10.1 billion 1st in the U.S. CA horticulture industry jobs 81,011 jobs in production 87,856 jobs in retailing

4. CA Nursery Industry

5. CA Nursery Industry

6. CA Nursery Industry

8. Nurseries & Pesticides Pesticide Uses Agricultural crops Home lawns/gardens Structural/indoor pest control Nurseries Roadside Parks

10. Trend of Pesticide Use Total

11. Top Ten in California

12. Use Trend of “Reproductive Toxic” Pesticides in CA

13. Reproductive Toxic Products

14. Use Trend of Carcinogenic Pesticides in CA

15. Carcinogenic Pesticides

16. Use Trend of Cholinesterase Inhibiting Pesticides in CA

17. Cholinesterase-Inhibiting Pesticides

18. Use Trend of Groundwater-Risk Pesticides in CA

19. Groundwater-risk Pesticides

20. Surface water-Risk Pesticides Not human safety concern ! Aquatic toxicity: Organophosphate insecticides (e.g., Dusban, diazinon) Carbamate insecticides (e.g., carbaryl) Synthetic pyrethroids (e.g., cyfluthrin, permethrin, …)

25. Water Quality Issues Ground water issues Surface water issues TMDLs TMDL examples

26. Groundwater Issues The CA Picture (CDPR, CWRCB) 324 of 3,165 wells in year 2000 84 verified detections From previous use (fumigants) DBCP, EDB, 1,2-D From existing use (herbicides): Simazine, ACET (from simazine or atrazine), DACT, norflurazon, bromacil, diuron, atrazine, deethyl atrazine

28. Surface Water Quality Issues Urban surface water quality issues Pesticide detections in most streams 99% streams with 1 pesticide 70% streams with ? 5 pesticides Sustained insecticide levels Harmful to aquatic organisms Beneficial use TMDLs for many streams The new rule!

29. What is TMDL? CWA 303(d) States to make list of “impaired” waters Develop TMDLs for the listed waters TMDLs to account for all pollutants and all sources, TMDL includes non-point sources, e.g., urban and agricultural runoffs Develop implementation plans (Basin Plans or Water Quality Control Plans in CA)

30. California: RWQCBs 800 TMDLs in total 120 TMDLs in progress Amend the Basin Plan by incorporating TMDLs TMDL Elements: Problem statement Numeric targets Source analysis Allocations Implementation plan Linkage analysis Monitoring/Re-evaluation Margin of safety

33. San Diego Creek Pesticide TMDLs

34. Diazinon: 200-455 ppt ? 50 ppt 300-900% reduction! Chlorpyrifos: 87-111 ppt ? 14 ppt 600-800% reduction! Legacy pesticides: DDT, chlordane,… Urban use is the No.1 source! San Diego Creek Pesticide TMDLs

37. How Does It Happen? Storm water runoff Irrigation runoff Leaching through containers? Planting media spills? Runoff + planting media = pesticide runoff?

38. Irrigation

39. Nursery Runoff

41. Planting Media

44. Pesticides in Spilled Potting Mix

45. Loose Potting Mix

46. Governing Processes Degradation Chemical Microbial Adsorption Leaching Potential Runoff Potential

47. Transport after application

48. Degradation in Soil What is “degradation”? Structural changes caused by chemical and/or microbial reactions Desirable environmentally Pesticide-dependent Vary in different soil types Measured by persistence or “half-life” T1/2 Long “half-life” = problems T1/2 ? = leaching potential ? T1/2 ? = runoff potential ?

49. Pesticide degradation in soil

50. What Causes Degradation? Chemical reactions Hydrolysis (OPs, carbamates, etc.) – pH sensitive Photolysis – by UV, near the surface Oxidation – reduction by soil chemical species Nucleophilic attacks by soil nucleophiles Pesticide dependent Soil dependent

51. What Causes Degradation? Microbial transformations Biodegradation – bacteria use pesticides as “food” Cometabolism –degradation by “accident” Enzyme-based transformations Pesticide dependent Soil dependent Microbial ecology Organic matter plays a big role

53. Adsorption in Soil What is “adsorption”? Retention of pesticides by soil Pesticide dependent Soil dependent Organic matter content ?, adsorption ? Weak adsorption + long persistence ? worst for ground water Adsorption ? = runoff in water Adsorption ? = runoff with soil

54. Adsorption Coefficient Kd Adsorbed concentration / dissolved concentration Kd = Cs / Cw Kd ? = strong adsorption Koc Koc = Kd / OC (%) Adsorption is proportional to soil OC% Koc < 100, weakly adsorbing Koc > 1000, strongly adsorbing

60. Leaching Potential What is leaching? Ability of pesticides to move through soil to reach groundwater High leaching potential Weak adsorption Long persistence Shallow groundwater table Active water movement Sandy texture

61. Leaching and Adsorption Retardation factor: Reflect difficulty in moving with water As R increases, rate of movement decreases As Kd increases, rate of movement quickly decreases

62. GUS Index “GUS” Groundwater Ubiquity Score GUS = log(T1/2) * (4 – log(Koc)) Leaching risk Gus > 2.8: high leaching risk Gus < 1.8: low leaching risk 1.8 < GUS < 2.8: intermediate leaching risk

63. Groundwater-risk Pesticides

64. Runoff Potential Move in water Diazinon, chlorpyrifos, many herbicides Move with loose soil particles synthetic pyrethroids

65. Runoff Long persistence + weak adsorption ? high runoff potential Long persistence + strong adsorption ? intermediate runoff potential Short persistence + weak adsorption ? Transient Short persistence + strong adsorption ? Harmless

66. Contact Info: Jay Gan Dept. Environmental Sciences UC Riverside, CA 92521 jgan@mail.ucr.edu (909) 787-2712