Comparison of Pesticide Runoff from Organic and ... - ACS Publications

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Chapter 9

Comparison of Pesticide Runoff from Organic and Conventional Walnut Orchards Nicole David,*,1 Fred Thomas,2 and Debra Denton3 1San

Francisco Estuary Institute, 7770 Pardee Lane, 2nd Floor, Oakland, CA 94621, USA 2CERUS Consulting, 2119 Shoshone Avenue, Chico, CA 95926, USA 3U.S. Environmental Protection Agency, 1001 I Street, Sacramento, CA 95814, USA *[email protected], Tel: 1-510-746-7386, Fax: 1-510-746-7300

Contamination from pesticide and nutrient applications to orchard crops is a major water quality issue in California. The goals of this study were to compare pesticide concentrations in water and sediment in runoff from organic and conventional walnut orchards and to compare the observed concentrations to water quality criteria and aquatic life benchmarks. Water and sediment samples were collected from five orchards over two years. Slightly lower, but not significantly different, pesticide concentrations for several pesticides (chlorpyrifos, diazinon, dimethoate, lambda-cyhalothrin, and esfenvalerate) in runoff from organic orchards were measured compared to the conventional orchards. Average concentrations of bifenthrin in sediment were statistically significantly lower (p < 0.05) at the organic sites compared to the conventional sites. This work indicates that BMP implementation and organic farming practices are effective in minimizing concentrations of pesticides in orchard runoff. Keywords: organophosphate pesticides; agricultural runoff; organic; walnuts

pyrethroids;

© 2011 American Chemical Society In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.


Introduction Intensive use of organophosphate (OP) pesticides, pyrethroids, herbicides, and fungicides in orchards and other agricultural fields is a significant source of pesticide contamination to water bodies in the Central Valley of California (1, 2) (Figure 1). The Sacramento River watershed (Figure 1) is included on the 303(d) List of impaired water bodies and revised Total Maximum Daily Loads (TMDLs) for chlorpyrifos and diazinon were approved by the State Water Resources Control Board in 2008 (3). Water and sediment samples were collected from several orchard tail ditches to evaluate improvements in water and sediment quality due to organic growing practices. Pesticides and pesticide groups included in this study were selected based on recommendations by the State Water Board, amounts of active ingredient applied in walnuts according to the pesticide use report, and the capability of the analytical laboratory.

Materials and Methods Study Area and Sampling Locations All sampling sites were located in Solano County in the Sacramento Valley (Figure 1). Organic walnuts are grown without using most conventional pesticides, fertilizers made with synthetic ingredients or sewage sludge. Replacing the use of pesticides are Best Management Practices (BMPs), which emphasize the use of renewable resources and the conservation of soil and water. BMPs implemented by certified organic farmers included monitoring of pest pressures and soil fertility, applying organic pesticides and nutrients, using pheromone disruption, cover crops, filter strips, and beneficial insects. In conventional farming, chemical plant protectants, herbicides, and chemical fertilizers are common. Some of the conventional orchards monitored in this study included BMPs, e.g., biological control (bats were successfully used for the control of codling moths). Walnut orchards were selected with the intention of covering geographical areas with similar crops, site characteristics, and soil types to provide a good comparison between organic and conventional farming. The orchards were between 12 and 32 ha and were located within an 8 km radius of each other; hence, they experienced similar pest problems and rainfall. All monitored orchards were flood irrigated between April and September with no dormant spray applications during the winter months. Average tree density was 95 trees per ha and the average age of the trees was 20 years with no tillage between the trees at both sites. Approximately 9,000 kg/ha of turkey or chicken manure were applied to the organic orchards in March, while 680 kg/ha of the synthetic fertilizer ammonium sulfate were applied in form of a granular material to the conventional orchards in April and June (Table 1). Approximately 14 kg/ha of copper hydroxide per year were applied by helicopter to the organic orchards as a bacteriocide to control walnut blight, Xanthomonas campestris pv. juglandis. The conventional orchards used 11 kg/ha of copper hydroxide annually according to the pesticide use report data. Additionally, Spinosad®, derived from a naturally occurring soil 130 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.


Figure 1. Map of all sampling sites in Solano County, California, USA. dwelling bacterium called Saccharopolyspora spinosa, was applied to the trunks and the main limbs of organic walnut trees by handgun to control walnut husk fly, Rhagoletis completa, in August. For the control of a variety of other pests, 120 kg/ha of Surround® WP (95% kaolin clay, a naturally occurring mineral) was used at the organic sites on an annual average. Two applications of chlorpyrifos (annual average of 3.26 kg a.i./ha) were reported by the conventional growers, one in July, one in August, and 0.22 kg a.i./ha of bifenthrin were applied. Less consistent were the use of paraquat (approximately 1.92 kg a.i./ha annually), oxyflurofen (0.66 kg a.i./ha annually), maneb (2.06 kg a.i./ha annually), and 2,4-D (0.59 kg a.i./ha annually) over the study period. 131 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

Table 1. Annual application of fertilizers and active ingredients of pesticides in organic and conventional walnut orchards Organic Orchardsb

Conventional Orchardsb

Time of Application

turkey or chicken manure

9,000 kg/ha (1)

-

March

ammonium sulfate

-

680 kg/ha (2)

April and June

copper hydroxide

10.80 kg a.i./ha (2)

8.50 kg a.i./ha (2)

March and April

Spinosad

0.048 kg a.i./ha (1)

-

August

114 kg a.i./ha (1)

-

August

chlorpyrifos

-

3.26 kg a.i./ha (2)

July and August

bifenthrin

-

0.22 kg a.i./ha (2)

July and August

paraquat

-

1.92 kg a.i./ha (2)

April and July

oxyflurofen

-

0.60 kg a.i./ha (2)

April and July

maneb

-

2.06 kg a.i./ha (2)

March and April

-

0.59 kg a.i./ha (2)

April and July

Application


Fertilizer:

Pesticides:

Surround WP a

2,4-D a

95% Kaolin clay

b

(*) number of applications per year

Water and sediment samples were collected from the soft-bottom, tail ditches of five orchards. Tail ditches were at least partially covered with cover crops at the organic sites but not vegetated at conventional sites. Tail ditches were within 3 to 5 m from the last row of trees at all sites. Samples were collected three times during the summer growing season with flood irrigation runoff and once during the first winter storms in 2007, 2008, and 2009. Since no pesticides were applied to walnuts during the dormant season, no further storm water sampling was conducted after the first flush. Sampling times varied from 1 to 8 h after runoff started. A total of 42 water and 39 sediment samples were collected for each of the monitored pesticides over the course of the two monitored seasons, including samples for quality assurance.

Sediment Sampling Sediment sampling was conducted using a Petite Ponar grab with a surface area of 0.1 m2. The grab and all scoops, stirrers, and buckets were made of stainless steel and coated with Dykon® to make them chemically inert. Sediment sampling equipment was thoroughly cleaned (sequentially with detergent, acid, methanol, and rinsed with ultrapure water) at each sampling location prior to each sampling event (4). 132 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.


The top 5 cm of sediment were scooped in each of the grabs and placed in a bucket to provide a single composite sample for each site. Between sample grabs, the bucket was covered with aluminum foil to prevent airborne contamination. After all sediment grabs were completed, the bucket was thoroughly mixed to obtain a uniform, homogeneous mixture. Aliquots were subsequently split into 250-mL amber glass containers and kept at 4ºC for sediment and total organic carbon analyses. Water Sample Collection Water samples were collected directly from the tail ditch of each orchard. The 1-L amber glass containers were filled completely to eliminate any headspace, and care was taken to minimize exposure of samples to sunlight. Immediately after collection, the containers were closed and placed on ice in a cooler. Analytical Methods Sediment and water samples were analyzed for OP and pyrethroid pesticides. Analysis for OP pesticides included chlorpyrifos, diazinon, azinphos-methyl, dimethoate, disulfoton, malathion, methidathion, parathion, phorate, and phosmet. Analysis for pyrethroid pesticide included bifenthrin, cyfluthrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, lambda-cyhalothrin, and permethrin. OP pesticides in water were analyzed following modified EPA Methods 8140 and 8141AM (4). Analysis entailed liquid-liquid extraction and GC with a Flame Photometric Detector (FPD) in phosphorus mode and Thermionic Bead Specific Detector (TSD). OP pesticides in sediment were analyzed using EPA Method 8141AM with FPD on phosphorus mode and/or TSD. The method detection limit (MDL) and reporting limit (RL) for OP pesticides in water samples were 0.005 µg/L and 0.02 µg/L, respectively; and 2.0 ng/g and 5.0 ng/g, respectively, for sediment samples. Pyrethroids in water were analyzed following modified EPA Method 8081A using liquid-liquid extraction and GC with electron capture detection and GC-MS with an ion trap detector for confirmation. Pyrethroids in sediment were analyzed using a modified EPA Method 8081BM. Dual column GC was used with electron capture. For the majority of pyrethroids in water the MDL and RL were 0.002 µg/L and 0.004 µg/L, respectively. Bifenthrin, esfenvalerate, and lambda-cyhalothrin had a MDL and RL of 0.001 µg/L and 0.002 µg/L, respectively. In sediment samples, the MDLs were between 0.5 ng/g (bifenthrin) and 2.0 ng/g (cyfluthrin, cypermethrin, deltamethrin) and the RLs were between 1.0 ng/g and 4.0 ng/g. Relative percent differences (RPDs), calculated as the difference in concentration of a pair of analytical duplicates divided by the average of the duplicates, were within the target range of +/-25%, with the only exception of chlorpyrifos in sediment for which one RPD was 36%. Percent recoveries for laboratory control were predominantly within the range of 75-125%. No pesticides were detected in the method blank quality assurance samples. Also, all field blank samples were below the method detection limit for all pesticides. For 133 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

the calculation of average concentrations non-detectable results were included as zeros.


Results and Discussion Chlorpyrifos concentrations ranged from below the 0.005 µg/L MDL to 0.840 µg/L at the conventional sites with an average chlorpyrifos concentration of 0.125 µg/L (n = 15) (Figure 2). At the organic sites, concentrations ranged from below the MDL to 0.140 µg/L with an average of 0.020 µg/L (n = 19), even though no chlorpyrifos had been applied for at least 10 years. In comparison to the freshwater acute criterion maximum concentration (CMC) (5) for chlorpyrifos of 0.025 µg/L and the chronic criterion continuous concentration (CCC) of 0.015 µg/L the low concentrations at the organic sites may pose a risk to aquatic life.

Figure 2. Chlorpyrifos concentrations at organic and conventional sites in µg/L. Average concentrations were not statistically significantly different (p = 0.05, t-test). Sampling dates were Feb 2007 (1), Jun 2007 (2), Aug 2007 (3), Sep 2007 (4), Dec 2007 (5), Apr 2008 (6), Jul 2008 (7), Jul 2008 (8), Aug 2008 (9), Aug 2008 (9), Aug 2008 (10), Nov 2008 (11), Nov 2008 (12). Even though the monitored organic walnut orchards have been certified organic for approximately 10 years and part of an all-organic operation with no synthetic pesticides being used, results of this study suggest synthetic pesticides are still present. There are several possible explanations for this observation. Pesticides could be entering the orchard with contaminated irrigation water (6), spray drift during aerial or ground pesticide applications in neighboring orchards (7), or transport of contaminated dust particles. 134 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.


Diazinon concentrations (Figure 3) with both practices were below the CMC and the CCC of 0.16 and 0.10 µg/L (5), respectively. Diazinon ranged from below the 0.005 µg/L MDL to 0.014 µg/L at the conventional sites with an average concentration of 0.002 µg/L. The average concentration at the organic sites was 0.001 µg/L, ranging from below the MDL to 0.01 µg/L. Similar to chlorpyrifos, no statistically significant difference between walnut growing practices was observed (p > 0.05).

Figure 3. Diazinon concentrations at organic and conventional sites in µg/L. Average concentrations were not statistically significantly different (p = 0.1, t-test). Sampling dates were Feb 2007 (1), Jun 2007 (2), Aug 2007 (3), Sep 2007 (4), Dec 2007 (5), Apr 2008 (6), Jul 2008 (7), Jul 2008 (8), Aug 2008 (9), Aug 2008 (9), Aug 2008 (10), Nov 2008 (11), Nov 2008 (12). Low concentrations of dimethoate (0.38 to 0.42 µg/L), another OP pesticide, were detected at the conventional sites, while all results at the organic sites were below the 0.03 µg/L MDL. The average concentration at the conventional sites was 0.41 µg/L and far below aquatic life benchmarks for fish (620 µg/L) and for invertebrates (4.3 µg/L) (8). Concentrations of lambda-cyhalothrin in water also showed no significant difference related to growing practices. Surprisingly, the highest concentration found in water during this study was at an organic site (0.02 µg/L). Average concentrations were still slightly higher at the conventional sites (0.002 µg/L) compared to the organic sites (0.001 µg/L). Pyrethroid aerial concentrations decline much faster after applications than those of OP pesticides but they are still transported and re-deposited with dust particles for a long time (half-life of 135 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.


up to 44 days) (9, 10); this may explain the occurrence of lambda-cyhalothrin at the organic site if a neighboring field/orchard was treated with pyrethroids. The pyrethroid esfenvalerate was detected in some conventional water samples with an average concentration of 0.012 µg/L, while all organic samples were below the 0.001 µg/L MDL. The average conventional concentration was above the benchmark for fish (0.007 µg/L) and for invertebrates (0.005 µg/L). Pyrethroid concentrations in sediment exhibited the only significant difference between the growing practices. Bifenthrin concentrations in sediment ranged from below the 0.5 ng/g MDL to 24 ng/g at the conventional sites (averaging 5.61 ng/g). The average concentration for the organic sites was 0.44 ng/g, ranging from below the MDL to 8.52 ng/g. The difference between the two site types was significant (p = 0.002, t-test). Since pyrethroid bioavailability is highly dependent on carbon content, pyrethroid sediment concentrations were carbon-normalized (Figure 4) for a more ecologically relevant assessment. The LC50 for Hyalella for bifenthrin is 0.52 µg/g OC (1). Three out of 16 conventional samples had bifenthrin concentrations above the LC50, indicating a potential risk for sensitive species at the conventional sites. None of the 19 samples at the organic sites were above that toxicity threshold. The LC50 for lambda-cyhalothrin is 0.45 µg/g OC (1) and all conventional and organic sediment samples in this study were below this value.

Figure 4. Bifenthrin and lambda-cyhalothrin concentrations in µg/g TOC at organic (black symbols) and conventional (white symbols) sites. The solid line shows the LC50 for Hyalella for bifenthrin of 0.52 µg/g OC published by Amweg et al. (1). The dotted line shows the toxicity threshold for lambda-cyhalothrin of 0.45 µg/g OC with all samples being below the LC50 for Hyalella toxicity (1). 136 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.


The conventional walnut growers, whose runoff was monitored in this study, were very open to best management practices (e.g., biological control) and pesticide reduction. Ideally, runoff from growers that are more dependent on pesticide usage would have been sampled but those farmers did not agree to participate in this study. The low pesticide usage at the conventional sites examined in this study resulted in few appreciable differences in pesticide concentrations between the different growing practices.

Conclusion The chemical concentrations detected at the conventional sites, especially for chlorpyrifos and lambda-cyhalothrin in water samples and bifenthrin in sediment samples were above the aquatic life criteria. However, only bifenthrin concentrations were statistically significantly higher at the conventional orchards. Although diazinon, dimethoate, and esfenvalerate concentrations were higher at the conventional sites compared to the organic orchards, the difference was not statistically significant. In general, this study indicated that the risk of harmful environmental effects is lower with organic than with conventional growing practices. Even though organic growers did not use the synthetic pesticides that were monitored during the study, the water and sediment samples collected from the organic orchards were not pesticide free. Some of the samples at the organic sites even were slightly higher than the aquatic life criteria. The data from this study suggest that additional controls or more careful management practices in neighboring conventional orchards are needed to prevent pesticide contamination of organic orchards.

Acknowledgments This project was funded by the California State Water Resources Control Board and the authors would like to thank Ahmad Kashkoli leading this Project as Grant Manager. We thank Alicia Gilbreath and Kat Ridolfi for field data collection and Cathy Holden, Cindy Lashbrook, Ben Greenfield, Jay Davis, and Lester McKee for review comments. Dave Crane, Abdou Mekebri, and Patty Brucknell managed the laboratory analysis. The author would also like to thank Craig McNamara, Russ Lester, and Joe Martinez for their knowledge and support with all aspects of the sample collection. This document has been reviewed in accordance with U.S. EPA policy and approved for publication. Approval does not signify that the contents necessarily reflect the views or policies of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

137 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

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Amweg, E. L.; Weston, D. P.; Ureda, N. M. Use and toxicity of pyrethroid pesticides in the Central Valley, California, USA. Environ. Toxicol. Chem. 2005, 24 (4), 966–972. 2. Pereira, W. E.; Domagalski, J. L.; Hostettler, F. D.; Brown, L. R.; Rapp, J. B. Occurrence and accumulation of pesticides and organic contaminants in river sediment, water and clam tissues from the San Joaquin River and tributaries, California. Environ. Toxicol. Chem. 1999, 15 (2), 172–180. 3. SWRCB. Approving an Amendment to the Water Quality Control Plan for the Sacramento River and San Joaquin River Basins (Basin Plan) for the Control of Diazinon and Chlorpyrifos Runoff into the Sacramento and Feather Rivers; Resolution No. 2008-0013; Sacramento, CA, USA, 2008. 4. David, N.; Yee, D. Quality Assurance and Project Plan for the Going Organic Project; San Francisco Estuary Institute: Oakland, CA, USA, 2007. 5. CVRWQCB. Basin Plan Amendments to the Water Quality Control Plan for the Sacramento River and San Joaquin River Basins for the Control of Diazinon and Chlorpyrifos Runoff into the Sacramento and Feather Rivers; May 2007 Final Staff Report, 2007. 6. USGS. Pesticides in Storm Runoff from Agricultural and Urban Areas in the Tuolumne River Basin in the Vicinity of Modesto, California; Water Resources Investigations Report 98-4017; Sacramento, CA, USA, 1998. 7. Owens, K.; Feldman, J. Getting the Drift on Chemical Trespass. Pesticides and You 2004, 24 (2), 16–21. 8. USEPA. Office of Pesticide Programs’ Aquatic Life Benchmarks. http:// www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm, 2011. 9. Berger-Preiess, E.; Preiess, A.; Sielaff, K.; Raabe, M.; Ilgen, B.; Levsen, K. The Behavior of Pyrethroids Indoors: A Model Study. Indoor Air 1997, 7 (4), 248–262. 10. Gassner, B.; Wuethrich, A.; Lis, J.; Scholtyzik, G.; Solioz, M. Topical application of synthetic pyrethroids to cattle as a source of persistent environmental contamination. J. Environ. Sci. Health, Part B 1997, 2 (5), 729–739.

138 In Pesticide Mitigation Strategies for Surface Water Quality; Goh, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

Comparison of Pesticide Runoff from Organic and ... - ACS Publications

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