Zooplankton samples were collected at one site upstream of the Yolo Bypass in Northern California, three sites within the Bypass, and at a comparison site on the Sacramento River below the city of Sacramento and analyzed for a large suite of current-use pesticides and degradates. Samples were collected every two weeks from early August 2021 to mid-October 2021. Samples were collected by towing a 150-micron conical plankton net for 5 minutes by boat at each site. In the laboratory, zooplankton samples were filtered through a 63-micrometer sieve to separate the zooplankton and vegetation/detritus from the water. Large sticks, twigs, rocks, and leaves were rinsed with organic free water into the sieve and then discarded. The remaining mass in the sieve was transferred into 50 milliliter plastic centrifuge tubes, frozen overnight at -20 degrees Celsius, dehydrated completely using a freeze dryer, and then stored at -20 degrees Celsius. Immediately prior to analysis, each freeze-dried sample was homogenized and sub-sampled to a targeted final weight of 0.5 grams. Sub-samples were further homogenized with magnesium sulfate and extracted with acetonitrile at 100 degrees Celsius using an EDGE Automated Extraction System. Extracts were cleaned up using activated carbon and evaporated to 200 microliters in acetonitrile. Each sample had internal standards added, and was analyzed by gas chromatography-tandem mass spectrometry for 29 pesticides and by liquid chromatography tandem mass spectrometry for 137 pesticides. A total of 18 pesticides were detected in the zooplankton samples, and 25 of the 31 samples collected contained multiple pesticides (maximum of 12 per sample). The most frequently detected compounds in zooplankton were azoxystrobin, bifenthrin, fluridone, p,p’-DDD, p,p’-DDE, permethrin, and thiobencarb.

Zooplankton samples were collected at one site upstream of the Yolo Bypass in Northern California, three sites within the Bypass, and at a comparison site on the Sacramento River below the city of Sacramento and analyzed for a large suite of current-use pesticides and degradates. Samples were collected every two weeks from early August 2021 to mid-October 2021. Samples were collected by towing a 150-micron conical plankton net for 5 minutes by boat at each site. In the laboratory, zooplankton samples were filtered through a 63-micrometer sieve to separate the zooplankton and vegetation/detritus from the water. Large sticks, twigs, rocks, and leaves were rinsed with organic free water into the sieve and then discarded. The remaining mass in the sieve was transferred into 50 milliliter plastic centrifuge tubes, frozen overnight at -20 degrees Celsius, dehydrated completely using a freeze dryer, and then stored at -20 degrees Celsius. Immediately prior to analysis, each freeze-dried sample was homogenized and sub-sampled to a targeted final weight of 0.5 grams. Sub-samples were further homogenized with magnesium sulfate and extracted with acetonitrile at 100 degrees Celsius using an EDGE Automated Extraction System. Extracts were cleaned up using activated carbon and evaporated to 200 microliters in acetonitrile. Each sample had internal standards added, and was analyzed by gas chromatography-tandem mass spectrometry for 29 pesticides and by liquid chromatography tandem mass spectrometry for 137 pesticides. A total of 18 pesticides were detected in the zooplankton samples, and 25 of the 31 samples collected contained multiple pesticides (maximum of 12 per sample). The most frequently detected compounds in zooplankton were azoxystrobin, bifenthrin, fluridone, p,p’-DDD, p,p’-DDE, permethrin, and thiobencarb.

Zooplankton samples were collected at a site in the Yolo Bypass in Northern California and at a comparison site on the Sacramento River below the city of Sacramento and analyzed for a large suite of current-use pesticides and degradates. Samples were collected biweekly in the summer/fall 2017 and 2018, and from May 2019−March 2020. Samples were collected by towing a 150-micron conical plankton net for 5 minutes by boat at each site. In the laboratory, zooplankton samples were filtered through a 63-micrometer sieve to separate the zooplankton and vegetation/detritus from the water. Large sticks, twigs, rocks, and leaves were rinsed with organic free water into the sieve and then discarded. The remaining mass in the sieve was transferred into 50 milliliter plastic centrifuge tubes, frozen overnight at -20 degrees celsius, dehydrated completely using a freeze dryer, and then stored at -20 degrees celsius. Immediately prior to analysis, each freeze-dried sample was homogenized and subsampled to a targeted final weight of 0.5 to 1.0 grams. Each subsample was further homogenized with sodium sulfate and extracted with dichloromethane at 100 degrees celsius and 1500 PSI using an ASE 200 solvent extraction system. Extracts were cleaned up using activated carbon, evaporated to 200 microliters in ethyl acetate, internal standards added, and analyzed by gas chromatography-tandem mass spectrometry for 86 pesticides. A total of 29 pesticides were detected in the zooplankton samples, and 70 of the 73 samples collected contained multiple pesticides (up to 17 per sample). The most frequently detected compounds in zooplankton were 3,4-dichloroanline, azoxystrobin, bifenthrin, p,p’-DDD, p,p’-DDE, pendimethalin, and thiobencarb.

Zooplankton samples were collected in the summer/fall of 2022 and 2023 at multiple sites in the Sacramento River, Yolo Bypass, and Cache Slough Region of California and analyzed for a suite of 160 current-use pesticides and pesticide degradates by the U.S. Geological Survey Organic Chemistry Research Laboratory. In 2022 samples were collected at two sites in the Bypass and at a comparison site on the Sacramento River from early August to mid-October. In 2023 zooplankton samples were collected at one site upstream of the Yolo Bypass in Northern California, four sites within the Bypass, one site downstream of the Bypass in the Cache Slough region, and at a comparison site on the Sacramento River from late July through early October. Samples were collected every two weeks by towing a 150-micron conical plankton net for 5 minutes by boat at each site. In the laboratory, zooplankton samples were filtered through a 63-micrometer sieve to separate the zooplankton and vegetation/detritus from the water. Large sticks, twigs, rocks, and leaves were rinsed with organic free water into the sieve and then discarded. The remaining mass in the sieve was transferred into 50 milliliter plastic centrifuge tubes, frozen overnight at -20 degrees Celsius, dehydrated completely using a freeze dryer, and then stored at -20 degrees Celsius. Immediately prior to analysis, each freeze-dried sample was homogenized and sub-sampled to a targeted final weight of 0.5 grams. Sub-samples were further homogenized with magnesium sulfate and extracted with acetonitrile at 100 degrees Celsius using an EDGE Automated Extraction System following procedures outlined in Black and others, (2023). Extracts were cleaned up using activated carbon and evaporated to 200 microliters in acetonitrile. Each sample had internal standards added and was analyzed by gas chromatography-tandem mass spectrometry for 27 pesticides and by liquid chromatography tandem mass spectrometry for 133 pesticides following methods described in Gross and others, (2024). A total of 15 pesticides were detected in the 18 zooplankton samples collected in 2022, and 16 of the samples contained multiple pesticides (up to 9 per sample). The most frequently detected compounds in 2022 were azoxystrobin, bifenthrin, fluridone, and p,p’-DDE. A total of 25 pesticides were detected in the 55 zooplankton samples collected in 2023, and 50 of the samples contained multiple pesticides (up to 16 per sample). The most frequently detected compounds in 2023 were azoxystrobin, bifenthrin, and p,p’-DDE.

Zooplankton samples were collected in the summer/fall of 2022 and 2023 at multiple sites in the Sacramento River, Yolo Bypass, and Cache Slough Region of California and analyzed for a suite of 160 current-use pesticides and pesticide degradates by the U.S. Geological Survey Organic Chemistry Research Laboratory. In 2022 samples were collected at two sites in the Bypass and at a comparison site on the Sacramento River from early August to mid-October. In 2023 zooplankton samples were collected at one site upstream of the Yolo Bypass in Northern California, four sites within the Bypass, one site downstream of the Bypass in the Cache Slough region, and at a comparison site on the Sacramento River from late July through early October. Samples were collected every two weeks by towing a 150-micron conical plankton net for 5 minutes by boat at each site. In the laboratory, zooplankton samples were filtered through a 63-micrometer sieve to separate the zooplankton and vegetation/detritus from the water. Large sticks, twigs, rocks, and leaves were rinsed with organic free water into the sieve and then discarded. The remaining mass in the sieve was transferred into 50 milliliter plastic centrifuge tubes, frozen overnight at -20 degrees Celsius, dehydrated completely using a freeze dryer, and then stored at -20 degrees Celsius. Immediately prior to analysis, each freeze-dried sample was homogenized and sub-sampled to a targeted final weight of 0.5 grams. Sub-samples were further homogenized with magnesium sulfate and extracted with acetonitrile at 100 degrees Celsius using an EDGE Automated Extraction System following procedures outlined in Black and others, (2023). Extracts were cleaned up using activated carbon and evaporated to 200 microliters in acetonitrile. Each sample had internal standards added and was analyzed by gas chromatography-tandem mass spectrometry for 27 pesticides and by liquid chromatography tandem mass spectrometry for 133 pesticides following methods described in Gross and others, (2024). A total of 15 pesticides were detected in the 18 zooplankton samples collected in 2022, and 16 of the samples contained multiple pesticides (up to 9 per sample). The most frequently detected compounds in 2022 were azoxystrobin, bifenthrin, fluridone, and p,p’-DDE. A total of 25 pesticides were detected in the 55 zooplankton samples collected in 2023, and 50 of the samples contained multiple pesticides (up to 16 per sample). The most frequently detected compounds in 2023 were azoxystrobin, bifenthrin, and p,p’-DDE.

Zooplankton samples were collected in the summer/fall of 2024 at multiple sites in the Sacramento River, Yolo Bypass, and Cache Slough Region of California and analyzed for a suite of 160 current-use pesticides and pesticide degradates by the U.S. Geological Survey Organic Chemistry Research Laboratory. Samples were collected at two sites in the Bypass, at a comparison site on the Sacramento River and four sites in the Cache Slough region from mid-June to mid-August. Samples were collected every two weeks by towing a 150-micron conical plankton net for 5 minutes by boat at each site. In the laboratory, zooplankton samples were filtered through a 63-micrometer sieve to separate the zooplankton and vegetation/detritus from the water. Large sticks, twigs, rocks, and leaves were rinsed with organic free water into the sieve and then discarded. The remaining mass in the sieve was transferred into 50 milliliter plastic centrifuge tubes, frozen overnight at -20 degrees Celsius, dehydrated completely using a freeze dryer, and then stored at -20 degrees Celsius. Immediately prior to analysis, each freeze-dried sample was homogenized and sub-sampled to a targeted final weight of 0.5 grams. Sub-samples were further homogenized with magnesium sulfate and extracted with acetonitrile at 100 degrees Celsius using an EDGE Automated Extraction System following procedures outlined in Black and others, 2023. Extracts were cleaned up using activated carbon and evaporated to 200 microliters in acetonitrile. Each sample had internal standards added and was analyzed by gas chromatography-tandem mass spectrometry for 27 pesticides and by liquid chromatography tandem mass spectrometry for 133 pesticides following methods described in Gross and others, 2024. A total of 14 pesticides were detected in the 35 zooplankton samples collected, and 33 of the samples contained multiple pesticides (up to 7 per sample). The most frequently detected compounds were azoxystrobin, bifenthrin, fluridone, and p,p`-DDE.

Hydrophobic (sediment-associated) pesticides were measured in sediment samples collected from 82 wadeable streams and in biofilm in 54 of those streams in the Central California Foothills and Coastal Mountains ecoregion.115 current-use and 3 legacy pesticides were measured in stream sediment; 93 of the current-use pesticides and the same 3 legacy pesticides were measured in biofilm. On average 4 times as many current-use pesticides were detected in biofilm at a site (median of 2) as in sediment (median of 0.5). This data release provides data for the pesticide concentrations, information on the pesticide compounds, and input data and R scripts for statistical models used in the analysis presented in the journal article "Biofilms provide new insight into pesticide occurrence in streams and links to aquatic ecological communities," by BJ Mahler, TS Schmidt, LH Nowell, SL Qi, PC Van Metre, ML Hladik, DM Carlisle, MD Munn, and J May, http://dx.doi.org/xxxxxxxx.

Hydrophobic (sediment-associated) pesticides were measured in sediment samples collected from 82 wadeable streams and in biofilm in 54 of those streams in the Central California Foothills and Coastal Mountains ecoregion.115 current-use and 3 legacy pesticides were measured in stream sediment; 93 of the current-use pesticides and the same 3 legacy pesticides were measured in biofilm. On average 4 times as many current-use pesticides were detected in biofilm at a site (median of 2) as in sediment (median of 0.5). This data release provides data for the pesticide concentrations, information on the pesticide compounds, and input data and R scripts for statistical models used in the analysis presented in the journal article "Biofilms provide new insight into pesticide occurrence in streams and links to aquatic ecological communities," by BJ Mahler, TS Schmidt, LH Nowell, SL Qi, PC Van Metre, ML Hladik, DM Carlisle, MD Munn, and J May, http://dx.doi.org/xxxxxxxx.

Surface water samples were collected from four stream/agricultural drain sites in the Sacramento Valley of California to measure pesticides commonly applied to rice. Samples were collected weekly from May through August 2010 to capture the rice pesticide application season. Water samples were filtered (0.7 µm) and extracted via solid-phase extraction. Additionally, the filter paper was solvent extracted to measure suspended sediment-associated pesticides. Both fractions were analyzed via gas chromatography-mass spectrometry. A total of 89 pesticides and pesticide degradates were measured in the dissolved water phase, while 14 pyrethroid insecticides were measured in the suspended sediment-associated fraction (pyrethroids are hydrophobic and known to associate with particulates). For the dissolved phase, 18 compounds were detected. The most frequently detected compounds included those pesticides applied to rice: azoxystrobin (detection frequency 100%, maximum concentration 128,000 ng/L), clomazone (96%, 19,400 ng/L), 3,4-dichloroaniline (propanil degradate; 92%, 13,600 ng/L), thiobencarb (83%, 12,400 ng/L), and propanil (57%; 6,500 ng/L). Other frequently detected dissolved pesticides not applied to rice included boscalid (45%, 75.7 ng/L) and metolachlor (43%, 600 ng/L). Only two pyrethroids were detected in the suspended sediment fraction; this included lambda-cyhalothrin (17%, 14.8 ng/L), which was applied to rice, and bifenthrin, which is not specific to rice (6%, 26.3 ng/L).

Surface water samples were collected from four stream/agricultural drain sites in the Sacramento Valley of California to measure pesticides commonly applied to rice. Samples were collected weekly from May through August 2010 to capture the rice pesticide application season. Water samples were filtered (0.7 µm) and extracted via solid-phase extraction. Additionally, the filter paper was solvent extracted to measure suspended sediment-associated pesticides. Both fractions were analyzed via gas chromatography-mass spectrometry. A total of 89 pesticides and pesticide degradates were measured in the dissolved water phase, while 14 pyrethroid insecticides were measured in the suspended sediment-associated fraction (pyrethroids are hydrophobic and known to associate with particulates). For the dissolved phase, 18 compounds were detected. The most frequently detected compounds included those pesticides applied to rice: azoxystrobin (detection frequency 100%, maximum concentration 128,000 ng/L), clomazone (96%, 19,400 ng/L), 3,4-dichloroaniline (propanil degradate; 92%, 13,600 ng/L), thiobencarb (83%, 12,400 ng/L), and propanil (57%; 6,500 ng/L). Other frequently detected dissolved pesticides not applied to rice included boscalid (45%, 75.7 ng/L) and metolachlor (43%, 600 ng/L). Only two pyrethroids were detected in the suspended sediment fraction; this included lambda-cyhalothrin (17%, 14.8 ng/L), which was applied to rice, and bifenthrin, which is not specific to rice (6%, 26.3 ng/L).