A novel U.S. Geological Survey-developed active water sampler was deployed at Ulatis Creek in Solano County, California for 24 hours from November 15, 2023 to November 16, 2023. Discrete surface water samples were collected at the start and end points of the active water sampler deployment interval for comparison to the active water sampler. Samples from the active water sampler and the discrete surface water samples were analyzed for 183 pesticides dissolved in water and 178 pesticides in suspended sediment at the U.S. Geological Survey Organic Chemistry Research Laboratory in Sacramento, California. Twenty-seven out of 183 pesticide compounds measured in sample extracts were detected in at least one of the grab sample or active sampler dissolved water extracts with concentrations ranging from 0.9 nanograms per liter to 32.2 nanograms per liter. No pesticides were detected in the suspended sediment filtered from the water.

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).

This Data release presents results for pesticide constituents in 460 samples collected from domestic and public-supply wells in August 2013-May 2018 for the California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). The samples were analyzed for 225 pesticide constituents on USGS National Water Quality Laboratory analytical schedule 2437. Results from quality-control samples collected with the environmental samples and results from laboratory quality-control samples were used to re-process the data to meet project data-quality objectives. The data release includes the final approved results tabulated by result and by sample, the original and final values for results affected by the quality-control re-processing, ancillary and summary information about the pesticide constituents, and results from field replicate and field blank samples.

This Data release presents results for pesticide constituents in 460 samples collected from domestic and public-supply wells in August 2013-May 2018 for the California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP). The samples were analyzed for 225 pesticide constituents on USGS National Water Quality Laboratory analytical schedule 2437. Results from quality-control samples collected with the environmental samples and results from laboratory quality-control samples were used to re-process the data to meet project data-quality objectives. The data release includes the final approved results tabulated by result and by sample, the original and final values for results affected by the quality-control re-processing, ancillary and summary information about the pesticide constituents, and results from field replicate and field blank samples.

The U.S. Geological Survey (USGS) deployed passive samplers at surface-water and groundwater sites on the Hawaiian Islands of Kauaʻi, Oʻahu, Maui, and Hawaiʻi for several weeks each during 2015–19. The passive samplers were deployed to assess the occurrence of pesticides and pesticide degradates, herein referred to as pesticides, in water at the sites. Some of the passive samplers were also used to assess the occurrence of additional organic contaminants and wastewater indicators in water at the sites. This dataset includes files with chemical results for the passive samplers. The chemical results include masses of pesticides that accumulated in the passive samplers and concentration values that represent the average concentrations of chemicals in water during the deployment of a passive sampler at a site. The data release includes five files. The first file (1_passive-sampler_sites.csv) contains information for each passive sampler that was deployed in water. The second file (2_pesticide_masses_POCIS.csv) contains mass values of pesticides that accumulated in polar-organic-chemical-integrative sampler (POCIS) units of passive samplers. The third file (3_pesticide_concentrations_POCIS.csv) contains concentration values of selected pesticides that accumulated in POCIS units of passive samplers. The fourth file (4_organic_contaminants_SPMD.csv) contains concentration values for organic contaminants that accumulated in semipermeable-membrane-device (SPMD) units of passive samplers. The organic contaminants include organochlorine pesticides, polybrominated diphenyl ether residues, total polychlorinated biphenyl residues, and polycyclic aromatic hydrocarbon residues. The fifth file (5_wastewater_indicators_POCIS.csv) contains results for pharmaceutical compounds and organic waste compounds that accumulated in the POCIS units of the passive samplers. The third file includes water-quality standards and benchmarks established by the State of Hawaiʻi, the U.S. Environmental Protection Agency, and USGS. The USGS National Water Quality Laboratory (NWQL) determined the occurrence of pesticides and pharmaceutical compounds in POCIS units of passive samplers. The USGS Columbia Environmental Research Center (CERC) determined the occurrence of organic contaminants in SPMD units of passive samplers and determined the occurrence of organic waste compounds in POCIS units of the passive samplers.

The U.S. Geological Survey (USGS) deployed passive samplers at surface-water and groundwater sites on the Hawaiian Islands of Kauaʻi, Oʻahu, Maui, and Hawaiʻi for several weeks each during 2015–19. The passive samplers were deployed to assess the occurrence of pesticides and pesticide degradates, herein referred to as pesticides, in water at the sites. Some of the passive samplers were also used to assess the occurrence of additional organic contaminants and wastewater indicators in water at the sites. This dataset includes files with chemical results for the passive samplers. The chemical results include masses of pesticides that accumulated in the passive samplers and concentration values that represent the average concentrations of chemicals in water during the deployment of a passive sampler at a site. The data release includes five files. The first file (1_passive-sampler_sites.csv) contains information for each passive sampler that was deployed in water. The second file (2_pesticide_masses_POCIS.csv) contains mass values of pesticides that accumulated in polar-organic-chemical-integrative sampler (POCIS) units of passive samplers. The third file (3_pesticide_concentrations_POCIS.csv) contains concentration values of selected pesticides that accumulated in POCIS units of passive samplers. The fourth file (4_organic_contaminants_SPMD.csv) contains concentration values for organic contaminants that accumulated in semipermeable-membrane-device (SPMD) units of passive samplers. The organic contaminants include organochlorine pesticides, polybrominated diphenyl ether residues, total polychlorinated biphenyl residues, and polycyclic aromatic hydrocarbon residues. The fifth file (5_wastewater_indicators_POCIS.csv) contains results for pharmaceutical compounds and organic waste compounds that accumulated in the POCIS units of the passive samplers. The third file includes water-quality standards and benchmarks established by the State of Hawaiʻi, the U.S. Environmental Protection Agency, and USGS. The USGS National Water Quality Laboratory (NWQL) determined the occurrence of pesticides and pharmaceutical compounds in POCIS units of passive samplers. The USGS Columbia Environmental Research Center (CERC) determined the occurrence of organic contaminants in SPMD units of passive samplers and determined the occurrence of organic waste compounds in POCIS units of the passive samplers.

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.

Dissolved pesticides were measured in weekly water samples from 85 wadeable streams in Central Coastal California over a variable six-week period during March–May, 2017, as part of the California Stream Quality Assessment (CSQA) study conducted by the U.S. Geological Survey's (USGS) Regional Stream-Quality Assessment (RSQA) Project. The 85 streams consisted of 40 urban sites (5–100% urban land in the lower basin), 9 agricultural sites, 24 mixed land-use sites, and 12 undeveloped sites. Water samples were filtered (0.7 micrometers) and analyzed for 253 pesticide compounds by direct-injection liquid chromatography with tandem mass-spectrometry (LC-MS/MS). Two similar LC-MS/MS methods were used: a broad-spectrum (223 compounds) method in use since 2012 and a newly developed method for 30 new-generation fungicides and diamide and neonicotinoid insecticides. This Data Release provides sampling-site locations, analyte information, concentration data for pesticide compounds in environmental weekly water samples, quality-control data for the new method (to supplement previously published quality control data for the standard method), aquatic-life benchmark and Pesticide Toxicity Index toxicity concentration values that were used to assess potential toxicity, estimates of agricultural and nonagricultural pesticide-use data, and streamflow data for gaged sites, in support of the journal article, “New-generation pesticides are prevalent in California’s Central Coast streams,” by Sandstrom, M.W., Nowell, L.H., Mahler, B.J., and Van Metre, P.C.