Sean M. Stout | USGS Science

USGS2018

Dissolved pesticide concentrations in the lower Sacramento River and its source waters, California, 2016

As part of a collaborative study designed to better understand water-quality conditions in the Sacramento River, surface-water samples were collected from the lower Sacramento River and five of its tributaries and then analyzed by the U.S. Geological Survey for a suite of 162 current-use pesticides and pesticide degradates. Samples were collected in May and October 2016 at 16 sites on the Sacramento River and its tributaries. Samples were analyzed for pesticide concentrations by using gas chromatography with mass spectrometry and liquid chromatography with tandem mass spectrometry laboratory methods. A total of 27 pesticides and pesticide degradates were detected in the water samples collected during the study (12 herbicides, 9 insecticides, 5 fungicides, and 1 synergist). Two herbicides were detected in the suspended sediments filtered from the water samples. Pesticides were detected in 100 percent of the water samples, and mixtures of two or more pesticides were detected at all sites and in all but four samples. The pesticides detected most frequently in the May and October sampling periods were the herbicides hexazinone (detected in 88 percent of the water samples), and diuron (84 percent), and the fungicide azoxystrobin (84 percent). Pesticide concentrations ranged from below the method detection limits to 576 nanograms per liter (clomazone). All pesticides were detected at concentration levels lower than the U.S. Environmental Protection Agency’s aquatic life benchmarks (U.S. Environmental Protection Agency, 2017). During the May sampling period, the fungicides boscalid and azoxystrobin (both 94 percent); the herbicides clomazone, diuron, and hexazinone (all 94 percent); thiobencarb (88 percent); and metolachlor (81 percent) were the most frequently detected compounds. During the October sampling period, the herbicides hexazinone (81 percent) and diuron (75 percent) and the herbicide degradates 3,4-dichloroaniline (75 percent) and N-3,4-dichlorophenyl-N-methyl-urea (50 percent), along with the fungicide azoxystrobin (75 percent) and the insecticide methoxyfenozide (63 percent), were the most frequently detected compounds.

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USGS2018

An initial comparison of pesticides and amphibian pathogens between natural and created wetlands in the New Jersey Pinelands, 2014–16

A study conducted by the U.S. Geological Survey, in cooperation with the New Jersey Pinelands Commission and Montclair State University, was designed to compare pesticide concentrations and the presence and prevalence of amphibian pathogens between natural ponds and two types of created wetlands, excavated ponds and stormwater basins, throughout the New Jersey Pinelands. The study described herein is part of a larger study by the New Jersey Pinelands Commission designed to compare the functional equivalency of natural and created wetlands throughout the New Jersey Pinelands. Sites were selected on the basis of land-use classifications within a 500-meter radius around each wetland from a pool of natural ponds, excavated ponds, and stormwater basins determined by the New Jersey Pinelands Commission. Water, bed-sediment, anuran-food, and composite larval-anuran-tissue samples were collected from four reference (minimum land-use effects) and four degraded (maximum land-use effects) sites from each wetland type for a total of 24 ponds or basins throughout the New Jersey Pinelands during 2014–16. Prevalence of Ranavirus was determined on the basis of tail clips collected from 60 individual larval anurans in each wetland, and 10 animals from each wetland also were swabbed for the presence of Batrachochytrium dendrobatidis (Bd). Other constituents measured included turbidity, pH, specific conductance, dissolved oxygen, dissolved organic carbon, percent organic carbon in sediment, and composite larval-anuran lipid content. The amount of altered land (percent agricultural plus percent developed) ranged from 0 to 62.4 percent for the natural ponds, 0 to 63.6 percent for the excavated ponds, and 23.3 to 80.2 percent for the stormwater basins. The herbicides atrazine and metolachlor were observed in 60 and 89 percent of the water samples, respectively. The insecticide bifenthrin was the most frequently detected current-use pesticide (greater than 25 percent of the samples) in bed-sediment, anuran-food, and composite larval-anuran-tissue samples. The legacy insecticide p,p' -DDT and its primary degradates p,p' -DDD and p,p' -DDE were the most frequently detected compounds in bed-sediment and anuran-food samples (32–76 percent in sediment samples and 24–72 percent in anuran-food samples). Significantly, greater numbers of pesticides and higher total pesticide concentrations were observed in stormwater basins than in natural and excavated ponds. Reference wetlands had fewer pesticides and lower total pesticide concentrations compared to degraded wetlands, indicating a positive relation between percent altered land and pesticides throughout the New Jersey Pinelands. Ranavirus was observed in larvae from 4 wetlands, including 1 reference natural pond, 1 degraded natural pond, and 2 degraded stormwater basins, with prevalence ranging from 3 to 43 percent. Bd was detected in swabs from 18 animals and in 4 natural ponds (1 reference and 3 degraded), 3 excavated ponds (all reference), and 2 stormwater basins (1 reference and 1 degraded); however, detection probability was low. In the wetlands with Bd detections, between 10 and 30 percent (between 1 and 3) of the animal’s swabbed tested positive for Bd. Owing to the limited number of positive detections for both Bd and Ranavirus , no statistical comparisons between wetland types and land-use classifications were possible.

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