Contamination and toxicity in streambed sediments caused by pyrethroid insecticides generally increased with the degree of urbanization in this stream (Mill Creek in Salt Lake City, Utah) and six other metropolitan areas across the Nation. Photo credit: Alan Cressler, USGS.

USGS scientist uses a very sensitive instrument to measure concentrations of pyrethroid insecticides in sediments. By comparing chemical concentrations to toxicity measured in laboratory tests, USGS scientists can show that pyrethroids are likely a major cause of the observed toxicity in streams.

Estimated 2002 annual use rate for the fungicide azoxystrobin, and the maximum observed concentration of azoxystrobin in stream-water samples collected in 2005 and 2006.

The 2002 average annual agricultural use of chlorothalonil in the southeastern United Sates (based on National 2002 Pesticide Use Maps). Chlorothalonil is an agricultural fungicide widely used on peanuts, potatoes, and other crops.

The shore crab, Hemigrapsus oregonensis, collected from a rocky cove near Bodega Bay, California. These crabs are reproductively active during the summer months and carry hundreds of embryos under their carapace until hatching occurs. Scientists found crab embryos from the bay's salt marsh with accumulations of mixtures of currently used and discontinued pesticides.

USGS scientist collecting sand crabs for analysis from an urban estuary near Richmond, California. Crabs utilize these rocky intertidal areas as breeding grounds. Scientists detected pyrethroid insecticides as well as 21 other pesticides, including DDT, in crab embryos.

Aerial spraying of fungicides on row crops in Iowa. A soybean field is in the foreground, and a cornfield is in the background. The soybean crop is the target of the aerial application. Fungicides are used to combat soybean rust, a fungal disease, and have been detected in streams in areas of application.

USGS scientist lifting a filter caked with sediment that's on top of a filter plate used for filtering suspended sediment from water samples. The filter was saved for later analysis for pyrethroid insecticides in the sediment. USGS scientists have developed a method to determine the concentration of a suite of pyrethroid insecticides absorbed to sediment particles.

USGS scientists have developed a method to detect chlorothalonil (a fungicide) and three of its environmental degradates in sediment and soil. After the target compounds are extracted from the sediment the samples are analyzed by gas chromatography/mass spectrometry (GC/MS). Chlorothalonil is widely used on peanut crops.

USGS studied the transport and fate of pyrethroid insecticides absorbed on sediment in streams in the Carpinteria Marsh, Calif. USGS scientists collected bed sediments at different depths in the channel to account for tidal inundation cycles.

USGS scientists use cone splitters, such as this one on board a research vessel, to separate a water sample into several subsamples. Each subsample will be analyzed for a different suite of organic chemicals such as pyrethroid insecticides and other pesticides. The water sample being collected here is from the San Francisco Bay, Calif., near Mallard Island.

USGS scientist operating a grab sampler to collect bottom sediment from the Salton Sea, Calif. The sediment sample was analyzed for pyrethroid insecticides as part of a study of the occurrence and distribution of pyrethroids in California.