Relatively few studies have examined recoveries from source waters by using Environmental Protection Agency method 1623 with organism spike doses that are environmentally realistic and at turbidity levels commonly found in surface waters. In this study, we evaluated the filtration capacities and recovery efficiencies of the Gelman Envirochek (standard filter) and the Gelman Envirochek high-volume (HV) sampling capsules under environmental conditions. We also examined the performance of method 1623 under ambient conditions with matrix spike experiments using 10 organisms/liter. Under turbid conditions, the HV capsule filtered approximately twice the volume filtered by the standard filter, but neither could filter 10 liters without clogging. In low-turbidity waters, oocyst, but not cyst, recoveries were significantly higher when the HV capsule was used. In turbid waters, organism recoveries were lower than those in nonturbid waters and were not significantly different for the different filters. When the HV capsule was used, Cryptosporidium recoveries ranged from 36 to 75%, and Giardia recoveries ranged from 0.5 to 53%. For both organisms, recoveries varied significantly by site. Turbidity could explain variation in Giardia recoveries (r 2 ‫؍‬ 0.80) but not variation in Cryptosporidium recoveries (r 2 ‫؍‬ 0.16). The inconsistent recoveries across sites suggested that the background matrix of the ambient water affected recovery by method 1623. A control sample collected at the height of the winter rainy season detected one organism, highlighting the difficulty of using this method to accurately measure pathogen abundance under natural conditions. Our findings support the use of the HV filter under field conditions but suggest that designing a cost-effective and statistically valid monitoring program to evaluate sources and loads of protozoan pathogens may be difficult.Cryptosporidium and Giardia spp. are a group of protozoan parasites that can cause mild to severe diarrhea and potentially shorten the life spans of immunocompromised individuals. The importance of understanding occurrence and distribution of these parasites is magnified by their potential to infect a large population via drinking-water supplies.

We used radiocarbon measurements of dissolved organic carbon (DOC) to resolve sources of riverine carbon within agriculturally dominated landscapes in California. During 2003 and 2004, average D 14 C for DOC was -254% in agricultural drains in the Sacramento-San Joaquin Delta, -218% in the San Joaquin River, -175% in the California State Water Project and -152% in the Sacramento River.

Abstract-The U.S. Environmental Protection Agency (U.S. EPA) protocols for conducting freshwater toxicity tests have been used in California, USA, to evaluate ambient water quality since 1986. Testing evolved from conducting broad watershed surveys for assessing the distribution of toxicity to conducting detailed studies for identifying chemical causes and sources. Using Ceriodaphnia dubia tests, pulses of diazinon toxicity have been detected over a 10-year period throughout California's Central Valley in waters receiving drainage from dormant orchards. In the 1980s, toxicity to C. dubia, caused by methyl parathion and carbofuran in drainage from rice fields, was detected in the Sacramento River. Rice drainage also was toxic to two important local species, larval striped bass and Neomysis. Throughout the state, diazinon and chlorpyrifos toxicity to C. dubia occurs year-round in waters receiving drainage from urban areas. Several years of monitoring the Alamo River in Imperial County with C. dubia demonstrated a recurring seasonal toxicity pattern. Toxicity during a 3-month autumn period was caused by chlorpyrifos and diazinon and during a 2-month spring period by diazinon and carbofuran. Although most toxicity has been detected with C. dubia and linked to insecticides, other examples of toxicity have been identified. Toxicity to Selenastrum has been linked to copper and zinc from mines and to the herbicide diuron in waters receiving agricultural or urban runoff. Ammonia-caused toxicity, originating from dairies and wastewater treatment plants, to fathead minnows has also been identified. Taken together, the results reveal that the three whole effluent toxicity (WET) testing procedures, in association with toxicity identification evaluations (TIEs) and chemical analyses, can be effective for the identification of an array of toxicants originating from several land use practices. In several cases, alternative land use practices or management strategies have resulted in improved water quality as demonstrated by continued toxicity testing.

Abstract-The responses of carbofuran, diazinon, and chlorpyrifos to standard acute toxicity identification evaluation (TIE) procedures were characterized. The test species was Ceriodaphnia dubia. The TIE procedures included solid-phase extraction, recovery in methanol eluates, hydrolysis under acid and base conditions, and retention in specific methanol/water fractions. In addition, the effect of the metabolic inhibitor, piperonyl butoxide, on the toxicity of each of the pesticides was determined. Diazinon degraded quickly under acid conditions, whereas carbofuran degraded under base conditions. In both cases, concentrations were reduced to nontoxic levels within 6 h. Conversely, acidic or basic conditions were not effective in reducing the concentration of chlorpyrifos over the same time period. Solid-phase extraction removed at least 95% of diazinon and carbofuran from solution, but was less effective with chlorpyrifos. All three pesticides eluted separately in characteristic methanol/water fractions. Piperonyl butoxide ameliorated the toxicity of diazinon and chlorpyrifos, but not carbofuran. Up to 1.5% methanol did not interfere with the protective action of piperonyl butoxide. Case studies in which these techniques were applied to ambient water samples are also described.

The responses of carbofuran, diazinon, and chlorpyrifos to standard acute toxicity identification evaluation (TIE) procedures were characterized. The test species was Ceriodaphnia dubia. The TIE procedures included solid‐phase extraction, recovery in methanol eluates, hydrolysis under acid and base conditions, and retention in specific methanol/water fractions. In addition, the effect of the metabolic inhibitor, piperonyl butoxide, on the toxicity of each of the pesticides was determined. Diazinon degraded quickly under acid conditions, whereas carbofuran degraded under base conditions. In both cases, concentrations were reduced to nontoxic levels within 6 h. Conversely, acidic or basic conditions were not effective in reducing the concentration of chlorpyrifos over the same time period. Solid‐phase extraction removed at least 95% of diazinon and carbofuran from solution, but was less effective with chlorpyrifos. All three pesticides eluted separately in characteristic methanol/water fractions. Piperonyl butoxide ameliorated the toxicity of diazinon and chlorpyrifos, but not carbofuran. Up to 1.5% methanol did not interfere with the protective action of piperonyl butoxide. Case studies in which these techniques were applied to ambient water samples are also described.