Urban pesticide use has a direct impact on surface water quality. To determine the extent of pesticide contamination, the California Department of Pesticide Regulation initiated a multi-area urban monitoring program in 2008. Water and sediment samples were collected at sites unaffected by agricultural inputs in three areas: Sacramento (SAC), San Francisco Bay (SFB), and Orange County (OC). Samples were analyzed for up to 64 pesticides or degradates. Multiple detections were common; 50 % of the water samples contained five or more pesticides. Statewide, the most frequently detected insecticides in water were bifenthrin, imidacloprid, fipronil, fipronil sulfone, fipronil desulfinyl, carbaryl, and malathion. Bifenthrin was the most common contaminant in sediment samples. Key differences by area: OC had more pesticides detected than SAC or SFB with higher concentrations of fipronil, whereas SAC had higher concentrations of bifenthrin. The most frequently detected herbicides were 2,4-D, triclopyr, dicamba, diuron, and pendimethalin. Key differences by area: OC and SFB had higher concentrations of triclopyr, whereas SAC had higher concentrations of 2,4-D and dicamba. Detection frequency, number of pesticides per sample, and pesticide concentration increased during rainstorm events. In water samples, all of the bifenthrin, malathion, fipronil, permethrin, and λ-cyhalothrin detections, and most of the fipronil sulfone and cyfluthrin detections were above their lowest US EPA aquatic benchmark. Diuron was the only herbicide that was detected above its lowest benchmark. Based on the number of pesticides and exceedances of aquatic benchmarks or the high number of sediment toxicity units, pesticides are abundant in California surface waters.

The phenylpyrazole insecticide fipronil has become a popular replacement pest management tool as organophosphorus insecticides have been phased out for residential use and pyrethroids have come under scrutiny as a surface water contaminant. There has been an increasing concern of offsite transport of fipronil to surrounding surface waters and a corresponding increase in potential toxicity to aquatic organisms. The California Department of Pesticide Regulation Environmental Monitoring Program has collected over 500 urban surface water samples throughout California since 2008 to determine the presence and concentrations of fipronil and five degradate products. Statewide, fipronil was detected at high frequency (49%), as were the sulfone (43%) and desulfinyl (33%) degradates. Data collected at long-term monitoring stations indicate higher concentrations in southern California, corresponding to a higher use pattern in the region. There is a clear pattern of increased transport of fipronil with higher flow associated with rain events. However, the lack of seasonality effects on degradates' concentrations suggest a constant source of fipronil with a corresponding lag time of transport to surface waters during the dry season. Receiving waters had a diluting effect on concentrations; however, a significant proportion (46%) of receiving water samples had associated fipronil concentrations above USEPA aquatic life chronic benchmark values. Total mass loading estimates from a long-term monitoring site suggest that the annual fipronil loading is greater in the dry season than during storm events. This could have implications for future mitigation efforts because most runoff during this period was generated from irrigation and outdoor residential use.

The California's San Joaquin River and its tributaries including Orestimba (ORC) and Del Puerto (DPC) Creeks are listed on the 2006 US EPA Clean Water Act §303(d) list for pesticide impairment. From December 2007 through June 2008, water and sediment samples were collected from both creeks in Stanislaus County to determine concentrations of organophosphorus (OP) and pyrethroid insecticides and to identify toxicity to Ceriodaphnia dubia and Hyalella azteca. OPs were detected in almost half (10 of 21) of the water samples, at concentrations from 0.005 to 0.912 μg L(-1). Diazinon was the most frequently detected OP, followed by chlorpyrifos and dimethoate. Two water samples were toxic to C. dubia; based on median lethal concentrations (LC50), chlorpyrifos was likely the cause of this toxicity. Pyrethroids were detected more frequently in sediment samples (18 detections) than in water samples (three detections). Pyrethroid concentrations in water samples ranged from 0.005 to 0.021 μg L(-1). These concentrations were well below reported C. dubia LC50s, and toxicity was not observed in laboratory bioassays. Cyfluthrin, bifenthrin, esfenvalerate, and λ-cyhalothrin were detected in sediment samples at concentrations ranging from 1.0 to 74.4 ng g(-1), dry weight. At DPC, all but one sediment sample caused 100% toxicity to H. azteca. Based on estimated toxicity units (TUs), bifenthrin was likely responsible for this toxicity and λ-cyhalothrin also contributed. At ORC, survival of H. azteca was significantly reduced in four of the 11 sediment samples. However, pyrethroids were detected in only two of these samples. Based on TUs, bifenthrin and λ-cyhalothrin likely contributed to the toxicity.

ABSTRACIPhotosynthesis is not required for the toxicity of diphenyl ether herbicides, nor are chloroplast thylakoids the primary site of diphenyl ether herbicide activity. Isolated spinach (Spinacia oleracea L.) chloroplast fragments produced malonyl dialdehyde, indicating lipid peroxidation, when paraquat (1,1'-dimethyl4,4'-bipyridinium ion) or diuron 13-(3,4-dichlorophenyl)-I,I-dimethylureaI were added to the medium, but no malonyl dialdehyde was produced when chloroplast fragments were treated with the methyl ester of acifluorfen (methyl 5-12-chloro-4-(trifluoromethyl)phenoxy-2-nitrobenzoic acid), oxyfluorfen 12-chloro-l-(3-ethoxy4-nitrophenoxy)4-(trifluoromethyl)benzenel, or MC15608(methyl 5-12-chloro44trifluoromethyl)phenoxyj2-chlorobenzoate). In most cases the toxicity of acifluorfen-methyl, oxyfluorfen, or MC15608 to the unicellular green alga Chiamydomonas eugametos (Moewus) did not decrease after simultaneous treatment with diuron. However, diuron significantly reduced cell death after paraquat treatment at all but the highest paraquat concentration tested (0.1 millimolar). These data indicate electron transport of photosynthesis is not serving the same function for diphenyl ether herbicides as for paraquat. Additional evidence for differential action of paraquat was obtained from the superoxide scavenger copper penicillamine (copper complex of 2-amino-3-mercapto-3-methylbutanoic acid). Copper penicillamine eliminated paraquat toxicity in cucumber (Cucumis sativus L.) cotyledons but did not reduce diphenyl ether herbicide toxicity. DPE3 herbicides initiate lipid peroxidation and eventually disrupt cell membranes causing cell death (7,13,18 initiating lipid peroxidation of the polyunsaturated fatty acids in the membrane of Scenedesmus acutus.The purpose of this study was to determine if photosynthesis is involved in DPE herbicide membrane disruption and cell death as it is for cell death by paraquat and diuron (5). This research used isolated spinach chloroplast fragments, the unicellular green alga Chlamydomonas, and excised cucumber cotyledons to evaluate the requirement of photosynthesis for DPE caused cell death. MATERIALS AND METHODSIsolated Chloroplast Fragments. Spinach chloroplast fragments were prepared by the method ofTakahama (24) with some modification. Large veins were removed from 25 to 30 g of commercially grown spinach leaves, and then the leaves were cut into 1 cm2 pieces. Leaf pieces were blended 30 s in a Waring Blendor with 125 ml of 17 mM Tris-HCI buffer (pH 7.4). The debris was filtered through eight layers of cheesecloth and centrifuged at 2000g for 1 min in a Sorvall HB-4 rotor. The supernatant was centrifuged 10,000g for 10 min, and the pellet was resuspended in 17 mm Tris -HCI buffer (pH 7.4) which was again centrifuged at 10,000g for 10 min. The chloroplast fragments in the pellet were resuspended in 17 mM Tris-HCI buffer, pH 7.4. All isolations were conducted at 4C, and Chl concentrations were determined using the absorption coefficients for Chl a and b as given by MacKinney (...

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