This study examined the hypothesis that exposure to sublethal concentrations of contaminants alters the gonadal condition of feral common carp Cyprinus carpio. Adult common carp in Lake Mead, Nevada, were collected from a contaminated site (Las Vegas Bay) that receives municipal and industrial effluent and from a reference site (Overton Arm) with a relatively low level of contamination. Fish were sampled seven times over a 1-year period extending over two separate spawning seasons. Morphometric and histopathological parameters of gonadal and germ

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The occurrence of organochlorine compounds and semivolatile organic compounds was investigated at 14 sites in the Las Vegas Valley in 1997. The investigation was a cooperative effort between the U.S. Geological Survey and the Clark County Regional Flood Control District. Semipermeable membrane devices (SPMD's) were used to sample synthetic organic compounds at five surface-water sites. Bottom-sediment samples were collected at six sites in valley streams and four sites in floodwater detention basins. One of the SPMD sites also was at a bottom-sediment site. Compounds analyzed for include organochlorine pesticides and selected degradation products, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, phthalates, and phenols. Extracts from the SPMD's were analyzed and 18 organochlorine pesticides, compounds, and selected degradation products, and 7 polycyclic aromatic hydrocarbons (PAH's) were detected and quantified. Of the 81 targeted organic compounds, 56 were not detected in extracts from the SPMD's. In bottom-sediment samples, 11 organochlorine compounds, 20 PAH's, 6 phthalates, 5 phenols, and 11 other miscellaneous semivolatile organic compounds were detected. Of the 98 targeted organic compounds, 45 were not detected in bottomsediment samples from the sites. In washes downstream from urban areas in Las Vegas Valley, 51 synthetic organic compounds were detected in bottom sediment. In other bottom sediment from floodwater detention basins, which generally are upstream from urban areas, only 17 compounds were detected.

Chemical and bacteriological data were collected to describe the quality of water from selected geologic units in Routt County, Colo. Calcium bicarbona•te was the dominant water-chemistry type; magnesium, sodium, and sulfate frequently occurred as codominant ions.Specific-conductance values ranged from 50 to 6,000 micromhos. Mean values of specific conductance, dissolved solids, and hardness from the sampled aquifers were generally greatest in waters from the older sedimentary rocks of the Lance Formation, Lewis Shale, Mesaverde Group, and Mancos Shale, and least in the ground waters from the alluvial deposits, the Browns Park Formation, and the basement complex. Direct correlations of specific conductance with dissolved sol ids and specific conductance with hardness were found within specified limits.On the basis of water-quality analyses, water from the alluvial deposits, the Browns Park Formation, and the basement complex generally is the most suitable for domestic uses. Chemical constituents in water from wells or springs that exceeded State and Federal standards for public-water supplies or State criteria for agricultural uses were pH, arsenic, boron, chloride, iron, fluoride, manganese, nitrite plus nitrate, selenium, sulfate, or dissolved solids. Total-coliform bacteria were detected in water from 29 sites; fecal-coliform bacteria were detected in water from 6 of these 29 sites.Routt County, which has an area of 2,231 mi 2 (fig. 1) in northwestern Colorado, is experiencing rapid growth in population due to recreational and energyrelated activities. The population of Steamboat Springs, the largest community in the county, has increased from 2,400 in 1970 to more than 4,000 in 1977 (Michael J. Zopf, Routt County Department of Environmental Health, oral commun., 1978).In 1978, the U.S. Geological Survey, in cooperation with the Routt County Regional Planning Commission and the Routt County Department of Environmental Health, began a 1-year study to assess the quality of ground water in the county. This study extends and supplements earlier work of Brogden and Giles (1977) that was done in 1975 in parts of western Routt and eastern Moffat Counties. ApproachWater samples were collected from 130 wells and springs (pt. 1) during May and June 1978.Sampling sites were selected from a 1 isting of registered wells and springs provided by the Colorado Department of Natural Resources, Division of Water Resources, Office of the State Engineer. When possible, the depth to the water level was measured in each well prior to obtaining the water sample.Water temperature, specific conductance, and pH were measured at the well or spring site, and samples for bacteriological analyses were collected at all wells and springs.Samples for laboratory analyses of dissolved chemical constituents were collected from 35 of the wells and springs and analyzed in accordance with accepted procedures of the U.S. Geological Survey (Skougstad and others, 1979; Greeson and others, 1977).In addition to the water-quality data obtained during th...

30. Block chart showing relative proportion of ion equivalents to total anion equivalents calculated from annual mean concentrations of bicarbonate, chloride, fluoride, and sulfate for perennial streams in Yellow Creek basin, water