Geology topics

J. D. Petty

Publications and source records attributed to J. D. Petty.

At least 19 recordsLinked to original sources

USGS2009

Semivolatile organic compounds in residential air along the Arizona - Mexico border

Concerns about indoor air quality and the potential effects on people living in these environments are increasing as more reports about the toxicities and the potential indoor air exposure levels of household-use chemicals and chemicals fromhousingandfurnishingmanufactureinairarebeingassessed. Gas chromatography/mass spectrometry was used to confirm numerous airborne contaminants obtained from the analysis of semipermeable membrane devices deployed inside of 52 homes situated along the border between Arizona and Mexico. We also describe nontarget analytes in the organochlorine pesticide fractions of 12 of these homes; this fraction is also the most likelytocontainthebroadestscopeofbioconcentratablechemicals accumulated from the indoor air. Approximately 400 individual components were identified, ranging from pesticides to a wide array of hydrocarbons, fragrances such as the musk xylenes, flavors relating to spices, aldehydes, alcohols, esters and phthalate esters, and other miscellaneous types of chemicals. The results presented in this study demonstrate unequivocally that the mixture of airborne chemicals present indoors is far more complex than previously demonstrated. ?? 2009 American Chemical Society.

Environmental Science & Technology↗

USGS2009

Uptake rate constants and partition coefficients for vapor phase organic chemicals using semipermeable membrane devices (SPMDs)

To fully utilize semipermeable membrane devices (SPMDs) as passive samplers in air monitoring, data are required to accurately estimate airborne concentrations of environmental contaminants. Limited uptake rate constants (k ua ) and no SPMD air partitioning coefficient (K sa ) existed for vapor-phase contaminants. This research was conducted to expand the existing body of kinetic data for SPMD air sampling by determining k ua and K sa for a number of airborne contaminants including the chemical classes: polycyclic aromatic hydrocarbons, organochlorine pesticides, brominated diphenyl ethers, phthalate esters, synthetic pyrethroids, and organophosphate/organosulfur pesticides. The k ua s were obtained for 48 of 50 chemicals investigated and ranged from 0.03 to 3.07??m 3 ??g -1 ??d -1 . In cases where uptake was approaching equilibrium, K sa s were approximated. K sa values (no units) were determined or estimated for 48 of the chemicals investigated and ranging from 3.84E+5 to 7.34E+7. This research utilized a test system (United States Patent 6,877,724 B1) which afforded the capability to generate and maintain constant concentrations of vapor-phase chemical mixtures. The test system and experimental design employed gave reproducible results during experimental runs spanning more than two years. This reproducibility was shown by obtaining mean k ua values (n??=??3) of anthracene and p,p???-DDE at 0.96 and 1.57??m 3 ??g -1 ??d -1 with relative standard deviations of 8.4% and 8.6% respectively.

Atmospheric Environment↗

USGS2007

An evaluation of selenium concentrations in water, sediment, invertebrates, and fish from the Solomon River Basin

The Solomon River Basin is located in north-central Kansas in an area underlain by marine geologic shales. Selenium is an indigenous constituent of these shales and is readily leached into the surrounding groundwater. Portions of the Basin are irrigated primarily through the pumping of selenium-contaminated groundwater from wells onto fields in agricultural production. Water, sediment, macroinvertebrates, and fish were collected from various sites in the Basin in 1998 and analyzed for selenium. Selenium concentrations were analyzed spatially and temporally and compared to reported selenium toxic effect thresholds for specific ecosystem components: water, sediments, food-chain organisms, and wholebody fish. A selenium aquatic hazard assessment for the Basin was determined based on protocol established by Lemly. Throughout the Basin, water, macroinvertebrate, and whole fish samples exceeded levels suspected of causing reproductive impairment in fish. Population structures of several fish species implied that successful reproduction was occurring; however, the influence of immigration of fish from low-selenium habitats could not be discounted. Site-specific fish reproduction studies are needed to determine the true impact of selenium on fishery resources in the Basin. ?? Springer Science+Business Media B.V. 2007.

Environmental Monitoring and Assessment↗

USGS2006

Assessment of pesticide residues in army cutworm moths (Euxoa auxiliaris) from the Greater Yellowstone Ecosystem and their potential consequences to foraging grizzly bears (Ursus arctos horribilis)

During summer, a grizzly bear ( Ursus arctos horribilis ) in the Greater Yellowstone Ecosystem (GYE) (USA) can excavate and consume millions of army cutworm moths ( Euxoa auxiliaris ) (ACMs) that aggregate in high elevation talus. Grizzly bears in the GYE were listed as threatened by the US Fish and Wildlife Service in 1975 and were proposed for delisting in 2005. However, questions remain about key bear foods. For example, ACMs are agricultural pests and concern exists about whether they contain pesticides that could be toxic to bears. Consequently, we investigated whether ACMs contain and transport pesticides to bear foraging sites and, if so, whether these levels could be toxic to bears. In 1999 we collected and analyzed ACMs from six bear foraging sites. ACMs were screened for 32 pesticides with gas chromatography with electron capture detection (GC–ECD). Because gas chromatography with tandem mass spectrometry (GC–MS/MS) can be more sensitive than GC–ECD for certain pesticides, we revisited one site in 2001 and analyzed these ACMs with GC–MS/MS. ACMs contained trace or undetectable levels of pesticides in 1999 and 2001, respectively. Based on chemical levels in ACMs and numbers of ACMs a bear can consume, we calculated the potential of chemicals to reach physiological toxicity. These calculations indicate bears do not consume physiologically toxic levels of pesticides and allay concerns they are at risk from pesticides transported by ACMs. If chemical control of ACMs changes in the future, screening new ACM samples taken from bear foraging sites may be warranted.

Wyoming↗

USGS2005

Comparison of a novel passive sampler to standard water-column sampling for organic contaminants associated with wastewater effluents entering a New Jersey stream

Four water samples collected using standard depth and width water-column sampling methodology were compared to an innovative passive, in situ, sampler (the polar organic chemical integrative sampler or POCIS) for the detection of 96 organic wastewater-related contaminants (OWCs) in a stream that receives agricultural, municipal, and industrial wastewaters. Thirty-two OWCs were identified in POCIS extracts whereas 9-24 were identified in individual water-column samples demonstrating the utility of POCIS for identifying contaminants whose occurrence are transient or whose concentrations are below routine analytical detection limits. Overall, 10 OWCs were identified exclusively in the POCIS extracts and only six solely identified in the water-column samples, however, repetitive water samples taken using the standard method during the POCIS deployment period required multiple trips to the sampling site and an increased number of samples to store, process, and analyze. Due to the greater number of OWCs detected in the POCIS extracts as compared to individual water-column samples, the ease of performing a single deployment as compared to collecting and processing multiple water samples, the greater mass of chemical residues sequestered, and the ability to detect chemicals which dissipate quickly, the passive sampling technique offers an efficient and effective alternative for detecting OWCs in our waterways for wastewater contaminants.

New Jersey↗

USGS2004

Hazard assessment of a simulated oil spill on intertidal areas of the St. Lawrence River with SPMD-TOX

Phytoremediation in a simulated crude oil spill was studied with a “minimalistic” approach. The SPMD-TOX paradigm—a miniature passive sorptive device to collect and concentrate chemicals and microscale tests to detect toxicity—was used to monitor over time the bioavailability and potential toxicity of an oil spill. A simulated crude oil spill was initiated on an intertidal freshwater grass-wetland along the St. Lawrence River southwest of Quebec City, Quebec, Canada. Several phytoremediation treatments were investigated; to dissipate and ameliorate the spill, treatments included nutrient amendments with inorganic nitrogen sources (ammonium nitrate and sodium nitrate) and phosphate (super triple phosphate) with and without cut plants, with natural attenuation (no phytoremedial treatment) as a control. Sequestered oil residues were bioavailable in all oil-treated plots in Weeks 1 and 2. Interestingly, the samples were colored and fluoresced under ultraviolet light. In addition, microscale tests showed that sequestered residues were acutely toxic and genotoxic, as well as that they induced hepatic P 450 enzymes. Analysis of these data suggested that polycyclic aromatic hydrocarbons were among the bioavailable residues sequestered. In addition, these findings suggested that the toxic bioavailable fractions of the oil spill and degradation products dissipated rapidly over time because after the second week the water column contained no oil or detectable degradation products in this riverine intertidal wetland. SPMD-TOX revealed no evidence of bioavailable oil products in Weeks 4, 6, 8, and 12. All phytoremediation efforts appeared to be ineffective in changing either the dissipation rate or the ability to ameliorate the oil toxicity. SPMD-TOX analysis of the water columns from these riverine experimental plots profiled the occurrence, dissipation, and influence of phytoremediation on the bioavailability and toxicity of oil products (parent or degradation products).

Environmental Toxicology↗

USGS2004

Overview and comparison of lipid-containing semipermeable membrane devices and oysters (Crassostrea gigas) for assessing organic chemical exposure

We performed 20-d, flow-through exposures of lipid-containing semipermeable membrane devices (SPMDs) and Pacific oysters ( Crassostrea gigas ) to three concentrations (nominally 10, 100, and 250 ng/L) of a diverse mixture of polycyclic aromatic hydrocarbons (PAHs). Exposure water was seawater free of particulates larger than 0.1 μm. The results of these controlled laboratory studies demonstrated that SPMDs and oysters concentrate the same chemicals but that the relative amounts accumulated are different. For oysters, the 20-d mean (across treatments) concentration factors (CFs) of test compounds with log K ow ≤ 4.8 were much lower (4.0- to 20-fold lower) than those of the same compounds in SPMDs. In contrast, the 20-d CFs of PAHs with log K ow ≥ 5.6 in oysters from the low-level treatment were higher than the corresponding CFs for SPMDs. The CFs of these compounds in oysters from the low-level treatment ranged from approximately 3.0- to 13-fold higher than those in oysters from the high-level treatment. This physiologically mediated difference in oyster CFs appears to be linked to active feeding in the low-level treatment and to apparent toxicity-induced cessation of feeding (i.e., valve closure) in the high-level treatment. Because CFs for these compounds in oysters were not independent of exposure concentrations, it follows that tissue levels were not proportional to exposure concentration. However, both sampling approaches have advantages and disadvantages, and the appropriateness of their use depends on the goals of a given study.

Environmental Toxicology and Chemistry↗

USGS2004

Development of a passive, in situ, integrative sampler for hydrophilic organic contaminants in aquatic environments

Increasingly it is being realized that a holistic hazard assessment of complex environmental contaminant mixtures requires data on the concentrations of hydrophilic organic contaminants including new generation pesticides, pharmaceuticals, personal care products, and many chemicals associated with household, industrial, and agricultural wastes. To address this issue, we developed a passive in situ sampling device (the polar organic chemical integrative sampler [POCIS]) that integratively concentrates trace levels of complex mixtures of hydrophilic environmental contaminants, enables the determination of their time-weighted average water concentrations, and provides a method of estimating the potential exposure of aquatic organisms to the complex mixture of waterborne contaminants. Using a prototype sampler, linear uptake of selected herbicides and pharmaceuticals with log K ow S < 4.0 was observed for up to 56 d. Estimation of the ambient water concentrations of chemicals of interest is achieved by using appropriate uptake models and determination of POCIS sampling rates for appropriate exposure conditions. Use of POCIS in field validation studies targeting the herbicide diuron in the United Kingdom resulted in the detection of the chemical at estimated concentrations of 190 to 600 ng/L. These values are in agreement with reported levels found in traditional grab samples taken concurrently.

Environmental Toxicology and Chemistry↗

USGS2004

Compound-specific carbon and hydrogen isotope analysis of sub-parts per billion level waterborne petroleum hydrocarbons

Compound-specific carbon and hydrogen isotope analysis (CSCIA and CSHIA) has been increasingly used to study the source, transport, and bioremediation of organic contaminants such as petroleum hydrocarbons. In natural aquatic systems, dissolved contaminants represent the bioavailable fraction that generally is of the greatest toxicological significance. However, determining the isotopic ratios of waterborne hydrophobic contaminants in natural waters is very challenging because of their extremely low concentrations (often at sub-parts ber billion, or even lower). To acquire sufficient quantities of polycyclic aromatic hydrocarbons with 10 ng/L concentration for CSHIA, more than 1000 L of water must be extracted. Conventional liquid/liquid or solid-phase extraction is not suitable for such large volume extractions. We have developed a new approach that is capable of efficiently sampling sub-parts per billion level waterborne petroleum hydrocarbons for CSIA. We use semipermeable membrane devices (SPMDs) to accumulate hydrophobic contaminants from polluted waters and then recover the compounds in the laboratory for CSIA. In this study, we demonstrate, under a variety of experimental conditions (different concentrations, temperatures, and turbulence levels), that SPMD-associated processes do not induce C and H isotopic fractionations. The applicability of SPMD-CSIA technology to natural systems is further demonstrated by determining the ??13C and ??D values of petroleum hydrocarbons present in the Pawtuxet River, RI. Our results show that the combined SPMD-CSIA is an effective tool to investigate the source and fate of hydrophobic contaminants in the aquatic environments.

Environmental Science & Technology↗

USGS2004

Polar organic chemical integrative sampling and liquid chromatography- electrospray/ion-trap mass spectrometry for assessing selected prescription and illicit drugs in treated sewage effluents

The purpose of the research presented in this paper was twofold: (1) to demonstrate the coupling of two state-of-the-art techniques: a time-weighted polar organic chemical integrative sampler (POCIS) and microliquid chromatography–electrospray/ion-trap mass spectrometry and (2) to assess the ability of these methodologies to detect six drugs (azithromycin, fluoxetine, omeprazole, levothyroxine, methamphetamine, methylenedioxymethamphetamine [MDMA]) in a real-world environment, e.g., waste water effluent. In the effluent from three wastewater treatment plants (WWTPs), azithromycin was detected at concentrations ranging from 15 to 66 ng/L, which is equivalent to a total annual release of 1 to 4 kg into receiving waters. Detected and confirmed in the effluent from two WWTPs were two illicit drugs, methamphetamine and MDMA, at 2 and 0.5 ng/L, respectively. Although the ecotoxicologic significance of drugs in environmental matrices, particularly water, has not been closely examined, it can only be surmised that these substances have the potential to adversely affect biota that are continuously exposed to them even at very low levels. The potential for chronic effects on human health is also unknown but of increasing concern because of the multiuse character of water, particularly in densely populated, arid areas.

Archives of Environmental Contamination and Toxico↗

USGS2004

A holistic passive integrative sampling approach for assessing the presence and potential impacts of waterborne environmental contaminants

As an integral part of our continuing research in environmental quality assessment approaches, we have developed a variety of passive integrative sampling devices widely applicable for use in defining the presence and potential impacts of a broad array of contaminants. The semipermeable membrane device has gained widespread use for sampling hydrophobic chemicals from water and air, the polar organic chemical integrative sampler is applicable for sequestering waterborne hydrophilic organic chemicals, the stabilized liquid membrane device is used to integratively sample waterborne ionic metals, and the passive integrative mercury sampler is applicable for sampling vapor phase or dissolved neutral mercury species. This suite of integrative samplers forms the basis for a new passive sampling approach for assessing the presence and potential toxicological significance of a broad spectrum of environmental contaminants. In a proof-of-concept study, three of our four passive integrative samplers were used to assess the presence of a wide variety of contaminants in the waters of a constructed wetland, and to determine the effectiveness of the constructed wetland in removing contaminants. The wetland is used for final polishing of secondary-treatment municipal wastewater and the effluent is used as a source of water for a state wildlife area. Numerous contaminants, including organochlorine pesticides, polycyclic aromatic hydrocarbons, organophosphate pesticides, and pharmaceutical chemicals (e.g., ibuprofen, oxindole, etc.) were detected in the wastewater. Herein we summarize the results of the analysis of the field-deployed samplers and demonstrate the utility of this holistic approach.

Chemosphere↗

USGS2004

Purification of triolein for use in semipermeable membrane devices (SPMDs)

Analyses of triolein-containing semipermeable membrane devices (SPMDs) have sometimes been impeded by interferences caused by impurities endemic to triolein that codialyze with the analytes. Oleic acid and methyl oleate have been the most troublesome of these impurities because of their relatively high concentrations in triolein and because significant residues of both can persist even after size exclusion chromatographic (SEC) fractionation. These residues have also been blamed for false-positive signals during bioindicator testing of SPMD dialysates. To prevent these problems, a simple, cost-effective procedure was developed for purifying triolein destined for use in SPMDs: the bulk triolein is repeatedly (6×) partitioned against methanol. Tests of the procedure show that 14 C-oleic acid is completely removed from the triolein. After SEC fractionation, dialysates of standard-size SPMDs made with the purified triolein contain less than 5 μg of methyl oleate as compared to sometimes more than 500 μg for dialysates (also after SEC) of SPMDs made with unpurified triolein. Gas chromatographic analyses with flame ionization and electron capture detection show that the purification treatment also greatly reduces the number and size of peaks caused by unidentified contaminants in the triolein. Microtox basic assay of dialysates of SPMDs shows that those made with the purified triolein have lower acute toxicities than dialysates of SPMDs made with unpurified triolein. Yeast estrogen screen (YES) testing of SPMDs fabricated with unpurified and purified triolein demonstrates that the purification process removes all background estrogenic activity.

Chemosphere↗

USGS2003

Comparisons of coarse and fine versions of two carbons for reducing the bioavailabilities of sediment-bound hydrophobic organic contaminants

Coarse (whole) and finely ground Ambersorb 1500 and coarse and fine coconut charcoal were compared as to their efficiencies in scavenging organic contaminants desorbed from sediment. Aqueous slurries of a test sediment spiked (1 ppm) with p,p???-DDE (DDE), 2,2???,5,5???-tetrachlorobiphenyl (TCB), naphthalene (NAP), or phenanthrene (PHEN), and containing 1% levels of the test carbons were treated by shaking at 35 ??C while exposed to clusters of low-density polyethylene membrane (detox spiders). Controls consisted of spiked sediments and detox spiders but no added carbon of any kind and thus represented unimpeded bioavailabilities (to the spiders). After the treatments - agitation periods from 2.5 to 60 h, depending on contaminant hydrophobicity - the exposed detox spiders were analyzed. The fine carbon of either type was more effective than its coarser variant in obstructing contaminant bioavailabilities. The finer variants of both carbons obstructed the bioavailabilities of NAP and PHEN equally well as did the coarser variants of both. Whole Ambersorb 1500 and coarse coconut charcoal were similarly ineffective in intercepting TCB and DDE. Ground Ambersorb 1500 obstructed virtually all bioavailability of all four contaminants and was far more effective than fine coconut charcoal in intercepting DDE and TCB. An additional experiment compared the effectiveness of ground Ambersorb 1500 and fine coconut charcoal in obstructing the bioavailabilities from sediment of a broad array of spiked organochlorine pesticides. The performance of ground Ambersorb 1500 was again found to be superior; the bioavailable levels of each of the 27 pesticides were markedly lower in the presence of ground Ambersorb 1500 than in the presence of fine coconut charcoal.

Chemosphere↗

USGS2002

Sequestration of priority pollutant PAHs from sediment pore water employing semipermeable membrane devices

Semipermeable membrane devices (SPMDs) were employed to sample sediment pore water in static exposure studies under controlled laboratory conditions using (control pond and formulated) sediments fortified with 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs). The sediment fortification level of 750 ng/g was selected on the basis of what might be detected in a sediment sample from a contaminated area. The sampling interval consisted of 0, 4, 7, 14, and 28 days for each study. The analytical methodologies, as well as the extraction and sample cleanup procedures used in the isolation, characterization, and quantitation of 15 PPPAHs at different fortification levels in SPMDs, water, and sediment were reported previously (Williamson, M.S. Thesis, University of Missouri - Columbia, USA; Williamson et al., Chemosphere (This issue - PII: S0045-6535(02)00394-6)) and used for this project. Average (mean) extraction recoveries for each PPPAH congener in each matrix are reported and discussed. No procedural blank extracts (controls) were found to contain any PPPAH residues above the method quantitation limit, therefore, no matrix interferences were detected. The focus of this publication is to demonstrate the ability to sequester environmental contaminants, specifically PPPAHs, from sediment pore water using SPMDs and two different types of fortified sediment.

Chemosphere↗

USGS2002

HPLC-PFD determination of priority pollutant PAHs in water, sediment, and semipermeable membrane devices

High performance liquid chromatography coupled with programmable fluorescence detection was employed for the determination of 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs) in water, sediment, and semipermeable membrane devices (SPMDs). Chromatographic separation using this analytical method facilitates selectivity, sensitivity (ppt levels), and can serve as a non-destructive technique for subsequent analysis by other chromatographic and spectroscopic techniques. Extraction and sample cleanup procedures were also developed for water, sediment, and SPMDs using various chromatographic and wet chemical methods. The focus of this publication is to examine the enrichment techniques and the analytical methodologies used in the isolation, characterization, and quantitation of 15 PPPAHs in different sample matrices.

Chemosphere↗

USGS2002

Stabilized liquid membrane device (SLMD) for the passive, integrative sampling of labile metals in water

A stabilized liquid membrane device (SLMD) is described for potential use as an in situ, passive, integrative sampler for cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in natural waters. The SLMD (patent pending) consists of a 2.5-cm-wide by 15-cm-long strip of low-density polyethylene (LDPE) layflat tubing containing 1 mL of an equal mixture (v/v) of oleic acid (cis-9-octadecenoic acid) and EMO-8Q (7-[4-ethyl-1-methyloctyl]-8-quinolinol). The reagent mixture continuously diffuses to the exterior surface of the LDPE membrane, and provides for sequestration of several divalent metals for up to several weeks. Depending on sampler configuration, concentration factors of several thousand can be realized for these metal ions after just a few days. In addition to in situ deployment, the SLMD may be useful for laboratory determination of labile metal species in grab samples. Methods for minimizing the effects of water flow on the sampling rate are currently under investigation.

Water, Air, & Soil Pollution↗

USGS2001

Development of the permeability/performance reference compound approach for in situ calibration of semipermeable membrane devices

Permeability/performance reference compounds (PRCs) are analytically noninterfering organic compounds with moderate to high fugacity from semipermeable membrane devices (SPMDs) that are added to the lipid prior to membrane enclosure. Assuming that isotropic exchange kinetics (IEK) apply and that SPMD-water partition coefficients are known, measurement of PRC dissipation rate constants during SPMD field exposures and laboratory calibration studies permits the calculation of an exposure adjustment factor (EAF). In theory, PRC-derived EAF ratios reflect changes in SPMD sampling rates (relative to laboratory data) due to differences in exposure temperature, membrane biofouling, and flow velocity-turbulence at the membrane surface. Thus, the PRC approach should allow for more accurate estimates of target solute/vapor concentrations in an exposure medium. Under some exposure conditions, the impact of environmental variables on SPMD sampling rates may approach an order of magnitude. The results of this study suggest that most of the effects of temperature, facial velocity-turbulence, and biofouling on the uptake rates of analytes with a wide range of hydrophobicities can be deduced from PRCs with a much narrower range of hydrophobicities. Finally, our findings indicate that the use of PRCs permits prediction of in situ SPMD sampling rates within 2-fold of directly measured values.

Environmental Science & Technology↗

USGS2001

An evaluation of selenium concentrations in water, sediment, invertebrates, and fish from the Republican River Basin: 1997-1999

The Republican River Basin of Colorado,Nebraska, and Kansas lies in a valley which contains PierreShale as part of its geological substrata. Selenium is anindigenous constituent in the shale and is readily leached intosurrounding groundwater. The Basin is heavily irrigated throughthe pumping of groundwater, some of which is selenium-contaminated, onto fields in agricultural production. Water,sediment, benthic invertebrates, and/or fish were collected from46 sites in the Basin and were analyzed for selenium to determinethe potential for food-chain bioaccumulation, dietary toxicity,and reproductive effects of selenium in biota. Resultingselenium concentrations were compared to published guidelines orbiological effects thresholds. Water from 38% of the sites (n = 18) contained selenium concentrations exceeding 5 μg L -1 , which is reported to be a high hazard for selenium accumulation into the planktonic food chain. An additional 12 sites (26% of the sites) contained selenium in water between 3–5 μg L -1 , constituting a moderate hazard. Selenium concentrations in sedimentindicated little to no hazard for selenium accumulation fromsediments into the benthic food chain. Ninety-five percent ofbenthic invertebrates collected exhibited selenium concentrationsexceeding 3 μg g -1 , a level reported as potentially lethal to fish and birds that consume them. Seventy-five percent of fish collected in 1997, 90% in 1998, and 64% in 1999 exceeded 4 μg g -1 selenium, indicating a high potential for toxicity andreproductive effects. However, examination of weight profilesof various species of collected individual fish suggestedsuccessful recruitment in spite of selenium concentrations thatexceeded published biological effects thresholds for health andreproductive success. This finding suggested that universalapplication of published guidelines for selenium may beinappropriate or at least may need refinement for systems similarto the Republican River Basin. Additional research is needed todetermine the true impact of selenium on fish and wildliferesources in the Basin.

Environmental Monitoring and Assessment↗