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At least 289 records · Page 16Linked to original sources
USGS2007

Comparison of fate and transport of isoxaflutole to atrazine and metolachlor in 10 Iowa rivers

Isoxaflutole (IXF), a newer low application rate herbicide, was introduced for weed control in corn (Zea mays) to use as an alternative to widely applied herbicides such as atrazine. The transport of IXF in streamwater has not been well-studied. The fate and transport of IXF and two of its degradation products was studied in 10 Iowa rivers during 2004. IXF rapidly degrades to the herbicidally active diketonitrile (DKN), which degrades to a biologically inactive benzoic acid (BA) analogue. IXF was detected in only four, DKN in 56, and BA in 43 of 75 samples. The concentrations of DKN and BA were approximately 2 orders of magnitude less than those of the commonly detected triazine and acetamide herbicides and their degradation products. Concentrations of IXF, DKN, and BA were highest during the May through June postplanting period. The concentration ratio of BA/DKN was similar to the deethylatrazine/atrazine ratio with smaller ratios occurring during May and June. The relative temporal variation of DKN and BA was similar to that observed for atrazine and deethylatrazine. This study shows that low application rate herbicides can have similar temporal transport patterns in streamwater as compared to more widely applied herbicides but at lower concentrations.

Iowa↗
USGS2007

A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment

Arsenic (As) geochemistry and sorption behavior were measured in As- and iron (Fe)-rich sediments of Haiwee Reservoir by deploying undoped (clear) polyacrylamide gels and hydrous ferric oxide (HFO)-doped gels in a gel probe equilibrium sampler, which is a novel technique for directly measuring the effects of porewater composition on As adsorption to Fe oxides phases in situ. Arsenic is deposited at the sediment surface as As(V) and is reduced to As(III) in the upper layers of the sediment (0-8 cm), but the reduction of As(V) does not cause mobilization into the porewater. Dissolved As and Fe concentrations increased at depth in the sediment column driven by the reductive dissolution of amorphous Fe(III) oxyhydroxides and conversion to a mixed Fe(II, III) green rust-type phase. Adsorption of As and phosphorous (P) onto HFO-doped gels was inhibited at intermediate depths (10-20 cm), possibly due to dissolved organic or inorganic carbon, indicating that dissolved As concentrations were at least partially controlled by porewater composition rather than surface site availability. In sediments that had been recently exposed to air, the region of sorption inhibition was not observed, suggesting that prior exposure to air affected the extent of reductive dissolution, porewater chemistry, and As adsorption behavior. Arsenic adsorption onto the HFO-doped gels increased at depths >20 cm, and the extent of adsorption was most likely controlled by the competitive effects of dissolved phosphate. Sediment As adsorption capacity appeared to be controlled by changes in porewater composition and competitive effects at shallower depths, and by reductive dissolution and availability of sorption sites at greater burial depths. ?? 2008 American Chemical Society.

Environmental Science & Technology↗
USGS2007

Cadmium ecophysiology in seven stonefly (Plecoptera) species: Delineating sources and estimating susceptibility

A major challenge in ecotoxicology lies in generating data under experimental conditions that are relevant to understanding contaminant effects in nature. Biodynamic modeling combines species-specific physiological traits to make predictions of metal bioaccumulation that fare well when tested in the field. We generated biodynamic models for seven predatory stonefly (Plecoptera) species representing the families Perlidae (5) and Perlodidae (2). Each taxon was exposed to cadmium independently via diet and via solution. Species varied approximately 2.6 fold in predicted steady-state cadmium concentrations. Diet was the predominant source of accumulated cadmium in five of the seven species and averaged 53.2 ± 9.6% and 90.2 ± 3.7% of net Cd accumulation in perlids and perlodids, respectively. Differences in Cd bioaccumulation between the two families were largely driven by differences in dissolved accumulation rates, which were considerably slower in perlodids than in perlids. We further examined the subcellular compartmentalization of Cd accumulated from independent aqueous and dietary exposures. Predicted steady-state concentrations were modified to only consider Cd accumulated in metal-sensitive subcellular compartments. These values ranged 5.3 fold. We discuss this variability within a phylogenetic context and its implications for bioassessment.

Environmental Science & Technology↗
USGS2008

Evaluation of statistical treatments of left-censored environmental data using coincident uncensored data sets: I. Summary statistics

The main classes of statistical treatment of below-detection limit (left-censored) environmental data for the determination of basic statistics that have been used in the literature are substitution methods, maximum likelihood, regression on order statistics (ROS), and nonparametric techniques. These treatments, along with using all instrument-generated data (even those below detection), were evaluated by examining data sets in which the true values of the censored data were known. It was found that for data sets with less than 70% censored data, the best technique overall for determination of summary statistics was the nonparametric Kaplan-Meier technique. ROS and the two substitution methods of assigning one-half the detection limit value to censored data or assigning a random number between zero and the detection limit to censored data were adequate alternatives. The use of these two substitution methods, however, requires a thorough understanding of how the laboratory censored the data. The technique of employing all instrument-generated data - including numbers below the detection limit - was found to be less adequate than the above techniques. At high degrees of censoring (greater than 70% censored data), no technique provided good estimates of summary statistics. Maximum likelihood techniques were found to be far inferior to all other treatments except substituting zero or the detection limit value to censored data.

Environmental Science & Technology↗
USGS2008

N-15 NMR study of the immobilization of 2,4- and 2,6-dinitrotoluene in aerobic compost

Large-scale aerobic windrow composting has been used to bioremediate washout lagoon soils contaminated with the explosives TNT (2,4,6-trinitrotoluene) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) at several sites within the United States. We previously used 15 N NMR to investigate the reduction and binding of T 15 NT in aerobic bench -scale reactors simulating the conditions of windrow composting. These studies have been extended to 2,4-dinitrotoluene (2,4DNT) and 2,6-dinitrotoluene (2,6DNT), which, as impurities in TNT, are usually present wherever soils have been contaminated with TNT. Liquid-state 15 N NMR analyses of laboratory reactions between 4-methyl-3-nitroaniline- 15 N , the major monoamine reduction product of 2,4DNT, and the Elliot soil humic acid, both in the presence and absence of horseradish peroxidase, indicated that the amine underwent covalent binding with quinone and other carbonyl groups in the soil humic acid to form both heterocyclic and non-heterocyclic condensation products. Liquid-state 15 N NMR analyses of the methanol extracts of 20 day aerobic bench-scale composts of 2,4-di- 15 N -nitrotoluene and 2,6-di- 15 N -nitrotoluene revealed the presence of nitrite and monoamine, but not diamine, reduction products, indicating the occurrence of both dioxygenase enzyme and reductive degradation pathways. Solid-state CP/MAS 15 N NMR analyses of the whole composts, however, suggested that reduction to monoamines followed by covalent binding of the amines to organic matter was the predominant pathway.

Environmental Science & Technology↗
USGS2008

Reproductive disruption in fish downstream from an estrogenic wastewater effluent

To assess the impact of an estrogenic wastewater treatment plant (WWTP) effluent on fish reproduction, white suckers ( Catostomus commersoni ) were collected from immediately upstream and downstream (effluent site) of the city of Boulder, CO, WWTP outfall. Gonadal intersex, altered sex ratios, reduced gonad size, disrupted ovarian and testicular histopathology, and vitellogenin induction consistent with exposure to estrogenic wastewater contaminants were identified in white suckers downstream from the WWTP outfall and not at the upstream site. The sex ratio was female-biased at the effluent site in both the fall of 2003 and the spring of 2004; the frequency of males at the effluent site (17–21%) was half that of the upstream site (36–46%). Intersex white suckers comprised 18–22% of the population at the effluent site. Intersex fish were not found at the upstream site. Chemical analyses determined that the WWTP effluent contained a complex mixture of endocrine-active chemicals, including 17β-estradiol (E 2 ) 17α-ethynylestradiol, alkylphenols, and bisphenol A resulting in an estimated total estrogen equivalence of up to 31 ng E 2 L −1 . These results indicate that the reproductive potential of native fishes may be compromised in wastewater-dominated streams.

Colorado↗
USGS2007

Contaminated salmon and the public's trust

Scientific uncertainties often make it difficult for environmental policy makers to determine how to communicate risks to the public. A constructive, holistic, multisectoral dialogue about an issue can improve understanding of uncertainties from different perspectives and clarify options for risk communication. Many environmental issues could benefit from explicit promotion of such a dialogue. When issues are complex, unconstructive advocacy, narrow focus, and exclusion of selected parties from decision making can erode public trust in science and lead to cynicism about the policies of government and the private sector.

Environmental Science & Technology↗
USGS2010

Variability in pesticide deposition and source contributions to snowpack in western U.S. National Parks

Fifty-six seasonal snowpack samples were collected at remote alpine, subarctic, and arctic sites in eight Western U.S. national parks during three consecutive years (2003−2005). Four current-use pesticides (CUPs) (dacthal (DCPA), chlorpyrifos, endosulfans, and γ-hexachlorocyclohexane (HCH)) and four historic-use pesticides (HUPs) (dieldrin, α-HCH, chlordanes, and hexachlorobenzene (HCB)) were commonly measured at all sites, during all years. The mean coefficient of variation for pesticide concentrations was 15% for site replicate samples, 41% for intrapark replicate samples, and 59% for interannual replicate samples. The relative pesticide concentration profiles were consistent from year to year but unique for individual parks, indicating a regional source effect. HUP concentrations were well-correlated with regional cropland intensity when the effect of temperature on snow-air partitioning was considered. The mass of individual CUPs used in regions located one-day upwind of the parks was calculated using air mass back trajectories, and this was used to explain the distribution of CUPs among the parks. The percent of the snowpack pesticide concentration due to regional transport was high (>75%) for the majority of pesticides in all parks. These results suggest that the majority of pesticide contamination in U.S. national parks is due to regional pesticide use in North America.

Environmental Science & Technology↗
USGS2010

Pharmaceutical formulation facilities as sources of opioids and other pharmaceuticals to wastewater treatment plant effluents

Facilities involved in the manufacture of pharmaceutical products are an under-investigated source of pharmaceuticals to the environment. Between 2004 and 2009, 35 to 38 effluent samples were collected from each of three wastewater treatment plants (WWTPs) in New York and analyzed for seven pharmaceuticals including opioids and muscle relaxants. Two WWTPs (NY2 and NY3) receive substantial flows (>20% of plant flow) from pharmaceutical formulation facilities (PFF) and one (NY1) receives no PFF flow. Samples of effluents from 23 WWTPs across the United States were analyzed once for these pharmaceuticals as part of a national survey. Maximum pharmaceutical effluent concentrations for the national survey and NY1 effluent samples were generally <1 microg/L. Four pharmaceuticals (methadone, oxycodone, butalbital, and metaxalone) in samples of NY3 effluent had median concentrations ranging from 3.4 to >400 microg/L. Maximum concentrations of oxycodone (1700 microg/L) and metaxalone (3800 microg/L) in samples from NY3 effluent exceeded 1000 microg/L. Three pharmaceuticals (butalbital, carisoprodol, and oxycodone) in samples of NY2 effluent had median concentrations ranging from 2 to 11 microg/L. These findings suggest that current manufacturing practices at these PFFs can result in pharmaceuticals concentrations from 10 to 1000 times higher than those typically found in WWTP effluents.

Environmental Science & Technology↗
USGS2010

Cyanotoxin mixtures and taste-and-odor compounds in cyanobacterial blooms from the midwestern united states

The mixtures of toxins and taste-and-odor compounds present during cyanobacterial blooms are not well characterized and of particular concern when evaluating potential human health risks. Cyanobacterial blooms were sampled in twenty-three Midwestern United States lakes and analyzed for community composition, thirteen cyanotoxins by liquid chromatography/mass spectrometry and immunoassay, and two taste-and-odor compounds by gas chromatography/mass spectrometry. Aphanizomenon, Cylindrospermopsis and/or Microcystis were dominant in most (96%) blooms, but community composition was not strongly correlated with toxin and taste-and-odor occurrence. Microcystins occurred in all blooms. Total microcystin concentrations measured by liquid chromatography/mass spectrometry and immunoassay were linearly related (rs = 0.76, p < 0.01) and LC/MS/MS concentrations were lower than or similar to ELISA in most (85%) samples. Geosmin (87%), 2-methylisoborneol (39%), anatoxin-a (30%), saxitoxins (17%), cylindrospermopsins (9%), and nodularin-R (9%) also were present in these blooms. Multiple classes of cyanotoxins occurred in 48% of blooms and 95% had multiple microcystin variants. Toxins and taste-and-odor compounds frequently co-occurred (91% of blooms), indicating odor may serve as a warning that cyanotoxins likely are present. However, toxins occurred more frequently than taste-and-odor compounds, so odor alone does not provide sufficient warning to ensure human-health protection.

Environmental Science & Technology↗
USGS2010

The plight of the bees

The loss of biodiversity is a trend that is garnering much concern. As organisms have evolved mutualistic and synergistic relationships, the loss of one or a few species can have a much wider environmental impact. Since much pollination is facilitated by bees, the reported colony collapse disorder has many worried of widespread agricultural fallout and thus deleterious impact on human foodstocks. In this Feature, Spivak et al. review what is known of the present state of bee populations and provide information on how to mitigate and reverse the trend.

Environmental Science & Technology↗
USGS2010

A role for analytical chemistry in advancing our understanding of the occurrence, fate, and effects of Corexit Oil Dispersants

On April 24, 2010, the sinking of the Deepwater Horizon oil rig resulted in the release of oil into the Gulf of Mexico. As of July 19, 2010, the federal government's Deepwater Horizon Incident Joint Information Center estimates the cumulative range of oil released is 3,067,000 to 5,258,000 barrels, with a relief well to be completed in early August. By comparison, the Exxon Valdez oil spill released a total of 260,000 barrels of crude oil into the environment. As of June 9, BP has used over 1 million gallons of Corexit oil dispersants to solubilize oil and help prevent the development of a surface oil slick. Oil dispersants are mixtures containing solvents and surfactants that can exhibit toxicity toward aquatic life and may enhance the toxicity of components of weathered crude oil. Detailed knowledge of the composition of both Corexit formulations and other dispersants applied in the Gulf will facilitate comprehensive monitoring programs for determining the occurrence, fate, and biological effects of the dispersant chemicals. The lack of information on the potential impacts of oil dispersants has caught industry, federal, and state officials off guard. Until compositions of Corexit 9500 and 9527 were released by the U.S. Environmental Protection Agency online, the only information available consisted of Material Safety Data Sheets (MSDS), patent documentation, and a National Research Council report on oil dispersants. Several trade and common names are used for the components of the Corexits. For example, Tween 80 and Tween 85 are oligomeric mixtures.

Environmental Science & Technology↗
USGS2010

New technique for quantification of elemental hg in mine wastes and its implications for mercury evasion into the atmosphere

Mercury in the environment is of prime concern to both ecosystem and human health. Determination of the molecular-level speciation of Hg in soils and mine wastes is important for understanding its sequestration, mobility, and availability for methylation. Extended X-ray absorption fine structure (EXAFS) spectroscopy carried out under ambient P-T conditions has been used in a number of past studies to determine Hg speciation in complex mine wastes and associated soils. However, this approach cannot detect elemental (liquid) mercury in Hg-polluted soils and sediments due to the significant structural disorder of liquid Hg at ambient-temperature. A new sample preparation protocol involving slow cooling through the crystallization temperature of Hg(0) (234 K) results in its transformation to crystalline α-Hg(0). The presence and proportion of Hg(0), relative to other crystalline Hg-bearing phases, in samples prepared in this way can be quantified by low-temperature (77 K) EXAFS spectroscopy. Using this approach, we have determined the relative concentrations of liquid Hg(0) in Hg mine wastes from several sites in the California Coast Range and have found that they correlate well with measured fluxes of gaseous Hg released during light and dark exposure of the same samples, with higher evasion ratios from samples containing higher concentrations of liquid Hg(0). Two different linear relationships are observed in plots of the ratio of Hg emission under light and dark conditions vs % Hg(0), corresponding to silica−carbonate- and hot springs-type Hg deposits, with the hot springs-type samples exhibiting higher evasion fluxes than silica−carbonate type samples at similar Hg(0) concentrations. Our findings help explain significant differences in Hg evasion data for different mine sites in the California Coast Range.

Environmental Science & Technology↗
USGS2010

Measurement of dissolved organic matter fluorescense in aquatic environments: An interlaboratory comparison

The fluorescent properties of dissolved organic matter (DOM) are often studied in order to infer DOM characteristics in aquatic environments, including source, quantity, composition, and behavior. While a potentially powerful technique, a single widely implemented standard method for correcting and presenting fluorescence measurements is lacking, leading to difficulties when comparing data collected by different research groups. This paper reports on a large-scale interlaboratory comparison in which natural samples and well-characterized fluorophores were analyzed in 20 laboratories in the U.S., Europe, and Australia. Shortcomings were evident in several areas, including data quality-assurance, the accuracy of spectral correction factors used to correct EEMs, and the treatment of optically dense samples. Data corrected by participants according to individual laboratory procedures were more variable than when corrected under a standard protocol. Wavelength dependency in measurement precision and accuracy were observed within and between instruments, even in corrected data. In an effort to reduce future occurrences of similar problems, algorithms for correcting and calibrating EEMs are described in detail, and MATLAB scripts for implementing the study's protocol are provided. Combined with the recent expansion of spectral fluorescence standards, this approach will serve to increase the intercomparability of DOM fluorescence studies.

Environmental Science & Technology↗
USGS2010

Zinc isotopic composition of particulate matter generated during the combustion of coal and coal + tire-derived fuels

Atmospheric Zn emissions from the burning of coal and tire-derived fuel (TDF) for power generation can be considerable. In an effort to lay the foundation for tracking these contributions, we evaluated the Zn isotopes of coal, a mixture of 95 wt % coal + 5 wt % TDF, and the particulate matter (PM) derived from their combustion in a power-generating plant. The average Zn concentrations and δ(66)Zn were 36 mg/kg and 183 mg/kg and +0.24‰ and +0.13‰ for the coal and coal + TDF, respectively. The δ(66)Zn of the PM sequestered in the cyclone-type mechanical separator was the lightest measured, -0.48‰ for coal and -0.81‰ for coal+TDF. The δ(66)Zn of the PM from the electrostatic precipitator showed a slight enrichment in the heavier Zn isotopes relative to the starting material. PM collected from the stack had the heaviest δ(66)Zn in the system, +0.63‰ and +0.50‰ for the coal and coal + TDF, respectively. Initial fractionation during the generation of a Zn-rich vapor is followed by temperature-dependent fractionation as Zn condenses onto the PM. The isotopic changes of the two fuel types are similar, suggesting that their inherent chemical differences have only a secondary impact on the isotopic fractionation process.

Environmental Science & Technology↗
USGS2010

Regional contamination versus regional dietary differences: Understanding geographic variation in brominated and chlorinated contaminant levels in polar bears

The relative contribution of regional contamination versus dietary differences to geographic variation in polar bear ( Ursus maritimus ) contaminant levels is unknown. Dietary variation between Alaska, Canada, East Greenland, and Svalbard subpopulations was assessed by muscle nitrogen and carbon stable isotope (δ 15 N, δ 13 C) and adipose fatty acid (FA) signatures relative to their main prey (ringed seals). Western and southern Hudson Bay signatures were characterized by depleted δ 15 N and δ 13 C, lower proportions of C 20 and C 22 monounsaturated FAs and higher proportions of C 18 and longer chain polyunsaturated FAs. East Greenland and Svalbard signatures were reversed relative to Hudson Bay. Alaskan and Canadian Arctic signatures were intermediate. Between-subpopulation dietary differences predominated over interannual, seasonal, sex, or age variation. Among various brominated and chlorinated contaminants, diet signatures significantly explained variation in adipose levels of polybrominated diphenyl ether (PBDE) flame retardants (14−15%) and legacy PCBs (18−21%). However, dietary influence was contaminant class-specific, since only low or nonsignificant proportions of variation in organochlorine pesticide (e.g., chlordane) levels were explained by diet. Hudson Bay diet signatures were associated with lower PCB and PBDE levels, whereas East Greenland and Svalbard signatures were associated with higher levels. Understanding diet/food web factors is important to accurately interpret contaminant trends, particularly in a changing Arctic.

Environmental Science & Technology↗
USGS2010

Nitrogen contamination of surficial aquifers - A growing legacy

The virtual ubiquity of fertilizer-fed agriculture, increasing over several decades, has become necessary to support the global human population. Ironically, widespread use of nitrogen (N) has contaminated another vital resource: surficial fresh groundwater. Further, as nitrous oxide (N 2 O) is a potent greenhouse gas, anthropogenic manipulation of N budgets has ramifications that can extend far beyond national borders. To get a handle on the size of the problem, Puckett et al. present an approach to track historical contamination and thus analyze trends now and in the past with implications for the future.

Environmental Science & Technology↗