bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrolysis of tert-butyl formate: Kinetics, products, and implications for the environmental impact of methyl tert-butyl ether
Authors: Church Clinton D , Pankow James F , Tratnyek Paul G 
Published: March 2010

Abstract
Asessing the environmental fate of methyl tert-butyl ether (MTBE) has become a subject of renewed interest because of the large quantities of this compound that are being used as an oxygenated additive in gasoline. Various studies on the fate of MTBE have shown that it can be degraded to tert-butyl formate (TBF), particularly in the atmosphere. Although it is generally recognized that TBF is subject to hydrolysis, the kinetics and products of this reaction under environmentally relevant conditions have not been described previously. In this study, we determined the kinetics of TBF hydrolysis as a function of pH and temperature. Over the pH range of 5 to 7, the neutral hydrolysis pathway predominates, with kN = (1.0 ± 0.2) × 10−6/s. Outside this range, strong pH effects were observed because of acidic and basic hydrolyses, from which we determined that kA = (2.7 ± 0.5) × 10−3/(M·s) and kB = 1.7 ± 0.3/(M·s). Buffered and unbuffered systems gave the same hydrolysis rates for a given pH, indicating that buffer catalysis was not significant under the conditions tested. The activation energies corresponding to kN, kA, and kB were determined to be 78 ± 5, 59 ± 4, and 88 ±11 kJ/mol, respectively. In all experiments, tert-butyl alcohol was found at concentrations corresponding to stoichiometric formation from TBF. Based on our kinetics data, the expected half-life for hydrolysis of TBF at pH = 2 and 4°C (as per some standard preservation protocols for water sampling) is 6 h. At neutral pH and 22°C, the estimated half-life is 5 d, and at pH = 11 and 22°C, the value is only 8 min.
Effects of a pulsed treatment with the herbicide afalon (active ingredient linuron) on macrophyte-dominated mesocosms. I. Responses of ecosystem metabolism
Authors: Kersting Kees , Van Wijngaarden René P.A. 
Published: March 2010

AbstractExperimental drainage ditches used as mesocosms were treated with linuron three times, at 4-week intervals, at nominal concentrations of 0, 0.5, 5, 15, and 50 μg/L. After each treatment, the mesocosms were kept static for 1 week. They were then flushed with noncontaminated surface water, with a residence time of 5 d, until the next treatment. Structural and functional measurements were made. A companion paper discusses the structural aspects. Dissolved oxygen concentrations and pH were measured continuously at 15-min intervals. Both variables declined during the static periods, and a lowest-observed-effect concentration (LOEC) of 5 μg/L was noted for both response variables. All mesocosms recovered during the flushing periods. Diurnal oxygen curves were used to calculate ecosystem gross primary production (GPP) and ecosystem oxygen consumption. Ecosystem oxygen consumption was not affected by the linuron treatments, but GPP had an EC50 of 21 μg/L during the static period after the first treatment. The EC50 for GPP increased to 36 μg/L after the second treatment and to 80 μg/L after the third treatment. This increase in EC50 is interpreted as an adaptation of the ecosystem, the mechanism of which could not be identified. The LOEC was 15 μg/L for all treatments and did not change over time. Between treatments, GPP recovered to the level of the controls. The LOEC for the long-term GPP was 50 μg/L.
What is the relationship between whole effluent toxicity and instream biological condition?
Authors: Diamond Jerome , Daley Christiana 
Published: March 2010

Abstract
We compileda data base of 250 dischargers across the United States and examined relationships between standardized Ceriodaphnia dubia and Pimephales promelas (fathead minnows), whole effluent toxicity (WET) test endpoints, and instream biological condition as measured by benthic macroinvertebrate assessments. Sites were included in the analysis if the effluents were not manipulated before testing (e.g., dechlorination), and standardized biological and physical habitat assessment methods were used upstream and directly downstream of the discharge. Several analyses indicated that fish endpoints were more related to instream biological condition than Ceriodaphnia WET endpoints. Dischargers that failed &lt;25% of their tests had ≤15% chance of exhibiting instream impairment. Effluent dilution was the strongest factor affecting relationships between WET and observed biological conditions. Effluents that comprised &gt;80% of the stream under low-flow conditions exhibited better relationships between WET and instream condition than effluents with greater dilution. Effluents that comprised &lt;20% of the stream had a low probability of exhibiting impairment, even if several WET test failures were observed over a 1-year period. Fish acute and chronic WET information could predict instream biological conditions; however, WET compliance, based on 7Q10 stream flow, was consistently conservative. Our results indicate that WET was more predictive of instream biological condition if several tests were conducted, more than one type of test was conducted, and endpoints within a test were relatively consistent over time.
Uncertainty analysis for an equilibrium partitioning-based estimator of polynuclear aromatic hydrocarbon bioaccumulation potential in sediments
Authors: Clarke Joan U , McFarland Victor A 
Published: March 2010

Abstract
In regulatory evaluations of contaminated sediments, an equilibrium partitioning-based screening test called theoretical bioaccumulation potential (TBP) is often performed to estimate the probable concentrations of neutral organic contaminants that would eventually accumulate in aquatic organisms from continuous exposure to a sediment. The TBP is calculated from contaminant concentration and organic carbon content of the sediment, lipid content of target organisms, and a partition coefficient, usually the biota-sediment accumulation factor (BSAF). However, routine applications of TBP have not included analysis of uncertainty. This paper demonstrates two methods for uncertainty analysis of TBP: a computational method that incorporates random and systematic error and a simulation method using bootstrap resampling of replicated model input parameters to calculate statistical uncertainty measures. For prediction of polynuclear aromatic hydrocarbon (PAH) bioaccumulation in bivalves exposed to contaminated sediments, uncertainty as a factor of TBP ranged from 1.2 to 4.8 using the computational method and 0.5 to 1.9 based on bootstrap 95% confidence intervals. Sensitivity analysis indicated that BSAF parameters, especially tissue contaminant concentration and lipid content, contributed most to TBP uncertainty. In bootstrap tests of significance, TBP significantly over- or underestimated actual PAH bioaccumulation in bivalves in 41% and 10% of comparisons, respectively.
Multiple computer-automated structure evaluation study of aquatic toxicity II. Fathead minnow
Authors: Klopman Gilles , Saiakhov Roustem , Rosenkranz Herbert S 
Published: March 2010

AbstractAn acute toxicity model was constructed on the basis of experimental data for 685 chemicals tested for toxicity for fathead minnow. The multiple computer-automated structure evaluation (M-CASE) program was used for the construction of the model. Based on a comparison between our results and published results, we found that the methodology is able to describe acute toxicity for the fathead minnow with high accuracy. The model incorporates the concept of a baseline activity as one of the parameters for the correlation as well as others parameters such as the presence of biophores, hardness-softness parameters, and other characteristics determined from quantum mechanical calculations. By using its artificial intelligence algorithm, M-CASE chooses automatically the most suitable set of parameters for evaluating the minnow toxicity of any organic molecule. We found that M-CASE can correctly predict acute toxicity for minnow for 80% of organic compounds with an average error of only 0.4 log units of lethal dose. The main toxicophores, corresponding to polar narcosis and to other types of reactive chemicals, were identified.
Toxicity of metal-contaminated sediments from keswick Reservoir, California, USA
Authors: Finlayson Brian , Fujimura Robert , Huang Zhang-Zhi 
Published: March 2010

AbstractKeswick Reservoir, California, USA, receives metal-laden acid-mine drainage (AMD) from the abandoned Iron Mountain Mine. Mixing of the AMD with reservoir water causes precipitation and deposition of metal-rich sludge in the reservoir. Hydroelectric generation activities can scour the sediments and mobilize trace metals cadmium, copper, and zinc into the water column, thus creating potentially toxic conditions to fish and aquatic invertebrates. Sediment samples collected from Keswick Reservoir in 1993 and 1994 were analyzed for acid-volatile sulfides and for simultaneously extractable metals (SEM), and whole sediments and sediment elutriates were tested for toxicity to rainbow trout (Oncorhynchus mykiss), amphipods (Hyalella azteca), and cladocerans (Ceriodaphnia dubia). Acid-volatile sulfide concentrations in the sediments were low (&lt;10 μmol/g H2S), indicating that dissolved metals in the sediment pore water were not limited by sulfide. The SEM concentrations were generally high (up to 11 μg/g Cd, 4,800 μg/g Cu, and 1,600 μg/g Zn, dry weight) in the sediments. Whole sediments and 20% w/w sediment elutriates from 16 sites were tested for toxicity. Low survival (as low as 0%) in whole sediments was generally associated with copper and zinc, and to a lesser extent cadmium, concentrations that exceeded probable effect level values for freshwater sediments; survival also may have been influenced by low pH and alkalinity conditions. Low survival (as low as 0%) in sediment elutriates was also generally associated with higher concentrations of dissolved zinc. Further study is required to formulate sediment cleanup levels that are protective offish and wildlife. Source control in the Iron Mountain Mine drainage will eventually significantly lessen the production of sediments.
Effects of physical (hypoxia, hyperoxia) and chemical (potassium dichromate, fenitrothion) stress on antioxidant enzyme activities inChironomus ripariusmg. (diptera, chironomidae) larvae: Potential biomarkers
Authors: Choi Jinhee , Roche Hélène , Caquet Thierry 
Published: March 2010

AbstractEffects of physical (hypoxia, hyperoxia) and chemical (potassium dichromate, fenitrothion) stress on antioxidant enzyme activities and hemoglobin content in Chironomus riparius Mg. (Diptera, Chironomidae) larvae were evaluated under laboratory conditions in order to identify pertinent biomarkers of stress. Hypoxia and hyperoxia caused an increase in Cu,Zn-superoxide dismutase (SOD) and Mn-SOD activities and a simultaneous decrease in total peroxidase (Px) and glutathione peroxidase (GSH-Px) activities. A parallel increase in hemoglobin concentration in the hemolymph was observed. The exposure to sublethal concentrations of both potassium dichromate and fenitrothion led to an increase in Cu,Zn-SOD and Mn-SOD activities and to a decrease in GSH-Px activity. Activation of catalase (CAT) was observed in the larvae exposed to high fenitrothion concentration (20μg/L). The response of SODs was rapid and sensitive to low chemical concentrations, but changes in CAT, Px, and GSH-Px were more specific and less sensitive.
Behavior of aliphatic alcohol polyethoxylates and their metabolites under standardized aerobic biodegradation conditions
Authors: Marcomini Antonio , Zanette Mauro , Pojana Giulio , Suter Marc J.-F. 
Published: March 2010

Abstract
Aerobic biodegradation of aliphatic alcohol polyethoxylates (AEs) was tested under screening test conditions (Organization for Economic Cooperation and Development [OECD] 301E protocol) using recently developed analytic methodologies for the specific determination of AEs and their neutral (polyethylene glycols [PEGs]) and carboxylic (carboxylated PEGs and AEs) aerobic metabolites. Biodegradation screening tests were performed under the same conditions on three typical, commercial AE blends and an individual, linear AE ethoxymer. The linear and monobranched AEs underwent a fast primary biodegradation, whereas the multibranched AEs underwent a slower biodegradation. Based on the formation and oligomeric distribution of PEGs and the lack of detection of other biointermediates before the formation of PEGs, the central cleavage of the AE molecule appeared to be the mechanism for primary biodegradation of the linear and monobranched AEs in the tested commercial blends. As a result, the shorter AE ethoxymers biodegraded faster than the longer ones. No PEGs were detected during biodegradation of the multibranched AEs. In addition, PEGs biodegraded more slowly than the parent AEs and were removed by hydrolysis, thus leading to shorter PEG oligomers, and by oxidative hydrolysis, thus forming carboxylated PEGs.
Polychlorinated biphenyls pattern analysis: Potential nondestructive biomarker in vertebrates for exposure to cytochrome P450-inducing organochlorines
Authors: van den Brink Nico W , de Ruiter-Dijkman Elze M , Broekhuizen Sim , Reijnders Peter J H , Bosveld Albertus T C 
Published: March 2010

Abstract
Biomarkers are valuable instruments to assess the risk from exposure of organisms to organochlorines. Ingeneral, however, these biomarkers are either destructive to the animal of interest or extremely difficult to obtain otherwise. In this paper, we present a nondestructive biomarker for exposure to cytochrome P450-inducing organochlorines. This marker is based on a pattern analysis of metabolizable and nonmetabolizable polychlorinated biphenyl (PCB) congeners, which occur in several kinds of tissues (and even blood) that can be obtained without serious effects on the organism involved. The fraction of metabolizable PCB congeners is negatively correlated with exposure to PCBs, which are known to induce specific P450 isoenzymes. This relation can be modeled by a logistic curve, which can be used to define critical levels of exposure. In addition, this method creates an opportunity to analyze biomarker responses in archived tissues stored at standard freezing temperatures (−20°C), at which responses to established biomarkers deteriorate. Furthermore, this method facilitates attribution of the enzyme induction to certain classes of compounds.
Quantifying solar spectral irradiance in aquatic habitats for the assessment of photoenhanced toxicity
Authors: Barron Mace G , Little Edward E , Calfee Robin , Diamond Steven 
Published: March 2010

Abstract
The spectra and intensity of solar radiation (solar spectral irradiance [SSI]) was quantified in selected aquatic habitats in the vicinity of an oil field on the California coast. Solar spectral irradiance measurements consisted of spectral scans (280–700 nm) and radiometric measurements of ultraviolet (UV): UVB (280–320 nm) and UVA (320–400 nm). Solar spectral irradiance measurements were taken at the surface and at various depths in two marsh ponds, a shallow wetland, an estuary lagoon, and the intertidal area of a high-energy sandy beach. Daily fluctuation in SSI showed a general parabolic relationship with time; maximum structure–activity relationship (SAR) was observed at approximate solar noon. Solar spectral irradiance measurements taken at 10-cm depth at approximate solar noon in multiple aquatic habitats exhibited only a twofold variation in visible light and UVA and a 4.5-fold variation in UVB. Visible light ranged from 11,000 to 19,000 μW/cm2, UVA ranged from 460 to 1,100 μW/cm2, and UVB ranged from 8.4 to 38 μW/cm2. In each habitat, the attenuation of light intensity with increasing water depth was differentially affected over specific wavelengths of SSI. The study results allowed the development of environmentally realistic light regimes necessary for photoenhanced toxicity studies.
Fathead minnow vitellogenin: Complementary DNA sequence and messenger RNA and protein expression after 17β-estradiol treatment
Authors: Korte Joseph J , Kahl Michael D , Jensen Kathleen M , Pasha Mumtaz S , Parks Louise G , LeBlanc Gerald A , Ankley Gerald T 
Published: March 2010

Abstract
Induction of vitellogenin (VTG) in oviparous animals has been proposed as a sensitive indicator of environmental contaminants that activate the estrogen receptor. In the present study, a sensitive ribonuclease protection assay (RPA) for VTG messenger RNA (mRNA) was developed for the fathead minnow (Pimephales promelas), a species proposed for routine endocrine-disrupting chemical (EDC) screening. The utility of this method was compared with an enzyme-linked immunosorbent assay (ELISA) specific for fathead minnow VTG protein. Assessment of the two methods included kinetic characterization of the plasma VTG protein and hepatic VTG mRNA levels in male fathead minnows following intraperitoneal injections of 17β-estradiol (E2) at two dose levels (0.5, 5.0 mg/kg). Initial plasma E2 concentrations were elevated in a dose-dependent manner but returned to normal levels within 2 d. Liver VTG mRNA was detected within 4 h, reached a maximum around 48 h, and returned to normal levels in about 6 d. Plasma VTG protein was detectable within 16 h of treatment, reached maximum levels at about 72 h, and remained near these maximum levels for at least 18 d. While the RPA was about 1,000 times more sensitive than the ELISA, the ELISA appears superior for routine screening tests. The ELISA method is relatively simple to perform and, because males lack a clearance mechanism for VTG, the protein remains at relatively high concentrations in the plasma for an extended period of time. As part of the development of the RPA, the complementary DNA (cDNA) sequence for fathead minnow VTG was determined and the deduced amino acid sequence compared with VTG sequences for other fish species.
Estimation of exposure criteria values for biliary polycyclic aromatic hydrocarbon metabolite concentrations in white suckers (Catostomus commersoni)
Authors: Cormier Susan M , Lin Edith LC , Fulk Florence , Subramanian Bhagya 
Published: March 2010

Abstract
A methodology was developed for deriving quantitative exposure criteria useful for comparing a site or a watershed to a reference condition and for defining the occurrence of extreme exposures. The prototype method used indicators of exposures to oil contamination and combustion by-products, naphthalene (NAPH)-type and benzo[a]pyrene (BaP)-type biliary metabolites from white suckers (Catostomus commersoni). The fish were collected from first- to third-order streams in the Regional Environmental Monitoring Assessment Program (REMAP) study of the Eastern Corn Belt Plains ecoregion at randomly selected sites and from third- or higher-order streams in conjunction with the Ohio Environmental Protection Agency (OEPA) Biomonitoring Program, which sampled sites of concern and reference sites selected by ecologists. The polycyclic aromatic hydrocarbon metabolites were measured using fixed-wavelength fluorescence with excitation/emission pairs at 290/335 nm for NAPH-type and 380/430 nm for BaP-type metabolites. Exposure criteria values were selected for each type of metabolite for both the REMAP study and the OEPA reference sites following the recommendations of the International Federation of Clinical Chemistry. Exposure criteria derived for each metabolite were not significantly different for REMAP and OEPA reference sites. More than one half of the OEPA nonreference sites were found to be contaminated, exceeding criteria values for both types of metabolites. This method for finding meaningful exposure criteria can be used to develop criteria of exposure to other contaminants for other wildlife and other ecosystems.
A test of watershed classification systems for ecological risk assessment
Authors: Detenbeck Naomi E , Batterman Sharon L , Brady Valerie J , Brazner John C , Snarski Virginia M , Taylor Debra L , Thompson Jo A , Arthur John W 
Published: March 2010

Abstract
To facilitate extrapolation among watersheds, ecological risk assessments should be based on a model of underlying factors influencing watershed response, particularly vulnerability. We propose a conceptual model of landscape vulnerability to serve as a basis for watershed classification systems to predict resistance and resilience of aquatic ecosystems to hydrology-related stressors. Watershed area, storage capacity, channel slope, and soil permeability determine sensitivity of lotic systems to stressors associated with land-use activities that impact hydrologic regimes. Natural hydrologic disturbance regimes also influence the resilience of aquatic systems by selecting for life history strategies associated with rapid recolonization following disturbance. Variability in some of these physiographic driving factors can be partitioned by landscape classification schemes such as the U.S. Forest Service Ecological Unit Classification System, while others (watershed storage) may explain remaining variability within landscape units. We are conducting a comparative watershed study to examine simple and interactive effects of physiographic units, watershed storage (lakes + wetlands), and land-clearing activities in watersheds surrounding the western arm of Lake Superior. Initial results for second-order watersheds indicate significant watershed class effects on baseflow water quality, percent motile biraphid diatom species in periphyton communities, habitat quality, and fish community integrity. Future studies have been designed to examine cumulative effects downstream.
Ecological effects of experimental insecticide applications on invertebrates in sahelian temporary ponds
Authors: Lahr Joost , Diallo Alpha O , Gadji Baba , Diouf Papa S , Bedaux Jacques JM , Badji Aliou , Ndour Khalifa B , Andreasen Jude E , van Straalen Nico M 
Published: March 2010

Abstract
The ecological impact offour insecticides used to control desert locustswas investigated during experimental field trials in natural temporary ponds in a cultivated savannah area of Senegal, West Africa. The insecticide formulations, dose rates, and application techniques were similar to those used in operational desert locust control. Average initial concentrations of fenitrothion, diflubenzuron, deltamethrin, and bendiocarb in pond water were 80, 10.4, 0.45, and 24.0 μg/L, respectively. Diflubenzuron and deltamethrin virtually disappeared in 24 h. Pseudo–first-order half-lives were 34 h for fenitrothion and 17 d for bendiocarb. Fenitrothion and deltamethrin significantly reduced population densities of backswimmers of the genus Anisops (Hemiptera, No-tonectidae) and in addition caused an extensive kill of other species of insects. Both insecticide applications were also followed by reductions of zooplankton densities, especially Cladocera, and deltamethrin eradicated populations of fairy shrimp (Streptoce-phalus spp.: Branchiopoda, Anostraca). Diflubenzuron only affected crustaceans, i.e., cladocerans and fairy shrimp. The least harmful insecticide in the study was bendiocarb, which only reduced the density of cladocerans. Recovery proceeded at fixed rates, which were different for each taxon. Anisops spp. recovered from the treatments in 1 to 4 weeks, most likely through aerial migration. Cladocerans returned to normal densities in 3 to 6 weeks. Streptocephalus spp., however, whose resting eggs presumably need desiccation during the dry season to be able to hatch, did not reappear until the next rainy season, one year later. It is concluded that contamination of temporary ponds in the Sahel by insecticide drift from desert locust control operations with any of the four insecticides should be avoided.