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51.
Pamela K. Jensen Chad E. Wujcik Michelle K. McGuire Mark A. McGuire 《Journal of environmental science and health. Part. B》2016,51(4):254-259
Simple high-throughput procedures were developed for the direct analysis of glyphosate [N-(phosphonomethyl)glycine] and aminomethylphosphonic acid (AMPA) in human and bovine milk and human urine matrices. Samples were extracted with an acidified aqueous solution on a high-speed shaker. Stable isotope labeled internal standards were added with the extraction solvent to ensure accurate tracking and quantitation. An additional cleanup procedure using partitioning with methylene chloride was required for milk matrices to minimize the presence of matrix components that can impact the longevity of the analytical column. Both analytes were analyzed directly, without derivatization, by liquid chromatography tandem mass spectrometry using two separate precursor-to-product transitions that ensure and confirm the accuracy of the measured results. Method performance was evaluated during validation through a series of assessments that included linearity, accuracy, precision, selectivity, ionization effects and carryover. Limits of quantitation (LOQ) were determined to be 0.1 and 10 µg/L (ppb) for urine and milk, respectively, for both glyphosate and AMPA. Mean recoveries for all matrices were within 89–107% at three separate fortification levels including the LOQ. Precision for replicates was ≤7.4% relative standard deviation (RSD) for milk and ≤11.4% RSD for urine across all fortification levels. All human and bovine milk samples used for selectivity and ionization effects assessments were free of any detectable levels of glyphosate and AMPA. Some of the human urine samples contained trace levels of glyphosate and AMPA, which were background subtracted for accuracy assessments. Ionization effects testing showed no significant biases from the matrix. A successful independent external validation was conducted using the more complicated milk matrices to demonstrate method transferability. 相似文献
52.
Reduction of phosphorus (P) inputs to surface waters may decrease eutrophication. Some researchers have proposed filtering dissolved P in runoff with P-sorptive byproducts in structures placed in hydrologically active areas with high soil P concentrations. The objectives of this study were to construct and monitor a P removal structure in a suburban watershed and test the ability of empirically developed flow-through equations to predict structure performance. Steel slag was used as the P sorption material in the P removal structure. Water samples were collected before and after the structure using automatic samples and analyzed for total dissolved P. During the first 5 mo of structure operation, 25% of all dissolved P was removed from rainfall and irrigation events. Phosphorus was removed more efficiently during low flow rate irrigation events with a high retention time than during high flow rate rainfall events with a low retention time. The six largest flow events occurred during storm flow and accounted for 75% of the P entering the structure and 54% of the P removed by the structure. Flow-through equations developed for predicting structure performance produced reasonable estimates of structure "lifetime" (16.8 mo). However, the equations overpredicted cumulative P removal. This was likely due to differences in pH, total Ca and Fe, and alkalinity between the slag used in the structure and the slag used for model development. This suggests the need for an overall model that can predict structure performance based on individual material properties. 相似文献
53.
54.
Stephanie Gardham Grant C. Hose Stuart L. Simpson Chad Jarolimek Anthony A. Chariton 《Environmental science and pollution research international》2014,21(11):7130-7139
Understanding the effects of sediment contaminants is pivotal to reducing their impact in aquatic environments. Outdoor mesocosms enable us to decipher the effects of these contaminants in environmentally realistic scenarios, providing a valuable link between laboratory and field experiments. However, because of their scale, mesocosm experiments are often complex to set up and manage. The creation of environmentally realistic conditions, particularly when using artificially contaminated sediment, is one issue. Here, we describe changes in geochemistry over 1.5 years of a sediment spiked with four different concentrations of copper, within a large freshwater mesocosm facility. The spiking procedure included proportional amendments with garden lime to counteract the decreases in pH caused by the copper additions. The majority of copper within the spiked mesocosm sediments partitioned to the particulate phase with low microgram per liter concentrations measured in the pore waters and overlying waters. The minimum partition coefficient following equilibration between pore waters and sediments was 1.5?×?104 L/kg, which is well within the range observed for field-contaminated sediments (1?×?104 to 1?×?106 L/kg). Recommendations are made for the in situ spiking of sediments with metals in large outdoor mesocosms. These include selecting an appropriate sediment type, adjusting the pH, allowing sufficient equilibration time, and regular mixing and monitoring of metal partitioning throughout the experimental period. 相似文献
55.
56.
Most agricultural information is reported by government sources on a state or county basis. The purpose of this study was
to demonstrate use of geospatial data, the 2002 Agricultural Cropland Data Layer (CDL) for the mid-Atlantic region, to characterize
agricultural, environmental, and other scientific parameters for the Chincoteague Bay subbasin using geographic information
systems. This study demonstrated that agriculture can be characterized accurately on subbasin and subwatershed bases, thus
complimenting various assessment technologies. Approximately 28% of the dry land of the subbasin was cropland. Field corn
was the largest crop. Soybeans, either singly or double-cropped with wheat, were the second most predominant crop. Although
the subbasin is relatively small, cropping practices in the northern part were different from those in the southern portion.
Other crops, such as fresh vegetables and vegetables grown for processing, were less than 10% of the total cropland. A conservative
approximation of the total pesticide usage in the subbasin in 2002 was over 277,000 lbs of active ingredients. Herbicides
represented the most frequently used pesticides in the subbasin, both in number (17) and in total active ingredients (over
261,000 lbs). Ten insecticides predominated in the watershed, while only small quantities of three fungicides were used. Total
pesticide usage and intensity were estimated using the CDL. Nutrient inputs to cropland from animal manure, chemical fertilizer,
and atmospheric deposition were modeled at over 30 million pounds of nitrogen and over 7 million pounds of phosphorous. Crops
under conservation tillage had the largest input of both nutrients. 相似文献
57.
Ninon F. V. Meyer Niko Balkenhol Trishna Dutta Maarten Hofman Jean-Yves Meyer Euan G. Ritchie Charlotte Alley Chad Beranek Cassandra K. Bugir Alex Callen Simon Clulow Michael V. Cove Kaya Klop-Toker Omar R. Lopez Michael Mahony Robert Scanlon Sandeep Sharma Elen Shute Rose Upton Emy Guilbault Andrea S. Griffin Edwin Hernández Pérez Lachlan G. Howell John-Paul King Dean Lenga Patrick O Donoghue Matt W. Hayward 《Conservation biology》2021,35(1):369-372
58.
Based on the premise that ecosystems with more species will function at more efficient rates, declining biodiversity is expected to alter important ecosystem functions, goods, and services across the globe. However, applicability of this general hypothesis to genetic or clonal richness in assemblages composed of few species is understudied. This illustrates the need to expand the focus of biodiversity-ecosystem-function experiments across all levels of biological diversity (including genetic). To explore this generality, we manipulated intraspecific (clonal) and interspecific (species) richness of a primary consumer, Daphnia, and measured assemblage feeding rate and total resource consumption. Our results showed that greater clonal richness had no effect on Daphnia feeding, and greater species richness decreased feeding-related effects of Daphnia. This suggests that multiclonal Daphnia assemblages may be no more efficient at consuming resources than monocultures, and that monocultures of Daphnia may consume resources more efficiently than more species-rich assemblages. The inhibitory effect of increasing richness observed in this study resulted from chemical and mechanical interference among some of the Daphnia taxa. This suggests that consumer-mediated ecosystem functions could be reduced when assemblages include taxa equipped with adaptations for interference competition. 相似文献
59.
Column Flotation Deinking: State-of-the-art and opportunities 总被引:1,自引:0,他引:1
Subhashini Vashisth Chad P.J. Bennington John R. Grace Richard J. Kerekes 《Resources, Conservation and Recycling》2011,55(12):1154-1177
Flotation is a critical process step for ink removal from recycled paper. Column flotation is a specific form of flotation that has grown in popularity recently. Extensive efforts during the past four decades to improve the flotation deinking operation sought an optimum blend of technological parameters, physico-chemical aspects and economical process conditions. With increasing demand to recover and recycle waste paper due to ecological and economical concerns, there is a need for an improved process and therefore for in-depth understanding of the mechanism and fundamental factors involved in the efficiency and economics of the deinking process. This paper reviews the progress made in the last decade (2000–2010) in deinking hydrodynamics, various measurement techniques, scale-up and design criterion. 相似文献
60.
The equilibrium distributions, between water and coal-tar contaminated sediment, of 16 monocyclic and polycyclic aromatic hydrocarbons were measured and evaluated for consistency with a Raoult's Law-based quantitative relationship. The quantitative relationship calculates the pore water concentration as the product of the aqueous solubility (or for compounds that are solid at room temperature, the aqueous super-cooled liquid solubility) and the mole fraction concentration of the compound within the liquid coal tar. Sediment was collected at five locations at two depths within a 120 m stretch of a river adjacent to a former manufactured gas plant, and all samples contained non-aqueous phase liquid (NAPL) coal tar. Although the amount of coal tar varied between samples by over an order of magnitude, the Raoult's Law-based NAPL-water partition coefficients for each monocyclic or 2- or 3-ring polycyclic aromatic hydrocarbon measured in this study generally varied within a factor of 2 over all sediments. 相似文献