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BACKGROUND: Glyphosate [ N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops and is heavily used on soybeans, corn and cotton. Glyphosate is used in almost all agricultural areas of the United States, and the agricultural use of glyphosate has increased from less than 10 000 Mg in 1992 to more than 80 000 Mg in 2007. The greatest intensity of glyphosate use is in the midwestern United States, where applications are predominantly to genetically modified corn and soybeans. In spite of the increase in usage across the United States, the characterization of the transport of glyphosate and its degradate aminomethylphosphonic acid (AMPA) on a watershed scale is lacking. RESULTS: Glyphosate and AMPA were frequently detected in the surface waters of four agricultural basins. The frequency and magnitude of detections varied across basins, and the load, as a percentage of use, ranged from 0.009 to 0.86% and could be related to three general characteristics: source strength, rainfall runoff and flow route. CONCLUSIONS: Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil. Copyright © 2011 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This is the first report on the ambient levels of glyphosate, the most widely used herbicide in the United States, and its major degradation product, aminomethylphosphonic acid (AMPA), in air and rain. Concurrent, weekly integrated air particle and rain samples were collected during two growing seasons in agricultural areas in Mississippi and Iowa. Rain was also collected in Indiana in a preliminary phase of the study. The frequency of glyphosate detection ranged from 60 to 100% in both air and rain. The concentrations of glyphosate ranged from <0.01 to 9.1 ng/m and from <0.1 to 2.5 µg/L in air and rain samples, respectively. The frequency of detection and median and maximum concentrations of glyphosate in air were similar or greater to those of the other high-use herbicides observed in the Mississippi River basin, whereas its concentration in rain was greater than the other herbicides. It is not known what percentage of the applied glyphosate is introduced into the air, but it was estimated that up to 0.7% of application is removed from the air in rainfall. Glyphosate is efficiently removed from the air; it is estimated that an average of 97% of the glyphosate in the air is removed by a weekly rainfall ≥30 mm. Environ. Toxicol. Chem. 2011; 30:548-555. © 2011 SETAC [ABSTRACT FROM AUTHOR]

A method to analyze haloacetic acids (HAAs) in drinking water was developed using a capillary electrophoresis (CE) ion analyzer for analyte separation and detection. The effects of background electrolyte (BGE) composition, sample injection approach, and on- and off-capillary preconcentration techniques on HAA peak resolution and method sensitivity were evaluated. The recommended BGE consists of 25 mM phosphate buffer at pH 5.7 with 1 mM tetradecyltrimethylammonium hydroxide as the electroosmotic flow modifier. Aqueous samples were preconcentrated using solid-phase extraction (SPE) and then loaded onto an extended light path capillary (75-µm inside diameter × 56-cm effective length) using pressure injection (50 mbar for 12 s). The estimated method detection limits were in the range of 1.5-3.5 µg/L The SPE/CE method was used to analyze ambient and spiked water samples from a water distribution system, and results were in good agreement with those using US Environmental Protection Agency method 552.2. The main advantage of the SPE/CE method over the currently approved HAA analysis methods is that it does not require HAA derivatization, which involves potentially hazardous chemicals and conditions. Disadvantages of the SPE/CE method are that it does not offer a significant time savings (because of the need for off-capillary sample preconcentration) and chlorodibromoacetic acid could not be quantified because of interference from a contaminant peak. [ABSTRACT FROM AUTHOR]

Focuses on the detection of the triazine herbicide, Prometon in bodies of water in the United States. Amounts of the herbicide detected from groundwater and drinking water sources; Relevance of the detection to the chemical's use practices and predicted environmental behavior.

Selenium status was explored by investigating effects of a 60-d Se supplementation with DL-selenomethionine (100 µg Se/d) in a group of 10 adults(plasma Se levels, 0.76-1.33 µmol/L). Plasma, erythrocyte, and urinary Se and activities of glutathione peroxidase (GSH Px) in plasma, erythrocytes, and platelets were measured before intervention and after 5, 15, 30, 45, and 60 d. A placebo was given to six adults. Plasma and urinary Sc were the most sensitive indices to Se exposure. Sc in plasma increased steadily during the course of the study whereas urinary Se reached a plateau between 30 and 60 d. By contrast erythrocyte Se did only change after 45 d. Enzyme in plasma and erythrocytes did not respond whereas platelet GSH Px did. The plateau of activity that was observed after 15 d for plasma Se in the range 1.40-1.50 µmol/L could mean that the Sc status is insufficient for an optimal function of GSH Px and implies that dietary intake in Belgium (< 50-60 µg Se/d) is not adequate. [ABSTRACT FROM AUTHOR]

Widespread deployment of sensors that measure river nitrate (NO3−) concentrations has led to many recent publications in water resources journals including review papers focused on data quality assurance, improved load calculations, and better nutrient management. The principal objective of this study is to review and synthesize studies of high‐frequency NO3− data that have aimed to improve understanding of the hydrologic and biogeochemical processes underlying episodic, diel, and long‐term stream NO3− dynamics. Investigations have provided unprecedented detail on hysteresis and flushing patterns during high flow, seasonal variation during baseflow, and responses to multiyear climate variation. Analyses of high‐frequency data have led to notable advances in understanding how climate variation affects spatial and temporal NO3− patterns, especially dry–wet cycles and antecedent moisture. Further advances have been limited by few investigations that include high‐frequency measurements outside the channel and the short duration of many records. High‐frequency data for multiple constituents have provided new insight to the relative roles of hydrology and biogeochemistry as highlighted by studies of the roles of autotrophic uptake, denitrification, riparian evapotranspiration, and temperature‐driven changes in viscosity as drivers of diel patterns. Comparisons of short duration high‐frequency data with long duration low‐frequency data have described similarities and differences in concentration–discharge patterns and highlighted the role of legacy stores. Investigators have applied innovative analysis approaches not previously possible with low‐frequency or temporally irregular data. Future availability of long duration high‐frequency data will provide new insight to processes, resulting in improved conceptual models and a deeper understanding of the role of climate variation. This article is categorized under: Science of Water > Water QualityScience of Water > MethodsWater and Life > Nature of Freshwater Ecosystems [ABSTRACT FROM AUTHOR]

Background Metolachlor [(RS)-2-Chloro- N -(2-ethyl-6-methyl-phenyl)- N -(1-methoxypropan-2-yl)acetamide] and two degradates (metolachlor ethane-sulfonic acid and metolachlor oxanilic acid) are commonly observed in surface and groundwater. The behavior and fate of these compounds were examined over a 12-year period in seven agricultural watersheds in the United States. They were quantified in air, rain, streams, overland flow, groundwater, soil water, subsurface drain water, and water at the stream/groundwater interface. The compounds were frequently detected in surface and groundwater associated with agricultural areas. A mass budget approach, based on all available data from the study and literature, was used to determine a percentage-wise generalized distribution and fate of applied parent metolachlor in typical agricultural environments. Results In these watersheds, about 90% of applied metolachlor was taken up by plants or degraded, 10% volatilized, and 0.3% returned as rainfall. One percent was transported to surface water, while an equal amount infiltrated into the unsaturated zone soil water. < 0.02% reached the groundwater. Subsurface flow paths resulted in greater degradation of metolachlor because degradation reactions had more time to proceed. Conclusions An understanding of the residence times of water in the different environmental compartments, and the important processes affecting metolachlor as it is transported along flowpaths among the environmental compartments allows for a degree of predictability of metolachlor's fate. Degradates with long half-lives can be used (in a limited capacity) as tracers of metolachlor, because of their persistence and widespread occurrence in the environment. [ABSTRACT FROM AUTHOR]