Glyphosate, Other Herbicides, And Transformation Products In Midwestern Streams, 2002

The use of glyphosate has increased rapidly, and there is limited understanding of its environmental fate. The objective of this study was to document the occurrence of glyphosate and the transformation product aminomethylphosphonic acid (AMPA) in Midwestern streams and to compare their occurrence with that of more commonly measured herbicides such as acetochlor, atrazine, and metolachlor. Water samples were collected at sites on 51 streams in nine Midwestern states in 2002 during three runoff events: after the application of pre-emergence herbicides, after the application of post-emergence herbicides, and during harvest season. All samples were analyzed for glyphosate and 20 other herbicides using gas chromatography/mass spectrometry or high performance liquid chromatography/mass spectrometry. The frequency of glyphosate and AMPA detection, range of concentrations in runoff samples, and ratios of AMPA to glyphosate concentrations did not vary throughout the growing season as substantially as for other herbicides like atrazine, probably because of different seasonal use patterns. Glyphosate was detected at or above 0.1 μg/l in 35 percent of pre-emergence, 40 percent of post-emergence, and 31 percent of harvest season samples, with a maximum concentration of 8.7 μg/l. AMPA was detected at or above 0.1 μg/l in 53 percent of pre-emergence, 83 percent of post-emergence, and 73 percent of harvest season samples, with a maximum concentration of 3.6 μg/l. Glyphosate was not detected at a concentration at or above the U.S. Environmental Protection Agency’s maximum contamination level (MCL) of 700 μg/l in any sample. Atrazine was detected at or above 0.1 μg/l in 94 percent of pre-emergence, 96 percent of postemergence, and 57 percent of harvest season samples, with a maximum concentration of 55 μg/l. Atrazine was detected at or above its MCL (3 μg/l) in 57 percent of pre-emergence and 33 percent of postemergence samples

Laboratory analyses of the potential toxicity of sediment-associated polydimethylsiloxane to benthic macroinvertebrates

Polydimethylsiloxane (PDMS) is widely used in a number of industrial processes and consumer products that result in down-the-drain disposal. The log p value for the PDMS used in the present study was 10, and the vapor pressure and water solubility values were below detection limits. These physicochemical characteristics and a measured degradation rate of 3fter six months in moist soils suggest that PDMS may accumulate in aquatic sediments. Sediment toxicity tests with the amphipod Hyalella azteca and with larvae of the midge Chironomus tentans were used to assess the potential for toxicity of PDMS-amended sediments to benthic invertebrates in short-term (10-d) and whole-life-cycle (28 d for H: azteca, 50-65 d for C. tentans) exposures. Endpoints for short-term tests included survival and growth, while life-cycle assays considered survival, growth, reproduction, and, for C. tentans only, emergence. Short-term and life-cycle exposures to concentrations of ≥ 1,000 mg PDMS/kg sediment (dry wt) indicated that PDMS will not reduce survival, growth, or reproduction in H. azteca or C. tentans

Receptor-mediated potencies of polycyclic aromatic hydrocarbons in urban sediments: comparisons of toxic equivalency risk assessment

The Klip River, flowing through South Africa’s most populated urban area—Soweto and Lenasia—is subject to various pollution and anthropogenic influences, including great concentrations of polycyclic aromatic hydrocarbons. The aims were to determine the aryl-hydrocarbon receptor-mediated potencies of the 16 priority polycyclic aromatic hydrocarbons in sediments of the Klip River, using chemical- and bio-analytical assessments of hazard, and to compare these results with international sediment quality guidelines. Sediment samples were collected from nine sites during the dry seasons of 2013 and 2014. Two sets of toxic equivalents were calculated from analytically obtained polycyclic aromatic hydrocarbon concentrations using: (1) 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalency factors and (2) relative potency factors for fish. The fraction of the sediment extracts containing polycyclic aromatic hydrocarbons was assayed with the H4IIE-luc reporter gene bio-assay, and the aryl-hydrocarbon receptor potency expressed as bio-assay equivalents. The bio-assay equivalents and tetrachlorodibenzo-p-dioxin equivalency factors were compared to Canadian sediment quality guidelines and of the three approaches, the bio-assay equivalents and the relative potency factors for fish proved the most protective. Results of this study are proof of the utility of combining biological analysis with instrumental analysis when predicting hazard. Even though there were instances where the bio-assay equivalents were orders of magnitude greater than the tetrachlorodibenzo-p-dioxin equivalency factors, the results still showed similar trends. It was concluded that hazard from aryl-hydrocarbon receptor-mediated potency to adversely affect aquatic organisms in the Klip River was relatively great, which indicated the need for further investigation into possible mitigation