|Thurman, Michael - USGS|
|Blanchard, Paul - UMC|
Submitted to: International Association of Environmental and Analytical Chemistry
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 1999
Publication Date: N/A
Technical Abstract: Knowledge of hydroxyatrazine (HA) sorption to soils, and its pattern of stream water contamination suggest that it is persistent in the environment. The primary objective of this research was to measure HA in soils and stream sediments. Soils with different atrazine use histories were collected from four sites, and sediments were collected from an agricultural watershed. All samples were exhaustively extracted with a mixed-mode extractant for HA or 80% aqueous methanol for atrazine, deethylatrazine (DEA), and deisopropylatrazine (DIA). HA concentrations were greater than atrazine, DEA, and DIA in all field soils. Median soil concentrations were: HA, 78 ug/kg; atrazine, 9.9 ug/kg; DEA, 3.4 ug/kg; and DIA, 1.8 ug/kg. In sediments, HA was also present at higher concentrations than atrazine, DEA, and DIA. Concentrations of HA in sediments ranged from 11 to 96 ug/kg with a median concentration of 14 ug/kg. Correlations of HA Aand atrazine concentrations to soil properties indicated that HA levels in soils were controlled by sorption of atrazine. Since atrazine hydrolysis is known to be enhanced by sorption and pH extremes, soils with high organic matter and clay content and low pH will result in greater atrazine sorption and subsequent hydrolysis. In sediments, significant correlations of HA concentrations to organic matter, pH, and cation exchange capacity suggested that mixed-mode sorption (i.e., binding by cation exchange and hydrophobic interactions) controlled its levels. The presence of HA at the levels observed support existing hypotheses regarding its transport in surface runoff. These results also indicated an additional risk factor associated with atrazine usage is the potential impact of sediment-bound HA on aquatic ecosystems.