No abstract

The adsorption and desorption of atrazine, and its three metabolites, deethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA), on Levy wetland soil were measured using the batch equilibration technique. Solution concentrations for each chemical were 1.3, 3.8, 6.6, and 13.2 μmol L-1. Four 24-h period desorptions for each concentration were conducted immediately after adsorption. The adsorption of all the chemicals conformed to linear isotherms. Adsorption coefficients decreased in the order HA (109.7) > atrazine (38.6) > DIA (26.3) > DEA (22.1). The organic carbon partition coefficients (K oc) for HA, atrazine, DIA, and DEA were 1500, 440, 290, and 240 L kg-1, respectively. Percent of chemical desorbed was about 29% for DEA, 24% for atrazine, 23% for DIA, and 16% for HA. The slopes of all desorption isotherms were less than their respective adsorption slopes, indicating hysteresis. Atrazine and its metabolites were relatively more strongly adsorbed and the binding was less reversible in the Levy wetland soil than what has been reported for agricultural soils. Keywords: Atrazine; deethylatrazine; hydroxyatrazine

The effectiveness of switchgrass (Panicum virgatum L.) filter strips in removing dissolved atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) and metolachlor (2‐chloro‐N‐2‐ethyl‐6‐methylphenyl‐N‐2‐methoxy‐1‐methylethyl acetamide) in runoff was investigated using aluminum‐tilted beds set at 1% slope, filled with Emporia sandy loam soil (fine‐loamy, siliceous, thermic Typic Hapludults) and planted to switchgrass. Solution containing herbicides, followed by water alone after 2 and 4 wk were applied on the up slope of beds with and without switchgrass. Water samples from surface flow, lateral, and vertical leachates as well as soil samples were analyzed for the two herbicides using a gas chromatograph. Switchgrass filter strips reduced the mass of dissolved atrazine and metolachlor by 52 and 59% from the applied runon, respectively. The bare soil strips removed 41% of atrazine and 44% of metolachlor. Less than 0.5% of the applied herbicide was released by the two water runons 2 and 4 wk after herbicide‐solution application. The average concentrations of both herbicides in surface runoff were greater than in leachate samples. Herbicides were removed by the soil as runon moved through the soil profile. The concentration of either herbicide on the top surface (0–2.5 cm) was greater than in the soil immediately below (2.5–5 cm). Degradation of both herbicides was faster in beds with switchgrass than without. Greater amounts of both herbicides were retained in the first 67‐cm section of beds with the grass than without. Switchgrass helped to remove the herbicides by slowing runoff velocity and increasing their retention by soil.

No abstract