Herbicide dynamics in the Bogue Phalia watershed in the Yazoo River basin of Mississippi.

摘要

A 2-year surface water reconnaissance of the Bogue Phalia in Mississippi, USA, and its tributaries was conducted in 1997 and 1998. Cyanazine and metolachlor in surface water samples were quantified using ELISA. Cyanazine and metolachlor were detected in 101 and 132 of the 160 samples, respectively. Cyanazine concentrations ranged from 0.1 to 2.2 g litre-1, and exceeded the US Environmental Protection Agency lifetime health advisory level (HAL) of 1.0 g litre-1 in 8 samples. However, concentrations never exceeded the HAL for shorter exposure times. Metolachlor concentrations never reached the lifetime HAL of 100 g litre-1. Metolachlor concentrations ranged from 0.1 to 20.6 g litre-1. Metolachlor was detected more frequently and found to be more persistent throughout the growing season than cyanazine. Higher cyanazine and metolachlor concentrations were detected at sampling dates that coincided with herbicide applications. One of the Bogue Phalia's tributaries, Clear Creek, was found to be a point-source of cyanazine for the watershed..