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Impact of Land Use on Microbial Transformations of Atrazine

Dep. of Environmental Health Sciences and Marine Science Program Columbia, SC 29208;

Dana C. Cresci

Dep. of Environmental Health Sciences, Univ. of South Carolina, Columbia, SC 29208.

^* Corresponding author (aelionm{at}sc.edu).

ABSTRACT

Atrazine has been one of the most heavily applied preemergent herbicides in the USA, and with alachlor, represents more than 45% (4.082 x 10⁶ kg) of total herbicide application in coastal U.S. counties. Several studies using bacterial isolates or mixed cultures have demonstrated that mineralization of atrazine [6-chloro-N-ethyl-N'-(1-methyl-ethyl)-1,3,5-triazine-2,4-diamine] is rapid, yet in soil microcosms mimicking in situ conditions, mineralization accounts for <1% of the applied compound. This study examined the impact of land use on atrazine biotransformation in sediments from three coastal sites, all in an historically agricultural area that has undergone extensive development in recent years. Production of ¹⁴CO₂ was monitored in sediment incubated with [U-¹⁴C]-atrazine from a forested preserve, a suburban neighborhood and a golf course, all of which were previously impacted by agriculture. Solid phase extraction of both liquid and sediment fractions was carried out over time to determine whether metabolic transformation of atrazine occurred. Results indicated that mineralization represented <1% of the atrazine added, and ring carbons were not assimilated into cellular biomass. Production of ¹⁴C-transformation products was a significant portion of the total ¹⁴C-atrazine added at all sites, but was greatest in the golf course sediments. This may be attributed to several environmental conditions of land development such as the preexposure of the golf course bacteria to frequent pesticide applications, and 100% sand content of the golf course sediment vs. higher clay and organic C content at the other two sites, causing less sorption and more bioavailability of atrazine.