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United States Department of Agriculture

Agricultural Research Service

Title: Enhanced Atrazine National Attenuation in Agricultural Soil Exposed to a Major spill

item Sims, Gerald
item Shaffer, Elizabeth

Submitted to: International Conference on Soils, Sediments and Water
Publication Type: Abstract Only
Publication Acceptance Date: 9/17/2007
Publication Date: 10/15/2007
Citation: Sims, G.K., Shaffer, E.A. 2007. Enhanced Atrazine National Attenuation in Agricultural Soil Exposed to a Major spill [abstract]. International Conference on Soils, Sediments and Water. Available:

Interpretive Summary:

Technical Abstract: Conventional soil tests, culture-based microbial methods, and the novel method of 15N-DNA stable isotope probing (SIP) were employed to illustrate atrazine biodegradation as related to the physiochemical properties of a Cisne soil from a major atrazine spill site. When compared to five reference soils in our laboratory as well as previous reports in the literature, this soil appeared to exhibit enhanced atrazine degradation, and was thus a good candidate for natural attenuation. Mineralization kinetics in the Cisne soil underestimated the rate of atrazine dissipation demonstrated by the accumulation of several metabolites. The soil showed high ambient concentrations of NO3-, either from excess fertilization or mineralization of atrazine N; however the presence of NO3- did not suppress atrazine degradation. Instead, natural attenuation of atrazine appeared to be primarily limited by incomplete distribution of the compound through the unsaturated soil matrix. Direct plating experiments from the Cisne soil isolated an atrazine-degrading microorganism, ES-1. Analysis of the 16S rRNA gene sequences from the isolate confirmed that ES-1 is closely related (99%) to Arthrobacter sp, a genus containing other known atrazine-degrading isolates. In pure culture the isolate rapidly converted atrazine to cyanuric acid. Accumulation of this product was consistent with metabolites accumulated in the Cisne soil, suggesting that isolate ES-1 was a critical element in the microbial community influencing in-situ remediation of atrazine. To verify this theory, 15N- SIP experiments were conducted using 15N-ethylamino-atrazine. The results of these experiments failed to establish a causal relationship between in-situ atrazine-degradation and ES-1 enrichment; however these inconclusive results are likely due to isotopic dilution. Further experiments using 13C-ethyl/isoproylamino-atrazine (to increase the sensitivity of the SIP technique) may yet verify a link between ES-1 and the enhanced natural attenuation exhibited in the Cisne soil.

Last Modified: 06/21/2017
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