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 an atrazine-exposed Cisne soil. The soil exhibited enhanced atrazine degradation and apparently accumulated cyanuric acid. The soil showed elevated ambient concentrations of NO3-; however NO3- did not suppress atrazine degradation. Atrazine natural attenuation was limited by incomplete distribution through the unsaturated soil matrix. Approximately four moles of inorganic N derived from atrazine were detected for each mole of atrazine carbon mineralized, indicating that at least 80% of the atrazine N was released (less than 20% assimilated). 15N-DNA- SIP experiments were conducted using15N (ring)- and 15N-ethylamino-atrazine. The results of these experiments failed to establish a causal relationship between in-situ atrazine-degradation and enrichment of DNA associated with soil microorganisms. These results are likely due to isotopic dilution, either as a result of insufficient 15N assimilation or competition by other N sources. Further experiments using 13C-ethyl/isoproylamino-atrazine may yet establish the identities of organisms responsible for enhanced natural attenuation exhibited in the Cisne soil.
Shaffer, Elizabeth; Sims, Gerald; Cupples, Alison; Smyth, Charles; Chee-Sanford, Joanne; and Skinner, Andrea
"Atrazine Biodegradation in a Cisne Soil Exposed to a Major Spill,"
International Journal of Soil, Sediment and Water: Vol. 3
, Article 5.
Available at: http://scholarworks.umass.edu/intljssw/vol3/iss2/5