|Moorman, Thomas - Tom|
Submitted to: International Symposium on Environmental Aspects of Pesticide Microbiology
Publication Type: Proceedings
Publication Acceptance Date: 7/6/1996
Publication Date: N/A
Technical Abstract: We conducted a series of experiments to determine the relationship between the biodegradation of the herbicides, atrazine and 2,4-D, and the size and structure of soil microbial communities. Experiments were conducted with surface soil, subsoils, and the underlying glacial sediments (sandy alluvium and glacial till) from sites in Iowa and Indiana. Microorganisms rapidly mineralized 100 ng/g concentrations of 2,4-D in surface soils from all sites. Mineralization of 2,4-D occurred (30 to 76%) after lags of 7 to 35 days in approximately 70% of the samples of sandy alluvium collected below 1 m depth. The frequency of adaptation and total 2,4-D mineralization were positively correlated to sand content. In sediments where microbial adaptation did not occur, less than 15% of the 2,4-D was mineralized. In contrast to the alluvial sediments 2,4-D was degraded more slowly in glacial till, with less than 10% of the 2,4-D mineralized in samples from greater than 1 m depth. Populations of 2,4-D-degrading microorganisms were detected in both till and alluvium and adaptation is related to growth of these populations. Our findings suggest that: (1) distinct (size and composition differ) microbial communities exist in the soil, vadose and saturated zones, but herbicide degrading microorganisms are present only at low levels; (2) the biodegradation potential of subsurface sediments (till vs. sandy alluvium) is different; and (3) these differences are possibly related to substrate bioavailability and the ability of specific degrader populations to grow in response to the substrate.