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Atrazine Mineralization in Laboratory‐Aged Soil Microcosms Inoculated with s‐Triazine‐Degrading Bacteria
Author(s) -
Radosevich Mark,
Traina Samuel J.,
Tuovinen Olli H.
Publication year - 1997
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1997.00472425002600010030x
Subject(s) - atrazine , microcosm , mineralization (soil science) , chemistry , soil water , environmental chemistry , bioavailability , tillage , zoology , pesticide , agronomy , soil science , biology , environmental science , bioinformatics
An atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine)‐mineralizing bacterial isolate was used as a biological probe to investigate the effects of atrazine residence time on subsequent bioavailability and biodegradatlon. [U‐ 14 C‐ring]‐atrazine was reacted with sterile soils collected from long‐term, experimental, no‐till and conventional‐tillage plots. After aging for 1 d to 3 mo, the atrazine‐treated soils were inoculated with the bacterium (7 × 10 7 cells g −1 ) and 14 CO 2 evolution was measured with time. Mineralization of [U‐ 14 C‐ring]‐atrazine could be described with a first‐order rate equation in soils from both tillage systems. Atrazine was rapidly mineralized in no‐till soil aged for 1 d, with 50% of the initial radioactivity recovered as 14 CO 2 within 2 d after inoculation. Both the mineralization rate constants ( k ) and the extent of mineralization ( P max ) decreased with soil residence time. conventional‐till soil, no significant aging effect was observed for soil reacted for 7 d; however, both the k and P max , values decreased with extended aging. Measurements of soil solution‐phase atrazine were determined by high‐pressure liquid chromatography analysis after solutions were retrieved by centrifugation. In no‐till soil, the observed degradation rates were 38 to 227 times slower than those predicted on the basis of solution‐phase experiments. The respective rates were 25 to 63 times slower in the conventional‐till soil. The results suggest that a significant fraction of the solution‐phase atrazine was sequestered from microbial attack and that the unavailable fraction increased with soil residence time.