Affiliations: Key Laboratory of Pesticide and Chemical Biology,
Ministry of Education, College of Chemistry, Central China Normal University,
Wuhan 430079, China | College of Agronomy, Henan Agricultural University,
Zhengzhou 450002, China | Pesticides and Environmental Toxicology Research
Institute, Zhejiang University, Hangzhou 310029, China
Abstract: The degradation of imazapyr in non-sterile and sterile soils from
four sampling sites in Zhejiang, China was studied. The results showed that the
half-lives of imazapyr in non-sterile soils were in the range of 30 to 45 d,
while 81 to 133 d in sterile (by autoclaving) soils. It means the rate
constants of imazapyr under non-sterile conditions were 2.3–4.4 times
faster than that under sterile (by autoclaving) conditions, evidently
indicating that the indigenous microorganisms in soil play an important role in
the degradation of imazapyr. The different sterilization methods could result
in different degradation rates of imazapyr. The heat of sterilization of soil
largely decreased the degradation. However, the sterile treatment of soil by
sodium azide had a different effect from that by autoclaving. Further more, the
mechanism was also discussed. Biodegradation in four non-sterile soils
accounted for 62% to 78% of imazapyr degradation. In contrast, less than 39% of
imazapyr degradation was associated with chemical mechanisms. Therefore, the
degradation mechanism was predominantly involved in biology including organisms
and microorganisms in soil. Two imazapyr-degrading bacterial strains were
isolated in enrichment culture technique and they were identified as
Pseudomonas fluorescenes biotype II (ZJX-5) and Bacillus cereus
(ZJX-9), respectively. When added at a concentration of 50 μg/g in mineral
salts medium (MSM), ZJX-5 and ZJX-9 could degrade 81% and 87% imazapyr after 48
h of incubation. For the treatment of incorporation of ZJX-5 or ZJX-9 into
soil, the degradation rate enhanced 3–4 fold faster than that for control
samples, which showed an important value in quick decontamination of imazapyr
in soil.
