Microbial Response Effects of Thermal Desorption in Organochlorine Pesticide-contaminated Soil.

Hexachlorocyclohexanes, the organochlorine pesticide, can have toxic response effects to the sensitive microbial flora in soil, resulting in changes of the type and numbers of the sensitive microbial flora. This paper analyzed the response and changes of microorganisms in HCHs polluted soil and the soil after the corresponding ex-situ thermal desorption remediation at different concentration levels, and screened out the microorganisms that can be used as indicator organisms in HCHs contaminated soil. In this paper, the clean soil samples (CK), soil samples, contaminated by HCHs of different levels (H1, H2 and H3) and the soil samples after being remediated (AR) were used as test soil samples. Based on the number of bacteria and the biological indicators of diversity, the differences between soils with different contaminated concentrations and the microbes before and after remediation are explored. The results of the studies showed that compared with CK, the number of bacteria in gradient contaminated soil H1, H2 and H3 was reduced by 95.31%, 94.17% and 94.06%, respectively (P<0.05), and the number of bacteria in AR recovered to some extent but was still notably lower than that of CK, 98.86% lower (P<0.05). There were significant differences in the bacterial diversity of clean soil, contaminated soil and the soil after being remediated. In H3 soil, the characteristic bacteria Proteobacteria and the characteristic bacteria Pseudomonas were significantly enriched, and the proportion reached 99.43% and 97.97%, respectively and the other species'proportion below 1%. Compared with H3, the microbial species composition in AR had been restored to a certain extent, and the diversity of community composition increased, but it was still lower than that of uncontaminated soil in the short term. The average relative abundance of Methylomirabilota, Nitrospira and Planctomycota in clean soil was significantly lower than that in contaminated soil, and in the most contaminated soil H3 their relative abundance was equal to zero, which implied that the above three species bacteria, being rather sensitive to HCHs pollution, could be used as HCHs pollution-sensitive indicator bacteria, and as a new auxiliary detection method. The analysis of environmental factors showed that HCHs noticeably exerted impacts on the bacterial community structure of soil, especially on that of the group H3. [ABSTRACT FROM AUTHOR]