杀虫剂类POPs对土壤中微生物群落多样性的影响

Effects of organochlorine pesticides on soil microbial community functional diversity

农药类持久性有机污染物(POPs)如DDT和HCH在我国2 0世纪5 0年代到80年代曾广泛使用,在停止使用2 0 a后,在土壤中仍然可以检测到DDT和HCH的残留。利用BIOL OG微平板研究土壤微生物群落功能多样性,意在反映有机氯杀虫剂类POPs对土壤微生物群落多样性的影响。结果表明,加了HCH后土壤微生物群落的颜色平均变化值(AWCD)的变化速度和最终能达到的AWCD值要高于空白土壤,并且随着农药浓度的加大,AWCD值的变化速率也越来越快,最终能达到的最大值也呈比例增大。加了DDT后的土壤与空白土壤的AWCD变化速度和程度相差不大。方差分析结果表明:空白土壤、HCH0 .5mg/kg、HCH1.5 mg/kg各处理间土壤的AWCD值有显著性差异(p<0 .0 1) ,空白土壤、DDT0 .5 m g/kg、DDT1.5 m g/kg各处理间土壤的AWCD值达不到显著性差异的水平(p>0 .0 5 ) ,表层土壤的AWCD值要高于第2层土壤(p<0 .0 1)。从多样性指数的变化来看,当加入到土壤中的DDT和HCH含量稍低时,微生物会利用农药为碳源进行分解作用,从而刺激了微生物的生长,这时表现出丰富度、均匀性和多样性都呈增长趋势。但当农药的浓度进一步加大时,反而会抑制某些种的微生物生长,另外一些种则对加入到土壤中的农药有一定的耐受性,从而表现出群落的均匀性下降,而丰富度升高。

Organochlorine pesticides such as DDT and HCH were used extensively in China from the 1950s to the 1980s. Although their use was banned in 1983, their residua in soil are still detectable in many regions today. Pesticides should be generally toxic only to the target organisms. However, this is rarely the case. Some microbial groups are able to use an applied pesticide as a source of energy and nutrients, whereas the pesticide may be toxic to other microbial organisms. Because microbial groups react differently to different pesticides, information concerning their functional diversity (metabolic potential) is essential for understanding the role of microbial communities in different environments. BIOLOG bacterial identification system plates were used to assess the effects of organochlorine pesticides (DDT and HCH) on soil microbial community. The effects of pesticides to microbial community were expressed in terms of Average Well Color Development (AWCD) and Community Diversity Indices. The results showed significant differences in AWCD among treatments of control soil, HCH 0.5mg/kg soil, and HCH 1.5mg/kg soil (p<0.01), but no significant differences among treatments of control soil, DDT0.5mg/kg soil, and DDT 1.5mg/kg soil (p>0.05). AWCD values of topsoil were also greater than those of plough horizon (p<0.01). The abundance, diversity and evenness of soil microbial community were increased with organochlorine pesticides added in soil. While the results for DDT were similar to those for HCH, there were much lower. Although the use of BIOLOG for microbial identification was subject to the same limitations as traditional isolate characterization using agar plates, it proved to be a rapid and reproducible method of detecting relative change in microbial communities. The application of the community-level approach to assays of microbial function would provide a more sensitive and ecologically meaningful measure of heterotrophic microbial community structure.