菲和铬(Ⅵ)单一及复合暴露对土壤微生物多样性的影响

有机物和重金属已成为我国土壤环境中常见的2类污染物质,二者间复合污染引起的土壤生态环境风险不容忽视。本研究以多环芳烃模式物菲和典型重金属铬(VI)作为受试物质,采用PCR-DGGE分子指纹图谱技术,探讨这2种污染物单一及复合暴露对土壤微生物群落多样性的影响,并选用主成分分析、聚类分析和戴斯系数3种算法对微生物群落相似性进行了比较。结果表明,在暴露实验第1天,菲单一暴露低浓度组中微生物群落相似性产生了极为明显的变化,而到第7天时,菲和铬(VI)单一暴露高浓度组均对微生物群落结构相似性产生最大程度的影响;采用香农指数法评价微生物群落的多样性,发现在暴露实验第7天,菲和铬(VI)单一暴露高浓度组对微生物群落多样性的影响比复合暴露高浓度组更强,二者复合暴露的相互作用方式表现为拮抗效应。本研究证明低浓度菲短期暴露的效应高于高浓度暴露结果,因而多环芳烃菲自身及其在复合暴露中所扮演的角色尤其值得关注。

Effects of Single and Combined Exposure to Phenanthrene and Chromium (Ⅵ) on Microbial Diversity in Soils

Organic pollutants and heavy metals are ubiquitously detected in Chinese soils, and the combined contaminative effect on the ecological risks of soil environment is of great concern. Individual and combined exposure to typical PAH pollutants phenanthrene and heavy metallic pollutants chromium(VI) was conducted to investigate their effect on the diversity of soil microbial community composition. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplicons of 16S rDNA sequence of microorganisms in soils was used in this work. The similarity of microbial community structure was assessed using primary component analysis, clustering analysis, and Dice coefficients, respectively. Individual exposure to low-concentration of phenanthrene resulted in a significant impact on community similarity at day 1; individual exposure to phenanthrene and chromium(VI) with high-concentration manifested the maximum effect on community similarity at day 7. Shannon index was utilized to evaluate the species diversity, and the results showed that individual exposure to either phenanthrene or chromium(VI) with high-concentration resulted in greater effects than that of combined exposure to phenanthrene and chromium(VI) at day 7. Antagonism effect was identified within the combined exposure process. Our results revealed that the short-term exposure to phenanthrene with lower concentration led to greater effect than that of with higher concentration. Particular concern should be addressed to PAH compound per se, e.g. phenanthrene, and its potential effect in combined exposure processes.