The activities of microbial communities in Huixian Wetland sediments under the interactive toxicity of Cu(II) and pentachloronitrobenzene

The unbonded Cu(II) and pentachloronitrobenzene (PCNB) in the sediment of Huixian Wetland were determined. Their toxic effects on the microbial communities in the sediment were explored by treating the sediment with Cu(II) (CuSO4·5H2O) and PCNB individually or jointly. The Complexation/Transformation ratios of these two toxicants resulted from the microbial communities were also investigated. Tow groups of sediments were classified according to the content of Cu(II) and PCNB in it, namely, higher level of Cu(II) and PCNB detectable for the first one (G1), which was collected from the lakes located at lower reaches of the water flow in the wetland, the other one with low level of Cu(II) and PCNB undetectable (G2), which was collected from the sites of upper flow of water, the foremost outlet of the subterranean streams flowed in to the wetland. The Cu(II) and PCNB content in the wetland sediments were as high as 185.63 ± 16.2 μg·g− 1 and 0.17 ± 0.07 μg·g− 1for the G1, but for the G2, 17.4 ± 1.2 μg·g− 1 and undetectable, respectively. The 40 h IC50 values for the microbial communities of Cu(II) and PCNB, as treated with Cu(II) and PCNB individually, were 3572 μg·g− 1 and 8 μg·g− 1 for the G1, 3053 μg·g− 1 and 4.5 μg·g− 1 for the G2, respectively. These values, when the microbial communities were treated with Cu(II) and PCNB simultaneously, increased to 7520 μg·g− 1 and 10.1 μg·g− 1 for the G1 and for the G2 3196 μg·g− 1 and 8.1 μg·g− 1, respectively. The 40 h additivity indexes (AI) for the interactive toxicity of Cu(II) and PCNB on the microbial communities in the sediment of G1 and G2 were − 0.26 and − 1.82, respectively. These results indicated that the microbial communities in Huixian Wetland that previously exposed to higher level of Cu(II) and PCNB had a higher tolerance to the corresponding toxicants, and the interactive toxicity of Cu(II) and PCNB was antagonistic under the testing conditions. Furthermore, the microbial communities in the sediment of G1 generally showed higher Cu(II) and PCNB Complexation/Transformation ratios against its counterpart in the G2, no matter Cu(II) and PCNB stressed separately or together. Moreover, the correlations of added doses of pollutants and microbial communities activities in the sediment were discussed. The conclusion were that microbial communities in the sediment of Huixian Wetland had a higher tolerance against Cu(II) but lower against PCNB, and the contents of the later in this sediment might have approached to the dose which the microbial communities could be furthest tolerable.