不同时空铅锌矿渣中耐受重金属细菌群体的变化

Spatial and temporal changes in colonization of heavy metal-tolerant bacteria in the lead-zinc tailings with different deposited history

利用含不同浓度铅锌的选择平板 ,对堆积时间分别约为 1 0、2 0和 80a的铅锌矿渣堆表层和下层的耐受细菌群体进行了调查。与对照土样相比 ,矿渣堆中细菌总量减少。堆积时间短的矿渣堆 ,细菌数量少 ,上下层数量差异不大 ;堆积时间长的 ,细菌数量较高 ,上层数量比下层大。矿渣堆中有大量耐受铅锌的细菌群体 ,耐受水平越高的群体数量越少。在空间分布上 ,耐受群体主要集中在下层。随堆积时间延长 ,耐受群体比例减少。铅锌对细菌的胁迫效应不同 ,尽管矿渣堆主要表现为铅污染 ,但其中仍有大量耐受Zn2 + 的群体 ,耐受水平达 1 0mmol·L-1 ,没有发现能够耐受如此高浓度Pb2 + 的群体。此外 ,发现有部分细菌的生长依赖于 0 .5mmol·L-1 的Pb2 + 和Zn2 + 。

Culturable heavy metal-tolerant bacteria in 5～10 cm and 25～30 cm layers of three lead-zinc tailings,deposited for about 10,20 and 80 years respectively,were investigated.Comparing with the campus soil,decreased total microbial population and a higher percentage of heavy metal-tolerant microorganisms was found in lead-zinc tailings.In tailings deposited for 10 years,no difference in bacterial population was found between the 5～10 cm layer and the 25～30 cm layer,but in the 20- and 80-year-old tailings,the 5～10 cm layer had 2～3 times the size of bacterial population in the 25～30 cm layer.A large population of heavy metal-tolerant bacteria was found in the lead-zinc tailings.The bacteria with high tolerance were small in size of population.Spatially,tolerant bacteria were mainly distributed in the 25～30 cm layer,however,the proportion of tolerant bacteria decreased with the increasing deposited history.Although these tailings contained a high concentration of soluble lead,but the bacteria tolerant to 10 mmol·L(-1) of zinc were found in three tailings,either in the (5～10) cm or 25～30 cm layers.No bacteria could resist to such a concentration of lead.However,some bacteria were found living on 0.5 mmol·L(-1) of lead and zinc.