复垦矿区重金属对土壤微生物群落的影响

Effects of Heavy Metals on Soil Microbial Community in Reclaimed Mining Area

为研究矿区复垦土壤重金属污染水平与土壤微生物群落多样性的关系,以及重金属污染对人体的潜在健康风险,该文以淮北朔里矿周边土壤为研究对象,采用高通量测序方法,研究土壤微生物群落结构的变化,并分析其结构与重金属污染及土壤环境要素的相关性,并对土壤重金属污染进行健康风险评价。结果表明:(1)朔里矿周边土壤重金属含量普遍偏高,内梅罗综合污染指数属于轻度或中度污染,主要污染物为Cd,平均含量为0.27 mg/kg;(2)复垦土壤pH值、有机质、硝态氮以及有效磷含量明显高于未复垦土壤含量,有效钾含量为复垦土壤低于未复垦土壤,氨氮与电导率则无显著差别;(3)高通量测序分析结果显示,复垦土壤与未复垦土壤细菌群落结构有显著差异。各样点中变形菌门丰度最大,未复垦土壤中变形菌门丰度略小于复垦土壤,酸杆菌、浮霉菌、蓝细菌则完全相反,同时在复垦土壤中发现了少量的NC10,该菌种在未复垦土壤中几乎没有。此外,Alpha指数显示未复垦土壤和复垦土壤的群落丰富度和群落多样性略有差异,但不显著。冗余分析表明,丰度较高的变形菌(Proteobacteria)、放线菌(Actinobacteria)、蓝细菌(Cyanobacteria)等与重金属之间呈负相关,酸杆菌(Acidobacteria)和其他细菌与重金属呈正相关,pH值、有效钾、硝态氮、有机质与重金属呈负相关,氨氮与重金属呈正相关;(4)矿区未复垦地与已复垦地非致癌风险儿童明显大于成人,As和Cd对儿童的非致癌风险明显。未复垦地的非致癌风险明显大于已复垦地,但两者的非致癌风险均未超过阈值,对儿童和成人的潜在健康风险都处于可接受水平。综上所述,土壤重金属含量增加会影响土壤微生物群落结构,土壤复垦可以改善土壤质量,但存在的潜在致癌风险,应引起足够的重视。

In order to study the relationship between the pollution level of heavy metals and the diversity of soil microbial community,and the potential health risk of heavy metals pollution to human body,the soil around Shuoli mine in Huaibei was collected as the research object.The high-throughput sequencing method was used to study the change of soil microbial community structure.The correlation among the metal pollution,soil environmental factors and microbial community were analyzed.The USEPA recommended health risk assessment model was used to evaluate heavy metal pollution.The results show that according to Nemerow integrated pollution index,several samples had high heavy metal concentration,belonging to the slight and moderate pollution level.The main pollutant was Cd,and its average content was 0.27 mg/kg.The values of soil pH,organic matter,nitrate nitrogen and Olsen-P in the reclaimed soil were obviously higher than the contents in the un-reclaimed soil.On the other side,the available potassium content was much higher in the un-reclaimed soil,while ammonia nitrogen and EC showed no significant difference between the reclaimed and un-reclaimed soil.High-throughput sequencing results indicated that there were significant differences between the bacterial structure of the reclaimed soil and the un-reclaimed soil.The Proteobacteria was the dominant phylum in all samples,but its abundance in the un-reclaimed soil was slightly less.The abundance of Actinobacteria,Planctomycetes,Cyanobacteria in the un-reclaimed soil were higher.At the same time,a slight amount of NC10 was found in the reclaimed soil,which scarcely existed in the un-reclaimed soil.Besides,Alpha diversity index showed that there was a slightly but not significant difference of Chao1 index and Shannon index between the un-reclaimed soil and reclaimed soil.Moreover,the RDA analysis showed that phyla with high abundance such as Proteobacteria,Actinobacteria,Bacteroidetes,had negative correlation with the heavy metal content,while Acidobacteria and others showed the positive correlation.Except the ammonia nitrogen content,the physicochemical properties showed negative correlation with soil heavy metal content.The non-carcinogenic risk of children in the non-reclaimed land and reclaimed land was significantly higher than that of adults,while the non-carcinogenic risk of As and Cd to children was significant.The non-carcinogenic risk of uncultivated land was significantly higher than that of reclaimed land,whereas the noncarcinogenic risk of both land does not exceed the threshold value.Moreover,the potential health risk to children and adults was at an acceptable level.Therefore,it might be concluded that high heavy metal concentration could significantly influence the soil microbial community structure,while land reclamation could improve the soil quality.But it should pay more attention to potential carcinogenic risk.