铝矿区复垦土地重金属质量分数特征及潜在生态风险评价

Characteristics and potential ecological risk assessment of heavy metals in reclaimed land of a bauxite mine

复垦土地的质量制约着土地的价值和利用方式,科学的生态风险评价是衡量土壤质量的重要手段,是防控重金属污染的重要依据和前提。为探讨地形坡度对复垦土地重金属分布状况和潜在生态风险的影响,以孝义铝矿复垦10年后的平地、缓坡地和陡坡地耕作层土壤为研究对象,对0～20 cm和> 20～40 cm 2个土层6种重金属(As、Cd、Cr、Cu、Ni和Pb)的质量分数和分布状况进行分析,并进一步用潜在生态风险指数法评估潜在生态风险。结果表明:Cd和Pb质量分数在2个土层均表现为平地>缓坡地>陡坡地,其他元素在0～20 cm没有固定规律。3种地形2个土层中,综合污染程度值在13. 18～14. 92之间,均值为13. 88,污染等级为中等;综合潜在生态风险生态指数在239. 05～275. 57之间,均值为255. 35,风险等级为中等。2个土层主要污染元素为Cd,其次为Pb,其中Cd处于高等潜在生态风险,其余元素为低等潜在生态风险。污染程度和潜在生态风险等级在0～20 cm土层表现为平地>缓坡地>陡坡地,在> 20～40 cm土层为陡坡地>平地>缓坡地。综合分析表明,受人为活动影响,平地和缓坡地中污染重金属元素高于自然恢复状态的陡坡地,地面坡度对重金属质量分数、污染程度和潜在生态风险存在影响,且随着土壤深度的增加坡度的影响在逐渐降低。

[Background]The quality of reclaimed land restricts the value and use models of land.Ecological risk assessment is an important basis for the control and prevention of heavy metal contamination.The object of this paper is to study the content characteristics and potential ecological contamination risk of 6 heavy metals elements in farming soil of Xiaoyi bauxite reclaimed land,which have reclaimed for 10 years in 3 terrains of plain,gentle slopeland,and steep slopeland.[Methods]The soil samples in 0-20 and>20-40 cm layers from plain,gentle slopeland,and steep slopeland were collected.The contents of 6 heavy mental(As,Cd,Cr,Cu,Ni,and Pb)in both 0-20 and>20-40 cm of soil layers were measured using ICP-AES after acid digestion,and further the contents and distribution characteristics were analyzed.Finally,the contamination degrees and potential ecological risks of heavy metals were assessed using Hakanson potential ecological risk index.The data of heavy metal contents were mean values of three repetitions,and the calculation and analysis were conducted using software Excel 2010 and SPSS 13.0.[Results]1)The concentrations of Cd and Pb presented that plain>gentle slopeland>steep slopeland in both of 0-20 cm and>20-40 cm layers,while the other4 metals sbowed no certain change pattern in 0-20 cm.2)At 3 different terrains and 2 soil layers,the degree of contamination ranged in 13.18-14.92,with an average 13.88,which was at medium contamination level.The potential ecological risk index ranged in 239.05-275.57,and average was255.35,which were at a medium risk level.At 0-20 cm soil layer,the degree of contamination and potential ecological risk demonstrated as plain>gentle slopeland>steep slopeland,and as steep slopeland>plain>gentle slopeland in>20-40 cm soil layer.The Cd was the major contamination element and Pb was the second,while Cd at a high and Pb at a medium contamination level.The other 4 elements did not show contaminations and at a low potential ecological risk.[Conclusions]The contamination degree of heavy metals is higher in plain and gentle slopeland than in steep slopeland.As more human impact on plain land and gentle slopeland while steep slopeland is at a nature state,the slope effect on the heavy metal concentrations,contamination degree and potential ecological risk,and the influence gradually decreases with the reduction of slope.