天山土壤微量(类)重金属的来源解析及潜在生态危害评估

Source identification and potential ecological hazards assessment of trace metalloid/heavy metals in the soil of Tianshan Mountains,Xinjiang,China

从天山山地3个区段(巴里坤-伊吾、乌鲁木齐-阿克苏、昭苏-特克斯)采集土壤样品,测定了其中(类)重金属Pb、Ni、Cd、Co、Hg、Cu、Mn、Zn、Cr和As的含量.运用经典统计学与多元统计方法分析了这些(类)重金属的来源;同时采用污染指数法与潜在生态风险指数法,并结合天山及新疆土壤背景值、国家土壤质量标准开展了区域土壤微量(类)重金属生态风险的评价.结果表明:所测10种(类)重金属的平均含量均高于天山或新疆土壤背景值.从变异系数来看,均为中等变异.总体上看,天山山地土壤中10种(类)重金属的含量均较低;主成分分析显示,10种元素可以辨识出2个主成分,主成分1(PC1,包括Cd、Pb、Hg、Mn和Zn)为人为源因子,主成分2(PC2,包括Cu、Ni、Cr、Co和As)为自然源因子.Mn和As在PC1和PC2上均有较大载荷,主要受人为源和自然地质背景的共同控制;污染评价表明,重金属Hg、Cd在天山中部的乌鲁木齐-阿克苏区段、As在天山西部的昭苏-特克斯区段的单因子污染指数(Pi)属于警戒等级,其他均属于安全等级和清洁水平.从综合污染(Pz)指数来看,天山中部乌鲁木齐-阿克苏区段土壤中10种(类)重金属元素的综合污染程度均属于轻度污染,其他两个区段均属于清洁水平;生态风险评估表明,重金属Hg、Cd在天山中部乌鲁木齐-阿克苏区段,As在天山西部昭苏-特克斯区段的潜在生态风险系数(Eir)和生态危害指数(RI)相对较高.

In this study, the contents of ten metalloid/heavy metals （As, Pb, Ni, Cd, Co, Hg, Cu, Mn, Zn and Cr） in soil samples collected from three sections including the central Urumqi- Akesu, eastern Blikun-Yiwu and western Zhaosu-Tekesi in Tianshan Mountains were determined, and their sources were identified by using typical statistical and multivariate statistical methods. The potential ecological risks of these heavy metals were assessed by employing pollution index method, potential ecological risk index and the background values of Tianshan Mountains, and Xinjiang, and also the Second National Standard of the Soil Qualities of China. The results showed that the contents of the heavy metals （Pb, Ni, Cd, Co, Hg, Cu, Mn Zn and Cr） and metalloid As were all higher than the soil background values of the Tianshan Mountain or Xinjiang, and their variation coefficients belonged to the medium variation. In general, the contents of the ten metalloid/heavy metals in the soil of Tianshan Mountains were low. Principal component analysis showed that the ten metalloid/heavy metals could be identified as two principal components, among which PC1 （Cd, Pb, Hg, Mn and Zn） could be seen as ＇human influence sources factor＇, PC2 （Cu, Ni, Cr, Coand As） as ＇natural sources factor＇. Mn and As had larger loads both in PCI and PC2, and they could be co-influenced by human and natural sources. The pollution assessment showed that Hg and Cd in central Urumuqi-Akesu section and As in western Zhaosu-Tekesi section were all at alert lev- el, while the other heavy metals in other sections were all at security level. From the comprehensive pollution indices （Pz） of heavy metals, it was found that the ten metalloid/heavy metals in the soils of central Urumqi-Akesu section were at low pollution level, but those in the other two sections were at clean level. The potential ecological risk assessment showed that the potential ecological risk co- efficient （Er^i） and the ecological damage index （RI） of Hg and Cd in central Urumqi-Akesu section and that of As in western Zhaosu-Tekesi section were relatively high.