黑色岩系地质高背景区土壤锌富集特征与环境活性

Accumulation and Environmental Availability of Zinc in Soils from a High Geological Background Area Underlain by Black Shale

锌(Zn)既是生物体必需元素又是有害元素,在复合污染的情况下,Zn在植物吸收、转运和富集镉的过程中发挥着重要作用。以往研究主要关注镉的活性,忽略了Zn的环境活性。基于此,本研究以黑色岩系地质高背景区自然富Zn土壤为对象,重点研究了土壤Zn的活性态和潜在活性态,讨论了Zn活性的影响因素和环境意义。结果表明,研究区土壤Zn富集,平均含量可达457 mg/kg,80%的土壤样品超过我国农用地土壤污染风险筛选值。CaCl_(2)提取态Zn含量平均值为0.92 mg/kg,平均提取率仅为0.26%,说明研究区土壤Zn的生物活性低,且随着pH升高而降低。EDTA提取态Zn的平均含量为12.7 mg/kg,平均提取率为2.74%,潜在有效态比例也较低。活性态在潜在活性态中占比为7.63%,活化潜力较大,且随着土壤pH的升高而降低。研究区土壤溶液中Zn∶Cd比较低,可能有利于植物对镉的吸收。开展土壤Zn活性的研究,对理解复合污染区土壤镉的活性变化及调控具有重要意义。

Zinc(Zn)is an essential element and is toxic at high concentration.Zinc plays a vital role in the processes of plant uptake,translocation and accumulation of Cd under Cd-Zn combined contamination.However,previous studies usually focused on the mobility of Cd and ignored the environmental availability of Zn.Therefore,this study collected naturally occurring Zn-rich soils from a high geological background area underlain by black shale,and quantified the mobile and mobilizable pools of Zn,and also investigated the factors influencing the environmental availability of Zn.The results showed that soils from the study area had an average Zn content of 457 mg/kg,with about 80%of samples exceeding the risk screening values of Chinese agricultural soils.The average content of CaCl_(2) extractable Zn,which represent the mobile pool,was 0.92 mg/kg,presenting 0.26%of total Zn.Mobile Zn decreased with increased soil pH.The average content of EDTA extractable Zn,which represent the mobilizable pool,was 12.7 mg/kg,presenting 2.74%of total Zn.Mobile Zn accounted for 7.63%of the mobilizable fraction,indicated the potential of Zn mobility,and the mobility increased with decreased pH.Soils from the study area had low Zn∶Cd molar ratio,which may favor the uptake of Cd by plants.The finding of this study is important for understanding and regulation of Cd availability in Zn-Cd contaminated soils.