基于梯度薄膜扩散技术的广西环江流域桑田土壤中铅的生物有效性研究

梯度薄膜扩散技术(Diffusive gradients in thin-films,DGT)是一种原位连续环境采样和测量方法,自20世纪90年代中期被报道以来,一直以固态结合相采集和测量水体、沉积物和土壤中有效态重金属,目前液态结合相的DGT多应用于水体中金属离子的检测。分别采用固态结合相(chelex100)和改进的液态结合相(sodium polyacrylate,PAAS)的DGT装置,对广西桑田土壤中有效态Pb进行了累积和测定。简单分析结果表明,两种装置提取的土壤有效态Pb含量与桑树老叶和嫩叶中的Pb含量都呈极显著相关关系,改进的PAAS-DGT装置对土壤中有效态Pb的提取能力更强。融合土壤pH、阳离子交换量(CEC)、有机质(OM)和土壤颗粒组成等理化指标影响,运用多元统计分析,建立了逐步回归模型。多元统计分析表明,两种结合相的DGT技术所构建的回归模型是可靠的,其调整判定系数R2adj分别为0.87、0.89、0.96和0.95,且预测结果融合了影响土壤有效态Pb含量的pH、CEC、有机质和土壤质地等主要因素。研究结果表明两种结合相的DGT装置均能较好预测桑田土壤中Pb的生物有效性,拓展了DGT技术的应用范围。关键词:梯度扩散薄膜技术(DGT);聚丙烯酸钠(PAAS);铅(Pb);生物有效性;桑田;广西

Assessment of Lead Bioavailability by Diffusive Gradients in Thin Films (DGT) in Mulberry Fields of Guangxi Huanjiang River Basin, China

Diffusive gradients in thin-films(DGT)is one of the most promising in situ sampling techniques for trace metal in-situ accumulation since its invention in the mid-1990s.DGT with solid form binding phases has been widely used as an in-situ sampler for trace metals in waters,sediments and soils.However,the developed liquid binding phase has been only used in the analysis of trace metals in the waters.In this study,the bioavaliability of lead in the rhizosphere soils of mulberry were accumulated and measured by different binding phases DGT devices(chelex100-DGT and PAAS-DGT).Simple linear regression analysis between concentrations of Pb in leaves and DGT measured Pb showed good fit,and Pb concentrations accumulated by PAAS-DGT were higher than chelex100-DGT.Multivariate analysis showed that the regression models established by the two binding phase DGT were reliable,and the adjusted coefficients were 0.87,0.89,0.96 and 0.95,respectively.Predicted results from these models incorporated the main factors affecting available Pb in soils,such as pH,cation exchanged capacity(CEC),soil organic matte(rOM)and texture.Results showed that both DGT devices could predict the potential runoff of Pb from soil and the accumulation of Pb in leaves of mulberry,which expanded the applicable range of DGT technique.