土壤镉对林木植物毒性的生物配体模型研究

With the serious situation of a large population with relatively little land in china, it is becoming more and more important to explore and utilize agroforestry resources. While the contamination condition in forest soil is unoptimistic, with commonly accumulation by cadmium (Cd). The biotic ligand model (BLM) has been demonstrated successfully in predicting metal bioavailability and toxicity, while few reports are found in its application for forest soils metal phytotoxicity to trees. The soil samples are selected from the representative forest soil sites and sensitive trees for Cd toxicity are screened by laboratory analysis. The research takes the main line of the dose - response effects between soil Cd concentrations and plant shoots, and its dominating factors. Meanwhile it focuses on the toxicity and quantitative relationship between the chemical speciation of Cd and phytotoxicity by diffusion gradient film and Donnan membrane technology. The aims of the present study are therefore to determine the Cd phytotoxicity to trees in typical Chinese forest soils and its controlling factors, to investigate Cd partitioning in soils solid and solution phases and the influencing factors, and to develop the predictable models for available Cd concentrations. Furthermore, the prediction of single and mixed Zn and Cd phytotoxicity by BLM was evaluated, incorporating the influence of dissolved organic carbon on Cd bioavailability by using trees culture experiments. Finally, we aimed to establish the predictable model - terrestrial biotic ligand model for Cd phytotoxicity in forest soils using the previous research results and base on the concept of competitive binding between toxic metal ions and cations, which illuminating the relationship among soil factors, metal and plants. It would provide the potential theoretical guidance to the quality criteria of soil environment for Cd and risk assessments for Cd contaminated forest soils.

人多地少形势下，我国林地农业开发的重要性日益凸显，但林地土壤重金属污染形势不容乐观，尤其镉污染。生物配体模型（BLM）是预测重金属生物有效性/毒性的理想方法，但应用其评价林地土壤重金属的植物毒性鲜见报道。本项目拟从我国代表性林地野外采样，并筛选对镉毒性敏感的林木进行室内培养实验，以土壤中镉的剂量-效应关系和影响因素为切入点，围绕镉的有效形态对其毒性量化关系，利用扩散梯度膜、道南膜技术：揭示土壤中镉的林木毒害规律及其主控因子，阐明土壤中镉的固-液相分配规律及其影响因素，建立有效态镉的预测模型；探讨镉和锌单一及镉-锌复合胁迫下，BLM对重金属植物毒害效应的预测能力，同时探明溶解性有机质组成对镉生物毒性的影响；基于上述研究结果和竞争配位化学原理，弄清土壤环境因子、重金属、植物三者间的响应关系，建立林地土壤镉植物毒性的预测模型-陆地生物配体模型。为镉污染土壤环境质量标准修订和风险评价提供科学依据。

项目以我国典型的林地为研究对象，分析了林地土壤重金属及氟的污染特征，并研究了土壤理化性质与土壤重金属全量及有效态之间的关系；获取了我国林地土壤溶解性有机质的含量分布及结构特征的信息，解析了DOM的紫外、红外等光谱特征，同时采用三维荧光结合平行因子分析手段分析了DOM来源结构，建立不同活性组分的DOM与土壤镉的相互作用特征；研究了Cd 对12种林木幼苗吸收累积量及生长发育的影响，探讨了品种的敏感性顺序，筛选出了具有代表性敏感性植物品种。.林地大部分位点重金属含量均未超过筛选值和管制值，Cd 的潜在生态危害指数最高，轻微等级生态风险；重金属在土壤中均存在一定程度累积，Cd、Zn、Cr、As污染程度较高，达到中度污染水平。土壤pH值与有效Cu含量有显著正相关性；重金属的全态与有效态存在显著正相关的特征。土壤有效态Pb和Cu可以较好的用土壤性质和全态量表示，相关系数r2分别为0.962和0.895。.研究区域土壤氟的赋存形态以残余态为主，可被植物吸收利用的有效态含量较低。不同形态氟之间存在显著相关性。基于土壤阳离子交换量、黏粒、铝氧化物和锰氧化物的多元经验回归模型可较好预测土壤水溶态氟、可交换态氟和铁锰氧化物态氟的含量，预测模型决定系数r2为0.53-0.70。.DOC与有色溶解性有机质、荧光溶解性有机质、土壤有机质之间存在显著正相关性；宁夏土壤DOM具有较强的疏水性和芳香性，SUVA254与SUVA260呈显著正相关关系；DOM中含有羧酸、醇类、烷烃、苯酚、多糖等基团；研究区林地土壤DOM包含三种光谱成分，2种类腐殖质和1种类蛋白质，自生源指标（BIX）和荧光指数的变化范围分别为0.54~1.14和1.62~2.21。.不同镉处理下，植物株高、叶片和根系的毒害效应随浓度的增加，毒害效应加强，不同的植物对应的症状有差异；低浓度镉对木本植物生长有一定的刺激作用。品种的敏感性顺序随着生理指标的变化而呈现无规律变化，植物地上部干重和株高差对镉胁迫的响应比其他指标更加敏感，性状更稳定。综合所有指标，筛选出了具有代表性的敏感品种，即金森女贞。