贵州省主要马铃薯产区土壤镉临界值的研究

The purpose of this project is to establish the soil critical value of cadmium for potato production in major areas of Guizhou province. First, the chemical behavior of soil cadmium ions in water and soil phases is understood by balancing distribution of cadmium in two medium, and the short-term physiological and ecotoxicological effects of cadmium on potato will be studied in order to calculate ecological toxicity threshold for potato growth. In addition, the long-term bioaccumulation effect of cadmium of potato is going to be explored, and the ecological risk assessment method is used to calculate the critical value of soil cadmium to protect the safe production of potato. Moreover, the soil Cd threshold is established based on the protection of soil microbial activity or crop yield as the indicators. Soil environmental quality assessment will be carried on the field soils. According to the research of different aspects such as soil, plant and microorganism, the soil cadmium critical value for the safe production of potato in the local is to be established, which provided the basis for the food safety of potato and the determination of cadmium environmental quality standard in Guizhou province.

本项目旨在确立贵州马铃薯产区马铃薯的土壤镉安全生产临界值，首先通过研究土壤重金属镉在水土两相的平衡分配对该产区土壤镉离子在水土相的化学行为有所了解；其次，一方面研究镉对马铃薯短期生理生态毒性效应，计算其对马铃薯的生态毒性阈值，另一方面研究镉对马铃薯的长期富集效应，应用生态风险评估方法计算保护当地马铃薯安全生产的土壤镉临界值，同时以保护作物产量、土壤微生物活性为指标确立马铃薯土壤镉临界值，对马铃薯产区土壤镉含量进行环境质量评价。综合土壤、植物、微生物等不同方面研究结果确立保护当地马铃薯安全生产的土壤镉临界值，为我国贵州地区马铃薯食品安全及土壤镉环境质量标准的制定提供基础。

本研究选择贵州省主要分布的土壤类型及常见马铃薯品种，建立基于生态风险概率分布的镉临界阈值模型。另外选定贵州省主要马铃薯产区进行取样，测定了土壤及马铃薯中不同重金属含量，结合GIS软件分析各产区空间变化趋势，并进行土壤、马铃薯重金属污染评价和健康风险评价。主要结论如下：.（1）应用生态效应法推导Cd阈值，结果显示本文中拟合的预测方程计算的土壤Cd阈值均高于现行国家标准。（全量法计算出来的阈值均在现行标准的2-4倍之间，外源法预测值最高比现行标准高4.7倍，最低比现行标准高2.65倍）。.（2）应用物种敏感曲线法推导Cd阈值，当累积概率为5%时，Log-normal、Burr Ⅲ计算的Cd临界阈值在pH=5.5、7、7.5，其值分别为1.02、1.08、1.09 mg/kg、 1.43、1.56、1.62 mg/kg。利用两种函数通过回归方程计算的土壤镉阈值较现行标准相比，呈现较为宽松的趋势。.（3）马铃薯污染评价显示：贵州马铃薯各产区整体均为轻度污染，马铃薯对As、Ni和Cd三种重金属富集程度较强，各产区中马铃薯均存在Cr和Cd污染。马铃薯重金属健康风险评价显示: TTHQ和THQ均为儿童＞成人，TTHQ均为盘县＞威宁＞花溪＞荔波＞纳雍＞赤水。.（4）马铃薯不同产区依据土壤全量Cd计算的阈值为：荔波为0.503 mg/kg，赤水为0.168 mg/kg，盘县为7.581 mg/kg，纳雍为8.167 mg/kg，威宁为2.810 mg/kg，花溪为22.2 mg/kg；pH≤5.5、5.5＜pH≤6.5、6.5＜pH≤7.5、pH＞7.5 时全量Cd的阈值分别为2.126、2.452、0.859、6.789 mg/kg。