重金属污染农田安全利用:目标、可选技术与可推广技术

当前,土壤重金属污染研究的主要任务之一是形成安全利用可推广技术方案。那么,当前科学界是否有能力提供这样一个方案?本文在分析土壤污染防控基本概念和决策树的基础上,系统解析了如下问题:污染农田安全利用的目标、技术选项、可推广技术标准和形态。我们认为污染农田安全利用有狭义和广义之分,以主粮区籽粒安全生产为目标的狭义安全利用技术研发是当务之急;安全利用技术的标准是农作物可食用部位的重金属含量达标,而不是土壤重金属钝化效果;重金属从根部到地上部的转运能力是作物筛选和改造的关注重点;低镉作物品种选育与推广有可能零成本地实现轻微镉污染农田安全利用,而钝化剂/土壤调理剂在优选以后将逐渐提高适合安全利用的农田镉污染上限;成本、效果和土壤生态效应是可推广安全利用技术的重要评价标准,可推广安全利用技术的形态受限于农业生产过程,需要以种子、肥料和农艺等形式交付使用者。这些系统分析,有利于安全利用技术研究从"百花齐放"向可推广技术转变,并最终服务于《土壤污染防治行动计划》污染农田安全利用目标。

Safe utilization of heavy metal-contaminated farmland: Goals, technical options, and extendable technology

A major task for current soil environmental study is to form problem-solving schemes for the safe utilization of contaminated farmland. Is the scientific community able to provide such schemes as quickly as possible to meet the need by the national "Action Plan for Soil Pollution Prevention and Control"? Here we analyzed the fundamental concepts and decision tree for soil pollution control, based on which the goals, technical options and extendable technology for the safe utilization of contaminated farmland were explored. It is proposed that safe utilization of the contaminated farmland could be referred both in the broad sense and in the narrow sense, with the narrow safe utilization being the priority. The safe utilization of contaminated farmland aims to the production of foods meeting the national food standards, but not the immobilization or cleanup of soil contaminants. Selection and cultivation of low-Cd crops is a promising technology, while the coupled use of metal immobilizers may increase the upper threshold of farmland metal contamination suitable for the safe utilization. We suggest that cost, effect and secondary eco-toxicity are important criteria for evaluating the safe utilization technology, and the form of the extendable technology may consider the traditional agronomic elements like seeds, fertilizers and tillage regime. This work is supposed to promote the translation of soil pollution control knowledge to the safe farming technology, which may ultimately serve the goals of the "Action Plant for Soil Pollution Prevention and Control".