重金属有效态与土壤环境质量标准制订

制订合适的土壤环境质量标准是评价土壤健康质量及食品安全的核心问题,而土壤重金属有效态对制定土壤环境质量标准具有重要意义。土壤重金属有效态主要指植物有效态,它与重金属形态关系密切。影响土壤重金属有效态的因素很多,主要包括:土壤pH值、氧化还原电位、CEC、有机质含量、粒径组成(黏粒含量)、铁铝锰氧化物含量、植物种类、土壤微生物、土壤温度的高低、重金属来源等。化学试剂浸提法是测量重金属生物有效性的常用方法,所用化学试剂主要有三类:弱(稀)酸、络合剂和中性盐,中性盐由于对土壤pH值影响小而受到重视。我国现行土壤质量标准采用土壤重金属总量和pH两个因素为依据,但是不少学者认为,该标准仅适用于重金属有效态较高的土壤,而不能反映重金属有效态含量较低土壤的实际状况。

The Bioavailability of Heavy Metal and Environmental Quality Standard for Soil

The suitable environmental quality standard for soil is vital to appraise soil and food quality,and the bioavailability of soil heavy metal is significant to making the suitable environmental quality standard for soil.The bioavailability of soil heavy metal is mainly referred to the availability of plants which has close relationship with the speciation of heavy metals.Many factors influence the bioavailability of soil heavy metal mainly including:pH of soil,Eh,CEC,organic content,grain making up,iron aluminum manganese oxide content,plant kind,soil microorganism,soil temperature,source of heavy metals etc.Chemical reagent soaking is usually used to measure bioavaitability of soil heavy metal.There are three kinds of chemical reagent used:weak acid,complexant and neutral salt and the neutral salt is paid attention to because it can't influence soil pH value.The current soil quality standard of our country is based on the total amount of heavy metal and pH.Many scholars think that this standard is only suitable for the soil where the bioavailability of soil heavy metal is high.