石灰钝化法原位修复酸性镉污染菜地土壤

In-situ lime immobilization of cadmium in vegetable field of acid soil zone

在湖南省湘潭县酸性(pH=5.47±0.64)镉污染((1.06±0.08)mg·kg^(-1))菜地,进行为期1年的田间修复实验。研究施用石灰类钝化剂(石灰石或生石灰)对菜地土壤镉(Cd)的有效性、当地常见蔬菜可食部位Cd含量的影响,分析蔬菜种植过程中农业投入品对表层土壤(20 cm)Cd积累的影响,确定Cd污染菜地蔬菜安全生产的措施。结果表明:与对照相比,施加4 500 kg·hm^(-2)CaCO_3或3 000 kg·hm^(-2)CaO分别使土壤pH升高了1.48和1.73,土壤有效态Cd含量分别降低了87.8%和78.1%;叶菜类、根茎类、茄果类和豆类蔬菜可食部位Cd含量分别降低了5.9%～70.5%、59.8%～65.8%、4.0%～50.0%和35.0%～76.4%,但施用4 500 kg·hm^(-2)CaCO_3或3 000 kg·hm^(-2)CaO不能使叶菜类、茄果类蔬菜中Cd含量降低到相应的国家食品安全标准限值(叶菜类蔬菜,0.2 mg·kg^(-1);茄果类蔬菜,0.05mg·kg^(-1))以下;蔬菜种植过程中施用的基肥、灌溉水、CaCO_3或CaO不会导致表层土壤Cd含量增加。在酸性Cd污染菜地施用CaCO_3或CaO、并种植低Cd积累蔬菜,可以实现蔬菜的安全生产。

A field experiment was conducted in a vegetable land with an elevated cadmium （Cd） concentration in the soil of Xiangtan county, Hunan province. The effects of application of CaCO3 or CaO on Cd availability in vegetable soil, the Cd concentrations in edible parts of different local vegetables, and the effect of continuous application of agricultural input on Cd accumulation in the upper 20 cm layer of soil in vegetable land were investigated. An appropriate technology for safe production of vegetable in Cd-polluted farmland was proposed. The application of 4 500 kg·hm^-2 CaCO3 or 3 000 kg·hm^-2 CaO increased soil pH by 1.48 and 1.73, but decreased the CaCl2-extractable Cd by 87.8% and 78.1%, respectively, as compared to the control. The application of CaCO3 or CaO significantly decreased Cd concentration in edible part of the leafy vegetables, rootstalk, solanaceous fruit and legume vegetables with a reduction range from 5.9% to 70.5%, 59.8% to 65.8%, 4.0% to 50.0% and 35.0% to 76.4%, respectively. However, Cd concentrations of both leafy vegetables and solanaceous fruit vegetables still exceeded the Chinese maximum permissible limits for Cd （0.2 mg·kg^-1 for leafy vegetables and 0.05 mg·kg^-1 for solanaceous fruit vegetables） even though the application of 4 500 kg·hm^-2 CaCO3 or 3 000 kg·hm^-2 CaO in the experiment. The use of agricultural inputs including fertilizer, irrigation water and lime （CaCO3 or CaO） has no obvious effects on the accumulation of Cd in the topsoils. The present results suggest that planting low Cd-accumulating varieties in combination with application of CaCO3 or CaO could produce safe vegetables in moderate Cd contaminated field.