生物炭和熟石灰对土壤镉铅生物有效性和微生物活性的影响

Effects of hydrated lime and biochar on the bioavailability of Cd and Pb and microbial activity in a contaminated soil

以南京近郊某蔬菜基地土壤为研究对象,采用盆栽试验方法,研究熟石灰和生物炭两种钝化剂对镉铅复合污染土壤修复效果以及对土壤微生物活性的影响.结果表明,施加熟石灰和生物炭能够增加土壤pH和有机碳等养分含量,促进Cd、Pb由酸溶态向还原态和残渣态转化,降低Cd、Pb有效态含量.与对照处理相比,熟石灰和生物炭5.0%用量下,Cd有效态含量(DTPA、TCLP和CaCl2等3种提取态)分别下降37.74%-41.46%和22.22%-31.71%,Pb有效态含量分别下降45.59%-52.82%和35.47%-41.94%.生物炭的施用提高了土壤微生物量碳氮和微生物群落功能多样性,促进微生物对碳源的利用能力,其中生物炭5.0%用量下土壤微生物活性最高.熟石灰和生物炭的添加显著降低小白菜可食部位和根部对Cd、Pb的富集,与对照处理相比,可食部位Cd、Pb含量分别下降7.14%-47.62%和45.93%-74.82%,但所有添加钝化剂处理小白菜可食部位含量均超出国家安全食用标准.

Pot experiments were conducted to investigate the effects of hydrated lime and biochar on the bioavailability of Cd and Pb in the tested soil, soil microbial community function and accumulation of Cd and Pb in pakchoi(Brassica chinensis L.), using Cd-Pb contaminated soil collected from a vegetable base in Nanjing. The results indicated that application of hydrated lime and biochar effectively increased the soil pH and soil organic carbon, promoted the transformation of Cd and Pb from acid soluble state to reducible and residual state, and decreased the contents of available Cd and Pb in the tested soil. Compared to the control treatment, the three types of available Cd contents(DTPA, TCLP and CaCl2) decreased by 37.74%-41.46% and 22.22%-31.71%, respectively, at a application rate of 5.0% for hydrated lime and biochar. The reduction of the available Pb content was 45.59%-52.82% and 35.47%-41.94%, respectively. The application of biochar significantly increased the soil microbial biomass carbon and nitrogen and microbial community functional diversity, and improved the abilities of the microbes to use carbon sources. Among them, soil microbial activity was the highest at 5.0% biochar treatment. The application of hydrated lime and biochar significantly decreased the accumulation of Cd and Pb in the edible parts and roots of pakchoi. Compared to the control treatment, the contents of Cd and Pb in the edible parts of pakchoi decreased by 7.14%-47.62% and 45.93%-74.82%, respectively. However, the contents of Cd and Pb still exceeded the limit of National Food Quality Standard of the People′s Republic of China with both passivating agent treatments.