生物质炭中的污染物含量及其田间施用的环境风险预测

Pollutant contents in biochar and their potential environmental risks for field application

生物质炭在碳固定、污染修复和酸性土壤改良中的应用非常广泛,但对生物质炭中所含污染物的研究甚少,其在田间应用中的环境风险并不清楚。该文选择松针和麦秆为原料,采用不同制备方法,研究了不同条件下获得的生物质炭中的重金属和多环芳烃含量,并初步评估了其田间应用的环境风险。研究表明,不同有机废弃物来源制备的生物质炭中均含有一定量的重金属(0.301～128mg/kg)和多环芳烃(1.48～5.48mg/kg);松针制备的生物质炭中的重金属含量普遍高于麦秆制备的生物质炭,而多环芳烃含量则相反,且高温制备有助于降低生物质炭中的多环芳烃含量;在低施用量的田间条件下,生物质炭的施用不易对土壤造成多环芳烃的环境风险,但在高施用量条件下,生物质炭中含有的多环芳烃容易使土壤中多环芳烃含量达到中度或重度污染的程度;生物质炭中的重金属在土壤中的积累量比较有限,环境风险较小。

Biochar is widely used in carbon sequestration, pollution restoration, improvement of acid soils, and so on. However, there are few studies on examining the pollutant contents in biochar from different raw materials and preparation conditions, and the environmental risk of biochar application is unclear. In this study, the biochars with pine needles and wheat straw as raw materials were prepared under different conditions. The contents of heavy metals and polycyclic aromatic hydrocarbons （PAHs） in biochar were determined, and the environmental risk of biochar for field application was assessed. The results showed that different kinds of biochar contained a certain amount of heavy metals （0.301-128 mg/kg） and PAHs （1.48-5.48 mg/kg）. The contents of heavy metals in the biochar from pine needles were higher than those from wheat straw, but opposite for the contents of PAHs. The Cu, Zn and Cd contents in the biochar by high temperature preparation were higher than those by low temperature preparation, and high temperature preparation reduced the PAHs contents in biochar. With high application rate of biochars, the PAHs in biochars tend to make soil PAHs contents reach moderate or severe pollution level. The environmental risk of heavy metals in biochars is little regardless of low or high application rate in field.