菜籽饼生物炭中污染物赋存特征及其用于土壤改良的适宜性评价

生物炭作为土壤改良剂在农业生产活动中具有巨大的应用价值,但其自身携载的污染物可能会对环境产生影响,因而需要引起关注. 以菜籽饼为前体材料,采用厌氧炭化法于200~700 ℃下制备生物炭,研究了生物炭中PAHs(多环芳烃)、重金属及矿质元素的赋存特征,评估了施用生物炭的环境适宜性. 结果表明:生物炭中PAHs总量(以w计)为0.2~3.4 mg/kg,重金属及矿质元素Cu、Zn、Pb、Cd、Cr、Ni、Fe和Mn的全量(以w计)分别为8.9~23.3、149.9~372.1、1.1~1.9、<0.014、6.3~14.8、5.9~14.0、140.6~462.1和86.8~269.2 mg/kg. 所有生物炭的PAHs总量和重金属全量均低于我国、美国及欧洲国家的污泥农用控制标准(以上各国PAHs总量以及Cu、Zn、Pb、Cd、Cr和Ni全量的最低标准值分别为6、250、500、300、5、600和100 mg/kg),少数生物炭中易淋溶态Mn质量浓度超过以上国家的地下水或饮用水标准(各国的最低标准值为50 μg/L). 总之,高温(500~700 ℃)条件下制备的生物炭中PAHs总量及易淋溶态元素质量浓度较低,适宜在土壤中施用. 

Characterization of Contaminants in Rapeseed Cake-Derived Biochars and Evaluation of Their Suitability for Soil Improvement

Agriculture is greatly benefited from biochar that is used as a soil enhancement. However, much attention needs to be paid to the potential adverse impacts on the environment due to biochar-borne contaminants. Biochars were produced from rapeseed cake under anoxic/anaerobic conditions at temperatures between 200 and 700 ℃. The concentrations of polycyclic aromatic hydrocarbons (PAHs), heavy metals and minerals in biochars were determined, and the environmental suitability of biochars for land application was assessed. The results showed that the total PAHs concentration was 0.2-3.4 mg/kg. The total heavy metals and minerals were found at the following concentrations (mg/kg):Cu, 8.9-23.3; Zn, 149.9-372.1; Pb, 1.1-1.9; Cd, <0.014; Cr, 6.3-14.8; Ni, 5.9-14.0; Fe, 140.6-462.1; Mn, 86.8-269.2. The total concentrations of PAHs and heavy metals in all biochars were below the control standards of sludge for agricultural use in China, the USA and Europe (minimum standards of PAHs, Cu, Zn, Pb, Cd, Cr, Ni in these countries are 6,0, 500,0, 5,0, 100 mg/kg, respectively). The mass concentrations of leachable Mn in some biochars exceeded the groundwater or drinking water standards of these countries (minimum standard was 50 μg/L). Overall, biochars generated at high temperatures (500-700 ℃) were suitable for land application due to their low total PAHs contents and mass concentrations of leachable elements.