不同热解温度生物炭改良铅和镉污染土壤的研究

Biochars From Different Pyrolytic Temperature Amending Lead and Cadmium Contaminated Soil

为了探究热解温度对生物炭修复重金属污染土壤的影响,将300℃、500℃和700℃下制备的生物炭加入铅(Pb)和镉(Cd)污染土壤进行培养,检测重金属形态的变化。结果表明,加入生物炭培养60d后,Pb和Cd污染土壤pH值较对照上升0.35—0.86单位值,土壤中重金属的酸可提取态含量下降,残渣态含量上升,对目标重金属生物有效性降低的改良效果700℃>500℃>300℃;在生物炭添加量相同的情况下,复合污染土壤中Pb的残渣态含量比对应单一污染高50.60%—72.79%,而复合污染土壤中Cd的酸可提取态含量较对应单一污染高7.53%—12.99%;热解温度影响生物炭的表面特征和吸附重金属机制,进而影响生物炭改良土壤中目标重金属形态分布。

Biochar from biomass pyrolysis has＇received much attention recently due to its strong affinity for organic pollutants and heavy metals. Previous studies have revealed potential applications of biochar in the contaminated soil remediation. However, the knowledge of pyrolysis temperature effects on biochar as a soil amendment remains lacking. In this paper, three bioehars produced at 300℃, 500℃and 700℃were added into Lead （Pb） and Cadmium （Cd） contained soil, variations of these two metals were analyzed before and after 60 days incubation. The results show that soil pH value is increased by 0.35-0.86 units after biochars addition and incubation. Acid extractable form contents of Pb and Cd are reduced, whereas the residual form contents are increased. The reducing bio-availability of target heavy metals by different biochar amendments is in the following order： 700℃〉500℃〉300℃. With the same amount of biochar addition, Pb residual form contents in the combined polluted soil are increased by 50.60%-72.79% from the single polluted soil, and Cd acid extractable form contents in the combined polluted soil are increased by 7.53%--12.99% from the single polluted soil. Pyrolytic temperature affects characteristics of biochar surface structure and mechanism of heavy metal sorption on biochar, and then affects the states of lead and Cadmium in soils .