秸秆生物炭对湖南3种典型水稻土铅形态转化的影响

Effects of Straw Biochar on the Transformation of Plumbum in Three Typical Paddy Soils in Hunan

以湖南外源铅污染的3种典型水稻土,即红黄泥田、河沙泥田和灰泥田,为研究对象,通过添加水稻、棉花、玉米3种秸秆生物炭进行45 d淹水培养试验,研究了水稻土铅的5级形态变化。结果表明:未添加秸秆生物炭前,土壤铅的分配系数均以残渣态为主体(占36%~50%),其次是碳酸盐态(15%~26%),而其他形态铅均低于16%;3种水稻土中,碳酸盐态、铁锰结合态和有机结合态均以灰泥田的最高,而交换态最低。添加秸秆炭后土壤铅形态变化因土壤而异,从降低交换态或可移动态铅(交换态+碳酸盐态)考虑,灰泥田效果不显著,而河沙泥田和红黄泥田效果显著,3种秸秆炭中均以稻秆炭最好,与对照比较,交换态铅降幅河沙泥田(73.8%)>红黄泥田(62.3%),可移动态铅降幅河沙泥田(44.6%)>红黄泥田(15.1%)。3种水稻土交换态铅含量已低于一般土壤铅毒性临界值水平。

Using the Hunan 3 typical paddy soil which were red mud, river sand mud and plaster field , and polluted by exogenous Pb(430~550 mg/kg) as the research object , by adding 3 kinds of straw biochar of rice, cotton and maize, the five stage morphological changes of Pb in paddy soil were studied by 45 days water culture experiment. The results showed that the distribution coefficient of Pb in soil before adding straw biochar was the main component (36%-50%), followed by carbonate state (15%-26%), and other forms of Pb were less than 16%; carbonate state, Fe and Mn bound state and organic bound state were highest in plaster field, while the exchangeable state was minimum. The change of soil Pb form was different with soil after adding straw biochar, considering the effect of the reduction of the carbonate and movable Pb, the red clayey sand and mud were significant but not in plaster, among the 3 kinds of straw charcoal, rice straw charcoal was the best, compared with the control , for exchangeable Pb reduction, river sand mud(73.8%)>red mud(62.3%), for movable Pb reduction, river sand mud(44.6%)>red mud(15.1%). The exchangeable Pb content in 3 kinds of paddy soils was lower than the general soil Pb toxicity threshold level.