施用玉米秸秆生物炭对镉生物有效性及其胁迫下生菜生长的影响

Effects of biochar derived from corn-straw on cadmium bioavailability,and lettuce growth under cadmium stress

为明确施用玉米秸秆生物炭对重金属镉(Cd)生物有效性及其产生的植株生长胁迫效应的影响,本研究向模拟土壤溶液中加入0%和2%(m/V)的玉米秸秆生物炭,在不同pH值(4.3和7.0)条件下,通过等温吸附实验分析了Cd^(2+)在生物炭上的吸附行为,并结合生菜(Lactucasativa var.longifolia)幼苗植株的生长、根毒性及其Cd积累量的研究,探讨了生物质炭影响下Cd生物有效性与其环境行为之间的关系。结果表明,生物炭表面负电荷量随溶液pH值的增大而增加,玉米秸秆生物炭能够通过静电效应吸附Cd^(2+);Langmuir方程能够较好地拟合Cd^(2+)在玉米秸秆生物炭上的吸附行为,且方程表征的Cd^(2+)最大吸附量参数Q_(m)随pH值的增大而增加。生菜幼苗的根长和干质量均随生物炭的施加而增大,而根中Cd积累量则随生物炭的施加而降低;与模拟土壤溶液中Cd总量(Cdtotal)和根中Cd积累量相比,溶液中Cd^(2+)浓度指标能够更好地预测幼苗根伸长抑制率RRE(r^(2)=0.80,P<0.001)和根中Cd积累量(r^(2)=0.88,P<0.001)。上述研究结果表明,施加玉米秸秆生物炭能够有效降低重金属污染物的生物有效性及其生态环境风险。

In order to clarify the effects of corn-straw biochar application on cadmium(Cd)bioavailability and plant growth under Cd stress,0%and 2%(m/V)corn-straw biochar were added to the simulated soil solutions in this study.At different pH values(4.3 and 7.0),the adsorption behavior of Cd^(2+)on biochar was analyzed using isothermal adsorption experiments.The correlations between Cd bioavailability and its environmental behavior(as affected by biochar)were analyzed together with the data of growth,rhizotoxicity,and root Cd accumulation of lettuce seedlings(Lactuca sativa var.longifolia).The negative charge of biochar increased with the increase in solution pH,and Cd^(2+)was adsorbed by corn-straw biochar through an electrostatic effect;the Langmuir equation fitted the adsorption behavior of Cd^(2+)by biochar optimally,and the maximum adsorption capacity(Q_(m))of Cd^(2+)predicted by the Langmuir equation increased with the increase of pH values.Root length,and dry weight of lettuce seedlings increased with the increasing rate of biochar application,while the content of Cd in the roots decreased with the application of biochar.When compared to the content of total Cd in simulated soil solutions(Cdtotal),and Cd content in roots,the concentration of Cd^(2+)in solutions was more strongly correlated to relative root elongation RRE(r^(2)=0.80,P<0.001),and dry weight(r^(2)=0.88,P<0.001).The application of corn-straw biochar could therefore effectively be used to reduce the bioavailability and ecological risks of heavy metals.