有机酸对土壤中镉的解吸及影响因素

EFFECT OF ORGANIC ACIDS ON CADIUM DESORPTION FROM SOILS

研究了酒石酸和柠檬酸对两种不同处理土壤 (镉质土和污染土 )中Cd的解吸行为 ,探讨了介质pH值、支持电解质等对其解吸镉质土和污染土中Cd的影响。结果表明 ,随有机酸浓度升高 ,柠檬酸和酒石酸对镉质土和污染土中Cd的解吸率呈先降低后升高变化 ,出现一波谷 ,波谷位置与有机酸和土壤类型有关。当解吸液起始pH值由 2升至 8时 ,柠檬酸对镉质土和污染土中Cd的解吸率呈降低—升高—降低的变化 ,先后出现一波谷和一波峰 ,且柠檬酸浓度高时变化趋势尤为明显 ;而酒石酸对镉质土和污染土中Cd的解吸率则一直降低。解吸液中支持电解质浓度提高 ,酒石酸对镉质土和污染土中Cd的解吸率增大 ,且以KCl为支持电解质时的解吸率要高于KNO3。

Effects of organic acids on Cd desorption from Cd-saturated soils and contaminated soils were studied. Results show: The desorption rate of Cd for three Cd-saturated soils and three contaminated soils could be characterized by valley-like curves with increase in tartrate or citrate concentration. Desorption rate of Cd was higher under the effect of citrate than under the effect of tartrate when concentration of the organic acids was higher than 2 mmol L -1. Effects of tartrate and citrate on Cd desorption varied with the initial soil pH value. With increase in initial pH value from 2 to 8, Cd desorption rate for Cd-saturated soils and contaminated soils under citrate declined first, then rose, then declined again, forming a curve appearing like a lying 'S'. During the course a valley and a peak appeared clearly when the concentration of citrate was at 6 mmol L -1. Under the effect of tartrate Cd desorption rate decreased with increase in initial pH value from 2 to 8. With higher electrolyte concentration, the desorption rate of Cd increased, moreover, Cd desorption rate with KCl electrolyte was higher than that with KNO 3 electrolyte under the same electrolyte concentration. What is more, effects of organic acids on Cd desorption remained more or less the same regardless of forms and concentrations of Cd in Cd-saturated soils and contaminated soils, initial pH value and type of electrolytes. From the results of this study, it could be concluded that availability of heavy metals was inhibited when concentration of organic acids was low. Contrarily enhanced availability would be found when higher concentrations of organic acids existed. So it is feasible to control the efficiency of bioremediation and phytoremediation for heavy metal contaminated soils by using different types of organic acids under varied conditions.