海三棱藨草(Scirpus mariqueter)根系低分子量有机酸对根际沉积物重金属生物有效性的影响

应用等离子光谱仪(ICP)与高效液相色谱仪(HPLC)分别对海三棱藨草根际沉积物中重金属(Cu、Pb、Zn和Cd)不同化学形态含量和植物根系分泌物中常见低分子量有机酸进行了季节跟踪测定,分析了有机酸(柠檬酸、草酸、酒石酸、苹果酸、甲酸和乳酸)含量与重金属化学形态(可交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态和残渣态)的季节相关性。结果表明,柠檬酸、草酸和苹果酸含量与Cu和Pb的除残渣态外的其它4种形态含量呈正相关性,表明其能提高Cu和Pb生物有效性,与Zn的所有形态含量呈负相关性,降低了生物有效性;酒石酸、甲酸和乳酸含量与Cu和Pb的可交换态含量呈负相关性,而与其它形态含量相关性不明显,降低了生物有效性。与Zn的除残渣态外的其它4种形态含量呈正相关性,提高其生物有效性。而上述所有有机酸与Cd的各种化学形态相关性不明显。表明其对Cd的生物有效性影响不大。

EFFECTS OF LOW MOLECULAR WEIGHT ORGANIC ACIDS OF ROOT EXUDATES ON HEAVY METAL BIOAVAILABILITY AROUND SCIRPUS MARIQUETER RHIZOSPHERE SEDIMENTS

Different fractions contents of heavy metal (Cu, Zn, Pb and Cd) in rhizosphere sediments of Scirpus mariqueter and low molecular weight organic acids (LMWOAs) of plant root exudates were measured by ICP and HPLC respectively in different seasons. The seasonal correlations between contents of different fractions (the exchangeable, the combination of carbonate, the ferro-manganese oxides, the organic-bounded and the residues) of heavy metals and LMWOAs (the citric, oxalic, tartaric, malic, formic and lactic acid) were analyzed. Results indicated the contents of citric, oxalic and malic acid were positive correlations to all the other four fraction contents of Cu and Pb except the residues content, which showed those acids above could improve their bioavailability. However the contents of citric, oxalic and malic acid were negative correlations to the all different fraction content of Zn, which reduced its bioavailability. The contents of the tartaric, formic and lactic acid were negative correlations to the exchangeable contents of Cu and Pb, and they were not obvious correlations to the other fraction contents. So the three acids above could reduce their bioavailability. The contents of the tartaric, formic and lactic acid were positive correlations to all the other four fraction contents of Zn except the residues content, which showed those acids above also could improve its bioavailability. For Cd, all the acids above have no obvious correlations to the four heavy metals, which showed they have few effects on its bioavailability.