不同可溶性有机碳对铜在土壤中迁移的影响

MOBILITY OF Cu IN SOILS IN RELATION TO DISSOLVED ORGANIC CARBON (DOC)

土壤中可溶性有机碳(DOC)的存在被认为是能促进重金属在土壤中迁移的重要因素之一,但不同DOC的作用效果可能不同。本研究以Cu为研究对象,利用饱和土壤恒定流条件下的混合置换实验,试图阐明:不同DOC(胡敏酸(HA)和柠檬酸(CA))在土壤中的迁移过程,及其对Cu在土壤中迁移的促进作用。结果表明CA在砂土和红壤性水稻土中的移动能力高于HA;而HA和CA均有促进Cu在土壤中迁移的趋势,但CA的促进效果更为明显,这可能与CA比HA更能提高环境pH值及HA的分子比较大有关;尽管Cu在供试的两种土壤中的迁移能力均很弱,但其在质地粘重的红壤性水稻土中的迁移潜力似乎大于其在砂土中的迁移潜力。上述结果表明,当土壤中加入DOC含量较高的溶液时,Cu在土壤中迁移能力的增强可能主要与土壤溶液中存在可移动的Cu-有机质络合物有关,为验证这一研究结果,进一步的田间和长期试验十分必要。

The presence of dissolved organic carbon （DOC） is considered as one of the key factors that facilitate movement of heavy metals, and the effect varies with the type of DOC. In this study, a miscible displacement approach, where soil-watersaturation and constant flow velocity were maintained in soil columns, was applied to investigation of mobility of humic acid （HA） and citric acid （CA）, and their effects on Cu mobility in soil columns. Results show that CA was higher than HA in mobility in sandy soil and red paddy soil, and both HA and CA showed facilitating effect on Cu mobility in soils. The effect of CA was more obvious than that of HA, probably because CA may cause higher solution pH than HA and smaller in molecular weight. More interestingly, though the mobility of Cu was extremely low in the two studied soils, it seems that the potential mobility of Cu was higher in the heavy red paddy soil than in the light sandy soil. The results suggest that the enhancement of Cu mobility in the soils after irrigation with water high in DOC content is related mainly to the presence of mobile Cu-organic complexes in the soil solution. Further long-term and field experiments are required to validate the findings.