模拟酸雨下自然红壤与污染红壤中Cd，Cu，Zn的释放特征

RELEASE CHARACTERISTICS OF Cd,Cu AND Zn FROM THE NATURAL AND CONTAMINATED RED SOILS UNDER SIMULATED ACID RAIN

通过对2个自然红壤和2个污染红壤的模拟酸雨土柱淋溶试验,研究了酸雨作用下红壤中重金属Cd,Cu,Zn的释放特征与影响因素,比较了自然红壤与污染红壤重金属释放特征的差异.结果表明,自然红壤中Cd,Cu,Zn的释放量均随酸雨淋溶量增加而线性增加,累积释放量有Zn>Cu>Cd的规律,并且随酸雨酸度增加而增加,3种重金属释放量之间存在显著的线性关系.在污染红壤中,Cd的释放随着酸雨淋溶量的增加呈现对数型增长,Cu的释放模式仍为直线型增长,而Zn的释放在弱酸性酸雨作用下为直线型增长,在强酸性酸雨作用下则为对数型增长,3种重金属释放量之间存在非线性关系.污染红壤中重金属释放量顺序为Cd>Zn>>Cu,大约26%—76%的外源Cd和11%—68%的外源Zn被酸雨淋溶释放,但99%以上的外源Cu被土壤吸附.同时,3种重金属累积释放量均与淋出液中H+离子累积量呈现显著的对数关系;Cd和Zn与TOC累积释放量之间呈现显著的对数关系,Cu与TOC呈现显著的乘幂关系.在酸雨作用下,自然红壤由于重金属释放量很小,出现重金属污染的可能性较小;但污染红壤中大量Cd和Zn的释放可能导致土壤-水体系统发生重金属污染.

Release characteristics of Cd, Cu and Zn from red soils under acid rain and the related influencing factors were studied and differences in heavy metal release from natural soils and contaminated soils were compared in this paper through a leaching experiment of simulated acid rain for two natural red soils and two contaminated red soils. The results indicated that in the natural red soils, release of Cd, Cu and Zn increased linearly with increasing leaching amounts of simulated acid rain, and the accumulative amounts of released heavy metals increased with increasing acidity of acid rain, showing a sequence of Zn 〉 Cu 〉 Cd. There existed significant linear relationships between Cu or Zn release and Cd release. In the contaminated soils, however, Cd release increased logarithmically with increasing leaching amounts of simulated acid rain, but Cu release increased still in a linear way. Zn release was a linear patter when weak acid rain was applied, but a logarithmic one when strong acid rain was applied. There were non-linear relationships among releases of Cd, Cu and Zn. The release sequence of heavy metals in the contaminated red soils was Cd 〉 Zn 〉 〉 Cu. About 26%-76% of external Cd and 11%-68% of external Zn were released through leaching of acid rain, but more than 99% of external Cu was absorbed by the soils. Meanwhile, accumulative release amounts of these three elements were all significantly logarithmically related to H^＋ accumulative amounts in the leachates, but only those of Cd and Zn were also logarithmically related to TOC （total organic carbon） accumulative amounts. The relationships between Cu release and TOC release were a power pattern. For the natural red soils, possibility of acid rain stimulating heavy metal contamination was little due to a small release amount of heavy metals; for the contaminated red soils, however, a great amount of heavy metals especially Cd and Zn were released under acid rain, and contamination with heavy metals in soil-plant systems was greatly possible.