城市污水厂脱水污泥施用对马尼拉草生长及其对重金属迁移转化的影响

EFFECT OF DEWATERED SEWAGE SLUDGE ON THE GROWTH OF MANILA GRASS AND TRANSFER OF HEAVY METALS

以厦门市筼筜污水处理厂的脱水干化污泥作为有机肥种植马尼拉草,通过盆栽试验,探讨污泥直接施用对马尼拉草生长和产量的影响及重金属在马尼拉草-土壤间的迁移转化和积累情况.结果表明,污泥中氮、磷、钾和有机质含量丰富,重金属含量均低于城镇污水处理厂污泥处置园林绿化用泥质的标准(GB/T23486—2009);施用适量污泥可促进马尼拉草的生长,污泥用量为20%时,马尼拉草长势最好,生物量最大;污泥用量超过30%,马尼拉草的生长明显受到抑制;马尼拉草对各重金属元素的生物浓缩系数均小于1.0,各重金属元素在马尼拉草-土壤间的富集能力大小为:Cu>Zn>Cd>Co>As>Ni>V>Mn>Pb>Fe>Cr;种植马尼拉草后根际土中Cd、Cr、As的残渣态向有效态转化,Zn、Cu的可氧化态向弱酸溶态和可还原态转化,Mn的可还原态向弱酸溶态和残渣态双向转化,Ni的有效态向残渣态转化,Co的弱酸溶态和可还原态比例有所减小,残渣态比例增加,Pb、Fe、V等元素的各种形态变化不明显.

Manilagrass was planted with direct application of dewatered and dried municipal sewage sludge collected from Xiamen Yundang Wastewater Treatment Plant under pot experiment.The effect of sludge application on the growth and yield of Manilagrass was determined,and the transfer and accumulation of heavy metals in the Manilagrass-soil system was discussed.The results showed that the sludge was rich in nitrogen,phosphorus,potassium and organic matter,and the contents of heavy metals studied were all lower than the limits of national standard,for the disposal of sludge from municipal wastewater treatment plant-quality of sludge used in gardens or parks（GB/T23486—2009）.Application of sludge increased the growth and yield of Manilagrass,which presented the maximum values when the sludge content was 20%.But the growth of Manilagrass was significantly inhibited when the sludge content was more than 30%.The bio-accumulation factors of eleven studied heavy metals in Manilagrass were all lower than 1.0,and the bio-accumulation capacity of heavy metals in the tested Manilagrass-soil systems is as follows： CuZnCdCoAsNiVMnPbFeCr.After the planting experiment,the chemical speciation of heavy metals in the rhizosphere soils transformed to some extent.Cd,Cr and As transformed from residual into bio-available fraction,Cu and Zn transformed from oxidizable into acid-soluble and reducible fractions,Mn transformed from reducible into acid-soluble and residual fractions,Ni transformed from bio-available into residual fraction significantly,Co transformed from acid-soluble and reducible into residual fraction,while Pb,Fe and V showed no significant transformation in chemical speciation.