根际是控制植物养分动态的重要因素,养分动态也影响着根际土壤环境.当土壤被污水污泥改良后,根际土壤中的养分和重金属性质也会发生变化.目前很少有人研究施用污泥的土壤中植物根系对根际重金属有效性和分布的影响.采用根垫一冰冻薄层切片法对施用污泥后土壤中油菜根际的养分和重金属分布情况进行研究,以期探明污泥改良土壤中根际重金属的活化特征.当土壤施用污泥后,根际土壤中DTPA提取态Zn,Cd,Ni,Mn,有效磷,有效钾和铵态氮被显著消耗,而根际土壤中DTPA提取态Cu没有明显的消耗或积累.当土壤中施用大量污泥时,根际土壤的pH值随着离根表面距离的增加而增加.无论土壤是否用污泥处理,油菜根际土壤中可交换态Cu都显著减少.当土壤被50％污泥改良时,在距离根表面0-2 mm处的油菜根际土壤中碳酸盐结合态,铁锰氧化物结合态,有机物结合态,残渣态的Cu和Zn都被消耗较多.污泥的施用对油菜的生长有促进作用.随着污泥施用量的增加,油菜地上部分Cu和Zn的含量没有显著变化.施用污泥量小于25％的土壤中,污泥没有增加重金属的可利用性和移动性.除了Cu,油菜根际土壤中DTPA提取态Zn,Cd,Ni的减少表明施用污泥的土壤中重金属的活化是非常有限的.%The rhizosphere contains important factors controlling nutrient dynamics in this zone and the mineral nutrition of plants.Nutrient dynamics also influence the environment of the rhizosphere.The nutrients and heavy metals in the rhizosphere change when soil is amended with sewage sludge.However,little attention has been given to the extent to which plant roots affect the availability and distribution of heavy metals near roots in soils amended with sludge.The objectives of the present study were to investigate the distribution of heavy metals and nutrients in the rhizosphere of Brassica campestris grown in sludge-amended soil,and to predict the availability of metals in sludge-amended soil.The distribution of nutrients and heavy metals in the rhizosphere in sludge-amended soil was investigated using the root mat and a frozen thin slicing technique to provide indications regarding the activation of heavy metals.DTPA-extractable Zn,Cd,Ni,and Mn,available P and K,and ammonium nitrogen in the rhizosphere were markedly depleted when soil was amended with sludge.There was no conspicuous depletion or accumulation of DTPA-extractable Cu in the rhizosphere when the soil was amended with sludge.The pH value in the rhizosphere increased with distance from the roots when soil was amended with larger amounts of sludge.The exchangeable fraction of Cu in the rhizosphere was depleted whether or not the soil was treated with sludge.Carbonate,oxide,organic,and residual fractions of Cu and Zn were depleted in the rhizosphere at a distance of 0-2 mm from the roots when soil was amended with 50％ sludge.Application of sewage sludge had a positive effect on Brassica campestris growth.With an increase in sludge amounts,the concentrations of Cu and Zn in aboveground parts of Brassica campestris did not change.Soil amendments with less than 25％ sludge did not increase the availability or mobility of heavy metals.The depletion in rhizospheric DTPA-extractable Zn,Cd,and Ni indicated that with the sole exception of Cu,release of metals from sludge-amended soil was very limited.
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