中文摘要：

基于保水剂所具有的较强重金属吸附能力,近年来已被作为重金属污染土壤的修复候选材料之一,为弄清保水剂如何影响重金属在土壤中的形态转化,通过向镉污染土壤中添加不同用量保水剂后的黑麦草盆栽试验,探讨保水剂（聚丙烯酸钠）对黑麦草吸镉以及对土壤镉形态转化的影响。结果显示,试验所用保水剂对溶液中重金属镉有较强的吸附能力,在镉浓度为200 mg·L~（-1）的溶液中,保水剂吸附镉可达120 mg·g~（-1）以上,添加保水剂可减少镉在黑麦草地上部的积累量。仅添加保水剂处理,60 d后土壤镉下降20%以上。添加保水剂并栽种黑麦草,可使土壤镉附加下降16%以上,培养过程中减少的土壤镉绝大部分被保水剂所吸附。黑麦草根系分泌物对镉的络合可促使难溶性镉向可溶性镉转化,而保水剂通过对可溶性镉的吸附降低了可溶性镉的浓度,促进镉由＂残渣态→可氧化态→可还原态→酸溶态＂的转化,两者共同促进了土壤镉的降低。添加保水剂一方面促进了土壤中难溶性镉向可溶性镉的化学转化,另一方面又减少了镉在植物体内的积累。因保水剂吸附的镉是否在一定时间后可重新释放出来被植物吸收还不清楚,将保水剂作为钝化剂正式用于修复镉污染土壤之前,还须通过长期的生物学试验加以验证。

英文摘要：

Water-retaining agents（WRAs）have recently been proposed for remediation of heavy metal contaminated soils, but their impacts on morphology of heavy metals are not well understood. To investigate effects of WRAs application on cadmium（Cd）morphological transformation in soil and Cd uptake by plants, a pot experiment was conducted for 60 days with and with no ryegrass at WRAs（active ingredient：polyacrylic acid sodium salt-PAAS）application rates of 0‰,2‰,4‰ and 8‰. The results showed that WRAs reduced Cd accumulation in aboveground part of ryegrass. Compared to control, total soil Cd concentrations decreased by more than 20% and 36% in WRA treatments with no and with plants, respectively. The sorption of soluble Cd in soil solution by PAAS facilitates the dissolution of insoluble Cd species,which is further enhanced by the complexation with the root exudates. Thus, the Cd morphology transforms in the following order：residue state → oxidized state → reduced state → acid soluble state. Overall, PAAS application increased chemical activity of Cd on one hand, and reduced its short-term bioavailability on the other hand. However, a long-term botanical experiment is needed to find out the desorption potential of Cd-loaded PAAS before WRAs can be widely used to remediate Cd contaminated soil.