Hei Liang, Wu Qi-Tang, Long Xin-Xian, Hu Yue-Ming
College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China.
Huan Jing Ke Xue. 2007 Apr;28(4):852-8.
The sewage sludge produced in Guangzhou and other cities contains heavy metals such as Zn which exceeds the national standard for agricultural use and should be taken into consideration. A phyto-treatment system consisted of metal hyperaccumulator Sedum afredii Hance and low-accumulating corn was exploited to phytoextract metals from sludge, in order to reduce heavy metals in sludge and meanwhile to stabilize the sludge and gain innocuous agricultural products. The two plants were co-cropped directly on the sludge plots, the plant biomass and metal uptake were determined as well as the changes of the treated sludge. A pot experiment was conducted to study the interaction mechanisms between the two plant roots. The results of the experiment in plots showed that the efficiency of the phyto-extraction of Zn/Cd by S. alfredii was significantly improved by co-planting and Zn content in S. alfredii reached 9 910 mgx kg(-1), 1.5 folds of that in the mono-crop. Meanwhile the produced corn grain was conformed to the national standards for foods or feeds concerning heavy metals and the treated sludge was biologically stabilized. The results from the pot experiment studying the interaction mechanisms showed that corn roots, separated from S. alfredii with a mesh barrier, decreased pH in the sludge solution, increased DOC and resulted in higher Zn/Cd concentration than that of S. alfredii mono-crop, which caused more Zn/Cd transported to the S. alfredii side and then enhanced the uptake of the heavy metals by the hyperaccumulator.
广州等城市产生的污水污泥含有锌等重金属，其含量超过了农业使用的国家标准，应予以考虑。利用由金属超积累植物东南景天和低积累作物玉米组成的植物修复系统从污泥中提取金属，以减少污泥中的重金属含量，同时使污泥稳定化并获得无害化农产品。将这两种植物直接间作在污泥地块上，测定了植物生物量、金属吸收量以及处理后污泥的变化情况。进行了盆栽试验以研究两种植物根系之间的相互作用机制。田间试验结果表明，间作显著提高了东南景天对锌/镉的植物提取效率，东南景天中的锌含量达到9910 mg·kg⁻¹，是单作时的1.5倍。同时，所产玉米籽粒符合食品或饲料重金属国家标准，处理后的污泥实现了生物稳定化。研究相互作用机制的盆栽试验结果表明，用网屏障将玉米根系与东南景天隔开后，污泥溶液的pH值降低，溶解性有机碳增加，导致锌/镉浓度高于东南景天单作，这使得更多的锌/镉转运到东南景天一侧，进而增强了超积累植物对重金属的吸收。
