Advanced Utilization of Rhizosphere Functions for Phytoremediation of Heavy Metal Contaminated Soils.

为了开发有效的、环境清洁的植物修复技术，开展了以下方面的基础研究：1)可生物降解的螯合物辅助植物修复；2)金属积累植物及其积累机制的调查；3)利用土壤改良剂减少As从根际向作物地上部的迁移。主要研究结果如下：1.在铜污染土壤中添加可生物降解的螯合剂(S、S-乙二胺-N，N‘-二琥珀酸，EDDS)，与不添加EDDS的植株相比，显著增加了褐芥菜对铜的吸收。与添加EDTA的情况相比，铜和铜络合物的淋失以及对土壤微生物的影响等环境风险较小。然而，可生物降解的螯合物辅助植物修复应该在隔离条件下进行，因为在植物栽培过程中很难完全减少铜和螯合剂的淋失。2.…周围的土壤和植物调查日本兵库县Ikuno-cho关闭的银矿揭示，阿拉比斯鞭毛是一种新的锌、镉超积累植物。研究还发现，著名的重金属富集性蕨类植物--蹄盖蕨能同时富积As和重金属。拟南星叶片中的锌和镉分别有80%以上和55%以上为可溶形态。这表明苹果酸对叶片中高浓度的锌有解毒作用。在高Cd处理下，植株根系中植物络合素等SH类化合物含量增加，表明这些化合物对Cd有解毒作用。3.接种丛枝菌根显著降低了As污染土壤上向日葵对As的毒害症状和As吸收。另一方面，在水稻土中应用无定形氢氧化铁显著降低了受砷污染水灌溉的水稻植株对砷的吸收。较少

To develop effective and environmentally clean phytoremediation technologies, basic researches were conducted concerning about 1)biodegradable chelate-assisted phytoremediation, 2)survey of metal accumulating plants and the mechanism of their metal accumulation, and 3)utilization of soil amendments for reducing As movement from rhizosphere to crop shoots. The main results were listed below :1.Addition of biodegradable chelating agents (S,S-ethylenediamine-N,N'-disuccinic acid, EDDS) to Cu contaminated soils significantly increased Cu uptake by brown mustard, compared with the plants grown without EDDS. Environmental risks, such as leaching of Cu and Cu-chelate and the impact on the soil microorganisms were smaller than the case of EDTA addition. However, biodegradable chelate-assisted phytoremediation should be carried out under isolated condition because complete reduction of leaching of Cu and chelating agents during plant cultivation was difficult.2.Soil and plant survey around the … More closed silver mine at Ikuno-cho, Hyogo Prefecture, Japan revealed that Arabis flagellosa is a new Zn and Cd hyperaccumulating plant. It was also found that well-known heavy metal accumulating fern, Athyrium yokoscense can accumulate As and heavy metals, simultaneously. More than 80 and 55% of Zn and Cd in the leaves of Arabis flagellosa were soluble forms, respectively. It was suggested that malic acid contributed to detoxify high concentrations of Zn in the leaves. When the plant was treated with high Cd, increase of SH compounds such as phytochelatins in the roots were confirmed, which suggested the detoxification of Cd by these compounds.3.As toxicity symptoms and As uptake of sunflower grown on As contaminated soils were significantly reduced by the application of arbuscular mycorrhizal inoculum, compared with the plants supplied with P fertilizers. On the other hand, application of amorphous Fe hydroxides to paddy soil significantly reduced As uptake by rice plants irrigated with As contaminated water. Less