高砷区植物的生态与化学特征

THE ECOLOGICAL AND CHEMICAL CHARACTERISTICS OF PLANTS IN THE AREAS OF HIGH ARSENIC LEVELS

土壤砷污染是一种十分严重的环境问题 ,但目前尚无经济有效的治理方法。利用各种重金属的耐性与富集植物修复重金属污染土壤是当前的研究热点。通过对两个中国典型的砷矿区 (炼砷区 )土壤与植物的系统调查与采样分析 ,发现若干种植物对砷具有极强的耐性和不同程度的富集能力。砷在不同植物中的含量分别为 :蜈蚣草 (Pterisvittata)羽片 16 0 0mg·kg-1DW ,剑叶凤尾蕨 (Pterisensiformis)地上部 12 30mg·kg-1DW ,酸模 (Rumexacetosa)地上部 4 4 0mg·kg-1DW ,苎麻 (Boehmerianivea)叶 5 36mg·kg-1DW ,蟋蟀草 (Digitariasanguinalis)地上部 5 5 0mg·kg-1DW。不同采样点芒草地上部含砷量为 13～ 76 0mg·kg-1DW ,平均 16 0mg·kg-1DW。这几种植物对于砷污染土壤的植物修复研究与应用具有重要的意义。

Arsenic contamination in soil is a severe environmental problem. Currently, there is economical and effective remediation technique for arsenic. The study of using tolerant and hyper-accumulating plants to remediate heavy metal contaminated soils, termed Phytoremediation, has become an intensive topic field. China has long history of arsenic mining and smelting, especially in the south. The tailings and smelting stove residue contain large concentration of arsenic that produced severe arsenic contamination to local waters, soils and organisms. China has a large plant diversity. Therefore, a survey for screening arsenic tolerant and hyperaccumulating plants, as well as their ecological and chemical characteristics may provide useful insight and contribute to the field of phytoremediation. Two localities with high arsenic levels were chosen for investigation. One is an arsenic mine located in Shimen county, Hunan province(SM); the other is an arsenic smelting area located in Guiyang county, Chenzhou city of Hunan province(CZ). Tailing dam and smelting gases were the main sources of arsenic contamination at SM, while smelting residue piles resulting from intensive indigenous arsenic smelting activity during 1950-1980s distributed vastly around some hill valleys in CZ. The surveys were conducted in June and November 1999. Plants that grew on the tailings, smelting residue piles and soils with heavy arsenic contamination were collected. The growing media around the plants roots were also collected for arsenic analysis. Spots with elevated arsenic levels grew scarce of plant species. The major plants grew on the three sites of different arsenic sources were also different. On the tailing dam of SM, only Pteris vittata and Boehmeria nivea were found. Miscanthus sinensis was the dominant plant on the hill with severe gaseous arsenic pollution at SM, other plants were Cynodon dactylon, Digitapia sanguinalis, Erigeron annuus, Dendranthema indicum, Polygonum hydropiper, Alternanthera sessilis, Kummerowia striata and Commelina communis. Miscanthus sinensis, Avena fatua, Artemisia japonica, Solidago virgauren, Lespedeza cunteata, Dicranopteris dichotoma, Pteris ensiformis, Patrinia villosa were the major plants growing around the remains of indigenous arsenic smelting stoves and the residue piles at CZ. Analytical results showed that some plants demonstrated high arsenic tolerance and accumulation. The average arsenic concentration in the tailings and gaseous polluted soils at SM was 24 153 mg·kg -1 and 511 mg·kg -1, respectively, and that in the smelting residues and contaminated soils around indigenous arsenic smelting stoves were 21 184 and 6 888 mg·kg -1 at CZ. The arsenic concentration in the different parts of the plants are as follows (mg·kg -1, dry matter basis): leaves of P. vittata 1 600 mg·kg -1, shoots of P. ensiformis 1 230 mg·kg -1, shoots of R. acetosa 440 mg·kg -1, leaves of B. nivea 536 mg·kg -1 and shoots of D. sanguinalis 550 mg·kg -1, shoots of M. sinensis 760 mg·kg -1. The arsenic concentration in these plants were notably greater than that in normal plants and thus are valuable candidates for phytoremediation of arsenic contaminated soils.