贵州百花水库消落带常见植物中汞与砷的富集特征

Enrichment features of mercury and arsenic pollutants in the water-level-fluctuating zone of Guizhou Baihua Reservoir and their impact on the general flora and fauna

消落带易受重金属污染,调查分析消落带常见植物对重金属的富集特征,可为消落带重金属污染治理提供依据。于2013年9月对百花水库麦西河河口消落带不同梯度常见植物及土壤进行采样调查,检测植物和土壤中的汞、砷质量比,分析了不同植物对土壤中汞、砷的富集特征。结果表明,除低梯度植物土壤砷质量比超过国家土壤环境质量二级标准外,高、中梯度植物土壤重金属质量比均在国家土壤环境质量二级标准范围内。消落带植物汞、砷质量比差异较大,根、茎、叶中汞质量比分别为0.17～5.90 mg/kg、0.23～1.39 mg/kg和0.13～2.04 mg/kg,砷质量比分别为0.52～22.24 mg/kg、0.03～6.26mg/kg、0.05～5.35 mg/kg。汞质量比从高到低为根、茎、叶和为根、叶、茎的各有8种植物,为叶、根、茎的有6种植物;砷质量比从高到低为根、叶、茎的有12种植物,为根、茎、叶的有11种植物。消落带植物对汞的富集能力强于砷,植物对汞和砷的富集系数分别为0.528～10.561和0.002～0.444,转运系数分别为0.045～2.260和0.003～1.989。消落带高、中梯度植物对汞的富集特征主要为富集型,低梯度植物为根部囤积型;高梯度植物对砷的富集特征主要为根部囤积型,中、低梯度植物为规避型。高梯度植物苎麻（Boehmeria）、中梯度黄花蒿（Artemisia annua）和藜蒿（Artemisia selengensis）地上部对汞富集能力较强,低梯度植物牛鞭草（Hemarthria altissima）根部对汞和砷的积累量较大,苎麻、黄花蒿和藜蒿可作为消落带理想的去除汞污染植物。

The water-level-fluctuating zone is one of the special eco-systems in the case of the reservoir which is fragile to heavy metal contaminations. In order to understand the discrepancies of accumulation factors of different plants,we have collected samples of the different plants and soil samples from Maixi inlets of Baihua reservoir in September,2013. And,then,we have analyzed concentrations of heavy metal contents in the different parts of the plants and the soil compositions. The results of our analysis have shown that both the concentration of the total mercury and the total arsenic vary greatly in the tissues of the different parts for the same plant. For example,the total mercury concentration rates among the plant roots,stems and leaves have been identified and determinated as 0. 17- 5. 90 mg / kg,0. 23- 1. 39 mg / kg and 0. 13- 2. 04 mg / kg,respectively,whereas those for the arsenic,have been found ranging from 0. 52- 22. 24 mg / kg,0. 03- 6. 26 mg / kg and 0. 05- 5. 35 mg / kg,respectively.The pollution patterns of mercury concentration among the different plant sections can be classified into three in the following descending order,i. e.,roots stems leaves and roots leaves stems,each of which can be discovered in 8 kinds of plants. And,in case for the arsenic,we have observed two patterns,i. e.,roots leaves stems and roots stems leaves. In comparison,the former pattern has been found in 12 plants while the latter has been worked out in 11 plants. What is more,comparing the capability of enrichment for plants,mercury enrichment proves to be much stronger than that of arsenic. That is to say,the enrichment ratios of mercury and arsenic for the plants can be found as 0. 528- 10. 561 mg / kg and 0. 002- 0. 444 mg / kg,respectively,with the transferring parameters being0. 045- 2. 260 mg / kg and 0. 003- 1. 989 mg / kg,respectively.Therefore,the plants at high and middle gradient can be grouped as mercury accumulator while plants at lower gradient could be classified as root compartment ones according to their accumulation features. Thus,the main enrichment features of arsenic in the higher gradient plants turn to be the root accumulators,and,in contrast,the middle and lower gradient plants could be classified as the excluding ones. The ground-surface parts of Boehmeria in high gradient,on the contrary,Artemisia annua and Artemisia selengensis have higher mercury concentration rate in the growing middle parts than the other ones. The root of Hemarthria altissima in the low gradient tends to accumulate more mercury and arsenic content rates in the root. Therefore,it would be possible to make Boehmeria,Artemisia annua and Artemisia selengensis the optimistic plants for mercury phytoremediation in the water-level-fluctuating zone.