苔藓植物对贵州丹寨汞矿区汞污染的生态监测

Ecological monitoring of bryophytes for mercury pollution in Danzhai Mercury Mine Area,Guizhou Province,China

采用野外生态学系统取样方法和室内理化分析方法相结合,分别从苔藓植物地球化学特征、物种丰富度、群落类型、群落的结构等生物学特征上,探讨苔藓植物对丹寨汞矿区汞污染的生态监测。丹寨汞矿区苔藓植物共20个科,34属85种;真藓科和丛藓科占优势。在汞污染程度不同的4种生境梯度中,汞含量均超出国家土壤环境质量三级土标准的10倍以上。各研究生境梯度真藓(Bryum argenteum),丛生真藓(Bryum caespiticium)和狭叶小羽藓(Haplocladium angustifolium)体内的汞含量与其生境基质(土壤)的汞含量在P<0.01水平上呈显著的正相关;且信度系数R均大于0.9,表明被测苔藓植物在地球化学特征上具有监测环境汞污染的生态功能。物种丰富度特征方面,汞污染严重区域物种丰富度较低;而污染程度相对较轻区域物种丰富度则较大;表明了该区苔藓植物丰富度总体上可以作为环境中汞污染的监测指标之一。群落学特征方面,群落类型丰富度在汞污染较重的区域丰富度较低;而苔藓植物群落结构方面,在汞污染较重区域过渡到汞污染相对较轻区域,纯群落数在逐渐减少,但3种及3种以上组成的群落数却有所增加。表现了苔藓群落结构组成越简单则该区汞污染较严重,苔藓植物结构组成越复杂则该区的汞污染程度相对较轻。这说明了苔藓植物群落特征也较适合作为汞矿区生态监测的指标。在汞污染区过渡到相对清洁区的污染过渡带,苔藓物种多样性和群落类型趋于多样化,产生了较明显群落边缘效应。

Mercury（Hg） is a global pollutant and poses a worldwide concern due to its high ecological risk.Ecological monitoring of mercury pollution in Danzhai Mercury Mine Area was studied using bryophytes by means of a systematic sampling design in the field and a physicochemical analysis in the laboratory.Geochemical characteristics,species abundance,community types and community components of bryophytes in this mining area were investigated.Four kinds of habitats with different mercury pollution levels were sampled in the field.Slage area and Mullock area are both serious mercury pollution areas in the Danzhai Mercury Mine Area,and Gaopai area was 4 km and Jingzhong area was 8 km away from mercury pollution area respectively.A 10 m×2 m plot was subdivided into 15 subplots 10 cm×10 cm in size.In each subplot the position of a first sample unit was determined randomly.From the first sample unit of each subplot a second sample unit was taken at a random angle.This sampling strategy resulted in a total of 180 sample units and aimed at a regular coverage of the sampling area. The results showed that a total of 85 bryophyte species belong to 20 families and 34 genera were found,and Bryaceae and Pottiaceae were the dominant families.The mercury content in all habitats were about ten times higher than the Grade Ⅲ（pH6.5,Hg≤1.5 mg/kg） of National Soil Environmental Quality Standard of China（GB15618-1995）.It suggests that the Danzhai Mercury Mine Area had been seriously polluted by mercury.With Regression Analysis,a significant positive correlation（P0.01） was found between mercury contents in the bryophytes Bryum argenteum,Bryum caespiticium,Haplocladium angustifolium and in their substrates,and the reliability coefficients（R） were all greater than 0.9.It explains that if the habitats mercury polluted seriously,the mercury content in bryophytes which grew in the habitats would be increased remarkably.Therefore,the geochemical characteristics of the three species could be used as an indicator of mercury pollution in Danzhai Mercury Mine Area.The best species suited for monitoring mercury pollution was Bryum caespiticium,followed by Haplocladium angustifolium,and for Bryum argenteum in this study area.The index of species abundance of bryophytes were-0.73,-0.54,1.32 and-0.05 respectively in Slage area,Mullock area,Gaopai area and Jinzhong area,and the bryophytes abundance were lower in the seriously polluted areas while higher in the lightly polluted areas.It demonstrates that the bryophyte abundance was suitable for monitoring mercury pollution in this mine area.In the component of community aspect,the number of single-species communities was reduced gradually while the multi-species communities composed of three or more bryophyte species increased observably,and the number of communities composed with two species was not remarkable from the seriously polluted areas to the lightly polluted areas.This phenomenon shows that the community structure component was simple in the seriously mercury pollution areas,but the structural component was more complex in the slightly pollution areas.Therefore,the characteristics of bryophyte community might be one of the indexes of ecological monitoring in Danzhai Mercury Mine Area.Moreover,species abundance and community types of bryophytes increased in transition zone between polluted and less polluted regions（Gaopai area）.This may be an obvious edge affect.Therefore,when ecological monitoring in mining areas according to species abundance and community type abundance of bryophytes are considered one should consider the community edge effect.