利用苔藓植物监测分析贵州草海的重金属大气沉降特征

Monitoring and analysis of heavy metal atmospheric deposition of Caohai Lake in Guizhou by bryophytes

关键词:  草海, 湿地, 重金属, 沉降通量, 污染特征, 苔袋(MossBag)

Key words:  Caohai Lake, wetland, heavy metals, deposition flux, pollution characteristics, MossBag

摘要:

贵州草海是典型的高原湿地生态系统,对调节区域气候、维持生态平衡起着重要的作用,研究大气沉降重金属通量及污染特征,对于草海湿地的稳定性与可持续发展具有深远意义。为分析贵州草海的重金属大气沉降特征,该研究利用苔藓植物对重金属的敏感性与耐受性作为生物监测指示植物,运用苔袋法(MossBag)监测贵州草海高原湿地系统湖泊大气沉降重金属污染状况,测定其中Cu、Pb、Zn、Cd、Cr、As、Hg七种重金属,用ICP-MS以及原子荧光检测了这七种元素含量,计算沉降通量,并利用主成分分析及相关性分析解析污染特征与来源,用地积累污染指数法对其数据进行评价分析。结果表明:草海各元素大气沉降通量存在明显的差异,Cu和Zn元素沉降通量远高于其他元素,达到21.43 μg·m^-2·d^-1和102.82 μg·m^-2·d^<sup>-1,占总沉降比重大。相关系分析表明,Cu与Zn、As与Cr、Cd与Pb表现出正相关关系,表明它们有相同来源,其他元素之间的相关性表现不显著。运用地累积指数法判断,七种重金属均属于严重污染,其中Cd尤为严重。根据重金属污染特征及来源分析,草海大气沉降重金属污染主要受到多种因素共同作用,包括产业结构和生产生活方式,甚至是已经关闭的土法炼锌遗留的影响。

Abstract:

As a critical part of wetland system in Guizhou plateau, Caohai Lake plays important roles in maintaining ecological balance, healthy and harmonious species diversity and the regional climate regulation. In order to stabilize the wetland and sustainable development resource, it is critically important to study the characteristics of heavy metals pollution in atmospheric deposition flux and pollution characteristics. By the susceptibility and tolerance of bryophytes to heavy metals, MossBag method was used to monitor the heavy metal pollution around the lake for seven heavy metals(Cu, Pb, Zn, Cd, Cr, As and Hg)analyses, and the contents of seven heavy metals were detected by ICP-MS and atomic fluorescence. The sediment flux was calculated. The principal component analysis and correlation analysis are applied to study their characteristics and origins of such pollutants, while the ecological risks of these seven heavy metals were evaluated using geoaccumulation index method. The results were as follows: The heavy metals in atmospheric deposition fluxes of Caohai Lake were significantly different, among which Cu and Zn deposition fluxes much higher than Pb,Cd,Cr,As and Hg, reaching 21.43 μg·m^-2·d^<sup>-1 and 102.82 μg·m^-2·d^<sup>-1, accounting for a large percentage of total deposition flux. The correlation analysis showed that there was a positive correlation between As and Cr, Zn and Cu, Cd and Pb indicating that they were from similar or same sources. However,there was no significant correlation between other metals. Applying the geoaccumulation index method, the following conclusions were reached: All seven heavy metals were seriously polluted, of which Cd was at the extremely high pollution level. According to the characteristics and sources of heavy metal pollution around Caohai Lake, heavy metal pollutions were considered mainly caused by many factors, including industrial structure and production and life style, and even the leftover of primitive zinc smelting industry in the vicinity.