太湖水华蓝藻中元素的组成及其环境意义

苏彦平; 杨健; 陈修报; 刘洪波

太湖水华蓝藻中元素的组成及其环境意义

Study on Element Bioaccumulation in Cyanobacteria in the Taihu Lake and Its Environmental Significance

摘要

摘要: 利用电感耦合等离子质谱仪对2008年7、9和10月采自太湖南泉水域的水华蓝藻样本中19种元素（Na、Mg、K、Ca、Zn、Mn、Fe、Al、Cu、Cr、Co、Ni、As、Se、Mo、Ag、Tl、Cd和Pb）的质量含量（w）及组成变化进行研究。结果表明,在藻华中w较高（>1 000μg.g-1,以干质量计）的常量元素或有益元素为Ca、K、Na、Mg、Al、Fe。其中,w（Ca）和w（K）较高（>4 000μg.g-1）,w（Ca）随月份变化不大,而w（K）、w（Mg）、w（Na）则逐月升高。w（Al）、w（Fe）变化较大,7月最高（>1 000μg.g-1）,之后迅速降低（<400μg.g-1）;藻华中w在10100μg.g-1之间变化的元素为Mn、Zn、Ni、Cu,其中,7月这4种元素w均最高,910月则降低。藻华中还检出痕量元素Co、Mo和Se,Tl未检出。藻华中积累的有毒元素中w（As）较高（515μg.g-1）,而w（Cr）、w（Cd）、w（Pb）、w（Ag）均较低（<5μg.g-1）。有毒元素w最高值均出现在7月。基于上述结果,推算出2007—2009年采取物理方法除藻从太湖中移除的元素量约为:K595.89 t、Ca 544.03 t、Mg 181.18 t、Al 83.06 t、Na 63.97 t、Fe 55.45 t、Mn 2.99t、Zn 2.26 t、Ni 1.67 t、Cu 1.11 t、As 0.76 t、Cr 94.5 kg、Cd 82.70 kg、Se 45.01 kg、Pb 37.64 kg、Co 32.27 kg、Mo5.41 kg和Ag 2.46 kg。该研究不仅可为进一步寻找关键元素在蓝藻水华爆发过程中的限制作用及其机制提供基础数据,同时也可为评价利用物理除藻方法去除太湖中有毒元素和降低有可能促进藻华发展的营养元素的负荷量的有效性,从而保护和修复渔业环境提供理论依据。

Abstract: The Taihu Lake is the third largest fresh water lake in China.Recently,it has seen heavy cyanobacterial blooms in the lake almost every year.Samples of cyanobacteria were collected from Nanquan area of the Taihu Lake in July,September and October 2008 for analysis of contents of 19 elements(Na,Mg,K,Ca,Zn,Mn,Fe,Al,Cu,Cr,Co,Ni,As,Se,Mo,Ag,Tl,Cd and Pb) therein and variation of the composition,using an Agilent 7500ce inductively coupled plasma mass spectroscopy(ICP-MS).All the 19 elements,except for Tl,which was undetectable,evidently accumulated to varying levels in the cyanobacteria.The concentrations of Ca,K,Na,Mg,Al and Fe were commonly>1 000 μg·g-1 dry weight(esp.Ca and K were>4 000 μg·g-1 dry weight).From July to October,Ca remained relatively stable in concentration,while K,Mg and Na gradually increased.The concentrations of Al and Fe were the highest in July,but dropped sharply in September.Mn,Zn,Ni,and Cu,found to be moderate in concentration(10-100 μg·g-1 dry weight),peaked in July and bottomed in September and October.In contrast,Co,Mo,and Se were measured to be low in concentration(<1 μg·g-1 dry weight).And some toxic elements As(5-15 μg·g-1 dry weight),Cr,Cd,Pb and Ag(<5 μg·g-1 dry weight) were detected in cyanobacteria,and usually peaked in concentration in July.Based on the aforementioned results and the provincial government reports on the physical removal of cyanobacteria in the Taihu Lake in 2007-2009,it is estimated that approximately 595.89 t of K,544.03 t of Ca,181.18 t of Mg,83.06 t of Al,63.97 t of Na,55.45 t of Fe,2.99 t of Mn,2.26 t of Zn,1.67 t of Ni,1.11 t of Cu,0.76 t of As,94.5 kg of Cr,82.70 kg of Cd,45.01 kg of Se,37.64 kg of Pb,32.27 kg of Co,5.41 kg of Mo and 2.46 kg of Ag were consequently removed from the Taihu Lake during the same period.The findings of this study may serve as fundamental insights for further investigation of the elemental effect on the occurrence and development of cyanobacterial water blooms,and furthermore,provide important evidence for making use of the bioaccumulation properties of cyanobacteria to reduce toxic element loads and conserve the fishery environment of the Taihu Lake.

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