鲤鱼鱼鳃微环境酸碱条件与铜形态分布模拟

用鱼鳃微环境测定装置和化学平衡计算方法,研究了在人工河水中暴露于铜的鲤鱼鳃部微环境的pH、碱度、粘液含量和铜形态分布.结果发现,鱼鳃pH平衡点为6.92,人工河水pH高于或低于此值时,鱼鳃微环境pH偏低或偏高.变化幅度约达-0.6至0.4 个pH单位.根据实测结果分别建立了计算人工河水和鱼鳃微环境碱度以及鱼鳃粘液分泌量随暴露铜含量和pH变化的定量模型.化学平衡计算结果说明,在pH6至9范围内,人工河水中优势态铜从游离态铜过渡到羟基络合态铜.由于粘液和pH差异的影响,鱼鳃微环境中生物有效态铜含量显著低于人工河水.这样的差别在酸性条件下尤为显著.

SPECIATION OF COPPER IN THE FISH GILL MICRO-ENVIRONMENT

pH, alkdalinity, mucus content and copper speciation in the gill microenvironment of carp ( Cyprinus carpio) were investigated using exposure experiment and chemical equilibrium calculation. It was found that the balance pH of the fish gill was 6.92 at which the pH in the microenvironment was identical to that in the bulk solution. pH in the gill microenvironment shifted to more acid or more basic when the pH of the bulk solution was adjusted to either above or below this point. Models were developed to calculate gill pH based on bulk solution pH and calculate alkalinity based on pH of either bulk solution or the gill microenvironment. The results of the chemical equilibrium modeling indicated that within pH range of 6 to 9, the dominant species of copper in the bulk solution shifted from free ions to hydroxo complex. Because the influence of mucus complexation and pH change, bioavailable copper species in the fish gill microenvironment were significantly lower than those in the bulk solution , especially under acidic condition.