重金属(铜、镉、锌和铅)对海水无机碳体系影响的模拟研究

Effects of heavy metal(copper,cadmium,zinc and lead) on marine inorganic carbon system in simulated experiments

通过室内模拟实验,研究了孔石莼和重金属(铜、镉、锌和铅)共同作用下,海水无机碳体系及碳源汇格局的变化。结果表明,t=7d时,无机碳体系各参数的变化幅度(Δ)与重金属种类和浓度有关。与对照相比,低浓度(<1μmol.L-1)的重金属添加组中,DIC、HCO3-和PCO2的下降幅度都很明显(P<0.01**)。当铜、镉浓度大于"转折浓度"后,DIC、HCO3-和Pco2均要大于初始值,其增幅随着重金属浓度的增加而增大。对于锌和铅,二者浓度高达50μmol.L-1时,水体中无机碳各参数与初始值相比仍呈现下降趋势。此外,当重金属浓度和种类不同时,水体中的碳源汇格局亦做不同的变化。当铜和镉浓度小于转折浓度时,水体表现为大气CO2的汇;而当铜和镉超出转折浓度时,水体会由大气CO2的汇过渡到源,并且当水体成为CO2的源后,其CO2的释放量是随着铜、镉浓度的增加而增大。在本实验设计的各浓度锌、铅添加组水体始终表现为碳汇,但当锌、铅浓度分别高于15μmol.L-1和20μmol.L-1时,其碳汇强度开始小于对照组(P<0.05*)。

Simulated experiments were performed in laboratory. In these experiments, effects of heavy metal （copper, cadmium, zinc and lead） coupled with Ulca pertusa on marine inorganic carbon system and CO2 fluxes were investigated. The results indicated that concentration changes （Δ） of inorganic carbon system were correlated with the concentrations and kinds of heavy metal （t=7d）. In the heavy metal groups of low concentration （〈1μmol·L^-1）, DIC、HCO3^- and PCO2 significantly decreased comparing to the control experiment data （P〈0.01^＊＊）. When the infusions of copper and cadmium were higher than the ＂critical concentration＂, the above mentioned parameters increased comparing to the control experiment data and their increments followed the uptrend with increasing heavy metal concentrations. As for zinc and lead, when they were 50μmol·L^-1, decreasing trend of inorganic carbon in sea water was still found. Moreover, the results indicated that CO2 sink/source pattern might be controlled by the concentrations and kinds of heavy metal. When the infusions of copper and cadmium were lower than that critical concentration, the corresponding sea waters were presented as sinks to atmospheric CO2. These sinks would probably convert into CO2 sources after the dose of copper and cadmium exceeding the critical concentration and their release fluxes of CO2 augmented along with the increasing infusions of heavy metal. For the groups of zinc and lead, in the range of our experiment dose, the sea waters were always present as atmospheric CO2 sinks. However, when the concentrations of zinc and lead were higher than 15μmol·L^-1 and 20μmol·L^-1, respectively, their carbon sink strength became less than that of the control experiment （P〈0.05^＊）.