珠江三角洲潜在生态风险:土壤重金属活化

Potential ecological risk assessment of heavy metal in soils in the Zhujiang River delta: Heavy metal activation in soils

珠江三角洲典型土壤模拟酸雨提取实验表明,土壤酸缓冲能力为菜园土大于水稻土大于赤红壤。酸化过程早期,铝铁胶体吸附共沉淀导致重金属溶出量增长不明显甚至下降;进一步酸化时,多数元素溶出量与加入酸量呈显著正相关。计算表明,在pH=4.5的酸雨作用下,溶液中Hg、Mn、Pb、Fe(以Fe2O3表示)浓度已超出II级地表水标准,Cu、Zn大大高于渔业用水标准。可见,土壤元素活化溶出对水体生态环境有潜在的危害。

Modeling experiments of extraction of acid rain from typical soils in the Zhujiang River delta indicate that the acid buffer capacities of three types of soil decrease in order of orthic anthrosols, stagnic anthrosols and udic ferralisols. At the beginning of acidification, the dissolved proportion of heavy metals from soils increased slowly or even decreased slightly due to adsorption and co-deposition of Al and Fe colloids. As acidification continued, the dissolved proportion of Al and most heavy metals usually had a pronounced positive correlation with the added acid rain volume. Calculations based on this experiment showed that under the impact of acid rain of pH=4.5 Hg, Mn, Pb and Fe (expressed as Fe2O3) concentrations in solutions surpassed grade II of China's surface water quality standards, while the Cu and Zn concentrations in solutions were greatly above the threshold of fishery water. This shows that there is a potential ecological risk from activation and dissolution of metals in soils under acid rain impact in the Zhujiang River delta.