贵州阿哈水库不同季节水体和沉积物重金属分布特征及污染评价

Distribution characteristics and pollution assessment of heavy metals in water and sediments of Aha Reservoir of Guizhou in different seasons

探讨湖库不同季节水体和沉积物中重金属的分布特征并对其进行污染评价,有助于深入理解湖库环境重金属污染的时空动态演化及其环境效应。对贵州阿哈水库不同季节水体和沉积物中8种重金属的深度分布特征及其污染评价进行了分析。阿哈水库水体重金属含量排序为Ni>As>Zn>Cu>Cr>Co>Pb>Cd。夏秋季节缺氧的底层水体重金属含量增高与表层沉积物铁锰还原导致的重金属释放有关。冬春季节湖水混合期水体重金属的垂向变化较小。沉积物重金属含量排序为Zn>Ni>Cr>Co>Cu>As>Pb>Cd。沉积物活跃层(12 cm以上)重金属含量峰值的季节变化与沉积物-水界面氧化还原状况及与之对应的铁锰还原和硫酸盐异化还原的季节性变化的共同作用有关。阿哈水库夏秋季节沉积物活跃层重金属(主要是Co、Ni、As和Cd)的含量、污染程度和潜在生态风险高于冬春季节同深度的沉积物,但通过孔隙水向上覆水体扩散的影响非常有限。阿哈水库4个季节水体重金属含量均未超过《地表水环境质量标准》(GB 3838—2002)Ⅰ类标准与《生活饮用水卫生标准》(GB 5749—2006)规定的标准限值,表明水体没有重金属污染。

Clarifying the distribution of heavy metals in water and sediment across different seasons and evaluating their pollution are helpful to better understand the spatiotemporal dynamics of heavy metal pollution and its environmental effects in lakes and reservoirs. We analyzed the vertical distribution and the pollution evaluation of eight heavy metals in stratified water and sediments of different seasons in Aha Reservoir. The concentrations of eight heavy metals in the stratified water were in an order as Ni>As>Zn>Cu>Cr>Co>Pb>Cd. The increases in the concentrations of heavy metals in the hypoxic bottom water in summer and autumn were related to the release of heavy metals caused by the reduction of iron and manganese in the surface sediments. In the lake water mixing period of winter and spring,there was limited vertical change of heavy metals in the stratified water. The concentrations of eight heavy metals in the sediments were following an order of Zn>Ni>Cr >Co >Cu >As > Pb > Cd. The seasonal variation of the peak concentrations of heavy metals in the active sediment layer( above 12 cm) was related to the combined effects of the redox status of the sediment-water interface and the corresponding seasonal variation of iron-manganese reduction and sulfate dissimilatory reduction. The concentration,pollution degree,and potential ecological risk of heavy metals( mainly Co,Ni,As and Cd) in the active layer of sediments in the Aha Reservoir were higher in summer and autumn than that in winter and spring.The influence of pore water diffusion into overlying water was very limited. The concentrations of heavy metals in the water in all the four seasons of Aha Reservoir did not exceed the standard limit specified in the "Surface Water Environmental Quality Standard"( GB 3838-2002) Class I standard and"Drinking Water Sanitary Standard"( GB 5749-2006),indicating that the water of Aha Reservoir had no heavy metals pollution.