三峡库区蓄水初期大宁河鱼类重金属污染特征

Characteristics of heavy metals pollution of fishes in Daning River of Three Gorges Reservoir Area during initial impoundment

三峡水库蓄水后,库区不同水域的水体状态存在差异。为揭示三峡库区中不同水体环境条件对鱼类重金属含量的影响,以大宁河河口(巫山)和回水区(大昌)分别代表库区中的河流型和湖泊型水体,在两地分别采集了11种鱼类,利用稳定同位素分析了两地鱼类食物来源和营养等级,并测定鱼类样本中的Cr、Cd、As、Pb、Ni、Cu和Zn 7种重金属含量。结果显示,大昌鱼类的稳定同位素δ13C值范围(-28.8‰～-22.5‰)宽于巫山鱼类的δ13C值范围(-26.2‰～-23.1‰),但大昌鱼类的δ15N值普遍负于巫山鱼类。两地鱼体重金属含量除As外均处于较低水平。两地的中上层鱼类体内重金属含量无明显区别,但大昌的底层鱼类体内重金属含量显著高于采自巫山的底层鱼类含量,与沉积物的较多接触可能是该地区底层鱼类部分重金属水平显著升高的重要原因。

There exists spatial heterogeneity in the water environment in different areas of the Three Gorges Reservoir Area （TGRA） after impoundment. In order to explore the effects of different water environmental conditions on the heavy metals concentrations in the fishes in TGRA, we selected the river mouth （Wushan） and backwater area （Dachang） of Daning River, a typical tributary in central TGRA, as the study areas. Eleven fish species were collected from each of the two sites, and the Cr, Cd, As, Pb, Ni, Cu and Zn concentrations in the muscle tissue of all fish samples were determined. The food sources and nutrition levels of the fish samples were evaluated by using stable isotope analysis （δ13C and δ15N）. It was found that the fishes in Dachang had greater range of δ13C values （-28.8‰--22.5‰） than those in Wushan （-26.2‰--23.1‰）, while the δ15N values of the fishes in Dachang were lower than those in Wushan. There were no significant differences in the heavy metal concentrations in the fishes in Dachang and Wushan, but the heavy metal concentrations in demersal fishes in Dachang were significantly higher than those in corresponding species in Wushan. As compared with other fishes, the demersal fishes in backwater water area had more contact with sediments, which could be an important reason for the higher heavy metal levels in the demersal fish tissues.