大宝山矿水外排的环境影响:Ⅰ.下游水生生态系统

Environmental impacts of acid mine drainage from the Dabaoshan Mine: Ⅰ. Downstream aquatic ecosystem

通过水质生物检测、理化分析及野外水生大型无脊椎动物多样性实地调查等综合方法,就广东大宝山矿区南侧拦泥库溢出的酸性矿水对下游横石水河生态系统的影响进行了系统研究.结果表明,大宝山矿区拦泥库溢出的酸性矿水对隆线溞具有较强的急性生物毒性,酸性矿水24 h,48 h及96 h对水溞的半致死体积分数LC50分别为13.55%、10.30%、6.20%;安全体积分数为0.06%.通过在暴雨期间对拦泥库上游洪水的各项指标的分析结果表明,拦泥库溢出的酸性矿水pH值可低至2.15,其中铁及重金属的质量浓度分别为:铁216.79 mg/L、锌73.23 mg/L、铜32.63 mg/L、铅1.82 mg/L、镉0.87 mg/L.在尾矿坝下游3.5 km处,重金属质量浓度分别为:铁51.63 mg/L、锌2.83 mg/L、铜1.64 mg/L、铅2.67 mg/L、镉0.1 mg/L和锰20.50 mg/L.从矿水排放口到受矿水影响的下游50 km范围内,河水pH的变化幅度为3.36～7.42.大型无脊椎动物多样性的调查显示,从尾矿坝到受矿水影响的下游25 km范围内,未发现任何底栖动物,而在横石水河上游未受矿水影响的对照点中至少有36种底栖动物存在.可见由大宝山矿区排出的酸性矿水对下游溪流的水生生物多样性和河流生态系统造成了严重的破坏.

Field and laboratory work has been done to investigate the impacts of acid mine drainage (AMD) from the Dabaoshan Mine on the downstream aquatic ecosystem. The pH of floodwater upstream of the mud-retaining impoundment could be as low as 2.15 with high concentrations of Pb (1.82 mg/L), Fe (216.79 mg/L), Cu (32.63 mg/L), Zn (73.23 mg/L) and Cd (0.87 mg/L) during heavy rainfall events. The concentrations of Pb, Mn, Fe, Cu, Zn and Cd in the stream water at about 3.5 km downstream of the mud-retaining dam were 2.67 mg/L, 20.50mg/L, 51.63 mg/L, 1.64 mg/L, 2.83 mg/L and 0.1 mg/L, respectively. pH of the stream water increased from 3.36 at the discharge point of mine water to 7.42 at about 50 km downstream of the mud-retaining dam. Survey at 6 sites found no macroinvertebrates up to 25 km downstream of the mud-retaining dam. This was in contrast with the reference site upstream of the junction of the AMD-affected tributary and the main channel of the Hengshishui River where at least 36 different benthic macroinvertebrate taxa were found. These indicate that AMD from the Dabaoshan Mine has been causing severe damage of the downstream aquatic ecosystem.