Biogeochemistry of a subterranean acidic mine water body at an abandoned copper mine

摘要

Since the 1950's, a large body of acidic (pH approx 2.5) metal-rich water has accumulated and been retained within the underground workings of the former Parys copper mine, Amlwch, north Wales. Concern that the failure of the concrete plug retaining this water body would result in a catastrophic release of acid water that could cause major flooding and pollution problems in the nearby town of Amlwch, resulted in the commissioning of a dewatering scheme at the abandoned mine. Over a ten week period (April to June, 2003) about 274,000 m~3 of water was pumped out of the old mine workings. The composition of the discharge water was monitored throughout this period, as were changes in chemistry of the water as it flowed down the relatively short distance (about 3 km) to the sea. The subterranean water body contained ca. 500 mg/l of iron (almost exclusively ferrous at source), 50 mg/l of zinc and 30 mg/l of copper and 10 mg/l of manganese. There was virtually no removal of zinc or copper as the water flowed to the sea, so that large quantities of these metals were discharged into the bay at Amlwch. Significant numbers (>10~4/ml) of acidophilic ironoxidisers were present in the subterranean water. Perturbations in the microbial biodiversity of the water body during the pumping operation were assessed using combined cultivation-based (isolation on plates) and cultivation- free (T-RFLP and clone library) techniques. Dewatering of the mine allowed access to previously submerged lower depths within the Parys workings. Biofilms and "acid streamers" were sampled from these zones, and their microbial compositions were studied using T-RFLP.