National Assessment of Sediment-Related Diffuse Mining Pollution in England and Wales

摘要

In catchments affected by diffuse mining-related pollution, the effectiveness of future remediation efforts at point discharges (e.g. mine drainage adits) may be severely limited as diffuse sources persist in elevating instream contaminant concentrations. This paper aims to systematically map potential diffuse mining pollution sources across catchments in England and Wales through (1) undertaking a risk-based classification of all waste rock mining features mapped between 1840 and the present (e.g. waste rock, tailings and processing plants), and (2) screening national datasets of fluvial metal(loid) concentrations in mine-affected catchments. A total of 2402 waste rock features (total surface area: 91 km~2) are identified in mining catchments, which in 11 priority catchments accounts to >10% of the catchment area. Many of these waste rock features are located in steep, upland catchments where risk for ongoing contaminated sediment delivery to watercourses is highlighted by topographic analyses (e.g. distance from stream features, slope and drainage areas) for each feature. There also appears to be a considerable inventory of within-stream potential diffuse pollution sources. In 69% of mine-affected catchments with available fluvial sediment concentration data, lead (Pb) exceeds the Probable Effects Level (PEL), above which potential negative effects on sediment dwelling organisms would be anticipated. The data highlight the ubiquity of diffuse-mining related pollution, and data presented for one catchment in north east England illustrate the importance of diffuse source mining pollution to overall metal export from such river systems. Such information will be of use for managers in catchment scale source apportionment studies and remedial planning for point discharges.