Environmental impacts from mining at Taojiang Mn ore deposit, central Hunan, China

Tyndrum was an industrial mining area from 1741 until the 1920s where the main ores extracted were lead sulphide (galena) and zinc sulphide (sphalarite). Situated in central Scotland, the now deserted site is identified as a highly polluted, barren area where the original waste residues from the mine, an ore processing and a smelting site are clearly evident. Previous studies have suggested that high levels of lead and zinc contaminants are still dispersed from this former mine site, both atmospherically and through fluvial transport. For example, high concentrations of Pb, identified by its isotopic signature as originating in Tyndmm, have been found in sediments in Loch Tay, 25 km east of this area. This paper presents the results of a study of the occurrence and magnitude of airborne contamination by dispersion from the former mine site using measurements of metal concentrations in tree bark. These naturally occurring 'bio monitors', which accumulate airborne materials including heavy metals, have become an effective alternative to the more costly air-filter system, which is restricted in scope and coverage. Bark samples were acquired from Scots pine (Pinus sylvestfis) trees, which are abundant around the derelict mine site. Suitable locations were chosen to investigate atmospheric transport and deposition of contaminants within the area. Bark samples were taken on two sides of each tree, selecting Northwest (NW) and Southeast (SE) facing aspects. Trees of about the same age were selected and samples of bark were carefully removed at an average height of about 2.0 m above the ground. Concentrations of Pb and Zn were determined by atomic absorption spectrometry. The results demonstrate that Scots pine bark is an effective bio-monitor for the dispersal of airborne pollution. Elevated levels of Pb and Zn were observed in the bark facing the waste dump and dissimilar levels were recorded between samples from the northwesterly and southwesterly sides. This indicates that contaminant metals within the area are actively being transported atmospherically, with a major influence by wind direction. Overall, the results have proven to be consistent with and correspond to the implications that waste from this abandoned mining site continues to represent a significant environmental problem, especially in the Tyndrum area.