Leachability of Trace Elements from Coal Stockpiles

The aim of this project was to study the leachability of environmentally sensitive trace elements from stockpiles of Australian thermal coals and to address the concerns that have been expressed by some overseas purchasers (in particular Japanese power stations). Although there is no evidence to suggest that trace elements are leached in significant concentrations from the exported Australian coals, it was thought prudent to obtain data on the leachate water present at the bases of coal stockpiles and from sedimentation pits at coal loaders and power stations.

The results of the analyses of waters collected from the sumps or ponds at coal loaders, power stations and coal mines have been compared with the values set by the Japanese Ministry of The Environment Environmental Quality Standards (EQS) as target levels for water quality to be achieved in public waters. The data were compared with the Australian and New Zealand Guidelines for water quality.

Findings

The analyses of water obtained from the mines, coal loaders and power stations indicated that trace elements are not present at levels that would a cause for concern. A comparison of these concentrations with the values quoted by the Japanese as target levels for public water bodies indicates that the quality of the run-off waters from coal stockpiles retained onsite meets the target values without further dilution on discharge.

Conclusions

Based on the data obtained in this project, there is no indication that trace elements present in the waters leached from coal stockpiles pose a risk to the environment. In fact, the concentrations of most trace elements are less than those recommended as trigger values (i.e. warranting further investigation) in "typical slightly moderately disturbed ecosystems" in the ANZECC/ARMCANZ Water Quality Guidelines.

The results indicated that the trace elements in waters running off stockpiles of Australian export coals have no significant environmental impact.