Ecological and geochemical impact of an underground colliery waste discharge to a river

Abstract

Abstract This study investigated the impact of mine wastewater disposal to a nearby river (the Bargo River). Mean electrical conductivity (EC) increased in surface waters below the mine discharge, rising more than six times from (219.5 μS/cm) upstream to 1551 μS/cm below the waste inflow. River pH increased from 7.12 (upstream) to 8.67 (downstream). The mine discharge strongly modified the ionic composition of the river. The mean concentration of several metals in the river were increased due to the mine wastewater. Nickel increased from 1.0 μg/L (upstream) to 32 μg/L (downstream). Zinc increased from 3.5 μg/L (upstream) to 23.5 μg/L (downstream). Our study also assessed the biological uptake of pollutants by growing weeping willow (Salix babylonica) cuttings in mine wastewater and contrasting to ‘control’ cuttings grown in river water from upstream of the mine. After growing in the laboratory for several weeks, the cuttings accumulated metals, dominated by barium, strontium and lithium. Results from the study constituted one of the most detailed geochemical and ecological studies investigating the impact of the coal mine waste discharge to an Australian river. Recommendations are suggested for improved regulation of the mine discharge to reduce its wastewater environmental impact.