River sediment quality assessment using sediment quality indices for the Sydney basin, Australia affected by coal and coal seam gas mining

Coal mining activities in the Sydney basin have been historically associated with significant environmental impacts. The region is facing more recent coal seam gas extraction activities and the synergetic environmental impacts of the newmining activities are still largely unknown. The aim of this study was to provide environmental assessment of river sediments comparing upstreamto downstreamareas relative to industrial-discharge sites associated with coal and coal-seam-gas extraction within the Sydney basin. Various contaminants were measured to determine the sediment quality according to the Australian and New Zealand Environment and Conservation Council (ANZECC) guidelines. Arsenic, nickel and zinc were the main sediment contaminants in downstream samples exceeding the ANZECC guidelines. Degree of contamination (Cd), geoaccumulation index (Igeo), enrichment factor (EF), pollution load index (PLI) and sediment environmental toxicity quotients' increment in downstreamsediment were estimated for the studied areas. Toxicology indices ofmetals present in the sediments near industrial discharge siteswere used as an additional tool to compare the level of environmental effectswith their increment. The study revealed that the sediments from coal mining sites were highly affected by increased concentrations of manganese, zinc, cobalt, nickel and barium. The sediments associated with coal mining activities were found to be substantially more affected than the sediments near coal seam gas production sites, mainly attributed to the differentwastewater discharge licencing requirements. The approach applied in this study can be used as an additional model to assess the contribution of industrial and mining activities on aquatic environments.