Hydrochloric Acid: An Overlooked Driver of Environmental Change

摘要

Research on the ecosystem impacts of acidifying pollutants, and measures to control them, has focused almost exclusively on sulfur (S) and nitrogen (N) compounds. Hydrochloric acid (HC1), although emitted by coal burning, has been overlooked as a driver of ecosystem change because most of it was considered to redeposit close to emission sources rather than in remote natural ecosystems. Despite receiving little regulatory attention, measures to reduce S emissions, and changes in energy supply, have led to a 95% reduction in United Kingdom HC1 emissions within 20 years. Long-term precipitation, surface water, and soil solution data suggest that the near-disappearance of HC1 from deposition could account for 30-40% of chemical recovery from acidification during this time, affecting both near-source and remote areas. Because HC1 is highly mobile in reducing environments, it is a more potent acidifier of wetlands than S or N, and HC! may have been the major driver of past peatland acidification. Reduced HC1 loadings could therefore have affected the peatland carbon cycle, contributing to increases in dissolved organic carbon leaching to surface waters. With many regions increasingly reliant on coal for power generation, HC1 should be recognized as a potentially significant constituent of resulting emissions, with distinctive ecosystem impacts.