title: Hydrochloric acid: an overlooked driver of environmental change.
abstract: 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 (HCl), 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 HCl emissions within 20 years. Long-term precipitation, surface water, and soil solution data suggest that the near-disappearance of HCl from deposition could account for 30-40% of chemical recovery from acidification during this time, affecting both near-source and remote areas. Because HCl is highly mobile in reducing environments, it is a more potent acidifier of wetlands than S or N, and HCl may have been the major driver of past peatland acidification. Reduced HCl 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, HCl should be recognized as a potentially significant constituent of resulting emissions, with distinctive ecosystem impacts.
authors.affiliation: Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor LL57 2UW, United Kingdom. cev@ceh.ac.uk
authors.forename: Chris D
authors.initials: CD
authors.lastname: Evans
authors.forename: Don T
authors.initials: DT
authors.lastname: Monteith
authors.forename: David
authors.initials: D
authors.lastname: Fowler
authors.forename: J Neil
authors.initials: JN
authors.lastname: Cape
authors.forename: Susan
authors.initials: S
authors.lastname: Brayshaw
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry* / Q000633:toxicity; D000397:Air Pollution / Q000706:statistics & numerical data; D057486:Carbon Cycle / Q000187:drug effects; D002713:Chlorine / Q000032:analysis; D017753:Ecosystem; D004777:Environment; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry; D006851:Hydrochloric Acid / Q000032:analysis / Q000737:chemistry* / Q000633:toxicity; D006863:Hydrogen-Ion Concentration; D012987:Soil / Q000737:chemistry
chemical_list: D000393:Air Pollutants; D012987:Soil; D002713:Chlorine; D006851:Hydrochloric Acid