title: Long-term trends in water chemistry of acid-sensitive Swedish lakes show slow recovery from historic acidification.
abstract: Long-term (1987-2012) water quality monitoring in 36 acid-sensitive Swedish lakes shows slow recovery from historic acidification. Overall, strong acid anion concentrations declined, primarily as a result of declines in sulfate. Chloride is now the dominant anion in many acid-sensitive lakes. Base cation concentrations have declined less rapidly than strong acid anion concentrations, leading to an increase in charge balance acid neutralizing capacity. In many lakes, modeled organic acidity is now approximately equal to inorganic acidity. The observed trends in water chemistry suggest lakes may not return to reference conditions. Despite declines in acid deposition, many of these lakes are still acidified. Base cation concentrations continue to decline and alkalinity shows only small increases. A changing climate may further delay recovery by increasing dissolved organic carbon concentrations and sea-salt episodes. More intensive forest harvesting may also hamper recovery by reducing the supply of soil base cations.
authors.affiliation: Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), P.O. Box 7050, 750 07, Uppsala, Sweden, martyn.futter@slu.se.
authors.forename: Martyn N
authors.initials: MN
authors.lastname: Futter
authors.forename: Salar
authors.initials: S
authors.lastname: Valinia
authors.forename: Stefan
authors.initials: S
authors.lastname: Löfgren
authors.forename: Stephan J
authors.initials: SJ
authors.lastname: Köhler
authors.forename: Jens
authors.initials: J
authors.lastname: Fölster
mesh_terms: D004784:Environmental Monitoring; D006863:Hydrogen-Ion Concentration; D060106:Lakes / Q000032:analysis*; D012621:Seasons; D013548:Sweden; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality
chemical_list: D014874:Water Pollutants, Chemical