Long-Term Increase in Dissolved Organic Carbon in Streamwaters in Norway Is Response to Reduced Acid Deposition

Citations Over TimeTop 10% of 2007 papers

Abstract

Concentrations of dissolved organic carbon (DOC) in freshwaters have increased significantly in Europe and North America, but the driving mechanisms are poorly understood. Here, we test if the significant increase in TOC (total organic carbon, 90-95% DOC) in three acid-sensitive catchments in Norway of 14 to 36% between 1985 and 2003 is related to climate, hydrology, and/or acid deposition. Catchment TOC export increased between 10 and 53%, which was significant at one site only. The seasonal variation in TOC was primarily climatically controlled, while the deposition of SO4 and NO3--negatively related to TOC--explained the long-term increase in TOC. We propose increased humic charge and reduced ionic strength--both of which increase organic matter solubility--as mechanistic explanations for the statistical relation between reduced acid deposition and increased TOC. Between 1985 and 2003, ionic strength decreased significantly at all sites, while the charge density of TOC increased at two of the sites from 1-2 meq g(-1) C to about 5 meq g(-1) C and remained constant at the third site at 5 meq g(-1) C. The solubility of organic matter is discussed in terms of the pH-dependent deprotonation of carboxylic groups and the ionic strength-dependent repulsion of organic molecules.

Related Papers

• → Ongoing increases in dissolved organic carbon are sustained by decreases in ionic strength rather than decreased acidity in waters recovering from acidic deposition(2020)55 cited
• → Direct and indirect effects of increasing dissolved organic carbon levels on pH in lakes recovering from acidification(2010)54 cited
• → Climatically induced rapid acidification of a softwater seepage lake(1990)67 cited
• → Long-term trends in stream chemistry and biology in North-East Scotland: Evidence for recovery(1995)20 cited
• → Potential future effects of current levels of sulfur deposition on stream chemistry in the southern blue ridge mountains, U.S.(1990)14 cited