Long-term trends in water chemistry of acid-sensitive Swedish lakes show slow recovery from historic acidification.

Martyn N Futter,Stephan J Köhler,Salar Valinia,Jens Fölster,Stefan Löfgren

doi:10.1007/s13280-014-0563-2

Martyn N Futter, Stephan J Köhler + Show 3 more

Open Access

https://doi.org/10.1007/s13280-014-0563-2

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Journal: Ambio	Publication Date: Nov 15, 2014
Citations: 65	License type: CC BY 4.0

Affiliation: Swedish University of Agricultural Sciences

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.

Highlights

Acidification has adversely affected many surface waters in Europe, North America, and Asia
We focus on acidification-related parameters, dissolved organic carbon (DOC), and estimates of acid neutralizing capacity (ANC)
The trends in lake chemistry were consistent with a recovery from acidification

Summary

Introduction

Acidification has adversely affected many surface waters in Europe, North America, and Asia. In part due to these early studies, European legislation such as the Convention on Long-Range Transboundary Air Pollution (UNECE 2012) led to a [90 % reduction in anthropogenic sulfur deposition in Sweden in comparison to the peak in 1970–1980s (Bertills et al 2007). This large reduction in sulfur and a smaller reduction in nitrogen deposition should lead to recovery of surface waters from the chronic negative effects of acidification. Acidification of surface waters is still an ongoing issue in Sweden with concerns about the possibility of re-acidification that may be associated with more intensive forestry (Akselsson et al 2007)

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