Chemical trends at lakes and streams in the UK Acid Waters Monitoring Network, 1988-2000: Evidence for recent recovery at a national scale

Abstract

A detailed trend analysis of 12 years of data (1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000) for 22 surface waters in acid-sensitive regions of the United Kingdom, in which individual site data have been combined to identify national-scale trends, has shown strong common patterns of temporal variation. Results suggest a widespread reduction in sulphate concentrations, hydrogen ion and inorganic aluminium species, and increases in acid neutralising capacity. Many chemical changes have not been linear. However, the first five years were characterised by high concentrations of marine ions and relatively stable pollutant sulphate concentrations and the remaining period by lower concentrations of marine ions and declining sulphate. Genuine 'recovery', in terms of declining acidity in response to reduced anthropogenic sulphur deposition is only apparent, therefore, for the latter part of the monitoring period. Reductions in calcium concentrations appear to have partially offset the influence of sulphate reductions on acidity, as have increases in organic acidity associated with strong and widespread rising trends in dissolved organic carbon. Fluctuations in a number of climatic factors over the monitoring period have led to significant inter-annual variability in nitrate, which exhibits little longterm trend, marine ions and acidity, emphasising the need for long monitoring periods if underlying trends are to be correctly identified.

An Assessment of the potential impact of the Gothenburg Protocol on surface water chemistry using the dynamic MAGIC model at acid sensitive sites in the UK

“…6). ANC is predicted to have increased slightly at Round Loch of Glenhead (site 7) and Lochnagar (site 4) and this is in line with observations from 1988-2000 (Evans and Monteith, 2001). Many of the sites, on the other hand, are predicted to have further acidified since 1970 but all of these have undergone significant afforestation.…”

Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales

“…Emissions of SO x , and to a lesser extent NO x and ammonium, account for the acid loading to these catchments, and although SO x emissions are declining owing to legislative changes the relative importance of nitrogen emissions has increased (Skeffington, 2002). The detrimental effects of nitrogen deposition on surface water chemistry have been widely reported both in Europe and North America (Evans and Monteith, 2001;Stoddard, 1994), however recent improvements caused by emission targets have occurred (Skjelkvale et al, 2005). While most studies have focussed on the effect of dissolved inorganic nitrogen (DIN) in terms of nitrogen cycling and water quality, the role of dissolved organic nitrogen (DON) in nitrogen cycling and bioavailability has also been shown to be important in a range of environments (Scott et al, 2007;Seitzinger et al, 2005;Jones et al, 2004;Willett et al, 2004;Seitzinger and Sanders, 1997;Carlsson and Graneli, 1993).…”

Element fluxes in watershed-lake ecosystems recovering from acidification: Čertovo Lake, the Bohemian Forest, 2001–2005

“…4) due to continuous depletion of S pools accumulated in soils over the decades of high S deposition (Kopáček et al, 2001b). A significant increasing trend in DOC concentrations in the Bohemian Forest lakes during the last 15 years is probably associated with an elevated terrestrial DOC export (as in other areas recovering from acidification; e.g., Evans & Monteith, 2001), and we suspect it to bring more Al o to the lakes.…”