Direct and indirect effects of increasing dissolved organic carbon levels on pH in lakes recovering from acidification

Abstract

[1] In this study, we examine the impact of increasing concentrations of dissolved organic carbon (DOC) on the recovery from acidification for 66 lakes in Southern Sweden. The lakes are small, weakly buffered, and have all been affected by acidifying deposition. A majority of the lakes (∼75%) showed an increase in DOC concentrations between 1990 and 2008. The method used in this study was to model pH in 2008 from DOC, acid neutralizing capacity, pCO 2 (partial carbon dioxide pressure), and Al speciation, using both the DOC observed in 2008 and the "unelevated" DOC of 1990. Furthermore, we consider the indirect effects of increasing DOC on acidity, i.e., the ancillary effects from DOC on pCO 2 , Al transport and speciation, and release of base cations (BCs). Our results indicate that the DOC increase in the latest decades has retarded the recovery from acidification by 0.13 pH units (median for all lakes) and by more than 1 unit for individual lakes. The effects of elevated pCO 2 and BC concentrations accompanying the DOC increase compensated for each other for the average lake, whereas the effects of higher Al transport on pH were minor. The estimate of the amount of BCs released with the organic anions is however uncertain, and further studies on this topic are needed.Citation: Erlandsson, M., N. Cory, S. Köhler, and K. Bishop (2010), Direct and indirect effects of increasing dissolved organic carbon levels on pH in lakes recovering from acidification,

Measuring the relative resilience of subarctic lakes to global change: redundancies of functions within and across temporal scales

“…), which suppresses recovery of pH and alkalinity (Erlandsson et al . ). This may explain the long‐term stability of pH and alkalinity and decreasing water clarity observed in hemiboreal lakes.…”

Contribution of climate change and rising CO2 to terrestrial carbon balance in East Asia: A multi-model analysis

“…These models have been extensively validated against measured carbon fluxes at particular sites around the world (Krinner et al, 2005;Sitch et al, 2003); they also realistically simulate observed historical change in leaf area index (LAI) and transient responses of carbon fluxes to climate variability (Lutch et al, 2002;Ciais et al, 2005;Piao et al, 2006Piao et al, , 2008. Tao and Zhang (2010) have also validated LPJ derived NPP and carbon storage against observation in China. Terrestrial NEP fluxes from ORCHIDEE have also been successfully validated against measured carbon fluxes at particular sites in China (Tan et al, 2009;Peng et al, in prepare).…”

“…The meteorological data (air temperature, precipitation, wet day frequency, diurnal temperature range, cloud cover, relative humidity of the air, and wind speed) with spatial resolution of 0.5°for 1901-2002 were supplied by the Climatic Research Unit (CRU), School of Environmental Sciences, University of East Anglia, U.K. (Mitchell and Jones, 2005), while annual global atmospheric CO 2 concentrations for the period 1901-2002 were based on data from ice-core records and atmospheric observations (Keeling and Whorf, 2005). Both ORCHIDEE and SDGVM used prescribed actual vegetation (Loveland et al, 2000), while LPJ calculated its own vegetation distribution (Sitch et al, 2003;Tao and Zhang, 2010). Soil texture distribution information was derived from the Zobler (1986) soil texture map.…”

Simulating Dissolved Organic Carbon Dynamics at the Swedish Integrated Monitoring Sites with the Integrated Catchments Model for Carbon, INCA-C

“…However, over-reliance on simple models and purely statistical criteria may lead to overly simplistic views of the environment. If nothing else, it can be argued that more than 30 years of research into surface water DOC, and its links to acidification, acidity, climate and hydrology (Krug and Frink 1983;Laudon et al 1999;Erlandsson et al 2008Erlandsson et al , 2010Lepistö et al 2008;Clark et al 2010;Haaland et al 2010;Haei et al 2010;Löfgren et al 2010b;Löfgren and Zetterberg 2011), has shown that numerous factors influence or covary with surface water DOC. So, we must conclude that, on the basis of our current understanding, reality is over-determined but that models can be a useful tool for environmental hypothesis testing and understanding.…”

“…Changes in [DOC] also affect the timing and magnitude of thermal stratification in lakes, with consequent effects on ecological processes and mercury dynamics (Forsius et al 2010). In addition, increasing [DOC] has been shown to affect pH recovery in many surface waters (Erlandsson et al 2010).…”