Acidity controls on dissolved organic carbon mobility in organic soils

Abstract

NERC has developed NORA to enable users to access research outputs wholly or partially funded by NERC. Copyright and other rights for material on this site are retained by the rights owners. Users should read the terms and conditions of use of this material at http://nora.nerc.ac.uk/policies.html#access This document is the author's final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. Some differences between this and the publisher's version remain. You are advised to consult the publisher's version if you wish to cite from this article.The definitive version is available at http://onlinelibrary.wiley.com Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. (Evans et al., 2005). In the water 55 industry, the high cost of DOC removal, and associated health risks through trihalomethane 56 formation (e.g. Chow et al., 2003), result in it being widely viewed as a pollutant. Changes in DOC 57 export to surface waters also affect aquatic energy supply and light regime (due to the 58 chromophoric properties of organic compounds), with potentially major consequences for the 59 functioning of aquatic ecosystems (Cole et al., 2001; Battin et al., 2009;Karlsson et al., 2010). When 60 first detected, DOC increases were thought to be a consequence of climate change (Freeman et al., 61 2001; Hejzlar et al., 2003;Worrall & Burt, 2007; Hongve et al., 2004), and thus evidence of 62 ecosystem destabilisation, contributing to terrestrial carbon losses (Bellamy et al., 2005). Some 63 recent studies also suggest high climate-sensitivity of DOC leaching (e.g. Larssen et al., 2011; Fenner 64 & Freeman, 2011 Oulehle & Hruska, 2009; Chapman et 72 al., 2010; Arvola et al., 2010; Clark et al., 2011; Ekström et al., 2011;SanClements et al., 2012) and 73 challenging (e.g. Roulet & Moore, 2006; Eimers et al., 2008;Worrall et al., 2008; Clair et al., 2008; 74 Sarkkola et al., 2009;Sarkkola et al., 2009;Zhang et al., 2010; Couture et al., 2011; Löfgren and 75 Zetterberg, 2011; Pärn & Mander, 2012) Figure S1b). 167At the Afon Gwy AWMN site, 50 km to the south, DOC has increased by 51% over the same period , pH range 3.9 to 4.4). In addition, the Peak District peat 237 and Migneint podzol sites exhibited some pre-treatment differences in mean DOC concentrations 238 between control and treatment plots ( Figure 1, Table 1). To explore underlying relationships 239 between DOC and pH change, we therefore standardised DOC concentrations by dividing mean DOC 240 for each treatment at each site and sampling interval by the corresponding pre-treatment mean. 241Deviation from this initial level due to treatment was quantified as the ratio of mean standardised habitats showed an increase in mean pH between the two surveys, and these mean values were 296 used to calculate RH std as above,...

Sensitivity of freshwaters to browning in response to future climate change

“…One obvious explanation for accelerated a 420 increases is an increased soil export of colored dissolved organic matter. Increased soil export of colored dissolved organic matter has previously been related to decreasing sulfate deposition (Ekström et al 2011;Evans et al 2012;Monteith et al 2007;Tipping and Hurley 1988). On a spatial scale we found no evidence that SO 4 -S concentrations have an influence on a 420 variation, probably because of an overriding effect of land-cover.…”

Seasonal contribution of terrestrial organic matter and biological oxygen demand to the Baltic Sea from three contrasting river catchments

“…Increasing DOM and water colour have profound effects on the ecosystem, changing the aquatic light environment and increasing the supply of allochthonous substrates for the planktonic communities. Several factors have been suggested as drivers of this increasing organic matter trend, from decreasing acidification (Evans et al, 2012;Monteith et al, 2007) changing hydrology and warming climates (Evans, 2005) to increasing ionic strength in soils (Hruška et al, 2009) and changes in land use (Garnett et al, 2000). The specific processes behind these trends are likely to at least partially vary regionally (Oni et al, 2013).…”

Developmental Changes in the Historical and Present-Day Trophic Status of Brown Water Lakes. Are Humic Water Bodies a Uniform Aquatic Ecosystem?

“…Simultaneously, over the past few decades, phenomena that are advantageous for the formation of humic lakes have been observed; namely, the intense export of organic matter to surface waters (Freeman et al 2001;Roulet and Moore 2006;Evans et al 2012).…”