Since 1988, there has been, on average, a 91% increase in dissolved organic carbon (DOC) concentrations of UK lakes and streams in the Acid Waters Monitoring Network (AWMN). Similar DOC increases have been observed in surface waters across much of Europe and North America. Much of the debate about the causes of rising DOC has, as in other studies relating to the carbon cycle, focused on factors related to climate change. Data from our peat-core experiments support an influence of climate on DOC, notably an increase in production with temperature under aerobic, and to a lesser extent anaerobic, conditions. However, we argue that climatic factors may not be the dominant drivers of DOC change. DOC solubility is suppressed by high soil water acidity and ionic strength, both of which have decreased as a result of declining sulphur deposition since the 1980s, augmented during the 1990s in the United Kingdom by a cyclical decline in sea-salt deposition. Our observational and experimental data demonstrate a clear, inverse and quantitatively important link between DOC and sulphate concentrations in soil solution. Statistical analysis of 11 AWMN lakes suggests that rising temperature, declining sulphur deposition and changing sea-salt loading can account for the majority of the observed DOC trend. This combination of evidence points to the changing chemical composition of atmospheric deposition, particularly the substantial reduction in anthropogenic sulphur emissions during the last 20 years, as a key cause of rising DOC. The implications of rising DOC export for the carbon cycle will be very different if linked primarily to decreasing acid deposition, rather than to changes in climate, suggesting that these systems may be recovering rather than destabilising. Nomenclature:AWMN 5 UK Acid Waters Monitoring Network;CET 5 Central England Temperature Record; DOC 5 dissolved organic carbon; SAA 5 sum of acid anions; xSO 4 5 nonmarine sulphate

Soils are subject to varying degrees of direct or indirect human disturbance, constituting a major global change driver. Factoring out natural from direct and indirect human influence is not always straightforward, but some human activities have clear impacts. These include land-use change, land management and land degradation (erosion, compaction, sealing and salinization). The intensity of land use also exerts a great impact on soils, and soils are also subject to indirect impacts arising from human activity, such as acid deposition (sulphur and nitrogen) and heavy metal pollution. In this critical review, we report the state-of-the-art understanding of these global change pressures on soils, identify knowledge gaps and research challenges and highlight actions and policies to minimize adverse environmental impacts arising from these global change drivers. Soils are central to considerations of what constitutes sustainable intensification. Therefore, ensuring that vulnerable and high environmental value soils are considered when protecting important habitats and ecosystems, will help to reduce the pressure on land from global change drivers. To ensure that soils are protected as part of wider environmental efforts, a global soil resilience programme should be considered, to monitor, recover or sustain soil fertility and function, and to enhance the ecosystem services provided by soils. Soils cannot, and should not, be considered in isolation of the ecosystems that they underpin and vice versa. The role of soils in supporting ecosystems and natural capital needs greater recognition. The lasting legacy of the International Year of Soils in 2015 should be to put soils at the centre of policy supporting environmental protection and sustainable development.

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It is well known that atmospheric concentrations of carbon dioxide (CO2) (and other greenhouse gases) have increased markedly as a result of human activity since the industrial revolution. It is perhaps less appreciated that natural and managed soils are an important source and sink for atmospheric CO2 and that, primarily as a result of the activities of soil microorganisms, there is a soil-derived respiratory flux of CO2 to the atmosphere that overshadows by tenfold the annual CO2 flux from fossil fuel emissions. Therefore small changes in the soil carbon cycle could have large impacts on atmospheric CO2 concentrations. Here we discuss the role of soil microbes in the global carbon cycle and review the main methods that have been used to identify the microorganisms responsible for the processing of plant photosynthetic carbon inputs to soil. We discuss whether application of these techniques can provide the information required to underpin the management of agro-ecosystems for carbon sequestration and increased agricultural sustainability. We conclude that, although crucial in enabling the identification of plant-derived carbon-utilising microbes, current technologies lack the high-throughput ability to quantitatively apportion carbon use by phylogentic groups and its use efficiency and destination within the microbial metabolome. It is this information that is required to inform rational manipulation of the plant–soil system to favour organisms or physiologies most important for promoting soil carbon storage in agricultural soil.

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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,...

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Climate change in the UK is expected to cause increases in temperatures, altered precipitation patterns and more frequent and extreme weather events. In this review we discuss climate effects on dissolved organic matter (DOM), how altered DOM and water physico-chemical properties will affect treatment processes and assess the utility of techniques used to remove DOM and monitor water quality. A critical analysis of the literature has been undertaken with a focus on catchment drivers of DOM character, removal of DOM via coagulation and the formation of disinfectant by-products (DBPs). We suggest that: (1) upland catchments recovering from acidification will continue to produce more DOM with a greater hydrophobic fraction as solubility controls decrease; (2) greater seasonality in DOM export is likely in future due to altered precipitation patterns; (3) changes in species diversity and water properties could encourage algal blooms; and (4) that land management and vegetative changes may have significant effects on DOM export and treatability but require further research. Increases in DBPs may occur where catchments have high influence from peatlands or where algal blooms become an issue. To increase resilience to variable DOM quantity and character we suggest that one or more of the following steps are undertaken at the treatment works: a) 'enhanced coagulation' optimised for DOM removal; b) switching from aluminium to ferric coagulants and/or incorporating coagulant aids; c) use of magnetic ion-exchange (MIEX) pre-coagulation; and d) activated carbon filtration post-coagulation. Fluorescence and UV absorbance techniques are highlighted as potential methods for low-cost, rapid on-line process optimisation to improve DOM removal and minimise DBPs.