Spatial controls on dissolved organic carbon in upland waters inferred from a simple statistical model

Abstract

Because of the implications for drinking water treatment and supply there is increasing interest in the potential for mitigation through local land management, and for forecasting the likely impact of environmental change.However, the dominant controls on DOC production remain unresolved, hindering the establishment of appropriate reference levels for specific locations. Here we demonstrate that spatial variation in long-term average DOC levels draining upland UK catchments is highly predictable using a simple multiple logistic regression model comprising variables representing wetland soil cover, rainfall, altitude, catchment sensitivity to acidification, and current acid deposition. A negative relationship was observed between DOC concentration and altitude that, fro catchments dominated by organo-mineral soils, is plausibly explained by the combined effects of changing net primary production and temperature-dependent decomposition.However, the magnitude of the altitude effect was considerably greater for catchments with a high proportion of wetland cover, suggesting that additional controls influence these sites such as impeded respiratory loss of carbon in wet soils and/or an increased susceptibility to water level drawdown at lower altitudes. The model suggests 1) that continuing reductions in sulphur deposition on acid sensitive organo-mineral soils, will drive further significant increases in DOC and, 2) given the differences in the magnitude of the observed altitude-DOC relationships, that DOC production from catchments with peat-dominated soils may be more sensitive to climate change than those dominated by mineral soils. However, given that mechanisms remain unclear, the latter warrants further investigation.

Importance of within-lake processes in affecting the dynamics of dissolved organic carbon and dissolved organic and inorganic nitrogen in an Adirondack forested lake/watershed

“…Most of the Adirondack lakes including Arbutus Lake have shown significant decreases in sulfate concentration (Park et al, 2003; 0.87 * * * Driscoll et al, 2007). The effects of changes of acidic deposition on surface water, including trends in DOC concentrations, have been documented in North America and Europe (Erlandsson et al, 2011;Evans et al, 2007;Kalbitz et al, 2000;Monteith et al, 2007Monteith et al, , 2015Mulder et al, 2001). However, for Arbutus Lake the effects of changes in acidic deposition may be less evident due to its relatively high pH (∼ 6.7) and ANC (∼ 77 µeq L −1 ) values and base status (Foster et al, 1992;Johnson and Lindberg, 1992;Mitchell et al, 2001;Chen et al, 2004;NYSERDA, 2011).…”

“…There has been considerable discussion on the mechanisms driving recent increases of DOC in acid-sensitive surface waters in North America and Europe Erlandsson et al, 2011;Evans et al, 2007;Monteith et al, 2007Monteith et al, , 2015. For example, Monteith et al (2007) suggested that the recovery of the previous acidification of surface water in response to decreased acidic deposition might result from an increase in the solubility of soil organic matter due to the change of pH, aluminum and ionic strength (Kalbitz et al, 2000;Mulder et al, 2001).…”

Heavy Rainfall Impacts on Trihalomethane Formation in Contrasting Northwestern European Potable Waters

“…In these high rainfall environments, peat soils dominate many reservoir catchments. This soil type is almost entirely organic and leaches high concentrations of DOC to freshwaters; DOC export has been shown to be linearly related to the percentage cover of peatlands within the catchment (Urban et al, 1989; Dillon and Molot, 1997; Monteith et al, 2015). Because long‐term increases in DOC have been greatest in regions where many organic soils such as peats dominate, there are concerns within the UK water industry that the treatment of water will become progressively more costly (Ritson et al, 2014).…”

A Water Framework Directive-compatible metric for assessing acidification in UK and Irish rivers using diatoms

“…Similarly, TOC concentration is primarily an intrinsic feature of the site that is controlled by catchment characteristics (see, for example Monteith et al, 2015). TOC concentrations have approximately doubled at most UWMN sites over the first 2 decades of monitoring, a feature that is thought to be directly linked to reductions in acid deposition .…”