Link between DOC in near surface peat and stream water in an upland catchment

Clark, J. M.; Lane, Stuart N.; Chapman, P. J.; Adamson, J.

doi:10.1016/j.scitotenv.2007.11.002

Cited by 84 publications

(80 citation statements)

References 40 publications

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“…Many studies have so far investigated DOC exports from catchments and the controls thereof (Clark et al, 2010), but fewer studies are available investigating the DOC source areas and the DOC in runoff in a complementary approach (Worrall et al, 2008;Clark et al, 2008Clark et al, , 2012. If data from wetlands as DOC source areas are available, often no redox sensitive probing of predominant pore water species had been achieved, especially in monitoring programmes (Clark et al, 2005;Worrall and Burt, 2007).…”

Section: Discussionmentioning

confidence: 99%

DOC-dynamics in a small headwater catchment as driven by redox fluctuations and hydrological flow paths – are DOC exports mediated by iron reduction/oxidation cycles?

2013

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Dissolved organic carbon (DOC) exports from many catchments in Europe and North-America are steadily increasing. Several studies have sought to explain this observation. As possible causes, a decrease in acid rain or sulfate deposition, concomitant reductions in ionic strength and increasing temperatures were identified. DOC often originates from riparian wetlands; but here, despite higher DOC concentrations, ionic strength in pore waters usually exceeds that in surface waters. In the catchment under study, DOC concentrations were synchronous with dissolved iron concentrations in pore and stream water. This study aims at testing the hypothesis that DOC exports are mediated by iron reduction/oxidation cycles. Following the observed hydrographs, δ<sup>18</sup>O of water and DOC fluorescence, the wetlands were identified as the main source of DOC. Antecedent biogeochemical conditions, i.e., water table levels in the wetlands, influenced the discharge patterns of nitrate, iron and DOC during an event. The correlation of DOC with pH was positive in pore waters, but negative in surface waters; it was negative for DOC with sulfate in pore waters, but only weak in surface waters. Though, the positive correlation of DOC with iron was universal for pore and surface water. The decline of DOC and iron concentrations in transition from anoxic wetland pore water to oxic stream water suggests a flocculation of DOC with oxidising iron, leading to a drop in pH in the stream during high DOC fluxes. The pore water did not per se differ in pH. There is, thus, a need to consider processes more thoroughly of DOC mobilisation in wetlands when interpreting DOC exports from catchments. The coupling of DOC with iron fluxes suggested that increased DOC exports could at least, in part, be caused by increasing activities in iron reduction, possibly due to increases in temperature, increasing wetness of riparian wetlands, or by a shift from sulfate dominated to iron reduction dominated biogeochemical regimes

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Section: Discussionmentioning

confidence: 99%

DOC-dynamics in a small headwater catchment as driven by redox fluctuations and hydrological flow paths – are DOC exports mediated by iron reduction/oxidation cycles?

2013

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“…Bishop & Pettersson 1996), the decline in the annual flowweighted mean concentration in years of high rainfall was small compared to the magnitude of the increase in rainfall and overall C export (Clark et al 2007). Integrated analysis of soil and stream water concentrations in Cottage Hill Sike have shown a close coupling between the supply of DOC from near surface soil water (-1 to -10 cm depth) and DOC transported through the stream water network (Clark et al 2005, Clark et al 2008. On the basis of these data alone, it is difficult to determine whether increased DOC fluxes during years with the greatest rainfall were simply due to increased leaching and transport of DOC from soil to stream and/or increased supply of DOC during wet years due to a decline in consumption and respiration of DOC within the soil.…”

Section: Budgets and Fluxes At Moor House (N England)mentioning

confidence: 99%

Carbon balance of UK peatlands: current state of knowledge and future research challenges

Billett¹,

Charman²,

Clark³

et al. 2010

Clim. Res.

148

110

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“…Results from experimental studies (Freeman et al, 2004;Fenner et al, 2007;Hagedorn and Machwitz, 2007) support the hypothesis that elevated atmospheric CO 2 concentrations, along with increasing temperatures, can enhance DOC export from catchments due to increased primary production and DOC exudation from decaying plants, as well as due to changes in the composition of organic matter. Changes in hydrological regime such as increased discharge and changes of flow-path, and drought, also have an impact on concentrations and fluxes of dissolved organic carbon from catchments (Clark et al, 2008;Dawson et al, 2008;Jager et al, 2009). Worrall and Burt (2007) examined long-term data on DOC concentrations from 315 monitoring stations in Great Britain and found that, despite dominant increasing trends, DOC concentrations in some rivers in the south-west of the country PROCEEDINGS OF THE LATVIAN ACADEMY OF SCIENCES.…”

Section: Introductionmentioning

confidence: 99%