The molecular properties of humic substances isolated from a UK upland peat system

Scott, Matthew J.; Jones, Malcolm N.; Woof, C.; Simon, Bernard; Tipping, Edward

doi:10.1016/s0160-4120(01)00100-3

Cited by 39 publications

(23 citation statements)

References 24 publications

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“…This would be consistent with an older TOC at lower flow, with lower SUVA and C:N (Hood et al, 2006). Mires have also been found to exhibit a temporal variation in the influence on the molecular weight in streams, with higher apparent molecular weight during summer (Scott et al, 2001). During the dry summer 2002 there was a decrease in specific discharge (power analysis 76% and bootstrapping 48%) between headwaters and downstream sites along O2, which coincided with decreases in SUVA, SVA and ε a , as well as for C:N, but not in molecular weight.…”

Section: Mosaic Of the Landscapesupporting

confidence: 62%

“…Mire streams had lower absorbance ratio and it increased during spring flood. These observations of SUVA and A 254 /A 365 could be coupled to temporal variation in molecular weight (Scott et al, 2001) and different temporal responses were found in mire and forest streams. Thus while there were distinct changes in TOC concentration and NOM character as flow rates changed, the spatial variation of TOC and to some extent even NOM character (Ågren et al, 2008); has been found to be less during high discharge situations than during low flow.…”

Section: Comparison Of the Nom Charactermentioning

confidence: 82%

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Landscape scale patterns in the character of natural organic matter in a Swedish boreal stream network

Temnerud

Düker²,

Karlsson

et al. 2009

Hydrol. Earth Syst. Sci.

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Section: Mosaic Of the Landscapesupporting

confidence: 62%

Section: Comparison Of the Nom Charactermentioning

confidence: 82%

Landscape scale patterns in the character of natural organic matter in a Swedish boreal stream network

Temnerud

Düker²,

Karlsson

et al. 2009

Hydrol. Earth Syst. Sci.

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“…A great deal of scientific effort has been made to examine the origin, composition, and fate of dissolved organic matter during the past few decades (Findlay and Sinsabaugh, 2003). Scott et al (2001) measured the fractionation composition of DOM and its seasonal changes in a small watershed dominated with organic soils. Humic acids exhibited a seasonal pattern of higher average molecular weight during the summer months.…”

Section: Introductionmentioning

confidence: 99%

Seasonal and photochemical changes of DOM in an acidified forest lake and its tributaries

Porcal

Hejzlar

Kopáček

2004

Aquatic Sciences - Research Across Boundaries

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The concentration, composition, and photochemical changes of dissolved organic matter (DOM) were evaluated in surface and bottom layers, and surface and subsurface tributaries of Plešné Lake, Bohemian Forest, Czech Republic, during one hydrological year. DOM was fractionated using the Amberlite XAD-8 and ion exchange resins into five fractions: hydrophilic neutrals, hydrophilic acids, hydrophilic and hydrophobic bases, hydrophobic acids, and hydrophobic neutrals. Photochemical transformations of DOM by photosynthetically active radiation (PAR) were tested with in-situ experiments using water from the surface tributary. The fraction composition of DOM was dominated by hydrophobic acids in all samples, with annual averages of 54 -58 % of DOM. The surface tributary differed from the subsurface one in higher and lower percentages of hydrophobic neu- Aquatic Sciencestrals and hydrophilic neutrals, respectively. The surface and bottom water of the lake did not significantly differ in the composition of DOM fractions despite significantly higher DOM concentrations at the bottom. The results of in-situ photochemical experiments showed the significance of PAR in photochemical as well as biological transformations of allochthonous DOM in this lake. The net rates of photo-production of DIC and photochemical plus biological degradation of DOC ranged from 0.3 to 0.6 and 0.6 to 4.3 µmol L -1 day -1 , respectively, with maximum values in late spring. The hydrophobic acids fraction and the remaining DOM fractions were decomposed biologically (in dark bottles) and by combined photochemical and biological degradation (in transparent bottles) at similar rates, resulting in unchanged fraction composition of DOM in the experiments.

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“…Biogeochemical processes include a range of geochemical (sorption and alteration of DOC by contact with soil surfaces) as well as biological (for example, microbial processing and plant exudation) interactions. Such processes together give a changing signal of DOC amount and composition between source soils (Scott et al, 2001;Stutter et al, 2007a, b) and during transport to the stream (Kaiser and Guggenberger, 2005;Hagedorn et al, 2000;Hood et al, 2006). In this study we employ a combination of techniques, examining: (i) DOC concentrations and simple compositional indicators (C-normalised UV Analysis, DOC:DON ratios), (ii) storm concentration vs. discharge hysteresis, (iii) an end-member mixing model elucidating flow pathway contributions to stream flow, and (iv) laboratory sorption equilibrations to characterise interactions between DOC-rich surface waters and subsoil taken from the catchment.…”

Section: Introductionmentioning

confidence: 99%

Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments

2012

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Abstract. Better knowledge of spatial and temporal delivery of dissolved organic carbon (DOC) in small catchments is required to understand the mechanisms behind reported longterm changes in C fluxes from some peatlands. We monitored two storms with contrasting seasons and antecedent conditions in a small upland UK moorland catchment. We examined DOC concentrations and specific UV absorbance (SUVA at 285 nm), together with solute concentrations required to undertake end-member mixing analyses to define dominant flow paths contributing to streamflow. This was combined with laboratory soil-solution equilibrations. We aimed to resolve how seasonal biogeochemical processing of DOC and flowpath changes in organo-mineral soils combine to affect DOC exported via the stream. An August storm following a dry period gave maximum DOC concentration of 10 mg l −1 . Small DOC:DON ratios (16-28) and SUVA (2.7-3.6 l mg −1 m −1 ) was attributed to filtration of aromatic compounds associated with up to 53 % B horizon flow contributions. This selective filtration of high SUVA DOC was reproduced in the experimental batch equilibration system. For a November storm, wetter antecedent soil conditions led to enhanced soil connectivity with the stream and seven times greater DOC stream-load (maximum concentration 16 mg l −1 ). This storm had a 63 % O horizon flow contribution at its peak, limited B horizon buffering and consequently more aromatic DOC (SUVA 3.9-4.5 l mg −1 m −1 and DOC:DON ratio 35-43). We suggest that simple mixing of waters from different flow paths cannot alone explain the differences in DOC compositions between August and November and biogeochemical processing of DOC is required to fully explain the observed stream DOC dynamics. This preliminary evidence is in contrast to other studies proposing hydrological controls on the nature of DOC delivered to streams. Although our study is based only on two storms of very different hydrological and biogeochemical periods, this should promote wider study of DOC biogeochemical alteration in headwaters so that this be better incorporated in modelling to predict the impacts of changes in DOC delivery to, and fate in, aquatic systems.

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The molecular properties of humic substances isolated from a UK upland peat system

Cited by 39 publications

References 24 publications

Landscape scale patterns in the character of natural organic matter in a Swedish boreal stream network

Landscape scale patterns in the character of natural organic matter in a Swedish boreal stream network

Seasonal and photochemical changes of DOM in an acidified forest lake and its tributaries

Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments

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