Climatic and watershed controls of dissolved organic matter variation in streams across a gradient of agricultural land use

Shang, Peng; Lu, YueHan; Du, Yingxun; Jaffé, Rudolf; Findlay, Robert H.; Wynn, Anne

doi:10.1016/j.scitotenv.2017.08.322

Cited by 97 publications

(47 citation statements)

References 81 publications

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“…In addition, agricultural practices will also significantly alter DOM composition in headwater streams. 26,33,34,62,63 Thus, it is likely that DOM abundance, composition, and reactivity (in situ processing) are different in anthropogenically impacted headwaters compared to those in natural systems. As such, watershed land use may be the dominant driver and a better indicator of DOM composition in an anthropogenically disturbed system by comparison to the traditional RCC.…”

Section: Discussionmentioning

confidence: 99%

Controls of Land Use and the River Continuum Concept on Dissolved Organic Matter Composition in an Anthropogenically Disturbed Subtropical Watershed

Roebuck

Seidel

Dittmar

et al. 2019

Environ. Sci. Technol.

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About 250 Tg of dissolved organic carbon are annually transported from inland waters to coastal systems making rivers a critical link between terrestrial and ocean carbon pools. During transport through fluvial systems, various biogeochemical processes selectively remove or transform labile material, effectively altering the composition of dissolved organic matter (DOM) exported to the ocean. The river continuum concept (RCC) has been historically used as a model to predict the fate and quality of organic matter along a river continuum. However, the conversion of natural landscapes for urban and agricultural practices can also alter the sources and quality of DOM exported from fluvial systems, and the RCC may be significantly limited in predicting DOM quality in anthropogenically impacted watersheds. Here, we studied DOM dynamics in the Altamaha River watershed in Georgia, USA, a fluvial system where headwater streams are highly impacted by anthropogenic activities. The primary goal of this study was to quantitatively assess the importance of both the RCC and land use as environmental drivers controlling DOM composition. Land use was a stronger predictor of spatial variation (∼50%) in DOM composition defined by both excitation−emission matrix−parallel factor analysis (EEM−PARAFAC) and ultrahigh-resolution mass spectrometry. This is compared to an 8% explained variability that can be attributed to the RCC. This study highlights the importance of incorporating land use among other controls into the RCC to better predict the fate and quality of DOM exported from terrestrial to coastal systems.

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Section: Discussionmentioning

confidence: 99%

Controls of Land Use and the River Continuum Concept on Dissolved Organic Matter Composition in an Anthropogenically Disturbed Subtropical Watershed

Roebuck

Seidel

Dittmar

et al. 2019

Environ. Sci. Technol.

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“…For instance, urbanized headwaters are engineered to include significant drainage networks and channelization, a process that may induce low order streams to behave more similarly to high order streams 30 . In addition, DOM composition in headwater streams have been found to be strongly influenced not only by urbanization, but also agricultural practices [69][70][71] and forest management 26 . Thus, we hypothesize that DOM sources and in-situ processing may be enhanced in anthropogenically impacted headwaters, which may further explain the lack of significant variability in molecular diversity observed along the Altamaha River continuum.…”

Section: Identification Of Parafac Componentsmentioning

confidence: 99%

“…However, the relative contributions of in-stream processing with stream order on DOM composition are not well understood. In some cases, stream order has shown to have little effect on predicting stream DOM composition 78 , whereas in others, clear processing and degradation of DOM has been observed along an increasing stream order gradient 71,79 . For this study, we show clear compositional shifts in DOM composition with respect to increasing stream order indicating that in-stream processing of DOM (microbial/photochemical/etc) may have significant influence on DOM composition in the Altamaha River; however, the evident anthropogenic disturbances in the upper watershed (urban Atlanta, agricultural activity)…”

Section: Identification Of Parafac Componentsmentioning

confidence: 99%

“…General patterns show clear downstream shifts in DOM composition represented by a higher degree of aromaticity as noted by the enrichment of polycondensed aromatic and polyphenolic like compounds (Figure 6 Figure 6.3). The enrichment of autochthonously derived DOM in both urban and agricultural areas has been linked to higher nutrient loads [87][88][89] which fuel primary productivity 34 and production of more bioavailable DOM 33,67,71 . In the Altamaha (Table 6.1).…”

Section: Land Use Controls On Dom Compositionmentioning

confidence: 99%

“…Our results are generally consistent with other studies as well that suggest that agricultural activity enhances the export of dissolved organic nitrogen along with a greater contribution of autochthonously derived DOM 66,76 . However, there is a need to recognize that the effects of agricultural land use on DOM composition is not completely clear as contrasting reports have also suggested that agriculturally impacted watersheds export a higher degree of aromatic, structurally complex material 71,[91][92] .…”

Section: Land Use Controls On Dom Compositionmentioning

confidence: 99%

See 2 more Smart Citations

Environmental Dynamics of Dissolved Organic Matter and Dissolved Black Carbon in Fluvial Systems: Effects of Biogeochemistry and Land Use

Roebuck¹,

Alan²

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River network travel time is correlated with dissolved organic matter composition in rivers of the contiguous United States

Hosen

Allen

Amatuli

et al. 2021

Hydrological Processes

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Most terrestrial allochthonous organic matter enters river networks through headwater streams during high flow events. In headwaters, allochthonous inputs are substantial and variable, but become less important in streams and rivers with larger watersheds. As allochthonous dissolved organic matter (DOM) moves downstream, the proportion of less aromatic organic matter with autochthonous characteristics increases. How environmental factors converge to control this transformation of DOM at a continental scale is less certain. We hypothesized that the amount of time water has spent travelling through surface waters of inland systems (streams, rivers, lakes, and reservoirs) is correlated to DOM composition. To test this hypothesis, we used established river network scaling relationships to predict relative river network flow-weighted travel time (FWTT) of water for 60 stream and river sites across the contiguous United States (3090 discrete samples over 10 water years). We estimated lentic contribution to travel times with upstream in-network lake and reservoir volume. DOM composition was quantified using ultraviolet and visible absorption and fluorescence spectroscopy. A combination of FWTT and lake and reservoir volume was the best overall predictor of DOM composition among models that also incorporated discharge, specific discharge, watershed area, and upstream channel length. DOM spectral slope ratio (R 2 = 0.77) and Freshness Index (R 2 = 0.78) increased and specific ultraviolet absorbance at 254 nm (R 2 = 0.68) and Humification Index (R 2 = 0.44) decreased across sites as a function of FWTT and upstream lake volume. This indicates autochthonous-like DOM becomes continually more dominant in waters with greater FWTT. We assert that river FWTT can be used as a metric of the continuum of DOM composition from headwaters to rivers. The nature of the changes to DOM composition detected suggest this continuum is driven by a combination of photo-oxidation, biological processes, hydrologically varying terrestrial subsidies, and aged groundwater inputs.

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Climatic and watershed controls of dissolved organic matter variation in streams across a gradient of agricultural land use

Cited by 97 publications

References 81 publications

Controls of Land Use and the River Continuum Concept on Dissolved Organic Matter Composition in an Anthropogenically Disturbed Subtropical Watershed

Controls of Land Use and the River Continuum Concept on Dissolved Organic Matter Composition in an Anthropogenically Disturbed Subtropical Watershed

Environmental Dynamics of Dissolved Organic Matter and Dissolved Black Carbon in Fluvial Systems: Effects of Biogeochemistry and Land Use

River network travel time is correlated with dissolved organic matter composition in rivers of the contiguous United States

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