The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed

Hernes, Peter J.; Spencer, Robert G. M.; Dyda, Rachael Y.; Pellerin, Brian A.; Bachand, Philip A.M.; Bergamaschi, Brian A.

doi:10.1016/j.gca.2008.07.031

Cited by 115 publications

(130 citation statements)

References 39 publications

(69 reference statements)

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“…Our high-frequency sampling during flooding periods at Baijiachuan gauge indicates that DOC concentrations were ~20% higher in the flooding periods than that in normal flow conditions. The positive correlation between DOC 375 export and hydrography demonstrates the enhanced leaching of organic matter from surface vegetation and organic-rich top soil layers (Hernes et al, 2008). Moreover, increased stream velocities in the flooding periods have reduced water residence time and consequently, even the labile fraction of DOC could be quickly transported downstream, resulting in a greater export of DOC (Raymond et al, 2016).…”

Section: Downstream Carbon Export At Catchment Outlet and Oc Burial 370mentioning

confidence: 99%

Riverine carbon export in the arid-semiarid Wuding River catchment on the Chinese Loess Plateau

Ran¹,

Tian²,

Fang³

et al. 2018

Preprint

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Riverine export of terrestrially-derived carbon represent a key component of the global carbon cycle. In this study we quantify the redistribution of riverine carbon within the 15Wuding catchment on the Chinese Loess Plateau. Export of dissolved organic and inorganic carbon (DOC and DIC) exhibited pronounced spatial and temporal variability. While the DOC concentration was spatially comparable within the catchment, it was generally higher in spring and summer than in autumn, especially in the loess subcatchment. This reflects the enhanced organic matter inputs from agricultural tillage in spring and from terrestrial ecosystems in 20 summer. DIC concentration in the loess subcatchment is significantly higher than that in the sandy subcatchment, due largely to dissolution of carbonates that are abundant in loess. In addition, content of particulate organic carbon (POC) shown strong seasonal variability with low values in the wet season owing to input of subsurface soils by gully erosion. The downstream carbon flux was (7±1.9)×10 10 g C year 1 and dominated by DIC and POC. Total CO2 emissions 25 from water surface were (3.7±0.5)×10 10 g C year 1 . Radiocarbon analysis revealed that the degassed CO2 was 8101890 years old, indicating the release of old carbon previously stored in soil horizons. Riverine carbon export in the Wuding catchment has been greatly modified by check dams. Our estimate shows that carbon burial through sediment storage was (7.8±4.1)×10 10 g C year 1 , representing 42% of the total riverine carbon export from terrestrial ecosystems on an 30 annual basis ((18.5±4.5)×10 10 g C year 1 ). Moreover, the riverine carbon export accounted for 16% of the catchment NEP. It appears that the magnitude of carbon sink of terrestrial ecosystems in this arid-semiarid catchment has been significantly offset by riverine carbon export.

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Section: Downstream Carbon Export At Catchment Outlet and Oc Burial 370mentioning

confidence: 99%

Riverine carbon export in the arid-semiarid Wuding River catchment on the Chinese Loess Plateau

Ran¹,

Tian²,

Fang³

et al. 2018

Preprint

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“…The ratio of coumaric to vanillic units (C / V) was investigated to trace the degradation state of lignin (Kögel, 1986). This ratio is commonly used to trace changes in DOM molecular composition during storm events (Dalzell et al, 2005;Hernes et al, 2008;Jeanneau et al, 2015). The TMAH reaction of CAR was used to analyse the free and terminal monosaccharides and to differentiate the hexoses (C6), deoxyhexoses (deoxyC6) and pentoses (C5) (Fabbri and Helleur, 1999;Grasset et al, 2009).…”

Section: Molecular Analysismentioning

confidence: 99%

“…Three possible origins could explain the modification of the stream DOM composition. The first one is proposed by Dalzell et al (2005) and Hernes et al (2008), who attributed the modifications of the stream DOM composition to the chemical equilibrium between soil particles in the stream. The experimental modelling of this process by shaking soil with water was found to produce small amounts of DOC compared to the increase in the DOC concentration measured over the different storm events.…”

Section: Are These Modifications Recorded In the Stream Dom?mentioning

confidence: 99%

“…With the establishment of storm flow, the transfer of DOM from the soil solution is assumed to be made conservatively via a pistonlike effect, as used for the endmember mixing analysis and isotopic studies (Bazemore et al, 1994;Klaus and McDonnell, 2013;Lambert et al, 2014). However, recent studies have demonstrated that this assumption about the conservative transport of DOM could be impacted by production mechanisms activated during storm flow which could possibly induce a modification of the DOM composition (Dalzell et al, 2005;Hernes et al, 2008). Molecular analyses of lignin biomarkers in stream water DOM have shown that the establishment of storm flow was responsible for an increase in the lignin concentrations and changes in the lignin composition where the lignin in streams during storm flows is less biodegraded compared to the base flow conditions.…”

Section: Introductionmentioning

confidence: 99%

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New molecular evidence for surface and sub-surface soil erosion controls on the composition of stream DOM during storm events

et al. 2017

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Abstract. Storm events are responsible for more than 60 % of the export of dissolved organic matter (DOM) from headwater catchments due to an increase in both the discharge and concentration. The latter was attributed to changing water pathways inducing the mobilization of DOM from the surface soil horizons. Recent molecular investigations have challenged this view and hypothesized (i) a contribution of an in-stream partition of organic matter (OM) between eroded particles and the dissolved fraction and (ii) the modification of the composition of soil DOM during storm events. To investigate these assumptions, soil solutions in the macropores, surface runoff and stream outlet were sampled at high frequency during three storm events in the KervidyNaizin catchment, part of the French critical zone observatory AgrHyS. The molecular composition of the DOM was analysed by thermally assisted hydrolysis and methylation (THM) with tetramethylammonium hydroxide (TMAH) coupled to a gas chromatograph and a quadrupole mass spectrometer. These analyses highlighted a modification of the DOM composition in soil solution controlled by the watertable dynamic and pre-event hydrological conditions. These findings fit with the mechanism of colloidal and particulate destabilization in the soil macroporosity. The different behaviour observed for lignins, carbohydrates and fatty acids highlights a potential chemical segregation based on their hydrophobicity. The composition of surface runoff DOM is similar to the DOM composition in soil solution and could be generated by the same mechanism. The DOM composition in both soil solution and surface runoff corresponds to the stream DOM composition observed during storm events. On the basis of these results, modifications of the stream DOM composition during storm events seem to be due to surface and sub-surface soil erosion rather than in-stream production.

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“…Impoundments drive the spatial and temporal variation of DOM [Mash et al, 2004;Duan et al, 2007;Kraus et al, 2011]. Reservoirs affect the source and processing of DOM [Groeger and Kimmel, 1984;Hernes et al, 2008;Kemenes et al, 2007], including increased degradation of DOM, as well as generation of new DOM via aquatic primary and secondary productivity [Wehr and Thorp, 1997;Bianchi et al, 2004;Mash et al, 2004]. In addition, reservoirs on some large, arid rivers have been shown to alter the quantity and composition of carbon in tailwaters and subsequent downstream reaches [Ulseth and Hall, 2015].…”

Section: Introductionmentioning

confidence: 99%

Impact of seasonality and anthropogenic impoundments on dissolved organic matter dynamics in the Klamath River (Oregon/California, USA)

Oliver

Spencer

Deas³

et al. 2016

JGR Biogeosciences

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Rivers play a major role in the transport and processing of dissolved organic matter (DOM). Disturbances that impact DOM dynamics, such as river impoundments and flow regulation, have consequences for biogeochemical cycling and aquatic ecosystems. In this study we examined how river impoundments and hydrologic regulation impact DOM quantity and quality by tracking spatial and seasonal patterns of DOM in a large, regulated river (Klamath River, USA). Dissolved organic carbon (DOC) concentrations decreased downstream and longitudinal patterns in DOC load varied by season. Export of DOM (as DOC) was largely driven by river flow, while DOM composition was strongly influenced by impoundments. Seasonal algal blooms in upstream lentic reaches provided a steady source of algal DOM that was processed in downstream reaches. DOM at upstream sites had an average spectral slope ratio (SR) > 1, indicating algal‐derived material, but decreased downstream to an average SR < 1, more indicative of terrestrial‐derived material. The increasingly terrestrial nature of DOM exported from reservoirs likely reflects degraded algal material that becomes increasingly more recalcitrant with distance from upstream source and additional processing. As a result, DOM delivered to free‐flowing river reaches below impoundments was less variable in composition. Downstream of impoundments, tributary influences resulted in increasing contributions of terrestrial DOM from the surrounding watershed. Removal of the four lower dams on the Klamath River is scheduled to proceed in the next decade. These results suggest that management should consider the role of impoundments on altering DOM dynamics, particularly in the context of dam removal.

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The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed

Cited by 115 publications

References 39 publications

Riverine carbon export in the arid-semiarid Wuding River catchment on the Chinese Loess Plateau

Riverine carbon export in the arid-semiarid Wuding River catchment on the Chinese Loess Plateau

New molecular evidence for surface and sub-surface soil erosion controls on the composition of stream DOM during storm events

Impact of seasonality and anthropogenic impoundments on dissolved organic matter dynamics in the Klamath River (Oregon/California, USA)

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