Biological lability of dissolved organic carbon in stream water and contributing terrestrial sources

2013 ◽  
Vol 32 (4) ◽  
pp. 1219-1230 ◽  
Author(s):  
Christine McLaughlin ◽  
Louis A. Kaplan
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Stream Water

Elucidating sources and pathways of dissolved organic carbon in a small, forested catchment – A qualitative assessment of stream, soil and shallow groundwater

2021 ◽  
Author(s):  
Katharina Blaurock ◽  
Phil Garthen ◽  
Benjamin S. Gilfedder ◽  
Jan H. Fleckenstein ◽  
Stefan Peiffer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Soil Water ◽  
Riparian Zone ◽  
Stream Water ◽  
Shallow Groundwater ◽  
Drinking Water Treatment ◽  
Base Flow ◽  
Qualitative Assessment ◽  
Fluorescence Characteristics

<p>Dissolved organic carbon (DOC) constitutes the biggest portion of carbon that is exported from soils. During the last decades, widespread increases in DOC concentrations of surface waters have been observed, affecting ecosystem functioning and drinking water treatment. However, the hydrological controls on DOC mobilization are still not completely understood.</p><p>We sampled two different topographical positions within a headwater catchment in the Bavarian Forest National Park: at a steep hillslope (880 m.a.s.l.) and in a flat and wide riparian zone (770 m.a.s.l.). By using piezometers, pore water samplers (peepers) and in-stream spectrometric devices we measured DOC concentrations as well as DOC absorbance (A<sub>254</sub>/A<sub>365</sub> and SUVA<sub>254</sub>) and fluorescence characteristics (fluorescence and freshness indices) in soil water, shallow ground water and stream water in order to gain insights into the DOC source areas during base-flow and during precipitation events.</p><p>High DOC concentrations (up to 80 mg L<sup>-1</sup>) were found in soil water from cascading sequences of small ponds in the flat downstream part of the catchment that fill up temporarily. The increase of in-stream DOC concentrations during events was accompanied by changing DOC characteristics at both locations, for example increasing freshness index values. As the freshness index values were approaching the values found in the DOC-rich ponds in the riparian zone, these ponds seem to be important DOC sources during events. Our preliminary results point to a change of flow pathways during events.</p>

scholarly journals Diurnal Patterns in Solute Concentrations Measured with In Situ UV-Vis Sensors: Natural Fluctuations or Artefacts?

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 859
Author(s):  
Suzanne R. Jacobs ◽  
Björn Weeser ◽  
Mariana C. Rufino ◽  
Lutz Breuer
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Stream Water ◽  
Visible Spectrum ◽  
Mobile Sensor ◽  
Stream Water Quality ◽  
High Resolution Data ◽  
Diurnal Patterns ◽  
Solute Dynamics

In situ spectrophotometers measuring in the UV-visible spectrum are increasingly used to collect high-resolution data on stream water quality. This provides the opportunity to investigate short-term solute dynamics, including diurnal cycling. This study reports unusual changes in diurnal patterns observed when such sensors were deployed in four tropical headwater streams in Kenya. The analysis of a 5-year dataset revealed sensor-specific diurnal patterns in nitrate and dissolved organic carbon concentrations and different patterns measured by different sensors when installed at the same site. To verify these patterns, a second mobile sensor was installed at three sites for more than 3 weeks. Agreement between the measurements performed by these sensors was higher for dissolved organic carbon (r > 0.98) than for nitrate (r = 0.43–0.81) at all sites. Higher concentrations and larger amplitudes generally led to higher agreement between patterns measured by the two sensors. However, changing the position or level of shading of the mobile sensor resulted in inconsistent changes in the patterns. The results of this study show that diurnal patterns measured with UV-Vis spectrophotometers should be interpreted with caution. Further work is required to understand how these measurements are influenced by environmental conditions and sensor-specific properties.

scholarly journals Changes in discharge and solute dynamics between hillslope and valley-bottom intermittent streams

2012 ◽  
Vol 16 (6) ◽  
pp. 1595-1605 ◽  
Author(s):  
S. Bernal ◽  
F. Sabater
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Stream Water ◽  
Valley Bottom ◽  
Solute Fluxes ◽  
Nitrate Export ◽  
Carbon And Nitrogen Dynamics ◽  
Reactive Solutes ◽  
Monthly Discharge ◽  
Solute Dynamics

Abstract. To gain understanding on how alluvial zones modify water and nutrient export from semiarid catchments, we compared monthly discharge as well as stream chloride, carbon, and nitrogen dynamics between a hillslope catchment and a valley-bottom catchment with a well-developed alluvium. Stream water and solute fluxes from the hillslope and valley-bottom catchments showed contrasting patterns between hydrological transitions and wet periods, especially for bio-reactive solutes. During transition periods, stream water export decreased >40% between the hillslope and the valley bottom coinciding with the prevalence of stream-to-aquifer fluxes at the alluvial zone. In contrast, stream water export increased by 20–70% between the hillslope and valley-bottom catchments during wet periods. During transition periods, stream solute export decreased by 34–97% between the hillslope and valley-bottom catchments for chloride, nitrate, and dissolved organic carbon. In annual terms, stream nitrate export from the valley-bottom catchment (0.32 ± 0.12 kg N ha−1 yr−1 [average ± standard deviation]) was 30–50% lower than from the hillslope catchment (0.56 ± 0.32 kg N ha−1 yr−1). The annual export of dissolved organic carbon was similar between the two catchments (1.8 ± 1 kg C ha−1 yr−1). Our results suggest that hydrological retention in the alluvial zone contributed to reduce stream water and solute export from the valley-bottom catchment during hydrological transition periods when hydrological connectivity between the hillslope and the valley bottom was low.

scholarly journals Spatio-temporal controls of dissolved organic carbon stream water concentrations

2018 ◽  
Vol 566 ◽  
pp. 205-215 ◽  
Author(s):  
A. Musolff ◽  
J.H. Fleckenstein ◽  
M. Opitz ◽  
O. Büttner ◽  
R. Kumar ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Stream Water ◽  
Spatio Temporal

scholarly journals Spatial distribution of soils determines export of nitrogen and dissolved organic carbon from an intensively managed agricultural landscape

2012 ◽  
Vol 9 (11) ◽  
pp. 4513-4525 ◽  
Author(s):  
T. Wohlfart ◽  
J.-F. Exbrayat ◽  
K. Schelde ◽  
B. Christen ◽  
T. Dalgaard ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Agricultural Landscape ◽  
Agricultural Land ◽  
Stream Water ◽  
Organic Soils ◽  
Total N ◽  
Small Catchment ◽  
Landscape Characteristics ◽  
Intensively Managed

Abstract. The surrounding landscape of a stream has crucial impacts on the aquatic environment. This study pictures the hydro-biogeochemical situation of the Tyrebækken creek catchment in central Jutland, Denmark. The intensively managed agricultural landscape is dominated by rotational croplands. The small catchment mainly consist of sandy soil types besides organic soils along the streams. The aim of the study was to characterise the relative influence of soil type and land use on stream water quality. Nine snapshot sampling campaigns were undertaken during the growing season of 2009. Total dissolved nitrogen (TDN), nitrate (NO3−), ammonium nitrogen and dissolved organic carbon (DOC) concentrations were measured, and dissolved organic nitrogen (DON) was calculated for each grabbed sample. Electrical conductivity, pH and flow velocity were measured during sampling. Statistical analyses showed significant differences between the northern, southern and converged stream parts, especially for NO3− concentrations with average values between 1.4 mg N l−1 and 9.6 mg N l−1. Furthermore, throughout the sampling period DON concentrations increased to 2.8 mg N l−1 in the northern stream contributing up to 81% to TDN. Multiple-linear regression analyses performed between chemical data and landscape characteristics showed a significant negative influence of organic soils on instream N concentrations and corresponding losses in spite of their overall minor share of the agricultural land (12.9%). On the other hand, organic soil frequency was positively correlated to the corresponding DOC concentrations. Croplands also had a significant influence but with weaker correlations. For our case study we conclude that the fractions of coarse textured and organic soils have a major influence on N and DOC export in this intensively used landscape. Meanwhile, the contribution of DON to the total N losses was substantial.

scholarly journals Small-scale topography explains patterns and dynamics of dissolved organic carbon exports from the riparian zone of a temperate, forested catchment

2021 ◽  
Vol 25 (12) ◽  
pp. 6067-6086
Author(s):  
Benedikt J. Werner ◽  
Oliver J. Lechtenfeld ◽  
Andreas Musolff ◽  
Gerrit H. de Rooij ◽  
Jie Yang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Surface Runoff ◽  
Stream Water ◽  
Surface Flow ◽  
Small Scale ◽  
Topographic Wetness Index ◽  
Forested Catchment ◽  
Source Zones ◽  
Doc Export

Abstract. Export of dissolved organic carbon (DOC) from riparian zones (RZs) is an important component of temperate catchment carbon budgets, but export mechanisms are still poorly understood. Here we show that DOC export is predominantly controlled by the microtopography of the RZ (lateral variability) and by riparian groundwater level dynamics (temporal variability). From February 2017 until July 2019 we studied topography, DOC quality and water fluxes and pathways in the RZ of a small forested catchment and the receiving stream in central Germany. The chemical classification of the riparian groundwater and surface water samples (n=66) by Fourier transform ion cyclotron resonance mass spectrometry revealed a cluster of plant-derived, aromatic and oxygen-rich DOC with high concentrations (DOCI) and a cluster of microbially processed, saturated and heteroatom-enriched DOC with lower concentrations (DOCII). The two DOC clusters were connected to locations with distinctly different values of the high-resolution topographic wetness index (TWIHR; at 1 m resolution) within the study area. Numerical water flow modeling using the integrated surface–subsurface model HydroGeoSphere revealed that surface runoff from high-TWIHR zones associated with the DOCI cluster (DOCI source zones) dominated overall discharge generation and therefore DOC export. Although corresponding to only 15 % of the area in the studied RZ, the DOCI source zones contributed 1.5 times the DOC export of the remaining 85 % of the area associated with DOCII source zones. Accordingly, DOC quality in stream water sampled under five event flow conditions (n=73) was closely reflecting the DOCI quality. Our results suggest that DOC export by surface runoff along dynamically evolving surface flow networks can play a dominant role for DOC exports from RZs with overall low topographic relief and should consequently be considered in catchment-scale DOC export models. We propose that proxies of spatial heterogeneity such as the TWIHR can help to delineate the most active source zones and provide a mechanistic basis for improved model conceptualization of DOC exports.

scholarly journals Temperature controls production but hydrology regulates export of dissolved organic carbon at the catchment scale

2020 ◽  
Vol 24 (2) ◽  
pp. 945-966 ◽  
Author(s):  
Hang Wen ◽  
Julia Perdrial ◽  
Benjamin W. Abbott ◽  
Susana Bernal ◽  
Rémi Dupas ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Groundwater Flow ◽  
Soil Water ◽  
Reactive Transport ◽  
Stream Water ◽  
Catchment Scale ◽  
High Discharge ◽  
Doc Production ◽  
Doc Concentration

Abstract. Lateral carbon flux through river networks is an important and poorly understood component of the global carbon budget. This work investigates how temperature and hydrology control the production and export of dissolved organic carbon (DOC) in the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania, USA. Using field measurements of daily stream discharge, evapotranspiration, and stream DOC concentration, we calibrated the catchment-scale biogeochemical reactive transport model BioRT-Flux-PIHM (Biogeochemical Reactive Transport–Flux–Penn State Integrated Hydrologic Model, BFP), which met the satisfactory standard of a Nash–Sutcliffe efficiency (NSE) value greater than 0.5. We used the calibrated model to estimate and compare the daily DOC production rates (Rp; the sum of the local DOC production rates in individual grid cells) and export rate (Re; the product of the concentration and discharge at the stream outlet, or load). Results showed that daily Rp varied by less than an order of magnitude, primarily depending on seasonal temperature. In contrast, daily Re varied by more than 3 orders of magnitude and was strongly associated with variation in discharge and hydrological connectivity. In summer, high temperature and evapotranspiration dried and disconnected hillslopes from the stream, driving Rp to its maximum but Re to its minimum. During this period, the stream only exported DOC from the organic-poor groundwater and from organic-rich soil water in the swales bordering the stream. The DOC produced accumulated in hillslopes and was later flushed out during the wet and cold period (winter and spring) when Re peaked as the stream reconnected with uphill and Rp reached its minimum. The model reproduced the observed concentration–discharge (C–Q) relationship characterized by an unusual flushing–dilution pattern with maximum concentrations at intermediate discharge, indicating three end-members of source waters. A sensitivity analysis indicated that this nonlinearity was caused by shifts in the relative contribution of different source waters to the stream under different flow conditions. At low discharge, stream water reflected the chemistry of organic-poor groundwater; at intermediate discharge, stream water was dominated by the organic-rich soil water from swales; at high discharge, the stream reflected uphill soil water with an intermediate DOC concentration. This pattern persisted regardless of the DOC production rate as long as the contribution of deeper groundwater flow remained low (<18 % of the streamflow). When groundwater flow increased above 18 %, comparable amounts of groundwater and swale soil water mixed in the stream and masked the high DOC concentration from swales. In that case, the C–Q patterns switched to a flushing-only pattern with increasing DOC concentration at high discharge. These results depict a conceptual model that the catchment serves as a producer and storage reservoir for DOC under hot and dry conditions and transitions into a DOC exporter under wet and cold conditions. This study also illustrates how different controls on DOC production and export – temperature and hydrological flow paths, respectively – can create temporal asynchrony at the catchment scale. Future warming and increasing hydrological extremes could accentuate this asynchrony, with DOC production occurring primarily during dry periods and lateral export of DOC dominating in major storm events.

Influences of dissolved organic carbon on stream water chemistry in two forested catchments in central Sweden

2010 ◽  
Vol 101 (1-3) ◽  
pp. 229-241 ◽  
Author(s):  
Sara H. Norström ◽  
Jenny L. K. Vestin ◽  
Dan Bylund ◽  
Ulla S. Lundström
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Chemistry ◽  
Stream Water ◽  
Forested Catchments ◽  
Stream Water Chemistry

scholarly journals Temporal changes in photoreactivity of dissolved organic carbon and implications for aquatic carbon fluxes from peatlands

2017 ◽  
Vol 14 (7) ◽  
pp. 1793-1809 ◽  
Author(s):  
Amy E. Pickard ◽  
Kate V. Heal ◽  
Andrew R. McLeod ◽  
Kerry J. Dinsmore
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Samples ◽  
Stream Water ◽  
Direct Conversion ◽  
Aquatic Systems ◽  
Residence Times ◽  
Terrestrial Environment ◽  
Rainfall Events ◽  
Fluorescence Characteristics

Abstract. Aquatic systems draining peatland catchments receive a high loading of dissolved organic carbon (DOC) from the surrounding terrestrial environment. Whilst photo-processing is known to be an important process in the transformation of aquatic DOC, the drivers of temporal variability in this pathway are less well understood. In this study, 8 h laboratory irradiation experiments were conducted on water samples collected from two contrasting peatland aquatic systems in Scotland: a peatland stream and a reservoir in a catchment with high percentage peat cover. Samples were collected monthly at both sites from May 2014 to May 2015 and from the stream system during two rainfall events. DOC concentrations, absorbance properties and fluorescence characteristics were measured to investigate characteristics of the photochemically labile fraction of DOC. CO2 and CO produced by irradiation were also measured to determine gaseous photoproduction and intrinsic sample photoreactivity. Significant variation was seen in the photoreactivity of DOC between the two systems, with total irradiation-induced changes typically 2 orders of magnitude greater at the high-DOC stream site. This is attributed to longer water residence times in the reservoir rendering a higher proportion of the DOC recalcitrant to photo-processing. During the experimental irradiation, 7 % of DOC in the stream water samples was photochemically reactive and direct conversion to CO2 accounted for 46 % of the measured DOC loss. Rainfall events were identified as important in replenishing photoreactive material in the stream, with lignin phenol data indicating mobilisation of fresh DOC derived from woody vegetation in the upper catchment. This study shows that peatland catchments produce significant volumes of aromatic DOC and that photoreactivity of this DOC is greatest in headwater streams; however, an improved understanding of water residence times and DOC input–output along the source to sea aquatic pathway is required to determine the fate of peatland carbon.

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