scholarly journals Dissolved Organic Carbon Driven by Rainfall Events from a Semi-arid Catchment during Concentrated Rainfall Season in the Loess Plateau, China

2019 ◽  
Author(s):  
Linhua Wang ◽  
Haw Yen ◽  
Xinhui E ◽  
Liding Chen ◽  
Yafeng Wang
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
The Loess Plateau ◽  
Rainfall Season ◽  
Doc Export ◽  
Doc Concentration ◽  
Doc Flux ◽  
Event Based ◽  
Runoff Discharge ◽  
Semi Arid

Abstract. Dissolved organic carbon (DOC) transported by surface runoff has been identified as an important role of the global carbon cycle. Despite there being many studies on DOC concentration and flux, but little information is available in semi-arid catchments of the Loess Plateau Region (LPR). The primary goal of this study was to quantify DOC exported from a sequence of runoff events during the concentrated rainfall season. In addition, factors that affect DOC export from a small headwater catchment will be investigated accordingly. Runoff discharge and DOC concentration were monitored at the outlet of the Yangjuangou catchment in Yanan, Shaanxi Province, China. The results showed that DOC concentration was highly variable (1.91–34.70 mg L−1), with event-based DOC concentrations ranging from 4.08 to 15.66 mg L−1. The mean monthly DOC flux loading from the catchment was 94.73–110.17 kg km−2 from June to September, while the event-based DOC flux ranged from 0.08 to 2.81 kg km−2. Intra-events of rainfall amount and runoff discharge led to event-based/monthly differences in DOC concentration and flux. Hysteresis analysis showed a nonlinear relationship between DOC concentration and discharge in the runoff process. Our results highlighted the advantages of high-frequency monitoring for DOC export and indicated that DOC export from a catchment is largely influenced by the interaction of rainfall and antecedent conditions for a rainfall event. Engineering and scientists can take advantage of the derived results to better develop advanced field monitoring work. In addition, release of DOC runoff can take quantified during hydrological and biogeochemical processes within catchments in LPR.

scholarly journals Dissolved organic carbon driven by rainfall events from a semi-arid catchment during concentrated rainfall season in the Loess Plateau, China

2019 ◽  
Vol 23 (7) ◽  
pp. 3141-3153 ◽  
Author(s):  
Linhua Wang ◽  
Haw Yen ◽  
Xinhui E ◽  
Liding Chen ◽  
Yafeng Wang
Keyword(s):  
Organic Carbon ◽  
The Loess Plateau ◽  
Rainfall Events ◽  
Rainfall Season ◽  
Doc Export ◽  
Doc Concentration ◽  
Doc Flux ◽  
Event Based ◽  
Runoff Discharge ◽  
Semi Arid

Abstract. Dissolved organic carbon (DOC) transported by runoff has been identified as an important role in the global carbon cycle. Despite there being many studies on DOC concentration and flux, little information is available for the semi-arid catchments of the Loess Plateau region (LPR). The primary goal of this study was to quantify DOC exported and driven by a sequence of rainfall events during the concentrated rainfall season. In addition, factors that affect DOC export from a small headwater catchment will be investigated accordingly. Runoff discharge and DOC concentration were monitored at the outlet of the Yangjuangou catchment in Yanan, Shaanxi Province, China. The results showed that DOC concentration was highly variable, with event-based DOC concentrations ranging from 5.14 to 13.14 mg L−1. Hysteresis analysis showed a nonlinear relationship between DOC concentration and flow rate in the hydrological process. The monthly DOC flux loading from the catchment was varied from 94.73 to 110.17 kg km−2, while the event-based DOC flux ranged from 0.18 to 2.84 kg km−2 in the period of June to September. Variations of event-driven DOC concentration contributed slightly to a difference in DOC flux, whereas intra-events of rainfall amount and runoff discharge led to evident differences in DOC export. In conclusion, our case results highlighted the advantages of high-frequency monitoring for DOC export and indicated that event-driven DOC export is largely influenced by the interaction of catchment hydrology and antecedent condition within a catchment. Engineers and scientists can take advantage of the derived results to better develop advanced field monitoring work. In addition, more studies are needed to investigate the magnitude of terrestrial DOC export in response to projected climate change at larger spatio-temporal scales, which may have implications for the carbon balance and carbon cycle model from an ecologically restored catchment in the LPR.

scholarly journals Dissolved organic carbon concentrations vary with season and land use – investigations from two fens in Northeastern Germany over two years

2014 ◽  
Vol 11 (5) ◽  
pp. 7079-7111 ◽  
Author(s):  
M. Schwalm ◽  
J. Zeitz
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Environmental Concern ◽  
Doc Export ◽  
Doc Concentration ◽  
Agricultural Use ◽  
Northeastern Germany ◽  
Carbon Concentrations ◽  
Discharge Measurements

Abstract. The rising export of dissolved organic carbon (DOC) from peatlands during the last 20 years is of great environmental concern, as DOC harms drinking water quality and diminishes the carbon storage of peatlands. Lack of knowledge particularly exists for fens. The aim of our study was to determine DOC concentrations at an agriculturally used fen and a rewetted fen throughout the year. We measured DOC concentrations in ditch water of these fens in 2011 and 2012. Furthermore, discharge measurements were condcucted to detect DOC export. Overall DOC concentrations at our agriculturally used site and at our rewetted site were 35 mg L−1 and 26 mg L−1 (median), respectively. The maximum DOC concentration at our agriculturally used site was twice as high as at the rewetted site (134 mg L−1 vs. 61 mg L−1). Annual DOC export was calculated for the rewetted site, amounting to 200 kg C ha−1 on average. Our results suggest that rewetting of degraded fens reduces DOC export in the long-term, while agricultural use of fens leads to enhanced decomposition and thus, elevates DOC export.

scholarly journals Retrogressive thaw slumps temper dissolved organic carbon delivery to streams of the Peel Plateau, NWT, Canada

2017 ◽  
Author(s):  
Cara A. Bulger ◽  
Suzanne E. Tank ◽  
Steven V. Kokelj
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Climate History ◽  
Fine Grained ◽  
Temperature And Precipitation ◽  
Environmental Controls ◽  
Doc Concentration ◽  
Using Data ◽  
Doc Flux ◽  
Peel Plateau

Abstract. In Siberia and Alaska, permafrost thaw has been associated with significant increases in the delivery of dissolved organic carbon (DOC) to recipient stream ecosystems. Here, we examine the effect of retrogressive thaw slumps (RTS) on DOC concentration and transport, using data from eight RTS features on the Peel Plateau, NT, Canada. Like extensive regions of northwestern Canada, the Peel Plateau is comprised of thick, ice-rich tills that were deposited at the margins of the continental ice sheet. RTS features are now widespread in this region, with headwall exposures up to 30 m high, and total disturbed areas often exceeding 30 ha. We find that intensive slumping on the Peel Plateau is universally associated with decreasing DOC concentrations downstream of slumps, even though the composition of slump-derived dissolved organic matter (DOM; assessed using specific UV absorbance and slope ratios) is similar to permafrost-derived DOM from other regions. Comparisons of upstream and downstream DOC flux relative to a conservative tracer suggest that the substantial fine-grained sediments released by slumping may sequester DOC on this landscape. Runoff obtained directly from within slump features, above entry into recipient streams, indicates that the deepest RTS features, which thaw the greatest extent of buried, Pleistocene-aged glacial tills, have the lowest runoff DOC concentrations when compared to upstream, un-disturbed locations. In contrast, shallower features, with exposures that are more limited to a relict Holocene active layer, have within-slump DOC concentrations more similar to upstream sites. Finally, fine-scale work at a single RTS feature indicates that temperature and precipitation serve as primary environmental controls on above-slump and below-slump DOC flux, but that the relationship between climatic parameters and DOC flux is complex for these dynamic thermokarst features. These results demonstrate that we should expect striking variation in thermokarst-associated DOC mobilization across Arctic regions, but that within-region variation in thermokarst intensity and other landscape factors are also important for determining biogeochemical response. An understanding of landscape and climate history, permafrost genesis, soil composition, the nature and intensity of thermokarst, and the interaction of these factors, is critical for predicting changes in land-to-water carbon mobilization in a warming circumpolar world.

scholarly journals The dynamics and export of dissolved organic carbon from subtropical small mountainous rivers during typhoon and non-typhoon periods

2017 ◽  
Author(s):  
Tsung-Yu Lee ◽  
Li-Chin Lee ◽  
Jr-Chuan Huang ◽  
Shih-Hao Jien ◽  
Thomas Hein ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Discharge ◽  
Dilution Effect ◽  
Carbon Export ◽  
Doc Concentration ◽  
The Mean ◽  
Doc Flux ◽  
Small Mountainous Rivers

Abstract. Small mountainous rivers (SMRs) are important conveyors of the land-to-ocean organic carbon export. However, relatively few studies have focused on dissolved organic carbon (DOC) compared to particulate organic carbon. In a long-term project (2002 to 2014), stream DOC was monitored in three neighboring subtropical small mountainous rivers of Taiwan. The objective was to relate DOC concentrations to water discharge and to quantify DOC flux during typhoon and non-typhoon periods. Seasonal fluctuations of DOC concentrations were closely correlated with air temperature at all sampling stations. During non-typhoon periods, increasing water discharge led to decreasing DOC concentrations due to a dilution effect. However, during typhoon periods, DOC concentrations increased with some lead time along the hydrograph and reached the annual maximum which likely sources from a significant input of litter and upper soil layers. The mean DOC concentration of the studied systems (

scholarly journals Distribution and cycling of terrigenous dissolved organic carbon in peatland-draining rivers and coastal waters of Sarawak, Borneo

2018 ◽  
Author(s):  
Patrick Martin ◽  
Nagur Cherukuru ◽  
Ashleen S. Y. Tan ◽  
Nivedita Sanwlani ◽  
Aazani Mujahid ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Coastal Waters ◽  
Photo Degradation ◽  
North East ◽  
Global Land ◽  
Doc Concentration ◽  
Blackwater Rivers ◽  
Doc Flux ◽  
North Western

Abstract. South-East Asia is home to one of the world's largest stores of tropical peatland, and accounts for roughly 10 % of the global land-to-sea dissolved organic carbon (DOC) flux. We present the first-ever seasonally-resolved measurements of DOC concentration and chromophoric dissolved organic matter (CDOM) spectra for six peatland-draining rivers and coastal waters in Sarawak, north-western Borneo. The rivers differed substantially in DOC concentration, ranging from 120–250 µmol L−1 (Rajang river) to 3,100–4,400 µmol L−1 (Maludam river). All rivers carried high CDOM concentrations, with a350 in the four blackwater rivers between 70–210 m−1, and 4–12 m−1 in the other two rivers. DOC and CDOM showed conservative mixing with seawater except in the largest river (the Rajang), where DOC concentrations in the estuary were elevated, most likely due to inputs from the extensive peatlands within the Rajang delta. Seasonal variation was moderate and inconsistent between rivers. However, during the rainier north-east monsoon, all marine stations in the western part of our study area had higher DOC concentrations and lower CDOM spectral slopes, indicating a greater proportion of terrigenous DOM in coastal waters. Photo-degradation experiments revealed that riverine DOC and CDOM in Sarawak are photo-labile: up to 25 % of riverine DOC was lost within five days of exposure to natural sunlight, and the spectral slopes of photo-bleached CDOM resembled those of our marine samples. We conclude that coastal waters of Sarawak receive large inputs of terrigenous DOC that is only minimally altered during estuarine transport, and that any biogeochemical processing must therefore occur mostly at sea. It is likely that photo-degradation plays an important role in the degradation of terrigenous DOC in these waters.

Can tributary in-flows improve the recovery of the dissolved organic carbon regime in a snowmelt river regulated by a large reservoir?

2016 ◽  
Vol 67 (9) ◽  
pp. 1338 ◽  
Author(s):  
Ann-Marie Rohlfs ◽  
Simon M. Mitrovic ◽  
Simon Williams ◽  
Daniel Coleman
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River System ◽  
Main Stem ◽  
Water Diversion ◽  
Regulated River ◽  
Regulated Rivers ◽  
Large Reservoir ◽  
Doc Export ◽  
Doc Concentration

Although tributary inputs can accelerate the recovery of many physical and chemical gradients below large reservoirs, their contribution to the dissolved organic carbon (DOC) regime in regulated rivers remains poorly studied. In some regulated tributaries, flow volumes can be manipulated, potentially influencing DOC supply to the main stem. The present study examines how tributary water diversion affects DOC supply to a snowmelt river regulated by large reservoirs. DOC concentration was measured at tributary and main stem sites, and tributary DOC export was estimated under different tributary flow-diversion scenarios. Significant, positive correlations between DOC concentration and discharge were absent directly below the dam, but were present in the unregulated tributary, and re-emerged below the tributary confluence. Irrespective of water-diversion practices, tributary in-flows reconnected the regulated main stem to a more variable DOC regime driven by catchment flushing processes. However, tributary water diversion dampened the tributary signal by reducing DOC pulse frequency and total DOC export to the regulated river. These aspects of the DOC regime may influence basal resource availability and ecosystem functioning in the regulated main stem. The present study illustrates how an ecologically valuable tributary function can be addressed and quantified to guide the management and rehabilitation of a regulated river system.

scholarly journals Distribution and cycling of terrigenous dissolved organic carbon in peatland-draining rivers and coastal waters of Sarawak, Borneo

2018 ◽  
Vol 15 (22) ◽  
pp. 6847-6865 ◽  
Author(s):  
Patrick Martin ◽  
Nagur Cherukuru ◽  
Ashleen S. Y. Tan ◽  
Nivedita Sanwlani ◽  
Aazani Mujahid ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Coastal Waters ◽  
Chromophoric Dissolved Organic Matter ◽  
North East ◽  
Global Land ◽  
Doc Concentration ◽  
Blackwater Rivers ◽  
Doc Flux ◽  
North Western

Abstract. South-East Asia is home to one of the world's largest stores of tropical peatland and accounts for roughly 10 % of the global land-to-sea dissolved organic carbon (DOC) flux. We present the first ever seasonally resolved measurements of DOC concentration and chromophoric dissolved organic matter (CDOM) spectra for six peatland-draining rivers and coastal waters in Sarawak, north-western Borneo. The rivers differed substantially in DOC concentration, ranging from 120–250 µmol L−1 (Rajang River) to 3100–4400 µmol L−1 (Maludam River). All rivers carried high CDOM concentrations, with a350 in the four blackwater rivers between 70 and 210 m−1 and 4 and 12 m−1 in the other two rivers. DOC and CDOM showed conservative mixing with seawater except in the largest river (the Rajang), where DOC concentrations in the estuary were elevated, most likely due to inputs from the extensive peatlands within the Rajang Delta. Seasonal variation was moderate and inconsistent between rivers. However, during the rainier north-east monsoon, all marine stations in the western part of our study area had higher DOC concentrations and lower CDOM spectral slopes, indicating a greater proportion of terrigenous DOM in coastal waters. Photodegradation experiments revealed that riverine DOC and CDOM in Sarawak are photolabile: up to 25 % of riverine DOC was lost within 5 days of exposure to natural sunlight, and the spectral slopes of photo-bleached CDOM resembled those of our marine samples. We conclude that coastal waters of Sarawak receive large inputs of terrigenous DOC that is only minimally altered during estuarine transport and that any biogeochemical processing must therefore occur mostly at sea. It is likely that photodegradation plays an important role in the degradation of terrigenous DOC in these waters.

scholarly journals Characteristics of wet dissolved carbon deposition in a semi-arid catchment at the Loess Plateau, China

2018 ◽  
Vol 15 (11) ◽  
pp. 3345-3356
Author(s):  
Linhua Wang ◽  
Haw Yen ◽  
Liding Chen ◽  
Xinhui E ◽  
Yafeng Wang
Keyword(s):  
Loess Plateau ◽  
Carbon Deposition ◽  
Terrestrial Ecosystems ◽  
External Input ◽  
The Loess Plateau ◽  
Dissolved Carbon ◽  
Rainfall Season ◽  
Event Based ◽  
Global Carbon ◽  
Semi Arid

Abstract. Wet dissolved carbon deposition is a critical node of the global carbon cycle, but little is known about dissolved organic and inorganic carbon (DOC and DIC) concentrations and fluxes in the semi-arid areas of the Loess Plateau Region (LPR). In this study, we measured variations in DOC and DIC concentrations in rainfalls at Yangjuangou Ecological Restoration and Soil and Water Observatory. Rainwater samples were collected in 16 rainfall events from July to September and the event-based, monthly concentrations and fluxes of DOC and DIC were quantified. The results showed that the event-based concentrations and fluxes of DOC and DIC were highly variable, ranging from 0.56 to 28.71 mg C L−1 and from 3.47 to 17.49 mg C L−1, respectively. The corresponding event-based fluxes ranged from 0.21–258.36 mg C m−2 and from 4.12 to 42.32 mg C m−2. The monthly concentrations of DOC and DIC were 24.62 and 4.30 (July), 3.58 and 10.52 (August), and 1.01 and 5.89 (September) mg C L−1, respectively. Thus, the monthly deposition fluxes of DOC and DIC were 541.64/94.60, 131.03/385.03, and 44.44/259.16 mg C m−2 for July, August, and September, respectively. In addition, the concentrations of DOC and DIC for the concentrated rainfall season (July–September) in the studied catchment were 7.06 and 7.00 mg C L−1, respectively. The estimated annual wet dissolved carbon depositions were 1.91 and 1.89 g C m−2 yr−1 for DOC and DIC, respectively. The results of this study suggest the variation in concentrations and fluxes of DOC and DIC and explore that these variation may be related to the dissolved carbon source and the rainfall characteristics during the concentrated rainfall season in the semi-arid catchment of the LPR. Furthermore, these results also suggest that dissolved carbon may be an important external input of carbon into terrestrial ecosystems.

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