Optical in-situ sensors capture dissolved organic carbon (DOC) dynamics after prescribed fire in high-DOC forest watersheds

2019 ◽  
Vol 28 (10) ◽  
pp. 761 ◽  
Author(s):  
Christopher I. Olivares ◽  
Wenbo Zhang ◽  
Habibullah Uzun ◽  
Cagri Utku Erdem ◽  
Hamed Majidzadeh ◽  
...  
Keyword(s):  
South Carolina ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Optical Sensors ◽  
Prescribed Fire ◽  
Second Order ◽  
In Situ Sensors ◽  
Forest Watersheds ◽  
Doc Load

Fires alter terrestrial dissolved organic carbon (DOC) exports into water, making reliable post-fire DOC monitoring a crucial aspect of safeguarding drinking water supply. We evaluated DOC optical sensors in a pair of prescribed burned and unburned first-order watersheds at the Santee Experimental Forest, in the coastal plain forests of South Carolina, and the receiving second-order watershed during four post-fire storm DOC pulses. Median DOC concentrations were 30 and 23mgL−1 in the burned and unburned watersheds following the first post-fire storm. Median DOC remained high during the second and third storms, but returned to pre-fire concentrations in the fourth storm. During the first three post-fire storms, sensor DOC load in the burned watershed was 1.22-fold higher than in the unburned watershed. Grab samples underestimated DOC loads compared with those calculated using the in-situ sensors, especially for the second-order watershed. After fitting sensor values with a locally weighted smoothing model, the adjusted sensor values were within 2mgL−1 of the grab samples over the course of the study. Overall, we showed that prescribed fire can release DOC during the first few post-fire storms and that in-situ sensors have adequate sensitivity to capture storm-related DOC pulses in high-DOC forest watersheds.

Application of Dissolved Organic Carbon Runoff Model Considering Soil Infiltration and River Runoff Processes in Multiple Forested Watersheds

2021 ◽  
Author(s):  
Kazunori Ebata ◽  
Yutaka Ichikawa ◽  
Hiroshi Ishidaira ◽  
Yoshitaka Matsumoto ◽  
Kei Nishida
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Transport Processes ◽  
Subsurface Water ◽  
Short Time Scale ◽  
Seasonal Temperature ◽  
Soil System ◽  
System A ◽  
Monsoon Area ◽  
Doc Load

<p>Estimation of dissolved organic carbon (DOC) runoff load in forested watershed is important for the assessment of the global carbon cycle as well as for the control of regional water environments. A few process-based models have been proposed to estimate the DOC load to water environments, which assume DOC source in topsoil and transport processes to the river, however, these models exhibited difficulties with the availability of input data and applicability to short time-scale rainfall-runoff processes in the Asian monsoon area. This study presents a new process-based model that consists of two separate systems for determining DOC load enforced by DOC Source Area (DSA) concept. For the runoff system, a semi-distributed hydrological modelling unit (‘modified-TOPMODEL’) was installed, by which surface and subsurface water flows, representing for DSA, were sequentially simulated. For the soil system, a wet-dry cycle was successfully simulated by an advection-diffusion and dissolution formulation as well as seasonal temperature effect. The model is first evaluated upstream (98ha) and downstream (1798ha) in the Mizugaki Watershed, Yamanashi, Japan and then applied for a Miuchi (203ha) watershed, Aichi, Japan during 2014 to 2018. The results of cumulative DOC load at baseflow and stormflow periods that the model performed well between the simulations and observations for both study sites. Considering the stormflow periods, from 25.2% to 32.0%, and 31.1% of high flows contributed to 50% of the total DOC load at Mizugaki and Miuchi watershed, respectively. Overall, the proposed model successfully simulated DOC load under different geochemical and hydrological condition by capturing the DSA variability.</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.

In situ dissolved organic carbon (DOC) release by submerged macrophyte–epiphyte communities in southern Quebec lakes

2009 ◽  
Vol 66 (9) ◽  
pp. 1522-1531 ◽  
Author(s):  
M. Demarty ◽  
Y. T. Prairie
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Myriophyllum Spicatum ◽  
Dry Weight ◽  
Release Rates ◽  
Doc Production ◽  
Epiphyte Communities ◽  
Benthic Chambers ◽  
Freshwater Macrophyte

We studied the in situ release of dissolved organic carbon (DOC) by growing a submerged freshwater macrophyte–epiphyte complex. Incubations with benthic chambers in five southeastern Quebec lakes show a net DOC production for different communities of Myriophyllum spicatum and Potamogeton spp. Daytime DOC release rates range from undetectable to 9.7 mg C·m–2·h–1. Although DOC release was restricted to daylight hours and thus suggestive of a photosynthesis-related process, we found no strong link between DOC release rates and concurrent illumination or temperature. We found no difference in DOC release rates between the three main colonizing species of the studied region. The overall mean DOC release rate was 4.57 mg C·m–2·h–1 (standard deviation (SD), ±0.65) or 56 µg C·g dry weight–1·h–1 (SD, ±8), which we suggest can be used for extrapolations at the lake scale.

scholarly journals In-situ fluorescence spectroscopy indicates total bacterial abundance and dissolved organic carbon

2020 ◽  
Vol 738 ◽  
pp. 139419 ◽  
Author(s):  
James P.R. Sorensen ◽  
Mor Talla Diaw ◽  
Abdoulaye Pouye ◽  
Raphaëlle Roffo ◽  
Djim M.L. Diongue ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Fluorescence Spectroscopy ◽  
Dissolved Organic Carbon ◽  
Bacterial Abundance ◽  
Total Bacterial Abundance

Hurricanes accelerate dissolved organic carbon cycling in coastal ecosystems

2020 ◽  
Author(s):  
Ge Yan ◽  
Jessica Labonté ◽  
Antonietta Quigg ◽  
Karl Kaiser
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Flood Plain ◽  
Extreme Weather Events ◽  
Flood Events ◽  
Decay Constants ◽  
Continental Shelves ◽  
Weather Events ◽  
Organic Carbon Cycling

<p>Extreme weather events such as tropical storms and hurricanes deliver large amounts of<br>freshwater (stormwater and river discharge) and associated dissolved organic carbon (DOC)<br>to estuaries and the coastal ocean, affecting water quality and carbon budgets. Hurricane<br>Harvey produced an unprecedented 1000-year flood event in 2017 that inundated the heavily<br>urbanized and industrialized Houston/Galveston region (Texas, USA). Within a week, storm-<br>associated floodwater delivered 105±10 Gg of terrigenous dissolved organic carbon (tDOC)<br>to Galveston Bay and the Gulf of Mexico continental shelves. In-situ decay constants of<br>8.75-28.33 yr<sup> -1</sup> resulted in the biomineralization of ~70% of tDOC within one month of<br>discharge from the flood plain. The high removal efficiency of tDOC was linked to a diverse<br>microbial community capable of degrading a wide repertoire of dissolved organic matter<br>(DOM), and suggested hurricane-induced flood events affect net CO<sub>2</sub> exchange and nutrient<br>budgets in estuarine watersheds and coastal seas.<br><br></p>

scholarly journals Identification and analysis of low-molecular-weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography

2016 ◽  
Vol 13 (12) ◽  
pp. 3833-3846 ◽  
Author(s):  
Emily C. O'Donnell ◽  
Jemma L. Wadham ◽  
Grzegorz P. Lis ◽  
Martyn Tranter ◽  
Amy E. Pickard ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Microbial Activity ◽  
Free Amino ◽  
Low Molecular Weight ◽  
Subglacial Environment ◽  
Basal Ice ◽  
Order Of Magnitude

Abstract. Determining the concentration and composition of dissolved organic carbon (DOC) in glacial ecosystems is important for assessments of in situ microbial activity and contributions to wider biogeochemical cycles. Nonetheless, there is limited knowledge of the abundance and character of DOC in basal ice and the subglacial environment and a lack of quantitative data on low-molecular-weight (LMW) DOC components, which are believed to be highly bioavailable to microorganisms. We investigated the abundance and composition of DOC in basal ice via a molecular-level DOC analysis. Spectrofluorometry and a novel ion chromatographic method, which has been little utilized in glacial science for LMW-DOC determinations, were employed to identify and quantify the major LMW fractions (free amino acids, carbohydrates, and carboxylic acids) in basal ice from four glaciers, each with a different type of overridden material (i.e. the pre-entrainment sedimentary type such as lacustrine material or palaeosols). Basal ice from Joyce Glacier (Antarctica) was unique in that 98 % of the LMW-DOC was derived from the extremely diverse free amino acid (FAA) pool, comprising 14 FAAs. LMW-DOC concentrations in basal ice were dependent on the bioavailability of the overridden organic carbon (OC), which in turn was influenced by the type of overridden material. Mean LMW-DOC concentrations in basal ice from Russell Glacier (Greenland), Finsterwalderbreen (Svalbard), and Engabreen (Norway) were low (0–417 nM C), attributed to the relatively refractory nature of the OC in the overridden palaeosols and bedrock. In contrast, mean LMW-DOC concentrations were an order of magnitude higher (4430 nM C) in basal ice from Joyce Glacier, a reflection of the high bioavailability of the overridden lacustrine material (> 17 % of the sediment OC comprised extractable carbohydrates, a proxy for bioavailable OC). We find that the overridden material may act as a direct (via abiotic leaching) and indirect (via microbial cycling) source of DOC to the subglacial environment and provides a range of LMW-DOC compounds that may stimulate microbial activity in wet subglacial sediments.

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