scholarly journals Potential for long‐term transfer of dissolved organic carbon from riparian zones to streams in boreal catchments

2015 ◽  
Vol 21 (8) ◽  
pp. 2963-2979 ◽  
Author(s):  
José L. J. Ledesma ◽  
Thomas Grabs ◽  
Kevin H. Bishop ◽  
Sherry L. Schiff ◽  
Stephan J. Köhler
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Riparian Zones

scholarly journals Effect of Acidified Versus Frozen Storage on Marine Dissolved Organic Carbon Concentration and Isotopic Composition

Radiocarbon ◽  
2016 ◽  
Vol 59 (3) ◽  
pp. 843-857 ◽  
Author(s):  
Brett D Walker ◽  
Sheila Griffin ◽  
Ellen R M Druffel
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Standard Procedure ◽  
Frozen Storage ◽  
Open Ocean ◽  
Field Collection ◽  
Organic Carbon Concentration ◽  
Large Numbers ◽  
Logistical Problem

AbstractThe standard procedure for storing/preserving seawater dissolved organic carbon (DOC) samples after field collection is by freezing (–20°C) until future analysis can be made. However, shipping and receiving large numbers of these samples without thawing presents a significant logistical problem and large monetary expense. Access to freezers can also be limited in remote field locations. We therefore test an alternative method of preserving and storing samples for the measurement of DOC concentrations ([DOC]), stable carbon (δ13C), and radiocarbon (as ∆14C) isotopic values via UV photooxidation (UVox). We report a total analytical reproducibility of frozen DOC samples to be [DOC]±1.3 µM, ∆14C±9.4‰, and δ13C±0.1‰, comparable to previously reported results (Druffel et al. 2013). Open Ocean DOC frozen versus acidified duplicates were on average offset by ∆DOC±1.1 µM, ∆∆14C± –1.3‰, and ∆δ13C± –0.1‰. Coastal Ocean frozen vs. acidified sample replicates, collected as part of a long-term (380-day) storage experiment, had larger, albeit consistent offsets of ∆DOC±2.2 µM, ∆∆14C±1.5‰, and ∆δ13C± –0.2‰. A simple isotopic mass balance of changes in [DOC], ∆14C, and δ13C values reveals loss of semi-labile DOC (2.2±0.6 µM, ∆14C=–94±105‰, δ13C=–27±10‰; n=4) and semi-recalcitrant DOC (2.4±0.7 µM, ∆14C=–478±116‰, δ13C=–23.4±3.0‰; n=3) in Coastal and Open Ocean acidified samples, respectively.

scholarly journals High-frequency measurements explain quantity and quality of dissolved organic carbon mobilization in a headwater catchment

2019 ◽  
Vol 16 (22) ◽  
pp. 4497-4516 ◽  
Author(s):  
Benedikt J. Werner ◽  
Andreas Musolff ◽  
Oliver J. Lechtenfeld ◽  
Gerrit H. de Rooij ◽  
Marieke R. Oosterwoud ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
High Frequency ◽  
Riparian Zone ◽  
Quality Parameters ◽  
Riparian Zones ◽  
Frequency Measurements ◽  
Seasonal Scale ◽  
Headwater Catchment

Abstract. Increasing dissolved organic carbon (DOC) concentrations and exports from headwater catchments impact the quality of downstream waters and pose challenges to water supply. The importance of riparian zones for DOC export from catchments in humid, temperate climates has generally been acknowledged, but the hydrological controls and biogeochemical factors that govern mobilization of DOC from riparian zones remain elusive. A high-frequency dataset (15 min resolution for over 1 year) from a headwater catchment in the Harz Mountains (Germany) was analyzed for dominant patterns in DOC concentration (CDOC) and optical DOC quality parameters SUVA254 and S275−295 (spectral slope between 275 and 295 nm) on event and seasonal scales. Quality parameters and CDOC systematically changed with increasing fractions of high-frequency quick flow (Qhf) and antecedent hydroclimatic conditions, defined by the following metrics: aridity index (AI60) of the preceding 60 d and the quotient of mean temperature (T30) and mean discharge (Q30) of the preceding 30 d, which we refer to as discharge-normalized temperature (DNT30). Selected statistical multiple linear regression models for the complete time series (R2=0.72, 0.64 and 0.65 for CDOC, SUVA254 and S275−295, resp.) captured DOC dynamics based on event (Qhf and baseflow) and seasonal-scale predictors (AI60, DNT30). The relative importance of seasonal-scale predictors allowed for the separation of three hydroclimatic states (warm and dry, cold and wet, and intermediate). The specific DOC quality for each state indicates a shift in the activated source zones and highlights the importance of antecedent conditions and their impact on DOC accumulation and mobilization in the riparian zone. The warm and dry state results in high DOC concentrations during events and low concentrations between events and thus can be seen as mobilization limited, whereas the cold and wet state results in low concentration between and during events due to limited DOC accumulation in the riparian zone. The study demonstrates the considerable value of continuous high-frequency measurements of DOC quality and quantity and its (hydroclimatic) key controlling variables in quantitatively unraveling DOC mobilization in the riparian zone. These variables can be linked to DOC source activation by discharge events and the more seasonal control of DOC production in riparian soils.

scholarly journals Dissolved organic carbon and dissolved nitrogen in soil under different fertilization treatments

2011 ◽  
Vol 52 (No. 2) ◽  
pp. 55-63 ◽  
Author(s):  
S.S. Gonet ◽  
B. Debska
Keyword(s):  
Surface Layer ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Cattle Slurry ◽  
Soil Horizons ◽  
Mineral Fertilization ◽  
Labile Organic Matter ◽  
Dissolved Nitrogen ◽  
After Effect

The objective of the study was to evaluate the effects of long-term fertilization of a sandy soil with differentiated doses of cattle slurry as well as its after-effect action on the possibilities of migration of dissolved organic carbon (DOC) and dissolved nitrogen (DNt) down to deeper layers of the soil profile. DOC and DNt were extracted with borate buffer and 0.004M CaCl<sub>2</sub> solution. Evaluation of effects of cattle slurry on the content of DOC and DNt was done in comparison with mineral fertilization. It was shown that the use of cattle slurry in the doses of 100 and 200&nbsp;m<sup>3</sup>/ha caused a significant increase of labile organic matter in the 0&ndash;25 and 25&ndash;50 cm layers of soil. As compared with mineral fertilization the application of slurry increased also the amounts of extracted DNt, but only in the surface layer. The DNt content in the deeper soil horizons did not depend on the kind of fertilization. Concentrations of DOC and DNt in the extracts depended not only on their content in soil but it was also modified substantially by the extractant used.

Long-term patterns of dissolved organic carbon in lakes across eastern Canada: Evidence of a pronounced climate effect

2009 ◽  
Vol 55 (1) ◽  
pp. 30-42 ◽  
Author(s):  
Jan Zhang ◽  
Jeff Hudson ◽  
Richard Neal ◽  
Jeff Sereda ◽  
Thomas Clair ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Eastern Canada ◽  
Climate Effect

scholarly journals Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments

2012 ◽  
Vol 9 (1) ◽  
pp. 209-251 ◽  
Author(s):  
M. I. Stutter ◽  
S. M. Dunn ◽  
D. G. Lumsdon
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Soil Conditions ◽  
Dry Period ◽  
Flow Paths ◽  
Selective Filtration ◽  
Antecedent Conditions ◽  
Doc Concentration ◽  
Mineral Soils

Abstract. Better knowledge of spatial and temporal delivery of dissolved organic Carbon (DOC) in small catchments is required to understand the mechanisms behind reported long-term changes in C fluxes from some peatlands. We monitored two storms with contrasting seasons and antecedent conditions in a small upland UK moorland catchment. We examined DOC concentrations and specific UV absorbance (SUVA at 285 nm), together with solute concentrations required to undertake end member mixing analyses to define dominant flow paths contributing to streamflow. This was combined with laboratory soil-solution equilibrations. We aimed to resolve how seasonal biogeochemical processing of DOC and flowpath changes in organo-mineral soils combine to affect DOC exported via the stream. An August storm following a dry period gave maximum DOC concentration of 10 mg l−1. Small DOC:DON ratios (16–28) and SUVA (2.7–3.6 l mg−1 m−1) was attributed to filtration of aromatic compounds associated with up to 53% B horizon flow contributions. This selective filtration of high SUVA DOC was reproduced in the experimental batch equilibration system. For a November storm, wetter antecedent soil conditions led to enhanced soil connectivity with the stream and seven times greater DOC stream-load (maximum concentration 16 mg l−1). This storm had a 63% O horizon flow contribution at its peak, limited B horizon buffering and consequently more aromatic DOC (SUVA 3.9–4.5 l mg−1 m−1 and DOC:DON ratio 35–43). We suggest that simple mixing of waters from different flow paths cannot alone explain the differences in DOC compositions between August and November and biogeochemical processing of DOC is required to fully explain the observed stream DOC dynamics. This is in contrast to other studies proposing hydrological controls and provides evidence that DOC biogeochemistry must be incorporated in modelling to predict the impacts of changes in DOC delivery to aquatic systems.

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