scholarly journals New insights from the use of carbon isotopes as tracers of DOC sources and DOC transport processes in headwater catchments

2013 ◽  
Vol 10 (11) ◽  
pp. 17965-18007
Author(s):  
T. Lambert ◽  
A.-C. Pierson-Wickmann ◽  
G. Gruau ◽  
A. Jaffrezic ◽  
P. Petitjean ◽  
...  
Keyword(s):  
Transport Processes ◽  
High Flow ◽  
Published Data ◽  
Storm Events ◽  
Headwater Catchments ◽  
Relative Contribution ◽  
Doc Export ◽  
High Flow Period ◽  
Doc Flux ◽  
Hourly Basis

Abstract. Monitoring the isotopic composition (δ13CDOC) of dissolved organic carbon (DOC) during flood events can be helpful for locating DOC sources in catchments and quantifying their relative contribution to DOC stream flux. High-resolution (< hourly basis) δ13CDOC data were obtained on six successive storm events occurring during the high-flow period in a small headwater catchment from western France. Intra-storm δ13CDOCvalues exhibit a marked temporal variability, with some storms showing large variations (>2‰), and others yielding a very restricted range of values (<1‰). Comparison of these results with previously published data shows that the range of intra-storm δ13CDOC values closely reflects the temporal and spatial variation in δ13CDOC observed in the riparian soils of this catchment during the same period. Using δ13C data in conjunction with hydrometric monitoring and an end-member mixing approach, we show that (i) >80% of the stream DOC flux flows through the most superficial soil horizons of the riparian domain and (ii) the soil DOC flux is comprised of DOC coming ultimately from both riparian and upland domains. Based on its δ13C fingerprint, we find that the upland DOC contribution decreases from ca. 30% of the stream DOC flux at the beginning of the high-flow period to <10% later in this period. Overall, upland domains contribute significantly to stream DOC export, but act as a size-limited reservoir, whereas soils in the wetland domains act as a near-infinite reservoir. Through this study, we show that δ13CDOC provides a powerful tool for tracing DOC sources and DOC transport mechanisms in headwater catchments.

scholarly journals DOC sources and DOC transport pathways in a small headwater catchment as revealed by carbon isotope fluctuation during storm events

2014 ◽  
Vol 11 (11) ◽  
pp. 3043-3056 ◽  
Author(s):  
T. Lambert ◽  
A.-C. Pierson-Wickmann ◽  
G. Gruau ◽  
A. Jaffrezic ◽  
P. Petitjean ◽  
...  
Keyword(s):  
High Resolution ◽  
High Flow ◽  
Published Data ◽  
Storm Events ◽  
Transport Pathways ◽  
Relative Contribution ◽  
Temporal And Spatial ◽  
High Flow Period ◽  
Doc Flux ◽  
Headwater Catchment

Abstract. Monitoring the isotopic composition (δ13CDOC) of dissolved organic carbon (DOC) during flood events can be helpful for locating DOC sources in catchments and quantifying their relative contribution to stream DOC flux. High-resolution (< hourly basis) δ13CDOC data were obtained during six successive storm events occurring during the high-flow period in a small headwater catchment in western France. Intra-storm δ13CDOC values exhibit a marked temporal variability, with some storms showing large variations (> 2 ‰), and others yielding a very restricted range of values (< 1 ‰). Comparison of these results with previously published data shows that the range of intra-storm δ13CDOC values closely reflects the temporal and spatial variation in δ13CDOC observed in the riparian soils of this catchment during the same period. Using δ13CDOC data in conjunction with hydrometric monitoring and an end-member mixing approach (EMMA), we show that (i) > 80% of the stream DOC flux flows through the most superficial soil horizons of the riparian domain and (ii) the riparian soil DOC flux is comprised of DOC coming ultimately from both riparian and upland domains. Based on its δ13C fingerprint, we find that the upland DOC contribution decreases from ca.~30% of the stream DOC flux at the beginning of the high-flow period to < 10% later in this period. Overall, upland domains contribute significantly to stream DOC export, but act as a size-limited reservoir, whereas soils in the wetland domains act as a near-infinite reservoir. Through this study, we show that δ13CDOC provides a powerful tool for tracing DOC sources and DOC transport mechanisms in headwater catchments, having a high-resolution assessment of temporal and spatial variability.

scholarly journals Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment

2021 ◽  
Vol 25 (9) ◽  
pp. 5133-5151
Author(s):  
Katharina Blaurock ◽  
Burkhard Beudert ◽  
Benjamin S. Gilfedder ◽  
Jan H. Fleckenstein ◽  
Stefan Peiffer ◽  
...  
Keyword(s):  
Riparian Zone ◽  
Hysteresis Loops ◽  
Hydrological Connectivity ◽  
Summer Drought ◽  
Carbon Cycles ◽  
Relative Contribution ◽  
Doc Export ◽  
Key Driver ◽  
Doc Load

Abstract. Understanding the controls on event-driven dissolved organic carbon (DOC) export is crucial as DOC is an important link between the terrestrial and the aquatic carbon cycles. We hypothesized that topography is a key driver of DOC export in headwater catchments because it influences hydrological connectivity, which can inhibit or facilitate DOC mobilization. To test this hypothesis, we studied the mechanisms controlling DOC mobilization and export in the Große Ohe catchment, a forested headwater in a mid-elevation mountainous region in southeastern Germany. Discharge and stream DOC concentrations were measured at an interval of 15 min using in situ UV-Vis (ultraviolet–visible) spectrometry from June 2018 until October 2020 at two topographically contrasting subcatchments of the same stream. At the upper location (888 m above sea level, a.s.l.), the stream drains steep hillslopes, whereas, at the lower location (771 m a.s.l.), it drains a larger area, including a flat and wide riparian zone. We focus on four events with contrasting antecedent wetness conditions and event size. During the events, in-stream DOC concentrations increased up to 19 mg L−1 in comparison to 2–3 mg L−1 during baseflow. The concentration–discharge relationships exhibited pronounced but almost exclusively counterclockwise hysteresis loops which were generally wider in the lower catchment than in the upper catchment due to a delayed DOC mobilization in the flat riparian zone. The riparian zone released considerable amounts of DOC, which led to a DOC load up to 7.4 kg h−1. The DOC load increased with the total catchment wetness. We found a disproportionally high contribution to the total DOC export of the upper catchment during events following a long dry period. We attribute this to the low hydrological connectivity in the lower catchment during drought, which inhibited DOC mobilization, especially at the beginning of the events. Our data show that not only event size but also antecedent wetness conditions strongly influence the hydrological connectivity during events, leading to a varying contribution to DOC export of subcatchments, depending on topography. As the frequency of prolonged drought periods is predicted to increase, the relative contribution of different subcatchments to DOC export may change in the future when hydrological connectivity will be reduced more often.

Influence of distorted inflows on the performance of a contra-rotating fan

2020 ◽  
pp. 1-18
Author(s):  
M.P. Manas ◽  
A.M. Pradeep
Keyword(s):  
Pressure Rise ◽  
Aircraft Engine ◽  
High Flow ◽  
Flow Coefficient ◽  
Potential Candidate ◽  
Blade Surface ◽  
Axial Fan ◽  
Stall Inception ◽  
Relative Contribution ◽  
Inflow Conditions

ABSTRACT A contra-rotating fan offers several aerodynamic advantages that make it a potential candidate for future aircraft engine configurations. Stall in a contra-rotating axial fan is interesting since instabilities could arise from either or both of the rotors. In this experimental study, a contra-rotating axial fan is analysed under clean or distorted inflow conditions to understand its performance and stall inception characteristics. The steady and unsteady measurements identified the relative contribution of each rotor towards the performance of the stage. The tip of rotor-1 is identified to be the most critical region of the contra-rotating fan. The contribution of rotor-2 to the overall loading of the stage is observed to be relatively less than rotor-1. The penalty due to distortion in the stage pressure rise is mostly felt by rotor-1, while rotor-2 also shows a reduction in performance for distorted inflows. Rotor-2 stalls at a high flow coefficient marking the initiation of partial stall of the stage, and the stall of the whole stage occurs once rotor-1 stalls. A fluid phenomenon that is attached to the blade surface marks the stall of rotor-1, and this fluid phenomenon initially rotates at a speed close to the speed of rotation of the blade. As the stage moves towards the fully developed stall, this fluid phenomenon sheds from the blade surface. The fluid phenomenon thus propagates at a speed much lower than the rotational speed of the blade during fully developed stall.

Hydraulic and treatment performance of pervious pavements under variable drying and wetting regimes

2011 ◽  
Vol 64 (8) ◽  
pp. 1692-1699 ◽  
Author(s):  
C. F. Yong ◽  
A. Deletic ◽  
T. D. Fletcher ◽  
M. R. Grace
Keyword(s):  
Suspended Solids ◽  
High Flow ◽  
Pollutant Removal ◽  
Low Flow ◽  
Storm Event ◽  
Stormwater Treatment ◽  
Storm Events ◽  
Treatment Technology ◽  
Porous Asphalt ◽  
Treatment Performance

Pervious pavements are an effective stormwater treatment technology. However, their performance under variable drying and wetting conditions have yet to be tested, particularly under a continuous time scale. This paper reports on the clogging behaviour and pollutant removal efficiency of three pervious pavement types over 26 accelerated years. These pavements were monolithic porous asphalt (PA), Permapave (PP) and modular Hydrapave (HP). Over a cycle of 13 days, the period of which was equivalent to the average annual Brisbane, Australia rainfall (1,200 mm), the pavements were randomly dosed with four different flows. Drying events of 3 h duration were simulated during each flow. Inflow and outflow samples were collected and analysed for Total Suspended Solids (TSS), Total Phosphorus (TP) and Total Nitrogen (TN). To evaluate the rate of clogging, a 1 in 5 year Brisbane storm event was simulated in the 6th, 8th, 12th, 16th, 20th and 24th week. Under normal dosing conditions, none of the pavements showed signs of clogging even after 15 years. However, under storm conditions, both PA and HP started to clog after 12 years, while PP showed no signs of clogging after 26 years. The drying and various flow events showed no effects in TSS removal, with all systems achieving a removal of approximately 100%. The average TP removal was 20% for all flows except for low flow, which had a significant amount of leaching over time. Leaching from TN was also observed during all flows except high flow. The TSS, TP and TN results observed during storm events were similar to that of high flow.

scholarly journals A database of marine and terrestrial radiogenic Nd and Sr isotopes for tracing earth-surface processes

2018 ◽  
Author(s):  
Cécile L. Blanchet
Keyword(s):  
River Sediments ◽  
Original Data ◽  
Isotopic Signature ◽  
Transport Processes ◽  
Sediment Provenance ◽  
Published Data ◽  
Sample Type ◽  
Management Service ◽  
Time Intervals ◽  
Available Information

Abstract. The database presented here contains radiogenic neodymium and strontium isotope ratios measured on both terrestrial and marine sediments. The main purpose of this dataset is to help assessing sediment provenance and transport processes for various time intervals. This can be achieved by either mapping sediment isotopic signature and/or fingerprinting source areas using statistical tools. The database has been built by incorporating data from the literature and the SedDB database and harmonizing the metadata, especially units and geographical coordinates. The original data were processed in three steps. Firstly, a specific attention has been devoted to provide geographical coordinates to each sample in order to be able to map the data. When available, the original geographical coordinates from the reference (generally DMS coordinates) were transferred into the decimal degrees system. When coordinates were not provided, an approximate location was derived from available information in the original publication. Secondly, all samples were assigned a set of standardized criteria that help splitting the dataset in specific categories. For instance, samples were discriminated according to their location Region, Sub-region and Location that relate to location at continental to city/river scale) or the sample type (terrestrial samples – aerosols, soil sediments, river sediments – or marine samples – marine sediment or trap sample). Finally, samples were distinguished according to their deposition age, which allowed to compute average values for specific time intervals. Graphical examples illustrating the functionality of the database are presented and the validity of the process was tested by comparing the results with published data. The dataset will be updated bi-annually and might be extended to reach a global geographical extent and/or add other type of samples. It is publicly available (under CC4.0-BY Licence) on the GFZ data management service at http://doi.org/10.5880/GFZ.5.2.2018.001.

Considerations on the influence of extreme events on the phosphorus transport from river catchments to the sea

2005 ◽  
Vol 51 (11) ◽  
pp. 193-204 ◽  
Author(s):  
M. Zessner ◽  
C. Postolache ◽  
A. Clement ◽  
A. Kovacs ◽  
P. Strauss
Keyword(s):  
Extreme Events ◽  
High Flow ◽  
Danube River ◽  
Flood Event ◽  
Phosphorus Transport ◽  
Flood Events ◽  
Relative Contribution ◽  
Extreme Flood ◽  
Flooded Areas ◽  
Total P

In this paper, results from rivers of different sizes in Romania, Hungary and Austria are presented. The paper shows the dynamics of extreme events and their contribution to the total P and suspended solids transported in these rivers. Special attention is paid to the influence of the size of the catchment and the event probability on the relative contribution of a single event to the total loads transported in the river. Further, the development of phosphorus loads along the Danube River at a flood event is shown. From the results it can be concluded that there is no immediate influence of high flow and flood events in upstream parts of the Basin on the transport of phosphorus from the catchment to the receiving Sea. Particle-bound phosphorus is mobilised from the catchment (through erosion) and the river bottom to a high extent at high flow events and transported at peak discharges to downstream, where retention by sedimentation of particles takes place. On the one hand this retention is a transport to flooded areas. In this case it can be considered as more or less long term retention. On the other hand sedimentation takes place in the riverbed, in case the tractive effort of the river is reduced. In this second case the P-pool in the sediments of the sedimentation area will be increased. If anaerobic conditions in the sediment appear, part of the phosphorus will be transformed to soluble ortho-phosphate and will continuously contribute to the phosphorus transport to the receiving sea. Part of the P-retained in the river sediment will be mobilised by resuspension at the next biggest high flow event. Altogether, these alternating processes of suspension, transport, export to flooded areas or sedimentation in the river bed with partly solution and partly resuspension at the next event decrease the share of the phosphorus transport during high flow events on the total loads transported in the more downstream parts of a catchments as compared to the more upstream parts. In the year of occurrence of an extreme flood event the P-transport of this year is dominated by the flood event. As an average over many years the contribution of high flow events to the total P-transport still may be between 7 and 20% in smaller catchments (around 1,000 km2). In a big catchment (e.g. river Danube) much smaller contributions of flood events on the total P-transport can be expected as an average over many years.

Carbon Dioxide Transport and Carbonic Anhydrase in Blood and Muscle

2000 ◽  
Vol 80 (2) ◽  
pp. 681-715 ◽  
Author(s):  
Cornelia Geers ◽  
Gerolf Gros
Keyword(s):  
Skeletal Muscle ◽  
Carbonic Anhydrase ◽  
Convective Transport ◽  
Transport Processes ◽  
The Body ◽  
Fiber Types ◽  
Carbon Dioxide Transport ◽  
Intracellular Space ◽  
Complex Interdependence ◽  
Relative Contribution

CO2produced within skeletal muscle has to leave the body finally via ventilation by the lung. To get there, CO2 diffuses from the intracellular space into the convective transport medium blood with the two compartments, plasma and erythrocytes. Within the body, CO2 is transported in three different forms: physically dissolved, as HCO3 −, or as carbamate. The relative contribution of these three forms to overall transport is changing along this elimination pathway. Thus the kinetics of the interchange have to be considered. Carbonic anhydrase accelerates the hydration/dehydration reaction between CO2, HCO3 −, and H+. In skeletal muscle, various isozymes of carbonic anhydrase are localized within erythocytes but are also bound to the capillary wall, thus accessible to plasma; bound to the sarcolemma, thus producing catalytic activity within the interstitial space; and associated with the sarcoplasmic reticulum. In some fiber types, carbonic anhydrase is also present in the sarcoplasm. In exercising skeletal muscle, lactic acid contributes huge amounts of H+ and by these affects the relative contribution of the three forms of CO2. With a theoretical model, the complex interdependence of reactions and transport processes involved in CO2 exchange was analyzed.

Hydrological controls of DOC export from Nordic headwater catchments. 

2021 ◽  
Author(s):  
Jacqueline Knutson ◽  
François Clayer ◽  
Magnus Norling ◽  
Ahti Lepistö ◽  
Hannu Marttila ◽  
...  
Keyword(s):  
Climate Change ◽  
Surface Waters ◽  
Data Set ◽  
Headwater Catchments ◽  
Lower Elevation ◽  
Hydrologic Controls ◽  
Doc Export ◽  
Doc Concentration ◽  
Long Term Trends ◽  
Source Limitation

&lt;p&gt;Nordic surface waters are currently much browner than during the 1980s due to drivers related to decreased acid deposition, and increased precipitation. While upward trends in concentration of DOC have been well documented, positive trends in the annual export of DOC are not as widespread. The variation in seasonality of DOC export may mask long-term trends in annual export. A large dataset of 30 natural headwater catchments from Finland, Norway, and Sweden contains more than 20 years of discharge and DOC records. We will use these data to better quantify the trends of DOC export and their relationships to seasonality and the effects of climatic changes seen over the last few decades, such as diminished snowpack, less distinct snowmelt events and increases in autumn precipitation. We will investigate both the seasonal and annual relationships between DOC concentration and discharge (C-Q) and test if they relate to time and catchment characteristics such as size, latitude, and landcover.&lt;/p&gt;&lt;p&gt;We explore 3 hypotheses in this data set. First, spring DOC export is decreased due to less distinct snowmelt and runoff events while autumn export of DOC is increased as a consequence of more autumn runoff. Second, we propose that catchments with a longer or more distinct snow cover period are more sensitive than catchments at lower elevation or latitude due to the length of inactivity caused by low temperatures and a more defined snowmelt runoff event. Third, we hypothesize the negative C-Q relationship in winter and spring is likely due to source limitation and dilution while hydrologic controls in summer and autumn are associated with positive C-Q relationships.&lt;/p&gt;&lt;p&gt;Climate change is promoting enhanced export of DOC from soils towards surface waters, leading to more carbon processed and transported along the aquatic continuum from headwaters to coast. This data set gives us an opportunity to look at a diverse set of headwater catchments in the Nordic region, an area disproportionally affected by climate change, to clarify the hydrologic components and how this will affect overall carbon transport.&amp;#160;&lt;/p&gt;

scholarly journals The Blood-Brain Barrier Thyroxine Transporter Organic Anion-Transporting Polypeptide 1c1 Displays Atypical Transport Kinetics

Endocrinology ◽  
2009 ◽  
Vol 150 (11) ◽  
pp. 5153-5162 ◽  
Author(s):  
Daniel E. Westholm ◽  
David R. Salo ◽  
Kevin J. Viken ◽  
Jon N. Rumbley ◽  
Grant W. Anderson
Keyword(s):  
Binding Sites ◽  
Organic Anion ◽  
Transport Processes ◽  
Transport Kinetics ◽  
Brain Barrier ◽  
Hek293 Cells ◽  
Published Data ◽  
Organic Anion Transporting Polypeptide ◽  
Wide Range ◽  
Dependent Inhibition

Organic anion-transporting polypeptide (Oatp) 1c1 is a high-affinity T4 transporter expressed in brain barrier cells. Oatp1c1 transports a variety of additional ligands including the conjugated sterol estradiol 17β-glucuronide (E217βG). Intriguingly, published data suggest that E217βG inhibition of Oatp1c1-mediated T4 transport exhibits characteristics suggestive of atypical transport kinetics. To determine whether Oatp1c1 exhibits atypical transport kinetics, we first performed detailed T4 and E217βG uptake assays using Oatp1c1 stably transfected HEK293 cells and a wide range of T4 and E217βG concentrations (100 pm to 300 nm and 27 nm to 200 μm, respectively). Eadie-Hofstee plots derived from these detailed T4 and E217βG uptake experiments display a biphasic profile consistent with atypical transport kinetics. These data along with T4 and E217βG cis-inhibition dose-response measurements revealed shared high- and low-affinity Oatp1c1 binding sites for T4 and E217βG. T4 and E217βG recognized these Oatp1c1 binding sites with opposite preferences. In addition, sterols glucuronidated in the 17 or 21 position, exhibited preferential substrate-dependent inhibition of Oatp1c1 transport, inhibiting Oatp1c1-mediated E217βG transport more strongly than T4 transport. Together these data reveal that Oatp1c1-dependent substrate transport is a complex process involving substrate interaction with multiple binding sites and competition for binding with a variety of other substrates. A thorough understanding of atypical Oatp1c1 transport processes and substrate-dependent inhibition will allow better prediction of endo- and xenobiotic interactions with the Oatp transporter.

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