scholarly journals The Analysis of Short-Term Dataset of Water Stable Isotopes Provides Information on Hydrological Processes Occurring in Large Catchments from the Northern Italian Apennines

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1360 ◽  
Author(s):  
Cervi ◽  
Dadomo ◽  
Martinelli
Keyword(s):  
Stable Isotopes ◽  
Isotopic Composition ◽  
Sine Wave ◽  
Hydrological Processes ◽  
Water Molecules ◽  
Residence Times ◽  
Catchment Characteristics ◽  
Mean Residence Times ◽  
Italian Apennines ◽  
Short Time

This study discusses a dataset of water stable isotopes from precipitation (4 rain gauges) and surficial water (9 rivers) from the northern Italian Apennines, an area in which clay-rich bedrocks widely outcrop and the runoff response to precipitation events is very rapid. The dataset has been compiled starting from existing data that had previously been published in the literature and consists of monthly values of stable isotopes oxygen-18 (18O) and deuterium (2H) lasting over the period from January 2003 to December 2006 (precipitation) and from January 2006 to December 2007 (surficial water). For this period, mean residence times estimated by means of a sine-wave fitting technique make evident the significant differences over time spent by water molecules within the 9 catchments. Moreover, isotopic compositions of rivers deviated from those of precipitations revealing the influence of some catchment characteristics in differentiating the isotopic composition in rivers. Further correlations between mean residence times of river water and selected catchment characteristics reveal the role of orography and bedrocks in delaying the water molecules during their flow-paths. In addition, time series and cross–correlation analyses indicate a certain control by the main watershed divide on the isotopic composition of river waters, which is reflected in a progressive isotopic variation with longitude. The study shows that, despite using a short-time dataset (2-years for surficial water) of sparse stable isotopes can provide remarkable indications for depicting hydrological processes in large catchments made up of clay-rich bedrocks.

scholarly journals Characterisation of stable isotopes to identify residence times and runoff components in two meso-scale catchments in the Abay/Upper Blue Nile basin, Ethiopia

2014 ◽  
Vol 18 (6) ◽  
pp. 2415-2431 ◽  
Author(s):  
S. Tekleab ◽  
J. Wenninger ◽  
S. Uhlenbrook
Keyword(s):  
Stable Isotopes ◽  
Stable Isotope ◽  
Isotopic Composition ◽  
Residence Times ◽  
Nile Basin ◽  
Blue Nile ◽  
Source Areas ◽  
Blue Nile Basin ◽  
Mean Residence Times ◽  
Meso Scale

Abstract. Measurements of the stable isotopes oxygen-18 (18O) and deuterium (2H) were carried out in two meso-scale catchments, Chemoga (358 km2) and Jedeb (296 km2) south of Lake Tana, Abay/Upper Blue Nile basin, Ethiopia. The region is of paramount importance for the water resources in the Nile basin, as more than 70% of total Nile water flow originates from the Ethiopian highlands. Stable isotope compositions in precipitation, spring water and streamflow were analysed (i) to characterise the spatial and temporal variations of water fluxes; (ii) to estimate the mean residence time of water using a sine wave regression approach; and (iii) to identify runoff components using classical two-component hydrograph separations on a seasonal timescale. The results show that the isotopic composition of precipitation exhibits marked seasonal variations, which suggests different sources of moisture generation for the rainfall in the study area. The Atlantic–Indian Ocean, Congo basin, Upper White Nile and the Sudd swamps are the potential moisture source areas during the main rainy (summer) season, while the Indian–Arabian and Mediterranean Sea moisture source areas during little rain (spring) and dry (winter) seasons. The spatial variation in the isotopic composition is influenced by the amount effect as depicted by moderate coefficients of determination on a monthly timescale (R2 varies from 0.38 to 0.68) and weak regression coefficients (R2 varies from 0.18 to 0.58) for the altitude and temperature effects. A mean altitude effect accounting for −0.12‰/100 m for 18O and −0.58‰/100 m for 2H was discernible in precipitation isotope composition. Results from the hydrograph separation on a seasonal timescale indicate the dominance of event water, with an average of 71 and 64% of the total runoff during the wet season in the Chemoga and Jedeb catchments, respectively. Moreover, the stable isotope compositions of streamflow samples were damped compared to the input function of precipitation for both catchments. This damping was used to estimate mean residence times of stream water of 4.1 and 6.0 months at the Chemoga and Jedeb catchment outlets, respectively. Short mean residence times and high fractions of event water components recommend catchment management measures aiming at reduction of overland flow/soil erosion and increasing of soil water retention and recharge to enable sustainable development in these agriculturally dominated catchments.

Is Lewis Acidity in Metal Dications Triggered by Solvent Shell Fluctuations?

2018 ◽  
Author(s):  
Tony Stace
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Metal Ion ◽  
Time Difference ◽  
Lewis Acidity ◽  
Water Molecules ◽  
Central Metal ◽  
Residence Times ◽  
Gas Phase Clusters ◽  
Mean Residence Times

Using experimental data collected on the stabilities of gas phase clusters consisting of metal dications in association with water molecules, a model is proposed to account for Lewis acidity. It is suggested that acidity is driven be fluctuations in the numbers of water molecules surrounding a metal ion, and that these fluctuations reduce numbers in the coordination shells to below those need to stabilise a +2 charge on the metal. The timescale on which these fluctuations are calculated to occur is approximately 6 orders of magnitude longer than any of the measure mean residence times of water molecules surrounding a central metal ion. This time difference reflects both the rarity of the event require to drive acidity and the extreme nature of some of the fluctuations.

Pathways and mean residence times of dissolved pollutants in the ocean derived from transient tracers and stable isotopes

1999 ◽  
Vol 237-238 ◽  
pp. 15-30 ◽  
Author(s):  
P. Schlosser ◽  
R. Bayer ◽  
G. Bönisch ◽  
L.W. Cooper ◽  
B. Ekwurzel ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Residence Times ◽  
Mean Residence Times

Is Lewis Acidity in Metal Dications Triggered by Solvent Shell Fluctuations?

2018 ◽  
Author(s):  
Tony Stace
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Metal Ion ◽  
Time Difference ◽  
Lewis Acidity ◽  
Water Molecules ◽  
Central Metal ◽  
Residence Times ◽  
Gas Phase Clusters ◽  
Mean Residence Times

Using experimental data collected on the stabilities of gas phase clusters consisting of metal dications in association with water molecules, a model is proposed to account for Lewis acidity. It is suggested that acidity is driven be fluctuations in the numbers of water molecules surrounding a metal ion, and that these fluctuations reduce numbers in the coordination shells to below those need to stabilise a +2 charge on the metal. The timescale on which these fluctuations are calculated to occur is approximately 6 orders of magnitude longer than any of the measure mean residence times of water molecules surrounding a central metal ion. This time difference reflects both the rarity of the event require to drive acidity and the extreme nature of some of the fluctuations.

scholarly journals Identifying residence times and streamflow generation processes using δ<sup>18</sup>O and δ<sup>2</sup>H in meso-scale catchments in the Abay/Upper Blue Nile, Ethiopia

2013 ◽  
Vol 10 (8) ◽  
pp. 10333-10377 ◽  
Author(s):  
S. Tekleab ◽  
J. Wenninger ◽  
S. Uhlenbrook
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Isotope Composition ◽  
Spring Water ◽  
Residence Times ◽  
Nile Basin ◽  
Source Areas ◽  
Mean Residence Times ◽  
Seasonal Time Scale ◽  
Meso Scale

Abstract. Measurements of the stable isotopes oxygen-18 (18O) and deuterium (2H) were carried out in two meso-scale catchments, Chemoga (358 km2) and Jedeb (296 km2) south of Lake Tana, Abay/Upper Blue Nile basin, Ethiopia. The region is of paramount importance for the water resources in the Nile basin. Stable isotope composition in precipitation, spring water and streamflow were analyzed (i) to characterize the spatial and temporal variations of water fluxes; (ii) to estimate the mean residence time of water using a sine wave regression approach; and (iii) to identify runoff components using classical two component hydrograph separations at a seasonal time scale. The results show that the isotopic composition of precipitation exhibit marked seasonal variations, which suggests different sources of moisture generation for the rainfall in the study area. The Atlantic–Indian ocean, Congo basin, and the Sud swamps are the likely the potential moisture source areas during the main rainy (summer) season. While, the Indian–Arabian, and Mediterranean Sea moisture source areas during little rain (spring), and dry (winter) seasons. The spatial variation of the isotopic composition is affected by the amount effect and to less extent by altitude and temperature effects. A mean altitude effect of −0.12‰ (100 m)−1 for 18O and −0.58‰ (100 m)−1 for 2H were discernable in precipitation isotope composition. The seasonal variations of the isotopic signature of the spring water exhibit a damped response as compared to the river waters, which shows that the spring water has longer residence times than the river water. Results from the hydrograph separation at a seasonal time scale indicate the dominance of event water with an average of 71% and 64% of the total runoff during the wet season in the Chemoga and Jedeb catchment, respectively. The stable isotope compositions of streamflow samples were damped compared to the input function of precipitation for both catchments and this damping was used to estimate mean residence times of stream water of 4.1 and 6.0 months at the Chemoga and Jedeb catchment outlet, respectively. Short mean residence times and high proportions of event water components suggest catchment management measure aiming at reduction of overland flow/soil erosion and increasing of soil water retention and recharge to enable sustainable development in these agricultural dominated catchments.

Ecological and isotopic discrimination of syntopic rodents in a neotropical rain forest of French Guiana

2003 ◽  
Vol 19 (2) ◽  
pp. 209-214 ◽  
Author(s):  
Jean-François Mauffrey ◽  
François Catzeflis
Keyword(s):  
Stable Isotopes ◽  
Isotopic Composition ◽  
Rain Forest ◽  
French Guiana ◽  
Ecological Studies ◽  
Carbon Isotope Ratios ◽  
Photosynthetic Pathways ◽  
Feeding Process ◽  
Neotropical Rain Forest

Stable isotopes are commonly used in ecological studies to infer food resources (Ambrose & DeNiro 1986, Bocherens et al. 1990,1991,1994;Yoshinaga et al. 1991) since isotopic composition is conserved during the feeding process. Moreover,for herbivorous (sensu lato) species, it is often possible to identify the main resource because different photosynthetic pathways generate different values of carbon isotope ratios (Park & Epstein 1961, Sternberg et al. 1984). This allows the characterization of broad biota such as savannas or forest and discrimination of grazers from sympatric folivorous species (DeNiro & Epstein 1978).

High-frequency river chemistry unveils the inner workings of concentration-discharge relationships during flood events

2021 ◽  
Author(s):  
Paul Floury ◽  
Julien Bouchez ◽  
Jérôme Gaillardet ◽  
Arnaud Blanchouin ◽  
Patrick Ansart
Keyword(s):  
High Frequency ◽  
Agricultural Watershed ◽  
Hydrological Processes ◽  
Rain Event ◽  
Exact Nature ◽  
Flood Events ◽  
Event Stream ◽  
Major Species ◽  
Solute Fluxes ◽  
Short Time

&lt;p&gt;Shifts in water fluxes through the Critical Zone exert a major control on stream solute export, but the exact nature of this control is still obscure, especially at the scale of relatively short flood events. To address this question, here we take advantage of a new high-frequency, flood event stream concentration&amp;#8211;discharge (C-Q) dataset. Stream dissolved concentration of major species were recorded every 40 minutes over five major flood events in 2015/2016 recorded in a French agricultural watershed using device called the &quot;River Lab&quot;. We focus our attention on the flood recession periods to highlight how C-Q relationships are controlled by hydrological processes within the catchment rather than by the dynamics of the rain event.&lt;/p&gt;&lt;p&gt;We show that for C-Q relationships resulting from data acquisition over multi-year time scales and including several flood events, lumping all trends together potentially result in biases in characteristic parameters (such as exponents of a power-law fit), that are strongly dictated by data from the recession periods of the most intense floods alone.&lt;/p&gt;&lt;p&gt;In order to evaluate the role of mixing of pre-existing water and solute pools in the catchment, we apply to solute fluxes an approach previously developed in catchment hydrology linking water storage and stream flow. This approach, which considers that hydrological processes prevail over chemical interactions during the short time spans of flood events, allows us to reproduce at first order a large diversity of shapes of recession C-Q relationships.&lt;/p&gt;

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