Dynamics of Water Soil Storage in the Unsaturated Zone of a Sand Dune in a Semi-Arid Region Traced by Humidity and Carbon Isotopes: The Case of Ashdod, Israel

Radiocarbon ◽  
2018 ◽  
Vol 60 (4) ◽  
pp. 1259-1267 ◽  
Author(s):  
Israel Carmi ◽  
Mariana Stiller ◽  
Joel Kronfeld
Keyword(s):  
Carbon Isotopes ◽  
Unsaturated Zone ◽  
Carbonic Acid ◽  
Isotopic Fractionation ◽  
Large Variability ◽  
Local Climate ◽  
Sparse Vegetation ◽  
Carbon Isotopic ◽  
Semi Arid Region ◽  
Semi Arid

ABSTRACTA 22 m sediment core was collected from the unsaturated zone (USZ) in the dunes south of Ashdod, Israel, in a low rainfall year, following an even lower-rainfall year. The mineralogy of was quartz with some clay and carbonate. The local climate is semi-arid. The roots of the sparse vegetation can reach ~8 m. The porosity was ~40–55%. The DIC ranged from 2 to 13 mmole C/L. Large variability is noted in the soil moisture, with a maximum at the high clay region at ~8 m. Oxygen isotopes enter the USZ with rain falling on the surface. There is18O enrichment in the top of the section due to evaporation during the summer. Below this depth δ18O values of ~ –5‰ prevail as in the local aquifer. CO2and the carbon isotopes enter the USZ laterally by exhalation from roots. The δ13C varies from –5‰ to –23‰, representing stages in carbon isotopic fractionation: CO2gasbecomes dissolved CO2aqueouswhich then forms carbonic acid and HCO3–. The high δ13C, Δ14C, and DIC are found at the 8 m depth. These values along with high humidity are replicated at ~22m depth. They most probably represent recharge water from the previous rainy season at 8 m depth subsequently pushed down 12.8±0.8 m during the last winter.

Variations in Soil CO2 Concentrations and Isotopic Values in a Semi-Arid Region Due to Biotic and Abiotic Processes in the Unsaturated Zone

Radiocarbon ◽  
2013 ◽  
Vol 55 (2) ◽  
pp. 932-942 ◽  
Author(s):  
I Carmi ◽  
D Yakir ◽  
Y Yechieli ◽  
J Kronfeld ◽  
M Stiller
Keyword(s):  
Unsaturated Zone ◽  
Arid Region ◽  
Carbonic Acid ◽  
Root Zone ◽  
Soil Gas ◽  
Soil Co2 ◽  
Co2 Concentrations ◽  
Measured Profile ◽  
Semi Arid Region ◽  
Semi Arid

A study of CO2 in soil gas was conducted in a bare plot in the unsaturated zone (USZ) of Yatir Forest, northern Negev, Israel. In 2006, 6 tubes for sampling of soil gas were inserted into the USZ to depths of 30, 60, 90, 120, 200, and 240 cm. Profiles of soil gas in the USZ were collected from the tubes 5 times between October 2007 and September 2008. Measurements of the collected profiles of soil gas were of CO2 (ppm), δ13C (′), and Δ14C (′). At all times, the concentration of CO2 in the soil gas was higher than in the air at the surface (CO2 ≃ 400 ppm; δ13C ≃ −9′). The main source of the CO2 in soil gas is from biotic activity released through roots of trees and of seasonal plants close to the surface. In the winter, the CO2 concentrations were lowest (6000 ppm) and the δ13C was −20′. In the spring and through the summer, the CO2 concentration increased. It was estimated that the major source of CO2 is at ≃240 cm depth (δ13C ≃ −22′; CO2 ≃ 9000 ppm) or below. Above this level, the concentrations decrease and the δ13C (′) become more positive. The 14C values in the measured profile are all less than atmospheric and biotic 14C. It was deduced that biotic CO2 dissolves in porewater to form carbonic acid, which then dissolves secondary carbonate (δ13C ≃ −8′; 14C ≃ −900′) from the sediments of the USZ. With the 14C data, the subsequent release of CO2 into the soil gas was then estimated. The 14C data, supported by the 13C and CO2 data, also indicate a biotic source at the root zone, at about 90 cm depth.

scholarly journals Evaluating Dissolved Inorganic Carbon Cycling in a Forested Lake Watershed Using Carbon Isotopes

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 636-645 ◽  
Author(s):  
Ramon Aravena ◽  
S. L. Schiff ◽  
S. E. Trumbore ◽  
P. J. Dillon ◽  
Richard Elgood
Keyword(s):  
Isotopic Composition ◽  
Carbon Isotopes ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Isotopic Composition ◽  
Isotopic Fractionation ◽  
Early Spring ◽  
Late Winter ◽  
Isotope Pattern ◽  
Carbon Isotopic

Dissolved inorganic carbon (DIC) is the main acid buffer in forested lake watersheds in Canada. We used carbon isotopes (13C, 14C) to evaluate the production and cycling of DIC in an acid-sensitive lake watershed of the Precambrian Shield. Soil CO2, groundwater and stream DIC were characterized chemically and isotopically. Soil CO2 concentration profiles reflect both changes in production and in losses due to diffusion. δ13C soil CO2 profiles (δ13C values of −23‰ in summer, slightly enriched during the fall and −25%‰ during the winter) are a reflection of the isotopic composition of the sources and changes in isotopic fractionation due to diffusion. Carbon isotopic composition (13C, 14C) of the groundwater and stream DIC clearly indicate that weathering of silicates by soil CO2 is the main source of DIC in these watersheds. 14C data show that, in addition to recent groundwater, an older groundwater component with depleted 14C activity is also present in the bedrock. The carbon isotope pattern in the groundwater also implies that, besides the main springtime recharge events, contributions to the groundwater may also occur during late winter/early spring.

Variations in the Isotopic Composition of Dissolved Inorganic Carbon in the Unsaturated Zone of a Semi-Arid Region

Radiocarbon ◽  
2015 ◽  
Vol 57 (3) ◽  
pp. 397-406 ◽  
Author(s):  
I Carmi ◽  
D Yakir ◽  
Y Yechieli ◽  
J Kronfield ◽  
M Stiller
Keyword(s):  
Unsaturated Zone ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Sediment Cores ◽  
Tritium Content ◽  
Organic Debris ◽  
Different Seasons ◽  
Semi Arid Region ◽  
Semi Arid

A study of water and carbon isotopes was conducted in a bare plot in the unsaturated zone of the Yatir Forest in the northern Negev of Israel. Sediment cores were collected in three different seasons. Measurements include profiles of mineralogy, moisture and its δ18O and tritium content, dissolved inorganic carbon (DIC) and its δ13C (‰) and Δ14C (‰) content, and δ13C (‰) and Δ14C (‰) in the solid sediment. The profiles of moisture and δ18O in the cores show clearly the effect of evaporation. The tritium profile indicates infiltration of water (0.11 m yr−1). The source of carbon in the DIC is CO2 released by biotic activity through roots of trees and of seasonal plants, which show seasonal variations, and by decay of organic debris. The δ13C (‰) profiles show clearly the chemical transition from dissolved CO2 (δ13C = −22‰) to bicarbonate (δ13C = −14‰). At greater depth (–11.3‰), the δ13C becomes similar to the δ13C in the aquifer below (–12.5‰). The effect of secondary processes is evident in the profile of Δ14C in the DIC. It shows a clear decrease with depth due to exchange with the sediment at a rate of 10‰ yr−1. Precipitation of carbon from the DIC on the sediment is 1.1 mg C Lsed−1 yr−1, negligible compared to the 28 g C in 1 Lsed. In the solid sediment, there is a gradient in Δ14Ccarb at the top meter. The net precipitation of 14C from the DIC on the sediment (0.25 to 1.1‰ yr−1), corrected for decay, cannot be observed in the deeper sediment. The presence of 14C in the top 1 m of the sediment is explained by two possible processes: accumulation of 14C-tagged dust (∼0.05 mm yr−1) and/or long-term cumulative precipitation from the DIC.

Carbon isotopes in Sphagnum from Kyushu, Japan, and their relationship with local climate

2015 ◽  
Vol 49 (5) ◽  
pp. 495-502 ◽  
Author(s):  
Saki Yasuda ◽  
Seigo Ooki ◽  
Hiroshi Naraoka ◽  
Tasuku Akagi
Keyword(s):  
Carbon Isotopes ◽  
Local Climate

The Molecular Characterization and Biological Assessment of the Leaves Extracts of Loofah Reveal their Nutraceutical Potential

2020 ◽  
Vol 11 ◽  
Author(s):  
Takoua Ben Hlel ◽  
Feten Belhadj ◽  
Fatih Gül ◽  
Muhammed Altun ◽  
Ayşe Şahin Yağlıoğlu ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Phenolic Compounds ◽  
Hela Cell ◽  
Arid Region ◽  
Biological Properties ◽  
Biological Assessment ◽  
Omega 3 ◽  
Hela Cell Lines ◽  
Semi Arid Region ◽  
Semi Arid

Background:: Luffa cylindrica is a plant that is widely distributed in Africa and Asia and it can be grown in regions with tropical or subtropical climates. Few patents dealt with Loofah biological properties, including some functional foods formulated from its leaves. Objective:: This study aimed to structurally and functionally characterize the bioactive compounds of L. cylindrica leaves grown in two different environments. Methods:: The extracts of L. cylindrica leaves collected from two Tunisian locations: Essouasi (LE), a semi-arid region and Medenine (LM) an arid region, were investigated for their phenolic compounds and fatty acids using HPLC/TOF-MS and GCMS techniques respectively. Furthermore, the antioxidant capacity was evaluated with DPPH, Chelating effect, Hydroxyl radical and Superoxide anion scavenging activities while the anticancer activity against HeLa cell lines was assessed using xCELLigence real time cell analyzer and lactate dehydrogenase cytotoxicity assay. Results:: The antiproliferative capacity of both extracts was time and dose-dependent with LE presenting the lowest HeLa cell index (CI = 0.035 ± 0.018, 250 μg/ml). LE also showed the best cytotoxic capacity (56.49 ± 0.8%) and antioxidant potential (IC50 = 54.41 ± 1.12 μg/ml for DPPH and 12.12 ± 0.07 μg/ml for chelating effet). 14 phenolic compounds were detected in LE with ferulic acid being the major compound (5128.5 ± 4.09 μg Phenols/g) while LM had only 6 phenolics. GCMS analysis showed the presence of omega-3 fatty acids in LE. Conclusions:: Our findings suggest that L. cylindrica leaves, especially when collected from semi-arid regions, are promising for formulating nutraceuticals of interest.

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