Key Factors of Precipitation Stable Isotope Fractionation in Central-Eastern Africa and Central Mediterranean

Abstract

The processes of isotope fractionation in the hydrological cycle naturally occur during vapor formation, vapor condensation, and moisture transportation. These processes are therefore dependent on local and regional surface and atmospheric physical features such as temperature, pressure, wind speed, and land morphology, and hence on the climate. Because of the strong influence of climate on the isotope fractionation, latitudinal and altitudinal effects on the δ18O and δ2H values of precipitation at a global scale are observed. In this study, we present and compare the processes governing precipitation isotope fractionation from two contrasting climatic regions: Virunga in Central-Eastern Africa and the Central Mediterranean (Stromboli and Sicily, Italy). While Virunga is a forested rainy tropical region located between Central and Eastern Africa, the Mediterranean region is characterized by a rainy mild winter and a dry hot summer. The reported δ18O and δ2H dataset are from precipitation collected on rain gauges sampled either on a monthly or an approximately bimonthly basis and published in previous papers. Both regions show clearly defined temporal and altitudinal variations of δ18O and δ2H, depending on precipitation amounts. The Central Mediterranean shows a clear contribution of local vapor forming at the sea–air interface, and Virunga shows a contribution from both local and regional vapor. The vapor of Virunga is from two competing sources: the first is the continental recycled moisture from soil/plant evaporation that dominates during the rainy season, and the second is from the East African Great Lakes evaporation that dominates during the dry season.

Hydrochemical study of bottled water in Rwanda and relationship with their origin

“…Negative relationships were found between both brand-weighted δ 18 O and δ 2 H and the altitude, (Figure 6). The vertical oxygen gradient is À0.12 ‰/100 m and that of δ 2 H is À0.9 ‰ /100 m. This value is similar to that found for precipitation waters in Central-Eastern Africa (À0.15 ‰ /100 m for δ 18 O and À0.86 ‰/100 m for δ 2 H) (Balagizi & Liotta 2019). The altitude gradient is À0.16‰ /100 m for δ 18 O in the Mount Cameroon region (Fontes & Olivry 1977).…”

“…The continental moisture issue from surface water evaporation and/or evapotranspiration (recycling continental process) gives rainfall with d-excess values higher to þ10‰ (Njitchoua et al 1999). Half of waters, present a higher d-excess showing rainfall then recharge aquifer are issue from a recycling continental process conform to the results of rainfall in central eastern Africa (Balagizi & Liotta 2019), explained by an area located in the middle of Africa with large forest zone and surface water under tropical climate.…”

Determination of exogenous water in grape juice through the isotopic analysis of 18O/16O

“…Isotopic fractionation processes occur naturally during the cycle of vapor formation, vapor condensation and moisture transport. According to some authors, an isotopic fractionation can occur due to heating, and the extent of this fractionation depends on factors such as relative humidity, wind speed, pressure, precipitation and temperature (Balagizi & Liotta, 2019;Rahul et al, 2018). In this test it was possible to observe that the isotopic results, after heating the juices with both the open lids and the closed lids, did not present statistically significant differences, demonstrating that the heating that occurs during the process of making juices did not interfere with isotopic results and, consequently, did not influence the method of analysis.…”

Shading Net and Partial Covering Plastic Film Do Not Affect Phenology, Photosynthetic Activity or Fruit Quality Traits of Kensington Pride Mango

“…The first observations were made at Full Flowering, identified by the phenological stage 615 of the BBCH scale for mango [68], and continued until harvest. The climate of the area is identified as Mediterranean in the Koppen classification [69][70][71], with an average yearly temperature of 17-18 • C and average yearly rainfall between 800 and 1000 mm [7].…”