Spatial Mapping of Atmospheric Precipitation Isotopes in Syria

Abstract

Stable isotope ratios (δ²H and δ¹⁸O), tritium (³H). and deuterium excess (d-excess) values of atmospheric precipitation (P) at 16 stations were determined for mapping the spatial variation of oxygen and hydrogen P isotopes in Syria. The major geographical parameters (longitude east, LE; latitude north, LN; altitude, H; and inland distance from the coast, DFC) were used to find out the best fitting models for the spatial mapping of atmospheric P isotopes in Syria. The highest correlation coefficients (r>0.73) were found for the relationships δ¹⁸O-H and δ²H-H. The impacts of LE and LN factors were rather moderate (0.3<r<0.6). However, a high correlation coefficient (r>0.7) was found for the relationship d-excess-LN. The increase of d-excess value from 23‰ to 24‰ in southern Syria is due to the Mediterranean Sea (MS) moisture, likely as a high percentage (>65%) of prevailed winds usually comes over the MS. The concentrations of ³H in P samples(4-14TU) during the period 1989–1993 were higher than those (3-10TU) for the period 2004–2006, indicating thus a return back toward the levels of typical ³H production in nature. The high correlation coefficients (r>0.59) that were found for the relationships ³H-DFC and ³H-LE, suggest a continuous exchange between the low tritium moisture from the MS and the higher tritium moisture from the inland areas. Produced gridded isotopic values are quite satisfactory for covering certain areas in Syria and the neighboring Arab countries.