Distribution of tritium and stable isotopes in precipitation in Syria

The paper discusses aspects of the isotopic composition (tritium and stable isotopes) of precipitation, which was monitored from 2000 to 2003 at 12 stations in Syria. The seasonal variations in delta O-18 are smaller at the western stations than at the eastern ones due to low seasonal temperature variations. A good correlation between delta H-2 and delta O-18 was obtained for each station, and the slopes of the local meteoric water lines are significantly lower than the Global Meteoric Water Line. Values of d-excess decrease from 19 parts per thousand at the western stations to 13 parts per thousand at the eastern ones, indicating the influence of precipitation generated by air masses coming from the Mediterranean Sea. A reliable altitude effect represented by depletion of heavy stable isotopes (delta O-18 and delta H-2), of about -0.21 parts per thousand and - 1.47 parts per thousand per 100 m elevation, respectively, was observed. Monthly tritium contents in precipitation, and seasonal variations, are less at the western stations than at the eastern ones. The weighted mean tritium values are between 3 and 9 TU, and increase with distance from the Syrian coast by 1 TU/100 km.