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Journal of Environmental Hydrology
ISSN 1058-3912 |
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Electronic Journal of the International Association for
Environmental Hydrology
JEH Volume 13 (2005), Paper 29 Posted December 17, 2005 CHEMICAL AND ISOTOPIC COMPOSITION OF RAINWATER IN COASTAL AND HIGHLAND REGIONS IN LEBANON
Zeinab Saad1,2 2Laboratory of Water and Environmental Sciences, Lebanese Atomic Energy Commission ABSTRACT Rainwater samples were collected from six stations at coastal and highland regions in Lebanon and analyzed for the major species Ca2+, K+, Na+, Mg2+, NO3-, NH4+, pH, Cl-, and SO42-. Absolute concentrations and element-to-sodium ratios show clear variations with higher levels found in coastal stations and lower levels found in continental sites for most of the species. Levels of major species from coastal areas can be twice as high as those of the highlands, in terms of both absolute concentration and element-to-sodium ratio. The contrast between low and high altitudes can be explained by proximity to the Mediterranean Sea and local agricultural pollution sources. Isotopic composition of rainwater in coastal sites presents high values of d18O and dD, whereas rainwater in continental areas is characterized by low values of d18O and dD. The altitude effect influences the isotopic fractionation in precipitation, including depletion in both d18O and dD, especially in stations at high elevation. The Lebanese Meteoric Water Line was defined as dD = 7.13 d18O + 15.98. This relation is close to the Regional Meteoric Water Line in the eastern Mediterranean with a lower d-excess indicating a relatively less pronounced secondary evaporation effect in Lebanon. From a series of 3H data of monthly precipitation from six stations within the small country of Lebanon, we concluded that between the stations there are no significant differences in altitude effect. However, a small continental effect is apparent at the Baalbak station. Reference: Saad, Z., V. Kazpard, A.G. El Samrani, and K. Slim. 2005. Chemical and Isotopic Composition of Rainwater in Coastal and Highland Regions in Lebanon, Journal of Environmental Hydrology, Vol. 13, Paper 29. CONTACT: Dr. Zeinab Saad Lebanese Atomic Energy Commission CNRS P.O.Box 11-8281 Beirut, Lebanon E-mail: zsaad@cnrs.edu.lb |
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