Chemical composition of rainwater and the acid neutralization effect at Tartous and Kadmous sites in coastal area of Syria

The chemical compositions were measured in rainwater samples collected from December 2019 to March 2021 from two representative sites; Tartous city and sub-urban of Kadmous. Both sites were located on the east Mediterranean coast of western Syria. The rainwater was alkaline with a volume-weighted mean (VWM) pH of 6.94 and 6.46 at Tartous and Kadmous respectively. Tartous had much higher concentrations of total ions in rainwater (2505µeq/L) than those in rainwater at Kadmous (836µeq/L). Ca 2+ , the most abundant ion with a VWM concentration of 738µeq/L and 269µeq/L and accounted for 30% of the total ionic at both sites. The SO 4 2− and NO 3 − concentration of rainwater in Tartous was three and six times that in Kadmous. The strong coefficient of (nssSO 4 2− + NO 3 − ) vs .(Ca 2+ ) correlation ( r  = 0.9) indicates that Ca 2+ ion is the major neutralizing factor and the percentages of the potential acidity neutralize by Ca 2+ were 77% and 79% in rainwater respectively. The high coefficient of Na + and Cl − correlation ( r  = 0.99) indicated marine components at both sites. Using Na + as an indicator of marine origin, and Ca 2+ for the terrestrial inputs, the proportions of sea salt and terrestrial elements were estimated from elemental ratios. The nss-Ca contribution was observed as 98% suggesting their crustal origin whereas nss-Mg and nss-K show their contribution as 67%, 54% and 96% and 69% respectively indicating the influence of soil sources. The nss-SO 4 2− 77.4% and 84.7% and NO 3 − more than 98% at both sites suggested the effects by anthropogenic sources mainly comprising industrial, vehicular, fossil fuel combustion, agricultural and residential activities.