Characteristics of the stable isotopes ( 18O and D) composition in precipitation from Bangkok, KamPhaeng-Phet and Suphanburi, Thailand

Abstract

The stable isotopic (d¹⁸O and dD) and water chemical compositions of the precipitation collected from Bangkok (BKK), Kamphaeng-Phet (KPP) and Suphanburi (SPB) in 2015 were performed. All water samples were weakly alkaline and the major ion (Cl^-, SO₄^-2, Na⁺¹, K⁺) were the same magnitude with low values. The results of isotopic measurements for BKK, KPP, and SPB shown a wide magnitude of variations ranging between -12.22 to 0.51 , -11.78 to 5.45 and -15.50 to 0.73, in d¹⁸O (‰)  and between -114.49 to 1.43, -86.41 to 27.29, and -81.74 to 2.79, in dD (‰), respectively. Both d¹⁸O and dD decreased significantly from BKK to SPB and KPP and from cold to warm season because of the evaporation-induced isotopic enrichments. The results of this study revealed the exact relationship between d¹⁸O and dD of precipitation changes from geographical region to region which depending on local climatic conditions. The average annual rainfall of d¹⁸O and dD for BKK, KPP and SPB were indicated the same derived source of precipitations. These isotopic data provide important baseline information of the regional characteristics of d¹⁸O and dD of meteoric water including produce maps of mean annual isotopic values of precipitation in the country.