Composition of Trinidad rainfall

The rainwater collected from daily rainfalls at six rainfall stations in Trinidad over a 1‐year period was analyzed for NH4+, NO3−, urea‐N, Mg2+, Ca2+, Na+, K+, Cl−, and SO42− concentrations. The concentration of these constituents varied from 0.41 to 1.13, 0.41 to 1.24, 0.15 to 0.50, 0.33 to 0.99, 1.88 to 4.52, 1.92 to 2.57, 1.21 to 3.27, 2.10 to 3.93, and 1.89 to 17.75 mg/1 of NH4‐N, NO3‐N, urea‐N, Mg2+, Ca2+, Na+, K+, Cl−, and SO42−, respectively. Considerable amounts of these constituents were added to the soil through rainfall. Major proportions of NH4+ and NO3− and some proportions of SO42− in rainwater may have been derived from gaseous sources, probably originating from soil. Urea‐N seems to have originated as particulate matter from soil organic matter and microbial cell debris. Greater proportions of Ca2+ and K+, and smaller proportions of Mg2+ and SO42− appear to have been derived from terrestrial dust. Sodium, Cl−, Mg2+ and partly Ca2+, K+ and SO42 were derived from marine sources. Thus it appears that the sources of various constituents in the Trinidad rainfall are quite varied.