RAINFALL CHEMISTRY AND NUTRIENT LOADING IN A PENINSULAR MALAYSIA FOREST SITE

Abstract

Rainwater collected at the Berembun Experimental Basin, Peninsular Malaysia, was analysed for its chemistry and nutrient loading. The annual weighted mean concentrations of the constituents were as follows (mg l^-1): K⁺-0.34, Ca²⁺-2.64, Na⁺-0.20, Mg²⁺- 0.94, Cl^- - 1.64, SO^2-₄ - 0.31, PO^3-₄ - 0.02, NO₃-N - 0.08, NH₄-N - 0.07, total-N - 0.54 and alkalinity -9.11. The pH was 5.98. Solutes in the rainfall were mostly supplied by terrestrial sources on the basis that the ratios of SO^2-₄ /Na⁺, Cl^-/Na⁺ and Mg²⁺/Na⁺ were 1.52, 8.06, and 4.62, respectively and generally much higher than the corresponding ratios in seaspray. Concentrations of Ca²⁺ and Mg²⁺ were very high and could be related to sample contamination by local dust. Similarly levels of Cl were far in excess to that of Na⁺ concentrations. Storm basis as well as monthly solute loads were significantly correlated with rainfall depth for Ca²⁺, Mg²⁺, Cl^-, PO^3-₄ , NO₃-N, NH₄-N and total-N. Annual solute loads were comparable to those obtained from other tropical areas except for Ca²⁺ and Mg²⁺ which were extremely high.