SPATIAL TRENDS OF NITRATE LEVEL AND NITRATE STABLE ISOTOPES IN THE LINGGI RIVER

Abstract

Determining the isotopic composition of nitrate (δ15N-NO3- and δ18O-NO3-) in water can provide useful information to identify the sources of nitrate pollution and understand its dynamic behaviour in the aquatic ecosystem. In this study, six river water samples from the Linggi River, Malaysia were obtained to determine the nitrate level and understand possible sources of nitrate pollution using nitrate stable isotopes. The nitrate level and nitrate stable isotopes were measured using ion chromatography (IC) and Continuous Flow Elemental Analyzer Isotope Ratio Mass Spectrometer (CF-EA-IRMS) respectively. The nitrate in the river water samples ranged between 0.97± 0.01 mg L-1 and 36.08 ± 0.12 mg L-1. The nitrate level in all river water stations was below than World Health Organization (WHO) and Malaysian Raw Drinking Water guideline level. For nitrate stable isotopes the δ15N-NO3- values ranged from +1.4‰ to +15.6‰ and the δ18O-NO3- values ranged from +13.8‰ to +27.4‰ in the river water samples. Based on the cross plot of nitrate stable isotopes, the Linggi River were influenced by the mixture of nitrate pollution sources process from ammonia in fertilizer, soil ammonia, sewage, manure, nitrate fertilizer and atmospheric nitrate. This study reports the signature of nitrate stable isotopes in potential nitrate pollution sources identificati