Rainfall patterns and its chemical characteristics in Singapore

• Main Author: Sam, Choy Ha.
• Other Authors: Chang Wei-Chung
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Civil engineering::Water resources
• Online Access: http://hdl.handle.net/10356/16060
• Institution: Nanyang Technological University

A total of 41 wet precipitation samples were collected in Nanyang Technological University,from December 2008 to March 2009, which is also the Northeast monsoon season of Singapore. Each sample was analyzed by Ion Chromatography (IC) test for major anions (Cl−, NO3 −,SO42−, F-)and Inductively Coupled Plasma(ICP)test for major cations (Na+, K+, Ca2+ and Mg2+,Zn2+ and Fe2+). The relative magnitude of scavenged mass by the precipitation followed the pattern Ca2+ > NO3- >K+ > Na+ > F- > Fe2+ > Zn2+. Ion Sulfate demonstrated highest mass contribution(27.4%) followed by ion Chloride(17.6%), ion Calcium(16.1%) etc. However, in term of ionic concentration, Ca2+ was found to have highest concentration 189.14 9eq/l(27.89%) among cations while Cl- exhibits the highest value among anions(16.83%). The statistical analysis had showed high correlation of Ca2+, K+ and Na+ with Cl- (the combination of sea-salt) are 0.77, 0.44 and 0.60 respectively, while SO4 2- correlates with Cl- with the value of 0.62. However, by assuming NaCl is 100% originated from marine origin,further analysis had shown the % of sea salt fraction for Ca2+, K+,and SO4 2- are ranged from 4% to 27.34% only, which suggested majority of these ions are more likely to associate with the soil dust, automobile emission and the inland human activities due to the prevailing wind direction during North East Monsoon. For acidity, SO42- was found to be dominant over NO3- by contributing an average of 59.6% acidity to the precipitation. The non sea-salt fraction of SO42- was found to be 72.66%, suggesting the major emission sources are from anthropogenic activities. This report is aiming to investigate the chemical composition of rainwater in Singapore to gain understanding on the atmospheric pollutants. Good understanding of wet deposition can assist in identifying the abundant air pollutants and thus allow regulatory body to set related rules on restricting the anthropogenic activities.