COMPOSITION OF SURFACTANTS AND IONIC ELEMENTS FROM DIESEL AND PETROL EXHAUST PARTICULATE MATTER
Emission from vehicular exhaust is an important source of particulate matter (PM) especially in the urban area. This study was conducted to determine the compositions of surfactants and ionic elements from diesel and petrol exhaust particulate matter (exhaust soot). The exhaust PM sample was collected using soft paint brush from different types of petrol and diesel motor vehicles, during dry days. Methylene Blue Active Substances (MBAS) which are anionic surfactant and Disulphine Blue Active Substances (DBAS) which are cationic surfactant were determined using UV-Vis Spectrophotometer, based on colorimetric method. Whereas, ion chromatography (IC) was used to determine ionic elements from the exhaust PM samples. In addition, the Field Emission Scanning Electron Microscope (FESEM) was used to study the morphological structure of exhaust PM. Results indicated that the concentration of surfactants were dominated by MBAS compared to DBAS for all types of motor vehicles studied. In addition, heavy duty vehicles/ lorries showed the highest concentration of MBAS (1.50 ± 0.10 µmol g-1) and DBAS (0.28 ± 0.04 µmol g-1). The ionic elements compositions followed the trend of SO42- > Ca2+ > Na+ > K+ > NO3- > Cl- > NH4+ > Mg2+ > F- for all types of soot samples. Exhaust PM from petrol and diesel automobiles appear as agglomerates of many fine spherical primary particles in the form of cluster soot particles, according to FESEM image. The emission from diesel and petrol vehicles should be a concern as they could pose negative effects to human health as well as towards environment.