AIR-POLLUTION IN SINGAPORE - ITS MULTIELEMENTAL ASPECT AS MEASURED BYNUCLEAR ANALYTICAL TECHNIQUES

Aerosol samples were collected in 1994 in Singapore on two occasions: once in June during the normal meteorological conditions and later in October during a long haze period caused by the heavy forest fire in I ndonesia, Filtration and impaction collection methods were used simult aneously so that detailed elemental analysis of bulk as well as of dif ferent size fractions could be performed. Accelerator based nuclear an alytical techniques such as Particle Induced X-Ray Emission (PIXE), Ru therford Backscattering (RES) and Nuclear Microscopy (NM) were used fo r analysis. These techniques are fast, truly multielemental and perfec tly suited for routine analysis of a large number of aerosol samples. Typically all samples were analysed for the following 24 elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Mn, Cr, Fe, Co, Ni, Cu, Zn, Ga, A s, Br, Rb, Sr and Pb. Detection limits for bulk analysis were generall y below ng/m(3) and for single particle analysis absolute detectable m ass was approximately 10(-17) g. Additionally, trace elements such as Cd, Sn, Sb and Pa whose characteristic X-ray lines were normally ''obs cured'' by the lines of other more abundant elements, were detected wh en analysing by nuclear microscope in single particle mode. Judging by the average concentrations of lead and sulphur which are good indicat ors of industrial component of air pollution the situation in Singapor e is satisfactory. Pb was typically found in concentrations of 5 to 50 ng/m(3) and sulphur in concentrations of 1 to 2 mu g/m(3). These conc entrations are well below limits set by the World Health Organisation (1500 ng/m(3) and 40 mu g/m(3), respectively). On the other hand durin g the haze period the average concentrations of elements like S, K, Ti , V, Mn, Ni, As and Pb were found to be 3 to 6 times higher than usual . Results are presented and discussed.