Abstract
Abstract. This study investigates the fine particulate matter (PM2.5) variability in the Klang Valley urban-industrial environment. In total, 94 daily PM2.5 samples were collected during a 1-year campaign from August 2011 to July 2012. This is the first paper on PM2.5 mass, chemical composition and sources in the tropical environment of Southeast Asia, covering all four seasons (distinguished by the wind flow patterns) including haze events. The samples were analysed for various inorganic components and black carbon (BC). The chemical compositions were statistically analysed and the temporal aerosol pattern (seasonal) was characterised using descriptive analysis, correlation matrices, enrichment factor (EF), stoichiometric analysis and chemical mass closure (CMC). For source apportionment purposes, a combination of positive matrix factorisation (PMF) and multi-linear regression (MLR) was employed. Further, meteorological–gaseous parameters were incorporated into each analysis for improved assessment. In addition, secondary data of total suspended particulate (TSP) and coarse particulate matter (PM10) sampled at the same location and time with this study (collected by Malaysian Meteorological Department) were used for PM ratio assessment. The results showed that PM2.5 mass averaged at 28 ± 18 µg m−3, 2.8-fold higher than the World Health Organisation (WHO) annual guideline. On a daily basis, the PM2.5 mass ranged between 6 and 118 µg m−3 with the daily WHO guideline exceeded 43 % of the time. The north-east (NE) monsoon was the only season with less than 50 % sample exceedance of the daily WHO guideline. On an annual scale, PM2.5 mass correlated positively with temperature (T) and wind speed (WS) but negatively with relative humidity (RH). With the exception of NOx, the gases analysed (CO, NO2, NO and SO2) were found to significantly influence the PM2.5 mass. Seasonal variability unexpectedly showed that rainfall, WS and wind direction (WD) did not significantly correlate with PM2.5 mass. Further analysis on the PM2.5 ∕ PM10, PM2.5 ∕ TSP and PM10 ∕ TSP ratios reveal that meteorological parameters only greatly influenced the coarse particles (particles with an aerodynamic diameter of greater than 2.5 µm) and less so the fine particles at the site. Chemical composition showed that both primary and secondary pollutants of PM2.5 are equally important, albeit with seasonal variability. The CMC components identified were in the decreasing order of (mass contribution) BC > secondary inorganic aerosols (SIA) > dust > trace elements > sea salt > K+. The EF analysis distinguished two groups of trace elements: those with anthropogenic sources (Pb, Se, Zn, Cd, As, Bi, Ba, Cu, Rb, V and Ni) and those with a crustal source (Sr, Mn, Co and Li). The five identified factors resulting from PMF 5.0 were (1) combustion of engine oil, (2) mineral dust, (3) mixed SIA and biomass burning, (4) mixed traffic and industrial and (5) sea salt. Each of these sources had an annual mean contribution of 17, 14, 42, 10 and 17 % respectively. The dominance of each identified source largely varied with changing season and a few factors were in agreement with the CMC, EF and stoichiometric analysis, accordingly. In relation to meteorological–gaseous parameters, PM2.5 sources were influenced by different parameters during different seasons. In addition, two air pollution episodes (HAZE) revealed the influence of local and/or regional sources. Overall, our study clearly suggests that the chemical constituents and sources of PM2.5 were greatly influenced and characterised by meteorological and gaseous parameters which vary greatly with season.
Highlights
PM2.5 mass ranged between 6 and 118 μg m−3, with 43 % of the samples exceed the 25 μg m−3 daily PM2.5 guideline set by the World Health Organisation (WHO) (2006) and 21 % sample exceedance of the 35 μg m−3 standard of 24 h PM2.5 United States Environmental Protection Agency (US EPA) National Ambient Air Quality Standards (NAAQS) (USEPA, 2015)
Friday recorded the highest average value of PM2.5 mass at 33 μg m−3, while the lowest was on Wednesday (24 μg m−3)
The 8.6 % mass percentage of trace elements determined in this Petaling Jaya urbanindustrial site is lower than the 14 % trace element recorded at Kuala Lumpur city (Rahman et al, 2011) but higher compared to Kuala Terengganu (Tahir et al, 2013b)
Summary
Airborne particulate matter (PM) significantly impacts global climate (Jacobson, 2002; Vieno et al, 2014; Mallet et al, 2016), causing visibility degradation in both urban and less polluted environments (Diederen et al, 1985; Doyle and Dorling, 2002; Watson, 2002; Chang et al, 2009; Hyslop, 2009) and accelerates material decay (Grossi and Brimblecombe, 2002). Fuzzi et al (2015) revealed that climate– aerosol interaction, as well as effects of PM on human health and the environment, were underpinned by many new processes and development in the science. Balasubramanian et al (2003) reported that Singapore PM2.5 mass temporal variability was influenced by a number of factors including changes in emission strength, WD and other meteorological parameters A study by Zhang et al (2013) has successfully discussed the seasonal perspective of PM2.5 sources (soil dust, coal combustion, biomass burning, traffic and waste incineration emissions, industrial pollution, secondary inorganic aerosol) in Beijing, China, using PMF on inorganic and organic data sets. Santoso et al (2008) used inorganic and BC data sets to identify five major sources of PM2.5 as biomass burning, soil, two stroke engine emissions, sea salt, secondary sulfate, motor vehicle emissions and road dust.
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