Distribution, sources and potential health risks of polycyclic aromatic hydrocarbons (PAHs) in PM2.5 collected during different monsoon seasons and haze episode in Kuala Lumpur.

This study aimed to determine the distribution and potential health risks of polycyclic aromatic hydrocarbons (PAHs) in PM2.5 collected in Kuala Lumpur during different monsoon seasons. The potential sources of PM2.5 were investigated using 16 priority PAHs with additional of biomass tracers namely levoglucosan (LV), mannosan (MN) and galactosan (GL). This study also investigated the cytotoxic potential of the extracted PAHs towards V79-4 cells. A high-volume air sampler (HVS) was used to collect PM2.5 samples for 24 h. PAHs were extracted using dichloromethane (DCM) while biomass tracers were extracted by a mixture of DCM/methanol (3:1) before analysis with gas chromatography-mass spectrometry (GC-MS). The cytotoxicity of the PAHs extract was determined by assessing the cell viability through the reduction of tetrazolium salts (MTT). The results showed that the total mean ±â€¯SD concentrations of PAHs during the southwest (SW) and northeast (NE) monsoons were 2.51 ±â€¯0.93 ng m-3 and 1.37 ±â€¯0.09 ng m-3, respectively. Positive matrix factorization (PMF) using PAH and biomass tracer concentrations suggested four potential sources of PM2.5; gasoline emissions (29.1%), natural gas and coal burning (28.3%), biomass burning (22.3%), and diesel and heavy oil combustion (20.3%). Health risk assessment showed insignificant incremental lifetime cancer risk (ILCR) of 2.40E-07 for 70 years of exposure. MTT assay suggested that PAHs extracts collected during SW monsoon have cytotoxic effect towards V79-4 cell at the concentrations of 25 µg mL-1, 50 µg mL-1, 100 µg mL-1 whereas non-cytotoxic effect was observed on the PAHs sample collected during NE monsoon.

Surfactants in the sea surface microlayer, subsurface water and fine marine aerosols in different background coastal areas.

This study aims to determine the concentrations of surfactants in the surface microlayer (SML), subsurface water (SSW) and fine mode aerosol (diameter size < 1.5 µm) at different coastal stations in Peninsular Malaysia. The concentrations of anionic and cationic surfactants were determined through colorimetric methods as methylene blue active substances (MBAS) and disulphine blue active substances (DBAS), respectively. Water-soluble ions, for the determination of fine mode aerosol sources, were determined using ion chromatography (IC) for anions (SO42-, NO3-, Cl- and F-) and cations (Na+, K+, Ca2+ and Mg2+). Principal component analysis (PCA), combined with multiple linear regression (MLR), was used to identify the possible sources of surfactants in fine aerosol. The results showed the concentrations of surfactants as MBAS and DBAS in the SML ranged between 0.23 ± 0.03 and 0.35 ± 0.01 µmol L-1 and between 0.21 ± 0.02 and 0.29 ± 0.01 µmol L-1, respectively. The enrichment factors (Efs) ratios between MBAS and DBAS in the SML and SSW ranged between 1.04 ± 0.01 and 1.32 ± 0.04, respectively. The station that is located near to tourism and industrial activities recorded the highest concentrations of surfactants in SML and SSW. The concentrations of surfactants in fine aerosol ranged between 62.29 and 106.57 pmol m-3. The three possible sources of fine aerosol during the northeast monsoon were aged sea spray/biomass burning (which accounted for 69% of the atmospheric aerosol), nitrate/mineral dust (23%) and sulphate/fresh sea salt (8%). During the southwest monsoon, the three main sources of atmospheric aerosol were biomass burning (71%), secondary inorganic aerosol (23%) and sea spray (6%). This study suggests anthropogenic sources are main contributors to the concentrations of surfactants in SML, SSW and fine aerosols.

Source apportionment and health risk assessment among specific age groups during haze and non-haze episodes in Kuala Lumpur, Malaysia.

This study aims to determine PM2.5 concentrations and their composition during haze and non-haze episodes in Kuala Lumpur. In order to investigate the origin of the measured air masses, the Numerical Atmospheric-dispersion Modelling Environment (NAME) and Global Fire Assimilation System (GFAS) were applied. Source apportionment of PM2.5 was determined using Positive Matrix Factorization (PMF). The carcinogenic and non-carcinogenic health risks were estimated using the United State Environmental Protection Agency (USEPA) method. PM2.5 samples were collected from the centre of the city using a high-volume air sampler (HVS). The results showed that the mean PM2.5 concentrations collected during pre-haze, haze and post-haze periods were 24.5±12.0µgm-3, 72.3±38.0µgm-3 and 14.3±3.58µgm-3, respectively. The highest concentration of PM2.5 during haze episode was five times higher than World Health Organisation (WHO) guidelines. Inorganic compositions of PM2.5, including trace elements and water soluble ions were determined using inductively coupled plasma-mass spectrometry (ICP-MS) and ion chromatography (IC), respectively. The major trace elements identified were K, Al, Ca, Mg and Fe which accounted for approximately 93%, 91% and 92% of the overall metals' portions recorded during pre-haze, haze and post-haze periods, respectively. For water-soluble ions, secondary inorganic aerosols (SO42-, NO3- and NH4+) contributed around 12%, 43% and 16% of the overall PM2.5 mass during pre-haze, haze and post-haze periods, respectively. During haze periods, the predominant source identified using PMF was secondary inorganic aerosol (SIA) and biomass burning where the NAME simulations indicate the importance of fires in Sumatra, Indonesia. The main source during pre-haze and post-haze were mix SIA and road dust as well as mineral dust, respectively. The highest non-carcinogenic health risk during haze episode was estimated among the infant group (HI=1.06) while the highest carcinogenic health risk was estimated among the adult group (2.27×10-5).