In this study, we show that black carbon (BC) mass concentrations measured by different techniques are consistent and traceable. First, we present the volatilities of 13 organic compounds passed through a heated inlet. These data were used to quantify the interference of organic aerosols on the BC measurement techniques. The masses of the refractory particles that incandesce (m * ref ) were used to calibrate BC mass measured by a single-particle soot photometer (SP2), which uses laser-induced incandescence. This calibration was influenced little by refractory organics and agreed well with that of fullerene soot, which indicates the consistency of the standards. We estimated the interference of pyrolyzed refractory organics on the BC measured with a filter-based absorption photometer continuous soot monitoring system (COSMOS) with a heated inlet to be small in Asia. This was also confirmed by the stable mass absorption cross section (MAC) obtained by the high correlations between BC mass concentrations measured by COSMOS (M COSMOS ) and those measured by the thermal-optical transmittance method (M TOT ) (Kondo et al. 2009). M COSMOS was also compared with total BC mass concentrations measured with an SP2 (M SP2 ) in Tokyo in 2009. M COSMOS and M SP2 were highly correlated (r 2 = 0.97) and agreed to within about 10% on average. These results demonstrate that M SP2 , M COSMOS , and M TOT were nearly identical. Use of the masses of incandescing refractory BC
The health implications of PM 2.5 in the tropical region of Southeast Asia (SEA) are significant as PM 2.5 can pose serious health concerns. PM 2.5 concentration and sources here are strongly influenced by changes in the monsoon regime from the south-west quadrant to the north-east quadrant in the region. In this work, PM 2.5 samples were collected at a semi-urban area using a high-volume air sampler at different seasons on 24 h basis. Analysis of trace elements and water-soluble ions was performed using inductively coupled plasma mass spectroscopy (ICP-MS) and ion chromatography (IC), respectively. Apportionment analysis of PM 2.5 was carried out using the United States Environmental Protection Agency (US EPA) positive matrix factorization (PMF) 5.0 and a mass closure model. We quantitatively characterized the health risks posed to human populations through the inhalation of selected heavy metals in PM 2.5 . 48 % of the samples collected exceeded the World Health Organization (WHO) 24 h PM 2.5 guideline but only 19 % of the samples exceeded 24 h US EPA National Ambient Air Quality Standard (NAAQS). The PM 2.5 concentration was slightly higher during the north-east monsoon compared to south-west monsoon. The main trace metals identified were As, Pb, Cd, Ni, Mn, V, and Cr while the main ions were SO 2− 4 , NO − 3 , NH + 4 , and Na. The mass closure model identified four major sources of PM 2.5 that account for 55 % of total mass balance. The four sources are mineral matter (MIN) (35 %), secondary inorganic aerosol (SIA) (11 %), sea salt (SS) (7 %), and trace elements (TE) (2 %). PMF 5.0 elucidated five potential sources: motor vehicle emissions coupled with biomass burning (31 %) were the most dominant, followed by marine/sulfate aerosol (20 %), coal burning (19 %), nitrate aerosol (17 %), and mineral/road dust (13 %). The hazard quotient (HQ) for four selected metals (Pb, As, Cd, and Ni) in PM 2.5 mass was highest in PM 2.5 mass from the coal burning source and least in PM 2.5 mass originating from the mineral/road dust source. The main carcinogenic heavy metal of concern to health at the current location was As; the other heavy metals (Ni, Pb, and Cd) did not pose a significant cancer risk in PM 2.5 mass concentration. Overall, the associated lifetime cancer risk posed by the exposure of hazardous metals in PM 2.5 is 3-4 per 1 000 000 people at this location. Published by CopernicusPublications on behalf of the European Geosciences Union. 598 M. F. Khan et al.: Fine particulate matter in the tropical environment Atmos. Chem. Phys., 16, 597-617, 2016 www.atmos-chem-phys.net/16/597/2016/
Haze is a common phenomenon afflicting Southeast Asia (SEA), including Malaysia, and has occurred almost every year within the last few decades. Haze is associated with high level of air pollutants; it reduces visibility and affects human health in the affected SEA countries. This manuscript aims to review the potential origin, chemical compositions, impacts and mitigation strategies of haze in Malaysia. "Slash and burn" agricultural activities, deforestation and oil palm plantations on peat areas, particularly in Sumatra and Kalimantan, Indonesia were identified as the contributing factors to high intensity combustions that results in transboundary haze in Malaysia. During the southwest monsoon (June to September), the equatorial SEA region experiences a dry season and thus an elevated number of fire events. The prevailing southerly and south-westerly winds allow the cross-boundary transportation of pollutants from the burning areas in Sumatra and Kalimantan in Indonesia, to Peninsular Malaysia and Malaysian Borneo, respectively. The dry periods caused by the El Niño-Southern Oscillation (ENSO) prolong the duration of poor air quality. The size range of particulate matter (PM) in haze samples indicates that haze is dominated by fine particles. Secondary inorganic aerosols (SIA, such as SO42-and NH4+) and organic substances (such as levoglucosan, LG) were the main composition of PM during haze episodes. Local vehicular emissions and industrial activities also contribute to the amount of pollutants and can introduce toxic material such as polyaromatic hydrocarbons (PAHs). Haze episodes have contributed to increasing hospital visits for treatments related to chronic obstructive pulmonary diseases, upper respiratory infections, asthma and rhinitis. Respiratory mortality increased 19% due to haze episodes. Children and senior citizens are more likely to suffer the health impacts of haze. The inpatient cost alone from haze episodes was estimated at around USD 91,000 per year in Malaysia. Almost all economic sectors also experienced losses, with the heaviest losses in the agriculture and tourism sectors. This review suggests several ways forward to reduce haze episodes in SEA and Malaysia. These include economic approaches, research collaborations and science-policy interface. Improving forecasting capabilities can help reduce response time to burning events and subsequently reduce its impacts. Lastly, commitment and involvement by individuals, government agencies, and the entrepreneurial private sectors are crucial to reduce biomass burning (BB) and haze episodes in SEA.
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