The Air Quality Influences of Vehicular Traffic Emissions

The number of automobiles has been steadily increasing in cities as a consequence of rapid urbanization and economic growth. It has been widely reported that vehicular emissions are strongly correlated with the level of urban air pollution. The major primary air pollutants that are linked to direct emissions from on‐road vehicles include soot (black carbon), carbon monoxide (CO), and nitric oxide (NO). Human exposure to these air pollutants is of health concern. Therefore, it is important to investigate air pollutants of traffic origin (e.g., BC, CO, and NO) in ambient air at different locations of cities and to assess the effects of vehicles on the urban air quality. With this goal in mind, we carried a systematic study in Singapore (the fourth most densely populated country in the world) with concurrent measurements of BC, NO, and CO in ambient air at four different locations having variations in traffic flows and meteorology. We then assessed the relationship between traffic flows and prevailing levels of the three air pollutants, and studied the association of these air pollutants among each other and with diverse meteorological conditions. The major outcomes of the study are discussed

Influence of Biomass Burning on Temporal and Diurnal Variations of Acidic Gases, Particulate Nitrate, and Sulfate in a Tropical Urban Atmosphere

The present study investigated the temporal and diurnal distributions of atmospheric acidic gases (sulphur dioxide (SO2), nitrous acid (HONO), and nitric acid (HNO3)) and those of particulate nitrate (NO3-) and sulfate (SO42-) through a comprehensive field campaign during the largest smoke haze episode in Singapore, a representative country in Southeast Asia (SEA). To identify the atmospheric behavior of these pollutants during the smoke haze period, the data generated from the measurement campaign were divided into three distinct periods: prehaze, during haze, and posthaze periods. The 24 hr average data indicated that ambient SO2, HONO, and HNO3 during the smoke haze episodes increased by a factor ranging from 1.2 to 2.6 compared to those during the prehaze and posthaze periods. Similarly, in the case of particulates SO42- and NO3-, the factor ranged from 2.3 to 4.2. Backward air trajectories were constructed and used to find the sources of biomass burning to the recurring smoke haze in this region. The air trajectory analysis showed that the smoke haze episodes experienced in Singapore were influenced by transboundary air pollution, caused by severe biomass burning events in the islands of Indonesia

A comparative study of Mn/Co binary metal catalysts supported on two commercial diatomaceous earths for oxidation of benzene

Two commercial diatomaceous earths were used as supports for the preparation of Mn/Cobinary metal catalysts at different metal loads (5 to 10 wt % Mn and 5 to 15 wt % Co) by incipientwetness deposition. The activity of the prepared catalysts towards the complete oxidation of benzeneto CO2and water was investigated between 100 and 400◦C. Raw supports and synthesized catalystswere characterized by XRD, N2physisorption, SEM-EDS, H2-TPR, and TPD. The purificationtreatment of food-grade diatomite significantly affected the crystallinity of this support whilereducing its specific surface area (SSA). A loss of SSA, associated with the increase in the metalload, was observed on samples prepared on natural diatomite, while the opposite trend occurredwith food-grade diatomite-supported catalysts. Metal nanoparticles of around 50 nm diameter wereobserved on the catalysts’ surface by SEM analysis. EDS analysis confirmed the uniform depositionof the active phases on the support’s surface. A larger H2consumption was found by TPR analysisof natural diatomite-based samples in comparison to those prepared at the same metal load onfood-grade diatomite. During the catalytic oxidation experiment, over 90% conversion of benzenewere achieved at a reaction temperature of 225◦C by all of the prepared samples. In addition, theformation of coke during the oxidation tests was demonstrated by TGA analysis and the solublefraction of the produced coke was characterized by GC-MS

Temporal and spatial variation in major ion chemistry and source identification of secondary inorganic aerosols in Northern Zhejiang Province, China

To investigate the seasonal and spatial variations of ion chemistry of fine particles in Northern Zhejiang Province (NZP), China, one year-long field sampling was conducted at four representative sites (two urban, one suburb, and one rural sites) in both cities of Hangzhou and Ningbo from December 2014 to November 2015. Twelve water soluble inorganic ions (WSII) were characterized in this comprehensive study. The annual average of PM2.5 concentration in NZP as overall was 66.2 ± 37.7 μg m−3, and urban sites in NZP were observed with more severe PM2.5 pollution than the suburban and rural sites. The annual average concentration of total WSII at four sampling sites in NZP was 29.1 ± 19.9 μg m−3, dominated by SO42− (10.3 μg m−3), and followed by NO3− (8.9 μg m−3), NH4+ (6.6 μg m−3), Cl− (1.3 μg m−3) and K+ (0.7 μg m−3). Among all cations, NH4+ was the predominant neutralizing ion with the highest neutralization factor (NF), while the remaining cations showed limited neutralization capacity. The highest and lowest sulfur oxidation ratio (SOR) values in this region were found in summer and winter, respectively; while the seasonal patterns for nitrogen oxidation ratio (NOR) were opposite to that of SOR. Principal component analysis (PCA) showed that the significant sources of WSII in NZP were industrial emissions, biomass burning, and formation of secondary inorganic aerosols. In addition, contribution from transboundary transport of polluted aerosols was also confirmed from the assessment through air mass backward trajectory analysis

2013 Southeast Asian Smoke Haze: Fractionation of Particulate-Bound Elements and Associated Health Risk

Recurring biomass burning-induced smoke haze is a serious regional air pollution problem in Southeast Asia (SEA). The June 2013 haze episode was one of the worst air pollution events in SEA. Size segregated particulate samples (2.5–1.0 μm; 1.0–0.5 μm; 0.5– 0.2 μm; and <0.2 μm) were collected during the June 2013 haze episode. PM_2.5 concentrations were elevated (up to 329 μg/m³) during the haze episode, compared to those during the nonhaze period (11–21 μg/m³). Chemical fractionation of particulate-bound trace elements (B, Ca, K, Fe, Al, Ni, Zn, Mg, Se, Cu, Cr, As, Mn, Pb, Co, and Cd) was done using sequential extraction procedures. There was a 10-fold increase in the concentration of K, an inorganic tracer of biomass burning. A major fraction (>60%) of the elements was present in oxidizable and residual fractions while the bioavailable (exchangeable) fraction accounted for up to 20% for most of the elements except K and Mn. Deposition of inhaled potentially toxic trace elements in various regions of the human respiratory system was estimated using a Multiple-Path Particle Dosimetry model. The particle depositions in the respiratory system tend to be more severe during hazy days than those during nonhazy days. A prolonged exposure to finer particles can thus cause adverse health outcomes during hazy days. Health risk estimates revealed that the excessive lifetime carcinogenic risk to individuals exposed to biomass burning-impacted aerosols (18 ± 1 × 10^–6) increased significantly (<i>P</i> < 0.05) compared to those who exposed to urban air (12 ± 2 × 10^–6)