Spatial distribution and temporal trends of VOCs in a highly industrialized town in Turkey

Effect of Particle Size and Crystal Surface of CeO2 on the Catalytic Combustion of Benzene

In this study, three kinds of CeO₂ were synthesized, and supported PdO_x (x = 0,1) catalysts were prepared for benzene catalytic combustion. The samples were characterized by XRD, N₂ adsorption/desorption, HRTEM, XPS and H₂-TPR. The results show that three kinds of CeO₂ with different structures can be formed by different preparation methods. This is mainly reflected in the differences in pore structure, particle size and crystal plane. CeO₂-DC obtained from directly calcined Ce(NO₃)₃·6H₂O had the largest pore volume and pore diameter and smallest particle size. CeO₂-DC was mainly exposed to the (200) plane. Combined with the results of the ability test, it could be concluded that when Pd²⁺ and Pd⁰ exist at the same time, the activity increases with an increase in the proportion of Pd²⁺. Meanwhile, the structure of CeO₂ affects the formation of oxygen vacancies, thereby affecting the adsorption and degradation of benzene. This article reveals that the particle size, crystal planes, oxygen vacancies and proportion of Pd²⁺ have a great impact on the catalytic combustion of benzene and allow a more comprehensive understanding of the structure–activity relationship, which can guide us to design high-efficiency catalysts targeted to obtain suitable CeO₂-based catalysts for the catalytic combustion of benzene.

Levels, characteristics and health risk assessment of VOCs in different functional zones of Hefei

In order to study the characteristics and health risk of VOCs in the ambient air in the typical developing cities in China, the research was conducted in five functional zones in Hefei from September 2016 to January 2017. The average concentrations of total measured VOCs in traffic zone was the largest (85.94 μg m^-3), followed by industrial zone (64.84 μg m^-3), development zone (58.92 μg m^-3), resident zone (57.31 μg m^-3), and background zone (54.94 μg m^-3). Cl-VOCs were most abundant species in chlorinated VOCs (85.06%), which showed much higher level in industrial zone. the mean value of BTEX found in presented study was 65.19 μg m^-3. Based on the specific VOC ratio method (B/T), the observed sites were greatly affected by the traffic emissions. The ratios of T/B, E/B and X/B were 1.15, 1.35 and 0.47, respectively, possibly due to the aging air mass. Carcinogenic risks for benzene, carbon tetrachloride, trichloroethylene, 1, 2-dichloroethane and chloroform were higher than the general acceptable risk level of 1.00 × 10^-6. Potential non-carcinogenic risk assessment showed that hazard quotient (HQ) of 10 VOCs not exceeded unity, but the hazard risk index (HI) at site ED, LY, YH and HD were both higher than 1.

A toxicological and genotoxicological indexing study of ambient aerosols (PM2.5-10) using in vitro bioassays

This study evaluates the toxicity and genotoxicity levels of atmospheric particulate matter (PM) samples collected at several locations of a megacity (Istanbul, Turkey) with different urban and industrial characteristics. The ambient air samples, in the form of a coarse fraction of inhalable particulates, PM_2.5-10, were collected on Teflon filters using a passive sampling method on a monthly basis during a one-year period. Later, they were extracted into both the lipophilic and hydrophilic phases using dimethyl sulfoxide (DMSO) and ultra-pure water, respectively. The obtained aqueous extracts were tested for acute toxicity and genotoxicity using the photo-luminescent bacterium Vibrio fischeri Microtox^® and SOS Chromotest^® assays, respectively. Statistically significant differences greater than background levels were obtained in both measurements, indicating the presence of toxic substances absorbed on particulate matter. The PM_2.5-10 extracts identified significant seasonal and locational differences in the toxicity and genotoxicity levels. Local anthropogenic activities and factors were associated with the quantified higher levels. Finally, a qualitative inner comparison study of regional toxicity and genotoxicity indexes was suggested to provide a clearer picture of the pollution and risk levels (or occurrences) in the Istanbul urban area. In this indexing study, the threshold levels for the urban background and episodic occurrences of the toxicity and genotoxicity levels in PM_2.5-10 samples were identified to be 1.11 TU (Toxicity Unit) and 8.73 TU and 0.72 IF (Induction Factor) and 1.38 IF, respectively.