Secondary organic aerosol formation from the irradiation of simulated automobile exhaust

Pyrolysis treatment of nonmetal fraction of waste printed circuit boards: Focusing on the fate of bromine

Advanced thermal treatment of electronic waste offers advantages of volume reduction and energy recovery. In this work, the pyrolysis behaviour of nonmetallic fractions of waste printed circuit boards was studied. The fate of a bromine and thermal decomposition pathway of nonmetallic fractions of waste printed circuit boards were further probed. The thermogravimetric analysis showed that the temperatures of maximum mass loss were located at 319°C and 361°C, with mass loss of 29.6% and 50.6%, respectively. The Fourier transform infrared Spectroscopy analysis revealed that the spectra at temperatures of 300°C-400°C were complicated with larger absorbance intensity. The nonmetallic fractions of waste printed circuit boards decomposed drastically and more evolved products were detected in the temperature range of 600°C-1000°C. The gas chromatography-mass spectrometry analysis indicated that various brominated derivates were generated in addition to small molecules, such as CH₄, H₂O and CO. The release intensity of CH₄ and H₂O increased with temperature increasing and reached maximum at 600°C-800°C and 400°C-600°C. More bromoethane (C₂H₅Br) was formed as compared with HBr and methyl bromide (CH₃Br). The release intensity of bromopropane (C₃H₇Br) and bromoacetone (C₃H₅BrO) were comparable, although smaller than that of bromopropene (C₃H₅Br). More dibromophenol (C₆H₄Br₂O) was released than that of bromophenol (C₆H₅BrO) in the thermal treatment. During the thermal process, part of the ether bonds first ruptured forming bisphenol A, propyl alcohol and tetrabromobisphenol A. Then, the tetrabromobisphenol A decomposed into C₆H₅BrO and HBr, which further reacted with small molecules forming brominated derivates. It implied debromination of raw nonmetallic fractions of waste printed circuit boards or pyrolysis products should be applied for its environmentally sound treating.

Comparison between idling and cruising gasoline vehicles in primary emissions and secondary organic aerosol formation during photochemical ageing

Driving conditions are among the important factors determining gasoline vehicle emissions, yet their relation with exhaust-derived secondary pollutants is poorly understood. Here, we introduced exhaust from a gasoline vehicle under hot idling and cruising conditions into an indoor smog chamber by using a chassis dynamometer and investigated the formation of secondary organic aerosols (SOA) during photochemical ageing under light after characterizing the primary emission of non-methane hydrocarbons (NMHCs), nitrogen oxide (NO_x) and primary organic aerosol (POA) in the dark. When compared to emission factors (EFs) at idling, during cruising at 20 km h^-1 or 40 km h^-1, the EFs of NMHCs decreased by more than an order of magnitude, while the EFs of NO_x were more than doubled, resulting in a large drop in the NMHC-to-NO_x ratios. The percentages of reactive alkenes and aromatic hydrocarbons also decreased from idling to cruising at 20 km h^-1 to that at 40 km h^-1. The emission factor of benzene, a carcinogenic compound, decreased more than 10 times from ~0.35 g kg-fuel^-1 at idling to ~0.03 g kg-fuel^-1 during cruising. During photochemical ageing of exhaust, substantial SOA was formed, and the SOA/POA ratios decreased from 52 to 92 at idling to 4-14 during cruising. Traditional aromatics could explain 30-64% of the measured SOA at idling but less than 15% of the measured SOA during cruising. Our results highlight that traffic congestion would greatly promote the emission of reactive volatile organic compounds and carcinogenic benzene from gasoline vehicles and also show that NMHCs as a target in gasoline vehicle emission tests cannot effectively represent the SOA and ozone formation potentials of the partially oxidized hydrocarbons from poorly functioning converters.

Secondary particles formed from the exhaust of vehicles using ethanol-gasoline blends increase the production of pulmonary and cardiac reactive oxygen species and induce pulmonary inflammation

BACKGROUND

Ethanol vehicles release exhaust gases that contribute to the formation of secondary organic aerosols (SOA).

OBJECTIVE

To determine in vivo toxicity resulting from exposure to SOA derived from vehicles using different ethanol-gasoline blends (E0, E10, E22, E85W, E85S, E100).

METHODS

Exhaust emissions from vehicles using ethanol blends were delivered to a photochemical chamber and reacted to produce SOA. The aerosol samples were collected on filters, extracted, and dispersed in an aqueous solutions and intratracheally instilled into Sprague Dawley rats in doses of 700 μg/0.2 ml. After 45 min and 4 h pulmonary and cardiac chemiluminescence (CL) was measured to estimate the amount of reactive oxygen species (ROS) produced in the lungs and heart. Inflammation was measured by differential cell count in bronchoalveolar lavages (BAL).

RESULTS

Statistically and biologically significant differences in response to secondary particles from the different fuel formulations were detected. Compared to the control group, animals exposed to SOA from gasoline (E0) showed a significantly higher average CL in the lungs at 45 min. The highest CL averages in the heart were observed in the groups exposed to SOA from E10 and pure ethanol (E100) at 45 min. BAL of animals exposed to SOA from E0 and E85S had a significant increased number of macrophages at 45 min. BAL neutrophil count was increased in the groups exposed to E85S (45 min) and E0 (4 h). Animals exposed to E0 and E85W had increased BAL lymphocyte count compared to the control and the other exposed groups.

DISCUSSION

Our results suggest that SOA generated by gasoline (E0), followed by ethanol blends E85S and E85W, substantially induce oxidative stress measured by ROS generation and pulmonary inflammation measured by the recruitment of white blood cells in BAL.

Variability in the primary emissions and secondary gas and particle formation from vehicles using bioethanol mixtures

Bioethanol for use in vehicles is becoming a substantial part of global energy infrastructure because it is renewable and some emissions are reduced. Carbon monoxide (CO) emissions and total hydrocarbons (THC) are reduced, but there is still controversy regarding emissions of nitrogen oxides (NO_x), aldehydes, and ethanol; this may be a concern because all these compounds are precursors of ozone and secondary organic aerosol (SOA). The amount of emissions depends on the ethanol content, but it also may depend on the engine quality and ethanol origin. Thus, a photochemical chamber was used to study secondary gas and aerosol formation from two flex-fueled vehicles using different ethanol blends in gasoline. One vehicle and the fuel used were made in the United States, and the others were made in Brazil. Primary emissions of THC, CO, carbon dioxide (CO₂), and nonmethane hydrocarbons (NMHC) from both vehicles decreased as the amount of ethanol in gasoline increased. NO_x emissions in the U.S. and Brazilian cars decreased with ethanol content. However, emissions of THC, CO, and NO_x from the Brazilian car were markedly higher than those from the U.S. car, showing high variability between vehicle technologies. In the Brazilian car, formation of secondary nitrogen dioxide (NO₂) and ozone (O₃) was lower for higher ethanol content in the fuel. In the U.S. car, NO₂ and O₃ had a small increase. Secondary particle (particulate matter [PM]) formation in the chamber decreased for both vehicles as the fraction of ethanol in fuel increased, consistent with previous studies. Secondary to primary PM ratios for pure gasoline is 11, also consistent with previous studies. In addition, the time required to form secondary PM is longer for higher ethanol blends. These results indicate that using higher ethanol blends may have a positive impact on air quality.

IMPLICATIONS

The use of bioethanol can significantly reduce petroleum use and greenhouse gas emissions worldwide. Given the extent of its use, it is important to understand its effect on urban pollution. There is a controversy on whether there is a reduction or increase in PM emission when using ethanol blends. Primary emissions of THC, CO, CO₂, NO_x, and NMHC for both cars decreased as the fraction of ethanol in gasoline increased. Using a photochemical chamber, the authors have found a decrease in the formation of secondary particles and the time required to form secondary PM is longer when using higher ethanol blends.

Formation mechanism of secondary organic aerosol from ozonolysis of gasoline vehicle exhaust

Gasoline vehicles are a major source of anthropogenic secondary organic aerosols (SOAs). However, current models based on known precursors fail to explain the substantial SOAs from vehicle emissions due to the inadequate understanding of the formation mechanism. To provide more information on this issue, the formation of SOAs from ozonolysis of four light-duty gasoline vehicle exhaust systems was investigated with a vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS). Remarkable SOAs formation was observed and the SOAs were primarily aliphatic alkenes. PI mass spectra of the SOAs from all vehicles exhibited similar spectral patterns (a regular mass group with m/z at 98, 112, 126 …). Interestingly, most carbonyl products of aliphatic alkenes observed as major gaseous products have specific molecular weights, and the main formation pathway of SOAs can be explained well using aldol condensation reactions of these carbonyls. This is a direct observation of the aldol condensation as a dominated pathway for SOAs formation, and the first report on the composition and formation mechanism of the SOAs from the ozonolysis of gasoline vehicle exhaust is given. The study reveals that low molecular weight alkenes may play a more significant role in vehicle-induced SOAs formation than previously believed. More importantly, the PI mass spectra of SOAs from vehicles show similarities to the field aerosol sample mass spectra, suggesting the possible significance of the aldol condensation reactions in ambient aerosol formation. Since carbonyls are a major degradation product of biogenic and anthropogenic VOCs through atmospheric oxidation processes, the mechanism proposed in this study can be applied more generally to explain aerosol formation from the oxidation of atmospheric hydrocarbons.

Characterization of secondary organic aerosol from photo-oxidation of gasoline exhaust and specific sources of major components

To further explore the composition and distribution of secondary organic aerosol (SOA) components from the photo-oxidation of light aromatic precursors (toluene, m-xylene, and 1,3,5-trimethylbenzene (1,3,5-TMB)) and idling gasoline exhaust, a vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS) was employed. Peaks of the molecular ions of the SOA components with minimum molecular fragmentation were clearly observed from the mass spectra of SOA, through the application of soft ionization methods in VUV-PIMS. The experiments comparing the exhaust-SOA and light aromatic mixture-SOA showed that the observed distributions of almost all the predominant cluster ions in the exhaust-SOA were similar to that of the mixture-SOA. Based on the characterization experiments of SOA formed from individual light aromatic precursors, the SOA components with molecular weights of 98 and 110 amu observed in the exhaust-SOA resulted from the photo-oxidation of toluene and m-xylene; the components with a molecular weight of 124 amu were derived mainly from m-xylene; and the components with molecular weights of 100, 112, 128, 138, and 156 amu were mainly derived from 1,3,5-TMB. These results suggest that C₇-C₉ light aromatic hydrocarbons are significant SOA precursors and that major SOA components originate from gasoline exhaust. Additionally, some new light aromatic hydrocarbon-SOA components were observed for the first time using VUV-PIMS. The corresponding reaction mechanisms were also proposed in this study to enrich the knowledge base of the formation mechanisms of light aromatic hydrocarbon-SOA compounds.

Emission characteristics of volatile organic compounds and their secondary organic aerosol formation potentials from a petroleum refinery in Pearl River Delta, China

A campaign was carried out to measure the emission characteristics of volatile organic compounds (VOCs) in different areas of a petroleum refinery in the Pearl River Delta (PRD) region in China. In the refining area, 2-methylpentane, 2,3-dimethylbutane, methylcyclopentane, 3-methylhexane, and butane accounted for >50% of the total VOCs; in the chemical industry area, 2-methylpentane, p-diethylbenzene, 2,3-dimethylbutane, m-diethylbenzene and 1,2,4-trimethylbenzene were the top five VOCs detected; and in the wastewater treatment area, the five most abundant species were 2-methylpentane, 2,3-dimethylbutane, methylcyclopentane, 3-methylpentane and p-diethylbenzene. The secondary organic aerosol (SOA) formation potential was estimated using the fractional aerosol coefficients (FAC), secondary organic aerosol potential (SOAP), and SOA yield methods. The FAC method suggests that toluene, p-diethylbenzene, and p-diethylbenzene are the largest contributors to the SOA formation in the refining, chemical industry, and wastewater treatment areas, respectively. With the SOAP method, it is estimated that toluene is the largest contributor to the SOA formation in the refining area, but o-ethyltoluene contributes the most both in the chemical industry and wastewater treatment areas. For the SOA yield method, aromatics dominate the yields and account for nearly 100% of the total in the three areas. The SOA concentrations estimated of the refining, chemical industry and wastewater treatment areas are 30, 3835 and 137μgm^-3, respectively. Despite the uncertainties and limitations associated with the three methods, the SOA yield method is suggested to be used for the estimation of SOA formation from the petroleum refinery. The results of this study have demonstrated that the control of VOCs, especially aromatics such as toluene, ethyltoluene, benzene and diethylbenzene, should be a focus of future regulatory measures in order to reduce PM pollution in the PRD region.

Public health impacts of secondary particulate formation from aromatic hydrocarbons in gasoline

BACKGROUND

Aromatic hydrocarbons emitted from gasoline-powered vehicles contribute to the formation of secondary organic aerosol (SOA), which increases the atmospheric mass concentration of fine particles (PM2.5). Here we estimate the public health burden associated with exposures to the subset of PM2.5 that originates from vehicle emissions of aromatics under business as usual conditions.

METHODS

The PM2.5 contribution from gasoline aromatics is estimated using the Community Multiscale Air Quality (CMAQ) modeling system and the results are compared to ambient measurements from the literature. Marginal PM2.5 annualized concentration changes are used to calculate premature mortalities using concentration-response functions, with a value of mortality reduction approach used to monetize the social cost of mortality impacts. Morbidity impacts are qualitatively discussed.

RESULTS

Modeled aromatic SOA concentrations from CMAQ fall short of ambient measurements by approximately a factor of two nationwide, with strong regional differences. After accounting for this model bias, the estimated public health impacts from exposure to PM2.5 originating from aromatic hydrocarbons in gasoline lead to a central estimate of approximately 3800 predicted premature mortalities nationwide, with estimates ranging from 1800 to over 4700 depending on the specific concentration-response function used. These impacts are associated with total social costs of $28.2B, and range from $13.6B to $34.9B in 2006$.

CONCLUSIONS

These preliminary quantitative estimates indicate particulates from vehicular emissions of aromatic hydrocarbons demonstrate a nontrivial public health burden. The results provide a baseline from which to evaluate potential public health impacts of changes in gasoline composition.

Gas-to-particle conversion in surface discharge nonthermal plasmas and its implications for atmospheric chemistry

This paper presents some experimental data on gas-to-particle conversion of benzene using nonthermal plasma (NTP) technology and discusses the possibility of its technical application in atmospheric chemistry. Aerosol measurement using a differential mobility analyzer (DMA) revealed that the parts of benzene molecules were converted into a nanometer-sized aerosol. Aerosol formation was found to be highly related with the missing part in carbon balance. Scanning electron microscopy analysis showed that the aerosols formed in synthetic humid air are the collection of nanoparticles. The carbonyl band (C=O) was found to be an important chemical constituent in the aerosol. The potential of the NTP as an accelerated test tool in studying secondary organic aerosol (SOA) formation from VOCs will be also addressed.

Exposure to Fine Particulate Matter (PM2.5) Among Highway Toll Station Workers in Taipei: Direct and Indirect Exposure Assessment

In this study, the authors assessed occupational exposure to PM2.5 among 47 highway toll station workers in Taipei, Taiwan. The subjects were monitored for 10 days to assess integrated 8-hr fine particulate matter (PM2.5) breathing zone concentration. Researchers constructed a microenvironment-time-concentration matrix and applied direct and indirect approaches to assess cumulative exposure. Mean PM2.5 concentration for workers in the truck and bus lanes was 308 microg/m3 (SD = 115.5 microg/m3), substantially higher compared with cash-payment car lanes (mean 115, SD = 41.8, p < 0.001) and ticket-payment car lanes (mean 109, SD = 48.7, p < 0.001). Concentration per vehicle in the truck and bus lanes was 6.4 and 3.7 times higher, respectively, than that of ticket- or cash-payment car lanes. Mean cumulative exposure for the 10-day period was 4,900-13,407 microg/m3.hr, with a mean of 8,019 microg/m3.hr (SD = 2,375.3). Indirect and direct concentrations were strongly correlated (r2 = .61, F(1,125); p = 0.000). The results of this study show that personal exposure to PM2.5 can be reliably estimated using indirect approaches.

Organic atmospheric particulate material

Carbonaceous compounds comprise a substantial fraction of atmospheric particulate matter (PM). Particulate organic material can be emitted directly into the atmosphere or formed in the atmosphere when the oxidation products of certain volatile organic compounds condense. Such products have lower volatilities than their parent molecules as a result of the fact that adding oxygen and/or nitrogen to organic molecules reduces volatility. Formation of secondary organic PM is often described in terms of a fractional mass yield, which relates how much PM is produced when a certain amount of a parent gaseous organic is oxidized. The theory of secondary organic PM formation is outlined, including the role of water, which is ubiquitous in the atmosphere. Available experimental studies on secondary organic PM formation and molecular products are summarized.