Incentives to use biofuels may result in increasing vehicular emissions of compounds detrimental to air quality. Therefore, regulated and unregulated emissions from a Euro 5a flex-fuel vehicle, ...tested using E85 and E75 blends (gasoline containing 85% and 75% of ethanol (vol/vol), respectively), were investigated at 22 and −7 °C over the New European Driving Cycle, at the Vehicle Emission Laboratory at the European Commission Joint Research Centre Ispra, Italy. Vehicle exhaust was comprehensively analyzed at the tailpipe and in a dilution tunnel. A fraction of the exhaust was injected into a mobile smog chamber to study the photochemical aging of the mixture. We found that emissions from a flex-fuel vehicle, fueled by E85 and E75, led to secondary organic aerosol (SOA) formation, despite the low aromatic content of these fuel blends. Emissions of regulated and unregulated compounds, as well as emissions of black carbon (BC) and primary organic aerosol (POA) and SOA formation were higher at −7 °C. The flex-fuel unregulated emissions, mainly composed of ethanol and acetaldehyde, resulted in very high ozone formation potential and SOA, especially at low temperature (860 mg O3km−1 and up to 38 mg C kg−1). After an OH exposure of 10 × 106 cm−3 h, SOA mass was, on average, 3 times larger than total primary particle mass emissions (BC + POA) with a high O:C ratio (up to 0.7 and 0.5 at 22 and −7 °C, respectively) typical of highly oxidized mixtures. Furthermore, high resolution organic mass spectra showed high 44/43 ratios (ratio of the ions m/z 44 and m/z 43) characteristic of low-volatility oxygenated organic aerosol. We also hypothesize that SOA formation from vehicular emissions could be due to oxidation products of ethanol and acetaldehyde, both short-chain oxygenated VOCs, e.g. methylglyoxal and acetic acid, and not only from aromatic compounds.
•Emissions from a flex-fuel vehicle, fueled with E85 and E75, lead to SOA formation.•These vehicles show higher regulated and unregulated emissions at −7 °C.•Unregulated emissions are mainly composed of ethanol and acetaldehyde.•SOA may arise from oxygenated compounds present in the exhaust.
This study investigates the influence of three environmental indoor parameters (i.e., temperature, relative humidity, and air exchange rate) on the emission of 13 volatile organic compounds (VOCs) ...and semi-volatile organic compounds (SVOCs) during incense burning. Experiments have been carried out using an environmental test chamber. Statistical results from a classical two-level full factorial design highlight the predominant effect of ventilation on emission factors. The higher the ventilation, the higher the emission factor. Moreover, thanks to these results, an estimation of the concentration range for the compounds under study can be calculated and allows a quick look of indoor pollution induced by incense combustion. Carcinogenic substances (i.e., benzene, benzo(a)pyrene, and formaldehyde) produced from the incense combustion would be predicted in typical living indoors conditions to reach instantaneous concentration levels close to or higher than air quality exposure threshold values.
Hydroxyl radicals (OH) are known to control the oxidative capacity of the atmosphere but their influence on reactivity within indoor environments is believed to be of little importance. Atmospheric ...direct sources of OH include the photolysis of ozone and nitrous acid (HONO) and the ozonolysis of alkenes. It has been argued that the ultraviolet light fraction of the solar spectrum is largely attenuated within indoor environments, thus, limiting the extent of photolytic OH sources. Conversely, the ozonolysis of alkenes has been suggested as the main pathway of OH formation within indoor settings. According to this hypothesis the indoor OH radical concentrations span in the range of only 104 to 105 cm–3. However, recent direct OH radical measurements within a school classroom yielded OH radical peak values at moderate light intensity measured at evenings of 1.8 × 106 cm–3 that were attributed to the photolysis of HONO. In this work, we report results from chamber experiments irradiated with varying light intensities in order to mimic realistic indoor lighting conditions. The exhaust of a burning candle was introduced in the chamber as a typical indoor source causing a sharp peak of HONO, but also of nitrogen oxides (NO x ). The photolysis of HONO yields peak OH concentration values, that for the range of indoors lightning conditions were estimated in the range 5.7 ×· 106 to 1.6 × 107 cm–3. Excellent agreement exists between OH levels determined by a chemical clock and those calculated by a simple PSS model. These findings suggest that significant OH reactivity takes place at our dwellings and the consequences of this reactivitythat is, formation of secondary oxidantsought to be studied hereafter.
Source contributions of organic aerosol (OA) are still not fully understood, especially in terms of quantitative distinction between secondary OA formed from anthropogenic precursors vs. that formed ...from natural precursors. In order to investigate the OA origin, a field campaign was carried out in Barcelona in summer 2013, including two periods characterized by low and high traffic conditions. Volatile organic compound (VOC) concentrations were higher during the second period, especially aromatic hydrocarbons related to traffic emissions, which showed a marked daily cycle peaking during traffic rush hours, similarly to black carbon (BC) concentrations. Biogenic VOC (BVOC) concentrations showed only minor changes from the low to the high traffic period, and their intra-day variability was related to temperature and solar radiation cycles, although a decrease was observed for monoterpenes during the day. The organic carbon (OC) concentrations increased from the first to the second period, and the fraction of non-fossil OC as determined by (14)C analysis increased from 43% to 54% of the total OC. The combination of (14)C analysis and Aerosol Chemical Speciation Monitor (ACSM) OA source apportionment showed that the fossil OC was mainly secondary (>70%) except for the last sample, when the fossil secondary OC only represented 51% of the total fossil OC. The fraction of non-fossil secondary OC increased from 37% of total secondary OC for the first sample to 60% for the last sample. This enhanced formation of non-fossil secondary OA (SOA) could be attributed to the reaction of BVOC precursors with NOx emitted from road traffic (or from its nocturnal derivative nitrate that enhances night-time semi-volatile oxygenated OA (SV-OOA)), since NO2 concentrations increased from 19 to 42 μg m(-3) from the first to the last sample.
Atmospheric particles have several impacts on health and the environment, especially in urban areas. Parts of those particles are not fresh and have undergone atmospheric chemical and physical ...processes. Due to a lack of representativeness of experimental conditions and experimental artifacts such as particle wall losses in chambers, there are uncertainties on the effects of physical processes (condensation, nucleation and
coagulation) and their role in particle evolution from modern vehicles. This study develops a new method to correct wall losses, accounting for
size dependence and experiment-to-experiment variations. It is applied to the evolution of fresh diesel exhaust particles to characterize the physical
processes which they undergo. The correction method is based on the black
carbon decay and a size-dependent coefficient to correct particle
distributions. Six diesel passenger cars, Euro 3 to Euro 6, were driven on a chassis dynamometer with Artemis Urban cold start and Artemis Motorway cycles. Exhaust was injected in an 8 m3 chamber with Teflon walls. The
physical evolution of particles was characterized during 6 to 10 h.
Increase in particle mass is observed even without photochemical reactions due to the presence of intermediate-volatility organic compounds and semi-volatile organic compounds. These compounds were quantified at
emission and induce a particle mass increase up to 17 % h−1, mainly for the older vehicles (Euro 3 and Euro 4). Condensation is 4 times
faster when the available particle surface is multiplied by 6.5. If initial particle number concentration is below 8–9 × 104 cm−3, a nucleation mode seems to be present but not
measured by a scanning mobility particle sizer (SMPS). The growth of nucleation-mode particles results in an increase in measured PN. Above this threshold, particle number concentration decreases due to coagulation, up to −27 % h−1. Under those conditions, the chamber and experimental setup are well suited to characterizing and quantifying the process of coagulation.
Fossil fuel-powered vehicles emit significant particulate matter, for example, black carbon and primary organic aerosol, and produce secondary organic aerosol. Here we quantify secondary organic ...aerosol production from two-stroke scooters. Cars and trucks, particularly diesel vehicles, are thought to be the main vehicular pollution sources. This needs re-thinking, as we show that elevated particulate matter levels can be a consequence of 'asymmetric pollution' from two-stroke scooters, vehicles that constitute a small fraction of the fleet, but can dominate urban vehicular pollution through organic aerosol and aromatic emission factors up to thousands of times higher than from other vehicle classes. Further, we demonstrate that oxidation processes producing secondary organic aerosol from vehicle exhaust also form potentially toxic 'reactive oxygen species'.
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