The determination and role of peroxyacetil nitrate in photochemical processes in atmosphere

Gridded 1 km × 1 km emission inventory for paddy stubble burning emissions over north-west India constrained by measured emission factors of 77 VOCs and district-wise crop yield data

Every year in the post-monsoon season, ~1.7 billion tons of paddy stubble is burnt openly in the Indo-Gangetic Plain (IGP) producing persistent smog and air quality deterioration that affects the entire IGP. Information concerning the identity, amounts and spatial distribution of volatile organic compounds (VOCs) which drive ozone and aerosol formation is still largely unknown as existing global emission inventories have poor VOC speciation and rely on limited satellite overpasses for mapping burnt areas. Here, emission factors (EFs) of 77 VOCs were measured from paddy fire smoke and combined with 1 km × 1 km stubble burning activity constrained by annual crop production yields and detected fires to compile a new gridded emission inventory for 2017. Our results reveal a large source of acetaldehyde (37.5 ± 9.6 Ggy-1), 2-furaldehyde (37.1 ± 12.5 Ggy-1), acetone (34.7 ± 13.6 Ggy-1), benzene (9.9 ± 2.8 Ggy-1) and isocyanic acid (0.4 ± 0.2 Ggy-1) that are not accounted for by existing emission inventories (GFED, GFAS, FINv2.1). During October-November, these emissions (346 ± 65 Ggy-1 NMVOC; 38 ± 8 Ggy-1 NOx; 16 ± 4 Ggy-1 NH3; 129 ± 9 Ggy-1 PM2.5; 22,125 ± 3674 Ggy-1 GHG CO2 equivalents) are more than 20 times larger than corresponding emissions from traffic and municipal waste burning over north-west India. Mitigation of this source alone can therefore yield massive air-quality climate co-benefits for more than 500 million people.

Analysis of major pollutants and physico-chemical characteristics of PM2.5 at an urban site in Rome

Air quality data from a one year study at an urban roadside location in Rome are reported for major pollutants. Continuous concentration data of carbon monoxide, ozone, nitrogen dioxide, aromatic hydrocarbons and natural radioactivity were measured in the urban air of Rome from January 2016 to January 2017. Moreover, PM_2.5 mass concentration and physico-chemical characteristics of single constituent particles are herein reported. Gaseous pollutants, except ozone, and PM_2.5 showed maximum concentrations in December due to high atmospheric stability. O₃ and NO₂ trend analysis showed photochemical smog episodes in June and September. In September, during a photochemical smog episode the aromatic hydrocarbons contribution to ozone formation was experimentally proven. Pearson's coefficient among aromatic hydrocarbons and the ratio Toluene/Benzene (T/B) showed that pollutants were under the influence of vehicular traffic. Physico-chemical characterization of PM_2.5 single particles, carried out by field emission scanning electron microscope combined with energy dispersive X-ray spectroscopy, displayed the presence of particle diversity from natural and anthropogenic origin. Four principal components in the PM_2.5 were identified: carbonaceous particles, Ca-sulphates, soil dust and building structure particles, metal particles. The principal source of carbonaceous particles in this urban area consists of the motor vehicle exhausts and the heating systems in winter. Traces of S and sometimes S, Na, K were detected on varying percentages of carbonaceous particles. These data suggested that the carbonaceous particles act as vehicles for strong acids, prevalently H₂SO₄ and alkaline metal sulphates. A Saharan dust contribution to PM_2.5 was found in different periods. Metal particles included iron oxide particles, metals oxide particles and Fe-rich metal compounds. The identification of chemical composition of individual particles provide useful information to determine their origin and formation processes.

Benchmark study on fine-mode aerosol in a big urban area and relevant doses deposited in the human respiratory tract

It is well-known that the health effects of PM increase as particle size decreases: particularly, great concern has risen on the role of UltraFine Particles (UFPs). Starting from the knowledge that the main fraction of atmospheric aerosol in Rome is characterized by significant levels of PM2.5 (almost 75% of PM10 fraction is PM2.5), the paper is focused on submicron particles in such great urban area. The daytime/nighttime, work-/weekdays and cold/hot seasonal trends of submicron particles will be investigated and discussed along with NOx and total PAH drifts demonstrating the primary origin of UFPs from combustion processes. Furthermore, moving from these data, the total dose of submicron particles deposited in the respiratory system (i.e., head, tracheobronchial and alveolar regions in different lung lobes) has been estimated. Dosimeter estimates were performed with the Multiple-Path Particle Dosimetry model (MPPD v.2.1). The paper discusses the aerosol doses deposited in the respiratory system of individuals exposed in proximity of traffic. During traffic peak hours, about 6.6 × 10(10) particles are deposited into the respiratory system. Such dose is almost entirely made of UFPs. According to the greater dose estimated, right lung lobes are expected to be more susceptible to respiratory pathologies than left lobes.