Impacts of Global Solid Biofuel Stove Emissions on Ambient Air Quality and Human Health.

Global solid biofuel stove emissions strongly impact air quality, climate change, and human health. However, investigations of the impacts of global solid biofuel stove emissions on human health associated with PM2.5 (particulate matter with aerodynamic diameter ≤2.5 µm) and ozone (O3) are limited. Here, we quantify the impacts of global solid biofuel stove emissions on ambient PM2.5 and O3 air quality and the associated human health effects for the year 2010, using the Community Atmosphere Model coupled with Chemistry version 5.3. Annual mean surface PM2.5 concentrations from global solid biofuel stove emissions averaged over 2006-2010 are up to 23.1 µg m-3, with large impacts found over China, India, sub-Saharan Africa, and eastern and central Europe. For surface O3 impacts, we find that global solid biofuel stove emissions lead to increases in surface O3 concentrations by up to 5.7 ppbv for China, India, and sub-Saharan Africa, and negligible impacts or reductions of up to 0.5 ppbv for the US, Europe, and parts of South America. Global solid biofuel stove emissions for the year 2010 contribute to 382,000 [95% confidence interval (95CI): 349,000-409,000] annual premature deaths associated with PM2.5 and O3 exposure, with the corresponding years of life lost as 8.10 million years (95CI: 7.38-8.70 million years). Our study highlights air quality and human health benefits of mitigating emissions from the global solid biofuel stove sector, especially over populous regions of low-income and middle-income countries, through promoting clean household energy programs for the residential energy supply.

Global Climate and Human Health Effects of the Gasoline and Diesel Vehicle Fleets.

The global gasoline and diesel fuel vehicle fleets impose substantial impacts on air quality, human health, and climate change. Here we quantify the global radiative forcing and human health impacts of the global gasoline and diesel sectors using the NCAR CESM global chemistry-climate model for year 2015 emissions from the IIASA GAINS inventory. Net global radiative effects of short-lived climate forcers (including aerosols, ozone, and methane) from the gasoline and diesel sectors are +13.6 and +9.4 mW m-2, respectively. The annual mean net aerosol contributions to the net radiative effects of gasoline and diesel are -9.6 ± 2.0 and +8.8 ± 5.8 mW m-2. Aerosol indirect effects for the gasoline and diesel road vehicle sectors are -16.6 ± 2.1 and -40.6 ± 4.0 mW m-2. The fractional contributions of short-lived climate forcers to the total global climate impact including carbon dioxide on the 20-year time scale are similar, 14.9% and 14.4% for gasoline and diesel, respectively. Global annual total PM2.5- and ozone-induced premature deaths for gasoline and diesel sectors approach 115,000 (95% CI: 69,000-153,600) and 122,100 (95% CI: 78,500-157,500), with corresponding years of life lost of 2.10 (95% CI: 1.23-2.66) and 2.21 (95% CI: 1.47-2.85) million years. Substantial regional variability of premature death rates is found for the diesel sector when the regional health effects are normalized by the annual total regional vehicle distance traveled. Regional premature death rates for the gasoline and diesel sectors, respectively, vary by a factor of eight and two orders of magnitude, with India showing the highest for both gasoline and diesel sectors.

Surface residence and uptake of methyl chloride and methyl alcohol at the air/water interface studied by vibrational sum frequency spectroscopy and molecular dynamics.

Vibrational sum frequency generation (VSFG) spectroscopy and molecular dynamics (MD) simulations are used to study the surface residence and organization of gas-phase methyl halide and methyl alcohol molecules adsorbed to the air/water interface, while Raman spectroscopy is used to detect the uptake of the gas-phase species into the bulk aqueous phase. Spectroscopy results reveal the presence of methyl alcohol in the bulk and at the surface. Methyl chloride is detected in the bulk, but not at the surface. This indicates that methyl alcohol adsorbs to the aqueous surface in a layer that is ordered, in agreement with previous studies, and is also readily taken up into the bulk aqueous phase, whereas methyl chloride adsorbs, but, while being taken up into the bulk liquid, has lower surface number density and/or forms a more disordered surface layer than methyl alcohol. MD simulations show that methyl halide molecules transition readily between the gas phase and interface, resulting in significantly shorter residence times at the surface for the methyl halides relative to methyl alcohol. Both the geometries that the methyl species adopt at the interface and the interactions between the methyl species and the interfacial water molecules differ for the halides and the alcohol. Complementary studies of butyl species show similar results: butyl alcohol adsorbs to the aqueous surface in a layer that exhibits a certain degree of order corresponding to the chains aligned along the surface normal, while a markedly more disordered surface layer and shorter residence times are observed in MD simulations for the butyl halides as compared to the alcohol. Desorption from the interface was found to be less frequent for the butyl halides than for the methyl halides by MD simulations. Although Raman studies show uptake of the butyl alcohol into the bulk phase, neither Raman studies nor MD simulations provide any evidence for uptake of the butyl halides into the bulk phase. The profound difference in preferred orientations between alkyl halides and alcohols at the aqueous surface, with the halogen atom of the alkyl halides being to a large degree exposed to the vapor phase, is likely to have consequences for chemistry of alkyl halides adsorbed on the surface of atmospheric aerosol particles.

Competition between DPPC and SDS at the air-aqueous interface.

Vibrational sum frequency generation spectroscopy is used to study the interactions of the charged soluble organic surfactant sodium dodecyl sulfate (SDS) with an insoluble 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer at the air-aqueous interface. Results indicate that the surfactant species compete for surface sites in the mixed system, with a lower monolayer number density of DPPC molecules being observed in the presence of dodecyl sulfate anions at the interface. Spectroscopic results also indicate that fewer dodecyl sulfate chains reside at the interface when the insoluble DPPC film is present. Increased conformational ordering of the acyl chains of both the DPPC molecules and the interfacial dodecyl sulfate anions is observed in the mixed system. Additionally, charged surfactant SDS promotes the alignment of the interfacial water molecules even in the presence of a DPPC monolayer.