No abstract

The African continent continuously experiences extreme aerosol load conditions, during which the World Health Organization clean air standard of 10 μg/m3 of PM2.5 mass is systematically exceeded. Africa holds the world largest source of desert dust emissions, undergoes strong industrial growth, and produces approximately a third of the Earth's biomass burning aerosol particles. Sub‐Saharan biomass burning is driven by agricultural practices, such as burning fields and bushes in the postharvest season for fertilization, land management, and pest control. Thus, these emissions are predominantly anthropogenic. Here we use global atmospheric composition, climate, and health models to simulate the chemical composition of the atmosphere and calculate the mortality rates for Africa by distinguishing between purely natural, industrial/domestic, and biomass burning emissions. Air quality‐related deaths in Africa rank within the top leading causes of death in Africa. Our results of ~780,000 premature deaths annually point to the extensive health impacts of natural emissions, high mortality rate caused by industrialization in Nigeria and South Africa, and a smaller extent by fire emissions in Central and West Africa. In Africa, 43,000 premature deaths are linked to biomass burning mainly driven by agriculture. Our results also show that natural sources, in particular windblown dust emissions, have large impacts on air quality and human health in Africa.

No abstract

In this work, a binary fuel model for dimethyl ether (DME) and propane is developed, with a focus on engine-relevant conditions (10-50 atm and 550-2000 K). New rapid compression machine (RCM) data are obtained for the purpose of further validating the binary fuel model, identifying reactions important to low temperature propane and DME oxidation, and understanding the ignition-promoting effect of DME on propane. It is found that the simulated RCM data for DME/propane mixtures is very sensitive to the rates of C3H8 + OH, which acts as a radical sink relative to DME oxidation, especially at high relative DME concentrations. New rate evaluations are conducted for the reactions of C3H8 + OH = products as well as the self-reaction of methoxymethyl peroxy (in competition with RO2 = QOOH isomerization) of 2CH3OCH2O2 = products. Accurate phenomenological rate constants, (,), are computed by RRKM/ME methods (with energies obtained at the CCSD(T)-F12a/cc-pVTZ-F12 level of theory) for several radical intermediates relevant to DME. The model developed in this work (120 species and 700 reactions) performs well against the experimental targets tested here and is suitable for use over wide range of conditions. In addition, the reaction mechanism generator software, RMG, is used to explore cross-reactions between propane and DME radical intermediates. These cross-reactions did not have a significant effect on simulations of the conditions modeled in this work, suggesting that kinetic models for high-and low-reactivity binary fuel mixtures may be assembled from addition of their corresponding submodels and a small molecule foundation model.