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[1] Particles generated by combustion of fossil fuels contribute to climate forcing by absorbing and scattering visible light. Residential combustion takes place in homes for heating or cooking purposes and is thought to contribute a large fraction of the global burden of anthropogenic primary particles. We present optical properties and size distributions of particulate matter emitted from three types of coal burned in residential combustors: bituminous coal, hard coal briquettes, and lignite. Emissions from these coals differ significantly and can be partially explained by differences in coal composition. For bituminous coal, particulate matter emission factors are somewhat greater than those used in current emission inventories. We observe particles for which the light absorption is weak and has a strong spectral dependence. For hard coal briquettes and lignite, emitted light absorption is low, and based on our measurements, current inventories of lightabsorbing aerosols significantly overestimate the contribution from these sources. Hard coal briquettes produce very few particles in the optically active size range. For all coals tested the size distributions required to represent the average of the emitted particles are broader than atmospheric size distributions, with geometric standard deviations between 2.2 and 3.0.

A mathematical model for the flash calcination of Ca(OH)2 and CaC03 is presented. The model describes the decomposition of the parent material at the reactant-product interface, the diffusion of C02 or H20 through the growing CaO layer, and the sintering of the CaO layer. The model is qualitative, but it provides useful estimates of peak C02 pressures in the CaO layer, relative rates of surface area development and loss for Ca(OH)2 and CaC03, the effect of particle size, and the effects of time and temperature.

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