Household humidification is widely practiced to combat dry indoor air. While the benefits of household humidification are widely perceived, its implications to the indoor air have not been critically appraised. In particular, ultrasonic humidifiers are known to generate fine particulate matter (PM). In this study, we first conducted laboratory experiments to investigate the size, quantity, and chemical composition of PM generated by an ultrasonic humidifier. The mass of PM generated showed a correlation with the total alkalinity of charge water, suggesting that CaCO 3 is likely making a major contribution to PM. Ion chromatography analysis revealed a large amount of SO 4 2− in PM, representing a previously unrecognized indoor source. Preliminary results of organic compounds being present in humidifier PM are also presented. A whole-house experiment was further conducted at an actual residential house, with five low-cost sensors (AirBeam) monitoring PM in real time. Operation of a single ultrasonic humidifier resulted in PM 2.5 concentrations up to hundreds of μg m −3 , and its influence extended across the entire household. The transport and loss of PM 2.5 depended on the rate of air circulation and ventilation. This study emphasizes the need to further investigate the impact of humidifier operation, both on human health and on the indoor atmospheric chemistry, for example, partitioning of acidic and basic compounds.

Biomass burning is a dominant source of ultrafine particulate matter in the atmosphere. Particulate matter is a leading health risk factor on a global scale, causing millions of premature deaths annually. Biomass burning also emits short-term climate forcers which contribute to the warming of the Earth’s atmosphere. Wood and animal dung are widely employed in the developing world as the primary sources of household energy. While wood burning is well studied, emissions from dung remain largely uncharacterized. Emissions from a given burn are highly complex chemical mixtures. While specific biomass tracerssuch as levoglucosanare employed to track burns, a fundamental chemical understanding of biomass emissions is required to predict their impacts. Herein, we conducted comprehensive sets of chemical analyses for particles emitted from biomass burning. Samples were generated using a tube furnace allowing reproducible, precise control of conditions. Emission factor data for levoglucosan and its isomers were measured from extracted particulate matter. We found that the levoglucosan emission factors from two distinct types of cow dung were consistently lower than that from wood. The water-extractable fraction of dung emissions exhibited light-absorptive properties greater than wood. Nontargeted chemical characterization was achieved through deconvolution of high-resolution mass spectrometry data. Overall, we present that the key differences between wood and dung emissions mirror the differences in their fuel compositions. The complexity of the extracted spectra and the unique characteristics of dung emissions accentuate the need for further study on biomass types less common within the Western context.

Biomass burning is a major source of short-lived climate forcers, e.g., brown carbon (BrC), that absorb solar radiation and cause warming of the Earth’s atmosphere. A large fraction of the...

Biomass burning is a significant contributor to atmospheric pollution, its emissions have been found to have adverse impacts on climate and human health. Largely, these impacts are dictated by how...

No abstract