Temporal Variations of Particulate Air Pollution: A Marker for Free Radical Dosage and Adverse Health Effects?

Secondary organic aerosol formation during evaporation of droplets containing atmospheric aldehydes, amines, and ammonium sulfate

Reactions of carbonyl compounds in cloudwater produce organic aerosol mass through in-cloud oxidation and during postcloud evaporation. In this work, postcloud evaporation was simulated in laboratory experiments on evaporating droplets that contain mixtures of common atmospheric aldehydes with ammonium sulfate (AS), methylamine, or glycine. Aerosol diameters were measured during monodisperse droplet drying experiments and during polydisperse droplet equilibration experiments at 75% relative humidity, and condensed-phase mass was measured in bulk thermogravimetric experiments. The evaporation of water from a droplet was found to trigger aldehyde reactions that increased residual particle volumes by a similar extent in room-temperature experiments, regardless of whether AS, methylamine, or glycine was present. The production of organic aerosol volume was highest from droplets containing glyoxal, followed by similar production from methylglyoxal or hydroxyacetone. Significant organic aerosol production was observed for glycolaldehyde, acetaldehyde, and formaldehyde only at elevated temperatures in thermogravimetric experiments. In many experiments, the amount of aerosol produced was greater than the sum of all solutes plus nonvolatile solvent impurities, indicating the additional presence of trapped water, likely caused by increasing aerosol-phase viscosity due to oligomer formation.

Tropospheric air pollution: ozone, airborne toxics, polycyclic aromatic hydrocarbons, and particles

Tropospheric air pollution has impacts on scales ranging from local to global. Reactive intermediates in the oxidation of mixtures of volatile organic compounds (VOCs) and oxides of nitrogen (NOx) play central roles: the hydroxyl radical (OH), during the day; the nitrate radical (NO3), at night; and ozone (O3), which contributes during the day and night. Halogen atoms can also play a role during the day. Here the implications of the complex VOC-NOx chemistry for O3 control are discussed. In addition, OH, NO3, and O3 are shown to play a central role in the formation and fate of airborne toxic chemicals, mutagenic polycyclic aromatic hydrocarbons, and fine particles.

Chemical mixtures in atmospheric aerosols and their correlation to lung diseases and lung cancer occurence in the general population

Several chemical and epidemiological investigations have been done during the last decade showing that correlations do exist between ambient air concentrations of aerodisperse (particulate) pollutants and the health risk for the general population. Based on these recently published results, there are on-going discussions and considerations proposing changes in air particulate pollution definitions, measurement, analysis and air quality standards. In this review, we summarize the "chemical standpoint" of this problem and its impact on the measurement strategy and air quality standard assessment.