Trace Metal Associations in Urban Airborne Particulates

Abstract

Air pollution monitoring for trace elements in aerosols should seek to determine which elements are pollutants, where they go, and whether they may cause undesirable effects. Several sampling and analysis schemes and auxiliary studies, carried out within and remote from the Chicago area, are reviewed here and are evaluated for their possible inclusion into larger national air monitoring programs. Initially, an approximate elemental emissions inventory for the urban region was calculated from available published information and was used to account for contributions from major pollution sources. A multi-station study of urban and non-urban near surface air led to discovery of certain elemental correlations useful in distinguishing pollution from regional background and in tracing long distance transport of pollutants. Particle size distributions gave insights concerning types of processes at pollution sources and identification of unsuspected sources. Diurnal variations suggested meteorological factors which may regulate concentrations in air. Auxiliary laboratory studies can confirm mechanisms for alteration of aerosol composition by chemical reactions in the atmosphere. For certain elements, e.g., some non-metals and semi-metals, anomalous natural sources at the sea or land surface must be further documented before long distance transport from localized pollution sources can be quantified.