Speciation of arsenic in ambient aerosols collected in Los Angeles

First-time measurements of the potentially toxic inorganic species of arsenic (arsenite and arsenate) have been obtained in fine (less than 2.5 microns AD) and coarse (greater than 2.5 microns AD) atmospheric particles in the Los Angeles area. A recently developed method that includes procedures for sample collection, preparation, and analysis was used in this study. Size-fractionated aerosol samples were collected with a high-volume dichotomous virtual impactor that employed polytetrafluoroethylene filters. Results were obtained for the recovery of arsenic standards added to unexposed and collected filters. Data from this study, indicated that the recently developed speciation method can be used to determine concentrations of As(III) and As(V) in atmospheric particulate matter samples. Size-fractionated aerosol samples were collected in the city of Industry during January and February 1987. In most samples, As(III) and As(V) were above the detection limit (approximately 1 ng m-3 of either species) in both aerosol size fractions. A greater portion (about 75 percent) of the two species were observed in the fine particles. The As(III)/As(V) ratio for both particle sizes was close to 1 (i.e., an equal mixture of both species). Comparison of total suspended particulate arsenic measured by the speciation method to that measured by a routine California Air Resources Board-approved procedure showed good agreement (r = 0.94), indicating both methods were approximately equivalent for the collection and analysis of aerosol arsenic.