Semivolatile organic compounds in the ambient air of Denver, Colorado

Abstract

A filter-polyurethane foam plug high volume air sampler was used to collect the particle (P) and vapor (V) phases of four classes of semivolatile organic compounds (SOC) in Denver, CO: n-alkanes. polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), and organochlorine pesticides. The carbon preference index (CPI) of n-alkanes in the V or P phases alone was skewed by temperature-dependent V/P partitioning; a combined gaseous + particulate CPI was preferred. The CPI suggested that the alkanes in Denver air were predominently petrogenic. Total PCB were calculated as the sum of individual congeners and also as Aroclor equivalents, with good agreement between the two methods. Apparent V/P distributions of these compound classes were expressed as A(TSP)/F, were A and F are the adsorbent- and filter-retained SOC concentrations (ng m −3) and TSP is the total suspended particle concentration (μg m −3). Values of A(TSP)/F were related to the average sampling temperature ( T, K) through: log [ A( TSP)/ F] = m/ T + b. Fitted log A(TSP)/F at 5°C correlated well with p L 0 at 5°C, the SOC liquid vapor pressure. No differences were observed in partitioning behavior among the four SOC types.