Processes controlling diurnal variations of PCDD/Fs in the New Jersey coastal atmosphere.

Lohmann, Rainer and Brunciak, Paul A. and Dachs, Jordi and Gigliotti, Cari L. and Nelson, Eric and Van Ry, Daryl and Glenn, Thomas and Eisenreich, Steven J. and Jones, Joanne L and Jones, Kevin C. (2003) Processes controlling diurnal variations of PCDD/Fs in the New Jersey coastal atmosphere. Atmospheric Environment, 37 (7). pp. 959-969. ISSN 1352-2310

Abstract

Consecutive 12 hour day–night air samples (500 m3 each) were taken over 7 days at three land-based sites and an over-water site in coastal New Jersey (NJ) in July 1998, in a campaign designed to shed light on factors controlling ambient PCDD/F concentrations. The sampling sites were chosen to reflect contrasting environments: urban/industrial from the center of the New York (NY)–NJ metropolitan area (Liberty Science Center, LSC); coastal Atlantic (Sandy Hook, SH); suburban NJ (New Brunswick, NB); over-water in Raritan Bay (RB). Despite proximity to the major NY/NJ conurbation, ambient PCDD/F concentrations in the region were low compared to literature data for other urban locations. Mean ∑Cl4–8DD/Fs and ∑TEQ (in fg/m3) were: 1400 and 16 at NB; 1000 and 9.5 over RB; 880 and 8.5 at LSC; and 830 and 6.6 at SH. Di- and tri-chlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) were also measured and dominated the ∑Cl2–8DD/F concentrations. Air–water exchange calculations demonstrated the relative importance of Cl2–3DD volatilizing from the Lower Hudson River Estuary for ambient concentrations (25% of advection), but was of minor importance for the other PCDD/Fs. The study provides evidence that advective transport, local inputs and atmospheric processes combine in a complex manner to control ambient PCDD/F concentrations. These processes generally dominate any local diurnal influence of OH-radical-mediated depletion, which we had hypothesized would be detectable by measuring higher night- and day-time concentrations. Rather, it is implied that changes in the mixed boundary layer height resulted in higher night- than daytime concentrations at the urban and coastal sites. A strong diurnal signal, dominated by the lower chlorinated dioxins and furans, was detected at the rural site (NB) during a period of lower wind speeds.