Short-term temperature-dependent air-surface exchange and atmospheric concentrations of polychlorinated naphthalenes and organochlorine pesticides

Atmospheric concentrations of five organochlorine (OC) pesticides, some of which have been banned for a number of years, and polychlorinated naphthalenes (PCNs) were measured at a U.K. site over periods of 6 h for 7 days resulting in 28 samples. Mean concentrations of the pesticides were alpha-HCH 90 pg m(-3), gamma-HCH 500, p,p'-DDE 8, dieldrin 63, endrin 22, and HCB 39. PCN mean homologue concentrations were (3)CNs 67 pg m(-3), (4)CNs 78, (5)CNs 5, (6)CNs 0.6, (7)CNs 0.6, and Sigma PCNs 152. TEQ concentrations for those PCNs ascribed TEF values ranged between 0.36 and 3.6 fg m(-3) which corresponds to similar to 3.0-30% of the TEQ concentrations of PCDD/Fs at the same site. All the compounds measured, except HCB, exhibited a strong temperature-dependent diurnal eye ring. Results from Clausius-Clapeyron plots show that pesticide concentrations were controlled by temperature-driven air-surface recycling throughout the first 5 days when stable atmospheric conditions were dominant, while during the last 2 days advection became more influential as more unstable and cooler weather started to influence the site. PCN concentrations were controlled primarily by a mixture of recycling and advection throughout the first 5 days and then by advection in the final 2 days, suggesting that there are ongoing emissions from diffuse point sources of PCNs into the U.K. atmosphere. This study provides further evidence of the rapid air-surface exchange of semivolatile organic compounds (SOCs) and shows how different factors alone or in combination can produce rapid changes in the atmospheric concentrations of past and present SOCs.