Thermal processes and secondary recycling regulate the atmospheric levels of the highly toxic polychlorinated naphthalenes in the urban environment of Eastern Mediterranean and Middle East.

Although production of legacy industrial-grade persistent organic pollutants has been prohibited since the early 2000's, residues persist across all environmental compartments, with unintentional releases still documented globally. The present work explores comprehensively the atmospheric occurrence and fate of the scarcely monitored polychlorinated naphthalenes (PCNs), along with polybrominated diphenyl ethers (PBDEs), in the urban environment of Eastern Mediterranean and Middle East. Gaseous and particulate phase concentrations of PCNs and PBDEs (fifty-six and twelve congeners) were comparable to urban locations in the broader region. For PCNs, regressions of partial pressure against ambient temperature revealed secondary recycling from local contaminated surfaces. Enthalpies of surface-air exchange (∆H) were significantly correlated to vaporization enthalpies (∆H), corroborating short-range revolatilization processes. Molecular concentration ratios suggested inputs from thermal processes, whereas potential evaporation from Aroclor-contaminated surfaces cannot be excluded. An inverse pattern for PBDEs was observed. The regression slopes were shallow, implying advective inflows of urban air, whereas ∆H were insignificantly correlated with ∆H, suggesting that, unlike PCNs, volatilization sources for PBDEs were of minor importance. Gas/particle partitioning was also evaluated by utilizing a wide range of traditional and novel models. Additionally, temperature-dependent quantitative structure-property relationship (QSPR) models were constructed separately for PCNs and PBDEs. Mixed sorptive and absorptive models yielded adequate predictions for PCNs, while steady-state models performed better for PBDEs. Both QSPR models demonstrated robust predictive capabilities across the congener groups and could serve as reference for studies under similar temperature ranges worldwide.