The OH-initiated chemical transformation of 1,2,4,6,8,10,11-heptachloroundecane in the atmosphere

Abstract

Short chain chlorinated paraffins (SCCPs) have recently drawn public attention because they have properties similar to persistent organic pollutants. In this study, 1,2,4,6,8,10,11-heptachloroundecane (HCU) is selected as a model molecule to investigate the chemical transformation of SCCPs using density functional theory (DFT) methods. After hydroxyl (OH) radicals initiate hydrogen (H) atom abstraction reactions, the produced intermediates could be further oxidized in the presence of O₂/NO. The main products were found to be chloro-aldehydes and chloro-ketones after dechlorination reactions, or chloro-hydrins after reaction with H₂O. These products have strong water solubility and polarity. Cl and OH radicals, which have strong reactivity, are also generated in the degradation process. Rate constants were calculated using transition state theory and the Arrhenius formulas were fitted. The total rate constant for the reaction of HCU with OH radicals is about 1.67 × 10⁻¹² cm³ per molecule per s at room temperature. The atmospheric lifetime of HCU relative OH radicals is about 7.1 days.