Modeling short-term variability of α-hexachlorocyclohexane in Northern Hemispheric air



[1] The POP version of the Danish Eulerian Hemispheric Model (DEHM-POP) is a further development of a 3-D dynamic atmospheric chemistry transport model covering the Northern Hemisphere, which was originally developed to study atmospheric transport of conventional air pollutants and other atmospheric constituents (e.g., SOX, heavy metals, and CO2). Four different surface compartments (soil, ocean water, vegetation, and snow) are introduced in DEHM-POP with each compartment including the most dominant dynamic processes determining the exchange between air and the surface type to account for the consecutive cycles of deposition and reemission of persistent organic pollutants (POPs). This model setup makes it possible to study short-term atmospheric variability of POPs, which is exemplified in this paper by a study of the atmospheric variability of α-hexachlorocyclohexane (α-HCH), the major component of the worldwide most used insecticide: technical HCH. Simulated α-HCH air concentrations are evaluated against measurements from 21 monitoring stations within the model domain, and the model is able to predict the annual average concentration as well as the long-term trend for the 1990s. Significant correlations between simulated and measured short-term atmospheric concentrations of α-HCH are also found at the majority of the investigated monitoring stations, which shows that it is possible to resolve the atmospheric variability of POPs using an atmospheric chemistry transport model. Differences between simulated and measured atmospheric α-HCH variability can arise because the measurements may be influenced by local features that are not accounted for in the model with the relatively coarse horizontal resolution and surface description.