Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 11/15/2001
Publication Date: N/A
Citation: Interpretive Summary: With the discovery of currently used pesticides (chlorpyrifos and trifluralin) in Bering/Chukchi ecosystem, it seemed important to attempt to model the loading of these chemicals to these pristine regions. The Chukchi sea region was discovered to be particularly well suited for modeling using an atmospheric-based fugacity model. The area is geographically well defined being mostly bordered by land on its southern edge and limited on the north by ice in the summer. An important input variable for the model is the air/water partition coefficient (HLC) for the pesticides. These constants are very sensitive to temperature and salinity of the water phase. By adjusting the respective HLC values to existing temperatures and salinity, the flux of these compounds into this area were predicted vary significantly from those derived from non adjusted values. Gas exchange and rain deposition (esp. for chlorpyrifos) accounted for most tof the loading with very little predicted from particle deposition. Modifying standard constants for increased salinity lowered the loadings of both trifluralin and chlorpyrifos, while adjusting temperatures to those typical to this Arctic region increased th eloadings of these chemicals. The model predicted the gas flux of chlorpyrifos to range from 112-117 ug/km2-day, and the rain amount to be 33 ug/km2-day; the gas flux for trifluralin was 104-109 ug/km2-day and essentially no rain deposition of trifluralin was predicted.
Technical Abstract: The loadings of the pesticides, chlorpyrifos and trifluralin, were modeled for the Chukchi sea region of the Arctic. These loadings were based on values measured from a 1993 joint US-Russian expedition to this area. Different HLC values, adjusted according to temperature and salinity, were used in a fugacity-based model to describe the flux of these compounds into othis area. Gas exchange and rain deposition (esp. for chlorpyrifos) accounted for most of the loading with very little predicted from particle deposition. Because of the importance of salinity and temperature on water solubility and therefore air/water partitioning, the model showed these to be critical variables affecting the final gas exchange loadings. Modifying these standard constants for salinity lowered the loadings of both trifluralin and chlorpyrifos, while adjusting temperatures to those typical to the Arctic increased the loadings of these chemicals. Adjusting HLCs to ovalues for microlayer and subsurface water that were measured in this area also tended to increase the loadings. Using the air/water constants most typical to conditions for this area the predicted fluxes of chlorpyrifos ranged from 112-117 ug/km2-day, gas, and 33 ug/km2-day rain; the gas flux for trifluralin was 104-109 ug/km2-day and essentially no rain flux.