Radial dilution model for the distribution of toxaphene in the United States and Canada on the basis of measured concentrations in tree bark

摘要

Toxaphene was a highly chlorinated pesticide that was used in the United States from the 1950s until its restriction and ban in the 1980s It was primarily used on cotton in the southern United States, and perhaps as a result, toxaphene is found in high concentrations in the southern United States Toxaphene has also been detected at remote locations such as in the high Canadian Arctic. However, these and other studies focused on selected regions of the United States and Canada, which only allowed for a limited interpretation of these data. We report here the concentrations of toxaphene measured in 46 tree bark samples collected in the United States and Canada. Concentrations were found to be greatest in the Mississippi River Valley along the borders of southern Missouri and Arkansas. We created a simple model based on radial dilution from a central location in the south central United States to describe toxaphene concentrations in tree bark and in air throughout the United States and Canada. The toxaphene concentrations were successfully described by this inverse square distance model. A bark-atmosphere partition coefficient for toxaphene was also calculated that was similar to literature-derived octanol-air partition coefficients. High concentrations of toxaphene still exist in areas where it was heavily used but decline rapidly with distance.