Estimation of North American Anthropogenic Sulfur Deposition as a Function of Source/Receptor Separation

Abstract

The relative contributions to acidic or acidifying deposition in North America from local sources and from long-range sources are contentious matters. Indeed, there is not even agreement on the terms of reference. To some, the term local implies that the source and the receptor are in the same political or administrative entity, such as a state or Environmental Protection Agency Region. To others, local and mesoscale transport are out to 500 km, with transport greater than 500 km termed continental or long-range. Since states and provinces encompass a wide range of shapes and areas, and since this research effort is aimed toward investigation of rather fundamental aspects of transport and deposition rather than who is doing what to whom, we here combine all U.S. and Canadian emissions of anthropogenic sulfur, and calculate separately the deposition contributions from sources located within 200 km, from 200 to 500 km, from 500 to 1000 km, and more than 1000 km from each receptor in turn. For convenience, we will call the source/receptor separation categories local, regional, long-range, and continental, respectively.