The need for spatial interpolation models in the regulatory environment has grown in the past few years. The EPA is using these models to review decisions on monitoring network design and to predict the efficacy of emission control programs. Due to the limited number of monitoring sites across the country for ambient concentrations of ozone and fine particles, there is a need to use spatial interpolation to predict ambient concentrations in unmonitored locations. Support for these methods has emerged from scientists and state/local/EPA agencies in recent workshops. The general consensus is that it is now possible to model the spatial dependence of air pollution data to reliably predict concentrations in unmonitored locations along with associated uncertainties for use in developing regulatory policy. EPA recognizes the merits of these methods, more specifically kriging, for use in the modeled attainment tests for the 8-hour ozone and PM 2.5 National Ambient Air Quality Standards attainment demonstrations. These methods provide environmental decision makers the opportunity to show important gradients of air pollution, review the location of monitoring networks and refine the definition of nonattainment boundaries. The purpose of this document is to provide an overview and better understanding of spatial interpolation methods.

Project Officer: Ellen Baldridge. "November 2004." "EPA-454/R-04-004." Includes bibliographical references. Battelle