In this subtitle the following words have the meanings indicated. “Acid deposition” means the process whereby acid–forming chemical compounds are transported from the atmosphere to the surface of the earth. “Acid deposition precursor” means an air contaminant that may be transformed to an acid gas or particle in the atmosphere. “Commission” means the Maryland Public Service Commission. “Departments” means the Department of Natural Resources and the Department of the Environment. “Participating agencies” means the Commission, the People’s Counsel of the Public Service Commission, and the Departments of Commerce, Agriculture, and Transportation, and the Department of Planning.