NOAEM (natural organic anion equilibrium model): A data analysis algorithm for estimating functional properties of dissolved organic matter in aqueous environments: Part I. Ionic component speciation and metal association

NOAEM is a flexible data analysis algorithm (PC FORTRAN program) that estimates functional properties of dissolved organic matter (DOM) in aqueous environments. Included are the quantity and quality of natural organic anion (NOA); kinds, quantities, and equilibrium constants of NOA bound metals; concentrations of ionic species; acid neutralizing capacity, conductivity, and ionic strength of the sample; and partitioning capacity of nonpolar portions of DOM for synthetic organic chemicals (NOAEM: Part II). NOAEM is based in ionic balance and determines parameters via the anion deficit of a sample. The assumptions are that NOA may be represented by a continuous distribution of individual anionic functional groups and that free and cation bound NOA exhibit a lognormal distribution of apparent pK values. Protolytic NOA is defined by four variables. Metal bound NOA is defined by three additional variables for each multivalent metal ion. Ions and ionic compounds that are not bound to NOA are speciated thermodynamically. The theoretical equations are reported and chemical data from a field site are utilized for preliminary validation of the model.