Record Display for the EPA National Library Catalog


OLS Field Name OLS Field Data
Main Title Evaluation of Procedures for Aggregating Nonlinear Sulfate Adsorption Isotherm Data.
Author Shaffer, P. W. ; Stevens., D. L. ;
CORP Author NSI Technology Services Corp., Corvallis, OR.;Corvallis Environmental Research Lab., OR.
Publisher c1991
Year Published 1991
Report Number EPA-68-03-3246; EPA/600/J-91/157;
Stock Number PB91-226332
Additional Subjects Inorganic sulfates ; Soil analysis ; Adsorption ; Land pollution ; Water pollution ; Isotherms ; Watersheds ; Procedures ; Acidification ; Deposition ; Surface waters ; Water chemistry ; Environmental transport ; Nonlinear systems ; Reprints ;
Library Call Number Additional Info Location Last
NTIS  PB91-226332 Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy. 11/26/1991
Collation 11p
As part of a study to assess potential regional surface-water acidification in the southern Blue Ridge region of the USA, more than 700 individual soils were sampled from 35 watersheds and analyzed. Sulfate adsorption isotherms were generated for all mineral soil horizons. Subsequent use of these data in dynamic watershed chemistry models required aggregation of adsorption data to two or three isotherms (one per soil mineral horizon) per watershed. The study evaluated several techniques for aggregation of the nonlinear adsorption-isotherm data. Results of the study show that aggregated-data values are extremely sensitive to the choice of aggregation procedure. The aggregated-coefficient and aggregated-point procedures appear to be straight-forward, reasonable approaches to data aggregation, but the aggregated functions generated by these procedures are usually biased; use of these procedures is strongly discouraged. In contrast, the aggregated-isotherm approach provided an effective means of aggregating data, even for very heterogeneous groups of isotherms; use of this procedure is recommended for aggregation of adsorption isotherms and for data for similar non-linear functions.