FITTING PHOSPHORUS ADSORPTION ISOTHERMS ON LOWLAND SOILS USING A COMBINATION OF ADSORPTION AND MULTISTEP DESORPTION TECHNIQUES

References: 16th International Multidisciplinary Scientific GeoConference SGEM 2016, SGEM Vienna GREEN Extended Scientific Sessions, www.sgemviennagreen.org, SGEM2016 Conference Proceedings, ISBN 978-619-7105-81-0 / ISSN 1314-2704, 2 - 5 November, 2016, Book 3 Vol. 3, 137-148pp, DOI: 10.5593/SGEM2016/HB33/S02.018

ABSTRACT

Soils from a lowland small sub-catchment of the Tisza river have been analysed for phosphorus adsorption characteristics in Hungary. Five genetic soil class have been determined based on national soil databases and 21 soil samples have been collected and analysed, 3-5 samples per class. The aim of the study was to create isotherms for the soil samples and to examine if characteristic P adsorption isotherm could be fitted for each soil type, using regression between isotherm parameters and soil properties such as pH, particle size distribution etc. Would that be possible, runoff (mainly artificial draining of excess water inundations) P concentrations and loading could be estimated better than currently possible. Multistep desorption was used to assess the originally adsorbed P on soil samples. On most soil samples the method worked well and linear regression with good fits (r2 mostly in the range of 0.8-0.95) could be used on the lower section of the isotherms. Except for few soils the adsorption experiment results fitted well with the section received by multistep desorption. In most soil types there were soil samples that behaved very similarly and could be described with one common isotherm. Using regression to estimate some of the isotherm parameters from soil properties is possible but further improvement and validation is necessary.

Keywords: phosphorus adsorption isotherm, desorption, originally sorbed P, linear regression, lowland soils