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Parameterization and regionalization of Cd sorption characteristics of sandy soils. II. Regionalization: Freundlich k estimates by pedotransfer functions
Author(s) -
Springob Günther,
Böttcher Jürgen
Publication year - 1998
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.1998.3581610613
Subject(s) - pedotransfer function , soil water , sorption , freundlich equation , total organic carbon , chemistry , soil science , regression analysis , mathematics , ionic strength , environmental chemistry , statistics , environmental science , adsorption , hydraulic conductivity , organic chemistry , aqueous solution
The aim was to describe Cd sorption in spatially variable sandy soils of the ‘Fuhrberger Feld’ catchment area as a prerequisite for prognosis of Cd transport in soil and of the threat of groundwater pollution. Thus, the possibility is evaluated to derive a generalized Freundlich equation based on multiple regressions relating the retention parameters k and M (from isotherm data of part 1 of this study) to basic soil properties (pedotransfer functions). For the parameter M (exponent), the correlation ‘measured vs estimated’ was weak (r 2 < 0.5) whereas k was well predictable by pedotransfer functions. The best regression was obtained if organic carbon (OC). clay content and H + activity were combined as independent variables (r 2 up to 0.96). The obtained k values were much higher than those from comparable literature models, probably due to lower ionic strength and different composition of our background solutions used for the isotherms. As a critical evaluation, the estimates for k were used to derive solute Cd concentrations (C est ) which then were compared to measured data (range 0.1–3 μg L −1 ). The best but still unsatisfactory r 2 was 0.77, obtained if G est was compared to Cd in 0.01 M c Ca(NO 3 ) 2 equilibria (Cd 0 ). Cd in fresh soil solution (Cd z ) showed no significant correlation with C est , except for one relationship where OC had been excluded from the preceding multiple regression of k. Generally, the role of the variable OC remained unclear. Direct multiple regressions of measured solute Cd vs soil properties (bypassing k, no sorbed fraction) yielded much closer correlations, with r 2 = 0.9 for Cd 0 vs OC, H + activity, clay (log data, OC decreases C) and r 2 = 0.7 for Cd 2 vs OC, H + activity, clay (log data, OC enhances C).