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Describing the Transport of Ion‐Exchanging Contaminants Using an Effective K d Approach
Author(s) -
Valocchi Albert J.
Publication year - 1984
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr020i004p00499
Subject(s) - ternary operation , dispersion (optics) , ion exchange , contamination , aquifer , constant (computer programming) , groundwater , ion , binary number , thermodynamics , mechanics , chemistry , environmental science , geology , mathematics , physics , computer science , geotechnical engineering , ecology , arithmetic , organic chemistry , optics , biology , programming language
Hydrogeologists have traditionally used distribution coefficients K d to describe the rate of migration of sorbing contaminants. Recent investigations have questioned the validity of the K d approach for contaminants governed by multicomponent ion exchange and have noted that computed K d values in such cases are not constant across an advancing solute front. This report demonstrates that mass balance arguments can nevertheless be utilized to define a constant “effective” K d which may then be used to calculate the contaminant front velocity. For selected cases of one‐dimensional binary and ternary exchange, front locations calculated using the effective K d approach agree closely with concentration profiles calculated using a general numerical simulation model of ion‐exchanging solute transport. The effective K d approach is also applied to a field problem involving the injection of advanced‐treated municipal effluent into a shallow confined aquifer. Although the effective K d approach is sometimes a practically useful tool, it is shown to be limited to situations where dispersion can be neglected.