Fig. 5. Sorption isotherms for sorption of p-nitrocyanobenzene (p-NCB) and 1,4-dinitrobenzene (1,4-DNB) by K+- and Mg2+–saturated Pahokee peat, Houghton muck, and Brookston loam. Isotherms with different letters (a, b, c, d, e) represent statistical difference at p < 0.05.