Fig. 4. Stability ratio of soils as a function of polyacrylamide (PAM) molecular weight [high molecular weight PAM(H) or moderate molecular weight PAM(M)], aggregate size (0.5- to 1.0- or 1.0- to 2.0-mm) and water quality (deionized water [DW] or gypsum solution [GS]). For a given soil, columns labeled with same letter are not significantly different at the P < 0.05 level.