Fig. 1. (a) Calcium, (b) Mg, (c) Mn, and (d) Fe distributions in sludge and soil samples. CL, clay loam; CLc, calcareous clay loam; Cs, saline clay; -h, highly contaminated soil; L, loam; -l, low-level contaminated soil; -r, noncontaminated reference soil; SLhy, hydromorphous sandy loam.