... depression of soil pH to 4.5 following a 300 tons/ha sludge loading. Sludge- processing mode, soil type, soil texture and time since application had substantial eects on perco-late metal mobilities ... al. / Environmental Pollution 109 (2000) 327±346 345Eect of sludge- processing mode, soil texture and soil pH on metal mobility in undisturbed soil columns under accelerated loadingB.K. Richardsa,*, ... pelletized, alkaline-stabilized, composted, and incinerated), soil type and initial soil pH on trace metal mobility was examined using undisturbed soil columns. Soils tested were Hudson silt loam...