Date of Award
Doctor of Philosophy
Michael L. Thompson
Land application of sewage sludge may introduce handful trace metals into soils and cause surface and ground water contamination. The mobilities of the metals are affected by dissolved organic carbon (DOC) in sludge or in soils. The major objective of the present study was to characterize the DOC in a digested sewage sludge and a sludge-amended soil and to examine the influence of DOC subcomponents on Cu mobility in an aquifer material collected near sludge application field;DOC from digested sewage sludge was fractionated according to its molecular weight (MW) and polarity. Investigations were performed on the mobilities and Cu-binding abilities of these subcomponents as well as their on influences on Cu transport in the aquifer material. The effect of sludge application on soil extractable DOC content and composition was also evaluated under two types of vegetation;Land application of sludge significantly increased the amount of extractable DOC in the soil and shifted it to hydrophilic and lower MW fractions ( 3500 daltons);The low-MW DOC (MW 500-3500 daltons) was found to be highly mobile, whereas the high-MW DOC (MW > 14,000 daltons) had a greater tendency to be adsorbed by the solid phase. Within the same MW fraction, the mobility of DOC followed the order of hydrophilic DOC > hydrophobic acids > hydrophobic neutrals. Cu breakthrough curves in the presence of various DOC subcomponents indicated that the DOC in sludge can mobilize Cu to a certain extent but can also inhibit Cu mobility dramatically. The facilitation or retardation effect was closely related to their Cu-binding abilities of DOC fractions rather than to their mobilities. The retardation of Cu mobility by DOC would reduce the potential of metal release to groundwater, alleviating concerns about possible groundwater contamination where sewage sludge is applied.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Han, Nizhou, "Composition and transport of sludge-derived organic carbon in soil and aquifer material " (1996). Retrospective Theses and Dissertations. 11529.