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University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Earth Sciences / Master / Master of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

Concentrations of Fe, Al, Mn and Zn were measured monthly from April to October at 24 rural riverine sites in Ontario and Quebec. Empirical models were developed predicting riverine metal concentrations from a small set of within-stream and catchment variables. Models explained a significant proportion of the variation in Fe (85%), Al (90%), Mn (57%) and Zn (37%). Simple models predicting annual catchment exports of metals from average riverine suspended particulate concentrations and runoff were also developed. These models explained most of the variation in annual exports of Fe (94%), Al (92%), Mn (62%) and Zn (75%) from the 24 catchments. / Models such as these can be used both to estimate catchment exports of metals to lakes, and to estimate riverine metal concentrations without requiring chemical analyses. The models also serve to distinguish background levels from those indicating metal contamination, and will, therefore, be useful in design of water quality guidelines.

A variety of extractants were used to fractionate the trace metals Cd, Cu, Mn, Ni, Pb, and Zn in contaminated urban soils. The metals were mostly held in soil solid phases but not in soluble and exchangeable forms. Except for Mn, extractability of metals by selective chemicals was mainly a function of the contamination level. The speciation of these elements in water, 0.01 M CaCl2, and pH-adjusted water extra was calculated using the chemical equilibrium model MINEQL+. The free ions of Cd, Ni, and Zn were the predominant species in most of the water and 0.01 M CaCl2 extracts while PbCO30 was the main form of Pb. Organically complexed Cu accounted for over of the total dissolved Cu. The solubility of trace metals increased as solution pH was decreased. Metals Cd, Ni, Pb and Zn combined with Cl- at low pH (<5). Organically complexed Cu was shifted to Cu2+ when pH was decreased. / Except for Mn, the activities of the other metals in water, 0.01 M CaCl 2 extracts, and pH-adjusted water extracts were undersaturated with respect to established minerals in soils. MnHPO4 seems to be controlling the solubility of Mn in these extracts.

The work in this thesis demonstrates whether resins are better than conventional soil extractants at predicting plant metal concentrations, and whether low-cost soil treatments can effectively reduce metal content and concentrations in lettuce leaves. / Researchers have shown that ion exchange resins can simulate root metal uptake behaviour by acting as ion sinks. Chemical extractants on the other hand, generally do not behave in this manner. Thus, we would expect resins (in either bead or membrane form) to predict plant metal concentrations better than conventional extractants. For the first study, a procedure using anion exchange resin membranes (AEM) treated with either EDTA or DTPA chelators was chosen, since previous studies showed this method to be effective at predicting plant metal uptake, and practical for routine laboratory use. In addition, several conventional extractants were selected for comparison. / For the second part of the thesis, a study was undertaken to test the effectiveness of various food processing byproducts to stabilize metal contaminants in soils, and compare the results with those of a Na-based aluminosilicate (zeolite). (Abstract shortened by UMI.)

Numerous urban soils surrounding industrial and metallurgical facilities in the U.S. are contaminated with metals including lead (Pb), cadmium (Cd), copper (Cu), Zinc (Zn), chromium (Cr), and nickel (Ni). Simplified geochemical mapping requires soil sampling and analysis for the presence of heavy metals from a grid pattern within a geographic area. In this study, a contour map of metal concentrations at two depths was subsequently superimposed over a standard political map to indicate areas of elevated metal concentrations in the soil. Natural levels of Pb, Cd, Cu, Zn, Cr, and Ni in Delaware County soils were determined to be 114.2 mg/kg, 0.14 mg/kg, 29.3 mg/kg, 88.4 mg/kg, 9.0 mg/kg, and 39.8 mg/kg, respectively. The average concentrations of metals found throughout Muncie, 203.9 mg/kg Pb, 39.2 mg/kg Cu, 275.4 mg/kg Zn, 9.7 mg/kg Cr, and 25.0 mg/kg Ni, were compared with natural levels to determine the extent of heavy metal pollution from atmospheric deposition. From the geographic mapping of metal concentrations, the effect of past industrial processes on possible contamination of soils by metals in Muncie, Indiana, was determined. Metals were also be fractionated in order to assess the percentage which is potentially bioavailable. / Department of Natural Resources and Environmental Management