『Abstract
The aim of the study was to determine whether the application
of superphosphate fertiliser to soils contaminated with mine wastes
can inhibit metal and metalloid mobility (Cu, Pb, Zn, Cd, Fe,
Mn, As, Sb) in the long term. Contaminated soils contained sulfide-
and sulfate-rich waste materials from the Broken Hill and Mt Isa
mining centres. Results of long-term (10 months) column experiments
demonstrate that fertiliser amendment had highly variable effects
on the degree of metal and metalloid mobolisation and capture.
Rapid release of metals from a sulfate-rich soil showed that phosphate
amendment was ineffective in stabilising highly soluble metal-bearing
phases. In a sulfide-rich soil with abundant organic matter, complexing
of metals with soluble organic acids led to pronounced metal (mainly
Cd, Cu and Zn) release from fertiliser-amended soils. The abundance
of pyrite, as well as the addition of fertiliser, caused persistent
acid production over time, which prevented the formation of insoluble
metal phosphate phases and instead fostered an increased mobility
of both metals and metalloids (As, Cd, Cu, Sb, Zn). By contrast,
fertiliser application to a sulfide-rich soil with low organic
carbon content and a sufficient acid buffering capacity to maintain
near-neutral pH resulted in the immobilisation of Pb in the form
of newly precipitated Pb phosphate phases. Thus, phosphate stabilisation
was ineffective in suppressing metal and metalloid mobility from
soils that were rich in organic matter, contained abundant pyrite
and had a low acid buffering capacity. Phosphate stabilisation
appears to be more effective for the in situ treatment of sulfide-rich
soils that are distinctly enriched in Pb and contain insignificant
concentrations of organic matter and other metals and metalloids.
Keywords: Mine waste; Metals; Fertiliser; Immobilisation; Remediation』
1. Introduction
2. Materials and methods
2.1. Materials
2.2. Material characterisation
2.3. Laboratory experiments and analyses
2.4. Quality control of geochemical data
3. Results
3.1. Soils
3.2. Feltiliser
3.4. Chemical composition of leached soil columns
3.5. Microprobe element mapping of amended soils
4. Discussion
4.1. Phase reactions in amended and non-amended soils
4.2. Element mobility in amended and non-amended soils
4.3. Limitations of phosphate amendment
5. Conclusions
Acknowledgements
References