The objective of this study was to (1) measure the concentration of four anions (Cl-, F-, NO
and SO ) and nine other elements (Al, Ba, Ca, K, Mg, Mn, Fe, Ni, and Si) in two nontraditional
biopolymeric chemical stabilizers (EBCS1 and EBCS2), (2) investigate consequent environmental
toxicity risk implications, and (3) create awareness regarding environmental
health issues associated with metal concentration levels in enzyme-based chemical stabilizers
that are now gaining widespread application in road construction and other concrete materials.
Potential ecotoxicity impacts were studied on aqueous extracts of EBCS1 and EBCS2 using
two thermodynamic properties models: the Pitzer–Mayorga model (calculation of the electrolyte
activity coefficients) and the Millero–Pitzer model (calculation of the ionic activity
coefficients). Results showed not only high concentrations of a variety of metal ions and inorganic
anions, but also a significant variation between two chemical stabilizing mixtures. The
mixture (EBCS2) with the lower pH value was richer in all the cationic and anionic species
than (EBCS1). Sulfate ( ) concentrations were found to be higher in EBCS2 than in
EBCS1. There was no correlation between electrolyte activity and presence of the ionic species,
which may be linked to a possible high ionic environmental activity. The concentrations
of trace metals found (Mn, Fe, and Ni) were low compared to those of earth metals (Ba, Ca,
K, and Mg). The metal concentrations were higher in EBCS1 than in EBCS2. Data suggest that
specific studies are needed to establish “zero” permissible metal ecotoxicity values for elements
and anions in any such strong polyelectrolytic enzyme-based chemical stabilizers.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:tut/oai:encore.tut.ac.za:d1001442 |
| Date | 08 January 2010 |
| Creators | Ndibewu, PP, Mgangira, MB, Cingo, N, McCrindle, RI |
| Publisher | Taylor & Francis |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | |
| Rights | © Taylor & Francis Group, LLC |
| Relation | Journal of Toxicology and Environmental Health |
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