| Summary: | A study of two biological indicators was undertaken to investigate the factors that influence the levels of heavy metals as indicated by these biological indicators. The two indicators investigated were the shellfish Chione (Austrovenus) stutchburyi, which was used as an indicator of lead and cadmium in the Avon-Heathcote Estuary, Christchurch, New Zealand, and human teeth, which were used as an accumulative indicator of lead exposure to humans.
The factors that were found to affect lead concentrations in the shellfish chosen were size and breeding cycle activity. A temporal study of lead concentrations in these shellfish established that the levels of lead were determined by rainfall over Christchurch and the source of lead was identified as being the waste products of a small lead smelter and battery factory on the banks of the Heathcote River. It was shown that lead accumulated in the shells of the shellfish by both incorporation (during shell growth) and isomorphous replacement after surface absorption.
The factors that were found to influence the lead levels in permanent teeth were tooth type, tooth age, type of tooth material analysed and area of tooth from which sample was taken. Lead concentrations measured in whole or partial sets showed that lead levels reflect tooth age. A survey comparing suburban and rural children demonstrated that rural children had lower teeth lead concentrations but that this difference was not statistically significant, though for inner city children the difference was significant.
A study of lead in river sediments showed that lead tended to be localised at points of entry and its sources were storm water run off and industrial waste from a battery factory. The chemistry of lead in the sediment was found to be determined by sediment pH and the redox conditions of the sediment. Also, an investigation of sorption of lead onto river sediments was carried out.
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