Inorganic Contaminants in Suspended Solids from Hamilton Harbour

Abstract

Concentrations of heavy metals and phosphorus were measured in suspended solids collected from Hamilton Harbour in the spring and late summer of 1986. Forms of iron were determined using Mossbauer spectroscopy and related to the concentrations of heavy metals and phosphorus. Two iron forms, wustite and hematite, originating from anthropogenic activities were identified in addition to naturally occurring Fe 2+ from chlorite and clays and Fe 3+ from amorphous iron oxides. The highest metal concentrations are found in deep water and in areas adjacent to outfalls. The concentrations of wustite and hematite are correlated with the concentrations of heavy metals, particularly Zn and Pb. Heavy metals in suspended solids exceed guidelines for open water disposal of dredged sediments. Annual loadings of heavy metals to the sediments, calculated from the heavy metal concentrations in suspended solids, are ∼477 × 10 3 kg Fe, 16 × 10 3 kg Zn, 3 × 10 3 kg Pb, 958 kg Cu, 469 kg Ni, and 56 kg Cd. Phosphorus concentrations in suspended solids are high and range between 3,100 mg kg −1 and 7,300 mg kg −1. Higher than average non-apatite inorganic P (NAI-P) concentrations in solids are observed in samples taken from the vicinity of municipal discharges. Manganese and iron were released from bottom sediments during summer anoxia in the hypolimnion of the deep water; however, no phosphorus release was observed. The results indicate that wustite and hematite are good tracers of industrial pollution and their distribution is of importance in determining the particle dynamics in Hamilton Harbour.