The current environmental impact of base-metal mining at the Tui Mine, Te Aroha, New Zealand

The current environmental impact of base metal mining at the Tui Mine, Te A roha and gold mining near Waihi, was investigated by analysis of local wate rs, stream sediments, and aquatic vegetation. X-ray diffraction analysis of heavy metal fractions in stream sediments showed the presence of pyrite in the upper reaches of the Tunakohoia and Tui Streams that drain the mineral ised reefs and Tui tailings dam. Relatively immobile lead (galena) was reta ined close to the source, whereas copper and zinc minerals were more mobile and distributed further downstream from the areas of mineralisation. Gold was determined in sediments from the Ohinemuri and Waitekauri Rivers along with other heavy metals derived from sulphide mineralisation at Waihi and W aitekauri. Analysis of waters from the Tui and Tunakohoia Streams showed co ncentrations of arsenic, cadmium, lead and zinc above recommended levels fo r potable-water in the upper parts of these waterways. The discharge of the se streams into the Waihou River (sampled upstream from Te Aroha and downst ream to past Paeroa) did not have any significant effect on heavy-metal con centrations in this river. Aquatic macrophytes sampled in the Waihou, Ohine muri and Waitekauri Rivers had very high heavy-metal concentrations compare d with the ambient water and should be considered as potentially useful for assessing the impact of low-metal fluxes into the waters. Gold was detecte d in aquatic macrophytes from streams draining both the Martha Mine at Waih i and the Golden Cross Mine at Waitekauri and indicated the possibility of prospecting for gold by analysis of these plants.