ABSTRACT
Information on the fate and behavior of geothermal arsenic (As) in receiving waters is usually limited, when compared to research on As in geothermal features or their immediate discharges. However, in New Zealand the close proximity of the North Island’s geothermally active Taupo Volcanic Zone, and the Waikato River, the longest and most utilized river in the country, has meant that As in this lowland river has received considerable attention. Hot springs on both undeveloped (e.g. Orakeikorako and Wai-o-tapu) geothermal fields, and developed fields (e.g. Ohaaki and Mokai) drain to the Waikato River (Fig. 1). However, the largest single source of geothermal As is the waste bore water from Wairakei Power Station on the Wairakei/Tauhara geothermal field. Consequently, As concentrations in Waikato River water typically range from 0.02 to 0.06 mg/L (e.g. McLaren & Kim 1995).
