Geothermal mercury pollution in New Zealand

New Zealand Journal of Marine and Freshwater Research

1988

Lithium and rubidium in the Waikato River originate partly from geothermal fluids and partly from weathering of surficial volcanic rocks. This paper reports on the distribution and behaviour of these metals in the river system. Total Li concentrations in the river water increased from 0.079 g/m 3 at the Lake Taupo outlet to 0.435 g/m 3 at Mercer, but the ratios of filtrable to particulate metal decreased from 1.82 to 0.322, respectively. The corresponding concentrations for Rb were 0.038 and 0.626 g/m 3, and the ratios were 0.095 and 0.040. Geothermal fluids are the source of about 80% of filtrable Li but only 50% of filtrable Rb. Weathering of volcanic rocks contributes the remainder of the metals. Approximately 11001 each of total Li and total Rb flow annually past Lake Aratiatia and more than 99% of these totals flow into the Tasman Sea. About 3 t of Li and 6 t of Rb accumulate each year into reservoir sediment; reservoir macrophytes, which probably turn over each year, could contain up to 0.5 t of Li and 8.4 t of Rb. Within the reservoir sediments and macrophytes, Li, Rb, and K each show different distributions.

Section: Introductionmentioning

confidence: 99%

Lithium and rubidium in the Waikato River, New Zealand

New Zealand Journal of Marine and Freshwater Research

1988

“…Dissolved oxygen occasionally sags to 6 g rrr 3 in the lower river (Strachan 1979). Arsenic is present in the river water at levels sometimes exceeding the WHO international standard (Aggett & Aspell 1980;Timperley 1980) and mercury accumulates in trout to levels of more than 0.5 mg kg 1 (Weissberg & Zobel 1973). Concern over the state of the river has prompted many investigations on specific aspects of the Waikato River and these have been reviewed by Strachan (1979).…”

Section: Introductionmentioning

confidence: 99%

Dissolved coloured compounds and suspended matter in the waters of the middle Waikato River

New Zealand Journal of Marine and Freshwater Research

1985

Concentrations of suspended matter and filtrable hydroxylated aromatic compounds (HAC) together with turbidity and light absorbance measurements at 270 and 750 nm are reported for monthly samples, over one year, of water from the tailraces of the nine hydroelectric power stations on the Waikato River, North Island, New Zealand. Between Lakes Aratiatia and Karapiro the suspended matter concentrations increase 3-fold. The concentrations of HAC increase only slightly in all lakes except Lake Maraetai where a 3-fold increase occurs because of Kraft bleach effluent from the New Zealand Forest Products Limited, Kinleith Mill. This effluent also causes a marked increase in the absorbance at 270 nm, a measure of the brown colour attributable to dissolved organic compounds. The HAC in the effluent are linearly related to absorbance at 270 nm. The use of these easily measured parameters for detecting changes in water appearance, i.e., colour and clarity, are discussed. Measurements of light scattering, either turbidity or absorbance, appear to have sufficient sensitivity to detect changes in relative water clarity. The ratio of inorganic to organic suspended matter increases down the river and measurements of these two components could be used to detect changes in water appearance resulting from changes in the suspended matter composition. The absorbance at 270 nm of filtered water is a convenient and sensitive indicator of dissolved colour but a range of unidentified compounds contribute to this absorbance and for control of the brown coloration caused by timber processing effluents, limits on the discharge of HAC may be more useful.

“…A Kraft pulp-and-paper mill discharges effluent into the fifth reservoir, Lake Maraetai, down-stream of Lake Taupo. In their investigation of the effects on trout of Hg losses from the chloralkali plant at this mill, Weissberg & Zobel (1973) first identified geothermal fluids in the upper Waikato River catchment as probable sources of the Hg in the river.…”

Section: Introductionmentioning

confidence: 99%

“…The Waikato River is the region's most utilised freshwater resource (Huser et al 1994) and the Hg discharge from the Timperley & Hill-Discharge of mercury Wairakei station has long been a concern, particularly for the trout fisheries in the river's reservoirs. Early studies showed that Hg concentrations (wet weight) in trout increased from c. 0.1 mg kg" 1 in Lake Taupo to more than 1.0 mg kg" 1 in the four lower reservoirs (Weissberg & Zobel 1973;Brooks et al 1976). More recent studies reported mean concentrations in trout ranging from 0.07 mg kg" 1 in Lake Taupo to 0.4 mg kg" 1 in Lake Ohakuri (Robinson et al 1995).…”

Section: Introductionmentioning

confidence: 99%

Discharge of mercury from the Wairakei geothermal power station to the Waikato River, New Zealand

New Zealand Journal of Marine and Freshwater Research

Hill

1997

The Wairakei geothermal power station on the west bank of the Waikato River 10 km north of Lake Taupo, New Zealand, discharges a warm mixture of cooling water and geothermal steam condensate to the river. This discharge contains at least two chemical species of mercury (Hg flows out of Lake Aratiatia, the reservoir formed for the Aratiatia hydro-electric power station 3 km down-stream from the Wairakei station. The residence time of the condensate in Lake Aratiatia varies between 1.5 h at high river flow and 12 h during winter when water is accumulated in the lake overnight. The warm condensate initially floats on the surface of the river but only a small proportion of the Hg 0 is lost to the atmosphere. Furthermore, the short residence time of the condensate in the lake probably limits the extent to which other mechanisms can remove Hg 0 from the river water. For these reasons it is concluded that most of the Hg 0 discharged to the river from the Wairakei Received 4 October 1996; accepted 24 March 1997 station remains as Hg 0 in the water flowing out of Lake Aratiatia. Fine-grained bed sediments in Lake Aratiatia are an insignificant sink for Hg because of their very small area and relatively low total Hg concentrations. It seems likely, therefore, that the non-reducible forms of Hg discharged with the condensate also remain in the river water and pass out of the lake. M96075