more on Xstrata’s Mt Isa Activities – from the Australian
LEAD pollution in popular swimming areas along Mt Isa’s Leichhardt River is hundreds of times higher than government limits. Concentrations of dissolved copper, zinc and cadmium, as well as levels of disease-causing bacteria, also exceed guidelines during the wet season, when the river and its tributaries are flushed by monsoonal rains.
Even in the dry season — when many of the streams and pools dry up — long-lasting water holes surpass heavy-metal and bacterial levels, which automatically trigger an investigation under the Australian and New Zealand Environment and Conservation Council (ANZECC) guidelines for aquatic systems.
“Some of the highest values we have come from a pool adjacent to a caravan park, where the kiddies swim,” said environmental scientist Mark Taylor of Sydney’s Macquarie University.
In that pool — sampled last January, during the wet season — lead concentrations were 2080 micrograms per litre.
The maximum ANZECC limit is 9.4mcg/L. Copper was 2600mcg/L (ANZECC limit: 2.5mcg/L); cadmium, 50 mcg/L (0.9mcg/L); and zinc, 4400mcg/L (31mcg/L).
The discovery raises public-health issues because children could easily ingest the contaminates. Pets and native animals also drink from the pools.
Studies in the US and Australia have linked blood lead levels as low as 10mcg per decilitre (one-tenth of a litre) to intellectual and behavioural difficulties in kids.
The discovery of heavy metal and bacterial contamination in the pools follows an earlier analysis of soil and dust in and around Mt Isa, also conducted by Dr Taylor and his colleagues.
As The Australian revealed last month, that study uncovered significant pollution with heavy metals, including lead, zinc and copper.
At one residential site lead levels were 33 times higher than federal guidelines.
Since The Australian’s report, Swiss mining giant Xstrata, owner of the Mt Isa Mine, told a residents’ meeting it would undertake a new environmental study.
But the environment manager for Xstrata North Queensland, environmental engineer Ed Turley, denied the announcement followed public concern over the findings.
“It had nothing to do with Dr Taylor’s study,” he said.
Mr Turley said the study had been discussed with the Environmental Protection Agency last year and was part of the mine’s environmental monitoring. It would complement that done by Dr Taylor’s group.
Mr Turley chose not to comment on the new water study until he had seen the data.
Dr Taylor will present the findings this week during the American Association of Geographers’ annual meeting in San Francisco. According to Dr Taylor, little of the new-found contamination came from Xstrata’s mining practices.
Most of the heavy metals came from erosion of “historical” sources such as old slag heaps or tailings ponds, he said.
Dr Taylor suspected recent “accidental releases” from the mine made a small contribution.
He suggested the bacterial and nutrient contamination might have come from leaking urban and industrial pipes, along with runoff from horse paddocks irrigated by the sewage recycling scheme.