Arsenic

Arsenic has been found in some Marlborough groundwaters at levels above the human health limit specified in the NZ Drinking Water Standards.

These areas include Rarangi, Wairau Valley, Riverlands and parts of the Southern Valleys or Lower Wairau Plain.

Most of the arsenic detected to date has originated from natural sources such as the mineral arsenopyrite.

Risk factors for arsenic-rich groundwater include: geological faults, wetlands and deeply buried aquifers which are oxygen deficient. A small amount is also leached from residues in historic sheep dips and landfills.

In 2003/04 the Marlborough District Council commissioned HortResearch to investigate the extent of arsenic leaching from copper-chromium-arsenic (CCA) treated vineyard support posts to groundwater. They found that arsenic was lost to the soil immediately surrounding the post but remained localised, which meant it did not travel through the soil layer into the groundwater below.

Arsenic is routinely tested for by Marlborough District Council, and surveys are planned in new areas to see if arsenic exists at harmful levels.

If you have concerns over the level of arsenic in your groundwater, you should have it tested (See YellowPages.co.nz for Laboratories in Marlborough).