Oceana Gold as part of their environmental strategy are
looking at various methods for cost-effective revegetation of their tailings
dams. Under the concept of revegetating the tailings this study looked at
several issues. These issues were; testing different methods of revegetation,
arsenic (As) uptake in vegetation with respect to capping thickness, and
background As levels in farmland areas above mineralised rocks. A number of
plots were set up in a temporarily disused tailings dam to trial the direct
sowing of ryecorn into the tailings.

Ryecorn was sown in sandy tailings (ca 1000 mg/kg As) and
then covered with oxidised schist to anchor the seeds. This proved successful
and ryecorn was established. Once the plots covered with oxidised schist were
growing, 1 m and 2 m strips were sown on the sheltered side of the existing
plots without the covering of oxidised schist. The uncovered plots also
established successfully. From this set of trials a sowing plan can be developed
that uses a minimum of resources to successfully establish vegetation. The
maximum As content of the ryecorn was 80 mg/kg. Clover, Yorkshire fog and ryegrass plant matter was sampled from a
pot trial that used different thicknesses of topsoil covering tailings material.
As the thickness of topsoil increased, the amount of As taken up decreased. Soil
samples were taken from farmland areas which were known to have elevated levels
of As (up to 1000 mg/kg) in the top 10 cm. Vegetation samples were also taken
from the same locations, and show the As levels in plants is <50>
mg/kg.