Internal presentation on toxicity of MgSO4 to Magela Creek, NT: laboratory and field results to date

Department of the Environment and Heritage, 2003

Internal Report 410
McCullough C, Humphrey C, Hogan A, Camilleri C, Douglas M, Gell P, Shiel R & van Dam R
Supervising Scientist Division

About the report

Magnesium sulphate (MgSO4) is a common mine contaminant for many mines through increased rates of weathering of waste rock. This is also true for the waste rock of the Ranger uranium mine where MgSO4 is a major constituent of waste waters. A discharge containing leachate with elevated solutes from this waste rock, flows from Retention Pond One (RP1) of the mine into the Magela Creek via Coonjimba Billabong during the wet season. However, the salinity arising from this salt has received very little ecotoxicological assessment and results of recent surveys of waterbodies receiving Ranger uranium mine run-off indicated that differences in macroinvertebrate community composition may be correlated with increased salinity arising from MgSO4 (O’Connor et al 1995, O’Connor et al 1996). Therefore, a study has been initiated to examine its effects on the ecology of Magela Creek downstream of Ranger uranium mine through laboratory ecotoxicity tests in natural creek water on specific species, and field mesocosm experiments on macroinvertebrate communities.