Mining and Arsenic
Arsenic occurs in various mineral forms, as arsenides in sulphide minerals and as arsenates. The most common mineral is arsenopyrite (FeAsS), which is also found in arsenolite (As2O3), olivenite (Cu2OHAsO4), mimetite (Pb5Cl(AsO4)3 and cobaltite (CoAsS).
In the weathering of sulphides, arsenic can be oxidised to arsenite and arsenate. Arsenic oxide is also formed as a by-product of copper, lead and nickel smelting.
The toxicology of arsenic and its compounds has attracted increasing attention and a particular concern involves the possible influence of the low-level exposures to various species of arsenic in the general population and in occupationally exposed groups.
Sources of Arsenic
Roaster off-gases constitute the major source of arsenic emissions from mining operations which roast sulphide concentrates containing arsenopyrite. Other contaminants such as antimony and sulphur dioxide may also be present in the air emissions. Other mines may produce tailing with high residual arsenic concentrations due to the presence of arsenopyrite in the ore, overburden and soil.
Arsenic in Water
Surface waters and groundwater in areas receiving fallout from roaster off-gas emissions or passing through soils with geologically high concentrations of arsenic can become contaminated. Drinking water sources which tap these contaminated surface or groundwaters may also be contaminated. Elevated concentrations of arsenic can be found in surface waters affected directly by mine area runoff and/or treated or untreated tailing discharges.
Arsenic in Soil and Food
Elevated concentrations of arsenic can be found in the soil and plant food species in areas receiving fallout from roaster off-gases or having naturally high geological sources of arsenic. People consuming seafood are exposed to organic arsenic species and this has to be differentiated from mine arsenic sources by examining individual arsenic species.
Operatives who work in gold roasting plants may be exposed to high concentrations of arsenic in dust-laden air surrounding roasting furnaces or emission control systems, e.g., fabric filter baghouses and transmission points.
Arsenic analyses of multimedia can be carried out on effluents, water, plants, fish, soils, animals, aquatic sediments, and human scalp hair, urine, and blood.
EnviroGulf Consulting subcontracts international testing authority-approved laboratories to conduct arsenic analyses:
- Total arsenic.
- Arsenic species (arsenate, arsenite, monomethylarsonate, dimethylarsinate, or sum of these species).
- Dissolved arsenic in surface, ground and drinking waters (passing 0.45 µm membrane filter).
EnviroGulf Consulting offers the following services to clients:
- Critical review of existing literature, reports and databases on environmental arsenic contamination.
- Design, implementation and execution of surveys to define environmental arsenic contamination and the behaviour and fate of arsenic in the environment.
- Direction of multidisciplinary team (scientists and medical) for combined epidemiological and arsenic contamination surveys.
- Determination of the degree of exposure occurring in communities surrounding point sources of arsenic emission.
- Determination of pathways contributing most to arsenic exposure.
- Determination of relative impact of current emissions versus environmental arsenic accumulated from historical releases.
- Development of statistically designed sampling and monitoring programs.
- Design and implementation of dietary intake and dietary exposure surveys.
- Preparation of technical reports on the above.
The Principal of EnviroGulf Consulting has carried out numerous metal contamination surveys of natural environments and exposed human populations, for example:
- Design and execution of baseline survey to determine arsenic concentrations in the scalp hair of villagers along the Strickland River and Lake Murray, Papua New Guinea (with NSR for Porgera Joint Venture).
- Design and implementation of sampling programs for assessing the scalp hair arsenic concentrations of people inhabiting the Fly River delta, Papua New Guinea and arsenic concentrations in dietary seafood (with NSR for Porgera Joint Venture).
Aquatic biological impact of arsenic present in mining wastes, wastewaters and tailing effluents:
- Lihir Gold Project, PNG - Assessment of the marine biological effects of at-depth marine tailing disposal and near-surface dumping of soft oxidised waste, on the basis of aeration-dilution and bioassay tests, field dump trials and predictions of waste transport and dispersion (with NSR/ Kennecott-Niugini Mining Joint Venture).
- Misima Gold Project Environmental Plan - Assessment of the marine biological effects of at-depth marine tailing disposal and near-surface dumping of soft oxidised waste, on the basis of aeration-dilution and bioassay tests, field dump trials and predictions of waste transport and dispersion (with NSR for Placer (PNG) Pty. Limited).
- Hidden Valley Gold Project Environmental Plan - Environmental impact assessment of potential river biological effects arising from the direct discharge of tailing and/or tailing supernatant (with NSR for CRA Gold Pty. Ltd.).
- Porgera Gold Project Environmental Plan - Assessment of river biological effects of mill tailing and mine waste disposal, based on laboratory aeration-dilution and bioassay tests and river transport modelling (with NSR for Placer (PNG) Pty. Limited).
- Ashanti Gold Mine, Ghana - In: Effects of Mining on the Ghanaian Environment (1991) - River environment impact assessments of five Ghanaian operating mines and formulation of guidelines for draft legislation to minimise the effects of new mining developments on the Ghanaian environment (with NSR for Minerals Commission, Government of Ghana).(NSR/World Bank/ Minerals Commission).
- Prestea Gold Mine, Ghana - In: Effects of Mining on the Ghanaian Environment (1991) - River environment impact assessments of five Ghanaian operating mines and formulation of guidelines for draft legislation to minimise the effects of new mining developments on the Ghanaian environment (with NSR for Minerals Commission, Government of Ghana).(NSR/World Bank/Minerals Commission).
- Ok Tedi Gold Mine, PNG - Three-year assessment of river biological effects of mill tailing and mine waste disposal (Senior Biologist with OTML).