While
the extraction of zinc brings about numerous economic benefits to communities
and countries, it can also have serious ramifications on the enivonment. These
consequences can be categorized into several aspects- water, soil and air.
Environmental Impact on Water
Sources
of groundwater pollution due to the extraction of zinc can come from potential
sources such as include runoff, leachate, and seepage from tailings
impoundments as well as waste rock piles. Zinc is extracted from sulphur
bearing ores, such as zinc blende ore, which is actually zinc sulphide. This in
turns encourages the generation of acid.
Acid in ground and surface water causes it to become acidified, which
causes greater potential for the leaching of heavy metals and facilities the
transport into bodies like rivers or lakes. The existence of bacteria like
thiobacillus ferroxidans are catalyse the oxidation of sulphur-bearing ores which
further encourage the generation of acid. Zinc extraction also increases the
instances for zinc wastes produced during zinc extraction to enter water
bodies. The problem is worsened by abandoned mines as existing waste and
contaminants are not cleared and continue to leak into water bodies unnoticed.
For example, in Wales, Cwm
Rheidol mine, near Aberystwyth, which practiced zinc extraction over the
centuries, has historically discharged large amounts of zinc into the River
Rheidol.
Since
water bodies are polluted with zinc and other contaminants due to zinc
extraction, the pH of the water decreases while the acidity levels
of the water increases, which leads to the pollution of water. When the water
becomes polluted with zinc and other waste products produced during zinc
extraction, it deteriorates the quality of the water. This will affect the
marine life and local communities. Marine life such as fish can die due to the
overconsumption of lead, and pollution of water bodies means it cannot support
marine life. It also has devastating effects on the ecosystems there, affecting
the food chains and biodiversity. Communities who depend on these water bodies
for drinking water and other uses are also unable to continue using the water
there and if they consume the water, they are undesirable health effects like
nausea, respiratory disorders and anaemia.
Environmental Impact on Soil
Discharge,
runoff, leachate, and seepage from tailings impoundments,
pits
and underground workings, as well as waste rock piles, which are results on
zinc extraction. In addition, deposition
of wind-blown particulates from dry tailings impoundments is also a potential
cause of zinc contminatoon in soil. Spills of fuel, flotation reagents,
cleaning solutions, as well as other chemicals such as zinc sulphide used
during the extraction process can also result in zinc contamination of soil. Zinc
one of the most soluble metal elements in soils, and can have toxic impacts on
the soil as it can increase the acidity of the soil, thereby affecting the
fertility of the soil and causing mineral deficiency. This affects the growth
of plants and other organisms in the soil. It has repercussions to soil quality
as well as the organisms in the soil thereby affecting the ecosystem in the
soil. Contaminated soil can have disastrous effects since leakages can affect
the quality and contaminate groundwater and water bodies.
Environmental Impact on Air
dust
from the dry surfaces of tailings impoundments, as well as waste rock piles,
resulting from zinc extraction is the main cause of air pollution due to zinc
mining. Tailings impoundments are not completely covered by water, therefore
being dry enough for wind transport. This gives rise to pollution of water and
soil, whereby due to winds, the contaminants and zinc metals contaminate the
water and soil. Humans can also suffer from health problems like respiratory
problems due to the dust blown in from the dry tailing impoundments.
Example
The
Red Dog extracts zinc from heDeLong Mountains which contains large amounts of
zinc deposists. Leaching of metals from
the ore-rich DeLong Mountains into Red Dog Creek has caused widespread
pollution in water bodies. Red Dog Creek cannot support any fish, partly
because of high metal concentrations. The
contaminated water empties into the Ikalukrok Creek, which in turn empties into
the Wulik River. It is one of the richest
fisheries in northwestern Alaska and hence this results in . Ikalukrok Creek is a wintering ground for
Dolly Varden (Arcticchar), and Wulik River is a major habitat for Dolly Varden
and spawning salmon, and the contaminated water affected the spawning of salmon
and growth of salmon. The Wulik River
also flows to the small Inupiat Eskimo community of Kivalina, about 60 miles
downstream from the mine. This affected communities relying on the water for
livelihood for fishing and as a resource for drinking water from the river. As
a result, they lost their source of water and livelihood.
In
the early 1980s, before mining began, the Alaska Department of Environmental
Conservation (DEC)records showed natural concentrations of zinc in Red Dog
Creek between 7 and 52 parts per million (ppm),
with
one reading of 273 ppm. Summer 1990, where zinc extraction was in full force,
samples from the creek showed consistent zinc measurements
above
100 ppm, with an early July measurement of 970 ppm, which showed that due to
zinc extraction, the amounts of zinc has increased rapidly, over legal levels,
meaning that there was pollution. Alaska Department of Fish and Game
(ADF&G) biologists have identified discoloration in the form of a milky
orange plume of precipitate beginning at Red Dog Mine and flowing
downstream
for about 20 miles. The source of the
water is seepage from the saturated zone associated with the ore body exposed
by extraction, which contains high concentrations of zinc.
Images:
The town of Picher, Okla., is nestled among huge
lead-laced piles of rock. Its population has dwindled to a fraction of its
former size as people gradually move away from the Tar Creek Superfund site
left from years of lead and zinc mining.
Reference:
EXTRACTION AND
BENEFICIATION OFORES AND MINERALS: LEAD & ZINC (USA Environmental
Protection Agency)
