Environmental risk of mining - Environmental Deterioration and Contamination: Problems and their Management - page 114

different elements of the natural environment at a time (atmosphere, hydrosphere,
lithosphere, biosphere, etc.) and result in different outcomes (alienation of affected
areas, landscape deterioration, physical damage, chemical and radioactive contamina-
tion, thermal, radiation, acoustic influences and other physical effects). These negative
impacts become apparent at both local/regional levels and world-wide.
The environmental problems caused by the extraction, utilization, processing of
nonrenewable energy and raw material resources are discussed below.
2 NONRENEWABLE RESOURCES
The use of renewable resources is not sustainable, and has gradually worsened in the
history of mankind with regard to population density and extent of industrialization.
Greater amounts of renewable resources are used than naturally produced, grown
or generated (deforestation, overgrazing, over-fishing, over-hunting, etc.) so that the
input and output are not equal; recharge is slower than exploitation. Nonrenewable
resources are generally defined as natural resources, which cannot be produced, grown
or generated at all, or only at a negligible rate compared with exploitation. This means
that there is only output, no considerable input, and once used there is no more reserve.
All mined resources such as metals, uranium, coal, oil, gas and various other materials
are examples of nonrenewable resources. Mining of these resources has caused and is
still causing severe environmental problems all over the world. Mining operations can
be grouped into five major categories in terms of their respective resources. These are
oil and gas extraction, coal mining, metal ore mining, nonmetallic mineral mining and
quarrying.
2.1 Oil and gas production
Drilling for oil and gas is disruptive to the earth's crust. Even if its footprint is less
than that of mining, the potential environmental impact is high. Apart from drilling,
oil and gas production can impact the environment during routine production oper-
ations. Large quantities of water and fine sediment are often withdrawn from wells.
These materials are generally separated before transportation of the product from the
wellhead to the refinery or gas conditioning plant. Water may be contaminated with
both metals and organics from the formation, and is also contaminated by additives
that are added to aid the flow of oil or to help separate desired materials from undesired
ones. Some of the additives include biocides to cut down on the growth of bacteria that
can clog pores and contribute to toxic hydrogen sulfide formation, corrosion inhibitors
to cut down on the formation of scale, surfactants to retard foaming, flocculants to
help settle suspended materials during separation processes. As the more easily acces-
sible deposits of oil and gas are depleted, production will become more difficult, and
the risks will increase in proportion.
Special risks are associated with offshore drilling operations. Deposition of drill
cuttings on the sea floor can have adverse effects on the marine ecology. Blowouts are
extremely difficult to control, see the case of Deepwater Horizon. In April 2010, a gas
release and subsequent explosion occurred on the Deepwater Horizon oil rig working
on the Macondo exploration well in the Gulf of Mexico. Eleven people died and many
others were injured. The fire burned for 36 hours before the rig sank, and hydrocarbons
leaked into the Gulf of Mexico before the well was closed and sealed. The accident