The Range of Environmental Concerns - Mining and the Environment: From Ore to Metal - page 536

Air dispersion modelling is the only practical way to factor in all of these inl uences to
predict atmospheric pollution. The model cannot provide absolute values, but it will pro-
vide a good statistical prediction about the pollutant and its movement.

Noise

The three major categories of noise sources associated with mining are (1) blasting;
(2) i xed equipment or process operations such as crushers, mills or ventilation fans; and
(3) mobile equipment used to load and haul ore, mine wastes, and mine products. In par-
ticular the warning sounds made by mine vehicles when reversing are, by design, quite
intrusive and may disturb nearby communities.
Fixed mine installations may include a wide range of equipment including crushers,
grinders, screens, generators, pumps, compressors, conveyers, storage bins, and electrical
equipment. Mobile noise sources may include drilling equipment, excavation equipment,
haulage trucks, pug mills, mobile treatment units, and service vehicles. Any or all of these
activities may be in operation at any one time. Single or multiple effects of sound genera-
tion from these operations constitute potential sources of noise pollution.
Mitigating measures are commonly applied to reduce the effects of noise or the noise lev-
els experienced by receptors. Reduction of sound levels at the point of generation is preferred
to diminishing the effects of the noise at the point of reception. Alternative construction or
operational methods, improved equipment maintenance, selection of alternative equipment,
physical barriers, siting of activities, set backs, and established hours of construction or opera-
tion, are common measures that are successfully used to mitigate adverse noise effects.

Spontaneous Combustion

Spontaneous combustion is most commonly associated with coal deposits, but can occur
at any deposits where chemical reactions of natural elements (such as sulphur) take place
and generate heat. The chemical reactions can be aerobic (that is oxidation), or anaerobic.
For example, coal seams once ignited can continue to 'burn' underground for many years,
despite the absence of air.
Combustion within coal seams (underground or at the surface), in piles of stored coal,
or in spoil dumps at the surface are the most common types of spontaneous combustion.
Coal i res can emerge from spontaneous self-combustion or as a result of extraneous causes.
Spontaneous combustion is commonly a consequence of oxidation processes in coal piles or
heaps. These exothermic processes result in increasing temperatures within the rock pile
which i nally lead to the spontaneous ignition of the coal. Other sources of coal i res are
related to careless mining operations, e.g. underground blasting, welding or grinding or
natural events such as lightning strikes. In developing countries traditional 'slash and burn'
practices to clear land for agricultural are common causes of uncontrolled coal and peat i res.
Nevertheless, although it is illegal, this practice is commonly used to clear land for planta-
tion development ( Case 13.8 ). Uncontrolled coal and peat i res are a major contributor to air
pollution, locally and globally. Of course they also contribute signii cantly to greenhouse gas
emissions. By some estimates the uncontrolled forest, peat, and coal i res in Indonesia in 1997
contributed nearly one-third of the global CO 2 emissions in that year. Less obviously, the
burning of peat increases the subsequent generation of methane from swamps.
The potential for spontaneous combustion of coal depends on its aptitude for oxidization
at ambient temperature. Oxidation is the absorption of oxygen at the coal surface; it is an

Spontaneous combustion is
commonly a consequence of
oxidation processes in coal piles
or heaps.