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1.2 Pollutants and Emission Sources 25

vironment:
,
electronics. It can be found in four forms in the en methyl mercury di- and
monovalent ionic mercury, and metallic mercuryThe main anthropogenic sources of lead .
in the environment are from general waste-disposal and industrial activities. Heavy metals
can also be found naturally in the environment.
Source : Industrial acti w vities, The metal industry is responsible for 41.68 aste disposal.
,
t Pb, 8.13 t Cd, 864.25 t Cr 45.77 t Cu, 71.55 t Ni, and 5.09 t As releases directly into
water, annually .
Impact: Immediate threat to aquatic life and human population.
• Inorganic salts and acids
Description : Inorganic salts come from acid mine drainage, industrial processes, and
drainage flow from irrigated areas. Salt accumulation on irrigated soils causes the most
damage and loss in this cateA high proportion of sodium in irrigation water supply gory .
affects plant life adversely. Acids may come from industrial activities or from acid rain and
cause lakes and streams to become acidic and unsuitable for many f ish.
Source : Mining industry drain-of , f w . ater
Impact: Acidification.
• Oil compounds
Description : Petroleum resulting from oil spills often pollutes water bodies. Lar ge-scale
accidents are also an important cause of pollution along shore lines. The most well-known
example is the Exxon Valdez oil spill.
Source : Oil spills. The basic organic chemicals industry is responsible for 82.53 t/yr of
benzene, toluene, ethyl benzene, and xylene (BTEX) direct releases into w . ater
Impact: Water quality deterioration, blocking sunlight from entering water bodies.

• Organic compounds
Description : Numerous compounds are included in this cate. Research is focused on gory
persistent organic compounds such as dioxins and polychlorinated biphenyls. PCBs are a
w found all o group of theoretically 209 different compounds that are man-made, b ut nover
v
olatility
the Earth due to their persistence and relatie v. Due to their stability they ha , v e
v xtensi been eely used in many industrial applications (as hydraulic fluids or cooling liq-
uids) and in open systems (as lubricants or paints). Another significant type of compounds
included in this category is phenols. Phenols and similar compounds are primarily present
w
aste
in refinery and petrochemical waters and are known to hae a significant ne v e v gati
y are well-kno impact on marine life and human health, as thewn carcinogens (IRIS, 1998).
Furthermore, phenols cause an increase in oxygen demand in w and they also impart , ater
a taste to drinking water at very low concentrations of their chlorinated deri es. v ati v
ineries, Primary sources of phenols are in wastewaters from benzene-refining plants, oil ref
coke plants, chemical operations, and plastics production. Another example is aniline
(C H N), which is a colorless oily liquid and is highly toxic. It is used in the manuf acture
6 7
of antioxidants and vulcanization accelerators for the rubber industry, and the manufacture
of dyes and pharmaceuticals (Sharp, 1990; IRIS, 1998). Another common contaminant
type found in water is dyes (F aste w gacsa or et al ., 2004). Synthetic dyes are e v ely xtensi
,
acturing,
used in industry e.g. textile manuf leather tanning, paper production, and food
technology.