Organic and inorganic pollutants
Dr. Kiran Hina
( B )
Organic and inorganic pollutants
pollution occurs when large quantities of organic compounds. Which act as
substrates for microorganisms, are released into water-cources. During the
decomposition process the dissolved oxygen in the receiving water may be used
up at a greater rate. It can be replenished, causing oxygen depletion and
having severe consequences for the stream biota. Organic effluents also
frequently contain large quantities of suspended solids which reduce the light
available to photosynthetic organisms and, on settling out. Alter the
characteristics of the river bed, rendering it an unsuitable habitat for many
invertebrates. Toxic ammonia is often present. Organic pollutants consist of
proteins, carbohydrates, fats and nucleic acids in a multiplicity of combinations.
Raw sewage is 99,9 per cent water, and of the 0,1 per cent solids, 70 per cent
is organic (65 per cent proteins, 25 per cent carbohydrates, 10 per cent fats).
Organic wastes from people and their animals may also be rich in
disease-causing (pathogenic) organisms.
What are the origins of
pollutants originate from domestic sewage (raw or treated), urban run-off,
industrial (trade) effluents and farm wastes. Sewage effluents is the greatest
source of organic materials discharged to freshwaters. In England and Wales
there are almost 9000 discharges releasing treated sewage effluent to rivers
and canals. And some hundred more discharges of crude sewage, the great
majority of them tot the lower, tidal reaches of rivers or, via long outfalls,
to the open sea. It has been assumed, certainly incorrectly. That the sea has
an almost unlimited capacity for purifying biodegradable matter.
Origin and Occurrence
A wide range of organic substances are
produced by human society and appear in discharges such as sewage, storm-water
and industrial discharges. These discharges can represent major sources of the
pollutant substance. For example the concentration of organic pollutants in
sewage is low. But the volume is large making it a major source of many
pollutants. A similar situation applies with storm-water where these substances
often originate from discharges from motor vehicles on to road surfaces. They
are subsequently swept into waterways by storm run-off. Motor vehicles are
major sources of petroleum hydrocarbons, polycyclic aromatic hydrocarbons and
dioxins. Which are often discharged to the atmosphere in particulate form.
These particulates are deposited close to busy roadways leading to
contamination of urban soils and potential human exposure. Urban and industrial
wastes are often, either currently or in the past, disposed directly into pits
dug into the ground which leads to contamination of the soil and in some cases
the adjacent ground water. Outside urban areas agricultural activities are the
major sources of pollutants. The growing of crops often involves the release of
pesticides into the environment. Which can result in the contamination of
waterways and soils, as well as the urban environment. Imaginably the most
spectacular example of contamination of the environment is due to the
accidental spillage of petroleum. Over the years many disasters of this kind
have occurred releasing tens of thousands of tonnes of petroleum into the
and Properties of Organic Pollutants
The many types of organic pollutant can be
placed into three general classes:
and phosphorus compounds or
the major group is the hydrocarbons and related compounds, which comprehends
such compounds as DDT, the dioxins and the polycyclic aromatic hydrocarbons
(PAHs). These compounds contain the elements of carbon and hydrogen, with some
containing chlorine and oxygen as well. There are a limited number of types of
chemical bonds present, which are principally C-H, C-C, C-Cl, C=Cand C=C
(aromatic). All of these bonds are relatively stable and have limited polarity
and this property is then conferred onto the related compounds. Some typical structures
are shown in Figure 1.
As a result of the low polarity, these
compounds are, in over-all, soluble in fat (i.e. lipophilic), unwell soluble in
water and persistent in the environment. Thus, they will be sorbed by sediment
and bioaccumulated by organisms (in fatty tissues) and have low concentrations
in water and air. The lipophilicity of compounds can be measured in the
laboratory as the octanol-water partition coefficient ( ow K ). The higher the
ow K value the higher the lipophilicity. This class contains the most toxic
organic compound of abiotic origin, 2,3,7,8-tetrachlorodibenzo(1,4)dioxin, also
known as 2,3,7,8-TCDD or TCDD.
The group comprising oxygen, nitrogen and
phosphorus compounds is very diverse but as a over-all rule it contains
compounds with moderately high solubility in water, low fat solubility and
relatively low determination in the environment. This is due to the presence of
bonds with relatively high levels of polarity due to carbon and other atoms
being attached to oxygen, nitrogen or phosphorus conferring a high level of
polarity onto the related compounds. As a general rule the ow K values are
relatively low, much lower than those of the hydrocarbons. In totaling, such
bonds are relatively easily dissolved by environmental processes and
consequently such compounds are less persistent.
The substances in this group only infrequently
form residues in the environment due to their low persistence, low accumulation
in sediments and low bioaccumulation volume in organisms. The organometallic collection
is probably the least important from an environmental perspective and includes
compounds that are combinations of metal, such as lead and tin, with organic
components based on carbon.
Figure 1: Chemical structures of some well
known organic pollutants
Pollutants and Endocrine Disruptors:
There are a group of chemicals which have stood
particular environmental problems due to their fat solubility, bioaccumulation
potential and environmental persistence as well as practice patterns. These are
discussed as Persistent Organic Pollutants (POPs). These substances are often
distributed over long distances up to a global scale. POPs are normally members
of the hydrocarbon and related compounds group (see Figure 1). And include such
compounds as DDT, PCBs and the dioxins (see Persistent Organic Wastes, Pathways
of Organic Chemical Contamination in Ecosystems). The POPs have been associated
with adverse biological effects often related to disruption of the endocrine
system in organisms. The endocrine system is a complex array of glands and
other organs that control hormone levels within organisms. When POPs are taken
up by an organism, even in very low concentrations. They can disrupt the
endocrine system causing hormonal changes that can result in reproductive
problems. In accumulation these compounds are often carcinogens. There are some
examples of the adverse effects of POPs on reproductive success in the natural
environment. Perchance the best known is the effects of DDE on the reproductive
success of birds. In current times the number of endocrine disrupters has
increased dramatically and now includes most organic pollutants or the range of
other substances. In addition there have been reports of adverse effects. Usually
related with reproduction, in relationship to humans as well.
The effects of organic
effluents on receiving waters:
an organic polluting load id discharged into a river. It is gradually excluded
by the activities of microorganisms in a way very similar to the processes in
the sewage treatment works. This self-purification involves sufficient
concentrations of oxygen. And involves the breakdown of complex organic
molecules into simple in organic molecules. Dilution, sedimentation and
sunlight also play a part in the process. Attached microorganisms in streams
play a more role than suspended organisms in self-purification. Their
importance increases as the quality of the effluent increases. Since attached
microorganisms are already present in the stream. Whereas suspended ones are
mainly supplied with the discharge.
Effects on the biota
pollution affects the organisms living in a stream by lowering the obtainable
oxygen in the water. This causes reduced fitness. When severe, asphyxiation.
The increased turbidity of the water decreases the light available to
photosynthetic organisms. Organic wastes also settle out on the bottom of the
stream. Altering the characteristics of the substratum.
is Inorganic Pollution?
Pollution are things found naturally. But because of human production of goods
have been altered to drastically increase the amount of them in the environment
(some examples include arsenic, lead, as well as many different air pollutants).
of Inorganic Pollution:
first experiment was aimed at figuring out exactly how Organic and Inorganic
pollution effect soil acidity (PH level). Which can have a drastic effect on
the environment; an example is that in acidic ponds algae grows much more
easily which can literally suffocate fish, killing them. For our second
experiment we are trying to see how plant life essentially grows in the soil. That
has pollutant in it that will make its PH level lower than neutral, with a
normal plant planted in regular soil as the control.
Classification of Inorganic chemical pollutants
Fig-2Classification of Inorganic chemical pollutants
Lists some of the
pure-inorganic chemical pollutants and their harmful effects.
Pure inorganic chemical pollutants
a contributor to Alzheimer’s disease
highly toxic to humans and is chronic, or cumulative in human and animal
the gastrointestinal tract and the central nervous system
toxic to fish and aquatic life and various plants and inhibits photosynthesis
in terrestrial plants
approximately 1 to 4 mg/l, can be toxic to plants and at approximately 30
mg/l, can have physiological effects on animals and humans.
metabolism and is quite toxic to animals and humans; it is cumulative in the
kidney and liver organs and can cause death.
levels above 100 mg/l is highly toxic to animals and humans and can cause
vomiting and liver damage.
be fatal at 8 mg/l. At low pH, CN forms hydrogen cyanide (HCN), which is a
highly toxic, almond smelling mustard gas.
is cumulative in animal and human organs; with concentration greater than 0,5
mg/l causes lead poisoning. Plumbism is a disease caused by lead that affects
the central nervous system of animals and humans.
tests have been developed to indicate water quality based on chemical
characteristics. That can be simpler, less expensive or more indicative of
water quality than a chemical compounds tests. CaCO3 is used as
a standard for several of the indicator tests since its molecular weight is 100.
And calculations are simplified. Table-2 lists description of some of the
Chemical Indicator Tests.
2Chemical Indicator Tests (Water Quality control Handbook)
an indicator of capacity of water to react with a strong base to a designated
pH. Titration with a standard alkali solution to an end point of 3.8 pH is
used for most wastewaters. Acidity is reported in mg/l of CaCO3.
primarily a function of the carbonate(CO3), bicarbonate (HCO3)
and hydroxide (OH) content of wastewater. Titration with a standard acid to
an end point of 8.3 pH is reported as phenolphthalein alkalinity and
titration to an end point of approximately 4.5 is reported as total
alkalinity. Alkalinity is measured in mg/l as CaCO3.
a quantification of the ability of water to carry an electric current. Most
conductivity tests are accomplished with an instrument.
generally a measure of the capacity of water to precipitate soap. Hardness is
either calculated from the results of separate calcium and magnesium tests or
is determined from a colour change when titrating a sample with
ethylenediaminetetracetic acid (EDTA)
substances that are soluble in trichlorotrifluoroethane. These tests will
include the presence of certain sulfur compounds, organic dyes and
chlorophyll that is not volatilised.
used to indicate the intensity of the acidic or basic character of a
a measure of the dissolved salts in solution. mg/l
pollutant limitations are shown in Table -3.
Pollutant Limitations (Water Quality control Handbook)
& Widlife protection
in soft water
1100 ?g/l in hard water
in soft water
12 ?g/l in hard water
96 hr LC50
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