The quality of water
has to be monitored at regular time-intervals in a very effective and precise
to determine the effect of various pollutantson the living species in water,
which in turn are responsible for the imbalance in the aquatic ecosystem. The
monitoring results actually indicate the quality of water samples under
investigation rather than the water body from where the sample is taken.
Monitoring requires those water samples, which are collected at various
time-intervals and concentrations, so that no change in quality could pass
unnoticed. Train (1979) described the philosophy of the quality of water.
Water Quality Index (WQI) Clasification
and monitoring of parameters: this list is not exhaustive but these parameters
are widely referred in WQI.
1.
pH (units)
2.
Turbidity (NTU)
3.
Temperature (
̊C)
4.
Dissolved Oxygen
(DO)
5.
Conductivity (S/
Cm)
6.
Total Suspended
Solids (TSS) mg/l
7.
Total Dissolved
Solids (TDS) mg/l
8.
BOD5
9.
CODcr
10. Alkalinity
(total)
11. Chemicals
(ppm)
12. Pesticides
(ppm)
13. Oil
and grease (mg/l)
14. Detergents
15. Radioactive compounds (milicurie)
16. Colonies/
ml (bacteria)
17. Color
18. Ammonium
Nitrogen
19. Nitrate
Nitrogen (Am-N)
20. Heavy
metals (ppm)
21. Other
organic and organic contaminants
22. Biota
The
above parameters can be broadly classified into three categories:
3.1. PHYSICO-CHEMICAL PARAMETERS OF
AQUATIC MEDIUM WATER
Hydrogen ion
concentration (pH):
All biochemical reactions are sensitive to the variation of pH. For most
reactions as well as for the human beings, pH value of 7 is considered to be
the best and the most ideal. ICMR Special Report (1975) specifies the limit for
pH value for drinking water at 6,5 – 8,5. Knowledge of the pH of water or
wastewater is useful in determining necessary measures for corrosion control,
pollution control and disinfectant. The hydrogen ion concentration can affect
the ‘taste’ of the water an at a low pH, water taste sour. Extremes of pH or
rapid pH changes can exert stress conditions or kill aquatic life outright.
Even moderated changes from ‘acceptable’ criteria limits of pH are deleterious
to some species. The relative toxity to aquatic life of many materials is
increased by changes in the water pH. Highly acidic waters are harmful to
living organisms exhibiting the pollution characteristics.
Total
Dissolved Solids (TDS): TDS indicates the general nature of
water quality or salinity. Water containing more than 500mg/l. of TDS is not
considered desirable for drinking though more highly mineralized water is also
used where better water is not available. For this reason 500mg/l. as the
desirable limit and 1500mg/l. as the maximum permissible limit has been
suggested for drinking water. Water with high residue is normally less
palatable and may induce an unfavorable physiological reaction in the transient
consumer (Singanan and Soma Sekhara 1974).
Total
Hardness (TH): The contents of calcium or magnesium
salts or both characterize hardness of water. The contents of calcium and
magnesium in potable water ranges from 75-200mg/l. and 50-100mg/l.respectively
(Special Report ICMR,1975). Though hardness has no known adverse effect on
health, some evidence has accumulated to indicate its role in heart disease.
Dissolved Oxygen (DO) and Chemical Oxygen Demand
(COD): These are very important pollution parameters, as
they indicate the degree of pollution in water. DO in water is a quality that,
in appropriate concentrations, is essential not only to keep organism living
but also to sustain species reproduction, vigor and the development of
populations. Organisms undergo stress at reduced DO concentrations that make
them less competitive and less able to sustain their species within the aquatic
environment. One example of reduced DO concentrations have been shown to:
(i)
Interfere with
fish population through delayed hatching of eggs,
(ii)
Reduced size and
vigor if embryous,
(iii)
Production of
deformities in young,
(iv)
Interference
with food digestion,
(v)
Acceleration of
blood clotting,
(vi)
Decreased
tolerance of toxicants,
(vii)
Reduced food
utilization efficiency, growth rate and
(viii)
Maximum
sustained swimming speed.
Likewise other aquatic
organisms in the aquatic ecosystems are effected adversely during condition of
decreased DO. The lethal affect of low concentrations of DO appears to be
increased by the presence of toxic substances such us ammonia, cyanides, heavy
metals like zinc, lead, copper etc., or cresols.
COD is a purely chemical oxidation test
device as an alternate method of estimating the total oxygen demand of the
wastewater. Generally, low DO value indicates high pollution and high COD value
indicates presence of oxidizable organic materials in the water.
Biological Oxygen Demand (BOD): This
is one of the important parameters used in almost all water pollution studies
to evaluate the impact of waste waters on water bodies which are toxic to the
organisms, involved in the biological breakdown of the organic matter.
Materials, which may contribute to the BOD, include carbonaceous organic
materials useable as a food source by aerobic organisms, oxidizable nitrogen
derived from nitrites, ammonia and organic nitrogen compounds which serve as food for specific
bacteria. Other chemically oxidizable materials such as ferrous iron, sulfides,
sulfite etc., may react with DO or are metabolized by bacteria. Water with high
BOD indicates the presence of decomposing organic matter and associated
increased bacterial concentrations that degree its quality an potential uses. A
by product of high BOD concentration can increase algal concentration and
blooms which result from decompotition of the organic matter and which form the
basis of algal populations.
Pollutants which are
measures by the BOD5 test are also measured by COD test. In addition
pollutants which are more resistant to biological oxidation will also be
measured as COD.
Water Quality Index (WQI): Water
quality and its suitability for determining the WQI of the water under
consideration can also assess public consuming. In most of the studies, the use
of water for drinking or personal
hygiene has been treated as the primary consideration. The WQI values indicate
the overall pollution of drinking water. The permissible limit of WQI for
drinking water is 100.
3.2. CHEMICAL PARAMETERS AND THEIR
BIOLOGICAL EFFECTS
These include inorganic salts, heavy
metals and dissolved organics. These effect the nucleic acids(general material)
hence their role in WQI is very important. Therefore the need to determine
their concentrations and their impact. Environmental protection agencies in
every country has set limits to hundreds of chemicals present in water affect
the quality of drinking water.
Transition metals in
permissible concentrations are reported to stabilize the DNA structure through
phosphate bonding, but high concentrations destabilize the structure, braeking
the base-to-base hydrogen bonds. The extent of destabilization by metal ion is correlated with the relative affinity
of metal ions for base vs. photosphate binding (Ghunther and Yang, 1968). Zn is
reported to bind to the bases in addition to the phosphate sites in DNA and
exhibits a high affinity especially the G-C base pair. Zn binds to G3’ p5’
U in a specific manner i.e., only to the 3’-side guanine base at N7 and
when present in excess may lead to the disruption of (biologically active)
stacking structure of DNA (Zeimer et al., 1974). Entry and accumulation of ZN
is shown to generate toxic free radicals (Kim.,1999). Generation of free
radicals may damage DNA and other cellular molecules. Lindahl et al. (1998) has
also showed that Zn stimulated oxygen free radical formation in human
neutrophils. Zn is also reported to completely inhibit DNA ligase I activity
affecting DNA replication resulting in DNA damage (Yang et al., 1996).
Generally,
in the structures of metal-DNA-purine complexes the predominant mode of metal
binding takes place at the nitrogen atoms of the 5-membered (imidazole) ring, N7
and N9 and also (in some adenine complexes) at the N3 and
N1 position of 6-membered (pyrimidine) ring. However, if the local
disordering of the DNA structure occurs, possibly due to metal bonding to N7
with a concomitant perturbation of the hydrogen bonding system, then there is a
possibility of the metal ions to react with these sites resulting in the
breaking of the hydrogen bonds. This may results in the destabilization of the
DNA structure leading to single strand breaks (Katsuyaki Aoki et al., 1988).
3.2.1 Heavy Metals:
It is known that elements are cycled in
nature, but most elements are locked up in the from of insoluble inorganic
compounds. Human activities release many of these substances into the
environment in chemical forms capable of interacting with biota(Kaiser Jamil,
1991). The concentrations of the heavy metals have increased in the lotic
(running water habitats) and lentic waters (standing/ still water habitats) due
to discharge of the heavy metals are extremely useful to humans. For example
cobalt, copper, selenium, molybdenum, etc. but large quantities of them may
cause physiological disorders, many of them are quite serious (Bruce Martin,
1986). In recent years carcinogenicity of metal compounds has attracted a great
deal of attention. Chamicals listed in the IARC (International Agency for
Research on Cancer) monographs revealed their carcinogenicity risk to humans
and an overall evaluation of their carcinogenic potential was reported. Some of
these metal compounds are listed below, others not common in the aquatic
environment include beryllium. The increased demand for metals of all kinds
that followed tha Industrial Revolution was accompanied by the appearance of
metal induced occupational diseases on a large scale.
Manganese
(Mn): It is an essential element which does not occur
naturally as a metal but is found in various salts and minerals frequently in
association with iron compounds. Higher levels of manganese, sometimes found in
free-flowing water are usually associated with industrial pollution (WHO-1984
report). The effect of Mn exposure on health in general is poorly documented.
MnSO4 injections in mice resulted in lung tumors. Manganese
intoxication in humans leads to neurotoxic manifestations including
neurological and neurobehavioral symptoms resembling those in
Parkinson`sdisease. They have also reported the depletion of monoamines i.e.
dopamine and noradrenaline and increase in dopamine (D2) receptors
in the brain of Mn exposed animals.
Zinc
(Zn): It is an essential element for both animals and man and is necessary
for the functioning of various systems. Zinc in water produces undesirable
effects and therefore the concentration of zinc in public water supplies should
be less than 5.0 mg/l., otherwise water may appear opalescent and develop a
greasy film on boiling. It is learnt that toxic concentrations of zinc above
5.0mg/l. causes adverse effect in the morphology of fish by inducing cellular
break down of gills. Zinc plays a role in the synthesis of hemoglobin and
supplementation was found to be beneficial for sickle cell anemia and
thalassemia. Water containing 4 mg/l. of zinc has a bitter or astringent taste
(Cohen 1960). Zinc at concentrations ranging from 0.4 mg/l.-25 mg/l. have been
found to be toxic to several plant species. A maximum permissible limit of
5.0mg/l. has been recommended (ISI Standard, 1983).
Mercury
(Hg): It has been shown that atmospheric deposition of Hg in lakes and rivers
are one of the major sources of mercury pollution. Bioaccumulation an in situ
production is an important source of methyl mercury occurence in the lakes. The
potent toxicity of mercury not only poses increasing threat of contamination of
the environment and ecosystem but also causes world wide concern regarding the
fate of mercury in the environment, especially in aquatic system. The
'Minamata' episode has created a greater awareness regarding monitoring of
mercury in environment (Forstner an Whittman 1983). Mercury induced dysfunction
of endocrine glands is a major toxicological concern in fishes, as it can act
at different levels of endocrine feedback axis (Joy an Kirabugaran, 1998).
Copper
(Cu): Copper is an essential element, as it is required for blood formation in
addition to iron. Many of the well-established biochemical functions of copper
area due to specific cupro-enzymes. Copper concentrations that have no harmful
effects on several aquatic species are 5-15mg/l. In waters with high be able
tolerate higher copper concentrations. A maximum permissible limit of 1.0mg/l.
Is recommended (WHO report, 1975). Menke's disease is a genetic disorder in
infants, which characteriticalli accumulates copper deficiency in the brain and
liver. In the kidnes of such patients copper was detected in a protein fraction
corresponding to metallothionein known-as ceruloplasmin. Copper also occurs in
oxidases, electron transport, crosslinking of elastin, causes anemia and
changes in ossification.
Chromium
(Cr): Hexavalent chromium is known for adverse health effects. Hexavalent
chromium may cause urinary tract cancer and digestive disorders in man. A
permissible limit of 50 ug/l. was set, for hexavalent chromium in domestic
water supplies beyond which it causes health hazards. Epidemiological studies
have shown that occupationally exposed workers to chromate compounds in
refining ferro-alloys, electro-plating or pigmet production factories have an
increased risk of lung cancer and mortality. Chromium in the effluents of
leather industry is known to contaminate aquatic life. Chromium-VI was reported
positive in Salmonella typhimurium assay, while that of Cr-III was negative.
Chromium occurs in RNA-protein complexes, its occurence in the animals affects
growth resulting in reduction of life span and decrease in glucose tolerance.
Nikel
(Ni): attention to the carcinogenecity of nickel was drawn from an observation
of increased incidence of lung and nasal cancer in a nickel refinery factory
which uses the Mond process. The process involves conversion of nickel
compounds into geseous nickel carbonyl. In rats an hamsters, inhalation of
metallic nickel and nickel compounds have been reported to induce malignant
sarcomas or pulmonary cardinomas. The index of carcinogenecity of nickel is as
high as that of chromium.
Aluminum
(Al): Present acidification of our environment solubilizes large amount of
aluminum (Savenson et al., 1994). Aluminum interferes witg phosphate
metabolism, reduces bioavailability of ATP and casein; inhibit certain enzymes
by forming complexes witg them. Evidence of proposed physiological effects of
aluminum include intreraction with DNA, disturbance of phosphate metabolism,
interaction with cell wall and cell membranes and induction of calcium
deficiency (Viola et al., 1980; Bradley et al., 1971; Vierstra et al., 1978).
Aluminum is commonly used in food processing, storagd, pharmaceuticals, and as
phoshate binders. Prolonged exposure to Al can lead to a progressive fracturing
osteodystrophy, and alteration in myocardial calcium transport.
Lead
(Pb): Man's continuous utility and exploitation of lead smelters, battery
manufacturers, paper an pulp industries, boat and ship fuels and ammunition
industries are important sources of lead contamination. Lead is also used in
antiknock gasoline additives. In general the industrial uses of lead and its
hazardous effects on human systems are well documented. The toxicity of lead to
humans has been identified as a cause of brain and kidnes damage. Lead and lead
poisoning in antiquaity has been reported by Nriagu (1983). In children, itu
may result in mental retardation and even convulsions in lateq life. Lead is
also responsible for liver damage and anemia. (It may be noted that water
intake may add to 10-15ug of lead per day). The permissible limit for lead in
the drinking water is set as 0.05mg/l. (WHO, 1984).
Cadmium
(Cd): Among the divalent cations present in the environment cadmium is reported
to be the most toxic metal pollutant and is associated with the disorders of
lungs, kidneys and liver. Main sources of cadmium effluents are the cladding
industry where it is used in protective metal coating, nuclear reactors,
alkaline cells an alloy industry. Cadmium enters the bodz through some natural
foods, cigarette smoking and polluted cells. Many harmful effects of cadmium on
humans include hypertension and renal changes, which has been reported by
several workers (Roels et al., 1993). The permissible limit of cadmium in
drinking water is set as 5ug/l. and the maximum permissible limit discharge
levels for the effluents as 2mg/l. (WHO, 1984).
Arsenic
(As): Of all the heavy metals, arsenic has received a great del of attention
due to its toxicological effects on human system. Arsenic enters the aquatic
environment in the dissolved form through industrial discharges. Such as from
metallurgical industry, glass and ceramic industry, pesticide manufacturing,
and petroleum refining industries etc. Besides being proven carcinogenic,
inorganic arsenic, when it gets deposited on or bound to tissues, leads to
gastro intestinal cardiovascular, dermal and respiratory disorders,
hyperpigmentation and peripheral neropathy. The uppermost safety limit of
arsenic in drinking water is set as 0.05mg/l. (WHO, 1984).
3.2.2 Pesticides
The
aquatic environment is countinuously being contaminated with toxic chemical
generated by man’s industrial, agricultural and domestic activities.
Pesticicdes are one of the major xenobiotic substance that have been used for a
longer period of management of pests in agricultural fields and control of
vectors in public health operations. Most of the insecticides are so
hydrophobic that they can easily be absorbed by soil particels and can migrate
to natural water systems such as rivers, lakes and ponds through the run-off,
causing severe aquatic pollution. Consequently these xenobiotic moluculers have
been found in natural water systems and they have a great impact on the
environmental quality. It has been shown by Sevenson et al. (1994) that
pesticides become accumulated in aquatic organisms and can enter the food
chain. Primarily they affect the metabolism, which is concerned with oxygen
consumption in aerobic respiration. The acute toxicity bioassay of many
insecticides for aquatic organisms has been reported. A lot of work has been
done to know the effect of pesticides upon aquatic organisms. Which has paved
the way for indicating the levels of water pollution.
In
the past few decades a number of new problems have arisen i.e reentry of
pesticides in fields, acid rain, pesticide (aldicarb) in ground.
3.3
Oil, Grease, Petroleum and Detergents
Oil,
grease and petroleum pollutants are common. Typically they are run-off leaks
and discharges from dairy and other industries, often small-scale, but
occasionally refinery eflluents also effect big rivers. Many oils are toxic.
The subsequent break down products of oil provides additional organic input
e.g. oil in streams and in ponds, experimental oiling manipulations, effect
under ice and fish avoidance reaction. Hydrocarbons of petrochemical products
are also known to inhibit a large number of enzymatic reaction. Oil and grease
being immiscible in water and low in density, the float and form a slime on the
surface affecting the penetration of light and precluding gaseous transactions through water surface. Such
films are disastrous to the aquatic life as it impairs their normal reespiratio
and movement . numerous nektonic animlas come to the surface to breathe and the
film of oil-grease at water-air interface adversely affects them. Oil-grease
also bring about clogging of stomatal openings of macrophytes. The major
problems associated with oil-grease is the loss of hydraulic capacity and its
subsequent accumulation in the pump station preventing pumps frpm operating at
their assigned level. This may create flooding or an overflow of raw waste
water to any nearby water sourse. Oil-grease cause health hazards and
interferes with activated sludge digestion process. Detergent are lumped
together with oils more by associantion, rather then occurring independently,
thus resulting in toxic nature. A more specific danger arises in water
treatment plants, where slippery detergents can make conditions very hazardous
for workers. The aromatic sulphonates of detergent are found to be carcinogenic
in nature.
3.4
Thermal Pollution
Various
industrial processes may untilize water of cooling and resultant warmed water
has often been discharged into streams or lakes. Coal oil fired generators and
atomic energy plants cause large amounts of waste heat which is carried away
as hot water and cause thermal pollution
or calcification (warming). Thermal pollution products distincy changes in
aquatic biota. Water body at 30-350C is essentially a biological
desert and many game fish require temperatures of less than 100C for
successful reproduction , although they will survive above that temperature. A
temperature rise of 100C will double the rate of many chemical
reactions and also so the decay of the organic matter, the rusting of iron and
the solution rate of salts are also accelerated by calcification. Since the
rate of the exchange of salts organisms increases, any toxins are liable to
exert greater effect and temperature fluctuations are likely to affect
organism. Thermal pollution thus can exert a destructive effect on aquatic
ecosystems. The hightly suspended solids of thermal agents found to affect
microbial flora.
Organisms that can tolerate thermal
change must therefore be able to tolerate rather drastic changes in enzyme
modulator and enzyme substrate affinities, or they must somehow adjust their
thermal sensitivities to suitable levels,. Of these two options the latter
seems to be more frequently observed. In the case of AMP regulation of fructose
biphosphatase studies and its homologues form organisms living in widely
differing physical environments indicate that AMP binding is indeed strongly
compensated with respect to temperature and pressure (Hochachka et al., 1988).
Various workers have also reported
thermal pollution due to radioactive wastewater in some parts ofthe globe. The
operational release of warm waters from nuclear plants containing radionuclides
as contaminants effect aquatic organisms as the toxicity of these will be
several million times more harmful than chlorine.
3.5
Biological Parameters
Water
bodies are subject to important changes in their microbial quality due to
dischange of sewage into them. Sewage contains a wide varienty of pathogens,
which may pose a health hazard to the humman popullation. Same of the
microorganims serve as bioindicators due to their predominant presence over
other species: these include:
·
Coliform
·
Fecal coliforms
·
E. colli
·
Fecal
streptococci
·
Spore of
clostridia
Some obigate
anaerobes or their stages seem to the most suitable indicators of water
pollution owing to their availability to survive outside the intestinal tract.
Pathogens:
Pathogens
include viruses, bacteria, protozoa, fungi and metazoan animal parasite such as
flukes and tapeworms. The prime concern of these organisms being their direct
health risk to hummans. Their presence is often associeted with other polluting
effluents, notably sewage. Some parasites are water borne ineffective stags,
free living or carried by aquatic vector ingested when a terget on their own
accord. The diseases can be very dangerous such as bilharzia caused by a genus
of trematode worms parasitic in humans. Treatment of dangerous waters, such as
bilharzia sites, may involve potensial pollutants, in the case mollucsicides.
In developed countries pathogen control is primarily a matter of adequate
sewage treatment. Anthropogenic discharges containing pathogens that threaten
wild life are not a common problem though fish diseases may be spread due to
aquaculture effluent.
Human,
recreational and domestic wastes
Besides
noxious chemicals and other effluents, domestic waste themselve can be very
destructive by their presence. Sometimes this is obvious from the litter we
leave behind. Litter and domestic wastes accumulated close to human dwellings
can cause more disturbances since clean up and control measures tend to become
difficult to implement.
This
complication arises only because straightforward identification of the source
is impossible. For the natural weather conditions scalter these substances and
at discomfort. Teh added twist to this pollution is that it stems largely from
the very great pleasure we gain from the countryside in which water plays a
great part. The nicer asite, more and more poeple are drawn there, so the
preseure can be disproportionstely worse at some of the most beautiful
areas.
The toxic and pathological effect of
above water pollutans are tabulated in Taebl II.
Tabel
II. Seource
and caracteristics of toxicants that cause toxic effect through the medium of
water
|
Industry
|
Toxicant
nature
|
Potential
effect
|
|
Agriculture
and Sericulture
|
Pesticides,
herebicides/insecticides, nitrates,inorganics
|
Neuorological
disorders, nitrosamine type carcinogens, toxic to bacteria and fish, enter
the food cycle of human beings
|
|
Paper and
pulp
|
BOD, Odor,
organic and inorganic contamination
|
Aquatic
pollution, toxic
|
|
Explosive or
ammunition, chemicals
|
TNT, aromatic
compounds, RDX
|
Highly toxic
or lethal effect
|
|
Hospital
|
Microbes,
disinfectants
|
Spread of
diseases, health hazards
|
|
petrochemicals
|
hydrocarbons
|
Inhibit a
large number of enzymatic reactions
|
|
Leather
|
Chromium
|
Carcinogens
|
|
Pharmaceutical
and bulk drugs
|
Drugs and
antibiotic
|
Generate
resistant microbial organisms
|
|
Phosphoric
acid
|
Fluorides or
organophosphates
|
Bone related
or neurological disorders
|
|
Battery
|
Lead,
cadmium, nickel
|
Neurological,
brain. Bone and enamal damage
|
|
Plastics and
resins
|
Penol,
formaldehyde
|
Highly
dangerous, respiratory disorder
|
|
Textile or
dye
|
Dyes, heavy
metals
|
Hazardous,
genotoxic
|
|
Sewage
plants
|
Heavy
metals, microbes
|
Gastro-intestinal
deseases
|
|
Other
industries
|
Organic and
inorganic effluennts(contaminats)
|
Immune
system suppression allergins, diseases
|
The
types of pollutans generated by various activities of humans are listed in the
above tabel II. This also indicates the kinds of toxicants a particular
activity produces and the effect, which are manifaested in the living beings as
result of exposure to these toxicants. One is aware that as literature is
mounting in these areas, there is more information of these activities in books
and papers related to pollution.
However, in Tabel II there is a
brief indication of effect produced by chemical toxicants, which are the
outcomes of the particular industrial (man-made) acitivity. The health of
humans is grossly effected by the presence of these toxicants in his close
environments. The toxic nature of the effluents or the produts of industrial
activities, which are of direct benefit to man by way of provinding food and
clothing, papers and energy, medicines and housing, plastics and textiles etc.,
have an inderect effect on human health. Younger generations are much more suscaptible.
Occupational workers who are directly involved in the production activities are
the target group and suffer the most. Some of the workers are exposed to the
toxicants for long periodes of time and lethal effects as described in Tabel II
are noticable. Tabel II particularly lists the effects on humans rather than on
ecosystems or other biota. Even than the parameters presented in Tabel II are
not exhaustive but representative. It is useful to understand that these
effects can be traced back to the causative agent i.e. toxicant and the
toxicant can be traced back to industrial activity. Since the entire system in
linked to one another it relates directly or indirectly to environmental
quality monitoring.
3.6. Plants which are indicators of
water quality
They can also be found in nature.
Some of which are listed in Tebal II
Tabel
III .
Some aquatic plant species as Ecological Indicators:
|
Name of the
species
|
Indicator of
|
|
Utricularia,
chara, wolffia, hyacinth
|
Water
pollution
|
|
Atriplen,
salsola and saved
|
Salinity
|
|
Hydrilla,
ceratophyllum
|
Hardness of
water
|
Among the plant kingdom, there are
several species of plants, which are indicative of the environment in which
they grow. It has long been known how plants of the aquatorial region differ
from plants of the Arctic and Tundra regions of the globe. Plants diversity and
distribution on the planet earth depends on its eco-environment. Even though
this conpect ofplant indicators is not new, but the recognition that plants can
indicate environmental health is new. In the tabel II only few species have
been listed which are widely recognized as pollution indicator aquatic plants
the list is ever increasing and more information is included in the vegetation
due to the pollution effect in that region as compared to the non-industrial
areas.
The tables below IV and VII (p.107)
are the refrence standarts of chamicals, which include the allowable limits of
the prensence of these substances in the environments. Any quantity beyond
these limits is considered seriously by
the regulatory authorities.
Tabel
IV.
Maxium allowable concentrations of some pesticides in aquatic medium
|
Pesticides
|
(mg/l)
|
|
Endrin
|
0,02
|
|
Lindane
|
0,4
|
|
Methoxychlor
|
10,0
|
|
Texaphene
|
0,5
|
|
2,4 –
Dicholorophenoxyacetic acid
|
10,0
|
|
2,4 -
Dinitrotoluene
|
0,13
|
|
2,4,5 –
trichlorophenoxypropionic acid (silvex)
|
1,0
|
Some constituents of a water may be
unstable and may have the pontential to cause an explosion at any stage of
waste management cycle. The EPA has developed to toxcity characteristic test to
identify wastes that are likely to leach hazardous constituents into the ground
water from improperly managed facilities. The leach test stimulates natural
leaching action that may occur in a landfill.
The contaminant may be considered
toxic if their concentration exceeds the respective value given in Appendix-I.
It is likely that as more test results become available, the list will expand
(Syed E. Hassn, 1996).
Under the safe drinking water Act of
USA (1986) a long list of permissible concentrations of chemicals and metals is
defined. A large number of chemicals and related substances are regulated by
the Act, and the liability burden under the law is indeed very serious. The
Toxic Substances Control Act (TSCA) of 1976 was aimed at regulating chemicals, hence a TSCA Registry was
established. Under this Act any new chemical manufactured or imported has to be
registered. Following this information on the environmental fate of a chemical and
associated health effect have to be furnished. Then the decision of its use in
the environment will be revealed.
The importance of quality monitoring
in the aquatic eco-environment cannot be less emphasized in view of the fact
that there are innumerable water-borne diseases and factors affecting
environmental health directly and animals and plants indirectly. A clean
environment is the way to good health, and safe drinking water is highly
desirable in underdeveloped and developing countries around the globe. The
recycling of some of the hazardous environment pollutants through tropic levels
of food chain, in low doses leads to chronic toxicity and delayed neurotoxicity, these events are described in
the next chapter on impact of pollutants.
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