CHAPTER ONE 1.0 INTRODUCTION/LITERATURE REVIEW All cells, at least those that are metabolically active, contain approximately 85.95% water, it is therefore a truism to state that any environmental factor that affects, the activity, structure or physical state of water poses a threat to life in one’s health. Oceans have historically been the dumping grounds for the wastes from society. Fortunately, this view has changed and regulations have become much more stringent, but the effects of the past still lingers. Pollution has been very damaging to aquatic ecosystems, and may consist of agricultural, urban, and industrial wastes containing contaminants such as sewage, fertilizer, and heavy metals that have proven to be very damaging to aquatic habitats and species. Many of the pollutants entering aquatic ecosystems (e.g., mercury, lead, pesticides, and herbicides) are very toxic to living organisms (USEPA, 2007). They can lower reproductive success, prevent proper growth and development, and even cause death. The organisms that are most 1
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CHAPTER ONE
1.0 INTRODUCTION/LITERATURE REVIEW
All cells, at least those that are metabolically active, contain approximately 85.95% water, it
is therefore a truism to state that any environmental factor that affects, the activity,
structure or physical state of water poses a threat to life in one’s health. Oceans have
historically been the dumping grounds for the wastes from society. Fortunately, this view
has changed and regulations have become much more stringent, but the effects of the past
still lingers. Pollution has been very damaging to aquatic ecosystems, and may consist of
agricultural, urban, and industrial wastes containing contaminants such as sewage, fertilizer,
and heavy metals that have proven to be very damaging to aquatic habitats and species.
Many of the pollutants entering aquatic ecosystems (e.g., mercury, lead, pesticides, and
herbicides) are very toxic to living organisms (USEPA, 2007). They can lower reproductive
success, prevent proper growth and development, and even cause death. The organisms
that are most directly and adversely affected by toxic pollutants consist of larvae, eggs, and
other organisms that live at the surface or near the bottom of aquatic habitats where
pollutants tend to settle. Filter feeders (e.g., clams, and mussels) and other organisms
higher up in the food chain (e.g., swordfish, tuna) are also affected by the presence of
toxicants. Filter feeders and predatory fin-fish are not directly affected by the presence of
toxic chemicals in the water column or sediments, instead they bioconcentrate and
bioaccumulate the toxicants. For example, humans, animals, and birds have been known to
suffer from mercury poisoning, lead poisoning, and other neurological diseases from eating
fish and shellfish that are contaminated with high levels accumulated toxicants.
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In addition to toxic pollutants, increased nutrients, especially nitrogen and phosphorus,
from city sewage and fertilizers from agricultural areas (e.g. animal feed lots) have also
proven to be very damaging to aquatic ecosystems. Certain levels of these nutrients are
known to cause harmful algal blooms in both freshwater and marine habitats. In turn, algal
blooms impact aquatic biodiversity by affecting water clarity, depleting oxygen levels, and
crowding out organisms within an ecosystem. In some instances algal blooms have
produced neuro-toxins that have led to species die-offs and illnesses such as Paralytic
shellfish poisoning. Other pollutants affecting biodiversity in aquatic ecosystems are solid
pollutants like plastic bags, plastic rings, abandoned fishing gear, and other man-made
materials that result from garbage dumped from shore and ships. Trash and debris of this
nature floating in aquatic environments, have been known to entangle and even kill marine
mammals and birds. Animals such as sea turtles have often died through ingesting bits of
plastic and other discarded materials. In addition, abandoned fishing gear such as lobster
pots and nets are self-baiting and will continue to catch and kill fish and other organisms for
years after the gear has been discarded or lost (USEPA, 2007).
1.1 INLAND WATER
Inland water systems can be fresh or saline within continental and island boundaries. They
include lakes, rivers, ponds, streams, groundwater, springs, cave waters, floodplains, as well
as bogs, marshes and swamps, which are traditionally grouped as inland wetlands. The
biodiversity of inland waters is an important source of food, income and livelihood,
particularly in rural areas in developing countries. Other values of these ecosystems include:
water supply, energy production, transport, recreation and tourism, maintenance of the
hydrological balance, retention of sediments and nutrients, and provision of habitats for
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various fauna and flora. But since all terrestrial animals and plants depend on fresh water,
the boundaries between aquatic and terrestrial are blurred. At the species level, inland
water biodiversity generally includes all life forms that depend upon inland water habitat for
things other than simply drinking (or transpiration in plants). Besides the obvious life living
within water itself (e.g., fish), this also includes many “terrestrial” species of animals (e.g.,
water birds), semi-aquatic animals (e.g., hippopotamus, crocodiles, and beaver) and plants
(e.g., flooded forest, mangroves, vegetation associated with the margins of water bodies).
The majority of amphibians, for example, breed in fresh water. As for all biodiversity, for
inland waters the concept includes diversity at the species, genetic and ecosystem level.
Species which are restricted to inland waters (e.g., freshwater fish) cannot move easily
between different areas. Inland waters are therefore characterized by high endemicity of
freshwater species – for example between different lakes or the upper reaches of sub-
catchments of rivers, often even where located physically close to each other. This is also
reflected in high levels of genetic diversity. Most importantly, ecosystem diversity (including
hydrological and physical diversity within the landscape) is an extremely important aspect of
the biodiversity of inland waters. This ecosystem diversity is very complex and includes both
aquatic and terrestrial (landscape) influences; maintaining it is critical to maintaining
ecosystem services. Also, human interventions in the ecosystem tend to deliberately reduce
this diversity (e.g., by modifying the form, and therefore function, of river channels and/or
hydrology).
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1.2 LAGOON POLLUTION
Lagoons have a less well defined drainage network and larger open areas and are usually
shallow—often less than 2 m (6.5 ft) deep. A raised ridge, or sand barrier, is characteristic
of lagoons. This feature was formed during the interglacial stage of the Pleistocene Epoch,
some 80,000 years ago, when sea shorelines were about 6 m (20 ft) above present average
levels. During the last ice age, fluvial and atmospheric processes eroded the earlier coast.
When sea levels rose anew, the areas behind the barrier were once again flooded. Lagoons
are present on all continents (Encarta 2008). Water pollution may come from point sources
or nonpoint sources. Point sources discharge pollutants from specific locations, such as
factories, sewage treatment plants, and oil tankers. The technology exists to monitor and
regulate point sources of pollution, although in some areas this occurs only sporadically.
Pollution from nonpoint sources occurs when rainfall or snowmelt moves over and through
the ground (USEPA).
1.2.1 POINT SOURCE POLLUTION
Point source pollution refers to contaminants that enter the lagoon through a discrete
conveyance, such as a pipe or ditch. Examples of sources in this category include discharges
from a sewage treatment plant, a factory, or a city storm drain. The U.S. Clean Water Act
(CWA) defines point source for regulatory enforcement purposes
1.2.2 NON-POINT SOURCE POLLUTION
Non-point source (NPS) pollution refers to diffuse contamination that does not originate
from a single discrete source. NPS pollution is often a cumulative effect of small amounts of
contaminants gathered from a large area. Nutrient runoff in stormwater from “sheet flow”
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over an agricultural field or a forest is sometimes cited as examples of NPS pollution.
Contaminated stormwater washed off of parking lots, roads and highways, called urban
runoff, is sometimes included under the category of NPS pollution. However, this runoff is
typically channeled into storm drain systems and discharged through pipes to local surface
waters, and is a point source. The CWA definition of point source was amended in 1987 to
include municipal storm sewer systems, as well as industrial stormwater, such as from
construction sites.
FIGURE 1.1
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1.3 PARAMETERS OF INTEREST
The parameters considered in determining the quality of water are many and varied. The
choice of parameters therefore rests on the researcher’s interest and objectives.
Possible choice of parameters may be centered on the following:
Geographical location
Economic activities
Source of pollution
Availability of appropriate instrument and reagent.
This project would focus on the conventional and nutrient parameters.
1.4 CONVENTIONAL/PHYSICAL PARAMETERS
pH
Temperature
TDS
Turbidity
Conductivity
Salinity
1.4.1 NUTRIENT PARAMETERS
These parameters are the result of life activities in the lagoon. They provide the nutrient
requirement of organisms and such explain why life may exist in water. They include:
Nitrate Phosphate Sulphate
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1.5 SPECTROPHOTOMETRY
In spectrophotometer analysis, a source of radiation is used that extends into the ultraviolet
region of the spectrum. The instrument employ is the spectrophotometer. It consists of two
components;
An optical spectrometer- it is an instrument possessing an optical system which can
produce dispersion of incident electromagnetic radiation, and with which
measurements can be made of the quantity of transmitted radiation at selected
wavelengths of the spectral range.
A photometer is a device for measuring the intensity of transmitted radiation or a
function of this quantity.
The variation of the colour of a system with change in concentration of some components
forms the basis of calorimetric analysis. The colour is usually due to the formation of a
coloured compound by the addition of an appropriate reagent.
Colorimetry is concerned with the determination of the concentration of a substance by
measurement of the relative absorption of light with respect to a known concentration of
the substance.
1.5.1 BEER-LAMBERT’S LAW
The law states that there is a logarithmic dependence between the transmission (or
transmissivity), T, of light through a substance and the product of the absorption coefficient
of the substance, α, and the distance the light travels through the material (i.e. the path
length), ℓ. The absorption coefficient can, in turn, be written as a product of either a molar
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absorptivity of the absorber, ε, and the concentration c of absorbing species in the material,
or an absorption cross section, σ, and the (number) density N of absorbers.
For liquids, these relations are usually written as
Whereas for gases, and in particular among physicists and for spectroscopy and
spectrophotometry, they are normally written
Where I0 and I are the intensity (or power) of the incident light and that after the material,
respectively
The transmission (or transmissivity) is expressed in terms of an absorbance which for liquids
is defined as
Whereas for gases, it is usually defined as
This implies that the absorbance becomes linear with the concentration (or number density
of absorbers) according to
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And
For the two cases, respectively
Thus, if the path length and the molar absorptivity (or the absorption cross section) is
known and the absorbance is measured, the concentration of the substance (or the number
density of absorbers) can be deduced.
Although several of the expressions above often are used as Beer–Lambert law, the name
should strictly speaking only be associated with the latter two. The reason is that
historically, the Lambert law states that absorption is proportional to the light path length,
whereas the Beer law states that absorption is proportional to the concentration of
absorbing species in the material.
If the concentration is expressed as a mole fraction i.e. a dimensionless fraction, the molar
absorptivity (ε) takes the same dimension as the absorption coefficient, i.e. reciprocal length
(e.g. cm−1). However, if the concentration is expressed in moles per unit volume, the molar
absorptivity (ε) is used in L·mol−1·cm−1, or sometimes in converted units of mol−1 cm2.
The absorption coefficient α' is one of many ways to describe the absorption of
electromagnetic waves. For the others, and their interrelationships, see the article:
Mathematical descriptions of opacity. For example, α' can be expressed in terms of the
imaginary part of the refractive index, κ, and the wavelength of the light (in free space), λ0,
according to
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In molecular absorption spectrometry, the absorption cross section σ is expressed in terms
of line strength, S, and an (area-normalized) line shape function, Φ. The frequency scale in
molecular spectroscopy is often in cm−1, wherefore the line shape function is expressed in
units of 1/cm−1, which can look funny but is strictly correct. Since N is given as a number
density in units of 1/cm3, the line strength is often given in units of cm2cm−1/molecule. A
typical line strength in one of the vibrational overtone bands of smaller molecules, e.g.
around 1.5 μm in CO or CO2, is around 10−23 cm2cm−1, although it can be larger for species
with strong transitions, e.g. C2H2. The line strengths of various transitions can be found in
large databases, e.g. HITRAN. The line shape function often takes a value around a few
1/cm−, up to around 10/cm−1 under low pressure conditions, when the transition is Doppler
broadened, and below this under atmospheric pressure conditions, when the transition is
collision broadened. It has also become commonplace to express the linestrength in units of
cm−2/atm since then the concentration is given in terms of a pressure in units of atm. A
typical linestrength is then often in the order of 10−3 cm−2/atm. Under these conditions, the
detectability of a given technique is often quoted in terms of ppm•m.
The fact that there are two commensurate definitions of absorbance (in base 10 or e)
implies that the absorbance and the absorption coefficient for the cases with gases, A' and
α', are ln 10 (approximately 2.3) times as large as the corresponding values for liquids, i.e. A
and α, respectively. Therefore, care must be taken when interpreting data that the correct
form of the law is used.
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The law tends to break down at very high concentrations, especially if the material is highly
scattering. If the light is especially intense, nonlinear optical processes can also cause
variances.
Figure 1.2
Diagram of Beer–Lambert absorption of
a beam of light as it travels through a
cuvette of width ℓ.
1.5.2 CALIBRATION OF THE SPECTROPHOTOMETER
The spectrophotometer is operated by first of all standardizing the instrument with the
respective chemical. A given number was entered on the instrument. After which it
displayed a wavelength with respect to the parameter of interest. The instrument was then
turned to the wavelength and the necessary parameter concentrations were then read after
treating the samples with the appropriate reagent.