ENVIRONMENTAL CHEMISTRYCHM 314

ENVIRONMENTALCHEMISTRY?

Environmental chemistry is the study of various chemical phenomenon taking place in the environment

It comprises of chemical spp existing in the various segment of the environment, their sources, pathways, reaction and their consequences

on the activities on human being and other living forms.

Is the study of the sources, transport, effects and fate of chemical spp in water, soil and air environment.

OBJECTIVES OF THE COURSE

• The course is about environmental issue and the chemistry behind them.,

• It aims to apply the knowledge of chemistry to understand environmental issues., and

• It provides the students the knowledge of how to do chemist share in improving environmental quality

ENVIRONMENT?• The totality of circumstances surrounding an organism or groups of

organism which may include external physical. biological and chemical conditions that affect and influence the growth, development and survival of organism.

• Simply means our surrounding including air, water, land, all plants, animals and human being living their in and inter-relationship which exist among them.

• Environment could be biophysical, natural, man made or global.

Biophysical Environment• Biotic & Abiotic factors

• Abiotic Factors: consist of the physical and chemical factors which include the soil, water, air, inorganic and organic compounds, temperature, moisture, wind, currents, tides, solar radiation.

• They are essentially non-living components that affect the living organisms of the ecosystem

• Biotic Factors: consists of all living organisms such as plants, animals, microbes including man.

• These two factors are interrelated.

• Biotic and abiotic factors combine to create an ecosystem.

• An ecosystem is a community of living and non-living things considered as a unit.

• If a single factor is changed, perhaps by pollution or natural phenomenon, the whole system could be altered e.g irrigation or farming activities may lead to erosion or flooding.

Natural and Man-made Environment

• Biophysical environment may be viewed as natural environment and man-made or built environment.

• The natural environment, commonly referred to as the environment, encompasses all living and non-living things occurring naturally on Earth.

• Global environment consists of four segments viz, the atmosphere, the hydrosphere, the lithosphere and biosphere

• The atmosphere is a mixture of gases, extending outward from the surface of the earth, which evolved from elements of the earth. The atmosphere is the region of air which covers the earth to a height of about 500 km from earth surface.

• It is the protective thick gaseous mantle, surrounding the earth, which sustains life on earth and saves from unfriendly environment of outer surface

• The hydrosphere is the region of the environment related to water and consists of the seas, rivers, oceans, the lakes, ponds, streams, glaciers, polar ice caps, and the shallow groundwater.

• 80% of the earth is covered with water: 97% is from oceans, 2% from glaciers and polar ice carps and remaining 1% water is the only useful part to living organisms toward drinking and agricultural activities.

• The lithosphere is the soil mantle that wraps the core of the earth. It is the mantle of rocks constituting the earth’s crust.

• Lithosphere covers the entire solid component of the earth containing minerals, rocks, soil organic compounds air and water.

• It contains three layers: crust, mantle and core.

• The biosphere is a thin shell that encapsulates the earth. A zone of living organisms which denotes mutual interaction of organisms related to lithosphere, hydrosphere and atmosphere with the environment.

Pollution of the Environment.

• Contamination: Is the presence of a minor constituent in another chemical or mixture often at trace level.

• A contaminant is a substance present in nature due to human activity that would not otherwise be there.

• It can also be defined as a substance present in the environment as a result of human activity, but without harmful effects.

• Pollution: Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem.

• The Organization of Economic Cooperation and Development (OECD) defined pollution as the introduction by man, directly or indirectly, of substances or energy into the environment resulting in deleterious effects of such a nature as to endanger human health, harm living resources or interfere with amenities or other legitimate use of the environment.

• Pollution can also be defined as undesirable changes in physical, chemical or biological characteristics of air, water or land that will be or may be harmful to man and other life, industrial processes, living conditions and cultural assets.

• It can further be described as alterations that bring about an unfavorable development in the surrounding arising from human activities.

• Environmental pollution in its broadest sense is the unfavourablealteration of our surroundings, wholly or largely as a by-product of man’s actions, through direct or indirect effects of changes in energy patterns, radiation levels, chemical and physical constitution and abundance of organisms.

• Sources of Pollution

• Point sources: pollution originating from a single, identifiable source e.g. Discharge pipe from factory; animal feeding operations, animal waste treatment plant, storage, handling, mixing and cleaning area for pesticides, fertilizers and petroleum.

• Non-point sources occurs as water moves across the land or through the ground and picks up natural and man-made pollutants

.

Pollutants

• Pollutants may be defined as unwanted substances causing damages to things in the environment.

• It may be natural or anthropogenic

Types of Pollution

• Air Pollution

• Air pollution is the presence in the atmosphere of one or more air contaminants in sufficient quantities, of such characteristics, and such duration as to be or to threaten to be injurious to human, plant, or animal life or property.

• Air pollution could be indoor or outdoor.

• Indoor Air Pollution: is pollution inside homes, offices, class room and other buildings e.g

• Radon- a colourless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium

• Molds and other allergens: These biological chemicals can arise from different means but there are two common classes: (a) moisture induced growth of mold colonies and (b) natural substances released into the air such as plant pollen. Some mold contain toxic compounds (mycotoxins).

• Indoor combustion Products: e.g tobacco smoke, woodstoves, kerosene and gas heaters, gas stoves etc.

• Major pollutants released are carbon dioxide, carbon monoxide. Volatile organic compounds(VOCs) nitrogen dioxide etc.

• Outdoor Air Pollution: Sometimes called ambient air pollution is air pollution outside the home, office or enclosed places.

Sources of Air Pollutants

• (i) Natural

Dust from natural sources usually large areas of land with little or no vegetation.

Methane, emitted by digestion of foods by animals

Radon gas from radioactive decay with the earth’s crust

Volcanic activity, which produce sulphur, chlorine, and ash particulates

• (ii) Anthropogenic (human activity)

Stationary sources include smoke stacks of power plants, factories and waste incinerators

Mobile sources include motor vehicles, marine vessels, air craft and the effect of sound etc.

Controlled or prescribed burning in forest management, farming, green house abatement.

Fumes from paint, hair spray, varnish, aerosol sprays and other solvents.

Waste deposition in landfills, which generate methane. Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air.

Military, such as nuclear weapons, toxic gases, germ warfare and rocketry.

• The chief anthropogenic causes of air pollution are:

• Combustion: The sources of energy in many factories and power stations are the combustion of fossil oil; this has replaced the combustion of coal to a large extent. Coal contains sulphur and compounds of sulphur as impurities.

• Vehicular emission: A motor vehicle use petrol, a hydrocarbon fuel, and the combustion of this fuel, at high temp in the car engine, produces a wide range of pollutants.

• Aircraft emission: Emissions from aircrafts are a small part of total emissions from all sources on a national scale. Aircraft emissions account for 10% of hydrocarbons(HC), oxides of nitrogen (NOx), and carbon monoxide (CO), and even a smaller fraction of particulate matter (PM) and oxides of sulphur (SOx).

Effects of Air Pollutant• Effects on Human Health: An average man breathes 22,000 times a

day and takes in 16 kg of air each day. The impurities in the inhaled air can affect human health in a number of ways, depending upon the nature and concentration of the pollutants, duration of exposure and age group of the receptor.

• Specific health effect of air pollutants are as follows:

(i). Eye irritation can be caused by many air pollutants such as NOx, O3, PAN, smog particulate etc

(ii) Nose and throat irritant can be caused by SO2, Nox, insecticides, pesticides etc.

(iii) Gaseous pollutants like H2S, SO2, NO2 and hydrocarbon can cause odor, nuisance even at low concentration

• (iv) Irritation of respiratory tract can be caused by SOx, NOx, O3, CO etc

• (v) Increase in mortality and morbidity rate.

• (vi) A variety of particulates, particularly pollen can initiate asthmatic attacks.

• (vii) High concentrations of SO2, NO2, SPM (suspended particulate matter), photochemical smog can aggravate chronic pulmonary disease like bronchitis and asthma.

• (viii) careless use of body sprays, especially fake or adulterated ones can initiate asthmatic attack

• (ix) Carbon dioxide, which is 200 times more reactive than oxygen combines with hemoglobin in the blood and consequently increases stress on those suffering from cardiovascular and pulmonary disease.

• (x) Hydrogen fluoride can cause fluorosis and mottling of teeth.

• (xi) Air pollutants such POPs, aliphatic hydrocarbons are carcinogenic.

• (xii) Dust can cause specific respiratory diseases

• (xiii) etc

Global Consequences of Air Pollution• Depletion of the Ozone Layer

• Green House Effects

• Global warming

• Acid Rain and Acidification

Major Air Pollutants• Odour

• Carbon monoxide

• Carbon dioxide

• Nitrogen oxides

• Nitrogen dioxide

• Effects of Particulate Matter

Volatile Organic Compounds etc

Water Pollution & Chemistry• Water pollution can be defined as the presence of foreign substances or

impurities in water in such quantity as to constitute health hazard by lowering the water quality and making it unfit for use.

• Sources: Point & Diffused sources

• Point sources: Sources that can be identified e.g waste generated by human settlements, domestic, commercial and industrial activities, petroleum related industry, energy utilization activities and precipitation of atmospheric pollutants, municipal sewage, treatment plants etc.

• Diffused sources: Otherwise known as non-point source are sources of generalized discharge of waste water whose location cannot be easily identified. e.g run-off from agricultural land treated with fertilizer

Types of Water Pollution• Precipitation pollution

• Surface water pollution

• Agricultural water pollution

• Ground water pollution

• Domestic water pollution

• Industrial water pollution

• Marine water pollution

• Mining water pollution

Classification of Water Pollution• Physical pollutants: include silt, clay discarded objects, weeds,

decaying organic matter, which generally affect the aesthetic quality of surface water.

• Chemical Pollutants- include non-biodegradable, toxic heavy metals; persistent and hazardous pollutants.

• Microbial pollutants- arising from discharge of effluents from domestic sources and manufacturing industries into surface waters. Faecal contamination also lead to microbial pollutants.

Water Quality Monitoring ParametersPhysical characteristics

• Colour in water may be due to inorganic ions, such as Fe & Mn, humus and peat materials, plankton, weeds and industrial wastes.. It means the colour of water from which turbidity has been removed.

• Apparent colour includes not only the colour due to substances in solution, but, also that due to suspended matter.

• Apparent colour is determined on the original sample without filtration or centrifugation.

Platinum cobalt (visual comparison) method

• Principle: Colour is measured by visual comparison of the sample with platinum-cobalt standards. One unit of colour is, that produced by 1mg Pt/litre in the form of chloroplatinate.

Sample Handling & Preservation• Representative samples shall betaken in clean glassware. Colour

should be determined as early as possible after the collection of samples as biological activity or physical changes occurring during storage may affect the colour. Refrigeration of water sample at 4ᵒC is recommended.

• Apparatus: Nessler cylinder 50 mL capacity; centrifuge or membrane filter 0.45 µm.

• Standard chlorolatinate solution: Dissolved 1.246 g potassium chloroplatinate (K2PtCl6) (equivalent to 500 mg metallic Pt) and 1.0 g crystalline cobaltous chloride (CoCl36H2O) equivalent to 250 mg metallic cobalt) in distill water containing 100 mL conc HCl.

• Dilute to 1000 mL with distrill water. This standard solution is equivalent to 500 colour units.

• Preparation of standards : prepare standards having colour units of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60 and 70 by diluting 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, and 7.0 mL standard chloroplatinate solution with distilled water to 50 ml .

• Protect the standards against evaporation and contamination by the use of clean inert stoppers. The standard should be protected against absorption of ammonia which causes increase in colour.

• Procedure

• Apparent colour: observe the color of the sample by filling a matched Nesslercylinder to the 50 mL mark with water and compare with standards. Compare by looking vertically downward through the cylinder towards a white surface placed at such an angle that light is reflected upwards through the column of liquid. If turbidity has not been removed, report the color as “apparent color”. If the colour exceeds 70 units, dilute the sample with distilled water until the color is in the range of the standards..

• Calculation: calculate the color units as follows:

• Color units=50𝐴

𝑉

• Where : A = Estimated color of diluted sample• V= Volume in mL of sample taken for dilution

pH: see your note

Turbidity: The turbidity is the reduction of transparency due to the presence of particulate matter such as clay or slit, finely divided organic matter, plankton or other microscopic organisms.

These cause the light to be scattered and absorbed rather than transmitted in straight lines through the sample. The values are expressed in nephelometric turbidity units (NTU). The method is applicable to drinking, surface and saline water in the range of turbidity 0-40 NTU. Higher values may be obtained by dilution of the sample.

• pH: This is the logarithm of reciprocal of hydrogen ion activity in moles per litre.

• In natural water, the pH is governed by the exchange of carbon dioxide with the atmosphere Carbon dioxide is soluble in water and the amount of CO2 that will dissolve in water will be a function of temperature and the concentration of CO2 in the air.

• Lower values in pH are indicative of high acidity, which can be caused by the deposition of acid forming substances in precipitation. A high organic content will tend to decrease the pH because of the carbonate chemistry.

• Methods for determination of pH in water are: Electrometric method; colorimetric method.

• Principle of Electrometric method: The pH value is determined by measurement of the electromotive force of a cell consisting of an indicator electrode immersed into the test solution and a reference electrode. Contact between the test solution and the reference electrode is usually achieved by means of a liquid junction which forms part of the reference electrode. The electromotive force is measured with a pH meter.

• Electrical Conductivity (EC): EC in natural waters is the normalized measure of the water’s ability to conduct electric current. This is mostly influenced by dissolved salts. The common units for EC is µS/cm.

• EC reflect the amount of total dissolved solid (TDS) in natural waters.

• Temperature: many aquatic organisms are sensitive to changes in water temperature. Temperature is an important water quality parameter and is relatively easy to measure. Water bodies will naturally show changes in temperature seasonally and daily.

• Hardness: Hardness may be defined as the concentration of all multivalent metallic cations in solution. The principal ions causing hardness in natural water are calcium and magnesium. Others which may be present though in much smaller quantities are iron(II), manganese(II), strontium and aluminium.

• By convention, water hardness is obtained by measuring the concentrations of the individual cations, principally Ca and Mg, and report them in terms of equivalent mass rather than in terms of mg/L. The equivalent mas of substance is its atomic or molecular mass divided by the valency or ionic charge or ionic charge of the cation of interest.

• 𝐸𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡 𝑚𝑎𝑠𝑠 =𝑎𝑡𝑜𝑚𝑖𝑐 𝑜𝑟 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑚𝑎𝑠𝑠

𝑣𝑎𝑙𝑒𝑛𝑐𝑦 (𝑜𝑟 𝑖𝑜𝑛𝑖𝑐 𝑐ℎ𝑎𝑟𝑔𝑒)

• e.g. in CaCO3, the valency or ionic charge of Ca (the cation of interest) is 2

• therefore, 𝑒𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡 𝑚𝑎𝑠𝑠 𝐶𝑎𝐶𝑂3 =40𝑔+12𝑔+3×16𝑔

2𝑝𝑒𝑟 𝑒𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡

• = 50𝑚𝑔/𝑚𝑒𝑞

Alkalinity

• This is a measure of the capacity of natural water to neutralize acid. The main contributors to alkalinity in natural waters are HCO3

-, CO32- and OH-;

phosphate, silicate, NH3 and other bases must also be considered. Thus, alkalinity may be expressed as:

• Alkalinity (meq/L) – [HCO3-] + 2[CO3

3-] – [H+]

Chloride Determination

• Argentometric method was used for chloride determination. Ten milliliter of the sample was titrated against 0.014 M silver nitrate (AgNO3) using 2 drops of potassium chromate (K2CrO4) indicator solution to a pinkish yellow end point (APHA, 1995).

• Calculation was done according to the following relationship:

• mg Cl/L = A-B × 35450

• V

• where A = volume of titrant used for sample;

• B = volume of titrant used for blank;

• M = Molarity of AgNO3; and

• V = volume of sample taken.

Sulphate (SO42-) Determination

• For the sulphate determination, turbidimetric method (Ademoroti, 1996) can be used. 20 mL of the water sample is treated with 0.3301 g of Barium chloride and 1 mL of conditioning reagent (mixture of 50 mL glycerol, 30 mL conc. HCl, 300 mL distilled water, 100 mL 95% ethanol and 75 g NaCl). The colloidal solution formed is measured using UV/ visible spectrophotometer. The sulphate stock standard is prepared by dissolving 0.0148 g anhydrous sodium sulphate, (Na2SO4) in distilled water and diluted to give 100 mg/L solution using 100 mL standard flask. 5 mg/L, 10 mg/L, 15 mg/L, 20 mg/L, 25 mg/L, 30 mg/L and 40 mg/L series of standards is prepared from the stock standard solution. These are then treated with 1 mL of conditioning reagent and 0.3301 g of BaCl2. A standard calibration curve is constructed using J UV/visible spectrophotometer. The absorbance of the standard solutions and worked-up samples are measured at 425 nm.

Phosphate (PO43-) Determination

• Vanadomolybdophosphoric acid colorimetric technique (APHA, 1995) can be used to determine the levels of phosphate in the samples. 5 mL vanadate-molybdate reagent is used to develop yellow colour in the standards and samples, ten minutes after addition of this reagent to 17.5 mL of sample or standard solutions, which is then made up to 25 mL mark with distilled water in a stadard volumetric flask. The intensity of this yellow colour is proportional to the phosphate concentration after measuring the absorbance at 470 nm.

• Vanadatemolybdate reagent is prepared by dissolving 6.25 g ammonium molybdate, (NH4)6Mo7O24.4H2O in 75 mL distilled water and labelled solution A. Solution B is prepared by dissolving 0.3125 g ammonium metavanadate, NH4VO3 via heating to boiling in 75 mL distilled water, cooled and added 82.5 mL conc HCl. Solution B is then cooled to room temperature after which solution A is poured into it, mixed and diluted to mark in a 250 mL standard flask.

• Phosphate stock standard is prepared by dissolving in distilled water 0.0220 g anhydrous KH2PO4 and diluted to 100 mL to give 50 mg/L standard solution. 5 mg/L, 10 mg/L, 15 mg/L, 20 mg/L, and 25 mg/L concentrations were used to plot a calibration curve the readings are taken at 470 nm.

Nitrate (NO3-) Determination

• Ultra-violet spectrophotometric screening method (APHA, 1995) can be used in which measurement of ultra violet absorption at 220 nm enabled a rapid determination of NO3

-. Since dissolved organic matter also may absorbed at 220 nm and NO3

- does not absorb at 275 nm, a second measurement of the sample made at 275 nm was used to correct the NO3

-

values.

• For the nitrate concentrations, potassium nitrate (KNO3) is dried at 105 oC for 24 hours in an oven and 0.0722 g of it is dissolved and diluted to mark in a 100 mL volumetric flask to give 100 mg/L standard solution. From the stock solutions, 2 mg/L, 4 mg/L, 6 mg/L, 8 mg/L, and 12 mg/L concentrations are prepared and used to plot the calibration curve at 220 nm by treating 25 mL each of the series of standards with 0.5 mL of 1.0 M HCl.

• During the nitrate concentration determination in the samples 0.5 mL of 1.0 M HCl is added to 25 mL clear sample and mixed thoroughly. The absorbance is then determined at 220 nm and 275 nm, respectively.

Total Alkalinity Determination• Total alkalinity comprises of hydroxide (OH-), carbonate (CO3

-), and bicarbonate (HCO3

-). It can be determined in the water samples by titration (Ademoroti, 1996). Carbon (IV) oxide (CO2) free distilled water which is prepared by boiling distilled water for 15 minutes in order to expel CO2 and later cooled to room temperature is used to prepare stock and standard solutions, as well as dilution water for standardization.

• To 10 mL of the water sample, 1 mL of 0.05 M Na2S2O3.5H2O is added to remove free residual chlorine if present. This is followed by the addition of methyl orange indicator and then titrated with 0.01M H2SO4 to faint pink end point. The total conversion for this corresponds to the equation:

• OH- + CO32- +4H+→ 3H2O + CO2,

• and the calculation was based on the relationship:• Vt × M × 100,000• Total Alkalinity (as mg/L CaCO3) = -------------------------• mL sample• where Vt = total volume (mL) of acid used for the titration; and• M = Molarity of acid used.

Bicarbonate (HCO3-) Determination

• Alkalinity due to bicarbonate, according to Ademoroti (1996), is the difference between total alkalinity (OH-, CO3

2- and HCO3-) and phenolphthalein alkalinity (OH-

and CO32-). That is,

Bicarbonate alkalinity = total alkalinity – phenolphthalein alkalinity. • Phenolphthalein alkalinity is determined thus; 10 mL of water sample is taken into a

clean conical flask and 1 mL of 0.05 M Na2S2O3.5H2O is added to remove residual chlorine. If solution remains colourless then phenolphthalein alkalinity (PA) is equal to zero, but if the solution turns pink, PA is present and such solution is then titrated against 0.01 M H2SO4 to colourless end point.

• Calculation can be done using the relationship:Vp × M × 100,000

Phenolphthalein alkalinity (as mg/L CaCO3) = --------------------------mL sample

• where Vp = volume of the acid used; andM = Molarity of acid.

In situations whereby there is no phenolphthalein alkalinity, bicarbonate alkalinity is reported as total alkalinity in line with the relationship between total alkalinity and phenolphthalein alkalinity (Ademoroti, 1996).

Total Solid (TS) Determination

• The principle involves evaporating 50 mL of each well mixed water samples to dryness in a weighed dish at about 105oC. The increased weight over the empty dish represents the total solid.

• The weight of the empty beaker was taken and recorded as W1 after it was allowed to dry in an oven to a constant weight. After drying, 50 mL of well mixed water samples were measured into the evaporating dishes and placed inside the oven to evaporate. After the evaporation, the dishes were brought out of the oven and allowed to cool by placing them inside the desiccators. The weight of the cooled evaporating dishes after evaporation was then taken and recorded as W2.

• W2 - W1 ×103

• Total solid (mg/L) = ----------------------

Volume of sample

where W1 = weight of empty dishes without the sample (g); and

• W2 = weight of dishes after evaporation of water sample (g)

Suspended Solid (SS) Determination

• Whatman No.1 filter papers are placed in an oven set at 105oC and dried to constant weights. The filter papers are removed from the oven and placed in a desiccator to cool down. The weight is then taken and recorded as W1. An accurately measured 50 mL of each, well mixed water sample is filtered through a weighed dry filter paper. The residue on the filter paper is dried to constant weight in an oven set at 105oC. The dried filter paper containing the residue is then weighed as W2. The increase in weight of the filter paper represents the suspended solids.

• W2 – W1 × 103

• Suspended solid (mg/L) = ----------------------------

• Volume of sample (mL)

• where W2 = weight of dried filter paper after filtration (g); and

• W1 = weight of dried filter paper before filtration (g).

Oxygen Demand Test

• Oxygen demand by a sample may be defined as the amount of oxygen required to oxidize the organic content in the sample to carbon(iv)oxide and water. There are two types of oxygen demand tests; COD and BOD

Chemical Oxygen Demand (COD)

• This is the amount of oxygen required to oxidize the organic fraction of a sample which is susceptible to tetraoxomanganate(vii)permanganate or heptaoxochromate(vi) (dichromate) oxidation in acid i.e solution.

Tetraoxomanganate VI test

• The test utilizes KMnO4 as the oxidizing agent. The water/waste water sample is borted with a measured excess of the manganite(VII) in acid i.esolution H2SO4 for 90 mins. The pink solution is cooled and a known amount of ammonium oxalate NH4C2O4 is added, the solution becoming colorless. Excess oxalate is the titrated against KMnO4 solution until the pink color returns. The oxalate used is calculated by difference and the KMnO4 used is calculated from simple stoichiometry. The equation below corresponds to oxidation of the oxalate.

• Heptaoxochromate(VI) Test

• This test utilizes potassium hepaoxoxhromate(VI) K2Cr2O7 as the oxidizing agent. The test is widely used for COD measurement in preference to the use of KMnO4. COD test is used for estimating the concentration of organic matter in waste water.

• This test is preferred by heating under total reflux condition a measured sample with a known excess of K2Cr2O7 in the presence of H2SO4 for a period of 2 hrs. Organic matter in the sample is oxidized and as a result, yellow or red colored K2Cr2O7 is consumed and replaced by green chromic

• Silver tetraoxosulpahte(VI) is added as a catalyst and for the oxidation of straight chain alcohol and acids.

Chemical Oxygen Demand (COD) Determination• COD is a measure of the amount of oxygen required for complete oxidation

of carbon content of organic matter present in a sample of water, waste water or effluent. 100 mL of distilled water was pipette into a 250 mL conical flask. 10 mL of 25% H2SO4 and 20 mL of 0.01 M KMnO4 were added to the mixture. The flask was placed on boiling water basin for 30 mins. The flask was cooled down to room temperature before 10% KI solution was added. The liberated iodine was titrated with 0.05 M Na2S2O3 solution using 2 drops of starch indicator. The titre value obtained served as titre value, A.

• To obtain titre value, B, 100 mL of each water sample (constituted by adding 10 mL of sample to 90 mL of deionized water) was placed into a separate 250 mL flask and titrated as stated in the above procedure. The calculations were done using the relationship:

• (A- B) ×M × 40,000• COD (mg/L) = ------------------------------• Volume of sample taken• where A = distilled water titre value;• B = sample water titre value; and• M = Molarity of KMnO4

• Biochemical Oxygen Demand (BOD)

• BOD is used as a measure of the quality of O2 required for oxidation of biodegradable organic matter present in a water sample by aerobic biochemical action.

• BOD is performed by incubation of a sample in the dark for 5 days at 20 0C. This means O2 consumed by bacteria during oxidation of organic matter (biodegradation) in 5 days at 20 0C. The period of incubation has been considered suitable for biodegradation of considerable amount of organic matter. The standard BOD test specifies pH of 7.2. In case where the sample pH is more or less than 7.2 it is corrected to 7.2 by adding dilute solution of acid or alkali as required.

• Determination of DO

• This is preferred to the titrimetric method due to Winkler. The sodium azide modification of Winker method is popularly adopted. The modification effectively removes interference caused by nitrate. Winkler method is based on the oxidation of iodide ion (I-), which is contained in the alkaline iodide azide reagent to iodine I2 by the DO of the sample and titration of the iodine by sodium thiosulphate Na2S2O3 using starch indicator. The oxidation is performed in acid medium (H2SO4 and in the presence of MnSO4. The alkali iodide reagent is a solution of NaOH , NaIand NaN3 sodium azide).

Soil Chemistry• Soil is formed not just by the weathering of minerals derived from rocks but

also by the input of organic matter from the decomposition of plants and to a lesser extent the decomposition and waste products of animals and micro-organisms.

• The soil science society of America (http://www.soils.org/ssaglass/): defined soil as the unconsolidated minerals or organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants.

• Further, they defined soil as the unconsolidated mineral or organic material on the surface of the earth that has been subjected to and shows the effects of genetic and environmental factors of climate (including water and temperature effects), micro and macro-organisms, conditioned by relief, acting on parent material over a period of time.

• The five points underlined in the second definition are known as the soil formation factors, which interact to produce a soil of particular characteristics in any given place.

• Soil is a combination of all the major components of the surface environment: the atmosphere, hydrosphere, lithosphere and biosphere.

• Determination of soil water and air content and bulk density

• 𝐺𝑟𝑎𝑣𝑖𝑚𝑒𝑡𝑟𝑖𝑐 𝑠𝑜𝑖𝑙 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 % = (𝑚𝑎𝑠𝑠 𝑜𝑓 𝐻2𝑂

𝑚𝑎𝑠 𝑜𝑓 𝑜𝑣𝑒𝑛 𝑑𝑟𝑖𝑒𝑑 𝑠𝑜𝑖𝑙) ×

100

• 𝑉𝑜𝑙𝑢𝑚𝑒𝑡𝑟𝑖𝑐 𝑠𝑜𝑖𝑙 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 % = (𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝐻2𝑂

𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑜𝑖𝑙 𝑐𝑜𝑟𝑒) × 100

• 𝑆𝑜𝑖𝑙 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑔𝑟𝑎𝑣𝑖𝑡𝑦 𝑔𝑐𝑚−3 =𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑣𝑒𝑛 𝑑𝑟𝑦 𝑠𝑜𝑖𝑙

𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑜𝑖𝑙 𝑠𝑜𝑙𝑖𝑑𝑠

• 𝑃𝑜𝑟𝑒 𝑠𝑝𝑎𝑐𝑒 % =𝑠𝑜𝑖𝑙 𝑐𝑜𝑟𝑒 𝑣𝑜𝑙 𝑜𝑓 𝑠𝑜𝑖𝑙 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑖𝑛 𝑐𝑜𝑟𝑒

𝑠𝑜𝑖𝑙 𝑐𝑜𝑟𝑒 𝑣𝑜𝑙𝑢𝑚𝑒× 100

• 𝑆𝑜𝑙𝑖𝑑 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 100% =𝑣𝑜𝑙 𝑜𝑓 𝑠𝑜𝑖𝑙 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒𝑠 𝑖𝑛 𝑐𝑜𝑟𝑒

𝑡𝑜𝑡𝑎𝑙 𝑐𝑜𝑟𝑒 𝑣𝑜𝑙× 100

• 𝑊𝑎𝑡𝑒𝑟 𝑓𝑖𝑙𝑙𝑒𝑑 𝑝𝑜𝑟𝑒 𝑠𝑝𝑎𝑐𝑒 % = 𝑣𝑜𝑙𝑢𝑚𝑒𝑡𝑟𝑖𝑐 𝑠𝑜𝑖𝑙 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑡𝑒𝑛𝑡

• 𝐴𝑖𝑟 𝑓𝑖𝑙𝑙𝑒𝑑 𝑝𝑜𝑟𝑒 𝑠𝑝𝑎𝑐𝑒 % = %𝑝𝑜𝑟𝑒 𝑠𝑝𝑎𝑐𝑒 −%𝑤𝑎𝑡𝑒𝑟 𝑓𝑖𝑙𝑙𝑒𝑑 𝑝𝑜𝑟𝑒 𝑠𝑝𝑎𝑐𝑒

• Mineral Components of Soil

• The nature of the parent material is the most important factor influencing the mineral components of soil of a soil. The textural properties and inherent fertility are directly affected by the types of rocks and minerals found in the parent material. Parent material can be consolidated rocks (igneous, metamorphic, sedimentary rocks) or unconsolidated superficial deposits that have been transported by some agencies such as wind, ice or water.

• The primary soil minerals sometimes called inherited minerals are those that are derived from rocks of the parent material . These are silicates.

• Secondary minerals (which dominate the clay size fraction of soil < 0.002 mm) are formed in soil by the action of various weathering processes on the primary minerals derived from the parent material.

• The process that causes changes to the rocks and minerals of the soil parent material are collectively known as weathering.

• Weathering is a geochemical phenomenon (physical, mechanical and chemical). The processes involved in chemical weathering may be divided into the following categories:

1. Hydration/Dehydration

2. Dissolution

3. Acid Hydrolysis

4. Oxidation

5. Chelation

• ORGANIC COMPONENETS OF SOIL

• Soil is formed by the interaction of the mineral weathering product of rocks and the organic material introduced as a result of biological activity. Much of this organic materials plant is derived. In addition, animal and microbial excretion and decomposition must be taken into account.

Soil pH and Redox Potential

• Soil pH, which is a measure of the acidity or alkalinity and redox potential, a measure of the aeration status, are the two crucial factors that controls many of the chemical and biological processes in the soil.

• pH is defined as –log [H+] in solution is based on the concept of the partial ionization of water. Measure of pH in soil is usually done using a glass of pH electrode in a soil suspension.

Soil Acidity

• The atmosphere is a major source of soil acidity. In areas affected by industrial pollution, SO2 and NO2 dissolve in rain water to produce H2SO4 and HNO3 which are both strong acid cause even more acidity.

• Various soil processes also contribute to soil acidity. Decaying organic matter releases a number of organic acids. Nitrification, the microbial oxidation of NH4+ to NO3 by Nitrosomonas and nitrobacteria occur in slightly acidic to neutral soil and releases H+ ions.

Adjustment of Soil Acidity

• Most common plants grow best in soil with pH near neutrality. If the soil becomes too acidic for optimum plant growth, it may be restored to productivity by liming e.g addition of CaCO3.

• If the soil is too basic due to the presence of basic salts such as Na2CO3. Alkaline salt may be treated with aluminium or iron sulphate, which release acid on hydrolysis.

Soil Alkalinity

• Alkaline soil (pH > 7) contains solid phase carbonate and bicarbonate is the dominant anion in solution. Ca and Mg carbonates produces a soil of pH between 7 and 8.5, depending upon the concentrations of CO2 and Ca2+ or Mg2+ ions.

Redox Potential

• Redox potential is the measure of the oxidation-reduction state of a soil and is determined by redox reactions involving the transfer of electrons from one chemical specie to another.

Soil Composition

• Soil may be defined as material of variable depth with a substantial solid content at the earth’s surface which is undergoing changes as a consequence of chemistry, physics and biology process:

• Soil essentially consists of phases: a solid phase, a solution and gas phase.

• The solid phase usually includes an intimate mixture of mineral material, originating from rock, sediment or silt and organic material arising as a consequence of biological activity.

• The solution phase, this interact continuously with a solid phase. It originates infiltrating the soil or from rising water or water moving laterally.

• The gas phase or soil atmosphere composition depends upon biological activity

• The solid fraction of typical productive soil is approximately 5% organic matter and also 95% inorganic matter.

Water and Air in Soil

• Water is part of the three phases, solid-liquid-gas system that makes up the soil. It is the basic transport medium of carrying essential plant nutrients from solid soil particles into plant roots and plant leaf structure. The water enters the atmosphere from the plant leaves a process called transpiration.

• The availability of water to plants is governed by gradients arising from capillary and gravitational forces. The availability of nutrient solutes in water depends upon concentration gradients and electrical potential gradients.

Inorganic Component of Soil

• The weathering of parent rock and minerals to form the inorganic soil components results ultimately in the formation of inorganic colloids. These colloids are repositories of water and plant nutrients, which may be made available to plants as needed. Inorganic soil colloids often absorb toxic substances in soil, thus playing a role in detoxification of substances that otherwise would harm plants.

Organic Matter in Soil

• Though typically comprising less than 5% of a productive soil organic matter largely determines soil productivity. It serves as a source of food for microorganism, undergoes chemical reactions such as ion exchange and inferences the physical properties of soil. Some organic compounds contribute to weathering of mineral matter e.g Cr2O4

2-, oxalate in soil water dissolves minerals, thus speeding the weathering process and increasing the availability of nutrient ion specie which involves oxalate complexation of iron or aluminium.

OIL SPILL

• This is referred to an accidental dumping of oil or other petroleum products into ocean and its coastal water bays and habours. A wide spectrum of biotic community suffers the harmful impacts of oil spills.

CAUSES OF OIL SPILLS

• Two sources- exploration of offshore fields and transportation of crude oil by sea- have led to a multiplicity of massive accidental spills over the past few decades. Drilling waters discharged from sea rigs contaminate the surrounding waters. Sometimes, blowouts occur on offshore drilling platforms, in which case the oil spillage is much more spread out.

FATE OF THE SPILLED OIL

• Crude oil has a lower density than water. Hence on spillage, the oil floats on the sea surface, impairing it a dark colour. For this reason, oil spills are also referred to as black tides. The black tides spread away from the original source, generally at a speed of 1-4 km/h.

• During this duration, the oil undergoes one or more of the following transformations:

i) It may disperse and dissolve into the water column. So long the oil remains afloat, only the biotic community prevailing on the sea surface is affected. In a situation when the oil goes deep into the water column, a far greater quantum of marine life is likely to be affected.

ii)It may be oxidized by chemical and biotic pathways. Complete oxidation of oil into carbon dioxide and water totally wipes out the black tides. Over a short time, the hydrocarbons are partially oxidized to peroxides or phenols, with ultra violet component of natural light acting as catalyst.

Peroxides and phenols are more toxic than the original hydrocarbons comprising the crude oil but are soluble in water and thus, easily enter the food chain, causing harmful consequences.

iii) It may be incorporated into the bottom sediments. Some oil droplets are rapidly adsorbed by suspended clay particles which carry then to the bottom sediments. Oil in the sediments is very persistent and degrades extremely slowly over years or even decades.

CONSEQUENCES OF OIL SPILL

i) Reduced photosynthesis: Black tides reduce the transmission of sunlight across the water surface. Thus, the photosynthesis by aquatic algae slows down and the oxygen level of water drops, thereby all forms of marine life are affected.

ii) Sea birds: marine and coastal sea birds are vulnerable to oil spills. It has been observed that the population of auks, puffins and razorbills drops after every oil spill incident.

• Sea birds may directly ingest the oily material from the sea water. They also induce behavioural changes, so that nesting, mating and migratory activities are seriously disrupted.

• Hydrocarbons present in the oil are fat-soluble, and thus, become concentrated in the tissue of the birds. The toxic compounds then bioaccumulate in the food chain. Oil also damages the feathers.

iii) Fish: the larval and egg stages of fish are sensitive to the toxic effects of oil. An oil spill occurring in this period, thus, causes the fish population to decline. The migratory behaviour of fish is impaired in the event of an oil spill.

iv) Benthic community: The benthic community refers to those marine animals that reside on the sea floor. These are affected by the oil residues which become a part of the sediments. Mortality rates of crabs, zoanthids, hydrocorals and snails increase after an oil spill. Behavioural disorders, such as locometer impairment and abnormal burrows construction, have also been observed among these species

v) Marine vegetation: Seagrass meadows, which are found in the shallow coastal regions, are instantly killed after an oil spill. Seagrass provides food, habitat and refuge for diverse population of invertebrates and fish. Mangrove trees, which line up along the sea shore, are also killed when the black tide washed ashore.

MITIGATION OF OIL SPILL IN NIGERIA

• Several laws and policies have been taken in managing oil spill incidents at the international and national levels. These laws and policies are given in the following sections:

i) Oil Pollution Act (OPA) of 1990: This is responsible for many of the nation’s improvements in oil spill prevention and response. OPA 1990 provides guidance for government and industry on oil spill prevention, mitigation, clean-up and liability. The majority of OPA 1990 provisions were targeted at reducing the number of spills followed by reducing the quantity of oil spilled.

ii) National Oil Spill Detection and Response Agency (NOSDRA): NOSDRA was initiated by the ministry of Environment and approved by the federal government. The establishment of contingency plan and the agency was in compliance with the International Convention of Oil Pollution Preparedness, Response and Cooperation (OPRC90)to which Nigeria was signatory.

iii) The Niger Delta Development Commission (NDDC): To reduce the rate of oil incidents along the Nigerian coast particularly as a result of vandalisation.. The NDDC Act (2000) are expected to carry out among other things the following tasks:

a) Cause the Niger Delta area to be surveyed in order to ascertain measures, which are necessary to promote its physical and socio-economic development.

b)Prepare plans and schemes designed to promote the physical development of the Niger Delta area.

c) Identify factors inhibiting the development of the Niger Delta and assist the member states in the formation and implementation of policies to ensure sound and efficient management of the resources of the Niger Delta.

d) Assess and report on any project funded or carried out in the Niger-Delta area by oil and gas producing companies and any other company including NGO and ensure that funds released for such projects are properly utilised;

e)Tackle ecological and environmental problems that arise from the exploration of oil in the Niger Delta area

f)Liase with the various oil mineral and gas prospecting and producing companies on all matters of pollution prevention and control.

iv) Petroleum Related Laws and Regulations: According to the Federal Environmental Protection Agency, the following relevant national laws and international agreements are in effects:

a)Endanger Species Decree Cap 108 LFN 1990

b)Federal Environmental Protection Agency Act Cap 131 LFN 1990

c)Harmful waste Cap 165 LFN 1990

d)Petroleum (Drilling and Production) Regulations, 1969

v) The Environmental Impact Assessment (EIA) decree No.86 of 1992

• The EIA decree No 86 of 1992 was established to protect and sustain our ecosystem. The laws makes the development of an EIA compulsory for any major project that may have adverse effects on the environment. It sought to assess the likely or potential environmental impacts of proposed activities, including their direct or indirect, cumulative, short term and long term effects, and to identify the measures available to mitigate adverse environmental impacts of proposed activities, and assessment of those measures.

vi) Federal and State Agencies: A number of federal and state agencies deal with the problems of oil spill in Nigeria. The agencies include the Department of Petroleum of Petroleum resources (DPR), the federal ministry of Environment, the state ministries of Environment and national maritime Authority

vii)Effort of the Oil Companies and NGO: Owing to increasing awareness in preventing and controlling spills in Nigeria. The Clean Nigeria Associate (CAN) was formed in Nov. 1981. The CAN was a consortium of 11 oil companies operating in Nigeria. As a result of the focus on Shell activities in Nigeria and other oil producing companies established the Niger Delta Environmental Survey (NDES). The NDES was expected to provide:

a) A comprehensive description of the area, ecological zones, boundaries, and different uses of renewable and non-renewable natural resources;

b)An integrated view on the state of the environment and its relationship to local people;

c) An analysis of the casual relationship between land use, settlement patterns, industry and the environment, to provide a base line for future development planning;

d) An indicative plan for the development and management of the Niger Delta.

viii) Oil Trajectory and Fate Models for Oil Spill Disaster Monitoring:Oil spill simulation model is used in oil response and contingency planning and as a tool in oil fate and impact assessment.

ix) Nigerian Sat1: The Nigerian Sat 1 has joined the Disaster Monitoring Constellation, an international early-warning satellite network transmitting real-time information about droughts, earthquakes, deforestation and man-made disasters observable from space. The Nigerian Sat 1, an orbit satellite for geographical mapping, would also help to check the perennial problem of oil pipeline vandalisation, and assist in combating and managing oil spill incidents.

x) International Co-operation: To shore up the fight against oil smugglers in Nigeria, the US has donated three 56 m (180 ft) refitted World War two-era patrol oats to the Navy. The Nigerian navy has intercepted several tankers.

xi) Geographic Information System for managing Oil Spill Incidents: A successful combating operation to a marine oil spill is dependent on a rapid response from the time the oil spill is reported until it has been fully combated. In order to reduce the response time and improve the decision-making process, application of Geographic Information System (GIS) as an operational tool is essential.

xii) Environmental Sensitive Index (ESI) Mapping: ESI maps are basemaps that show the sensitivity of given locations or arenas to a particular stress factor (such as exposure to petroleum products) on a scale of 1 to 10, 10 being most sensitive. The maps may contain physical and geomorphic features (eg shorelines), biological features, and socioeconomic features such as agricultural fields.

xiii) Creating Awareness: Awareness creation on the impacts of oil spill is an integral part of management programme for oil spill along the coast of Nigeria. This is being carried out by government at different levels and agencies such as the NDDC.