ASSIGNMENT#2 Topic: Organic and inorganic pollutants Submittedto: Dr. Kiran HinaSubmittedby: Rabia-khalid 15051561-090 5th( B )Department: Environmental sciences Organicand inorganic pollutants Organic pollutants:Organic pollution occurs when largequantities of organic compounds, which act as substrates for microorganisms,are released into watercources. During the decomposition process the dissolvedoxygen in the receiving water may be used up at a greater rate than it can bereplenished, causing oxygen depletion and having severe consequences for thestream biota. Organic effluents also frequently contain large quantities ofsuspendid solids which reduce the light available to photosynthetic organismsand, on settling out, alter the characteristics of the river bed, rendering itan unsuitable habitat for many invertebrates. Toxic ammonia is often present.Organicpollutants consist of proteins, carbohydrates, fats and nucleic acids in amultiplicity of combinations.
Raw sewage is 99,9 per cent water, and of the 0,1per cent solids, 70 per cent is organic (65 per cent proteins, 25 per centcarbohydrates, 10 per cent fats). Organic wastes from people and their animalsmay also be rich in disease-causing (pathogenic) organisms. What are the origins of organic pollutants?Organic pollutants originate fromdomestic sewage (raw or treated), urban run-off, industrial (trade) effluentsand farm wastes. Sewage effluents is the greatest source of organic materialsdischarged to freshwaters.
In England and Wales there are almost 9000discharges releasing treated sewage effluent to rivers and canals and severalhundred more discharges of crude sewage, the great majority of them tot thelower, tidal reaches of rivers or, via long outfalls, to the open sea. It hasbeen assumed, certainly incorrectly, that the sea has an almost unlimitedcapacity for purifying biodegradable matter.Origin and Occurrence in Discharges A broad range of organic substances areproduced by human society and appear in discharges such as sewage, stormwaterand industrial discharges. These discharges can represent major sources of thepollutant substance. For example the concentration of organic pollutants insewage is low but the volume is large making it a major source of manypollutants. A similar situation applies with stormwater where these substancesoften originate from discharges from motor vehicles on to road surfaces and aresubsequently swept into waterways by storm run-off.
Motor vehicles are majorsources of petroleum hydrocarbons, polycyclic aromatic hydrocarbons and dioxinswhich are often discharged to the atmosphere in particulate form. Theseparticulates are deposited close to busy roadways leading to contamination ofurban soils and potential human exposure. Urban and industrial wastes areoften, either currently or in the past, disposed directly into pits dug intothe ground which leads to contamination of the soil and in some cases theadjacent ground water. Outside urban areas agricultural activities are themajor sources of pollutants. The growing of crops often involves the release ofpesticides into the environment, which can result in the contamination ofwaterways and soils, as well as the urban environment.
Perhaps the mostspectacular example of contamination of the environment is due to theaccidental spillage of petroleum. Over the years many disasters of this kindhave occurred releasing tens of thousands of tonnes of petroleum into theaquatic environment. Classes and Properties of OrganicPollutants The various types of organic pollutant can beplaced into three general classes:v Hydrocarbons,v Oxygen,v Nitrogen and phosphorus compounds orv Organometallic compounds. Probably the major category is thehydrocarbons and related compounds, which contains such compounds as DDT, thedioxins and the polycyclic aromatic hydrocarbons (PAHs). These compoundscontain the elements of carbon and hydrogen, with some containing chlorine andoxygen as well. There are a limited number of types of chemical bonds present,which are principally C-H, C-C, C-Cl, C=Cand C=C (aromatic). All of these bondsare relatively stable and have limited polarity and this property is thenconferred onto the related compounds. Some typical structures are shown inFigure 1.
As a result of the low polarity, thesecompounds are, in general, soluble in fat (i.e. lipophilic), poorly soluble inwater and persistent in the environment. Thus, they will be sorbed by sedimentand bioaccumulated by organisms (in fatty tissues) and have low concentrationsin water and air.
The lipophilicity of compounds can be measured in thelaboratory as the octanol-water partition coefficient ( ow K ). The higher theow K value the higher the lipophilicity. This class includes the most toxicorganic compound of abiotic origin, 2,3,7,8-tetrachlorodibenzo(1,4)dioxin, alsoknown as 2,3,7,8-TCDD or TCDD. The group containing oxygen, nitrogen andphosphorus compounds is very diverse but as a general rule it containscompounds with relatively high solubility in water, low fat solubility andrelatively low persistence in the environment. This is due to the presence ofbonds with relatively high levels of polarity due to carbon and other atomsbeing attached to oxygen, nitrogen or phosphorus conferring a high level ofpolarity onto the related compounds. As a general rule the ow K values arerelatively low, much lower than those of the hydrocarbons. In addition, suchbonds are relatively easily dissolved by environmental processes and consequentlysuch compounds are less persistent. The substances in this group only rarely formresidues in the environment due to their low persistence, low accumulation insediments and low bioaccumulation capacity in organisms.
The organometallicgroup is probably the least important from an environmental perspective andincludes compounds that are combinations of metal, such as lead and tin, withorganic components based on carbon. Figure 1: Chemical structures of some wellknown organic pollutants Persistent Organic Pollutants and Endocrine Disruptors: There are a group of chemicals which haveposed particular environmental problems due to their fat solubility,bioaccumulation potential and environmental persistence as well as usagepatterns. These are referred to as Persistent Organic Pollutants (POPs) andthese substances are often distributed over long distances up to a globalscale. POPs are commonly members of the hydrocarbon and related compounds group(see Figure 2) and include such compounds as DDT, PCBs and the dioxins (seePersistent Organic Wastes, Pathways of Organic Chemical Contamination inEcosystems).
The POPs have been associated with adverse biological effectsoften related to disruption of the endocrine system in organisms. The endocrinesystem is a complex array of glands and other organs that control hormonelevels within organisms. When POPs are taken up by an organism, even in verylow concentrations, they can disrupt the endocrine system causing hormonalchanges that can result in reproductive problems. In addition these compoundsare often carcinogens. There are several examples of the adverse effects ofPOPs on reproductive success in the natural environment. Perhaps the best knownis the effects of DDE on the reproductive success of birds. In recent times thenumber of endocrine disrupters has increased dramatically and now includes mostorganic pollutants as well as the range of other substances.
In addition therehave been reports of adverse effects, usually associated with reproduction, inrelationship to humans as well.The effects of organic effluents on receiving waters:When an organic polluting load iddischarged into a river it is gradually eliminated by the activities of microorganisms in a way very similar to the processes in the sewage treatment works.This self-purification requires sufficient concentrations of oxygen, andinvolves the breakdown of complex organic molecules into simple in organicmolecules. Dilution, sedimentation and sunlight also play a part in theprocess. attached micro organisms in streams play a greater role than suspendedorganisms in self-purification. Their importance increases as the quality ofthe effluent increases since attached microorganisms are already present in thestream, whereas suspended ones are mainly supplied with the discharge. Effects on the biotaOrganic pollution affects the organismsliving in a stream by lowering the available oxygen in the water.
This causesreduced fitness, or, when severe, asphyxiation. The increased turbidity of thewater reduces the light available to photosynthetic organisms. Organic wastesalso settle out on the bottom of the stream, altering the characteristics ofthe substratum. What is Inorganic Pollution?Inorganic Pollution are things foundnaturally but because of human production of goods have been altered todrastically increase the amount of them in the environment (some examplesinclude arsenic, lead, as well as many different air pollutants).Examples of Inorganic Pollution:v Leadv Zincv Copper Our first experiment was aimed atfiguring out exactly how Organic and Inorganic pollution effect soil acidity(Ph level) which can have a drastic affect on the environment; an example isthat in acidic ponds algae grows much more easily which can literally suffocatefish, killing them. For our second experiment we are trying to see how plant lifeactually grows in the soil that has an pollutant in it that will make its Phlevel lower than neutral, with a normal plant planted in regular soil as thecontrol. Classification of Inorganic chemicalpollutants Fig-2Classification of Inorganic chemical pollutantsLists some of the pure-inorganic chemical pollutants and theirharmful effects.
Table-1 Pure inorganic chemicalpollutants Pure-inorganic chemical pollutants Harmful affect Aluminium (Al) is a contributor to Alzheimer’s disease Arsenic (As) is highly toxic to humans and is chronic, or cumulative in human and animal organs Barium (Ba) affects the gastrointestinal tract and the central nervous system Beryllium (Be) is toxic to fish and aquatic life and various plants and inhibits photosynthesis in terrestrial plants Born (B) at approximately 1 to 4 mg/l, can be toxic to plants and at approximately 30 mg/l, can have physiological effects on animals and humans. Cadmium (Cd) affects metabolism and is quite toxic to animals and humans; it is cumulative in the kidney and liver organs and can cause death. Copper (Cu) at levels above 100 mg/l is highly toxic to animals and humans and can cause vomiting and liver damage.
Cyanide (CN) can be fatal at 8 mg/l. At low pH, CN forms hydrogen cyanide (HCN), which is a highly toxic, almond smelling mustard gas. Lead (Pb) it is cumulative in animal and human organs; with concentration greater than 0,5 mg/l causes lead poisoning. Plumbism is a disease caused by lead that affects the central nervous system of animals and humans. Certain tests have been developed toindicate water quality based on chemical characteristics that can be simpler,less expensive or more indicative of water quality than a chemical compoundstests.
CaCO3 is used as a standard for many of the indicatortests since its molecular weight is 100 and calculations are simplified.Table-2 lists description of some of the Chemical Indicator Tests.Chemical Indicator TestsTable- 2Chemical Indicator Tests (WaterQuality control Handbook) Chemical Indicator Tests Description Acidity is an indicator of capacity of water to react with a strong base to a designated pH.
Titration with a standard alkali solution to an end point of 3.8 pH is used for most wastewaters. Acidity is reported in mg/l of CaCO3. Alkalinity is primarily a function of the carbonate(CO3), bicarbonate (HCO3) and hydroxide (OH) content of wastewater.
Titration with a standard acid to an end point of 8.3 pH is reported as phenolphthalein alkalinity and titration to an end point of approximately 4.5 is reported as total alkalinity. Alkalinity is measured in mg/l as CaCO3.
Conductivity is a quantification of the ability of water to carry an electric current. Most conductivity tests are accomplished with an instrument. Total Hardness is generally a measure of the capacity of water to precipitate soap. Hardness is either calculated from the results of separate calcium and magnesium tests or is determined from a colour change when titrating a sample with ethylenediaminetetracetic acid (EDTA) Oil and Grease quantify substances that are soluble in trichlorotrifluoroethane. These tests will include the presence of certain sulfur compounds, organic dyes and chlorophyll that is not volatilised. Ph is used to indicate the intensity of the acidic or basic character of a solution.
Salinity is a measure of the dissolved salts in solution. mg/l Various pollutant limitations are shownin Table -3.Chemical inorganic Pollutant Limitations:Table-3Chemical Pollutant Limitations(Water Quality control Handbook) Chemical Drinking water protection Fish & Widlife protection Ammonia – 0.02mg/l Arsenic 50g/l – Barium 1mg/l – Beryllium – 11?g/l in soft water 1100 ?g/l in hard water Boron – – Cadmium 10g/l 4 ?g/l in soft water 12 ?g/l in hard water Chromium 50g/l 100 ?g/l Copper 1mg/l 0,1x 96 hr LC50 Cyanide – 5 ?g/l Reference:MackayD. (1991).
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