Chemical and biochemical change

Chemical and biochemical change

Chemical and biochemical changes 2(iii) a. Hydrolysis b. Redox reactions c. Photo induced reactions d. Transition metal complexes Aims (i) to provide overview of main concepts and terminology in chemical and biochemical changes. (ii) to discuss possible soil, atmospheric and aquatic systems environmental processes. (iii) To discusses of bio-physico-chemical processes of metals and metalloids in soil, atmospheric and aquatic

systems. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 2 Outcomes (i) students will be able to evaluate hydrolysis, redox reactions, photo induced reactions, transition metal complexes and biochemical transformations. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 3

Outcomes: (ii) Students will be able to determine and discuss about fundamentals of biotic and abiotic interactions of metals and metalloids with soil components contain six chapters, which deal with: - impact of physico-chemical-biological interactions on metals and metalloid transformations in soils; - transformation and mobilization of metals, metalloids and radionuclides by microorganisms; - kinetics and mechanisms of sorption/desorption in soils; - spectroscopic techniques for studying metal-humic complexes in soil; - factors affecting the sorption-desorption of trace elements in soil; - modelling adsorption of metals and metalloids by soil

components. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 4 Outcomes: (iii) Students will be able to predict possible environmental behavior of charged species due to clay/organic matter content of surface. Knowledge on the mechanisms and assessment of P-induced Pb immobilization in situ and water. Students will be able to predict possible ways of monitoring the process and to assess the mechanisms of reactions in the soil, air and water.

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 5 Chemical and biochemical changes A chemical change is a phenomenon quite different from a physical change. If liquid water boils or freezes (both of which are examples of a physical change resulting from physical processes), it is still water. Physical changes do not affect the internal composition of an item or items; a chemical change, on the other hand, occurs when the actual composition changes that is, when one substance is transformed into another. Chemical change requires a chemical

reaction, a process whereby the chemical properties of a substance are altered by a rearrangement of atoms. Biogeochemical processes from soils affect the fate behaviour and bioavailability of metals and metalloids in soils. Read more: Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes Read more: http://www.answers.com/topic/nitrogen-cycle#ixzz1lci9t1yE 6 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 7

Schematic representation of the flow of nitrogen through the environment. The importance of bacteria in the cycle is immediately recognized as being a key element in the cycle, providing different forms of nitrogen compounds assimillable by higher organisms. http://www.answers.com/topic/nitrogen-cycle#ixzz1lci9t1yE Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

8 A schematic presentation of the Marine Nitrogen Cycle http://www.answers.com/topic/nitrogen-cycle#ixzz1lci9t1yE Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 9 a. Hydrolysis Chemical reaction in which water (H2O or HOH) and another reactant exchange functional groups to form two products, one takes the H and the other one, the OH. For example, an ester can be hydrolyzed to form

a carboxylic acid and an alcohol. In most hydrolyses involving organic compounds, the other reactants and products are neutral; Such reactions are often accelerated by enzymes (as in much of digestion and Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

metabolism in general) or other catalysts. 10 Hydrolysis is the name for a reaction in which substance chemically reacts with water. Hydrolysis should be distinguished from solvation, which is the process of water molecules associating themselves with individual solute molecules or ions. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 11

I. Salts of Weak Acids In general, all salts of weak acids behave the same, therefore we can use a generic salt to represent all salts of weak acids. Let NaA be a generic salt of a weak acid and A its anion. Here are two specific examples of salts of weak acids: Substance Formula The anion portion (A) sodium acetate NaC2H3O2

C2H3O2 sodium benzoate C6H5COONa C6H5COO Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 12 The generic chemical reaction (in net ionic form) for hydrolysis may be written: A + H2O HA + OH

This reaction is of a salt of a weak acid (NOT the acid) undergoing hydrolysis. The salt is NaA, and it reacts with the water. Keep in mind that the acid (HA) does not undergo hydrolysis, the salts ion(s) do(es). By the way, the potassium ion, K+, (and several others) could also be used above without affecting any discussions of this topic. As a practical matter, only Na+ and K+ tend to get used in examples. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 13 However, keep in mind that Na+ is present in the solution. Some teacher

might want to ask a "sneaky" question on a test. It is important to notice several things: 1) The Na+ (notice only OH is written) IS NOT involved. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 14 2) HA is the UNDISSOCIATED acid. 3) There are free hydroxide ions (OH) in the solution!! This is the thing that makes the pH greater than 7. Keep in mind that it is not the acid that makes the acidic pH of a solution, it is the amount of hydrogen ion (or hydronium

ion, H3O+, if you wish). In order to produce the hydrogen ion, the acid must dissociate. Now, I can see a question forming in your mind. If there is acid (HA) and base (OH), why don't they just react and give back the reactants on the left side? Now, that really is a good question. The answer? This reaction is an equilibrium. Now, if you are taking chemistry for the first time, you probably just got done with equilibrium a few weeks ago and it might have been hard to understand. That's understandable, but please realize that equilibrium is one of more important concepts in chemistry. Keep up the work!! Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 15

When a chemical reaction comes to equilibrium, there is a mixture of all involved substances in the reaction vessel. This mixture is characterized by a constant composition. The key point that makes a reaction come to equilibrium is that it is reversible. (Keep in mind that constant composition DOES NOT imply equal composition.) So, while it is true that the HA and OH will react in the reverse direction, so can the A and the H2O in the forward direction. The key point is that thereverse reaction happens in small extent. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

16 The important points will be (1)how much OH is formed and (2) what is the pH of the solution? Quick answers: (2)the amount of OH formed will be >10-7 M (present in pure water) and (3)the pH will be greater than 7, so the solution of the salt of a weak acid should be basic. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 17 II. Salts of Weak Bases

HB+ is usually not considereds as a salt, but as a conjugated acid of the base. (Compare how this is worded compared to the "salt of weak acid" discussion.) HB+ is a cation, but that word is not used as much in discussions as is "anion" is above. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 18 Substance Formula

The cation portion (HB+) ammonium chloride NH4Cl NH4+ methyl ammonium nitrate CH3NH3NO3 CH3NH3+ HNH3+ : NH3 is the base (symbolized by B) and an H+ has

been attached to it in a chemical reaction. The NH3 has been protonated and the result (NH4+) is now an acid. Why? Because it now has a proton to donate. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 19 Its source is the salt (HB+Cl) that is dissolving in the water and it DOES NOT affect the pH. Its presence in writing the appropriate chemical reactions and doing the calculations is omitted. However, keep in mind that Cl is present in the solution.

Some teacher might want to ask a "sneaky" question on a test. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 20 Now, I can see a question forming in your mind. If there is base (B) and acid (H3O+), why don't they just react and give back the reactants on the left side? Now, that really is a good question. The answer, of course, is given in above in the discussion of salts of weak acids. It would be the same explanation here, so I won't repeat it. What you might want to do,

however, is look at the different phrasing in part I as compared to part II. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 21 When calculations are done, the important points will be (1) how much H3O+ is formed and (2) what is the pH of the solution? Quick answers: (1) the amount of H3O+ formed will be greater than the 10-7 M (present in pure water) and (2) the pH will be less than 7, so the solution of the salt of a weak base will be acidic.

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 22 Hydrologic cycle The hydrologic cycle has critical role in some of the most important ecosystem feedbacks between organisms and the physical environment. Ecosystems both respond to water availability ,and change water availability. Soil moisture is one of the major regulators of plant growth and the productivity of terrestrial ecosystems. At the same time, plants remove water from the soil and release it into the atmosphere.

Water influences climate through evaporative cooling, cloud formation, and precipitation. Water not removed by plants or evaporation moves over or through the soil into streams and rivers and, ultimately, the ocean. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 23 Water is unevenly distributed among aquatic enviroments such as lakes, rivers, and ocean: most is seawater. The situation on earth is indeed as Samuel Coleridges ancient mariner saw it: Water, water, everywhere, nor

any drop to drink. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 24 b.Redox Reactions Redox reactions, have a number of similarities to acidbase reactions. Fundamentally, redox reactions are a family of reactions that simply because we need two (2) half-reactions to form a whole reaction. This half-reaction says that we have solid copper (with no charge) being oxidized (losing electrons) to form a copper ion with a plus 2 charge. Notice that, like the stoichiometry notation, we have a "balance"

between both sides of the reaction. We have one (1) copper atom on both sides, and the charges balance as well. Chemists typically write out the electrons explicitly: Cu (s) Cu2+ (aq) + 2 eEnvironmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 25 The symbol "e-" represents a free electron with a negative charge that can now go out and reduce some other species, such as in the halfreaction: 2 Ag+ (aq) + 2 e- 2 Ag (s) The abbreviations "aq" and "s" mean aqueous and solid, respectively.

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 26 We can now combine the two half-reactions to form a redox equation: Cu(s) Cu2+ (aq)+2e 2Ag+ (aq)+ 2e2 Ag(s) ------------------------------------- Cu(s)+2Ag+ (aq)+ 2eCu2+ (aq)+2Ag(s)+2e- or Cu(s)+2Ag+ (aq) Cu2+ (aq) +2Ag(s) Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 27

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 28 An external electric current hooked up to an electrochemical cell will make the electrons go backwards. This process is called electrolysis. This is used, for example, to make something gold plated. You would put the copper in a solution with gold and add a current which causes the gold ions to bond to the copper and therefore coating the copper. The time, current, and electrons needed determine how much "coating" occurs. The key to solving electrolysis problems is learning how to convert between the units.

Useful information: 1 A=1 C/sec; 96,500 coulombs (1 Faraday) can produce one (1) mole of e-; the electrons needed for deposition on electrode is determined by the charge of the ion involved. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 29 Example Problem: If you are trying to coat a strip with aluminum and you have a current of 10.0 A (amperes) running for one hour, what mass of Al is formed? The solution of this problem involves a lengthy unit conversion process:

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 30 The reference electrode In practice, the redox potential difference is measured with respect to a standard electrode. The standard electrode is a hydrogen half-cell, with the reaction in which all components are in their standard states (1 atm pressure for the gas, 1M activity for the proton, or pH=0).

H2 (g) 2 H+ (aq) + 2 eEnvironmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 31 Reference electrodes provide a standard redox reaction that will accept or release electrons to the soil solution. Two types of reference electrodes are in use: Ag/AgCl and Calomel. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 32

The Ag/AgCl electrode consists of a Ag metal wire and a AgCl salt. The basic reaction is: Ag Ag+ + eWhen the reaction goes to the right (Ag is oxidized) the electron is sent to the voltmeter and could be transmitted to the Pt wire to reduce chemicals in the soil solution if the voltmeter were not present. If the reaction goes to the left then an electron comes from the voltmeter into the electrode. The Ag and Ag+ are surrounded by a solution of KCl which maintains electrical neutrality. When the reaction above goes to the right, then a K+ is released to the soil through the ceramic tip of the electrode. When the reaction goes to the left then a Cl- anion is released through the ceramic tip. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

33 Schematic presentation of referent electrode set-up http://www.water-research.net/course/RedoxWriteup.pdf Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 34 Another type of reference electrode in common use is the calomel which contains Hg. The basic reaction is: Hg Hg++ eThis electrode works the same as the Ag/AgCl. While both kinds of reference electrodes give reliable data, the voltages measured with each electrode

are interpreted slightly differently. It is for this reason that users must know which electrode they have. The voltage measured in the field must be corrected to what would have been obtained with a different reference electrode, called the standard hydrogen reference electrode. This electrode cannot be used in the field, but our interpretations of redox potential measurements are based on values determined with it. Therefore, all voltages measured in the field with either the Ag/AgCl or calomel reference electrode have to be adjusted to the value that would have been obtained had a standard hydrogen electrode been used. The basic correction factors are Ag/AgCl in saturated KCl solution +200 Calomel+250 These correction factors are temperature dependent, but in most instances the effect of temperature is much lower than the variability in the data for a given time. Therefore, a temperature correction is not necessary unless very precise measurements are required.

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 35 Formula for Converting Field Data to Redox Potential: Field Voltage +Correction Factor = Redox Potential (Eh) The symbol Eh or EH is used to indicate a voltgage that has been corrected to what would have been obtained with a standard hydrogen electrode. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 36

Relation between electrode potential and free energy of reaction The complete reaction of an electrochemical cell can be treated like any other reaction, using the equation for G' presented inan earlier page. G' presented in an earlier page. Since the activity terms in the logarithmic ratio are the same as the activity terms in the equations for E above, it is a straightforward exercise to substitute among equations to find the relation between E and G' presented inan earlier page. G. This gives the following relationships: G' presented inan earlier page. G' = -zF G' presented inan earlier page. E' G' presented inan earlier page. Go = -zF G' presented inan earlier page. Eo G' presented inan earlier page. Go' = -zF G' presented inan earlier page. Eo'

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 37 c.Photoinduced reactions Dark Reactions Most organic compounds react very slowly, even with oxygen, at normal temperature. As a rule, they can be considered generally nonreactive. BUT !... Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 38

Let Be Light ! Visible and ultraviolet radiation can promote the reactivity of almost all compounds. Recall a well known fact that items exposed (northern hemisphere) on southern side of buildings decay more quickly than those on northern side. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 39 On the side facing south, the wooden (and

metal) items decay faster Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 40 Museum item Side exposed to light Side not exposed to light Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

41 Basics of Photochemistry Primary photophysical process. Subsequent chemical change(s) Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 42 Photophysical process Actually, it means absorption of light quanta. It promotes molecule from ground- to excited state (energy rich one). But, to catch the light quanta, molecule has to

have a CHROMOPHORE ! Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 43 Chromophores Chromophores are structural details in molecule(s) that enable high(er) probability of light absorption. Normally, it comprises double bonds in molecule, i.e., -electrons: Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

44 Chromophore Double bond C=C Aromatic ring Far more efficient are polarized double bonds. C=O:

C=N- Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 45 Photophysical process Once molecule acquires light quantum, it has many ways to decay, involving the chemical change. Simplified approach tells that molecule can exist in ground state singlet or triplet The same holds for excited state Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

46 S0 Ground-state singlet S1

Excited-state singlet T1 Excited-state triplet Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 47

Jablonski diagram E MO Description E S1 S0 T1 S1

(c) T1 h (a) (b) h S0 (c) (d)

h h (b) h h (a) (d) r

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 48 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 49 Singlets and triplets are known as multiplicities of state. Electronic transition among states of different multiplicities is not likely to happen (is forbidden), But, as many other things, something

forbidden still could happen. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 50 These violations could be promoted by, so called, SENSITIZERS. HO + O OH

CN N COO Me 2 N S + NMe 2 CN Fluoresceine

ee Methylene blue Dicyanoanthracene Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 51 Sensitizers quickly, and in good yields populate excited triplet states.

E S1 T1 h (a) Triplets live long enough to encounter other molecules. (c)

(b) h (d) h S0 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 52 Sensitization

Sens (S0) Sens (S1) h Sens (S1) intersystem Crossing Sens (T1) Sens (T1) + VOC (S0) )))) Sens (S0) + VOC (T1)

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 53 Photophysics Photochemistry C=O: Norrish type I CH3-CO-CH3 h CH3CO + CH 3 )) CH3COCOCH3 + CH3CH3

Norrish type II R R R h O H R O H

R OH + R Enol Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 54 Primary chemical intermediates in

photochemical metathesis are organic free radicals. Free radicals are highly reactive. Radicals react with almost everything! Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 55 Additional sensitization (singlet oxygen) Sens (S0) h

Sens (S1) Sens (T1) + O2 (T0) Sens (S1) intersystem crossing Sens (T1) )))) Sens (S0) + O2 (S1) Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

56 Coatings & Erosion VOC-s exposed to light can be promoted to more reactive compounds. Oxygen-containing derivatives can be aggressive to living organisms and to artifacts. Reactive intermediates may lead to polymers, forming sticky coating. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 57

Everything matters Ozone is not emitted directly from industrial sources and vehicles. It is formed in troposphere as a result of reactions involving oxides of nitrogen and volatile organic compounds. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 58 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 59

Internet Resources http://www.iaq.dk/index.html http://www.airclim.org/airAndEnvironment/AE_chp3.htm http://www.epa.gov/region4/airqualitytoolkit/10_Glossaries/U S NPS - Air Quality Glossary.pdf http://www.heritage.xtd.pl/pdf/full_czop.pdf http://www.epa.gov/iaq/voc.html http://www.environment.gov.au/soe/2006/publications/comme ntaries/atmosphere/glossary.html http://www.airimpacts.org/documents/local/aqbook.pdf Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 60

d.Transition metal complexes Transition metal complexes Transition metals and their common oxidation states What is a metal complex? Geometries of complexes Common ligands Isomerism in coordination complexes Naming transition metal complexes Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 61

Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 62 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 63 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 64 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

65 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 66 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 67 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 68 Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes

69 Video recording. http://www.youtube.com/watch?v=TD0JbxPmuMg Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 70 Video recording. http://www.youtube.com/watch?v=osLRRoUnhKQ Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 71

Redox reactions mechanisms and examples on how to solve a problem Video recording. http://www.youtube.com/watch?v=xbaa2CpNEbk Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 72 Methodology Preparation of sample The soil and sludge were collected and prepared in London in 1990 (Nouri, et al.,1980). Duplicate 250 grams samples of air dried sewage sludge/soil mixtures comprising 100, 90, 80, 50 and 0 per cent soil were placed in sintered glass membrane filter funnels and kept at the field capacity moisture by regular watering

with deionised water. Soil solution was extracted by placing the funnel in a suction flask linked to a vacuum line. The first early extraction produced very little filtrate so an improved standardized procedure was adapted in which 40 ml of deionised water was slowly added to the mixtures, 30 minutes before vacuum filtration. This filtrate was more realistically a saturation extract than a representative sample of soil solution. After filtration the pH values of the filtrates were determined and sub samples were taken to dryness with concentrated nitric acid to destroy any soluble organic molecules prior to chemical analysis. For comparative purposes, small sub samples of the sludge/soil mixtures, taken at the beginning and end of the experiment, were extracted with water and the metal concentrations determined in the extract (McLaren and Crawford, 1973). Twelve saturations extracts were obtained over a period of eight months. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 73

Conclusion The model equation developed for the mobility of heavy metals in the soil contaminated with sewage sludge is given as: The analysis of the result shows that there is a very good level of agreement between the experimental and simulated results obtained. This can also be confirmed by the statistical analysis of the result through the correlation coefficient found to be 0.9983, 0.9999, and 1.000 for 100% soil, 90% soil and 50% soil respectively. In conclusion, the model developed can be considered to be a good representation of the phenomenon of mobility of metals in the soil. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 74

where: C = Concentration of solute; DL = Hydrodynamic dispersion coefficient; vx = Pore velocity along flow path; b = solid density; = porosity for saturated conditions; C = Mass of solute sorbed per dry unit weight of soil. This equation contains a term for dispersion, advection, and sorption (Vince DeCapio, 2003). Knowing that C" = kd C Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 75 References:

1. 2. Paul, Eldor Alvin - "Soil Microbiology and Biochemistry" - Academic Press is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA Linacre House, Jordan Hill, Oxford OX2 8DP, UK Third edition 2007 ISBN 13: 978-0-12-546807-7 William R. Horwath - "Carbon cycling and Formation of soil organic Matter - Academic Press is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA Linacre House, Jordan Hill, Oxford OX2 8DP, UK Third edition 2007 , ISBN 10: 0-12-546807-5, Page:303-467 3. Hartmut Yersin Electronic and Vibronic Spectra of Transition Metal Complexes II

Springer-Verlag Berlin Heidelberg ,New York .1997 . Printed in Germany. ISSN 0340-2033. Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 76 4. A.G. Khan, C. Kuek, T.M. Chaudhry, C.S. Khoo, W.J. Hayes " Environmental Chemistry"; Stanley E. Manahan - New York Washington D.C. 2000, ISBN 99-047521 5. A.G. Khan, C. Kuek, T.M. Chaudhry, C.S. Khoo, W.J. Hayes A.G. Khan Role of plants, mycorrhizae and phytochelators in heavy metal contaminated land remediation - Chemosphere 41 (2000), pg 197-207, PII: S0045-6535(99)00412- 9 6. Martin N. Hughes and Robert K Pool

"Metal speciation and microbial growth-the hard (and soft) facts - Journal of General Microbiology (1991) Great Britain, pg 137, 725-734; doi: 10.1099/00221287-137-4-725 7. Mark Fungayi Zaranyika and Tsitsi Chirinda " Heavy metal speciation trends in mine slime dams: A case study of slime dams at a goldmine in Zimbabwe , Academic Journals, 14 March, 2011. ISSN-2141-226X Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 77 8. Hooda P. S., McNulty D., Alloway B. J., Aitken M. N. Plant availability of heavy metals in soils previously amended with heavy application of sewage sludge, J. Sci of Food and Agric., 1997, 73, p. 446-454.

http://onlinelibrary.wiley.com/doi/10.1002/(SICI)10970010(199704)73:4%3C446::AID-JSFA749%3E3.0.CO;2-2/abstract 9. Camobreco V. J., Richards B. K., Steenhuis T. S., Peverly J. H., McBride M. B. Movement of heavy metal through undisturbed and homogenized soil columns, Soil Science, 1996, 161:740-750. 10. http://en.wikipedia.org/wiki/Hydrolysis http://www.lenntech.com/waterglossary.htm#ixzz1lcdQ6E4F https://www.novapublishers.com/catalog/product_info.php? products_id=2951 http://ww2.chemistry.gatech.edu/~wilkinson/Class_notes/CHEM_3111_61 70/Intoduction_to_transition_metal_complexes.pdf Environmental processing / Fundamental processes in soil, atmospheric & aquatic systems / Chemical and biochemical changes 78

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