BEHAVIOR OF TRACE METALS IN AQUATIC SYSTEMS: EXAMPLE CASE STUDIES Environmental Biogeochemistry of Trace Metals (CWR6252)

Slides:

Advertisements

Similar presentations

Plasma Membrane.

Advertisements

Particle size Ions  molecular clusters  nanocrystals  colloids  bulk minerals Small particles can have a significant % of molecules at their surface.

Complexes Complex – Association of a cation and an anion or neutral molecule All associated species are dissolved None remain electrostatically effective.

CE 541 Complex Formation.

© 2011 Pearson Education, Inc. Key Concepts Plasma membranes are made up of selectively permeable bilayers of phospholipids. Phospholipids are amphipathic.

Aqueous Ionic Solutions and Equilibrium Chapter 19.

AP Biology Ch. 5.1 Plasma Membrane Structure and Function.

The Cell Membrane (Ch. 7) Phospholipids Fatty acid Phosphate Amphipathic – Phosphate head hydrophilic – Fatty acid tails hydrophobic Arranged as a bilayer.

The cells environment 1. All cells live in a fluid environment.

Mercury in the Environment. What is Mercury (Hg) Hg is a silvery, liquid metal at room temperature "heavy metals." Like water, Hg can evaporate and become.

Ch.3 Life on Earth is Aqueous!. Predominance of Water -3/4 of earth covered with water (liquid & solid) -cells are 70-95% water -all organisms require.

TRACE METALS - FROM DEFICIENCY TO TOXICITY Quest – July 22, 2004 Yeala Shaked, Yan Xu and Francois Morel, Geosciences Dept, Ecology and Evolutionary Biology.

CHAPTER 7 MEMBRANE STUCTURE AND FUNCTION The plasma membrane is selectively permeable Contains: ________ (mostly phospholipids) ___________ ______________(minor.

IS SOLUBILITY THE ONLY CONTROL ON SOLUTE CONCENTRATIONS? The answer is NO! Solubility often controls the concentrations of major solutes such as Si, Ca,

Ch.3 Life on Earth is Aqueous!. Predominance of Water -3/4 of earth covered with water (liquid & solid) -cells are 70-95% water -all organisms require.

Topic 1.3 Membrane Structure

The Chemical Cycle and Bioaccumulation of Mercury paper by: Francois Morel, Anne Kraepiel, and Marc Amyot presented by: Roxanne Myshkowec class: CE 468.

Essentials of Biochemistry Chemistry 360 Thomas J. Wiese, Ph.D. Assistant Professor of Chemistry Fort Hays State University.

Solubility Equilibrium In saturated solutions dynamic equilibrium exists between undissolved solids and ionic species in solutions Solids continue to dissolve.

“Keeping it all Together”

Cell Membrane. Function of Cell Membrane  Separates the cell’s contents from materials outside the cell  Regulates what moves in and out of a cell 

Complexes Complex – Association of a cation and an anion or neutral molecule Complex – Association of a cation and an anion or neutral molecule All associated.

BIOCYANIDE DEMONSTRATION PROJECT Activity III ; Project 5.

Acid-Base Reactions and Proton Accounting Lecture 20.

How H 2 0 interacts with: Itself –Hydrogen-bonding Ions and charged functional groups –Solvation, screening, dielectric value Non-polar groups –The hydrophobic.

 Elemental classification  Lewis acid/base  Pearson’s hard/soft metals  Ionic and covalent index  Ionic potentials  Earth Scientist's Periodic Table.

Maintaining a Balance. 1.The plasma membrane is a SELECTIVELY (SEMI-) PERMEABLE membrane that allows nutrients and wastes to enter and exit the cell.

1 The Turtle by Ogden Nash Ogden Nash The turtle lives 'twixt plated decks Which practically conceal its sex. I think it clever of the turtle In such a.

BEHAVIOR OF TRACE METALS IN AQUATIC SYSTEMS: EXAMPLE CASE STUDIES (Cont’d) Environmental Biogeochemistry of Trace Metals (CWR6252)

1 Selective Precipitation  a solution containing several different cations can often be separated by addition of a reagent that will form an insoluble.

The Plasma Membrane - Gateway to the Cell

Environments of cells All cells exist in a watery environment – extracellular fluid Mullticellular organisms have an outer layer that acts as a barrier.

 Elemental classification  Lewis acid/base  Pearson’s hard/soft metals  Ionic and covalent index  Ionic potentials  Electron negativity  Earth Scientist's.

Cell Membrane and Transport Maintaining homeostasis and providing nutrients to cells.

NOTES: CELL MEMBRANES (Structure & Functions)

Functions of the plasma membrane 1.Holds the cell together 2.Controls what goes in and out (diffusion, osmosis, active transport) 3.Protects the cell.

Plasma Membrane. Pre-Assessment 1.Which of the following statements concerning membrane proteins is incorrect? A.They can act as a channel, allowing the.

Aquatic Chemistry 367 Civil and Environmental Engineering Meeting time: MWF 11:00-11:50am Meeting room: Abbott Auditorium in Pancoe Pavillion Instructor:

1 Titration Curve of a Weak Base with a Strong Acid.

Basic Chemical Principals of Mercury

The Cell Membrane What does the cell membrane do? Separates living cell from aqueous environment Controls traffic in & out of the cell –allows.

1 2 It Matters! 3 Energy 4 Chemical Bonds 5 Oxidation - Reduction.

The Phospholipid molecule Hydrophilic – “water loving” Hydrophobic – “water fearing” Draw and label this: title:

6.1 Section Objectives – page 141 Relate the structure of an atom to the identity of elements. Section Objectives: Relate the formation of covalent and.

AP Biology The Cell Membrane AP Biology Overview  The cell membrane separates the inside of a living cell from its surroundings  Function to maintain.

Essential Chemistry for Biology. Matter is made of atoms.

Phospholipid A phospholipid is a type of lipid used in the cells of living things.

Basic Chemical Principals of Mercury

Learning Goal: Identify the major components of a cell membrane.

1 Water and the Fitness of the Environment chapter 3.

Lecture 21. Water-Related Complexes Ferric iron, will form a Fe(H 2 O) 6 3+ aquo-complex. The positive charge of the central ion tends to repel hydrogens.

What is a Liposome? A liposome is a tiny bubble (vesicle), made out of the same material as a cell membrane. Liposomes can be filled with drugs, and used.

THE CELL MEMBRANE The Key to Cellular Transport. Characteristics of the Cell Membrane  Made of phospholipids – arranged in two layers called a bilayer.

Review for Cell Membrane Structure & Molecular Movement Quiz!

Homeostasis and Cellular Transport. Cell Membrane A phospholipid bilayer that forms the outer membrane of a cell Is selectively permeable Controls which.

Biology Warm-Up 1. What is the function of the cell membrane? 2. What is the cell membrane composed of? Learning Goal  Understand the relationship between.

Membranes organize a cell’s activities Ch ► Plasma membrane acts as a cell’s boundary ► Regulates the traffic of chemicals that go in and out of.

Topic 13 - Periodicity. Ionic properties High melting and boiling point Conduct electricity in molten and aqueous states Crystalline solids Soluble.

Aquatic Chemistry 367 Civil and Environmental Engineering

Cell Membrane Structure

Solid-Water Interface

NOTES: CELL MEMBRANES (Structure & Functions)

9/1/2017 the Chemistry of Life.

Biogeochemical Cycle of Mercury (Hg)

Chemical bonds and Equations 2.1 and 2.4

Complexes Complex – Association of a cation and an anion or neutral molecule All associated species are dissolved None remain electrostatically effective.

9/1/2017 THE CHEMISTRY OF LIFE.

Made up of 3 organic molecules: - Lipids - Proteins - Carbohydrates Only allows certain molecules to pass through while blocking others out.

Biomolecules. Biomolecules The Water Life exists on Earth because of the abundant liquid water. Water has been referred to as the universal solvent.

Major Determinants of Water Quality

Presentation transcript:

BEHAVIOR OF TRACE METALS IN AQUATIC SYSTEMS: EXAMPLE CASE STUDIES Environmental Biogeochemistry of Trace Metals (CWR6252)

INTRODUCTION: I. Mercury as Example Trace Metal - Background

Hg Cycle

ARTISANAL GOLD MINING IN THE DEVELOPING WORLD

Artisanal Gold Mining by Hg-Amalgamation

GOLD EXTRACTION SITE (SLUICING)

Hg 2+ Hg 0 1. Hg reduction Evasion Atmospheric deposition SRB Hg 2+ MeHg SO 4 2- HS - 2. Uptake & methylation Hg 2+ + MeHg 3. Mobilization from sediments 4. Uptake by phytoplankton Phytop Zoopl Fish Humans Birds oxic anoxic Biomagnification Mercury in Water/Sediment ? MeHgHg 2+ MeHg demethylation Runoff

SO 4 2- Nutrients NO 3 NH 4 PO 4 2- Organic matter FOOD OXIC ANOXIC (No O 2 ) Less organic matter (Large particles) (More O 2 penetration) Fine particles (Large surface area) (Less O 2 penetration) IDEAL CONDITIONS FOR MERCURY TRANSFORMATION!!!!

The lipids in cell membranes are chiefly phospholipids such as phosphatidyl ethanolamine and cholesterol. Phospholipids are amphiphilic with the hydrocarbon tail of the molecule being hydrophobic; its polar head hydrophilic. As the plasma membrane faces watery solutions on both sides, its phospholipids accommodate this by forming a phospholipid bilayer with the hydrophobic tails facing each other. Cell Membrane Lipid bilayer Protein channels Transport across cell membranes

BIOACCUMULATION AND CELL TOXICITY Example pathway for Hg and other chalcophiles incorporation into proteins : Example: Two amino-acids play a key role metal toxicity:  Cysteine (cys): HOOC-CHNH 2 -CH 2 -SH  Methionine (met): HOOC-CHNH 2 -(CH 2 ) 2 -S-CH 3 These amino-acids serve as point of attach for CHALCOPHILIC metals to proteins S Bio-concentration/Bio-accumulation Octanol-water coefficient (K ow = [C octanol ]/[C water ])

Bioaccumulation & Biomagnification Mercury in Water PlanktonOmnivorous Fish Carnivorous Fish Birds Man Hydrosphere Pedosphere Mercury in Soil PlantsAnimals/ Birds Man Atmosphere Mercury in Air PlantsAnimals /Birds Man

Example Health Impact due to Hg Exposure

PART-1

1. Metals in Water with no other Ligands than H 2 O Metals would form “ AQUO COMPLEXES ” of metals and even loose protons  The pH of solution is important in determining whether protons are lost  Leads to an acid-base type reaction with the following general equation  Deprotonation steps are favored mostly in the case of highly charged and small radius ions (high Z 2 /r). This relationship holds true primarily for the main group elements, and other factors become important for transition metals, especially the heavy ones by omitting the waters of hydration

Values of Z 2 /r and pKa 1 for aquo-complexes of a few selected metals  pKa 1 = pH at which the aquo complex is at 50% fully protonated and 50% with less 1 proton  From the Table +1 metal ions would occur exclusively as fully protonated hydrated species throughout the entire pH range For +2 ions, deprotonation occurs more readily for smaller species (high Z 2 /r) Be(OH) + dominates at pH of 6.5 and above Mg(OH) + would need pH>11 Deprotonation becomes significant in environmentally common situations for +3 metals (e.g. Fe 2+ ) and +2 heavier metals (e.g. Hg 2+ )  This process can also lead to the formation of polynuclear species Metal ionsZ 2 /r (nm -1 )pKa 1 Na K+K+ 6.6>14.00 Be Mg Mn Fe Co Ni Cu Zn Cd Hg Al Fe o o

Mercury (Hg) as Example Trace Metal  Hg is a type B metal with a very high covalent index (X 2 m *r) and a low ionic index (Z 2 /r)  Earth’s crust abundance of ~89 ng/g and mostly as Hg 0 and HgS  Stable oxidation sates: 0, +1, and +2  Most important aqueous species = Hg 2+, particularly under oxidized conditions  In water containing no ligands, deprotonation occurs even in moderately acidic conditions (pH ~4) to give Hg(OH) + and Hg(OH) 2 as dominant species. For example, using Hg with a coordination number of 4:

Eh-pH Diagram with water as ligand

2. Metals in Water with Ligands 2.1. Chloride as example single ligand in water containing Hg log [Cl - ] Hg 2+ HgCl 2 HgCl + HgCl 3 - HgCl Distribution of Hg chloro-complexes in water as a function of chloride concentration.

Eh-pH Diagram with Cl - as ligand

PART#2