Today: April 9• Lab Discussion• Papers Due• Newspaper Articles: Johnny and Ashley• Chapter 5: The Water We Drink

– Notes– Activity– Worksheet

For Next Time: April 14• Homework #4 Due• Lab – Anyone willing to drive?

Water, water, every where, And all the boards did shrink; Water, water, every where, Nor any drop to drink.

And every tongue, through utter drought, Was withered at the root; We could not speak, no more than if We had been choked with soot.

The Rime of the Ancient MarinerSamuel Taylor Coleridge

Chapter 5: The Water We Drink

“Water has never lost its mystery. After at least two and a half millennia of philosophical and scientific inquiry, the most vital of the world’s substances remains surrounded by deep uncertainties. Without too much poetic license, we can reduce these questions to a single bare essential: What exactly is water?”

Philip Ball, in Life’s Matrix: A Biography of Water,University of California Press,Berkeley, CA, 2001, p. 115

Do you know where your drinking water comes from?

Do you know if your drinking water is safe to drink?

How would you know?

Sources of Drinking Water

• Lake Water• Ground Water• Rivers

– (The water quality in lakes, rivers and ground water are severely impacted by man. We have learned through our mistakes how we need to protect these resources, and how these resources behave.)

• (Oceans-rarely)

Where Does Potable(fit for consumption) Drinking Water Come From?

Surface water: from lakes, rivers, reservoirsGround water: pumped from wells drilled into underground aquifers

5.2

Clean water in small towns and private wells comes from underground aquifers. The Ogallala Aquifer is shown in dark blue.

While normally free of pollutants, groundwater can be contaminated by a number of sources:

Abandoned mines

Poorly constructed landfills and septic systems

Run off from fertilized fields

Household chemicals poured down the drain or on the ground.

The average American uses almost 100 gallons of water a day.

Nearly ¾ of the water entering our homes goes down the drain.

5.2

Clean water in cities comes mostly from surface waters.

5.14

Access to safe drinking water varies widely across the world.

5.3

A solution is a homogeneous mixture of uniform composition.

Solutions are made up of solvents and solutes.

Substances capable of dissolving other substances- usually present in the greater amount.

Substances dissolved in a solvent- usually present in the lesser amount.

When water is the solvent, you have an aqueous solution.

Key terms related to water• Ground water

- water that exists below the water table where saturated conditions occur

• Aquifer

- underground zone containing sufficient ground water that can be used

• Solvent –

medium in which other substances are dissolved

• Solutes – substances dissolved in the solvent• Solution

– contains the solvent and solutes• Aqueous solution

– water is the solvent• Mineral –

a naturally occurring element or compound with a definite chemical composition and crystal structure

Mineral Composition in Tap and Bottled Water

Where Do Bottled Waters Come From?

• Aquafina® This well-known bottled water brand produced by PepsiCo is derived from a municipal source and goes through a purification process that uses charcoal filtration, reverse-osmosis, ozonination and other elements of the process. During purification, virtually all of the natural minerals are removed from the water, giving it a light, mellow taste.

• Dasani® Coca-Cola's flagship purified bottled water brand is also derived from a municipal source and undergoes a reverse-osmosis-based purification process. However, Dasani® gets a blend of minerals added back after the purification process, giving it a crisp taste.

• Evian® This upscale spring water comes from a source in the northern French Alps. The water is collected from an aquifer that is fed by snowmelt and rainfall. Other than filtration through the ground's sand and clay, no other purifying process is used to produce this bottled water.

http://www.evian.com/us/

10 Minute ActivityBottled Water Claims: Many bottled water companies claim their products have unusual properties and are good for human health. Let’s examine one such water: Penta Water. Penta Water: http://www.pentawater.com/_pw/ourprocess.php?sub=1&item=2

5.4

Parts per hundred (percent)

Parts per million (ppm)

Parts per billion (ppb)

Molarity (mol/L)

20 g of NaCl in 80 g of water is a 20% NaCl solution

Concentration Terms

waterLsoluteg

waterLwaterg

solutegsoluteg

waterg

soluteg1

11

10001101

101

1ppb1

6

9

μμ=×

××

×=

Molarity (M) = moles soluteliter of solution

1.0 M NaCl solution

[NaCl] = 1.0 M = 1.0 mol NaCl/L solution

[ ] = “concentration of”

5.4

5.4

How to prepare a 1.00 M NaCl solution:

Note- you do NOT add 58.5 g NaCl to 1.00 L of water.The 58.5 g will take up some volume, resulting in slightly more than 1.00 L of solution- and the molarity would be lower.

mol soluteL of solutionM =

Concentration ProblemsWhat is the concentration (in mass %) of the resulting solution when you add 5 grams of NaOH to 95 mL of water?

What is the concentration (in ppm) of the solution made when you add 0.2 grams of NaCl to 100 mL of water?

What is the molarity of glucose (C6 H12 O6 ) in a solution containing 126 mg glucose per 100.0 mL solution?

Describe how you would make a liter of a 2 M solution of CaCl2 .

Describe how you would make a 100 mL of a 0.2 M solution of CaCl2 .

Today: April 14• Evaluations• Wind Lab Discussion • Newspaper Articles: Meghan and Laura• Chapter 5: The Water We Drink

– Properties of Water– Finish In-Class Worksheet

• Homework #4 Due

For Next Time: April 16• Read Chapter 5, Start Chapter 5 Homework• Lab – Anyone willing to drive?

Properties of Water

5.5

Different Representations of Water

Lewis structures Space-filling Charge- density

Charge-density

Region of partial negative charge

Regions of partial positive charge

Water has some WEIRD Properties

• Liquid at room temperature despite low molar mass• High boiling point• Expands when it freezes

Properties of Water

• Water is transparent and allows sunlight to penetrate allowing photosynthesis to take place in oceans, rivers, and lakes

• Water is the only liquid that forms a solid that is lighter than the liquid. Thus ice floats.

• As ice is formed the clusters of molecules create larger more rigid structures and this causes the volume to increase during freezing.

Properties of Water

• Water has a high specific heat – The quantity of heat required to raise the temperature

of one gram of a substance one degree C– it takes a lot heat to evaporate water or to melt ice.

• Water is a good solvent– Many inorganic and organic chemicals can dissolve in

water.

5.5

EN Values assigned by Linus Pauling, winner of TWO Nobel Prizes.

Electronegativity is a measure of an atom’s attraction for the electrons it shares in a covalent bond.

On periodic table, EN increases

5.5

HH

O

A difference in the electronegativities of the atoms in a bond creates a polar bond.

Partial charges result from bond polarization.

A polar covalent bond is a covalent bond in which the electrons are not equally shared, but rather displaced toward the more electronegative atom.

5.5

H HH2 has a non-polar covalent bond.

NaClNaCl has an ionic bond-look at the EN difference.

Na = 1.0

Cl = 2.9

ΔEN = 1.9

A water molecule is polar – due to polar covalent bonds and the shape of the molecule.

ΔEN Ionic Character> 1.7 Mostly Ionic

0.4 -1.7 Polar Covalent< 0.4 Mostly Non-Polar

Covalent

5.6

Polarized bonds allow hydrogen bonding to occur.

H–bonds are intermolecular bonds.Covalent bonds are intramolecular bonds.

A hydrogen bond is an electrostatic attraction between an atom bearing a partial positive charge in one molecule and an atom bearing a partial negative charge in a neighboring molecule. The H atom must be bonded to an O, N, or F atom.

Hydrogen bonds typically are only about one-fifteenth as strong as the covalent bonds that connect atoms together within molecules.

Why does ammonia, NH3 , have similar properties?

Properties of Solutes

When things are added to water, the resulting solution can have new properties …

Watch the following video and make observations on what is happening…http://www.youtube.com/watch?v=Rf2mS4J0FNg

1. What property changes during the video? 2. Why does the light bulb conduct electricity when the salt is added? 3. What would happen if you added sugar instead of salt?

5.7

When ions (charged particles) are in aqueous solutions, the solutions are able to conduct electricity.

(a) Pure distilled water (non-conducting)

(b) Sugar dissolved in water (non-conducting): a nonelectrolyte

(c) NaCl dissolved in water (conducting): an electrolyte

Some things are weak electrolytes – only a fraction of the molecules form ions and the conduction is therefore weaker

+ 1 e-Na Na

Na atom Na+ ion

Forming ions

+ 1 e-

Cl atomCl- ion

ClCl

5.7

Ionic Bonds: Electrostatic Bond between positive and negative ions

5.7

Substances that will dissociate in solution are called electrolytes.

Dissolution of NaCl in Water

The polar water molecules stabilize the ions as they break apart (dissociate).

Ions are simply charged particles-atoms or groups of atoms.

They may be positively charged – cations.

Or negatively charged- anions.

NaCl(s) Na+ (aq) + Cl-(aq)H2 O

Some atoms form more than one stable ion

5.7

Naming simple ionic compounds is easy-

Name the metallic element (cation) first, followed by the non-metallic element (the anion) second, but with an –ide suffix.

5.7

MgO Mg is the metal, O is the non-metal

magnesium oxide

NaBr Na is the metal, Br is the non-metal

sodium bromide

5.7

Ions that are themselves made up of more than one atom or element are called polyatomic ions.

NaSO4 (sodium sulfate) dissociates in water to form:

Na+

Sodium ions

and

Sulfate ions

The sulfate group stays together in solution.

Naming polyatomic ionic compounds is also easy-

Name the cation first, followed by the anion second.

5.7

MgOH Mg+ is the cation, OH- is the anion

magnesium hydroxide

NH4 Br NH4+is the anion, Br- is the anion

ammonium bromide

Examples of Ions in Water

• Chloride• Nitrate• Phosphate• Mercury ion• Calcium• Sodium• Magnesium

• What are the charges on these ions?

Hard Water is caused by ions…

A pipe with hard-water scale build up

Hard water contains high concentrations of dissolved calcium and magnesium ions.

Soft water contains few of these dissolved ions.

Because calcium ions, Ca2+, are generally the largest contributors to hard water, hardness is usually expressed in parts per million of calcium carbonate (CaCO3 ) by mass.

It specifies the mass of solid CaCO3 that could be formed from the Ca2+ in solution, provided sufficient CO3

2- ions were also present:

Ca2+(aq) + CO32–(aq) → CaCO3 (s)

A hardness of 10 ppm indicates that 10 mg of CaCO3 could be formed from the Ca2+ ions present in 1 L of water.

5.8

Simple generalizations about ionic compounds allow us to predict their water solubility.

IonsSolubility of Compounds

Solubility Exceptions Examples

sodium, potassium, and ammonium

All soluble None NaNO3 is solubleKBr is soluble

nitrates All soluble None LiNO3 is solubleMg(NO3 )2 is soluble

chlorides Most soluble Silver, some mercury, and lead chlorides

MgCl2 is solublePbCl2 is insoluble

sulfates Most soluble Strontium, barium, and lead sulfate

K2 SO4 is solubleBaSO4 is insoluble

carbonates Mostly insoluble* Group IA and NH41

carbonates are solubleNa2 CO3 is soluble CaCO3 is insoluble

hydroxides and sulfides

Mostly insoluble* Group IA and NH41

hydroxides and sulfides are soluble

KOH is soluble Al(OH)3 is insoluble

*Insoluble means that the compounds have extremely low solubility in water (less than 0.01 M). All ionic compounds have at least a very small solubility in water.

Not all ionic compounds dissociate in water.

5.9

What happens to covalent molecules in solution?

A sucrose molecule – when dissolved in water, sugar molecules interact with and become surrounded by water molecules, but the sucrose molecules do not dissociate like ionic compounds do; covalent molecules remain intact when dissolved in solution.

They will not conduct electricity; they are non-electrolytes.

Like dissolves like

5.9

Non polar solvents dissolve non polar compoundsPolar solvents dissolve polar compoundsWater dissolves polar compounds and compounds that can hydrogen bond

Today: April 16• Chapter 5: The Water We Drink

– Drinking Water and Water Treatment– Water Quality Issues in MN and World

For Next Time: Tues, April 21• Guest Lecturer: Laura Triplett, Geology• Lab: Read Lab 15 from Manual and Handouts• Finish Reading Chapter 5• Start Chapter 5 Homework (Due 28)• Next Paper Due April 30th

Drinking Water and Water Treatment

Drinking Water Contaminants

Biologicals are also monitored, especially Cryptosporidium and Giardia

Drinking Water Treatment

Al2 (SO4 )3 and Ca(OH)2

Disinfection• Chlorination

– HClO kills bacteria in the water– Problems: People don’t like taste of chlorine residuals

and disinfection by-products form, need to add lots of chlorine so water stays clean to the tap

– Used almost exclusively in US• Ozone

– Ozone kills bacteria in the water; is more effective than chlorine

– Expensive – Used in Europe

• UV Radiation– UVB used to kill bacteria– No by-products

Water Quality

Density of Water

Density

Degrees Centigrade40

Ice

Heaviest water at 4o CHeavier

Lighter

Temperature Profiles in Lakes

Fall Winter Spring

•T profiles created due to density differences in water•Warmer water sits on top of cooler water in the summer•In the fall, warmer upper water cools and mixes with lower water•In winter ice and colder water are at the top, heavy 4oC water at bottom•How could global warming impact lake mixing?

Summer

Thermal Stratification in Lakes

Epilimnion

Hypolimnion

Thermocline

•Summer stratification•Lighter, warmer water in the epilimnion sits on top of heavier, colder water in hypolimnion•Thermocline - transition zone where water T changes• Epilimnion and hypolimnion mix very little in strongly stratified lakes

Eutrophication• A eutrophic lake has high levels of algae

– green algae scums• Some lakes are naturally eutrophic

– shallow lakes with large watersheds– typical of lakes in S and SW Minnesota

• Many lakes are more eutrophic than natural due to increased nutrient loading

(usually P) related to watershed disturbances

• Arguably the most serious water quality problem in MN

Experimental Lakes Area - Lake 226 Phosphorus and Algae Growth

Phosphorus added to one side of the lake

ELA Lake 227 in 1994

http://www.umanitoba.ca/institutes/fisheries/eutro.html

What Happens in a Eutrophic Lake?

•Phosphate addition lead to excess algae growth •photosynthesis produces oxygen; only occurs during daylight

•Bacteria are constantly decomposing algae (removes oxygen)•Algae die and settle to hypolimnion•no photosynthesis in hypolimnion; thus O2 levels decline•fish communities change

Relating to lab…

We’ll be measuring the concentrations of several nutrients and other chemicals in our water samples…

• Phosphate concentrations • Nitrate concentrations• Chlorine concentrations

Restoring Eutrophic Lakes• Reduce external loadings of nutrients

– restore wetlands or add artificial wetlands– buffer strips or sedimentation basins to trap

runoff– prevent septic systems from leaking– do not use P-containing fertilizers in the

watershed– do not allow yard waste to enter lake via sewers

• Control internal recycling of nutrients– cap sediments– add alum– difficult and expensive

Carlson Trophic Status Scale

Oligotrophic vs Eutrophic

Lake Shaokatan

• West Central MN (Lincoln County)• 1018 acres, mean depth 7.3 feet (8:1 ratio

of agricultural watershed to lake)• Severe degradation in 1980’s, massive

algal blooms with toxic blue-green algae episodes

• Diagnostic study 1989, rehabilitation began in 1991.

Lake Shaokatan

• Pre-rehabilitation TP 200- 350 ug/L, Chl-a averaged 50-150 ug/L, Secchi – 1-5 ft

• Post-rehabilitation TP 89 - 161, Chl-a 6 to 66 ug/L. Summer Secchi’s peaked at 6.8 feet.

• WQ parameters decline: watershed problems noted (old feedlot enriched area, new inlets during intense rain events). TP(2001)= 189ppb.

Lake Shaokatan

Management in an Agricultural Watershed

• Short Term Goals• Inlake

TP < 150 ug/L Chla

< 60 ug /L• Reduce Severe

Nuisance conditions

• Long Term Goals• Inlake

TP 90 ug /L Inlake

Chla

< 30

Phosphorus Export Coefficients. Estimated ranges from literaure and measured ranges from subwatersheds in Lake Shaokatan CWP Project

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Fores

t

Precip

Grass

Shaok C

RP

Urban

Cultiva

tedSha

ok Cult.

Shaok F

eedlot

Land use

Kg

P/ha

/yr (

~lb/

acre

/yr)

Feedlot alone 1,000 kg

Lake Shaokatan Mean Total Phosphorus

0

100200

300400

500

1989199019911992199319941995199619971998199920002001

PPB

Pho

spho

rus

Abandoned feedlot and lagoon, south of lake

Manure was placed in wetland adjacent to lagoon also. This drains to Shaokatan during storm events.

Secchi disk depth about 0.5 m

Links on the Web

• PCA web site: www.pca.state.mn.us/water/

• Minneapolis lakes: www.minneapolisparks.org

– click on “Water Resources” at left• Minnesota Waters :

http://www.minnesotawaters.org/• Lake Hallett Association:

http://www.lakehallett.com/

Mercury - Hg• Exists in many forms (elemental Hgo, ionic

Hg+2, and organic - mainly methylmercury)– Methylmercury is formed in lake sediments

and wetlands and is the only form that accumulates in fish, loons, marine mammals, etc.

• What are some uses of mercury? Risks?

Mercury - Hg

• Many uses– fluorescent lights– production of chlorine– fungicide in paints, wood, vaccines– detonators– light switches– thermometers and barometers– Dental amalgam, gold mining, others

• Occurs naturally in the earth’s crust– coal contains trace amounts of mercury– burning of coal is the largest source

Mercury in the NewsChemical and Engineering News, April 13, 2009 Volume 87, Number 15, p. 33Army Halts Mustard Destruction In UtahRochelle F. H. Bohaty

Destruction of mustard-agent-filled mortars at the Tooele Chemical Agent Disposal Facility, in Utah, was stopped last week when higher than expected levels of mercury where measured in emissions. Although the mercury emissions were within permitted limits, the Army said in a statement that it is "committed to ensuring maximum protection of the environment" and has delayed further processing of the mortars. The recent campaign to destroy mustard agent in the 4.2-inch cartridges began on April 1. The Army plans to resume processing these mortars once a new sulfur-impregnated charcoal emission filter system designed to capture mercury from furnace flue gases has been installed and tested. Currently, the Tooele facility has destroyed more than 50% of its mustard stockpile. According to Army estimates, the depot has neutralized 78% of its total stockpile of chemical weapons agents. The Army plans to complete neutralization of all chemical weapons, including Tabun nerve agent and Lewisite blister agent, remaining at the Tooele depot by fall 2011.

Elemental Mercury

• Hgo – Silvery metallic liquid• Volatilizes readily• Virtually insoluble in water

(implications?)• Does not attach to particles

(implications?)• Many sources emit Hgo

• Vapor form can be inhaled or it can pass through skin and into bloodstream

• Liquid form does not pass through stomach lining

• Acute and chronic exposure risks

Ionic or charged Hg

• Hgo --> Hg+2 (oxidation)• Oxidation occurs in atmosphere (also soils

or water)• Very “sticky” – sticks to particles and

surfaces• May be inhaled, passes through stomach

lining• Least harmful form

Methylmercury (MeHg)

• Hg+2 --> (H3 CHg)+ (methylation)– MeHg formation is why we have a Hg problem

• Formed mainly microbially (by sulfate-reducing bacteria) in anoxic environments (wetlands and lake sediments)

• Lakes with low pH and high DOC tend to have higher MeHg levels

• Low pH favors methylation and MeHg is more stable

• MeHg photodegrades (light converts it to Hgo)• MeHg enters through lungs, skin, and stomach

How Does Hg Get Into Fish?

Runoff

WetlandTransport

AtmosphericDeposition

Wetlands and Sediments:

WaterPhytoplankton

ZooplanktonPrey Fish

PredatorFish

Elemental Mercury (Hg0): dominant species in atmosphere (99%), many sourcesIonic Hg (Hg2+): dominant species in rainfall, water, sediments, soilMethylmercury (MeHg): dominant species in fish, loons, produced microbially

Hg2+Hg0

Hg2+ MeHg

Length and structure offood chain is important

Health Effects• Humans

– Main health risk is from eating fish (MeHg), but also risk from breathing elemental Hg

– Effects: Headache, Memory loss, Hearing loss, Visual problems (e.g. blurred vision, blindness), Slurred speech, Impaired muscular coordination, Muscle spasms, Loss of sensation in fingers and toes, Numbness around mouth, Reproductive problems, Paralysis, Coma, Death

• In children whose mothers consumed mercury during pregnancy:– Mental retardation, Loss of coordination, Visual

problems, Cerebral palsy

Concern over Mercury: NHANES

• Center for Disease Control NHANES study– 10% of women of child-bearing age have

mercury (methyl Hg) levels that are close to levels of concern

– translates to 400,000 children born each year that may be impacted

• affects brain development• evidence for cardiovascular impacts• subtle effects

– Most exposure is from eating fish

Case Study - Minimata

Minimata Disaster• Chisso Co. - used Hg as a catalyst to produce

acetaldehyde• 1932 began dumping Hg waste in Minimata Bay• 1950’s: dead fish, birds, cats

– people began having symptoms of Hg poisoning• 1956: Researcher linked Chisso discharge to Hg

poisoning– company discontinued funding and destroyed

results• 1968: Hg discharges discontinued

– Hg as catalyst process became obsolete

Minimata Disaster (cont’d)

• Over 100 people died• 12,615 officially recognized as victims

– many offspring severely retarded• originally $130k given to a few victims

– millions have been given since• lawsuits still pending• Fish concentrations were at least 20 ppm

Hg– Some MN fish are at 4 ppm Hg– Minimata victims ate a lot of fish

Where Does the Hg in MN Come From?

-Most Hg (~90%) comes from out of state

Sources in Minnesota:• Energy Production -

Coal Burning- 47%• Purposeful Uses -

30% (waste combustion, processing)

• Taconite processing and other - 23%

3700 lbs emitted in 2000 (estimate); 8500 lbs in 1990; ~5700 lbs deposited

Global Emissions

Regional Emissions

Local Emissions

MeHg Fish

MercuryConversions

How Does Hg Get Into Fish?

Runoff

WetlandTransport

AtmosphericDeposition

Wetlands and Sediments:

WaterPhytoplankton

ZooplanktonPrey Fish

PredatorFish

Elemental Mercury (Hg0): dominant species in atmosphere (99%), many sourcesIonic Hg (Hg2+): dominant species in rainfall, water, sediments, soilMethylmercury (MeHg): dominant species in fish, loons, produced microbially

Hg2+Hg0

Hg2+ MeHg

Length and structure offood chain is important

40 50 60 70 800.2

0.4

0.60.8

2

40 45 50 55 60 65 70 75 800.0

0.5

1.0

1.5

2.0

Hg μg

/g

Fish Length, cm

Sand Point 69-617 Northern Pike, 1997

Fish Length, cm

Hg μg

/g

N. Central Hardwood ForestDriftless Area

Northern Glaciated PlainsNorthern Lakes and ForestsNorthern Minnesota WetlandsRed River ValleyWestern Cornbelt Plains

##

#0.0 -

0.2#NP Hg μg/g

0.2 -

0.4

0.4 -

0.60.6 -

0.8> 0.8

Statewide Hg in Standard-Size NP μg/g

WaterPhytoplankton

Zooplankton

Prey Fish

PredatorFish

Deposition

Air

Water

Release or resuspension of sediment

Longer food chains = more bioaccumulation

Simplified Bioaccumulation

Food In Food Out

Contaminant In Contaminant Out

Why do biota accumulate contaminants?

Biota accumulate contaminants over time

Why are fish mercury levels so variable in MN?

• Some lakes are more efficient at forming methylmercury

• MeHg is more persistent in some lakes• Some lakes have more wetlands in their

watershed• Length and structure of the food chain is

different in many lakes• Some lakes receive more loading of Hg

from their watersheds

Today: April 21

For Next Time: Thurs, April 23

• Guest Lecturer: Laura Triplett, Geology• Newspaper Articles: Danielle and Mike• Lab Discussion: Lab 15 from Manual and

Handouts• Start Chapter 6 Notes

• Finish Chapter 5 Homework, Due April 28• Read Chapter 6

Lab Notes

• Phosphate Determination: UV-Vis spectroscopy with Ocean Optics/Vernier Software

• Nitrate Determination: Ion Specific Probe and Vernier Software

• Chloride Determination: Monitor Color Changes with Titration

• Ion Chromatography: All ions will be determined by junior chemistry major on ion chromatograph

Spectroscopy

Calibration Curve

Ion Chromatograph

Acid Rain: Chapter 6

Notes will be added later