IRC Environmental Chemistry Aug 18, 1998

Pub #brownchem: @alpha137

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alpha137: hello

*** lizzk (gloworm4@173-98-173.ipt.aol.com) has joined channel #brownchem

lizzk: Hello, oh, I guess I changed my nick in an attempt to get back on last week

alpha137: hello

alpha137: How are things?

lizzk: The phones seem to be working better- but we are going to have to have the whole house re-wired

lizzk: Other than that things are good

alpha137: Why?

alpha137: I thought phone lines were pretty simple-and long lasting.

lizzk: Because there are shorts all over the place- in two or three different extensions- but inside the wall so it can't be fixed.

lizzk: These were long lasting- they've been in the house for 40 years

alpha137: Must have been the mice working on the wire insulation all this time?

lizzk: perhaps

alpha137: Any way, back to water.

lizzk: ok

alpha137: I was looking at my copy of the text (older edition) and at the distribution of uses in the US

lizzk: ok

lizzk: I have the place

alpha137: You have any comments on the fact that 57% is industrial, 34% agricultural and 9% domestic?

lizzk: thats a lot of industrial and agricultural use.

lizzk: I was very surprised it was so much

lizzk: And then- if we are running out of water- why chan't they cut down on their use?

lizzk: chan't => can't

alpha137: I makes cutting water used by flushing toilets seem trivial.

lizzk: Exactly

lizzk: IN times of drought, do the industrial and agricultural users cut down on their use of water?

alpha137: The industrial use IS our economy so I doubt it.

lizzk: That's too bad

alpha137: A lot of that use should be in the columns of other countries since we export!

lizzk: Thats true.

lizzk: BUt I would bet that the avg american uses more water than people in many other countries

alpha137: The per capita use is the total water use per person including industry and ag. No wonder we have the largest per capita use in the world - we are the largest economy.

lizzk: Yes

alpha137: I think it is hard to tell what our real use is.

lizzk: True

lizzk: Especially since it will vary greatly by region, and probably within seasons

alpha137: I tool a sabbatical to Colorado and lived on a ranch in the rockies in an Airstream trailer.

lizzk: Wow

lizzk: I love the mountains

alpha137: That trailer had a 50 gal water tank and we were a family of two to three

alpha137: Two to three because there was a dog and a small child.

lizzk: I see, but you don't really need to wash a dog like you do a person

alpha137: 50 gal of water per day was not enough, and we were conservation minded..

alpha137: We did not wash the dog!

lizzk: I can imagine

alpha137: We hooked up to a stream of pure rocky mountain water-straight from the mountains.

lizzk: I did't think that the dog would be a high priority on a 50 gallon a day limit (it isn;t even one on my unlimited supply)

lizzk: Did you have to clean it

alpha137: We had plenty of pure, unadulterated water and it was great.

lizzk: wow

lizzk: that mush have been nice

lizzk: mush is must

alpha137: The thing that impressed me was how much water we use and that with great conservation 50 gal/three people is difficult. At least if you bathe.

lizzk: Yes, I think bathing probably takes the most water

alpha137: I do not think one can get by on 25 gal/person per day.

lizzk: But how did you manage then?

alpha137: We hitched up to the mountain streams as I said.

lizzk: Ok

alpha137: In the text Marin Co. Ca is mentioned. You read that?

lizzk: Yes

alpha137: That is where I grew up.

lizzk: oh, so you have some first hand knowledge of what they're talking about

alpha137: Yes, and my sister and brother-in-law live there and were in that drought.

lizzk: thats too bad

lizzk: about the drought i mean

alpha137: According to the text, people there were allowed 50 gal/person per day.

lizzk: Thats not very much

alpha137: It is a lot more than my Airstream!

lizzk: but it is double what you had in Colorado- do you think that would be feaseable

alpha137: In Marin, during that drought, there was no outside watering.

alpha137: All the lawns died.

lizzk: I would imagine not

lizzk: I menat about the outside watering

lizzk: menat -> meant

lizzk: And I would assume the lawns would die given the conditions

alpha137: When the drought was over and people began watering those "dead" lawns they sprung back to life!

lizzk: Thats good

alpha137: I am thinking that per person we need somewhere between 25 gal and 50 gal per day minimum.

lizzk: ok

alpha137: The text says 71 gal/day/person on the average.

lizzk: but that doesn't include things like watering the lawn

alpha137: The 71 gal probably includes watering the lawn.

lizzk: Ok and that explains why it is more- iwrote that about the 50 gal per day minimum

lizzk: I wrote the lawn comment

alpha137: This gives us an idea of what we really need for domestic use.

lizzk: yes

alpha137: In Marin, and perhaps where you live too, there is not so much industrial activity.

lizzk: not much - lotsa politics though

alpha137: Especially, today!

lizzk: yep!

lizzk: ITs all over the place

alpha137: So, it would appear that if you have heavy industry you need to site the plant near an adequate supply of water.

lizzk: Yes

alpha137: What are the sources of water??

alpha137: You know, where does it come from?

lizzk: lakes rivers, oceans, groundwater, rain and precip. but not much

lizzk: I was typing and answer- i did understand the question

alpha137: The ocean has lots of salty water!

lizzk: I guess you could count glaciers or icebergs too (but they are melting fast)

alpha137: Aquifers?

lizzk: Yes, but maybe someday the industry's will be able to use salt water

lizzk: I read an article about salt-water agriculture irrigation rather, it said it was a viable possiblily since there is not too much freshwater left

alpha137: How does one get the salt out of sea water?

alpha137: Give me a couple of ways.

lizzk: Purify it- distill it or reverse osmosis,

lizzk: or just oldfasioned boil it and use the condensation

lizzk: But I think that is distilling it

alpha137: Thanks, and right.

alpha137: Boil = distill.

alpha137: How does reserse osmosis work?

alpha137: reverse

alpha137: There are a bunch of important chemical principles here.

alpha137: How do human cell walls allow potassium and sodium ions to pass?

lizzk: they put pure water and salt water on two sides of a membrane- in reg osmosis the salt would spread to the pure water, but with the help of a big pump they salt water is separated and the water part of the salt water goes to the fresh water chamber

lizzk: The second they was supposed to be a the

alpha137: The high pressure supplied by the big pump overcomes the normal chemical tendency.

lizzk: exactly

alpha137: Have you ever seen an osmotic pressure experiment?

lizzk: not yet

alpha137: This is where we need the lab part of this couse.

lizzk: yeah

alpha137: I have on top of my computer a semipermeable membrane. If I put that over a tube containing water and dump the membrane covered end into a concentrated sugar solution what do you think will happen?

lizzk: The sugar will go into the water part to establish some sort of equilibrium

lizzk: So both sides of the membrane are equally concentrated

alpha137: No, on one side we have pure water and on the other concentrated solution of something in water. The pure water part of the tube is extending upward.

alpha137: What happens?

alpha137: Woops, right. I just read your answer!

lizzk: even if the water is up?

alpha137: I am after a picture of that column of water before and then after when equilibrium has been established. What does it look like; what happens?

lizzk: before it would be two distinct liquids, after it would be one liquid throughout but different from either of the first

alpha137: Right, but I was after what happens to the length of the column of water in the tube.

lizzk: i don't know- it gets shorter?

alpha137: Correct, it gets shorter because some of that water went to making the solution more dilute.

alpha137: A column of water of a certain diameter weighs a certain amount. Right?

lizzk: yes

alpha137: It provides a force per unit area (force of gravity due to the mass of water).

lizzk: yes

alpha137: A force per unit area is a ___?

lizzk: pressure

alpha137: Right.

alpha137: This is osmotic pressure!

lizzk: oh, i see

alpha137: If we have a human cell and we surround it with a salt solution what do you think happens?

lizzk: The cell will absorb some salt

lizzk: Won't it try to equalize the salt content and then shrivel up and die?

lizzk: I mean, if the salt is too concentrated

alpha137: Yes, that is the answer. Water inside the cell will pass through the membrane in an attempt to lower the salt concentration outside.

alpha137: The cell will shrivel up.

alpha137: Usually, these questions are posed in the opposite way. The sugar solution is in the tube, for example. The cell is surrounded with water, not salt solution.

alpha137: The reverse answers apply when the problem is pose in this way.

alpha137: The chemical force is the Gibbs Free Energy.

lizzk: If the cell is surrounded with water then it will explode?

alpha137: Yes, the cell will explode.

lizzk: ok

alpha137: If some stupid person were to inject water into the blood supply then cells would explode.

lizzk: That would not be good

alpha137: That is why saline solution is used with humans. Saline means the correct ionic content.

lizzk: ok, i see

alpha137: We are talking paths towards equilibrium here.

lizzk: ok

alpha137: The controling quantity is the Gibbs Free Energy.

lizzk: i see

alpha137: To understand the macroscopic details we need to understand this Gibbs Free Energy busines.s

lizzk: ok

alpha137: We have discussed it earlier.

lizzk: yes

lizzk: I remember

alpha137: At equilibrium the Gibbs Free Energy change is zero.

lizzk: yes

alpha137: On one side or the other it is either positive or negative.

lizzk: yes

lizzk: so they balance each other out

alpha137: The way in which we would speak of this reverse osmosis thing is in these terms. At equilibrium there is some osmotic pressure which results in a zero G. If we apply a pressure in the right way we make the change in G negative towards the

alpha137: forcing of water through the membrane. That kind of thing.

lizzk: ok

alpha137: The motivation for learning this Gibbs stuff is to be able to deal quantitatively (and qualitatively too) with the approach to equilibrium in chemical system.s

lizzk: ok

lizzk: i understand

alpha137: In anycase, we have these broad connections between purifying water for domestic use and the lysing of cells in a biological system! Neat, huh.

lizzk: yep thats pretty neat

alpha137: Regardless of the massive uses of water in industry, we have to have pure water for life.

lizzk: yes

lizzk: and thats more important too! Without life there can be no industry

alpha137: That means we need a pure water source for that 50-71 gal per person per day.

A link to discn below about one method of determining organic impurities in water

alpha137: There is other life we need too.

lizzk: true

lizzk: yes

alpha137: Trees?

lizzk: yes, everything

alpha137: Fish in lakes and streams?

alpha137: This is a kind of transition to the topic of acid rain.

Here is an EPA link to acid rain.

Here is a link to acid rain in Europe.

lizzk: Of course- I don;t think that we as a species know enough about how EVERYTHING is related to think that we don'[t need any species

lizzk: But thats just me

lizzk: I also read the chapter on Acid Rain

lizzk: Except the more correct term is acid deposition

lizzk: But Acid Rain sounds better

alpha137: Yes, lets use the term acid deposition. The rain water is acid however.

lizzk: true

alpha137: We can define Acid Rain = Acid Deposition and use these terms interchangibly.

lizzk: Thats fine with me

lizzk: I probably would have done it anyway

alpha137: A friend of mine ran an environmental company. He sent his chem engineers out to measure the pH of water at a house. They came back with the result that the pH = 1. Comment on this please.

lizzk: HOw could it be that low!! That would be like washing your hands with lemon juice except worse!

lizzk: I hope they made a mistake

lizzk: That is horrible

alpha137: Well, there you are. You are smarter than a couple of graduate chemical engineers! Obviously the made a mistake.

alpha137: Their boss thought so too.

lizzk: ok, thats good

alpha137: They must have rinsed their pH probe with an acid solution.

alpha137: What would be the concentration of the acid in that pH = 1 solution?

lizzk: Something weird must have happened

alpha137: In moles/liter that is.

lizzk: wouldn't that be a 1 molar solution?

alpha137: No.

lizzk: or .1 maybe

alpha137: Yes

alpha137: pH = Log[H^+]

lizzk: ok

lizzk: I remember now

alpha137: -Log(0.1) = 1

alpha137: pH = - Log[H^+] I missed the minus sign.

lizzk: I thought there was a minus sign missing

alpha137: This is defined as a log scale because the range of useful concentrations is so large. Logs are convenient.

lizzk: yes

alpha137: We have established that you understand the acid/base part of the Acid Rain book stuff. What is the cause of acid rain?

lizzk: It can be formed when various compounds like NO_x and SO_x are released into the atomosphere, they bond with water forming acidic soloutions.

lizzk: When the rain falls, it is as an acid

alpha137: Right.

alpha137: There is a complex chemistry up there as well.

alpha137: Up there means a few thousand feet.

lizzk: yes,

lizzk: This all takes place in the troposphere, yes?

alpha137: Yes, the troposphere.

lizzk: ok good

alpha137: There is a lot of chemistry up there.

lizzk: yes,

lizzk: but there is chemistry everywhere

alpha137: Sulfur dioxide, SO_2, is oxidized to sulfur trioxide, SO_3.

lizzk: yes

alpha137: It is true that there is chemistry everywhere. I guess that is one of the reasons I enjoy the subject.

lizzk: yes,

lizzk: and everything is interrelated

lizzk: thats what I like

alpha137: I went hiking in the White Mountains in NH more than 10 years ago and then went back 10 years later. What I saw was a tremendous change in the forest.

alpha137: The forest was under attack from something.

lizzk: Let me guess, acid Rain?

alpha137: It certainly could have been acid rain!

alpha137: It looked real to me. How do we get rid of it?

lizzk: or perhaps it was just weakened by the rain and then some bug or tree blight came through and killed the rest

alpha137: Your last statement is the real problem in all this. How do we know this attack on the forest was acid rain and not some pest?

lizzk: I was thinking about that- it isn't like we can pour limestone on the entire earth to stop it

lizzk: I don't think we do, but there is some pretty substatial evidence that Acid Rain has had some effect

alpha137: Yes, it is impractical to cover vast land areas with limestone.

lizzk: ITs sort of like trying to fly some ozone up to the stratosphere to fix the hole

alpha137: Forest scientists have to go out and examine the trees and their surroundings to determine if pest are the cause.

lizzk: yes, but wasn't there something in the book about how the Acid Rain could weaken a forest so a pest could come in and finish it off?

alpha137: In fact, many measurements are being made of acid deposition and soil pH, etc in the forests. There are many mysteries as I understand it.

lizzk: So then it appears as though acid Rain had nothing to do with it, when in fact it did

alpha137: Yes, acid rain could weaken the forest so that pests could take hold.

lizzk: well. it is not a clear cut subject

alpha137: This sounds like all the subjects in not being clear cut.

alpha137: Global warming is not clear cut either.

lizzk: Yes, but I think that some of the others were more clearly defined

lizzk: And Global Warming is pretty much sure to exist

alpha137: The situation seems to be that we have good evidence that acid rain is messing up Eastern lakes and forests.

lizzk: Ok, so we know it exists

alpha137: Likewise, as you say, we have good evidence that global warming exists.

alpha137: Therefore, it behooves us to do something.

alpha137: What?

lizzk: Well, it seems to me that there are these huge industrial places spewing both CO_2 and SO_x into the atomosphere, and there aare lots of cars being driven giving of CO_2 and NO_x as well

lizzk: These affect both GW and Acid Rain

lizzk: So if we could cut back that would be better

lizzk: But how to do that?

lizzk: Laws? New Tech? Conservation? MY guess is a combination of all of them,

alpha137: Surely, it requires federal regulations to make the impacts fair to all.

lizzk: Yes, and that requires people who care about the issue

lizzk: or rather issues

alpha137: Regulations and federal programs can encourage conservation.

lizzk: Yes, especially if there are incentive

lizzk: s

alpha137: The environmental interest of the

lizzk: and they can also encourage people to develop new technology

alpha137: American public has been long standing.

lizzk: YEs

lizzk: And the situation has improved

lizzk: some

alpha137: There are public interest groups like the health associations.

lizzk: Yes, I think people care a lot about their health, if these were somehow to relate to pub. health issues then thinkgs would start to happen- just look at smoking

alpha137: And environmental orginzations like the Sierra Club, and Friends of the Earth, and EDF (Environmental Defence Fund), Fesources for the Future, etc.

lizzk: yes

alpha137: These organizations represent a lot of folks.

lizzk: that is good

lizzk: but the movement for change has to be huge given the opposition- time and the big industry companies (ie a major portion of the economy)

alpha137: Politicians understand the importance of these public associations.

lizzk: yes

lizzk: They also understand lobyists and the pwr of money

lizzk: but in truth, I do think things will happen

alpha137: To take one I know a little about, the American Lung Association, there are offices in every state.

lizzk: yes

alpha137: It is a large grass roots outfit and its representatives, citizens, talk to their local politicians-state and national.

lizzk: yes, that is how it has to work -

alpha137: They do not have much money, but they do swing a lot of votes!

lizzk: The people have to care before the politicians do

lizzk: YEs

alpha137: Now you add the Heart Association (3 times the size of Lung) and the Cancer Association and you are beginning to talk about a lot of votes!

lizzk: Yes, I agree completely

lizzk: But Will the Lung, heart, and Cancer associations fight for enviro. reforms?

alpha137: This is not a trivial thing here.

lizzk: No it is huge

alpha137: Yes, Lung, Heart and Cancer will fight for environmental reforms that impact the diseases of their consitutents.

alpha137: Air pollution is easy for them.

lizzk: So first you need good evidence that these problems do affect the health, air pollution is probably the one with the most evidence

alpha137: Getting pure water, water without carcinogens, is easy for Cancer.

lizzk: Thats true

alpha137: Yes, we need scientific evidence.

lizzk: Which goes back to why scientists can't lie

alpha137: Right. To lie is to really remove your effectiveness.

lizzk: Yes,

lizzk: And then on top of the american health associations, there are the environmental ones, maybe they have a little image problem, but that can be remidied

lizzk: remedied?

lizzk: And if America leads the way, maybe the rest of the world will follow'

alpha137: I have a question for you to think about. We have a vial of water containing some organic impurity (that gas station with a leaking tank into the water supply). The vial is closed with an air space above the water.

lizzk: ok

alpha137: What is contained within the air space above the water?

lizzk: well, won't there be some of that impurity too?

alpha137: Yes.

alpha137: What is the relationship between the amount of that organic impurity and the concentration of the impurity in the water?

lizzk: The more of the impurity, the higher the concentration?

alpha137: If we know this then we can devise a test for determing the purity of the water.

lizzk: yes

alpha137: Yes, generally the more the impurity in the water the greater the impurity in the vapor above the water.

alpha137: What is that relationship?

lizzk: a direct one?

alpha137: What would the funcational relationship be? Direct = what?

lizzk: as one increases so does the other?

lizzk: What do you mean functional relationship?

alpha137: Linear, exponential?

lizzk: oh, linear probably

alpha137: Yes.

alpha137: This is a question I meant to ask before our acid rain stuff.

lizzk: ok

alpha137: The linear relationship between partial pressure of organic vapor and concentration in water is called Henry's Law.

lizzk: ok

alpha137: p = k_H * (mole fraction of volitile impurity), where k_H is called the Henry's law constant.

lizzk: ok

alpha137: If we go around those gas stations, dig down and get a sample of soil and put it into a vial with some water then cap it we can measure the concentration of the contamination.

lizzk: yes

alpha137: Cap the vial, let it come to equilibrium for 10 minutes or so and measure the pressure of the organic vapor. Then using k_H we compute the mole fraction of the impurity.

lizzk: ok

alpha137: We have nailed that service station!

lizzk: i see

alpha137: To measure the vapor pressure we have to have some equipment.

lizzk: yes

alpha137: A portable gas chromatograph does the trick.

lizzk: ok

alpha137: The vial has a plastic septum in the cap. A syringe is pushed through and 100 microliters of vapor is extracted.

lizzk: ok

alpha137: This 100 microliters of vapor, containing air, organic impurity, etc., is placed into the imput of a gas chromatograph.

lizzk: ok

alpha137: The gas chromatograph must be calibrated.

lizzk: yes

alpha137: The signal of the organic impurity is displayed along with the concentration in the vapor (usually in ppm or ppb).

lizzk: ok

alpha137: Now, do you know what a gas chromatograph is?

alpha137: How it works?

lizzk: no

alpha137: There is a small plastic tube filled with a substrate (something inert) and the surface of the substrate is covered with a polymer.

lizzk: ok

alpha137: This tube has the end leading to some kind of detector of organic material and the input is closed. Also, there is some intern gas acting to push the impurity through the tube.

lizzk: ok

alpha137: The 100 microliters is injected into this tube and the inert gas, flowing at some rate, pushes the impurity through the substrate covered with polymer.

lizzk: ok

alpha137: The impurity (the organic compound) dissolves in the polymer, but is pushed along disolving and vaporizing as it goes.

lizzk: ok

alpha137: The "sticking" rate of the organic vapor depends on the specific compound.

lizzk: i see

alpha137: That is, the organic compound's ability to dissolve in the polymer depends on the particular molecular weight and structure.

lizzk: ok

alpha137: This is the way in which the chromatographic column can separate the different compounds. This can then be used, with a detector, to determine which compounds are present.

alpha137: We can take a portable apparatus like this and test water supplies.

lizzk: i see\

alpha137: Originally, plant colors were seperated in this fashion. Hence the name chromtography.

lizzk: ok

alpha137: In that case, the plant colors were in water solution and the colume was silica in a glass tube.

lizzk: ok

alpha137: Gravity did the pushing.

lizzk: ok

alpha137: The plant colors seperated in bands.

lizzk: yes

alpha137: You never saw that?

lizzk: no, i saw the plant color one

alpha137: OK, you saw the plant color one. The principle is the same and we can use

alpha137: this with organic vapors.

lizzk: ok

alpha137: This is one method for checking the purity of our water supply in terms of orgnics.

return to discussion of acid rain

lizzk: ok

lizzk: \

alpha137: I need to stop. It seems that in all these cases it is cheaper to clean up the source rather than the end point of the pollution.

lizzk: I think so too,