Class Notes (839,147)
United States (325,796)
Chemistry (865)
CHEM H90 (28)
Burke (28)
Lecture 16

CHEM H90 Lecture 16: The Ozone Hole and the Man Who Saved the Planet, pt.2 (05/10/17)
Premium

5 Pages
69 Views

Department
Chemistry
Course Code
CHEM H90
Professor
Burke

This preview shows pages 1 and half of page 2. Sign up to view the full 5 pages of the document.
Description
LECTURE 16 Wednesday, May 10, 2017 Atmospheric Chemistry: Ozone Hole The Ozone Hole and the Man Who Saved the Planet (pt.2) Ozone and Cl• • Data from Susan Soloman’s 1987 flight into the Antarctic ozone hole o This would have been flying over the ocean, very little chlorine in the air o As you approach a certain degrees latitude, the stratospheric chlorine goes up and stratospheric ozone goes down ▪ Shows very clearly that when there’s more chlorine, there’s less ozone Why Antarctica? • Coldest spot on the planet (-90 C) • Good stratospheric circulation due to land mass • Get polar stratospheric clouds with tiny ice crystals in winter o Makes all sorts of chemistry happen o Once you have these little, little particles, you can catalyze a reaction • Reactions on ice surfaces make reactive species for ozone depletion • Chlorine is released in Antarctic spring Antarctic ozone readings • This is the full curve of the British Antarctic readings, from 1980 o A sudden drop, from about 200 to below 100 since 1990 • Is there a misleading impression created by the choice of scale on the y-axis? o Yes, because it doesn’t start from 0. ▪ They want to emphasize their point, this huge drop • Antarctica didn’t have that much ozone to begin with, and half of that vanished o Human processes can affect the planet Largest ever Antarctic O3hole • Ozone depletion, the ozone hole, is the area on the surface of the earth where ozone is seriously missing Changing size of O3hole • A function of month • As you go from August to December, you see the ozone hole appear and disappear Global Response • We have the scientific paper in 1974… how did the world respond? Industry’s response • Let’s find a way to not worry about the problem • They don’t really want to know because it’s not good for business CFC production • Thirteen years later, 1987, the Montreal Protocol was signed • In the mid 1970s, energy crisis occurred o Lots of our chemicals come from cracking oil o CFC production leveled off • In 1987, the whole world signs a treaty saying they’ll stop producing CFC o CFC production goes way down Halons • Replace CFC with halons • Which element might be substituted in CFC’s to try to make them less harmful, but still have the same unreactive chemistry (so can be used for the same purposes)? o Cl replaced by Br ▪ Logic: it’s heavier, so it won’t get to the stratosphere Other replacements • Halons (using Br) are heavier, so go less high, but even more destructive to 3 • Hydro-CFCs (HCFCs) at first, such as CHClF2and C 2 3l 2 o Replace one Cl with a H or replace with a metal group (CH )3 • Much less destructive, but now being phased out • Now we have HFC’s (no chlorine – chlorine is the thing that eats up ozone), such as C 2F 5nd CH F 2 2.e., no Cl. • A lot more reactive, so they don’t make it to the stratosphere o The reason those CFCs were getting up there was because they don’t react to anything. If you’re more reactive, you don’t get up there Modern dust-off can • “No CFCs” o No more CFCs in these aerosol products • Difluoroethane – two flourines, no chlorines Melanoma incidence in US • Rates of melanoma in the US, from 1974 to 2002 • Among the white population, the rates are going up and up and up o Is this because of ozone depletion? o The answer is no o Things can be correlated without being causally related to each other Correlation versus causation • Two things can be correlated without one causing the other • Many possible explanations for melanoma increase in US o (e.g.) folks are living longer o Get increased UV just by being higher up or living further south • Maybe increase UV awareness leads to more use of sunblock leads to more time outdoors (exposure to UV rays) leads to more melanoma Projected Cl• in atmosphere • The projection is 2100 • Not even at 2100 is at the level of 1950 • It takes a long time This looks like cause and eff
More Less
Unlock Document

Only pages 1 and half of page 2 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit