Environmental Chemistry

Homework/Quizzes. 25% Class Participation Homework/Quizzes           25% Class Participation             15% Midterm Exam  (Week of 3/19)    15% Research Paper 20% Final                                       25% Homework = 15% Quizzes = 10% 8 total quizzes, 3 are dropped = 5 counted Each quiz is 2 pts toward overall grade I will weight individual part 25% and team part 75% As of now, the class average quiz score is 84% (1 of 4 dropped)

Climate in the news… https://www.nytimes.com/interactive/2018/03/16/climate/us-winter- warming.html?hp&action=click&pgtype=Homepage&clickSource=story- heading&module=second-column-region&region=top- news&WT.nav=top-news

Stratospheric Chemistry The Ozone Layer - Shield against dangerous incoming radiation How does radiation interact with molecules in the stratosphere? What processes form and maintain the ozone layer? How much ozone is there, and how is it distributed? How do we know? How have human activities altered ozone chemistry and the ozone layer itself? What controls have been put in place to protect the ozone layer? Ozone is a “success story” in environmental chemistry – what lessons can we learn from it? The stratosphere is also a good “case study” in how atmospheric chemistry works

Ozone layer characteristics

Global ozone Ozone column – total amount of ozone between ground and top of atmosphere Dobson Unit – an amount of ozone equivalent to a 0.01 mm thick layer of ozone when brought to ground level 300 DU = 3 mm ozone colum

How is ozone measured?

Ozone Update NASA OzoneWatch: http://ozonewatch.gsfc.nasa.gov/ NOAA ESRL Global Monitoring Division Webpage: http://www.esrl.noaa.gov/gmd/dv/spo_oz/

Air circulation in the stratosphere Air enters the stratosphere through the tropopause in the tropics T is very low (200 K), so air in strat is DRY (~ 5 ppmv H2O) T increases with alt so air is stratified – no vertical motion Air stays in stratosphere for ~5 yrs before returning to troposphere

Solar spectrum

O2 Absorption Spectrum Graedel and Crutzen, Atmospheric Change, 1993 Schumann-Runge continuum ionization continuum Herzberg continuum Schumann-Runge bands Graedel and Crutzen, Atmospheric Change, 1993

Ozone UV absorption spectrum Graedel and Crutzen, Atmospheric Change, 1993

Actinic Flux O2 O3

Comparing to observations Ozone concentrations are lower than predicted based on oxygen-only chemistry

Global ozone Ozone column – total amount of ozone between ground and top of atmosphere Dobson Unit – an amount of ozone equivalent to a 0.01 mm thick layer of ozone when brought to ground level 300 DU = 3 mm ozone colum

https://www. researchgate https://www.researchgate.net/figure/Ozone-absorption-of-UV-radiation-with-erythema-and-DNA-action-spectra_fig4_235201203