questions
DESCRIPTION
QUESTIONS. Is the rate of reaction of S(IV) more likely to be slower than calculated for a cloud droplet or a rain droplet? Why? If you wanted to determine whether a species would be a good oxidant in the aqueous phase what are the 3 things you would need to know?. CHAPTER 13: ACID RAIN. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/1.jpg)
QUESTIONS
1. Is the rate of reaction of S(IV) more likely to be slower than calculated for a cloud droplet or a rain droplet? Why?
2. If you wanted to determine whether a species would be a good oxidant in the aqueous phase what are the 3 things you would need to know?
![Page 2: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/2.jpg)
CHAPTER 13: ACID RAIN
![Page 3: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/3.jpg)
NATURAL pH OF RAIN
• Equilibrium with “natural” CO2 (280 ppmv) results in a rain pH of 5.7:
2 2 -12 2 2
7 2 2 3 1
2 103 3 2
( ) 3 10 M atm
9 10 M
7 10 M
H O
HCO g CO H O K
CO H O HCO H K
HCO CO H K
2
1/21[ ] ( ) H COH K K P
This pH can be modified by natural acids (H2SO4, HNO3, RCOOH…) and bases (NH3, CaCO3) natural rain has a pH in range 5-7
“Acid rain” refers to rain with pH < 5 damage to ecosystems
![Page 4: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/4.jpg)
ENVIRONMENTAL IMPACTS OF ACIDITY
![Page 5: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/5.jpg)
PRECIPITATION PH OVER THE UNITED STATES: 1994
![Page 6: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/6.jpg)
CHEMICAL COMPOSITION OF PRECIPITATION
Electoneutrality condition for acid rain based on predominant ions:[H+] + [NH4
+] +2[Ca2+] = 2[SO42-] + [NO3
-]
![Page 7: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/7.jpg)
PH MEASURED IN CLOUD AND FOG WATER
Courtesy: Jeff Collett
![Page 8: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/8.jpg)
GLOBAL SULFUR BUDGET [Chin et al., 1996](flux terms in Tg S yr-1)
Phytoplankton
(CH3)2S
SO2
1.3d
DMS1.0d
OHNO3
Volcanoes CombustionSmelters
SO42-
3.9d
22
10 64
OH
cloud, H+, H2O2
42
8184
dep27 dry20 wet
dep6 dry44 wet
H2SO4(g)
![Page 9: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/9.jpg)
SULFUR CHEMISTRY
Gas phase oxidation:SO2 + OH … H2SO4 slow, lifetime of SO2 ~weeks
2 2 2
24
16 3 2 2
16 13 14 15
[ ][ ][ ( )][ ]
SO H O
d SOk HSO H O aq H
dtk K K K P P
2
2 213
[ ]
SO
SO H OK
P
R16 very fast:Titrates either SO2 or H2O2 in a cloud
22 4 4H SO (aq) SO 2H
Aside: dissociation of sulfuric acid:
In cloud oxidation (focus here on H2O2 oxidation at low pH):SO2(g) SO2
.H2O (13)SO2
.H2O HSO3- + H+ (14)
H2O2(g) H2O2(aq) (15)HSO3
- + H2O2(aq) + H+ SO42- + 2H+ + H2O (16)
Remember equilibrium constants:
etc….
Rate of aqueous phase sulfate formation therefore:
![Page 10: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/10.jpg)
GLOBAL SULFUR EMISSION TO THE ATMOSPHERE
Chin et al. [2000]
2001 estimates (Tg S yr-1): Industrial 57 Volcanoes 5 Ocean 15 Biomass burning 1
![Page 11: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/11.jpg)
22 4 4H SO (aq) SO 2H
![Page 12: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/12.jpg)
Efficient scavengingof both HNO3(g) and nitrate aerosol
3 3HNO (aq) NO H
![Page 13: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/13.jpg)
Efficient scavengingof both NH3(g) and ammonium aerosol
3 4NH (aq) H NH
![Page 14: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/14.jpg)
BUT ECOSYSTEM ACIDIFICATION IS PARTLY A TITRATION PROBLEM FROM ACID INPUT OVER MANY YEARS
Acid-neutralizing capacity (ANC)from CaCO3 and other bases
Acid fluxFH+
0
acidificationt
HF dt ANC
![Page 15: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/15.jpg)
AREAS (IN BLACK) WITH LOW ACID-NEUTRALIZING CAPACITY
![Page 16: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/16.jpg)
ACID RAIN: US-CANADA ENVIRONMENTAL POLICY ISSUE OF 1970’s - 1980’s
http://archives.cbc.ca/environment/pollution/topics/584/
Dying lakes, dying cropsA long awaited agreement
A policy debate that was ultimately addressed with domestic legislation (Eastern Canada Acid Rain Program in 1985 and US amendment to Clean Air Act in 1991)
![Page 17: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/17.jpg)
EXCESS NITROGEN DEPOSITION CAN ALSO LEAD TO EUTROPHICATION OF LAKES AND RIVERS
Excessive deposition of assimilable N eutrophication accumulation of algae suppression of supply of O2 to deep water hypoxia
N inputs to the Chesapeake Bay have increased 7-fold over natural!
1987 agreement to reduce N inputs by 40%
[Boesch et al., 2001]
Watershed estimates of controllable N inputs to Chesapeake
![Page 18: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/18.jpg)
SOLUTIONS TO ACID DEPOSITION?
CHEMICAL:Liming – addition of calcium carbonate.Works, but is expensive and only a short term solution
BIOLOGICAL:Long-term solution – reduce emissions and let lakes recover naturally
www.life.uiuc.edu/ib/349/lectures/Acid04.ppt
![Page 19: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/19.jpg)
TRENDS IN U.S. EMISSIONS OF SO2
![Page 20: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/20.jpg)
AMMONIUM AND SULFATE TRENDS, 1985-2004
NH4+
SO42-
Lehmann et al. [2007]
![Page 21: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/21.jpg)
CHANGE IN PRECIPITATION PH FROM 1994 TO 2008
![Page 22: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/22.jpg)
DEPLETION OF BASE CATIONS FROM ACID RAIN(Hubbard Brook Experimental Forest, New Hampshire)
![Page 23: QUESTIONS](https://reader035.vdocuments.us/reader035/viewer/2022062517/568137e2550346895d9f8929/html5/thumbnails/23.jpg)
STILL A MAJOR CONCERN IN INDUSTRIALIZING NATIONS…