1. Dimethyl Sulfide Emissions from Dairies and Agriculture as a Potential Contributor to Sulfate Aerosols in the California Central Valley
Eric Lebel
Providence College Class of 2015
Student Airborne Research Program 2014 ~ August 5, 2014
Dr. Don Blake, University of California – Irvine
Josette Marrero, Research Mentor
(0:15)
Introduce
Read Title

2. Dimethyl Sulfide Concentrations Around the Salton Sea
<2000 ft.
Dimethyl sulfide (DMS) concentrations seem to be higher over the land near the Salton Sea
(1:15)
Salton Sea is new
Flight path
Cans opened at 1000 ft pass
seems to be a correlation
curious because DMS is marine gas

3. A two-tailed T-Test shows that the means are not similar
[DMS] (pptv) at the Salton Sea
Land
Sea 38 2 8 9 4 11 13 20 6 15 3 21 1 7 17
Average 14
Variable
Mean Difference
95.00% Confidence Interval t df
p-Value
Lower Limit
Upper Limit
LOG_LAND
0.441
0.120
0.763
2.937
14.451
0.011
LOG_SEA
P < 0.05,
H0 is rejected
(2:15)
Averages seem different
Transform data to normalize
Confidence level of 95%
P value is less than 0.05
reject null hypothesis for alternative
----- Meeting Notes (8/3/14 13:03) -----
Bring out P-value
α = 0.05
H0 = The means are the same
HA = The means are different

4. The DMS over the land is probably not coming from the Salton Sea
Methyl Iodide Concentrations Around the Salton Sea
<2000 ft.
Methyl iodide (CH3I)
Emitted from marine sources
Longer lifetime than DMS
DMS (ppt)
CH3I (ppt)
Air
10.5
0.35
Ground
287.3
1.14
(3:15)
Methyl idodide is a marine gas, concentration higher over sea
Comparison with ground samples:
3-fold difference between ground and air for CH3I
27-fold difference for DMS
Also helps to show that DMS probably didn't come from ocean
27x difference
3x difference

5. Marine transport is unlikely due to reactions and dilution
Can 1419, south of Salton Sea
P. Alt. = 1103 ft
DMS = 21 pptv
There is a significant amount of uncertainty in the trajectories.
(3:45)
Hysplit models show that the air came from the sea
Uncertainty in altitude
Most of DMS would react in this amount of time anyway

6. The DMS likely comes from local sources
DMS is primarily emitted from lactating cows in dairies and from manure.
Literature has reported that DMS can be emitted from terrestrial plants.
Can DMS also be emitted from other agricultural sources as well?
Agriculture?
(4:30)
Local sources
known that DMS comes from dairies and manure
CAN be emitted from plants in smaller amounts
How significant is agriculture?

7. Comparing DMS and Ethanol around the Salton Sea shows some correlation
Joshua Richardson (SARP 2012) showed that ethanol can be a tracer for dairies.
(5:15)
Ethanol is emitted from dairies
DMS vs. Ethanol
outlier suggest a different source than dairies
High DMS, but low ethanol

8. DMS is normally emitted from marine environments and can form CCN and sulfur aerosols
dimethyl
sulfide
(6:15)
Studying DMS is important to understanding aerosols!
COULD be important to formation of aerosols

9. Oxidation of DMS in the atmosphere can lead to aerosols
(Sulfuric acid)
Precursor to aerosols
Reaction with OH is most common; pathway determines aerosol formation
(Sulfur dioxide)
Main contributors to aerosols
(Methanesulfonic acid)
(7:00)
Multiple oxidation pathways
OH during day, form so2  sulfuric acid and msa = aerosols
NO3 happens quicker at night
(DMS)
(Methanesulfinic acid)

10. Dimethyl Sulfide Concentrations Around the Salton Sea
<2000 ft.
An increase in particle count was found around the same location as the above-average DMS
(7:30)
Justin Trousdell (Bertram group) found a spike in particle count

11. Central Valley, SARP 2014
That’s not smoke!!
(8:00)

12. DMS Concentrations in the Central Valley,
The Central Valley, excluding dairies, also shows elevated DMS concentrations
DMS Concentrations in the Central Valley,
Excluding Dairies
<2000 ft.
Boundary excluding dairies
Average DMS <2000 ft: pptv
(8:45)
DMS over land near the Salton Sea:
14 pptv

13. The entire Central Valley shows high DMS concentrations
DMS Concentrations in the Central Valley
<2000 ft.
Average DMS <2000 ft for all SARP years: pptv
(9:30)

14. Estimates of the contribution of DMS to aerosol formation show that it may not be negligible
27.2 pptv DMS from all SARP years = µg/m3
61.1% mass conversion of DMS to aerosol
0.045 µg/m3 aerosols from DMS
Central Valley had an average submicron particle count of 4 µg/m3
UHSAS data from the Bertram Group
(10:30)
Explain calculations
Lifetimes?
May not be negligible, especially in the regions with above-average DMS levels.
1.1 %
Chen, T.; Myoseon, J. Secondary organic aerosol formation from photooxidation of a mixture of dimethyl sulfide and isoprene. Atmospheric Environment ,

15. DMS Concentrations in the Central Valley,
With 2014 Flight Track
More samples should be taken in the northern Central Valley to evaluate how DMS contributes to particle formation
(11:00)
This flight path did not sample the regions with highly concentrated DMS
We only sampled a small section of the Central Valley in 2014

16. Conclusions Elevated DMS was seen over the land around the Salton Sea.
A spike in the particle count corresponded to higher DMS levels.
Since DMS is known to contribute to aerosol formation, DMS concentrations were analyzed in the Central Valley.
Especially high concentrations of DMS were found over dairies and in the north of the sampled region.
Future studies should be conducted to further understand the connection between DMS and aerosol formation in the Central Valley.
The estimated contribution of DMS to particle formation is not negligible.
(12:00)
Salton Sea – concentrations, particle count
Central Valley – high DMS
Future studies to better understand connection between DMS and aerosol, as estimate shows connection may not be negligible

17. Acknowledgements Dr. Don Blake and Josette Marrero Dr. Jack Kaye, NASA
Rick Shetter and Dr. Emily Schaller, NSERC
Jen Broughton, Steve Schill
Dr. Jessie Sagona
Rowland-Blake Lab Group
Nick Heath