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

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

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

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

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

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?

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

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 http://saga.pmel.noaa.gov/review/dms_climate.html http://apollo.eas.gatech.edu/yhw/Cindy/tropo.htm

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) http://joseba.mpch-mainz.mpg.de/dms.htm

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

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

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: 12.9 pptv (8:45) DMS over land near the Salton Sea: 14 pptv

The entire Central Valley shows high DMS concentrations DMS Concentrations in the Central Valley <2000 ft. Average DMS <2000 ft for all SARP years: 27.2 pptv (9:30)

Estimates of the contribution of DMS to aerosol formation show that it may not be negligible 27.2 pptv DMS from all SARP years = 0.074 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. 2012. 46, 271-278.

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

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

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