Study: Ocean waves play greater role in trapping CO2

Digital Journal  

2018-05-30

“Sea spray aerosol was thought for a long time to be just salt — sodium chloride — and that’s not true,” Grassian told Ensia. “There’s a lot more that comes out of the water — viruses, bacteria, organic compounds, parts of cell walls." “There’s a lot of interplay at that air-ocean interface,” Grassian added. “Gases and particles go in and come out of the ocean, so what’s in the ocean is going to affect what gets into the air and vice versa.”

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The surprising effect of ocean waves on global climate

DownToEarth  

2017-08-25

Breaking waves are the stuff of romance and poetry, but the spray they generate is serious business. Just ask Vicki Grassian, who thinks about what crashing waves mean for clouds and, ultimately, our ability to understand and adapt to our changing climate. In more than 20 years as a professor in the University of Iowa’s chemistry department, Grassian earned the title “dust queen” for her studies of how mineral particles make their way from land into the sky. The specialized tools and expertise required to study dust eventually drew her to the Department of Chemistry and Biochemistry and the Scripps Institution of Oceanography at the University of California, San Diego, where investigators have spent much of the past decade tackling a tantalizing question: How does the ocean affect Earth’s atmosphere?...

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How plankton and bacteria shape ocean spray

PHYS ORG  

2017-05-11

Molecules that plankton and bacteria secrete can become incorporated into the bubbles, which ultimately release these compounds into the air. The molecules also mix with the chemicals and salts inside the particles, meaning that they are less able to carry water from the ocean—a property called hygroscopicity. This, in turn, affects the way the aerosol interacts with the sun's rays and influences cloud formation. "We were surprised by how distinct the changes in the chemicals in the individual aerosol particles were," says senior author Vicki H. Grassian, co-director of the Center for Aerosol Impacts on Climate and the Environment at the University of California, San Diego. "This is a great result for us, as it helps us see more clearly how sea spray aerosol is involved in climate."

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Optical Properties of Humic Material Standards: Solution Phase and Aerosol Measurements

Deokhyeon Kwon, Matthew J Sovers, Vicki H Grassian, Paul D Kleiber, Mark Alan Young

2018 Aerosols generated from aqueous samples of readily obtainable humic material standards are often used as proxies for organic particulates found in the atmosphere in various investigations, such as consideration of radiative forcing effects. Here, we present results for the retrieved complex index of refraction, m = n + ik, at a wavelength of 403 nm for aerosols prepared from six humic material standards using a calibrated cavity ring-down spectrometer: a humic acid sodium salt, Pahokee peat humic and fulvic acids, Elliott soil humic and fulvic acids, and Suwannee river fulvic acid. In addition, we have conducted UV–vis spectrometric studies to measure the mass absorption coefficients, molar absorptivities, and absorption Ångstrom exponents of bulk aqueous solutions of the humic materials. We find clear differences between the humic acid (HA) and fulvic acid (FA) samples with the HA having larger values for the imaginary part of the refractive index, k. The mean value for the HA samples is k = 0.170 while the mean is k = 0.037 for the FA materials. We have examined correlations between the retrieved refractive index and humic material characteristics obtained from spectroscopic and elemental analysis, including aromatic content and the oxygen-to-carbon atomic ratio, where the molar absorption coefficient yields the strongest correlation. Finally, we compare the humic material optical properties to those of authentic and laboratory generated organic carbon samples in order to assess the usefulness of these humic standards as proxies for light absorbing aerosol.

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Impacts of Lipase Enzyme on the Surface Properties of Marine Aerosols

Jamie M Schiffer, Man Luo, Abigail C Dommer, Gray Thoron, Matthew A Pendergraft, Mitchell V Santander, Dolan Lucero, Emilia Pecora de Barros, Kimberly Ann Prather, Vicki H Grassian, Rommie E Amaro

2018 Triacylglycerol lipases have recently been shown to be transferred from the ocean to the atmosphere in atmospheric sea spray aerosol (SSA). Lipases have the potential to alter the composition of SSA; however, the structure and properties of enzymes in the high salt, high ionic strength, and low pH conditions found in SSA have never been explored. Here, we study the dynamics of Burkholderia cepacia triacylglycerol lipase (BCL) at SSA model surfaces comprised of palmitic acid and dipalmitoylphosphatidic acid (DPPA), two commonly found lipids at SSA surfaces. Surface adsorption Langmuir isotherm experiments and all-atom explicit solvent molecular dynamics simulations together illuminate how and why BCL expands the ordering of lipids at palmitic acid surfaces the most at pH < 4 and the least in DPPA surfaces at pH 6. Taken together, these results represent a first glimpse into the complex interplay between lipid surface structure and protein dynamics within enzyme-containing aerosols.

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Particle Concentrations in Occupational Settings Measured with a Nanoparticle Respiratory Deposition (NRD) Sampler

Larissa V Stebounova, Natalia I Gonzalez-Pech, Jae Hong Park, T Renee Anthony, Vicki H Grassian, Thomas M Peters

2018 There is an increasing need to evaluate concentrations of nanoparticles in occupational settings due to their potential negative health effects. The Nanoparticle Respiratory Deposition (NRD) personal sampler was developed to collect nanoparticles separately from larger particles in the breathing zone of workers, while simultaneously providing a measure of respirable mass concentration. This study compared concentrations measured with the NRD sampler to those measured with a nano Micro Orifice Uniform-Deposit Impactor (nanoMOUDI) and respirable samplers in three workplaces. The NRD sampler performed well at two out of three locations, where over 90% of metal particles by mass were submicrometer particle size (a heavy vehicle machining and assembly facility and a shooting range). At the heavy vehicle facility, the mean metal mass concentration of particles collected on the diffusion stage of the NRD was 42.5 ± 10.0 µg/m3, within 5% of the nanoMOUDI concentration of 44.4 ± 7.4 µg/m3. At the shooting range, the mass concentration for the diffusion stage of the NRD was 5.9 µg/m3, 28% above the nanoMOUDI concentration of 4.6 µg/m3. In contrast, less favorable results were obtained at an iron foundry, where 95% of metal particles by mass were larger than 1 µm. The accuracy of nanoparticle collection by NRD diffusion stage may have been compromised by high concentrations of coarse particles at the iron foundry, where the NRD collected almost 5-fold more nanoparticle mass compared to the nanoMOUDI on one sampling day and was more than 40% different on other sampling days. The respirable concentrations measured by NRD samplers agreed well with concentrations measured by respirable samplers at all sampling locations. Overall, the NRD sampler accurately measured concentrations of nanoparticles in industrial environments when concentrations of large, coarse mode, particles were low.

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Crystal Clear? Microspectroscopic Imaging and Physicochemical Characterization of Indoor Depositions on Window Glass

Victor W Or, Michael R Alves, Michael Wade, Sarah Schwab, Richard L Corsi, Vicki H Grassian

2017 Deposition and surface-mediated reactions of adsorbed species can play a role in the level of exposure of occupants to indoor pollutants, which include gases and particles. Detailed molecular-level descriptions of these processes occurring on indoor surfaces are difficult to obtain because of the ever-increasing types of surfaces and their proximity to a variety of different indoor emission sources. The results of an investigation of interactions of glass surfaces in unique indoor environments are described here. Window glass, a ubiquitous indoor surface, was placed vertically in six different locations to assess differences in particle and coating depositions. Atomic force microscopy–photothermal infrared (AFM–PTIR) spectroscopic analysis of these glass surfaces reveals differences in morphology and chemical composition, which reflects the diversity of surface processes found in local environments indoors. Overall, this detailed microspectroscopic imaging method shows deposition of particles and the formation of organic thin films that increase the surface area and surface roughness of the glass surface. PTIR spectroscopy demonstrates that depositions can be linked to primary emitters intrinsic to each of the different local environments.

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A Mesocosm Double Feature: Insights into the Chemical Makeup of Marine Ice Nucleating Particles

Christina S McCluskey, Thomas CJ Hill, Camille M Sultana, Olga Laskina, Jonathan Trueblood, Mitchell V Santander, Charlotte M Beall, Jennifer M Michaud, Sonia M Kreidenweis, Kimberly A Prather, Vicki Grassian, Paul J DeMott

2017 The abundance of atmospheric ice nucleating particles (INPs) is a source of uncertainty for numerical representation of ice-phase transitions in mixed-phase clouds. While sea spray aerosol (SSA) exhibits less ice nucleating (IN) ability than terrestrial aerosol, marine INP emissions are linked to oceanic biological activity and are potentially an important source of INPs over remote oceans. Inadequate knowledge of marine INP identity limits the ability to parameterize this complex INP source. A previous manuscript described abundances of marine INPs in relation to several aerosol composition and ocean biology observations during two laboratory mesocosm experiments. In this study, the abundances and chemical and physical properties of INPs found during the same mesocosm experiments were directly probed in SSA, seawater, and surface microlayer samples. Two unique marine INP populations were found: 1) dissolved organic carbon INPs are suggested to be composed of IN-active molecules, and 2) particulate organic carbon INPs are attributed as intact cells or IN-active microbe fragments. Both marine INP types are likely to be emitted into SSA following decay of phytoplankton biomass when 1) the surface microlayer is significantly enriched with exudates and cellular detritus and SSA particles are preferentially coated with IN-active molecules or 2) diatom fragments and bacteria are relatively abundant in seawater and therefore more likely transferred into SSA. These findings inform future efforts for incorporating marine INP emissions into numerical models and motivate future studies to quantify specific marine molecules and isolate phytoplankton, bacteria, and other species that contribute to these marine INP types.

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