Transition Metal Associations with Primary Biological Particles in Sea Spray Aerosol Generated in a Wave Channel Timothy L. Guasco, †,∥ Luis A. Cuadra-Rodriguez, † Byron E. Pedler, ‡ Andrew P. Ault, §,⊥ Douglas B. Collins, † Defeng Zhao, †,# Michelle J. Kim, ‡ Matthew J. Ruppel, † Scott C. Wilson, † Robert S. Pomeroy, † Vicki H. Grassian, § Farooq Azam, ‡ Timothy H. Bertram, † and Kimberly A. Prather †,‡, * † Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, 92093 ‡ Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, 92093 § Department of Chemistry, University of Iowa, Iowa City, Iowa, 52242 * S Supporting Information ABSTRACT: In the ocean, breaking waves generate air bubbles which burst at the surface and eject sea spray aerosol (SSA), consisting of sea salt, biogenic organic species, and primary biological aerosol particles (PBAP). Our overall understanding of atmospheric biological particles of marine origin remains poor. Here, we perform a control experiment, using an aerosol time-of-flight mass spectrometer to measure the mass spectral signatures of individual particles generated by bubbling a salt solution before and after addition of heterotrophic marine bacteria. Upon addition of bacteria, an immediate increase occurs in the fraction of individual particle mass spectra containing magnesium, organic nitrogen, and phosphate marker ions. These biological signatures are consistent with 21% of the supermicrometer SSA particles generated in a previous study using breaking waves in an ocean- atmosphere wave channel. Interestingly, the wave flume mass spectral signatures also contain metal ions including silver, iron, and chromium. The nascent SSA bioparticles produced in the wave channel are hypothesized to be as follows: (1) whole or fragmented bacterial cells which bioaccumulated metals and/or (2) bacteria-derived colloids or biofilms which adhered to the metals. This study highlights the potential for transition metals, in combination with specific biomarkers, to serve as unique indicators for the presence of marine PBAP, especially in metal-impacted coastal regions. 1. INTRODUCTION Atmospheric aerosol particles impact human health, air quality, and the Earth’s climate in important, yet poorly understood, ways. 1,2 The parameters that play a role in determining the effects of aerosols are chemical composition, 3−8 particle size, 8−11 and morphology. With regard to climate, aerosols impact the radiative balance by scattering and absorbing radiation as well as by acting as cloud condensation (CCN) and ice nuclei (IN) in processes referred to as the direct and indirect effects, respectively. 11,12 Due to the wide array of aerosol sources and the multitude of transformations particles can undergo in the atmosphere, there are numerous particle types which are composed of heterogeneous mixtures of many chemical components. 13 Primary biological aerosol particles (PBAP) are a particularly interesting class of particles of which there is an extreme paucity of knowledge. 14 PBAP refers to solid airborne particles derived from biological organisms (e.g., microorganisms, fragments of biological materials, and cellular exudates) that can profoundly influence climate and the hydrological cycle by serving as IN and CCN. 15−19 In particular, bacteria, a common PBAP, have been shown to be the most efficient IN, initiating ice formation at temperatures as warm as −2 °C. 14,20 In addition to climate effects, PBAP are believed to impact the cytotoxicity of airborne particulate matter. 14,21 While the health and climate impacts of PBAP have recently led to increased attention, there remain many questions and different opinions regarding the extent of control that PBAP exert on atmospheric processes, in part due to conflicting reports on the atmospheric flux and concentrations of PBAP. 18,22−32 Although numerous field studies have highlighted the possibility that PBAP can serve as an important source of IN on regional scales during different seasons, 16,17,33,34 local and global simulations have reported wide-ranging results with regard to the role of PBAP in atmospheric ice formation. 30,35−38 In order to develop a Received: July 19, 2013 Revised: November 25, 2013 Accepted: December 13, 2013 Published: December 13, 2013 Article pubs.acs.org/est © 2013 American Chemical Society 1324 dx.doi.org/10.1021/es403203d | Environ. Sci. Technol. 2014, 48, 1324−1333