The Sea Spray Chemistry and Particle Evolution Study (SeaSCAPE): Overview and Experimental Methods

Abstract

Marine aerosols strongly influence climate through their interactions with solar radiation and clouds. However, significant questions remain regarding the influences of biological activity and seawater chemistry on the flux, chemical composition, and climate-relevant properties of marine aerosols and gases. Wave channels, a traditional tool of physical oceanography, have been adapted for large-scale ocean-atmosphere mesocosm experiments in the laboratory. These experiments enable the study of aerosols under controlled conditions which isolate the marine system from atmospheric anthropogenic and terrestrial influences. Here, we present an overview of the 2019 Sea Spray Chemistry and Particle Evolution (SeaSCAPE) study, which was conducted in an 11,800 L wave channel which was modified to facilitate atmospheric measurements. The SeaSCAPE campaign sought to determine the influence of biological activity in seawater on the production of primary sea spray aerosols, volatile organic compounds (VOCs), and secondary marine aerosols. Notably, the SeaSCAPE experiment also focused on understanding how photooxidative aging processes transform the composition of marine aerosols. In addition to a broad range of aerosol, gas, and seawater measurements, we present key results which highlight the experimental capabilities during the campaign, including the phytoplankton bloom dynamics, VOC production, and the effects of photochemical aging on aerosol production, morphology, and chemical composition. Additionally, we discuss the modifications made to the wave channel to improve aerosol production and reduce background contamination, as well as subsequent characterization experiments. The SeaSCAPE experiment provides unique insight into the connections between marine biology, atmospheric chemistry, and climate-relevant aerosol properties, and demonstrates how an ocean-atmosphere-interaction facility can be used to isolate and study reactions in the marine atmosphere in the laboratory under more controlled conditions.

Atmospheric Benzothiazoles in a Coastal Marine Environment

“…Given the elevated water temperature, enclosed conditions, and low gas-phase flow rate of the SeaSCAPE ISV (described in Sauer, Mayer, and Lee et al), absolute gas-phase ISV concentrations exceeding ambient concentrations at the end of the pier is indicative of emissions to the gas phase. 47 Previously reported Henry's law constants for BT (K H′ , estimated from vapor pressure and solubility in Reddy et al, predicted from structure through various methods as reported in Sander, and predicted from structure based on HENRYWIN v. 3.10, EPA EPI Suite) range from 1.5 × 10 −5 to 2.6 × 10 −4 (dimensionless gas over liquid, converted assuming 25 °C). 53,54 Under the aqueous concentration (0.29 μg/L at day 1 sampling time, as shown in Table 1) and temperature conditions observed at SeaSCAPE, this would imply a maximum equilibrium gas concentration of BT between 0.7 and 12 ppt, a factor of 75−4.4 below the average concentrations observed in the ISV (53 ppt).…”

“…The results from this study derive primarily from Sea Spray Chemistry And Particle Evolution (Sea-SCAPE) 2019, a collaborative mesocosm experiment described in Sauer, Mayer, and Lee et al. 47 Coastal water (12,000 L) from Ellen Browning Scripps Memorial Pier (hereafter Scripps Pier) in La Jolla, CA, was transported into an indoor wave chamber facility (hereafter referred to as the wave channel), in which mechanically generated waves break on an artificial beach to create realistic primary sea spray aerosols. The natural coastal water was amended with nutrients to initiate an algal bloom of the naturally existing phytoplankton species, including three bloom experiments, replicating methodology described in Wang et al 48 Water from the wave channel was diverted through an inert glass and Teflon chamber forming an isolated sampling vessel (ISV), allowing analysis of gas-phase marine emissions.…”

“…The natural coastal water was amended with nutrients to initiate an algal bloom of the naturally existing phytoplankton species, including three bloom experiments, replicating methodology described in Wang et al 48 Water from the wave channel was diverted through an inert glass and Teflon chamber forming an isolated sampling vessel (ISV), allowing analysis of gas-phase marine emissions. This analysis focuses on the third algal bloom experiment, which lasted 20 days from July 24 to August 12, 2019, and is described in detail in Sauer, Mayer, and Lee et al 47 Periodically over the course of the bloom, water from the SeaSCAPE channel was collected for offline analysis of headspace gases (described below) and of extracted DOM chemical composition (also described below). One water sample directly from Scripps Pier was collected on July 23 for DOM extraction and analysis of dissolved analytes under ambient conditions.…”

“…VOCs both within the ISV and in the channel were additionally measured by Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus PTR-TOF by Aerodyne/Tofwerk). 47 Following the conclusion of SeaSCAPE, the Vocus was relocated to the end of the Scripps Pier for ambient coastal VOC sampling. A full description of Scripps Pier VOC sampling can be found in SI.…”

Emerging investigator series: surfactants, films, and coatings on atmospheric aerosol particles: a review

“…474 Another prominent technique used to investigate surfactants in SSA is the wave ume experiments conducted by the Center for Aerosol Impacts on Chemistry of the Environment (CAICE) at Scripps Institute of Oceanography. 475,476 Several CAICE studies have investigated composition and morphology of SSA containing surface-active organics produced in real seawater with phytoplankton blooms. 161,243,288,290,477 Ault et al 477 utilized Raman spectroscopy and SFG to demonstrate the presence of organic matter concentrated at the surface of SSA particles generated in a wave ume.…”