The influence of perfluoroalkyl acid (PFAA) concentrations on the enrichment of PFAAs in sea spray aerosols (SSA) in a laboratory study
Observations on relations between marine aerosol fluxes and surface-generated noise in the southern Baltic Sea
This study presents the preliminary results of combining underwater acoustic am- bient noise measurements with those of in-situ sea spray fluxes (SSF). Hydroacoustic measure- ments (in the frequency range 80 Hz —12.5 kHz) were made using an underwater noise recording system developed at the Institute of Oceanology of the Polish Academy of Sciences which was then deployed in the southern Baltic Sea. The simultaneous measurements of coarse sea spray fluxes (with particle diameters ranging from 0.5 to 47 μm) were made on board the r/v Ocea- nia using the gradient method. Observations were conducted for the duration of the passage of an atmospheric front that lasted 2.5 days (60 hours of measurements). There were signif- icant differences in the sound pressure level (SPL) and aerosol fluxes observed between the first part of measurements (developing wave state) and the second part (developed waves). Wave parameters, such as peak period , significant wave height, wave age, and mean wave slope acquired from the WAM (WAve Model), were used to investigate the impact of wave field properties on noise and aerosol flux measurements. We observed different behaviours in the power spectrum density (PSD) levels of noise for these parameters depending on the wave state
Brine rejection and hydrate formation upon freezing of NaCl aqueous solutions
Studying the freezing of saltwater on a molecular level is of fundamental importance for improving freeze desalination techniques. In this study, we investigate the freezing process of NaCl solutions using a combination of X-ray diffraction and molecular dynamics simulations (MD) for different salt-water concentrations, ranging from seawater conditions to saturation. A linear superposition model reproduces well the brine rejection due to hexagonal ice Ih formation and allows us to quantify the fraction of ice and brine. Furthermore, upon cooling at T = 233 K, we observe the formation of NaCl·2H2O hydrates (hydrohalites), which coexist with ice Ih. MD simulations are utilized to model the formation of NaCl crystal hydrates. From the simulations, we estimate that the salinity of the newly produced ice is 0.5% mass percent (m/m) due to ion inclusions, which is within the salinity limits of fresh water. In addition, we show the effect of ions on the local ice structure using the tetrahedrality parameter and follow the crystallite formation using the ion coordination parameter and cluster analysis.