Surface Tension Measurements of Seawater and its Organic Components

This study aims to quantify the variation in the surface tension of seawater over an 8 week period and to analyze the contribution of organic components, such as surfactants, to this variation. The analysis of surface tension and surfactants provides information about the physical, biological, and chemical processes occurring in air-sea interactions. The process of bubble-bursting, the production of submicron atmospheric particles by ocean waves crashing, relates surface tension and surfactants. On a biweekly basis, seawater (SW) samples were collected from Scipps pier, and filtered seawater (FSW) was made by running SW through a 0.2 micron filter. The Wilhelmy Plate Method was used in the KRUSS K11 Tensiometer to find surface tension values. The SW samples were atomized and collected onto 37 mm Teflon filters at a flow rate of 8 L/min for 3-5 hours. The filters were analyzed by Fourier Transform Infrared (FTIR) spectroscopy. SW had an average surface tension of 72.82 mN/m, which was higher than FSW by ~1 mN/m. The SW had a standard deviation of 0.139 whereas FSW was 0.330. The variability of FSW was greater than that of SW. We also investigated how different bacteria affect the surface tension of SW. 9 different bacteria was used to create cultures by adding either Casein (CAS) or Bovine Serum Albumin (BSA) proteins. The control groups generated for both CAS and BSA had surface tension similar to that of deionized water, making the results indistinguishable from the control. Further research is needed using a protein with higher surface tension, such as glucose. This research poses new questions and confirms the need to expand knowledge on surface tension and surfactants involved with the sea-surface.