Surfactant control of gas transfer velocity along an offshore coastal transect: results from a laboratory gas exchange tank

Ryan Pereira, K. Schneider-Zapp, R. C. Upstill-Goddard

Research output: Contribution to journalArticlepeer-review

380 Citations (Scopus)
43 Downloads (Pure)

Abstract

We measured total surfactant activity (SA; Triton T-X-100 equivalent) and CDOM absorbance (cm-1) in the surface microlayer (SML) and subsurface water (SSW) seasonally (2012-2013) along a 20 km coastal transect (North East UK), and evaluated corresponding values of the gas transfer velocity (kw; cm hr-1) using a custom designed air-sea gas exchange tank. Spatial SA variability exceeded its temporal variability. Overall, SA varied five-fold between all samples (0.08 - 0.38 mg L-1 T-X-100), being highest in the SML during summer. SML SA enrichment factors relative to SSW were ~ 1.0 - 1.9, except for two values (0.75; 0.89: February 2013). CDOM absorbance (250 - 450 nm), the CDOM spectral slope ratio (SR = S275–295 / S350–400) and the 250:365 nm CDOM absorbance ratio (E2 : E3) demonstrate the potential for terrestrially-derived CDOM to be biogeochemically processed in North Sea coastal waters. The range in corresponding k660 (kw for CO2; freshwater; 20 °C) was 6.8 - 22.0 cm hr-1. The film factor R660 (the ratio of the scaled transfer velocity k660 to the one of clean water) strongly correlates with SA (r ≥0.70, p ≤0.002, each n = 16) with high SML SA correlated to k660 suppression ~14 - 51 % relative to clean laboratory water, highlighting strong spatio-temporal gradients in gas exchange due to varying surfactant in these coastal waters. Such variability should be taken account of when evaluating marine trace gas sources and sinks.
Original languageEnglish
Pages (from-to)1-17
Number of pages17
JournalBiogeosciences Discussions
Volume2016
DOIs
Publication statusPublished - 18 Jan 2016

Fingerprint Dive into the research topics of 'Surfactant control of gas transfer velocity along an offshore coastal transect: results from a laboratory gas exchange tank'. Together they form a unique fingerprint.

Cite this