Influence of Biogenic Surfactants on Gas Exchange at the Air-Sea Interface

海洋浮游植物产生的表面活性有机物Frew 9301334已知可以减少空气-水界面的气体交换。在中等风速下，表面活性剂对气体传输速度-风速关系具有一阶效应，均方波斜率提供了不同风速和地表粘弹性条件下传输速度Kw的参数。这项持续研究的目标是在天然表面活性剂存在的情况下进一步完善气体交换的参数化，并将表面活性剂用作一种工具来研究小尺度波和湍流作为影响气体交换的因素所起的作用。在两个不同尺度的圆形风浪水槽中，将应用表征三维海浪谱和测量粘弹性阻尼的新技术来测量Kw。一系列表面活性化合物，包括合成和天然表面活性剂，可产生对动态表面粘弹性具有不同弹性和粘性贡献的薄膜，将用于修改Kw测量过程中的波场、三维波谱和气体传输，并区分涉及小尺度波或近地表湍流的粘弹性(Marangoni)衰减机制。这项研究与上层海洋生物地球化学过程模型有关，气体交换是其中的一个重要组成部分。

FREW 9301334 Surface-active organic matter produced by marine phytoplankton is known to reduce the exchange of gases at the air-water interface. Surfactants have a first-order effect on the gas transfer velocity- wind speed relationship up to moderate wind speeds and the mean square wave slope offers a parameterization of transfer velocity Kw at different wind speeds and surface viscoelastic conditions. The objective in this continuing research is to further refine this parameterization for gas exchange in the presence of natural surfactants and to use surfactants as a tool to examine the role of small-scale waves and turbulence as agents affecting gas exchange. New techniques for characterizing 3-dimensional wave spectra and for measurement of viscoelastic damping will be applied to measurements of Kw in two circular wind-wave tanks of different scales. A range of surface-active compounds, including synthetic and natural surfactants, which yield films with different elastic and viscous contributions to the dynamic surface viscoelasticity will be used to modify the wave field during measurements of Kw and the three-dimensional wave spectra and gas transfer and to discriminate between mechanisms involving viscoelastic (marangoni) damping of either small scale wave or near-surface turbulence. The research is relevant to models of upper ocean biogeochemical processes in which gas exchange is an important component.