Abstract

The surface film of water (the laminar layer about 0.5 mm thick and the intermediate layer about 5 mm thick) is regarded as a ‘bottleneck’ for heat and mass exchange between the atmosphere and natural water bodies. The dependence of the surface film temperature on air and water temperature and humidity under laboratory conditions is described. As demonstrated, replacing a ‘warm’ by a ‘cold’ surface film results in the oxygen transfer rate increasing by 8%.

The surface film of natural water bodies is inhabited by specific neuston organisms. The freshwater zooneuston of large Siberian reservoirs is described, and their general similarity with the marine neuston of the Sea of Japan is shown. The statement is made that there are two ways in which the biota influence the properties of surface films: 1. mechanical – by providing turbulence in the laminar layer by the swimming action of small zooneuston organisms; and 2. chemical – by the influence of biogenic surfactants on the water film. Experimental evidence of the biotic influence is demonstrated.

Introduction

From the hydrophysical or thermophysical point of view the surface film of water is envisaged as consisting of a laminar layer through which heat and mass transfer takes place by molecular diffusion, and an intermediate layer in which the rates of diffusion increase from molecular to turbulent scales (Figure 10.1).