Diffusion of contaminants in the ocean is a major factor forming fields of both natural and man-mad substances introduced into the water medium. Without proper understanding of the laws of contaminant diffusion in the ocean it is impossible to choose the correct methods of calculating the transport of biogenic elements, dissolved gases and pollutants. Diffusion processes in the ocean are very com­ plicated because of the larger number of factors influencing the distribution of a substance. In this regard, progress in studying the regularities of contami­ nant diffusion in the ocean can only be reached when combining theoretical and experimental methods. Both theoretical and experimental studies on the diffusion of contaminants in the ocean have been devoted much attention in many countries of the world. The results are being published in a larger number of journals and collected works; however, until now there have been no comprehensive publications on the diffu­ sion of contaminants in the ocean. This monograph summarizes the results obtained on the problem by the author and other researchers. The presentation of theoretical results is combined with the data obtained in diffusion experiments with artificial tracers. Also given are practical recommendations on how to compute the behavior of contaminants in various hydrometeorological conditions. Several parts of the monograph are based on the studies I have made in colla­ boration with A.N. Gerentsway, V.1. Zats, G.S. Karabashev, S.S. Muravyev, A.

1 Element of Contaminant-Diffusion Theory.- 1.1 Molecular Diffusion.- 1.2 Contaminant Diffusion in Turbulent Flows.- 1.3 Turbulent Diffusion Coefficients.- 1.4 Dependence of Transport Coefficients upon the Determining Factors.- 1.5 Diffusion Models with Transport Coefficients Depending onTime and the Phenomenon Scale.- 1.6 Contaminant Diffusion in a Non-Homogeneous and Non-Stationary Mean Current Velocity Field.- 1.7 Diffusion of Discrete Particles in the Turbulent Flow.- 1.8 Concentration Fluctuations for the Diffusion Contaminant.- 2. Diffusion of Contaminants From Localized Sources In the Ocean.- 2.1 Experimental Methods of Studying the Diffusion of Contaminants in the Ocean.- 2.2 Diffusion from Instantaneous Point Sources.- 2.3 Diffusion from Continuous Point Sources.- 2.4 Diffusion of Discrete Particles in the Ocean.- 3. Diffusion of Contaminants From Distributed Sources In the Ocean.- 3.1 Diffusion of Contaminants Fallen Out of the Atmosphere.- 3.2 Diffusion of Biogenic Elements, Oxygen and Carbon Dioxide in the Ocean.- 3.3 Some Aspects of Oil-Spot Diffusion.- 3.4 Diffusion of Contaminant from Distributed Sources in the Ocean with Vertical Fine-Structure.- 4. Practical Methods of Calculating the Contaminant Diffusion In the Ocean.- 4.1 Numerical Studies of Contaminant Concentration Carried Out Using the Semi-Empirical Diffusion Equation.- 4.2 The Walking-Particle Method.- 4.3 Estimations of Contaminant-Concentration Fields fromDischarge Facilities.- References.