Some 90 years ago, the first information on the occurrence of dissolved organic matter in sea water was published. For 50 years after that reve­ lation, little progress was made in identifying these dissolved "yellow substances." In the 1950s and 1960s, a few chemical oceanographers identified some specific dissolved organic compounds, but few of these pioneers fully appreciated their significance in terms of biological inter­ actions, metal chelation, or interactions with sedimentary material. When Mohammed Rashid began his work on marine humic compounds in the mid-1960s, he was one of only five scientists who had specifically designed their studies toward understanding the nature of these complex materials. Over the next decade, Dr. Rashid directed his research toward characterization of humic and fulvic compounds in the marine environ­ ment, the influence of humic substances on the growth of marine phy­ toplankton, the role of organic matter in complexing metals in sea water and marine sediments, the interaction between humic substances and clay minerals in marine environments, and the influence of organic matter on the geotechnical properties of marine sediments. As if the many papers produced from these scientific investigations were not sufficient, Dr.

Inhaltsangabe1 Origin and Distribution of Organic Compounds in the Marine Environment.- Inventory of Organic Carbon.- Geochemical Significance of Carbon-Containing Compounds.- Evolution of Life and Development of Organic Matter.- Beginning of Life on Earth.- Primitive Organisms and their Evolution.- Higher Land Plants and Animals.- Genesis and Survival of Organic Compounds During Geological Time.- Distribution of Organic Matter in Oceans and on Land.- Marine Primary Productivity and Factors Governing Productivity.- Global Marine Primary Productivity.- Terrestrial Productivity and Its Impact on Oceans.- Nature and Fate of Organic Matter.- Transformations of Organic Matter in the Water Column.- Origin, Concentrations and Nature of DOM and POM.- Aggregation, Sedimentation, and Distribution of Organic Matter.- Factors Affecting the Distribution of Organic Matter in Sediments.- Concentration of Organic Carbon in Surficial Sediments.- Summary.- 2 Humifícation-A Major Biogeochemical Phenomenon.- Nature of Microbial Population.- Bacteria.- Fungi.- Actinomycetes.- Chemical Composition of Organisms.- Some Major Cellular Constituents and Products of their Microbial Degradation.- Proteins and Related Compounds and their Microbial Disintegration.- Carbohydrates, their Related Compounds and their Microbial Decomposition.- Lipids and Related Compounds.- Lignins and Products of their Degradation.- Formation and Transformations of Phenolic Compounds.- Formation of Humus.- Reactions of Phenolic Compounds with Nitrogenous Substances.- Reactions of Amino Acids with Sugars.- Products of Humification.- Factors Influencing Humification.- Distribution of Humic Compounds in the Marine Environment.- Concentrations of Humic Compounds in the Water Column.- Concentrations of Humic Compounds in the Sedimentary Column.- Summary.- 3 Physico-chemical Characteristics of Marine Humic Compounds.- Major Components of Humic Substances.- Major Phenolic and Aromatic Compounds.- Major Aliphatic Constituents.- Structural Configuration.- Stability of Humic Compounds in Geological Times.- Chemical Composition and Characterization.- Elemental Analysis.- Ratios of Different Elements and their Significance.- Isotopic Composition and the Source of Organic Matter.- Functional Groups.- Factors Affecting the Distribution of Functional Groups.- Electro-chemistry of Humic Molecules.- Aliphaticity versus Aromaticity.- Physical Properties.- Some Striking Differences and Similarities in the Physico-chemical Characteristics of Marine and Terrestrial Humic Compounds.- Summary.- 4 Organo-metal Reactions and their Geochemical Significance.- Humus as a Natural Absorbent.- Geochemical Scale of Metal Absorption.- Enrichment of Trace, Transition, and Rare Metals in Humic-Rich Media.- Physico-chemical Properties of Humic Compounds in Relation to Organo-metal Reactions.- Functional Groups and their Role in Organo-metal Interactions.- Molecular Weight Distribution and Organo-metal Reactions.- Surface Area.- Degree of Humification, Nature, and Source of Humic Compounds.- Environmental Factors Affecting Organic Reactions.- Mechanisms of Organo-metal Interactions.- Surface or Physical Adsorption.- Cation Exchange Reactions.- Chelation and Complexing Reactions.- Bonding Strength.- Factors Affecting Bonding Strength.- Measurement of Bonding Strength.- Implications of Organo-metal Reactions.- Geochemical Significance and Sedimentary Base Metal Accumulations.- Economic Implications and Formation of Ores.- Environmental Significance of Organo-metal Reactions.- Ecological Implications.- Research Proposals.- Summary.- 5 Reactions of Humic Compounds with Sedimentary Minerals.- Clay Minerals and their Types.- Structure and Classification of Clay Minerals.- Electrical Charges.- Clay Minerals of Marine Sediments.- Other Minerals.- Physico-chemical Properties of Humic Compounds and Organo-clay Complexes.- Functional Groups.- Molecular Weight of Humic Compounds.- Mechanisms of Organo-clay Interactions.- Chemical Bondings