title: Molecular characterization of dissolved organic matter (DOM): a critical review.
abstract: Advances in water chemistry in the last decade have improved our knowledge about the genesis, composition, and structure of dissolved organic matter, and its effect on the environment. Improvements in analytical technology, for example Fourier-transform ion cyclotron (FT-ICR) mass spectrometry (MS), homo and hetero-correlated multidimensional nuclear magnetic resonance (NMR) spectroscopy, and excitation emission matrix fluorimetry (EEMF) with parallel factor (PARAFAC) analysis for UV-fluorescence spectroscopy have resulted in these advances. Improved purification methods, for example ultrafiltration and reverse osmosis, have enabled facile desalting and concentration of freshly collected DOM samples, thereby complementing the analytical process. Although its molecular weight (MW) remains undefined, DOM is described as a complex mixture of low-MW substances and larger-MW biomolecules, for example proteins, polysaccharides, and exocellular macromolecules. There is a general consensus that marine DOM originates from terrestrial and marine sources. A combination of diagenetic and microbial processes contributes to its origin, resulting in refractory organic matter which acts as carbon sink in the ocean. Ocean DOM is derived partially from humified products of plants decay dissolved in fresh water and transported to the ocean, and partially from proteinaceous and polysaccharide material from phytoplankton metabolism, which undergoes in-situ microbial processes, becoming refractory. Some of the DOM interacts with radiation and is, therefore, defined as chromophoric DOM (CDOM). CDOM is classified as terrestrial, marine, anthropogenic, or mixed, depending on its origin. Terrestrial CDOM reaches the oceans via estuaries, whereas autochthonous CDOM is formed in sea water by microbial activity; anthropogenic CDOM is a result of human activity. CDOM also affects the quality of water, by shielding it from solar radiation, and constitutes a carbon sink pool. Evidence in support of the hypothesis that part of marine DOM is of terrestrial origin, being the result of a long-term carbon sedimentation, has been obtained from several studies discussed herein.
authors.affiliation: Centro Interdipartimentale di Risonanza Magnetica Nucleare per l'Ambiente, l'Agroalimentare e i Nuovi Materiali (CERMANU), Università degli Studi di Napoli Federico II, via Università 100, 80055 Portici, Italy. antonio.nebbioso@unina.it
authors.forename: Antonio
authors.initials: A
authors.lastname: Nebbioso
authors.forename: Alessandro
authors.initials: A
authors.lastname: Piccolo
mesh_terms: D000336:Aerosols; D002244:Carbon / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry; D005782:Gels; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D013058:Mass Spectrometry / Q000379:methods; D008956:Models, Chemical; D009792:Oceans and Seas; D010316:Particle Size; D011134:Polysaccharides / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D014867:Water / Q000737:chemistry / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D014876:Water Pollution; D014881:Water Supply
chemical_list: D000336:Aerosols; D005782:Gels; D011134:Polysaccharides; D014874:Water Pollutants, Chemical; D014867:Water; D002244:Carbon