Estuarine organic matter composition as probed by direct temperature-resolved mass spectrometry and traditional geochemical techniques

Estuarine modification of terrestrial and riverine/estuarine organic matter may strongly affect the eventual preservation of reduced carbon in world o ceans, and is also important in nutrient and contaminant cycling. In this s tudy multiple size classes of organic matter (including particles and disso lved fractions, POM and DOM) from, a transect down the Delaware River/Bay s ystem were collected and analyzed. Variations in chemical characteristics w ere identified using direct temperature-resolved mass spectrometry (DT-MS) and wet chemical techniques coupled with discriminant analysis and canonica l correlations analysis. These comparative measures illustrate the compleme ntary nature of traditional versus more recent mass spectrometry approaches . Within the estuary system, organic matter size class, rather than sample lo cation, is found to be the major source of molecular-level variation. POM i s enriched in proteins, nucleic acids, fatty acids, chlorophyll, and sterol s, whereas DOM is enriched in aminosugar, furfural, and alkylphenol moietie s. In positive ammonia chemical ionization DT-MS studies, which focus on th e sugar components in POM and DOM, riverine very high molecular weight DOM (> 30 kDa, <0.2 mum) is found to be enriched in deoxysugars and methylsugar s compared to all other estuarine and coastal samples. Copyright (C) 2001 E lsevier Science Ltd.