title: Composition of dissolved organic nitrogen in rivers associated with wetlands.
abstract: As basic information for assessing reactivity and functionality of wetland-associated dissolved organic matter (DOM) based on their composition and structural properties, chemical characteristics of N in ultrafiltered DOM (UDON; >1 kD) isolated from wetland-associated rivers in three climates (cool-temperate, Hokkaido, Japan; sub-tropical, Florida, USA; tropical, Sarawak, Malaysia) were investigated. The UDON was isolated during dry and wet seasons, or during spring, summer, and autumn. The proportion of UDON present as humic substances, which was estimated as the DAX-8 adsorbed fraction, ranged from 47 to 91%, with larger values in the Sarawak than at the other sites. The yield of hydrolyzable amino acid N ranged 1.24 to 7.01 mg g(-1), which correlated positively to the total N content of UDOM and tended to be larger in the order of Florida>Hokkaido>Sarawak samples. X-ray photoelectron N1s spectra of UDON showed a strong negative correlation between the relative abundances of amide/peptide N and primary amine N. The relative abundances of amide/peptide N and primary amine N in the Sarawak samples were smaller (70-76%) and larger (20-23%) respectively compared to those (80-88% and 4-9%) in the Florida and Hokkaido samples. Assuming terminal amino groups and amide N of peptides as major constituents of primary amine N and amide/peptide N, respectively, the average molecular weight of peptides was smaller in the Sarawak samples than that in the Florida and Hokkaido samples. Seasonal variations in UDON composition were scarce in the Sarawak and Florida samples, whereas the distribution of humic substance-N and nonhumic substance-N and compositions of amino acids and N functional groups showed a clear seasonality in the Hokkaido samples. While aromatic N increased from spring to autumn, contributions from fresh proteinaceous materials were also enhanced during autumn, resulting in the highest N content of UDOM for this season.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan. Electronic address: akiraw@agr.nagoya-u.ac.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Watanabe
authors.affiliation: Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Tsutsuki
authors.affiliation: Graduate School of Science and Engineering, Saitama University, Sakura, Saitama 338-8570, Japan.
authors.forename: Yudzuru
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: School of Veterinary Medicine, Kitasato University, Towada, Aomori 034-8628, Japan.
authors.forename: Nagamitsu
authors.initials: N
authors.lastname: Maie
authors.affiliation: Tropical Peat Research Laboratory Unit, Chief Minister's Department, Jalan Badruddin 93400, Kuching, Sarawak, Malaysia.
authors.forename: Lulie
authors.initials: L
authors.lastname: Melling
authors.affiliation: Southeast Environmental Research Center, Florida International University, 3000 NE 151 Str., Marine Sciences Building, North Miami, FL 33181, USA; Department of Chemistry & Biochemistry, Florida International University, 3000 NE 151 Str., Marine Sciences Building, North Miami, FL 33181, USA.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Jaffé
mesh_terms: D004784:Environmental Monitoring; D007564:Japan; D009584:Nitrogen / Q000032:analysis*; D045483:Rivers / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D053833:Wetlands
chemical_list: D014874:Water Pollutants, Chemical; D009584:Nitrogen
keywords: Amino acids; DON; Humic substances; Wetlands; XPS