title: Relevance of peat-draining rivers for the riverine input of dissolved iron into the ocean.
abstract: Peat bogs have the ability to produce strong chelate ligands (humic and fulvic acids) which enhance the weathering rates of iron-silicate minerals and greatly increase the solubility of the essential trace metal iron in river water. Fluvial networks link peat bogs with the ocean, and thus terrestrial-derived fulvic-iron complexes fuel the ocean's biological productivity and biological carbon pump, but understanding this role is constrained by inconsistent observations regarding the behaviour of riverine iron in the estuarine mixing zone, where precipitation reactions remove iron from the water column. We applied a characterization of the colloidal iron carriers in peatland-draining rivers in North Scotland, using field-flow fractionation (FFF), in combination with end-member mixing experiments of river water sampled near the river mouth and coastal seawater using a (59)Fe radiotracer method. According to our results, the investigated river contributed "truly dissolved" Fe concentrations of about 3300nmolL(-1) to the ocean which is nearly two orders of magnitude higher than the dissolved iron contribution of the "average world" river ( approximately 40nmolL(-1)). Thus we conclude that peatland-draining rivers are important sources of dissolved iron to the ocean margins. We propose highly electrostatic and sterical stabilized iron-organic matter complexes in the size range of <2kDa to be responsible for iron transport across the estuarine mixing zone.
authors.affiliation: Institute of Inorganic Chemistry, University of Vienna, Währingerstrasse 42, 1090 Vienna, Austria. regina.krachler@univie.ac.at
authors.forename: Regina
authors.initials: R
authors.lastname: Krachler
authors.forename: Rudolf F
authors.initials: RF
authors.lastname: Krachler
authors.forename: Frank
authors.initials: F
authors.lastname: von der Kammer
authors.forename: Altan
authors.initials: A
authors.lastname: Süphandag
authors.forename: Franz
authors.initials: F
authors.lastname: Jirsa
authors.forename: Shahram
authors.initials: S
authors.lastname: Ayromlou
authors.forename: Thilo
authors.initials: T
authors.lastname: Hofmann
authors.forename: Bernhard K
authors.initials: BK
authors.lastname: Keppler
mesh_terms: D001578:Benzopyrans / Q000032:analysis; D004784:Environmental Monitoring; D006812:Humic Substances / Q000032:analysis; D058085:Iron Compounds / Q000032:analysis*; D007504:Iron Radioisotopes; D009792:Oceans and Seas; D045483:Rivers; D012623:Seawater / Q000737:chemistry*; D012987:Soil; D012995:Solubility; D014872:Water Movements; D053833:Wetlands
chemical_list: D001578:Benzopyrans; D006812:Humic Substances; D058085:Iron Compounds; D007504:Iron Radioisotopes; D012987:Soil; C005023:fulvic acid