Advanced

Characterization of Iron and Organic Carbon Colloids in Boreal Rivers and Their Fate at High Salinity

Herzog, Simon David LU ; Gentile, Luigi LU ; Olsson, Ulf LU ; Persson, Per LU and Kritzberg, Emma Sofia LU (2020) In Journal of Geophysical Research - Biogeosciences 125(4).
Abstract

Riverine colloids are important carriers of macronutrients, trace metals, and pollutants into marine waters. The aim of the current study was to extend the understanding of iron (Fe) and organic carbon (OC) colloids in boreal rivers and their fate at higher salinities. X-ray absorbance spectroscopy (XAS) and dynamic light scattering (DLS) were combined to explore Fe speciation and colloidal characteristics such as size and surface charge and how these are affected at increasing salinity. XAS confirmed the presence of two Fe phases in the river waters—Fe-organic matter (OM) complexes and Fe(oxy)hydroxides. From DLS measurements on filtered and unfiltered samples, three particle size distributions were identified. The smallest particles... (More)

Riverine colloids are important carriers of macronutrients, trace metals, and pollutants into marine waters. The aim of the current study was to extend the understanding of iron (Fe) and organic carbon (OC) colloids in boreal rivers and their fate at higher salinities. X-ray absorbance spectroscopy (XAS) and dynamic light scattering (DLS) were combined to explore Fe speciation and colloidal characteristics such as size and surface charge and how these are affected at increasing salinity. XAS confirmed the presence of two Fe phases in the river waters—Fe-organic matter (OM) complexes and Fe(oxy)hydroxides. From DLS measurements on filtered and unfiltered samples, three particle size distributions were identified. The smallest particles (10–40 nm) were positively charged and suggested to consist of essentially bare Fe(oxy)hydroxide nanoparticles. The largest particles (300–900 nm) were dominated by Fe(oxy)hydroxides associated with chromophoric molecular matter. An intermediate size distribution (100–200 nm) with a negative surface charge was presumably dominated by OM and containing Fe-OM complexes. Increasing the salinity resulted in a removal of the smallest distribution. Unexpectedly, both the intermediate and largest size distributions were still detected at high salinity. The collective results suggest that Fe(oxy)hydroxides and Fe-OM complexes are both found across the wide size range studied and that colloidal size does not necessarily reflect either Fe speciation or stability toward salinity-induced aggregation. The findings further demonstrate that also particles beyond the typically studied <0.45-μm size range should be considered to fully understand the riverine transport and fate of macronutrients, trace metals, and pollutants.

(Less)
Please use this url to cite or link to this publication:
author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
DLS, Fe speciation, natural colloids, size distribution, XAS
in
Journal of Geophysical Research - Biogeosciences
volume
125
issue
4
article number
e2019JG005517
publisher
Wiley
external identifiers
  • scopus:85091047073
ISSN
2169-8953
DOI
10.1029/2019JG005517
language
English
LU publication?
yes
id
e6c74fdf-be37-45ee-88ee-be37f1a70d10
date added to LUP
2020-10-06 14:42:18
date last changed
2020-10-08 14:53:24
@article{e6c74fdf-be37-45ee-88ee-be37f1a70d10,
  abstract     = {<p>Riverine colloids are important carriers of macronutrients, trace metals, and pollutants into marine waters. The aim of the current study was to extend the understanding of iron (Fe) and organic carbon (OC) colloids in boreal rivers and their fate at higher salinities. X-ray absorbance spectroscopy (XAS) and dynamic light scattering (DLS) were combined to explore Fe speciation and colloidal characteristics such as size and surface charge and how these are affected at increasing salinity. XAS confirmed the presence of two Fe phases in the river waters—Fe-organic matter (OM) complexes and Fe(oxy)hydroxides. From DLS measurements on filtered and unfiltered samples, three particle size distributions were identified. The smallest particles (10–40 nm) were positively charged and suggested to consist of essentially bare Fe(oxy)hydroxide nanoparticles. The largest particles (300–900 nm) were dominated by Fe(oxy)hydroxides associated with chromophoric molecular matter. An intermediate size distribution (100–200 nm) with a negative surface charge was presumably dominated by OM and containing Fe-OM complexes. Increasing the salinity resulted in a removal of the smallest distribution. Unexpectedly, both the intermediate and largest size distributions were still detected at high salinity. The collective results suggest that Fe(oxy)hydroxides and Fe-OM complexes are both found across the wide size range studied and that colloidal size does not necessarily reflect either Fe speciation or stability toward salinity-induced aggregation. The findings further demonstrate that also particles beyond the typically studied &lt;0.45-μm size range should be considered to fully understand the riverine transport and fate of macronutrients, trace metals, and pollutants.</p>},
  author       = {Herzog, Simon David and Gentile, Luigi and Olsson, Ulf and Persson, Per and Kritzberg, Emma Sofia},
  issn         = {2169-8953},
  language     = {eng},
  month        = {04},
  number       = {4},
  publisher    = {Wiley},
  series       = {Journal of Geophysical Research - Biogeosciences},
  title        = {Characterization of Iron and Organic Carbon Colloids in Boreal Rivers and Their Fate at High Salinity},
  url          = {http://dx.doi.org/10.1029/2019JG005517},
  doi          = {10.1029/2019JG005517},
  volume       = {125},
  year         = {2020},
}