『Abstract
Variations in the physico-chemical speciation of the rare earth
elements (REE) have been investigated in a subarctic boreal river
during an intense spring flood event using prefiltered (<100μm)
samples, cross-flow (ultra)filtration (CFF), flow field-flow fractionation
(FlFFF), and diffusive gradients in thin films (DGT). This combination
of techniques has provided new information regarding the release
and transport of the REE in river water. The colloidal material
can be described in terms of two fractions dominated by carbon
and iron, respectively. These two fractions, termed colloidal
carrier phases, showed significant temporal changes in concentration
and size distribution. Before the spring flood, colloidal carbon
concentrations were low, the colloids being dominated by relatively
large iron colloids. Colloidal concentrations increased sharply
during the spring flood, with smaller carbon colloids dominating.
Following the spring flood, colloidal concentrations decreased
again, smaller carbon colloids still dominating. The REE are transported
mainly in the particulate and colloidal phase. Before the spring
flood, the REE composition of all measured fractions was similar
to local till. During the spring flood, the REE concentrations
in the colloidal and particulate fractions increased. The increase
was most marked for the lighter REE, which therefore showed a
strong enrichment when normalized to local till. Following the
spring flood, the REE concentrations decreased again and reverted
to a distribution similar to local till. These changes in the
concentration and distributions of carbon iron and REE are interpreted
in terms of changing hydrological flow paths in soil and bedrock
which occur during the spring flood.』
1. Introduction
2. Methods
2.1. Sampling area
2.2. Water sampling
2.3. DGT sampling
2.4. CFF
2.5. FlFFF-ICP-MS
2.6. TOC and fluorescence
3. Results and discussion
3.1. Size fractions and temporal concentration variations
3.2. Normalized REE patterns
4. Discussions
Acknowledgments
References