Role of riverine colloids in macronutrient and metal partitioning and transport, along an upland–lowland land-use continuum, under low-flow conditions

Jarvie, H.P.; Neal, C.; Rowland, A.P.; Neal, M.; Morris, P.N.; Lead, J.R.; Lawlor, A.J.; Woods, C.; Vincent, C.; Guyatt, H.; Hockenhull, K.. 2012 Role of riverine colloids in macronutrient and metal partitioning and transport, along an upland–lowland land-use continuum, under low-flow conditions. Science of the Total Environment, 434. 171-185. 10.1016/j.scitotenv.2011.11.061

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An assessment is made of the role of riverine colloids in macronutrient (nitrogen, phosphorus and carbon), metal and trace element partitioning and transport, for five rivers in the Ribble and Wyre catchments in north-western England, under baseflow/near-baseflow conditions. Cross-flow ultrafiltration was used to separate colloidal (b0.45 μm >1 kDa) and truly dissolved (b1 kDa) fractions from river water. Clear patterns were observed, along the upland–lowland land use continuum, in the partitioning and transport of macronutrients and metals between the colloidal, truly dissolved and acid-available particulate (>0.45 μm, suspended) fractions. Of these operationally-defined fractions measured, colloids were generally more important for both macronutrient and metal transport in the upland than in the lowland rivers. The results suggest that organic moieties in truly dissolved form from sewage effluent may have a greater capacity to chelate metals. Organic-rich colloids in the upland moorlands and metal oxide colloidal precipitates in the industrial rivers had a higher capacity for binding metals than the colloidal fractions in the urban and agricultural lowland rivers. Aggregation of these colloids may provide an important mechanism for formation of larger suspended particulates, accounting for a higher degree of metal enrichment in the acid-available particulate fractions of the upland moorland and lowland industrial rivers, than in the lowland agricultural and urban rivers. This mechanism of transfer of contaminants to larger aggregates via colloidal intermediates, known as ‘colloidal pumping’ may also provide a mechanism for particulate P formation and the high proportion of P being transported in the particulate fraction in the uplands. The cross-flow ultrafiltration data also allowed refinement of partition coefficients, by accounting for colloids within the solids phase and replacing the filtered (b0.45 μm) fraction with the truly dissolved (b1 kDa) concentrations. These provided a clearer description of the controls on metal and P partitioning along the upland-lowland continuum.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.scitotenv.2011.11.061
Programmes: CEH Topics & Objectives 2009 onwards > Water
CEH Sections: Acreman
ISSN: 0048-9697
Additional Information. Not used in RCUK Gateway to Research.: NOTICE: this is the author’s version of a work that was accepted for publication in Science of the Total Environment. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Science of the Total Environment, 434. 171-185. 10.1016/j.scitotenv.2011.11.061
Additional Keywords: colloid, cross-flow ultrafiltration, phosphorus, nitrogen, carbon, nanoparticle
Date made live: 04 Oct 2012 08:14

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