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

Abstract

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. 10.1016Environment, 434. 171-185. 10. /j.scitotenv.2011 Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. An integrated assessment is made of the role of riverine colloids in macronutrient (nitrogen, 21 phosphorus and carbon), metal and trace element partitioning and transport, for five rivers in the 22Ribble and Wyre catchments in north-western England, under baseflow/near-baseflow 23 conditions. Cross-flow ultrafiltration was used to separate colloidal (<0.45 >1kDa) and truly 24 dissolved (<1kDa) fractions from river water. Clear patterns were observed, along the upland-25 lowland land use continuum, in the partitioning and transport of macronutrients and metals 26 between the colloidal, truly dissolved and acid-available particulate (>0.45µm, suspended) 27 fractions. Of these operationally-defined fractions measured, colloids were generally more 28 important for both macronutrient and metal transport in the upland than in the lowland rivers. 29The results suggest that organic moieties in truly dissolved form from sewage effluent may have 30 a greater capacity to chelate metals. Organic-rich colloids in the upland moorlands and metal 31 oxide colloidal precipitates in the industrial rivers had a higher capacity for binding metals than 32 2 the colloidal fractions in the urban and agricultural lowland rivers. Aggregation of these colloids 1 may provide an important mechanism for formation of larger suspended particulates, accounting 2 for a much higher degree of metal enrichment in the acid-available particulate fractions of the 3 upland moorland and lowland industrial rivers than in the lowland agricultural and urban rivers. 4This mechanism of transfer of contaminants to larger aggregates via colloidal intermediates, 5 known as 'colloidal pumping' may also provide a mechanism for particulate P formation and the 6 high proportion of P being transported in the particulate fraction in the uplands. The cross-flow 7 ultrafiltration data also allowed refinement of partition coefficients, by accounting for colloids 8 within the solids phase and replacing the filtered (<0.45µm) fraction with the truly dissolved 9 (<1kDa) concentrations. These provided a clearer description of the controls on metal and P 10 partitioning along the upland-lowland continuum. 11 12

Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers

“…Overall, the percentages reflected a substantial contribution of the NNP and fine colloidal fractions within the operationally defined dissolved elements Fe, P, Al, org C, and Mn (in descending order). Previous research on the significance of colloid‐bound elements within the operationally defined dissolved fraction also indicated maximum Fe binding in fine colloidal form between 80 and 100% with averages between 50 and 90% (Hill & Aplin, ; Jarvie et al, ; Martin et al, ), for organic C between 40 and 80% with averages between 20 and 60% (Jarvie et al, ; Martin et al, ; Wen et al, ), and for Al around 40 to 50% with averages around 45 to 55% (Hill & Aplin, ; Jarvie et al, ). Hill and Aplin () determined that the fine colloidal fraction accounted for up to 50% of Mn (average 23%) and up to 30% of Ca (average 20%) but only up to 10% of Si (average 0%).…”

“…Colloids smaller than 0.45 μm (≡450 nm) are in the present study defined as fine colloids. In natural aqueous phases up to 100% of the total elemental concentrations of metals, and also of specific nutrients like P, can be associated with such particles (Gottselig et al, ; Hart et al, ; Hill & Aplin, ; Jarvie et al, ; Martin, Dai, & Cauwet, ). Hence, identifying NNP and colloids in water samples is necessary to better understand the cycling and transport of elements in catchments and to determine their biological availability.…”

Nutrient dynamics, transfer and retention along the aquatic continuum from land to ocean: towards integration of ecological and biogeochemical models

“…Sorbed species like phosphate can move through the particle-size spectrum on a piggy-back ride as colloids according to a process called colloidal pumping (Stordal et al, 1996;Wen et al, 1997). The settling properties of phosphate alter accordingly, and this phenomenon is therefore more important in upstream than in lowland rivers (Jarvie et al, 2012).…”

Solid-Solution Metal Partitioning for the Upper Mero River Basin (NW Spain)

“…In the Mero River, the seasons of high Q also corresponded with the seasons of high SS. The decrease of K D when SS increase is frequently attributed to the particle concentration effect, which has been attributed to systematic variation of the quantity of colloid with SS when 0.45-µm filters were used (Veselý et al 2001;Jarvie et al 2012).…”

“…Trace metal mobility in large, urban, or highly polluted catchments has been well studied (Gundersen and Steinnes 2003;Ollivier, Radakovitch, and Hamelin 2011); however, headwater catchments and rural areas have received less attention, even though some rural rivers are also affected by anthropogenic activities such as agricultural runoff, manure application, or wastewater discharge (Miller, Foster, and Majedi 2003;Jarvie et al 2012).…”