Attenuation of rare earth elements in a boreal estuary

Åström, Mats E.; Österholm, Peter; Gustafsson, Jon Petter; Nystrand, Miriam; Peltola, Pasi; Nordmyr, Linda; Boman, Anton

doi:10.1016/j.gca.2012.08.004

Cited by 39 publications

(20 citation statements)

References 83 publications

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“…The loss of REEs from solution observed in earlier laboratory investigations that employed river waters was ascribed to salt-induced coagulation and flocculation of Ferich, organic colloids at low salinity, which scavenged the REEs and other trace metals from solution, and then settled out of suspension (Sholkovitz, 1976(Sholkovitz, , 1993(Sholkovitz, , 1995Boyle et al, 1977Boyle et al, , 1982Sholkovitz and Copland, 1981;Hoyle et al, 1984). Transects through a number of surface estuaries also reveal substantial removal of REEs from solution in the low salinity regions where river water initially encounters seawater, in agreement with the bottle mixing experiments discussed above (e.g., Martin et al, 1976;Goldstein and Jacobsen, 1988a;Sholkovitz and Elderfield, 1988;Elderfield et al, 1990;Sholkovitz, 1993Sholkovitz, , 1995Sholkovitz and Szymczak, 2000;Lawrence and Kamber, 2006;Censi et al, 2007;Åström et al, 2012;Rousseau et al, 2015). Again, the same mechanism of saltinduced coagulation and flocculation of Fe-rich, organic colloids, can explain REE removal from the water column in the low salinity region of these surface water estuaries.…”

Section: Mixing Experimentssupporting

confidence: 77%

Rare earth element behavior during groundwater–seawater mixing along the Kona Coast of Hawaii

Johannesson

Palmore

Fackrell

et al. 2017

Geochimica et Cosmochimica Acta

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Groundwater and seawater samples were collected from nearshore wells and offshore along the Kona Coast of the Big Island of Hawaii to investigate rare earth element (REE) behavior in local subterranean estuaries. Previous investigations showed that submarine groundwater discharge (SGD) is the predominant flux of terrestrial waters to the coastal ocean along the arid Kona Coast of Hawaii. Groundwater and seawater samples were filtered through 0.45 μm and 0.02 μm pore-size filters to evaluate the importance of colloidal and soluble (i.e., truly dissolved ionic species and/or low molecular weight [LMW] colloids) fractions of the REEs in the local subterranean estuaries. Mixing experiments using groundwater collected immediately down gradient from a wastewater treatment facility (WWTF) proximal to the Kaloko-Hanokohau National Historic Park, and more "pristine" groundwater from a well constructed in a lava tube at Kiholo Bay, were mixed with local seawater to study the effect of solution composition (i.e., pH, salinity) on the concentrations and fractionation behavior of the REEs as groundwater mixes with seawater in Kona Coast subterranean estuaries. The mixed waters were also filtered through 0.45 or 0.02 μm filters to ascertain the behavior of colloidal and soluble fractions of the REEs across the salinity gradient in each mixing experiment. Concentrations of the REEs were statistically identical (two-tailed Student ttest, 95% confidence) between the sequentially filtered sample aliquots, indicating that the REEs occur as dissolved ionic species and/or LMW colloids in Kona Coast groundwaters. The mixing experiments revealed that the REEs are released to solution from suspended particles or colloids when Kona Coast groundwater waters mix with local seawater. The order of release that accompanies increasing pH and salinity follows

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Section: Mixing Experimentssupporting

confidence: 77%

Rare earth element behavior during groundwater–seawater mixing along the Kona Coast of Hawaii

Johannesson

Palmore

Fackrell

et al. 2017

Geochimica et Cosmochimica Acta

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“…8) may reflect the removal of the Fe-rich colloids, binding LREE via surface adsorption or Ocean Sci., 10, 107-125, 2014 www.ocean-sci.net/10/107/2014/ incorporation, and the appearance of LMW organic ligands forming strong complexes with HREE. Preferential removal of the light REE was already observed in temperate estuaries (Sholkovitz and Elderfield, 1988;Elderfield et al, 1990) and LREE are known to be removed more efficiently than HREE in small estuaries (Lawrence and Kamber, 2006;Åström et al, 2012). The affinity of light REE for mineral and colloidal surfaces such as HMW organo-ferric colloids, and HREE for soluble organic ligands such as LMW < 1 kDa complexes, is fairly well known both from experimental studies (Bau, 1999) and natural observations in the boreal zone (Pokrovsky et al, 2006).…”

Section: Conservative Versus Non-conservative Behavior Controlled By mentioning

confidence: 90%

Fate of colloids during estuarine mixing in the Arctic

et al. 2014

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Abstract. The estuarine behavior of organic carbon (OC) and trace elements (TE) was studied for the largest European sub-Arctic river, which is the Severnaya Dvina; this river has a deltaic estuary covered in ice during several hydrological seasons: summer (July 2010, 2012) and winter (March 2009) baseflow, and the November–December 2011 ice-free period. Colloidal forms of OC and TE were assessed for three pore size cutoffs (1, 10, and 50 kDa) using an in situ dialysis procedure. Conventionally dissolved (< 0.22 μm) fractions demonstrated clear conservative behavior for Li, B, Na, Mg, K, Ca, Sr, Mo, Rb, Cs, and U during the mixing of freshwater with the White Sea; a significant (up to a factor of 10) concentration increase occurs with increases in salinity. Si and OC also displayed conservative behavior but with a pronounced decrease in concentration seawards. Rather conservative behavior, but with much smaller changes in concentration (variation within ±30%) over a full range of salinities, was observed for Ti, Ni, Cr, As, Co, Cu, Ga, Y, and heavy REE. Strong non-conservative behavior with coagulation/removal at low salinities (< 5‰) was exhibited by Fe, Al, Zr, Hf, and light REE. Finally, certain divalent metals exhibited non-conservative behavior with a concentration gain at low (~ 2–5‰, Ba, Mn) or intermediate (~ 10–15‰, Ba, Zn, Pb, Cd) salinities, which is most likely linked to TE desorption from suspended matter or sediment outflux. The most important result of this study is the elucidation of the behavior of the "truly" dissolved low molecular weight LMW< 1 kDa fraction containing Fe, OC, and a number of insoluble elements. The concentration of the LMW fraction either remains constant or increases its relative contribution to the overall dissolved (< 0.22 μm) pool as the salinity increases. Similarly, the relative proportion of colloidal (1 kDa–0.22 μm) pool for the OC and insoluble TE bound to ferric colloids systematically decreased seaward, with the largest decrease occurring at low (< 5‰) salinities. Overall, the observed decrease in the colloidal fraction may be related to the coagulation of organo-ferric colloids at the beginning of the mixing zone and therefore the replacement of the HMW1 kDa–0.22 μm portion by the LMW< 1 kDa fraction. These patterns are highly reproducible across different sampling seasons, suggesting significant enrichment of the mixing zone by the most labile (and potentially bioavailable) fraction of the OC, Fe and insoluble TE. The size fractionation of the colloidal material during estuarine mixing reflects a number of inorganic and biological processes, the relative contribution of which to element speciation varies depending on the hydrological stage and time of year. In particular, LMW< 1 kDa ligand production in the surface horizons of the mixing zone may be linked to heterotrophic mineralization of allochthonous DOM and/or photodestruction. Given the relatively low concentration of particulate versus dissolved load of most trace elements, desorption from the river suspended material was less pronounced than in other rivers in the world. As a result, the majority of dissolved components exhibited either conservative (OC and related elements such as divalent metals) or non-conservative, coagulation-controlled (Fe, Al, and insoluble TE associated with organo-ferric colloids) behavior. The climate warming at high latitudes is likely to intensify the production of LMW< 1 kDa organic ligands and the associated TE; therefore, the delivery of potentially bioavailable trace metal micronutrients from the land to the ocean may increase.

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“… In this overview of published estuarine dissolved Nd observations 7 9 28 29 30 51 52 53 54 55 all Nd concentrations are normalized to that of the corresponding river endmember. ( a ) estuaries that show a gradual drop in Nd concentrations, ( b ) estuaries that show both an initial drop (removal) followed by a rebound (release) in Nd concentrations, ( c ) scenario illustrating simultaneous fast Nd removal and slow Nd release, ( d ) scenario illustrating simultaneous slow Nd removal and slow Nd release.…”

Section: Figurementioning

confidence: 99%

Rapid neodymium release to marine waters from lithogenic sediments in the Amazon estuary

et al. 2015

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Rare earth element (REE) concentrations and neodymium isotopic composition (ɛNd) are tracers for ocean circulation and biogeochemistry. Although models suggest that REE release from lithogenic sediment in river discharge may dominate all other REE inputs to the oceans, the occurrence, mechanisms and magnitude of such a source are still debated. Here we present the first simultaneous observations of dissolved (<0.45 μm), colloidal and particulate REE and ɛNd in the Amazon estuary. A sharp drop in dissolved REE in the low-salinity zone is driven by coagulation of colloidal matter. At mid-salinities, total dissolved REE levels slightly increase, while ɛNd values are shifted from the dissolved Nd river endmember (−8.9) to values typical of river suspended matter (−10.6). Combining a Nd isotope mass balance with apparent radium isotope ages of estuarine waters suggests a rapid (3 weeks) and globally significant Nd release by dissolution of lithogenic suspended sediments.

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Attenuation of rare earth elements in a boreal estuary

Cited by 39 publications

References 83 publications

Rare earth element behavior during groundwater–seawater mixing along the Kona Coast of Hawaii

Rare earth element behavior during groundwater–seawater mixing along the Kona Coast of Hawaii

Fate of colloids during estuarine mixing in the Arctic

Rapid neodymium release to marine waters from lithogenic sediments in the Amazon estuary

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