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  • 1.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Geochemistry of tungsten and molybdenum during freshwater transport and estuarine mixing2018In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 93, p. 36-48Article in journal (Refereed)
    Abstract [en]

    The geochemistry of tungsten (W) in the environment is poorly studied. Tungsten usually occurs in low concentrations in natural waters and is not very mobile. For this study, we analyzed W together with molybdenum (Mo) in the dissolved and particulate fractions of two boreal estuaries during different seasons. Additionally, we sampled first-order streams that drain different landscape types and the receiving northern Baltic Sea. Furthermore, surface sediment from the estuaries was analyzed to obtain a comprehensive overview of the distribution of W and Mo in a boreal environment.

    Both elements showed different distribution patterns during different seasons. While they decreased in the dissolved fraction during spring discharge, in winter, their concentrations were elevated. Molybdenum exhibited non-conservative behavior along the salinity gradient in winter, which was probably caused by its release from underlying sediments. In the particulate fraction, we found opposite behaviors for Mo and W, with higher particulate W and lower particulate Mo during spring discharge.

    Molybdenum and W underwent fractionation from land to sea, indicating the different mobilities of these oxyanions. The Mo/W ratio in the dissolved fraction was mainly determined by the Mo concentration, as the W concentration varied only in a narrow range from first-order streams to the Bothnian Bay. In the particulate fraction, the Mo/W ratio appeared to be affected by scavenging processes and showed only small variations.

  • 2.
    Bauer, Susanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    The geochemistry of tungsten in the Baltic Sea2015Conference paper (Other academic)
  • 3.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Iron isotopes in aquatic systems2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The cycling of iron (Fe) is a key component for understanding water quality and biogeochemical processes. It serves as mediator during biotic and abiotic processes, as electron acceptor during the degradation of organic matter, as surface for trace element and organic matter adsorption, and is necessary for primary production processes. Since the beginning of Fe isotope studies, researchers focussed on the ratios in soils, rivers and oceans in various environments. The aim of this study was to characterize the Fe isotope ratios from the source (e.g. soils), along the river course, through the estuaries and into the adjacent sea within the boreal landscape. Therefore, seasonal sampling of water from Swedish headwater streams (2016/2017), rivers (2016), estuaries (2013/2014) and the Baltic Sea (2013/2014) were conducted, with the purpose to better understand the role and fate of riverine Fe export. Fe is transported in two main phases from the headwater streams into the oceans: organic Fe complexes and Fe(oxy)hydroxide. It has been proposed that these Fe phases varies in response to seasonal differences in hydrology.

                          This thesis includes the first Fe isotope dataset describing seasonal variations of headwater streams on a regional scale. In the headwater streams positive and negative Fe isotopes ratios can be used to distinguish between different Fe phases. Furthermore, Fe isotope ratios in headwater streams could verify regional drought periods and the subsequent rewetting of the subsurface soils.

    Within the rivers and estuaries, we found positive Fe isotopes in the dissolved phase (< 0.22µm) and negative Fe isotopes (> 0.22µm) in the particulate phase during high discharge. The correlation between different chemical parameters, Fe and DOC showed that the Fe isotope composition during spring flood is evolving in the upper soil layers of headwater streams. Therefore, the lighter Fe isotope signal is correlated to the organic-rich soil layers of the riparian zones in forested catchments. During baseflow, particulate Fe has a positive Fe isotope signal. This shows that the Fe has different origin throughout the season within one catchment.

    Salt-induced flocculation in the estuaries and under experimental conditions, is removing about 80 % of the dissolved and particulate Fe. Newly formed colloids and particles aggregate and sediment due to small changes in salinity. This major flocculation at low salinities might cause an underestimation of riverine Fe flux. Interestingly, salinity-induced aggregation experiments revealed that Fe(oxy)hydroxide, which dominated aggregates, displayed lower Fe isotope ratios than in the river samples Fe, while organic Fe complexes in the suspension had higher Fe isotope values. The seasonal variability in Fe isotope values could not be simply linked to Fe phases but was probably also influenced by variation in source areas of Fe and processes along the flow-path that alter both Fe phases and isotopic composition.

    Within the estuarine mixing zone, no Fe isotope fractionation was observed. The Fe isotope signal is constant over time and space, which excludes fractionation processes for example by oxidation. The Fe isotope signal within the Bothnian Bay was positive showing that different surface properties of Fe-OC and Fe(oxy)hydroxide aggregates lead to the flocculation of negative Fe aggregates.

  • 4.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Origin of Iron Isotope Signatures in Boreal Estuaries2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The geochemistry of iron (Fe) during freshwater transport and estuarine mixing has been investigated. Espescially the changes in the Fe-isotope signature have been studied. The fate of Fe-isotopes during estuarine mixing has been poorly studied. Sampling was performed in Kalix River, Kalix and Råne estuary, and in the open Bothnian Bay, Northern Baltic Sea. Water samples were filtered with 0.22 μm membrane filters. Both particulate (> 0.22 μm) and colloidal fractions (< 0.22 μm) were analyzed. Iron particles and colloids, with a negative Fe-isotope signature, are formed during spring flood in forested catchments. These Fe complexes are associated with organic carbon (OC), and probably have a mixed oxidation state (Fe(II,III)-OC). Negative colloids are labile and flocculate and/or oxidize during riverine transport. Therefore, no negative colloids are detectable in the estuaries of the open Bothnian Bay. Within the estuaries two types of ˜56Fe signatures were measured: negative particles and positive colloids. The open Bothnian Bay shows a third distinct group of positive particles. This group mirrors the rapid removal of Fe colloids and particles at low salinities. Most of the Fe has been removed from surface water at salinities below 1.0 psu. Data in this study show that the Fe-isotopes can be used to trace the origin and cycling of iron particles and colloids in the boreal landscape.

  • 5.
    Conrad, Sarah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Enrichment of heavy iron isotopes in suspended matter during estuarine mixing2015Conference paper (Other academic)
  • 6.
    Conrad, Sarah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Fe-OC aggregates from headwaters to the estuary: The story of Fe-isotopes2016Conference paper (Refereed)
  • 7.
    Conrad, Sarah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Iron isotope signatures in low salinity estuaries, northern Baltic Sea2014Conference paper (Refereed)
  • 8.
    Conrad, Sarah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Gelting, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Nordblad, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Engström, Emma
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. ALS Laboratory Group, ALS Scandinavia AB, Luleå, Sweden .
    Rodushkin, Ilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. ALS Laboratory Group, ALS Scandinavia AB, Luleå, Sweden .
    Andersson, Per S.
    Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden.
    Porcelli, Don
    Department of Earth Sciences, Oxford University, Oxford, UK.
    Gustafsson, Örjan
    Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden.
    Semiletov, Igor
    International Arctic Research Center (IARC), University of Alaska, Fairbanks, AK, USA. Pacific Oceanological Institute (POI), Far Eastern Branch of the Russian Academy of Sciences (FEBRAS), Vladivostok, Russia. Tomsk National Research Politechnical University, Arctic Seas Carbon International Research Laboratory, Tomsk, Russia.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Distribution of Fe isotopes in particles and colloids in the salinity gradient along the Lena River plume, Laptev Sea2019In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 16, no 6, p. 1305-1319Article in journal (Refereed)
    Abstract [en]

     Riverine Fe input is the primary Fe source for the ocean. This study is focused on the distribution of Fe along the Lena River freshwater plume in the Laptev Sea using samples from a 600 km long transect in front of the Lena River mouth. Separation of the particulate ( >  0.22 μm), colloidal (0.22 μm–1 kDa), and truly dissolved (<  1 kDa) fractions of Fe was carried out. The total Fe concentrations ranged from 0.2 to 57μM with Fe dominantly as particulate Fe. The loss of >  99% of particulate Fe and about 90% of the colloidal Fe was observed across the shelf, while the truly dissolved phase was almost constant across the Laptev Sea. Thus, the truly dissolved Fe could be an important source of bioavailable Fe for plankton in the central Arctic Ocean, together with the colloidal Fe. Fe-isotope analysis showed that the particulate phase and the sediment below the Lena River freshwater plume had negative δ56Fe values (relative to IRMM-14). The colloidal Fe phase showed negative δ56Fe values close to the river mouth (about -0.20 ‰) and positive δ56Fe values in the outermost stations (about +0.10 ‰). We suggest that the shelf zone acts as a sink for Fe particles and colloids with negative δ56Fe values, representing chemically reactive ferrihydrites. The positive δ56Fe values of the colloidal phase within the outer Lena River freshwater plume might represent Fe oxyhydroxides, which remain in the water column, and will be the predominant δ56Fe composition in the Arctic Ocean.

  • 9.
    Conrad, Sarah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Löfgren, Stefan
    Bauer, Susanne
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Iron isotopes in headwater streamsManuscript (preprint) (Other academic)
  • 10.
    Conrad, Sarah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Löfgren, Stefan
    Department of Aquatic Sciences and Assessment; Section for Geochemistry and Hydrology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Bauer, Susanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Seasonal Variations of Redox State in Hemiboreal Soils Indicated by Changes of δ56Fe, Sulfate, and Nitrate in Headwater Streams2019In: Acs Earth And Space Chemistry, ISSN 2472-3452, Vol. 3, no 12, p. 2816-2823Article in journal (Refereed)
    Abstract [en]

    During recent decades, much focus has been put on the iron (Fe) isotope ratios in soils, rivers, and oceans, while studies on the variation in headwater streams are scarce. Here we assess seasonal water chemical data from 104 hemiboreal headwater streams. Between summer and late autumn, decreasing Fe concentrations and simultaneously increasing sulfate and nitrate concentrations suggest a shift from reduced to oxidized conditions in the soils along the main groundwater flow paths. Fe isotope data, obtained from a subpopulation of 16 streams, show low δ56Fe ratios during summer drought, indicating an important influx of reduced groundwater to the streams with primarily Fe(II) as an important Fe source. In total, the δ56Fe data ranged between −0.8 ± 0.1 and 1.8 ± 0.1‰ with the lowest values in summer and maximum δ56Fe ratios in late autumn or spring, indicating an influx of more oxidized, less Fe(II) rich groundwater during those seasons. Local differences in δ56Fe ratios between the headwater streams, seemed to be driven by the different soil redox status of the catchments. The streams with the lowest δ56Fe ratios during summer are characterized by a small share (4.4 ± 6.6%) of wetlands, indicating discharge of reduced groundwater from mainly anoxic, moist, organic-rich mineral soils during drought. Relatively high total organic carbon (TOC) concentrations (2.4 ± 1.1 mM) and low pH (5.2 ± 0.8) may have restricted efficient Fe(II) oxidation in streamwater especially during the late autumn survey. Our results from hemiboreal headwater streams reveal the importance of climatic, pedogenic, and land cover-derived controls on the provenance of stream Fe loads that is likely broadly applicable to similar streams elsewhere.

  • 11.
    Conrad, Sarah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Wuttig, Kathrin
    GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Australia.
    Jansen, Nils
    GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia.
    Rodushkin, Ilia
    ALS Laboratory Group, ALS Scandinavia AB, Luleå, Sweden.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    The stability of Fe isotope signatures during low salinity mixing in subarctic estuaries2019In: Aquatic geochemistry, ISSN 1380-6165, E-ISSN 1573-1421, Vol. 25, no 5-6, p. 195-218Article in journal (Refereed)
    Abstract [en]

    We have studied iron (Fe)-isotope signals in particles (> 0.22 µm) and the dissolved phase (< 0.22 µm) in two subarctic, boreal rivers, their estuaries and the adjacent sea in northern Sweden. Both rivers, the Råne and the Kalix, are enriched in Fe and organic carbon (up to 29 µmol/L and up to 730 µmol/L, respectively). Observed changes in the particulate and dissolved phase during spring flood in May suggest different sources of Fe to the rivers during different seasons. While particles show a positive Fe-isotope signal during winter, during spring flood, the values are negative. Increased discharge due to snowmelt in the boreal region is most times accompanied by flushing of the organic-rich sub-surface layers. These upper podzol soil layers have been shown to be a source for Fe-organic carbon aggregates with a negative Fe-isotope signal. During winter, the rivers are mostly fed by deep groundwater, where Fe occurs as Fe(oxy)hydroxides, with a positive Fe-isotope signal. Flocculation during initial estuarine mixing does not change the Fe-isotope compositions of the two phases. Data indicate that the two groups of Fe aggregates flocculate diversely in the estuaries due to differences in their surface structure. Within the open sea, the particulate phase showed heavier δ56Fe values than in the estuaries. Our data indicate the flocculation of the negative Fe-isotope signal in a low salinity environment, due to changes in the ionic strength and further the increase of pH.

  • 12.
    Herzog, Simon D.
    et al.
    Department of Science and Environment, Roskilde University, Roskilde, Denmark.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Persson, Per
    Centre for Environmental and Climate Research & Department of Biology, Lund University, Lund, Sweden.
    Kritzberg, Emma S.
    Department of Biology/Aquatic Ecology, Lund University, Lund, Sweden.
    Spring flood induced shifts in Fe speciation and fate at increased salinity2019In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 109, article id 104385Article in journal (Refereed)
    Abstract [en]

    Rivers have traditionally been viewed as negligible sources of iron (Fe) to marine waters, as most Fe gets lost during estuarine mixing. However, recent findings demonstrate that Fe from boreal rivers display a higher resistance towards salinity-induced aggregation, presumably due to stabilizing interactions with organic matter. Previous studies have shown that Fe (oxy)hydroxides are selectively removed by aggregation processes, and that organic Fe complexes are less affected by increasing salinity. It has been further proposed that Fe speciation varies in response to seasonal differences in hydrology. In this study X-ray absorption spectroscopy (XAS) was used to determine the temporal variation in Fe speciation and the connection to Fe stability in response to increasing salinity in two boreal rivers (Kalix and Råne River), with the purpose to better understand the fate of riverine Fe export. Sampling was done from winter pre-flood, over the spring flood, to post-flood conditions (early April until mid June). In addition, parallel analyses for Fe speciation and isotope composition (δ56Fe relative to IRMM-14) were made on river samples, as well as salinity-induced aggregates and the fraction remaining in suspension, with the main objective to test if δ56Fe reflect the speciation of Fe.

    The contribution of organically complexed Fe increased during spring flood compared to the pre- and post-flood, as did Fe transport capacity. However, since Fe (oxy)hydroxides were dominating throughout the sampling period, the seasonal variability was small. Interestingly, salinity-induced aggregation experiments revealed that Fe (oxy)hydroxides, which dominated aggregates, displayed lower δ56Fe than in the river samples Fe, while organic Fe complexes in suspension had higher δ56Fe values. The seasonal variability in Fe isotope signature could not be simply linked to Fe speciation, but was probably also influenced by variation in source areas of Fe and processes along the flow-path that alter both Fe speciation and isotopic composition.

  • 13.
    Ingri, Johan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Lidman, Fredfrik
    Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå.
    Nordblad, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Engström, Emma
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. ALS Laboratory Group, ALS Scandinavia AB.
    Rodushkin, Ilia
    ALS Laboratory Group, ALS Scandinavia AB.
    Porcelli, Don
    Department of Earth Sciences, University of Oxford.
    Iron isotope pathways in the boreal landscape: Role of the riparian zone2018In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 239, p. 49-60Article in journal (Refereed)
    Abstract [en]

    Stable Fe isotope compositions have been measured in water samples of the subarctic Kalix River, a first-order stream, and soil water samples from a riparian soil profile adjacent to the first-order stream (Northern Sweden). In the first-order stream, dominated by forest, both the particulate (>0.22 µm) and dissolved (<0.22 µm) phase showed negative δ56Fe values (relative to IRMM-014) during base flow and meltwater discharge in May (−0.97 to −0.09‰). The Fe isotope composition in the water from the riparian soil profile varied between −0.20 and +0.91‰ with sharp gradients near the groundwater table. A linear correlation between the δ56Fe values and the TOC/Febulk ratio was measured during snowmelt in the unfiltered river waters (δ56Fe from −0.02 to +0.54‰), suggesting mixing of two Fe components. Two groups of Fe aggregates, with different Fe isotope compositions, are formed in the boreal landscape. We propose that carbon-rich aggregates, Fe(II)(III)-OC, have negative δ56Fe values and Fe-oxyhydroxides have positive δ56Fe values. A mixture of these two components can explain temporal variations of the Fe isotope composition in the Kalix River. This study suggests that stable Fe isotopes can be used as a tool to track and characterize suspended Fe-organic carbon aggregates during transport from the soil, via first-order streams and rivers, to coastal sediment. Furthermore, the differences in Fe isotope values in the Kalix River and the first-order stream during base flow conditions suggest that the primary Fe sources for river water change throughout the year. This model is combining the Fe isotope composition of first-order streams and rivers to weathering and transport processes in the riparian soil.

  • 14.
    Wortberg, Katharina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Conrad, Sarah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Andersson, Per S.
    Department of Geosciences, Swedish Museum of Natural History.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Strontium isotopes: A tracer for river suspended iron aggregates2017In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 79, p. 85-90Article in journal (Refereed)
    Abstract [en]

    The Kalix River shows distinct temporal variations in the Sr-isotope ratio in filtered water (0.726–0.732). During base flow in winter the 87Sr/86Sr ratio is on average 0.730. When discharge increases and peaks during spring flood the 87Sr/86Sr ratio shows the most radiogenic (0.732) values. The temporal variations in the 87Sr/86Sr ratio in the Kalix River can be explained by mixing of water from the woodlands and the mountain areas.

    During high water discharge in May the 87Sr/86Sr ratios are more radiogenic in the suspended phase (1 kDa - 70 μm) compared to the truly dissolved phase (<1 kDa). The difference in 87Sr/86Sr ratio between the two phases (Δ 87Sr/86Sr) is linearly correlated with the suspended iron concentration. During spring flood Sr and Fe derived from an additional source, reach the river. Deep groundwater has a more radiogenic 87Sr/86Sr isotope ratio than the Kalix River during spring flood and thus, represents a possible source for the suspended Fe and the associated Sr. Strontium can be coprecipitated with and adsorbed to different types of Fe aggregates. We propose that the Sr-isotope ratio in the suspended phase reflects the isotopic composition of the water at the interface between anoxic groundwater and oxic stream water in the riparian zone, where the Fe aggregates are formed. These particles dominate the suspended phase in the river and the mixing with mountain waters, poor in Fe, produces the difference in the isotopic signature.

    The different signatures in suspended and truly dissolved fraction indicate that these aggregates are relatively stable during stream-river transport. As such the 87Sr/86Sr can be used to trace the origin of the non-detrital suspended phase.

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