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© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bekaert, D. V., Auro, M., Shollenberger, Q. R., Liu, M.-C., Marschall, H., Burton, K. W., Jacobsen, B., Brennecka, G. A., McPherson, G. J., von Mutius, R., Sarafian, A., & Nielsen, S. G. Fossil records of early solar irradiation and cosmolocation of the CAI factory: a reappraisal. Science Advances, 7(40), (2021): eabg8329, https://doi.org/10.1126/sciadv.abg8329., Calcium-aluminum–rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V–10Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of 10Be and argue that CV CAIs possess essentially a homogeneous level of 10Be, inherited during their formation. Based on numerical modeling of 50V–10Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs., This study was funded by NASA Emerging Worlds grant NNX16AD36G to S.G.N. and prepared by LLNL under contract DE-AC52-07NA27344 with release number LLNL-JRNL-819045. M.C.L acknowledges the support by the NASA grant 80NSSC20K0759. The UCLA ion microprobe facility is partially supported by a grant from the NSF Instrumentation and Facilities program.

Calcium-aluminum–rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V–10Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of 10Be and argue that CV CAIs possess essentially a homogeneous level of 10Be, inherited during their formation. Based on numerical modeling of 50V–10Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs.

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bekaert, D. V., Auro, M., Shollenberger, Q. R., Liu, M.-C., Marschall, H., Burton, K. W., Jacobsen, B., Brennecka, G. A., McPherson, G. J., von Mutius, R., Sarafian, A., & Nielsen, S. G. Fossil records of early solar irradiation and cosmolocation of the CAI factory: a reappraisal. Science Advances, 7(40), (2021): eabg8329, https://doi.org/10.1126/sciadv.abg8329., Calcium-aluminum–rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V–10Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of 10Be and argue that CV CAIs possess essentially a homogeneous level of 10Be, inherited during their formation. Based on numerical modeling of 50V–10Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs., This study was funded by NASA Emerging Worlds grant NNX16AD36G to S.G.N. and prepared by LLNL under contract DE-AC52-07NA27344 with release number LLNL-JRNL-819045. M.C.L acknowledges the support by the NASA grant 80NSSC20K0759. The UCLA ion microprobe facility is partially supported by a grant from the NSF Instrumentation and Facilities program.

Calcium-aluminum–rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V–10Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of 10Be and argue that CV CAIs possess essentially a homogeneous level of 10Be, inherited during their formation. Based on numerical modeling of 50V–10Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs.

Chemical weathering of volcanic rocks in warm and humid climates contributes disproportionately to global solute fluxes. Geochemical signatures of solutes and solids formed during this process can help quantify and reconstruct weathering intensity in the past. Here, we measured silicon (Si) and germanium (Ge) isotope ratios of the soils, clays, and fluids from a tropical lowland rainforest in Costa Rica. The bulk topsoil is intensely weathered and isotopically light (mean ± 1σ: δ30Si = −2.1 ± 0.3‰, δ74Ge = −0.13 ± 0.12‰) compared to the parent rock (δ30Si = −0.11 ± 0.05‰, δ74Ge = 0.59 ± 0.07‰). Neoforming clays have even lower values (δ30Si = −2.5 ± 0.2‰, δ74Ge = −0.16 ± 0.09‰), demonstrating a whole‐system isotopic shift in extremely weathered systems. The lowland streams represent mixing of dilute local fluids (δ30Si = 0.2 − 0.6‰, δ74Ge = 2.2 − 2.6‰) with solute‐rich interbasin groundwater (δ30Si = 1.0 ± 0.2‰, δ74Ge = 4.0‰). Using a Ge‐Si isotope mass balance model, we calculate that 91 ± 9% of Ge released via weathering of lowland soils is sequestered by neoforming clays, 9 ± 9% by vegetation, and only 0.2 ± 0.2% remains dissolved. Vegetation plays an important role in the Si cycle, directly sequestering 39 ± 14% of released Si and enhancing clay neoformation in surface soils via the addition of amorphous phytolith silica. Globally, volcanic soil δ74Ge closely tracks the depletion of Ge by chemical weathering (τGe), whereas δ30Si and Ge/Si both reflect the loss of Si (τSi). Because of the different chemical mobilities of Ge and Si, a δ74Ge‐δ30Si multiproxy system is sensitive to a wider range of weathering intensities than each isotopic system in isolation.

Molybdenum (Mo) isotopes have proved useful in the reconstruction of paleoredox conditions. Their application generally relies upon a simplified model of ocean inputs in which rivers dominate Mo fluxes to the oceans and hydrothermal fluids are considered to be a minor contribution. To date, however, little attention has been paid to the extent of Mo isotope variation of hydrothermal waters, or to the potential effect of direct groundwater discharge to the oceans. Here we present Mo isotope data for two Icelandic groundwater systems (Mývatn and Þeistareykir) that are both influenced by hydrothermal processes. Relative to NIST 3134 = +0.25‰, the cold (<10 °C) groundwaters (δ98/95MoGROUNDWATER = −0.15‰ to +0.47‰; ) show little, if any, fractionation from the host basalt (MoBASALT = +0.16‰ to −0.12‰) and are, on average, lighter than both global and Icelandic rivers. In contrast, waters that are hydrothermally influenced (>10 °C) possess isotopically heavy δ98/95MoHYDROTHERMAL values of +0.25‰ to +2.06‰ with the possibility that the high temperature endmembers are even heavier. Although the mechanisms driving this fractionation remain unresolved, the incongruent dissolution of the host basalt and both the dissolution and precipitation of sulfides are considered. Regardless of the processes driving these variations, the δ98Mo data presented in this study indicate that groundwater and hydrothermal waters have the potential to modify ocean budget calculations.

Zinc is an essential micronutrient that is ultimately released during mineral weathering. In soils, organic matter plays a key role in influencing Zn partitioning and therefore on Zn biogeochemical cycling. Soil organic matter is partitioned between carbon that is more readily available for decomposition by microorganisms, and more stable carbon transiently preserved from decomposition. The role of the stable pool of soil organic matter on Zn biogeochemical cycling remains poorly understood. The pool of stable carbon is controlled by combination with mineral constituents or is material that is intrinsically resistant to decomposition. The Zn stable isotopes are fractionated by interactions between Zn and soil mineral and organic constituents. This study reports the Zn isotope composition of five Icelandic soil profiles derived from the same parent basalt and characterized by contrasting degrees of weathering and organic matter content (δ66Zn = + 0.10 ± 0.05 to + 0.35 ± 0.02‰), the distribution of reactive mineral constituents available to form associations with soil organic matter, and the amount of stable organic carbon. Throughout these soils, the δ66Zn isotope variations are little influenced by mineral constituents, but rather by soil organic matter content. These data suggest that a combination of organic matter accumulation and Zn loss by leaching is required to explain the observed decrease in Zn concentration in soils and lighter soil δ66Zn with increasing organic carbon content. These results suggest that the presence of stable organic carbon in soils provides a pool of light Zn, attributed to the Zn isotope signature of organic matter partially preserved from decomposition. Crucially, this stable organic carbon pool may also contribute to the formation of the light Zn isotope sink reported in organic-rich marine sediments, a key output required to explain the oceanic mass balance of Zn isotopes., SCOPUS: ar.j, info:eu-repo/semantics/published

Rainwater plays a major role in determining the transfer of elements and pollutants to soils and hydrological catchments, with compositional variations reflecting the extent of mixing between marine (sea-salt), terrestrial (dust and vegetation) and anthropogenic aerosols. While the radiogenic strontium isotope system (87Sr/86Sr) is often used to help constrain the different sources of atmospheric Sr, the degree of variability in the stable strontium isotope system (δ88/86Sr) remains unresolved. In order to determine how atmospheric Sr affects the δ88/86Sr composition of water entering the hydrological cycle this study analysed a suite of rainwater samples collected over the course of a year in central Paris. Rainwater δ88/86Sr compositions were found to range from 0.13‰ to 0.32‰, with 87Sr/86Sr ratios varying between 0.70796 and 0.71093. No seasonality was observed in δ88/86Sr, whereas 87Sr/86Sr ratios were observed to be generally more radiogenic in the summer and less radiogenic in the winter. Strontium enrichment factors significantly above seawater implied a predominantly terrestrial (non-sea-salt) origin of Sr in rainwater, with the δ88/86Sr and 87Sr/86Sr composition of this terrestrial fraction consistent with a mixture of Sr derived from carbonate dust and agricultural fertiliser. Evidence for a ~ 0.1‰ decrease in the δ88/86Sr composition of the River Seine as it passes through Paris suggests that anthropogenic pollutants may contribute to significant regional variations in the composition of Sr in the hydrological cycle. Together these results demonstrate that there is significant potential for both temporal and spatial variations in the δ88/86Sr and 87Sr/86Sr composition of rainwater that need to be taken into consideration when studying δ88/86Sr variations in localised catchments.

The stable strontium isotope system (δ88/86Sr) has recently been suggested to be a suitable proxy for determining variations in the strength of the marine carbonate system, the principal output flux of oceanic Sr. However, in order to be able to interpret carbonate-driven variations in δ88/86Srseawater a robust understanding of δ88/86Srinput is required. Surprisingly only a limited amount of δ88/86Sr data currently exists for rivers and hydrothermal fluids, thus this study assesses the variability of δ88/86Sr and 87Sr/86Sr in global rivers, hydrothermal fluids and porewaters, as well as minor marine Sr sources such as continental dust, rainwater and glacial ice. Our analyses broadly confirm the findings of Krabbenhöft et al. (2010) [Krabbenhöft, A., Eisenhauer, A., Böhm, F., Vollstaedt, H., Fietzke, J., Liebetrau, V., Augustin, N., Peucker-Ehrenbrink, B., Müller, M.N., Horn, C., Hansen, B.T., Nolte, N., Wallmann, K., 2010. Constraining the marine strontium budget with nautral strontium isotope fractionations (87Sr/86Sr∗, δ88/86Sr) of carbonates, hydrothermal solutions and river waters. Geochim. Cosmochim. Acta, 74, 4097-4109], and reveal flux-weighted δ88/86Srriverine and 87Sr/86Srriverine compositions of 0.32 ‰ and 0.71299 respectively. The hydrothermal fluids analysed in this study are consistent with an end-member δ88/86Srhydrothermal composition that is the same as the oceanic crust at ∼0.24 ‰, although three samples that display δ88/86Sr compositions offset from the seawater-hydrothermal mixing trend suggest that the precipitation of alteration phases such as anhydrite may drive δ88/86Srhydrothermal to higher values. Porewater fluids obtained from sediment cores in the Atlantic and Pacific Oceans have δ88/86Sr compositions within error of seawater (0.39 ‰), implying that the diagenetic flux of Sr may not significantly affect the δ88/86Sr composition of seawater. Continental loess samples have δ88/86Sr compositions that are consistently lighter than, or equal to

Highlights: • High-precision glacial–interglacial 87Sr/86Sr record from planktic foraminifera. • Major oceans yield indistinguishable 87Sr/86Sr values at ±5 ppm level of precision. • Foraminifera show no resolvable 87Sr/86Sr variation since last glacial interval. • These data accommodate a ±12% variation for the steady-state weathering flux. • A short-term weathering pulse during de-glaciation is not accommodated by the data. Abstract Existing strontium radiogenic isotope (87Sr/86Sr) measurements for foraminifera over Quaternary glacial–interglacial climate cycles provide no evidence for variations in the isotope composition of seawater at the ±9–13 ppm level of precision. However, modelling suggests that even within this level of uncertainty significant (up to 30%) variations in chemical weathering of the continents are permitted, accounting for the longer-term rise in 87Sr/86Sr over the Quaternary, and the apparent imbalance of Sr in the oceans at the present-day. This study presents very high-precision 87Sr/86Sr isotope data for modern seawater from each of the major oceans, and a glacial–interglacial seawater record preserved by planktic foraminifera from Ocean Drilling Program (ODP) Site 758 in the north-east Indian ocean. Strontium isotope 87Sr/86Sr measurements for modern seawater from the Atlantic, Pacific and Indian Oceans are indistinguishable from one another (87Sr/86Sr = 0.7091792 ± 0.0000021, n=17n=17) at the level of precision obtained in this study (±4.9 ppm 2σ). This observation is consistent with the very long residence time of Sr in seawater, and underpins the utility of this element for high precision isotope stratigraphy. The 87Sr/86Sr seawater record preserved by planktic foraminifera shows no resolvable glacial–interglacial variation (87Sr/86Sr = 0.7091784 ± 0.0000035, n=10n=10), and limits the response of seawater to variations in the chemical weathering flux and/or composition to ±4.9 ppm or less. Calculations suggest that a variation of ±12%

Variations in lithium and silicon isotope ratios in groundwaters of the Great Artesian Basin in Australia, and the causes of these variations, have been explored. The chemistries of Li and Si in groundwater are influenced by the dissolution of primary phases, the formation of secondary minerals, and the reaction of solid phases with dissolved constituents, while isotopic variations are generated by uptake into clays, which preferentially incorporate the light isotopes. The lithium isotopic composition (expressed as View the MathML sourceδLi7) of the groundwaters ranges from +9 to +16‰+16‰, and clearly reflects changes in aquifer conditions. Reaction-transport modelling indicates that changes in Li concentrations are principally controlled by the ratio of the weathering rate of primary minerals to the precipitation rate of secondary minerals, whereas View the MathML sourceδLi7 is affected by the extent of isotope fractionation during secondary mineral formation (which is dependent on mineralogy). The patterns of groundwater Si concentrations and View the MathML sourceδSi30 values versus flow distance suggest that Si is at steady state in the aquifer. The View the MathML sourceδSi30 value of most of the groundwater samples is close to −1‰−1‰, which is significantly lower than the View the MathML sourceδSi30 value of the reservoir rocks (∼0‰∼0‰). Since precipitation of clays preferentially removes the light Si isotopes from solution, the most plausible explanation for these low groundwater View the MathML sourceδSi30 values is addition of Si by dissolution of isotopically light secondary minerals. These data, together with model calculations, show that Li isotopes are extremely sensitive to changes in the chemical and physical conditions in the aquifer, whereas Si is not. Importantly, the model suggests that even in large aquifers with long fluid residence times, where steady-state would be expected to be reached, the concentrations and isotopic fractionation of trace

The quantification of the sources and sinks of elements to the oceans forms the basis of our understanding of global geochemical cycles and the chemical evolution of the Earth's surface. There is, however, a large imbalance in the current best estimates of the global fluxes to the oceans for many elements. In the case of strontium (Sr), balancing the input from rivers would require a much greater mantle-derived component than is possible from hydrothermal water flux estimates at mid-ocean ridges. Current estimates of riverine fluxes are based entirely on measurements of dissolved metal concentrations, and neglect the impact of riverine particulate dissolution in seawater. Here we present 87Sr/86Sr isotope data from an Icelandic estuary, which demonstrate rapid Sr release from the riverine particulates. We calculate that this Sr release is 1.1–7.5 times greater than the corresponding dissolved riverine flux. If such behaviour is typical of volcanic particulates worldwide, this release could account for 6–45% of the perceived marine Sr budget imbalance, with continued element release over longer timescales further reducing the deficit. Similar release from particulate material will greatly affect the marine budgets of many other elements, changing our understanding of coastal productivity, and anthropogenic effects such as soil erosion and the damming of rivers.

The quantification of the sources and sinks of elements to the oceans forms the basis of our understanding of global geochemical cycles and the chemical evolution of the Earth's surface. There is, however, a large imbalance in the current best estimates of the global fluxes to the oceans for many elements. In the case of strontium (Sr), balancing the input from rivers would require a much greater mantle-derived component than is possible from hydrothermal water flux estimates at mid-ocean ridges. Current estimates of riverine fluxes are based entirely on measurements of dissolved metal concentrations, and neglect the impact of riverine particulate dissolution in seawater. Here we present 87Sr/86Sr isotope data from an Icelandic estuary, which demonstrate rapid Sr release from the riverine particulates. We calculate that this Sr release is 1.1–7.5 times greater than the corresponding dissolved riverine flux. If such behaviour is typical of volcanic particulates worldwide, this release could account for 6–45% of the perceived marine Sr budget imbalance, with continued element release over longer timescales further reducing the deficit. Similar release from particulate material will greatly affect the marine budgets of many other elements, changing our understanding of coastal productivity, and anthropogenic effects such as soil erosion and the damming of rivers.

The magnesium (Mg) isotope composition of rivers is sensitive to changes in the balance of primary mineral dissolution and secondary mineral formation. As these processes are regulated by climate then changes to the Earth's climate system, such as the onset of glaciation, could potentially alter the isotopic behaviour of Mg in rivers. To investigate how Mg isotopes behave during glacial weathering, we have determined the Mg concentration and Mg isotope ratio for the dissolved, suspended and bedload phases of glacial and non-glacial rivers in west Greenland. This region is essentially monolithological and there is little biological activity; hence isotope variations largely result from differences in weathering processes. Dissolved Mg in rivers is always enriched in the light Mg isotopes relative to the bedload (δ26Mg = − 0.4‰), and the glacial rivers have lighter Mg isotope compositions (δ26Mg − 1 to − 1.3‰) than the non-glacial rivers (δ26Mg ~ − 0.6‰). Enrichment of light Mg in the dissolved load is consistent with the preferential uptake of heavy Mg from solution during the formation of secondary silicate minerals. However, evidence from saturation state modelling suggests that little secondary mineral formation is likely to have occurred in the glacial rivers because the concentration of dissolved solids is very low. Moreover, the glacial derived suspended sediment has identical Mg isotope ratios to the bedload. These observations suggest that the formation of secondary weathering minerals is not controlling the behaviour of Mg isotopes in these rivers. Rather, variations in the δ26Mg value of the dissolved load are attributed to incongruent weathering of the solid phase: preferential dissolution of carbonate minerals, which have low δ26Mg (− 1.1 to − 5.2‰), imparts a more negative δ26Mg signal to the glacial river waters. Although our study indicates that the Mg isotopic composition of the dissolved load is sensitive to changes in weathering congruence, it is un

This study presents uranium and thorium concentrations and activity ratios for all riverine phases (bedload, suspended load, dissolved load and colloids) from basaltic terrains in Iceland and the Azores. Small basaltic islands, such as these, are thought to account for ~ 25% of CO2 consumed by global silicate weathering, and for ~ 45% of the flux of suspended material to the oceans. These data indicate that [U] and [Th] in the dissolved and colloidal fractions are strongly controlled by pH, and to a much lesser extent by levels of dissolved organic carbon (which are low in these environments). At high pH, basalt glass dissolution is enhanced, and secondary mineral formation (e.g. Fe-oxyhydroxides and allophane) is suppressed, resulting in high dissolved [U], and low colloidal [U] and [Th], indicating a direct chemical weathering control on elemental abundances. When the dissolved (234U/238U) activity ratio is >~1.3 (i.e. when physical weathering, groundwater contribution or soil formation are high), there is little isotope exchange between dissolved and colloidal fractions. At lower activity ratios, the dissolved load and colloids have indistinguishable activity ratios, suggesting that when chemical weathering rates are high, secondary clay formation is also high, and colloids rapidly adsorb dissolved U. Many of the suspended sediment samples have (234U/238U) activity ratios of > 1, which suggests that uptake of U onto the suspended load is important. Identical (230Th/232Th) in suspended, dissolved and colloidal samples suggests that Th, like U, is exchanged or sorbed rapidly between all riverine phases. This particle-reactivity, combined with poorly constrained contributions from groundwater and hydrothermal water, and short-term variations in input to soils (volcanic and glacial), suggests that U-series nuclides in riverine material from such basaltic terrains are unlikely to reflect steady state erosion processes.

This study presents uranium and thorium concentrations and activity ratios for all riverine phases (bedload, suspended load, dissolved load and colloids) from basaltic terrains in Iceland and the Azores. Small basaltic islands, such as these, are thought to account for ~ 25% of CO2 consumed by global silicate weathering, and for ~ 45% of the flux of suspended material to the oceans. These data indicate that [U] and [Th] in the dissolved and colloidal fractions are strongly controlled by pH, and to a much lesser extent by levels of dissolved organic carbon (which are low in these environments). At high pH, basalt glass dissolution is enhanced, and secondary mineral formation (e.g. Fe-oxyhydroxides and allophane) is suppressed, resulting in high dissolved [U], and low colloidal [U] and [Th], indicating a direct chemical weathering control on elemental abundances. When the dissolved (234U/238U) activity ratio is >~1.3 (i.e. when physical weathering, groundwater contribution or soil formation are high), there is little isotope exchange between dissolved and colloidal fractions. At lower activity ratios, the dissolved load and colloids have indistinguishable activity ratios, suggesting that when chemical weathering rates are high, secondary clay formation is also high, and colloids rapidly adsorb dissolved U. Many of the suspended sediment samples have (234U/238U) activity ratios of > 1, which suggests that uptake of U onto the suspended load is important. Identical (230Th/232Th) in suspended, dissolved and colloidal samples suggests that Th, like U, is exchanged or sorbed rapidly between all riverine phases. This particle-reactivity, combined with poorly constrained contributions from groundwater and hydrothermal water, and short-term variations in input to soils (volcanic and glacial), suggests that U-series nuclides in riverine material from such basaltic terrains are unlikely to reflect steady state erosion processes.

Greenland is by far the dominant source of glacial runoff to the oceans but the controls on the chemical and isotopic composition of this runoff are poorly known. To better constrain glacial effects on weathering processes, we have conducted elemental and lithium isotope analyses of glacial and non-glacial rivers in gneiss catchments in West Greenland. The glacial rivers have high total suspended solids (0.5 g l− 1) and low total dissolved solids (12 μScm− 1) relative to the non-glacial rivers, and they contain a higher proportion of dissolved Ca2+ and K+ because of subglacial, preferential, weathering of trace carbonates and biotite. The glacial rivers also have high SO42− because of the oxidation of trace sulphides under the ice. Both glacial and non-glacial rivers have high δ7Li (respectively, not, vert, similar 26‰ and not, vert, similar 30‰) relative to the rocks from which the Li is derived (not, vert, similar 8‰). Saturation state modelling suggests that this is due to the formation of Fe-oxyhydroxides in the non-glacial rivers, with preferential uptake of 6Li during inner sphere sorption of Li+ on the Fe-oxyhydroxide surface. Glacial rivers, however, are undersaturated with respect to clay minerals and Fe-oxyhydroxides. Nevertheless, leaching of suspended sediments indicates that not, vert, similar 65% of the Li in these sediments is associated with Fe-oxyhydroxide phases, and the δ7Li value of this Li is low, not, vert, similar 5‰. These results suggest that these Fe-oxyhydroxides formed under the ice, as a product of sulphide oxidation, with preferential uptake of 6Li onto the mineral surface. Solubilisation of Li from these Fe-oxyhydroxide phases is unlikely to represent a significant flux of Li to the oceans. Moreover, because the difference between the δ7Li values of glacial vs non-glacial rivers is small, glaciation has not had a significant impact on the Li isotopic composition of the riverine flux delivered to the oceans in the past, even at the heig

This study presents lithium (Li) and magnesium (Mg) isotope data from experiments designed to assess the effects of dissolution of primary phases and the formation of secondary minerals during the weathering of basalt. Basalt glass and olivine dissolution experiments were performed in mixed through-flow reactors under controlled equilibrium conditions, at low pH (2–4) in order to keep solutions undersaturated (i.e. far-from equilibrium) and inhibit the formation of secondary minerals. Combined dissolution–precipitation experiments were performed at high pH (10 and 11) increasing the saturation state of the solutions (moving the system closer to equilibrium) and thereby promoting the formation of secondary minerals. At conditions far from equilibrium saturation state modelling and solution stoichiometry suggest that little secondary mineral formation has occurred. This is supported by the similarity of the dissolution rates of basalt glass and olivine obtained here compared to those of previous experiments. The δ7Li isotope composition of the experimental solution is indistinguishable from that of the initial basalt glass or olivine indicating that little fractionation has occurred. In contrast, the same experimental solutions have light Mg isotope compositions relative to the primary phases, and the solution becomes progressively lighter with time. In the absence of any evidence for secondary mineral formation the most likely explanation for these light Mg isotope compositions is that there has been preferential loss of light Mg during primary phase dissolution. For the experiments undertaken at close to equilibrium conditions the results of saturation state modelling and changes in solution chemistry suggest that secondary mineral formation has occurred. X-ray diffraction (XRD) measurements of the reacted mineral products from these experiments confirm that the principal secondary phase that has formed is chrysotile. Lithium isotope ratios of the experimental fluid

This study presents uranium (U) and lithium (Li) isotope and major and trace element data for the dissolved load, suspended particles and bedload from rivers draining dominantly basaltic catchments on the island of Sao Miguel in the Azores Archipelago. Uranium activity ratios are at secular equilibrium in the bedload, but are higher for suspended material, suggesting sorption of uranium from the solution onto particle surfaces. The (234U/238U) of the riverine dissolved phase varies between 1.02 and 1.86, and lies on a mixing trend between the values expected from chemical weathering of basalt (high [U]; (234U/238U) at secular equilibrium) and an endmember with low [U] and high (234U/238U), which probably reflects α-recoil effects associated with physical weathering and/or soil formation. Lithium isotope ratios are consistently lighter in suspended material than the corresponding bedload, suggesting preferential retention of 6Li in the suspended load. In turn, the δ7Li of the dissolved load is always isotopically heavier, ranging from 5.9 to 36.2‰, although the lightest values are affected by hydrothermal input. The lithium isotopic composition of the dissolved load reflects the balance of primary mineral dissolution to secondary mineral formation. Comparison of the behaviour of U and Li isotopes between Sao Miguel, Iceland, and other basaltic terrains suggests that whilst U isotopes are dominated by weathering regimes dependent on factors such as weathering rates, temperature, runoff and climate, neither weathering intensity nor climate exerts a direct influence on Li isotope behaviour; rather the formation of secondary minerals, which is indirectly controlled by climate, weathering, primary mineralogy and biology, appears to play the dominant role.

The application of the molybdenum (Mo) isotope system as a proxy for determining changes in the redox state of the oceans is predicated on the assumption that the composition of continental input can be characterised from crustal rock types, and remains constant. However, it has recently been shown that the δ98/95Mo composition of global rivers varies between 0.15‰ and 2.4‰ and is therefore systematically heavier than the average composition of the continental crust (not, vert, similar 0‰). In order to understand the processes that control Mo-isotope fractionation during weathering this study presents δ98/95Mo and Mo abundance data for rivers (and estuarine samples) from Iceland that drain predominantly basaltic terrains. Resolvable differences are observed in the isotopic composition of the riverine Mo sources; ice (δ98/95Moice > 1.8‰), basaltic bedrock (δ98/95Mobedrock not, vert, similar 0.0‰) and hydrothermal waters (δ98/95Mohydrothermal not, vert, similar−3.4‰). Systematic changes in the dissolved Mo-isotope composition are also observed within river catchments, with δ98/95Mo values increasing from not, vert, similar 0‰ in glacial rivers (close to the source) to not, vert, similar 1‰ downstream, consistent with Mo-isotopes being fractionated during weathering. Analysis of other riverine phases (bedload, colloids and iron-precipitates) demonstrates that these phases preferentially incorporate light Mo-isotopes, and remain coupled to the dissolved load during riverine transportation. A δ98/95Mo profile through the Borgarfjörður estuary exhibits a predominantly conservative mixing behaviour, but suggests that the release of isotopically light Mo from the particulate and/or colloidal phases may occur in the low salinity part of the estuarine mixing zone.

This study presents major and trace elements and uranium (U), lithium (Li) and magnesium (Mg) isotope data for dissolved and suspended particulate material from estuaries draining dominantly basaltic terrains in Iceland (Borgarfjörður) and Sao Miguel (Povoação) in the Azores archipelago. The concentrations of dissolved sodium (Na), calcium (Ca), potassium (K), sulphate (SO4), Mg and Li, and 7Li/6Li and 26Mg/24Mg isotope ratios vary directly as a function of the dissolved chloride concentration [Cl], indicating that these species are non-reactive in these estuaries. However, U appears to be affected either by colloid flocculation or the formation of Fe-oxyhydroxides in Borgarfjörður. The major element composition of suspended particulate material in the estuary at Borgarfjörður shows that the detrital silicates delivered to the estuarine mixing zone are relatively unweathered. Accordingly, the δ26Mg isotope composition of the suspended material is indistinguishable from that of the parent basalts. However, the (234U/238U) activity ratios of the suspended material are significantly different from the parent basalt indicating rapid equilibration of the U isotopes between particles and seawater. The Li concentration and δ7Li isotope composition of the suspended load are also observed to increase with increasing [Cl], consistent with ongoing weathering of detrital material and the formation of secondary minerals in seawater. Depending on the particle residence time in the estuary, this process could remove as much as 15–25% of the global riverine input of Li to the ocean.

This study presents major-, trace-element and Mg isotope data for the dissolved load and suspended particulates of Icelandic rivers draining dominantly basaltic catchments, including both glacier-fed and direct-runoff rivers. These samples provide the opportunity to understand the behaviour of Mg isotopes during chemical weathering, where variations due to lithology are not extant. Given the significant role of Mg in the carbon cycle, such variations may provide important information on the regulation of Earth's climate. Hydrothermal waters, groundwater, precipitation (glacial ice), basalt glass, olivine and representative soils have also been analysed. The dissolved load shows a wide range of δ26Mg compositions, compared to the parent basaltic glass (δ26Mg = − 0.29‰), ranging from − 0.96 to + 0.64‰, while precipitation and hydrothermal waters possess δ26Mg values of − 0.83‰ and + 0.85‰, respectively, with lower Mg concentrations than the dissolved load. Biomass activity in vegetation and organic material in soils and rivers (colloids) appear to have little effect on the Mg isotope compositions. Rather, the data suggest that Mg elemental and isotopic variations are largely controlled by the formation and stability of secondary phases in response to differing hydrological conditions. In some samples seawater, in the form of direct precipitation or glacial runoff, also appears to be an important source of Mg. Glacier-fed rivers, groundwaters, and some direct-runoff rivers, with a high pH, have higher δ26Mg than basalt, which is most likely due to the incorporation of light Mg isotopes in secondary minerals. In contrast, those direct-runoff rivers which have a relatively low pH, have low δ26Mg (relative to basalt), consistent with preferential incorporation of heavy Mg isotopes into secondary phases, although it is not possible to rule out some contribution from precipitation. Riverine suspended particulates are depleted in mobile elements, and have δ26Mg compositions

Experimental investigation of cavitation induced vibrations in a 2-bladed water model inducer was performed for inlet flowrates ranging from 70% to 120% of the design flowrate and over a range of inlet cavitation numbers representative of a typical rocket engine operation. Dynamic (high frequency) pressure transducers were used to record fluctuating pressures along inducer housing (stationary reference frame) up to 2500 Hz, i.e. about 30 times the shaft speed. Data were obtained in two axial planes: one 0.08 diameters upstream and one 0.37 diameters downstream relative to the inducer blade leading edge tip plane. Flow visualization data at conditions typical of tip vortex instabilities at high cavitation number and sheet cavitation are presented and correlated to dynamic signature. Dynamic spectrum of the 2-bladed inducer is compared to data representative of the environment in a 4-bladed rocket engine inducer. The differences in the dynamic characteristics between the 2-bladed and 4-bladed inducers and the potential implications to inducer design decisions for lowering the impact of cavitation induced vibrations in turbomachinery are discussed., Presented at the 12th International Symposium on Transport Phenomena and Dynamics of Rotating Machines (ISROMAC-12) held in Honolulu, HI on 17-22 Feb 2008.

This study presents U and Li isotope and major and trace element data for the dissolved load, suspended particulates and bedload for Icelandic rivers draining predominantly basaltic catchments. Physical erosion rates range from 920 to 2084 t/km2/yr, with the higher values associated with glacier-fed rivers. Chemical erosion rates range from 45 to 91 t/km2/yr, with lower rates being associated with glacier-fed rivers. Uranium activity ratios, (234U/238U), are close to secular equilibrium in the suspended and bedloads, but all dissolved load samples show values greater than unity, ranging from 1.13 to 2.41. The highest (234U/238U) values are found in glacier-fed rivers, and can be attributed to α-recoil effects, as grinding by glaciers locally enhances rates of physical weathering. Activity ratios in glacial rivers decrease with distance from the glacial source due to input from non-glacial tributaries which have high levels of dissolved uranium and lower activity ratios. In contrast, in non-glacial rivers, uranium activity ratios increase with distance downstream due to continued weathering in soils and of bedrock. The δ7Li value of the suspended load is always lower than that of the bedload due to preferential retention of 6Li in secondary minerals during weathering. In turn, the δ7Li value of the dissolved load is always greater than that of the bedload, ranging from 17.0 to 43.7‰. δ7Li for the dissolved load decreases with increasing levels of dissolved silicon, and the saturation index of secondary minerals, which suggests that δ7Li decreases with increasing chemical weathering. There is no correlation between δ7Li values and uranium activity ratios for the dissolved load for non-glacial rivers, but for glacier-fed rivers there is an increase in δ7Li with increasing (234U/238U), suggesting that where physical comminution of mineral grains by glaciers is high, chemical weathering is suppressed, and vice-versa.

Hafnium Hf-176/Hf-177 isotope ratio variations in marine records are thought to reflect changes in continental weathering through time, but the behavior of Hf in rivers, and during weathering, is not well understood. Here, we present Hf-176/Hf-177 data for rivers, bedrock, soils, and leaching experiments for the Moselle basin, Vosges, France. These data strongly suggest that the Hf-176/Hf-177 composition of river waters is controlled by preferential dissolution of accessory phases (i.e., apatite, sphene) versus more resistant minerals (e.g., K-feldspar) and linked to the intensity of silicate weathering. Estimates for the global isotopic composition of riverine Hf suggest that the ocean Hf budget may be dominated by river input, and variations seen in marine records can be directly related to changes in silicate weathering intensity.

Hafnium Hf-176/Hf-177 isotope ratio variations in marine records are thought to reflect changes in continental weathering through time, but the behavior of Hf in rivers, and during weathering, is not well understood. Here, we present Hf-176/Hf-177 data for rivers, bedrock, soils, and leaching experiments for the Moselle basin, Vosges, France. These data strongly suggest that the Hf-176/Hf-177 composition of river waters is controlled by preferential dissolution of accessory phases (i.e., apatite, sphene) versus more resistant minerals (e.g., K-feldspar) and linked to the intensity of silicate weathering. Estimates for the global isotopic composition of riverine Hf suggest that the ocean Hf budget may be dominated by river input, and variations seen in marine records can be directly related to changes in silicate weathering intensity.

Hafnium Hf-176/Hf-177 isotope ratio variations in marine records are thought to reflect changes in continental weathering through time, but the behavior of Hf in rivers, and during weathering, is not well understood. Here, we present Hf-176/Hf-177 data for rivers, bedrock, soils, and leaching experiments for the Moselle basin, Vosges, France. These data strongly suggest that the Hf-176/Hf-177 composition of river waters is controlled by preferential dissolution of accessory phases (i.e., apatite, sphene) versus more resistant minerals (e.g., K-feldspar) and linked to the intensity of silicate weathering. Estimates for the global isotopic composition of riverine Hf suggest that the ocean Hf budget may be dominated by river input, and variations seen in marine records can be directly related to changes in silicate weathering intensity.

The Sulitjelma fold nappe represents part of a Caledonian marginal basin obducted during the closure of the Iapetus Ocean and collision between Laurentia and Baltica. Metamorphic pressure-temperature (P-T) paths indicate that various parts of the Sulitjelma fold nappe followed characteristic clockwise P-T paths involving prograde burial followed by prograde exhumation and then near-isothermal exhumation prior to cooling. Geochronological results indicate that foreland rocks followed this general P-T path before more hinterlandward rocks, such that foreland rocks underwent exhumation while hinterlandward rocks were still being buried. This is consistent with the fold nappe passing through a collisional orogen; burial and ultimately prograde metamorphism were terminated sequentially by exhumation as a given part of the fold nappe came into contact with the lower plate, basement ramp (Baltica) and was driven upward. Burial, heating, exhumation, and cooling were thus diachronous within a single tectonic unit.

The Sulitjelma fold nappe represents part of a Caledonian marginal basin obducted during the closure of the Iapetus Ocean and collision between Laurentia and Baltica. Metamorphic pressure-temperature (P-T) paths indicate that various parts of the Sulitjelma fold nappe followed characteristic clockwise P-T paths involving prograde burial followed by prograde exhumation and then near-isothermal exhumation prior to cooling. Geochronological results indicate that foreland rocks followed this general P-T path before more hinterlandward rocks, such that foreland rocks underwent exhumation while hinterlandward rocks were still being buried. This is consistent with the fold nappe passing through a collisional orogen; burial and ultimately prograde metamorphism were terminated sequentially by exhumation as a given part of the fold nappe came into contact with the lower plate, basement ramp (Baltica) and was driven upward. Burial, heating, exhumation, and cooling were thus diachronous within a single tectonic unit.

Activation of sex steroid receptors is a key event in the regulation of uterine function. The expression of sex steroid receptors such as Oestrogen and Progesterone have been well characterised in normal human endometrial tissue. Expression of the androgen receptor (AR) has not been well characterised. The characterisation of AR in human endometrium is important to determine the role of androgens in physiological uterine events such as implantation and menstruation. The term "Intracrinology" refers to the ability of a peripheral target tissue to synthesise sex steroids. The expression pattern of metabolising enzymes determines a tissues steroidogenic potential. Key sex steroid metabolising enzymes include the 17β-hydroxysteroid dehydrogenases (17β -HSD), 5α-reductases (5αR), 3β-hydroxysteroid dehydrogenases (3β -HSD) and Aromatase. The objectives of this thesis were thus to determine in human endometrium; 1. The spatial and temporal expression of androgen receptor mRNA and protein in endometrium across the menstrual cycle. 2. The expression of critical androgen metabolising enzymes across the menstrual cycle - 17β -HSD type 2 mRNA and protein; 17β -HSD type 5 mRNA; 3β -HSD type 1 and 2 mRNA; and 5αR types 1 and 2 mRNA. 3. The spatial and temporal localisation, in endometrium exposed to high dose intra-uterine levonorgestrel, of AR mRNA and protein; 17β -HSD2 mRNA and protein; 17β -HSDS mRNA; 3β -HSD1 and 2 mRNA; and 5αRl and 2 mRNA. Endometrial biopsies from both normal endometrium and endometrium exposed to high dose intra-uterine levonorgestrel were subjected to optimised immunohistochemical protocols to determine the spatial and temporal immunolocalisation of the androgen receptor and 17β -HSD2. In-situ hybridisation (ISH) techniques were employed to localise AR mRNA in full thickness endometrial biopsies. Taqman real time RT-PCR examined the temporal variation in mRNA expression for AR; 17β -HSD2 and 5; 3β -HSD1 and 2; and 5aRl and 2 in normal endometrium and en

Activation of sex steroid receptors is a key event in the regulation of uterine function. The expression of sex steroid receptors such as Oestrogen and Progesterone have been well characterised in normal human endometrial tissue. Expression of the androgen receptor (AR) has not been well characterised. The characterisation of AR in human endometrium is important to determine the role of androgens in physiological uterine events such as implantation and menstruation. The term "Intracrinology" refers to the ability of a peripheral target tissue to synthesise sex steroids. The expression pattern of metabolising enzymes determines a tissues steroidogenic potential. Key sex steroid metabolising enzymes include the 17β-hydroxysteroid dehydrogenases (17β -HSD), 5α-reductases (5αR), 3β-hydroxysteroid dehydrogenases (3β -HSD) and Aromatase. The objectives of this thesis were thus to determine in human endometrium; 1. The spatial and temporal expression of androgen receptor mRNA and protein in endometrium across the menstrual cycle. 2. The expression of critical androgen metabolising enzymes across the menstrual cycle - 17β -HSD type 2 mRNA and protein; 17β -HSD type 5 mRNA; 3β -HSD type 1 and 2 mRNA; and 5αR types 1 and 2 mRNA. 3. The spatial and temporal localisation, in endometrium exposed to high dose intra-uterine levonorgestrel, of AR mRNA and protein; 17β -HSD2 mRNA and protein; 17β -HSDS mRNA; 3β -HSD1 and 2 mRNA; and 5αRl and 2 mRNA. Endometrial biopsies from both normal endometrium and endometrium exposed to high dose intra-uterine levonorgestrel were subjected to optimised immunohistochemical protocols to determine the spatial and temporal immunolocalisation of the androgen receptor and 17β -HSD2. In-situ hybridisation (ISH) techniques were employed to localise AR mRNA in full thickness endometrial biopsies. Taqman real time RT-PCR examined the temporal variation in mRNA expression for AR; 17β -HSD2 and 5; 3β -HSD1 and 2; and 5aRl and 2 in normal endometrium and en