Meteoric Input Research Articles

Mines to moana: Hydrochemical legacies in a historically mined watershed

This study investigates contemporary freshwater contamination originating from old mine workings in the Thames-Coromandel region of Te Ika-a-Māui (North Island), Aotearoa New Zealand. We employed a multi-method approach, including stable H and O isotope determinations of surface water, geochemical modelling, and diffusive gradients in thin films (DGT) deployments. Atypically, spring-summer (Sept–Nov) surface water stable oxygen isotope ratios (δ18O) were negatively displaced from meteoric values (ca. −0.28 ± 0.13 ‰), indicating a remarkable degree of low-temperature water-rock interaction, likely enhanced by dry antecedent conditions. Isotope ratios in tributaries showed less alteration than the main stem, suggesting greater meteoric inputs and shorter residence times in areas of high topographic relief. Conversely, in the main stem, isotope ratios revealed higher mineral weathering, accompanied by elevated dissolved metal concentrations, consistent with dominant inputs from shallow groundwater. Weathering of primary sulfides contributed pronounced acidity in one tributary (pH ca. 3.8), but overall, carbonate buffering ameliorated acid mine drainage across the catchment (pH ca. 7–8). Nevertheless, our results confirm exceedances of ecological guideline values (>80% protection threshold) for several toxic metals including Al, Zn, Cd and Pb; with implications for fresh and coastal water quality in Tikapa Moana-o-Hauraki, the Firth of Thames.

Mass Estimation From Simultaneous Optical and Radar Meteor Observations

AbstractThe total mass flux due to meteoric input is not well constrained and estimates vary greatly depending on the measurement technique used. The source of this discrepancy remains an open question in the field. Previous studies investigating the discrepancy by directly comparing mass estimates made using two techniques have been limited by extremely small sample sizes. This work presents a set of 166 meteors observed simultaneously by the MAARSY radar (53.5 MHz) and two nearby optical cameras. Independent masses are estimated using observations from both systems and compared against each other. The resulting mass estimates using both methods agree to within a factor of three on average. The results show two dominant trends: better agreement as meteoroid velocity increases and underestimation of the radar mass for the largest meteoroids observed (>10 mg). These trends had not been quantified by previous studies limited by very small sample sizes, and could help to explain the historic discrepancy between mass estimates by different systems. The general agreement between the radar and photometric masses indicates that both methods perform well independently, and can reliably be applied to radar or optical observations without restriction of simultaneous observations by two systems.

Silica Geothermometry Studies of Shallow Aquifer in Kelantan

The study aimed to analyze the spatial and temporal distribution of silica concentrations in shallow quaternary aquifers across Kelantan, Malaysia. This assessment was crucial for understanding groundwater dynamics, including residence times and potential contamination sources. A total of 32 (29 groundwater and 03 surface water) samples were collected during both pre-monsoon and post-monsoon periods in 2016. Silica concentrations ranged from 6.3 mg/l to 23.4 mg/l pre-monsoon and 6.2 mg/l to 23.5 mg/l post-monsoon. Silica geo-thermometry, based on the chalcedony equation, estimated temperatures ranging from 3.09°C to 37.61°C pre-monsoon and 0.90°C to 37.79°C post-monsoon. Under typical geothermal conditions with an average heat flow of 30°C/km, these temperatures corresponded to depths ranging from 0.02 km to 0.32 km pre- monsoon and 0.01 km to 0.32 km post-monsoon. The shallow depths (less than 0.32 km) indicate relatively rapid groundwater circulation, which aligns with the observed low silica concentrations. These findings suggest minimal anthropogenic influence and short residence times, emphasizing recent meteoric input and surface water inflow as dominant factors shaping water quality in the area.

Geochemical approach for decoding the paleoenvironmental and depositional evolution of a coastal lacustrine Konservat-Lagerstätte (Early Cretaceous, south-Central Pyrenees)

The lithographic limestone of La Pedrera de Meià (LPM) in south-Central Pyrenees (NE Spain) is considered one of the best preserved lacustrine-coastal successions of the Early Cretaceous in Europe, hosting a taxonomically diverse record of Barremian biota. While this Konservat-Lagerstätte has been extensively surveyed for paleontological purposes, little is known about the paleoenvironmental and depositional conditions prevailing during the formation of this fossil lagerstätte deposit. LPM limestone is made up of a homogeneous, dark gray to pale brown, faintly laminated 50 m-thick succession of micrite-rich intervals. To shed light on the environmental conditions of deposition, 303 rock samples were studied using a multiproxy approach based on different techniques including petrography, SEM-EDX, XRD, ICP-MS, XRF, Rare Earth Element distributions and C and O stable isotope geochemistry. The combination of sedimentological and geochemical data reveals a vertical shift of facies from littoral to profundal environments and then returning to littoral conditions. Profundal facies are made up of filament-rich mudstones originated from in situ precipitation of micrite either through biotically mediated or physico-chemical processes in undisturbed low energy settings, under anoxic conditions, characterized by the presence of transported terrestrial and lacustrine organisms that are exquisitely well-preserved. Littoral areas are characterized by the presence of in situ charophytes, smooth ostracods, and miliolid foraminifera that accumulated in mud-rich facies indicating low/moderate-energy, shallow-water, and relatively oxygenated conditions. Stable isotopic data and elemental geochemistry suggest a hydrologically closed to semi-closed lacustrine system with a restricted water circulation encouraging dysoxic to anoxic conditions in profundal sediments. Paleoproductivity proxies suggest a good correlation between catchment-derived siliciclastic discharge to the lake and primary productivity peaks. Furthermore, a decline in terrigenous input coupled with a reduction of meteoric water entrance to the lake is interpreted based on elemental proxies derived from paleosalinity and paleoredox analysis. Collectively, the strontium/barium (Sr/Ba) ratios, the sparse presence of miliolid foraminifera, and the isotopic signatures indicate an increase in salinity toward the younger intervals of the lake infilling, although their ultimate causes are unclear (i.e., increased evaporation, or a combination of reduced meteoric input and sporadic marine inputs might explain our data). The present work shows the importance of performing detailed multiproxy geochemical-sedimentological studies to better constrain the unique paleoenvironmental and paleohydrological conditions associated with the exceptional preservation of fossil biotas in Konservat-Lagerstätte deposits in analogous depositional settings.

Control on carbonate reservoir properties along a shallowing-upward sequence: The middle oxfordian jura inner platform predictive model

The study of the Bonnevaux section from the Middle Oxfordian Jura inner platform (France) highlights that a shallowing-upward sequence showing a large variability of original microfacies linked to various depositional environments (open sea to lagoon) can be exclusively composed of microporous limestones. A spatial evolution of reservoir qualities and transport properties of these microporous limestones is recognized at the platform scale: a correlated increase in total porosity (from 2.8 to 21.3%) and permeability (from 0.0001 to 16 mD) and a decrease in trapped porosity (from 100 to ∼50%) is observed from the upper offshore to the back-shoal lagoon environments. The increase in permeability observed at the platform scale is correlated with an evolution of the unimodal distribution of pore access radii and an increase in threshold radius (from 0.033 to 0.570 μm). It results from a diachronism in the control of meteoric pore-fluid flows by the microporosity (vs macroporosity) during the burial diagenesis. A later control of meteoric pore-fluid flows by the microporosity related to differences in cementation (1) reduces the fluid-rock interactions in the micrite areas and consequently promotes open fabrics with larger pore access radii and (2) allows to preserve larger pore access radii in the intercrystalline pore network of cements. In the case of reservoir qualities, this later control (1) promotes a higher total porosity in the micrite areas in relation with more open fabrics and (2) allows to preserve larger pore access inducing a lower trapped porosity. The macroporosity can played a key role when the blocky cementation of the pore space is partial. This study also reveals that a submarine lithification can prevent the petrophysical impact of a pore-fluid meteoric input during the burial diagenesis.

Geochemical insights from formation waters produced from Wolfcampian and Leonardian intervals of the Midland Basin, Texas, USA

The lower Permian of the Midland Basin of West Texas consists of mudrocks with some tight sandstones and carbonate-dominated intervals (Wolfcamp and Spraberry formations) averaging a thickness of 975 m (3200 ft). They have been the target of a large revitalization of oil and gas production from the basin using hydraulic fracturing stimulation and horizontal well technology. Little is known about the aqueous geochemistry of these intervals. We sampled produced formation water from 53 wells across the basin and put them in the context of the basin flow history. Analyzing for major and minor elements and stable water and strontium isotopes, we determined that: (1) TDS values vary from 72 to 135 g/L, decreasing with increasing depth and increasing stratigraphic age; (2) ionic composition is consistent with that of Na–Cl brines found elsewhere in the basin with no major impact of meteoric input or halite dissolution as sometimes seen in the Permian Basin; (3) stable water isotopes (δ18O +5.0 ± 2.0‰ and δ2H −28 ± 5‰ VSMOW) are enriched; slightly radiogenic 87Sr/86Sr ratio is consistent with local carbonates. Interpretative results suggest that the modern resident brines of the low-permeability Lower Permian originated as Permian evaporative brines coeval with Upper Permian thick halite deposition. They would have dolomitized Permian carbonates in their gravity-driven downward migration and been further modified through water-rock interactions, including smectite-illite conversion.

Martian Meteoric Mg+: Atmospheric Distribution and Variability From MAVEN/IUVS

AbstractSince the discovery of atmospheric Mg+ on Mars in 2015 by the Mars Atmosphere and Volatile Evolution mission, there have been almost continuous observations of this meteoric ion layer in a variety of seasons, local times, and latitudes. Here, we present the most comprehensive set of observations of the persistent metal ion layer at Mars, constructing the first grand composite maps from pooled medians of subsamples of a metallic ion species. These maps demonstrate that Mg+ appears in almost all conditions when illuminated, with peak density values varying between 100 and 500 cm−3, dependent on season and local time. There exists significant latitudinal variation within a given season, indicating that Mg+ is not simply an inert tracer, but may instead be influenced by the meteoric input distribution and/or atmospheric dynamics and chemistry. Geographic maps of Mg+ density as a function of latitude and longitude indicate the influence of atmospheric tides, and there is no apparent correlation with remnant crustal magnetic fields. This work also presents counter‐intuitive results, such as a reduction of Mg+ ions in the northern hemisphere during Northern Winter in an apparent correlation with dust aerosols.

The origin and transfer of water and solutes in peatlands: A multi tracer assessment in the carbonated Jura Mountains

AbstractPeatlands provide a large panel of socio‐ecosystemic services such as biodiversity, water and carbon storage and amenities. Hydrological and geochemical interactions between peats and their surroundings are expected to be favoured in mountainous areas, which are nowadays increasingly sensitive to climate changes. In order to provide an integrated scheme of potential interactions, this study evaluates spatio‐temporal patterns of environmental tracers (87Sr/86Sr, δ18O/δ2H, elemental ratios) during high‐ and low‐flow periods in the largest peatland complex of the Jura Mountains (France). Systematically depleted δ18O/δ2H values in the deepest peat pore waters suggest contrasted dynamics and origins, both compatible with either preferential winter recharge or supply from adjacent high‐elevation areas. Combined with strontium isotopes (87Sr/86Sr), we show that these water fluxes are purveyors of solutes derived from water‐rock interactions, modified by mixing, evapotranspiration and dilution with local meteoric inputs. An end member mixing analysis of the peat pore water solute composition is consistent with a major contribution of carbonates from the regional Cretaceous limestone formations, located beneath fluvio‐glacial Quaternary deposits underlying the peat. This contribution implies a significant upward water flux from the underlying syncline that could reach a sufficient hydraulic head thanks to recharge from an adjacent regional anticline. These multiscale (anticline‐syncline, syncline‐peatland, peatland‐surface) constraints allow us to propose a relevant scheme for the hydrogeochemical functioning of the peatland, enabling an improved understanding of the current high socio‐ecosystemic value of the area, and the potential future evolution of the related services.

Deep submarine infiltration of altered geothermal groundwater on the south Chilean Margin

Submarine groundwater discharge is increasingly recognized as an important component of the oceanic geochemical budget, but knowledge of the distribution of this phenomenon is limited. To date, reports of meteoric inputs to marine sediments are typically limited to shallow shelf and coastal environments, whereas contributions of freshwater along deeper sections of tectonically active margins have generally been attributed to silicate diagenesis, mineral dehydration, or methane hydrate dissociation. Here, using geochemical fingerprinting of pore water data from Site J1003 recovered from the Chilean Margin during D/V JOIDES Resolution Expedition 379 T, we show that substantial offshore freshening reflects deep and focused contributions of meteorically modified geothermal groundwater, which is likely sourced from a reservoir ~2.8 km deep in the Aysén region of Patagonia and infiltrated marine sediments during or shortly after the last glacial period. Emplacement of fossil groundwaters reflects an apparently ubiquitous phenomenon in margin sediments globally, but our results now identify an unappreciated locus of deep submarine groundwater discharge along active margins with potential implications for coastal biogeochemical processes and tectonic instability.

Phosphorus Chemistry in the Earth's Upper Atmosphere

AbstractThe ablation of phosphorus from interplanetary dust particles entering the Earth's atmosphere is a potentially significant source of this key bioelement. In this study, the atmospheric chemistry of phosphorus is explored by developing a reaction network of possible routes from PO, the major ablation product in the upper mesosphere/lower thermosphere region, to the stable reservoirs H3PO3 and H3PO4 that become incorporated into meteoric smoke particles (MSPs) as metal phosphites and phosphates, respectively. The network is constructed with reactions whose kinetics have been measured experimentally, together with reactions where theoretical rate coefficients are estimated using a combination of electronic structure theory calculations and a Rice‐Ramsperger‐Kassel‐Markus master equation treatment. The network is then incorporated into a global chemistry‐climate model, together with a phosphorus meteoric input function. The estimated global mean P deposition flux, in the form of submicron‐sized MSPs, is 1 × 10−8 g m−2 yr−1, with a maximum of ∼5 × 10−8 g m−2 yr−1 over the northern Rockies, Himalayas, and southern Andes. The estimated fraction of ablated phosphorus forming bioavailable metal phosphites is 11%, which results from the very large concentrations of O and H compared to OH in the upper mesosphere. A layer of OPO is predicted to occur at 90 km with a peak of concentration of ∼50 cm−3; this is the counterpart of the well‐known layers of meteoric metals such as Na and Fe, and may be observable spectroscopically.

A Pulse of Meteoric Subsurface Fluid Discharging Into the Chukchi Sea During the Early Holocene Thermal Maximum (EHTM)

AbstractThe response of Arctic Ocean biogeochemistry to subsurface flow driven by permafrost thaw is poorly understood. We present dissolved chloride and water isotopic data from the Chukchi Sea Shelf sediments that reveal the presence of a meteoric subsurface flow enriched in cations with a radiogenic Sr fingerprint. This subsurface fluid is also enriched in dissolved inorganic carbon and methane that bear isotopic compositions indicative of a carbon reservoir modified by reactions in a closed system. Such fluid characteristics are in stark contrast with those from other sites in the Chukchi Sea where the pore water composition shows no sign of meteoric input, but reflect typical biogeochemical reactions associated with early diagenetic sequences in marine sediment. The most likely source of the observed subsurface flow at the Chukchi Sea Shelf is from the degradation of permafrost that had extended to the shelf region during the Last Glacial Maximum. Our data suggest that the permafrost‐driven subsurface flow most likely took place during the 2–3°C warming in the Early Holocene Thermal Maximum. This time scale is supported by numerical simulation of pore water profiles, which indicate that a minimum of several thousand years must have passed since the cessation of the subsurface methane‐bearing fluid flow.

Meteor‐Ablated Aluminum in the Mesosphere‐Lower Thermosphere

AbstractThe first global atmospheric model (WACCM‐Al) of meteor‐ablated aluminum was constructed from three components: The Whole Atmospheric Community Climate Model (WACCM6); a meteoric input function for Al derived by coupling an astronomical model of dust sources in the solar system with a chemical meteoric ablation model; and a comprehensive set of neutral, ion‐molecule and photochemical reactions relevant to the chemistry of Al in the upper atmosphere. The reaction kinetics of two important reactions that control the rate at which Al+ ions are neutralized were first studied using a fast flow tube with pulsed laser ablation of an Al target, yielding k(AlO+ + CO) = (3.7 ± 1.1) × 10−10 and k(AlO+ + O) = (1.7 ± 0.7) × 10−10 cm3 molecule−1 s−1 at 294 K. The first attempt to observe AlO by lidar was made by probing the bandhead of the B2Σ+(v′ = 0) ← X2Σ+(v″ = 0) transition at λair = 484.23 nm. An upper limit for AlO of 60 cm−3 was determined, which is consistent with a night‐time concentration of ∼5 cm−3 estimated from the decay of AlO following rocket‐borne grenade releases. WACCM‐Al predicts the following: AlO, AlOH and Al+ are the three major species above 80 km; the AlO layer at mid‐latitudes peaks at 89 km with a half‐width of ∼5 km, and a peak density which increases from a night‐time minimum of ∼10 cm−3 to a daytime maximum of ∼60 cm−3; and that the best opportunity for observing AlO is at high latitudes during equinoctial twilight.

Fluid and ore-material source of the Xiajiaxiaohe gold deposit in central Yishu fault zone in Shandong, Eastern China

The Xiajiaxiaohe gold deposit is located in the middle section of the central Yishu fault zone in Shandong Province (Eastern China). Previous studies mainly focused on the relations between the fault zone and gold mineralization; yet, its mineralization process was rarely studied, which hinders further exploration and deposit model development. In this study, we analyzed the trace elements and He-Ar isotopes of the auriferous pyrite and determined the source(s) and nature of ore-forming fluids and materials. Rare earth element (REE) compositions of the pyrite indicate that the ore-forming materials at Xiajiaxiaohe were sourced from the Yishui Group wallrocks. The Co-Ni contents and Co/Ni ratios show that the Xiajiaxiaohe gold mineralization was formed under medium- to low-temperature conditions. Fluid inclusions in pyrite have 3He/4He (0.14–0.20 Ra) and 40Ar/36Ar (1038–1290) ratios reflecting a crust source for the ore-forming fluids. The fluids may have then undergone varying degree of interactions with a deep-mantle source, plus minor meteoric input during the Mesozoic Pacific subduction beneath the Eurasian plate.

The Meteoric Ni Layer in the Upper Atmosphere

AbstractThe first global atmospheric model of Ni (WACCM‐Ni) has been developed to understand recent observations of the mesospheric Ni layer by ground‐based resonance lidars. The three components of the model are: the Whole Atmospheric Community Climate Model (WACCM6); a meteoric input function derived by coupling an astronomical model of dust sources in the solar system with a chemical meteoric ablation model; and a comprehensive set of neutral, ion‐molecule, and photochemical reactions pertinent to the chemistry of Ni in the upper atmosphere. In order to achieve closure on the chemistry, the reaction kinetics of three important reactions were first studied using a fast flow tube with pulsed laser ablation of a Ni target, yielding k(NiO + O) = (4.6 ± 1.4) × 10−11, k(NiO + CO) = (3.0 ± 0.5) × 10−11, and k(NiO2 + O) = (2.5 ± 1.2) × 10−11 cm3 molecule−1 s−1 at 294 K. The photodissociation rate of NiOH was computed to be J(NiOH) = 0.02 s−1. WACCM‐Ni simulates satisfactorily the observed neutral Ni layer peak height and width, and Ni+ measurements from rocket‐borne mass spectrometry. The Ni layer is predicted to have a similar seasonal and latitudinal variation as the Fe layer, and its unusually broad bottom‐side compared with Fe is caused by the relatively fast NiO + CO reaction. The quantum yield for photon emission from the Ni + O3 reaction, observed in the nightglow, is estimated to be between 6% and 40%.

Interaction of photoionisation and meteoric input in the atmosphere of Jupiter

Interplanetary dust grains and meteoroids are assumed to deliver oxygen to the atmosphere of Jupiter. A current photochemical model overestimates the resultant density of water relative to an available measurement. This paper investigates whether the interaction of photoionisation and meteoric products can explain that discrepancy. As any process that breaks up water molecules is likely to produce hydroxyl, the predicted densities of hydroxyl are also investigated as a possible target for remote sensing. It is found that the densities of water are not changed by the addition of photoionisation, but that higher OH densities are predicted above about 400 km.

Stable and Radioisotope Systematics Reveal Fossil Water as Fundamental Characteristic of Arid Orogenic‐Scale Groundwater Systems

AbstractIn arid and semiarid regions, persistent hydrological imbalances illuminate the considerable gaps in our spatiotemporal understanding of fundamental catchment‐scale governing mechanisms. The Salar de Atacama basin is the most extreme example of groundwater‐dominated continental basins and therefore is an ideal place to probe these unresolved questions. Geochemical and hydrophysical observations indicate that groundwaters discharging into the basin reflect a large regional system integrated over 102–104 year timescales. The groundwater here, as in other arid regions, is a critical freshwater resource subject to substantial demand from competing interests, particularly as development of its world‐class lithium brine deposit expands. Utilizing a uniquely large and comprehensive set of H and O isotopes in water, we demonstrate that much of the presumed recharge area on the Altiplano‐Puna plateau exhibits isotopic signatures quite distinct from waters presently discharging within the endorheic Salar de Atacama watershed. δ18O values of predicted inflow source waters are 3.6‰ to 5.6‰ higher than modern plateau waters, and 3H data from 87 discrete samples indicate that nearly all of this inflow is composed of premodern recharge (i.e., fossil water). Under plausible conditions, these distinctions cannot be explained solely by natural variability in modern meteoric inputs or by steady state groundwater flow. We present a conceptual model revealing the extensive influence of transient draining of fossil groundwater storage augmented by regional interbasin flow from the Andes. Our analysis provides robust constraints on fundamental mechanisms governing this arid continental groundwater system and a framework within which to address persistent uncertainties in similar systems worldwide.

Groundwater Isotopes Biased Toward Heavy Rainfall Events and Implications on the Local Meteoric Water Line

AbstractStable water isotopes are useful tracers in the groundwater recharge studies, where the local meteoric water line (LMWL) usually serves as a reference line and the amount‐weighted average value of precipitation is regarded as the input meteoric signal. Based on a comparison of isotope composition between precipitation and groundwater collected from a groundwater basin in the Beijing area, we verify that small precipitation events do not constitute effective groundwater recharge in a (semi) arid region, causing that the isotopes in groundwater are biased toward the meteoric isotopic signal of heavy rainfall events. The positive deflections in groundwater levels from a phreatic aquifer in Yanqing Basin in the Northwest of Beijing revealed that recharge occurs exclusively during the rainy seasons and is clearly associated with heavy rainfall events (>10 mm/day). The isotope composition of groundwater samples that plot far below the mean meteoric input value, further strengthen the dependence of groundwater recharge on heavy rainfall events. We construct the LMWLs with different regression methods using daily stable isotope data from seven hydro‐meteorological stations over a hydrological year. When the δ18O ranges from −20‰ to 10‰, the lines are quite similar regressed by the weighted monthly values and by heavy rainfall events, so the conventional LMWL can still serve as the reference line for groundwater recharge studies.

A stable isotope record of Holocene precipitation dynamics in the Baltic region from Lake Nuudsaku, Estonia

A long-term perspective of past hydroclimate variability for the Baltic region provides important context for evaluating the potential impacts of Northern Hemisphere temperature changes and shifting ocean-atmospheric interactions on northern European climate. Lake Nuudsaku is an open-basin lake in south-central Estonia with seasonal overflow fed by active springs and groundwater. Stable isotope analyses of surface water samples from regional lakes, rivers, wetlands, and precipitation indicate that Lake Nuudsaku water δ18O values are consistent with the isotopic composition of inflowing meteoric water. The isotopic composition of fine-grained (<63 μm) endogenic CaCO3 (δ18Ocalcite) samples from Lake Nuudsaku vary between ∼14 to -9‰ (VPBD) over the last ∼9400 years. Based on sensitivity tests, we interpret the δ18Ocalcite variations from Lake Nuudsaku as a record of meteoric inputs; principally reflecting variations in the seasonality of precipitation, with temperature changes as a secondary influence. The δ18Ocalcite record indicates the early Holocene at ∼9400 calendar years before present (cal yr BP) was characterized by a high proportion of cold season (November through April) precipitation and lower temperatures, followed by waning cold season precipitation and higher temperatures until ∼8200 cal yr BP. The middle Holocene (8200–4200 cal yr BP) was likely a period of overall reduced cold season precipitation and higher temperatures, and/or increased warm season (May through October) precipitation. The late Holocene transition at ∼4200 cal yr BP generally marks a shift to lower δ18Ocalcite values that we interpret largely the result of increased cold season precipitation amounts. This was followed by the onset of more variable precipitation amounts and temperatures after ∼3600 cal yr BP, which gave way to less variable conditions during the last ∼2600 years. The Medieval Climate Anomaly (MCA) is marked by δ18Ocalcite values that are near the Holocene and present-day averages. The period spanning the Little Ice Age (LIA) is marked by low δ18Ocalcite values, suggesting temperatures were lower and cold season conditions were wetter than present-day. Proxy evidence from Lake Nuudsaku further indicates that centennial to millennial-scale hydroclimate shifts in the Baltic region were likely associated with changes in North Atlantic ocean-atmospheric circulation dynamics.

Results of the first continuous meteor head echo survey at polar latitudes

We present the first quasi continuous meteor head echo measurements obtained during a period of over two years using the Middle Atmosphere ALOMAR Radar System (MAARSY). The measurements yield information on the altitude, trajectory, vector velocity, radar cross section, deceleration and dynamical mass of every single event. The large statistical amount of nearly one million meteor head detections provide an excellent overview of the elevation, altitude, velocity and daily count rate distributions during different times of the year at polar latitudes. Only 40% of the meteors were detected within the full width half maximum of the specific sporadic meteor sources. Our observation of the sporadic meteors are compared to the observations with other radar systems and a meteor input function (MIF). The best way to compare different radar systems is by comparing the radar cross section (RCS), which is the main detection criterion for each system. In this study we aim to compare our observations with a MIF, which provides information only about the meteoroid mass. Thus, we are using a statistical approach for the elevation and velocity dependent visibility and a specific mass selection. The predicted absolute count rates from the MIF are in a good agreement with the observation when it is assumed that the radar system is only sensitive to meteoroids with masses higher than one microgram. The analysis of the dynamic masses seems to be consistent with this assumption since the count rate of events with smaller masses are low and decrease even more by using events with relatively small errors.

Geochemistry of trace elements in spring waters of the Lourdes area (France)

Geochemical studies on the waters of four springs, including the Massabielle (MS) Spring, were carried out at Lourdes (France) following a long, rainless and warm period, with the aim of at least documenting the groundwater chemistry that was affected by the current meteoric input. The existence of anecdotal reports about anomalously elevated concentrations of trace constituents in the water of the MS Spring in the absence of any detailed studies inspired these first geochemical investigations of trace elements in the spring waters at Lourdes. The main common features of waters from the four springs studied in Lourdes are low total dissolved solids (255–318 mg/L), a slightly alkaline pH (7.50–7.68), oxidizing conditions (E H = 458–472 mV), similar temperatures (11.3–13.1 °C), and their Ca-HCO 3 hydrochemical type, all of which are typical characteristics for an active zone within a hydrogeological system that is developed in carbonate-dominated bedrock. The spring waters, which represent an active turnover zone in the hydrogeological system, are only in partial chemical equilibrium with the minerals of the aquifer rocks. The enrichment of the MS Spring water with numerous elements (Li, Na, Cs, Ba, S, F, Br, REE, B, Sb and Bi), when compared with other springs studied and with the bedrock geochemistry, probably is caused by contributions from fluids (originating from the Pyrenees basement and/or from Triassic saliferous deposits) in the formation of the hydrogeochemical content of the zone under investigation. The germanium concentration in all of the waters studied was significantly lower than the concentrations typically found in fresh groundwater in the active zone; accordingly, the hypothesis concerning an anomalously high concentration of this element in the MS Spring water was invalidated. The preliminary geochemical research presented is part of an interdisciplinary geochemical-biological-tensiometric study of the spring waters at Lourdes.