Bedrock Geology Research Articles

Trace Element Geochemistry of Alluvial TiO2 Polymorphs as a Proxy for Sn and W Deposits

The Segura mining field, the easternmost segment of the Góis–Panasqueira–Segura tin–tungsten metallogenic belt (north–central Portugal), includes Sn-W quartz veins and Li-Sn aplite-pegmatites, which are believed to be genetically related to Variscan Granites. Sediment geochemistry indicates granite-related Ti-enrichments, locally disturbed by mineralization, suggesting magmatic and metamorphic/metasomatic titaniferous phases. Therefore, Segura alluvial samples and the geochemistry of their TiO2 polymorphs (rutile, anatase, and brookite) were investigated, and their potential as exploration tools for Sn and W deposits was evaluated. The heavy-mineral assemblages proved to be good proxies for bedrock geology, and TiO2 polymorph abundances were found to be suitable indicators of magmatic and/or metasomatic hydrothermal processes. The trace element geochemistry of Segura’s alluvial rutile, anatase, and brookite is highly variable, implying multiple sources and a diversity of mineral-forming processes. The main compositional differences between TiO2 polymorphs are related to intrinsic (structural) factors, and to the P-T-X extrinsic parameters of their forming environments. Anomalous enrichments, up to 9% Nb, 6% Sn and W, 3% Fe, 2% Ta, and 1% V in rutile, and up to 1.8% Fe, 1.7% Ta, 1.2% Nb, 1.1% W 0.5% Sn and V in anatase, were registered. Brookite usually has low trace element content (<0.5%), except for Fe (~1%). HFSE-rich and granitophile-rich rutile is most likely magmatic, forming in extremely differentiated melts, with Sn and W contents enabling the discrimination between Sn-dominant and W-dominant systems. Trace element geochemical distribution maps show pronounced negative Sn (rutile+anatase) and W (rutile) anomalies linked to hydrothermal cassiterite precipitation, as opposed to their hydrothermal alteration halos and to W-dominant cassiterite-free mineralized areas, where primary hydrothermal rutile shows enrichments similar to magmatic rutile. This contribution recognizes that trace element geochemistry of alluvial TiO2 polymorphs can be a robust, cost- and time-effective, exploration tool for Sn(W) and W(Sn) ore deposit systems.

The abnormally large “hushes” of Teesdale, North Pennines, England: Differentiating mining legacy and natural landforms in glaciated Carboniferous bedrock terrain

The unusually large, steep-sided gullies and gorges incised into bedrock at Coldberry Gutter and Pike Law in Teesdale in the North Pennines are traditionally associated with ‘hushing’, a hydraulic mining process designed to gain access to lead-bearing veins. However, it is difficult to reconcile the size and form of these features, as well as the bedrock geology, entirely with a hushing origin. Instead, it is proposed that these landforms originated naturally on valley sides and interfluves through a combination of karstification, spring sapping, steephead evolution, fluvial slope channel enlargement, landsliding and meltwater channel erosion, which preferentially developed in fault and mineralised zones. The practices of hushing and quarrying then targeted the natural bedrock exposures for the extraction of visible mineralised materials, which were small and locally workable orebodies that would likely have led the way to the discovery of much more substantial mineralised ground and then subsequent adit excavation in adjoining areas. Large numbers of leats and hushing dams were constructed above and around Coldberry Gutter and Pike Law and were used to enlarge some engineered trenches/gullies (hushes), but were mostly too small to account for the excavation of the substantial volumes of bedrock necessary to create the largest incisions. Volume calculations on the alluvium located at the base of the incisions, likely to contain all the waste rock from the hushing process, are also incompatible with the total sizes of the proposed excavations; additional rock waste contained in spoil tips are composed of material excavated directly from adits within the gulleys and gorges. It appears that engineered reservoirs and leats were employed mostly to clear out waste material, wash processed rock and contribute to hydro-power activities in the larger gullies and gorges. Some of the most intensive hushing activity is in the surficial (Late Pleistocene and Holocene) deposits laid down by glaciation and postglacial fluvial processes, suggesting that it was employed also as a placer mining technique.

Dust sources in Westernmost Asia have a different geochemical fingerprint to those in the Sahara

Dust is an important component of Earth's climate system, directly affecting the global radiation budget and hydrological cycle. The interaction of aerosols with clouds and its impact on regional and global energy budgets remains one of the largest sources of uncertainty in climate model predictions. Records of terrigenous dust accumulation in geological archives also provide a potentially powerful way to assess past changes in hydroclimate. Western Asia, including the Arabian Peninsula, is second only to the Saharan Desert in contributing dust to the global atmosphere. Yet, while satellite-derived maps of dust source activation frequency (DSAF) provide an increasingly granular understanding of the different dust sources within these regions today, our ability to fingerprint their windblown contributions to geological archives is rudimentary, severely limiting the use of dust-based records to reconstruct past changes in continental hydroclimate. A main limitation is a poor understanding of the mineralogical and geochemical composition of the bedrock geology and, more importantly, of the readily deflated unconsolidated sediments in these regions. Here we use published data to produce a DSAF map, centred on the Arabian Peninsula and extending from North Africa to Western Asia (∼40-10 °N; ∼25–65 °E), and we present new radiogenic isotope (Sr and Nd) data from unconsolidated surface sediment samples at active dust-producing sites. We combine our new Sr and Nd data with sparse data on sediments from the literature and the DSAF data to define three new preferential dust source areas (PSAs) in Westernmost Asia: (i) the central belt of the Arabian Peninsula, (ii) the Southern Levant and (iii) Mesopotamia. All three of these PSAs are geochemically distinct from Saharan dust sources. Long-range sediment transport by the Blue Nile and its tributaries, and the Tigris-Euphrates river systems exerts a strong influence on the geochemical fingerprints of dust sources in the Eastern Sahara and Mesopotamia, respectively. The isotopic signature of active dust sources in the central belt of the Arabian Peninsula shows only modest correspondence to underlying bedrock geology suggesting wide scale mixing by aeolian transport internally and/or a weak imprint of palaeo humidity (e.g. localized river reactivation) on dust source composition in comparison to the Eastern Sahara. Our results provide surer foundations for fingerprinting the sources of continental dust accumulating in marine, lacustrine, speleothem and ice archives, an important step in improving our understanding of Quaternary rainfall climate in arguably the most water-stressed region on Earth.

Lateritic processes in Madagascar and the link with agricultural and socioeconomic conditions

Madagascar hosts a youthful landscape atop old bedrock geology. Observed rapid surface uplift – possibly a consequence of sub-plate mantle plume activity – does not fit the concept of “The Red Island”, i.e. thick piles of laterite, formed by slow chemical weathering that requires prolonged periods of tectonic quiescence. Here, we document the results of a three-year field campaign in which we sought to interrogate and decouple the climatic and tectonic drivers behind laterite formation, and establish a tentative link to agricultural productivity, which may reinforce local levels of poverty. We installed 45 rain gauges and merged their data with a satellite precipitation product to develop a new high-resolution climatology. We also collected 11 sediment samples from which we established 10Be-derived erosion rates; and measured laterite/saprolite thickness at 60 localities. The thickest lateritic profiles coincide with a narrow band of annual rainfall, suggesting that laterite evolution processes co-evolved with climate changes. Laterite thickness correlates negatively with erosion rate, and strongly positively with the headcount index of poverty. In the absence of agricultural technology, we propose a direct link between the local prevalence of lateritic soil and poor agricultural productivity. We also suggest that the spatial distribution of uplift/erosion and precipitation governs the distribution and thickness of laterite. Uplift and erosion rates vary dramatically over small distances, restricting the development of thick laterite to two small patches that straddle the central Hauts Plateaux.

Decadal trends in solute concentrations, mass flux, and discharge reveal variable hydrologic and geochemical response to climate change in two alpine watersheds

High-alpine environments are particularly sensitive to changes driven by climate change and experience more dramatic shifts in vegetation, snowmelt timing, and the relative ratio of rain to snow compared to other lower-elevation environments. These shifts drive changes in stream discharge and solute concentrations, long-term records of which may be archived in publicly available databases. Here, we use three decades of discharge and water quality data from two alpine watersheds along the Continental Divide in the Rocky Mountains of Colorado, USA, to quantify temporal trends in solute concentration and solute mass flux, which serve as integrators of watershed processes and are used to identify controls on how these watersheds respond to climate change over decadal timescales. By analyzing both solute concentrations and mass flux we are able to remove the effects of seasonal changes in discharge and separate hydrologic and geochemical drivers of changes in solute export from these two watersheds. While we find that concentrations of calcium, bicarbonate, and sulfate increase through time in both watersheds, increasing solute mass flux is found in one watershed but not the other, despite similar watershed characteristics such as elevation, precipitation, average temperature, and bedrock geology. We identify different dominant weathering mechanisms as the cause for the differences in watershed response to climate change. In one watershed, sulfide oxidation was the dominant weathering mechanism at the beginning of the record and stayed dominant through the three-decade period of data. This consistency in weathering mechanism likely controls why the solute flux did not change significantly. In contrast, in the other watershed, solute flux increased and water chemistry shows that the dominant weathering mechanism shifted from dominantly CO2-driven to more influence from sulfide-oxidation driven weathering. This shift in weathering mechanism is accompanied by significantly increasing solute fluxes. This study demonstrates the importance of quantifying geological weathering in watershed response to climate change where two similar watersheds exhibit different responses--one hydrological and one combined hydrological and geochemical--that could not have been predicted from a simple analysis of the watershed characteristics. Such analyses are needed on a large scale to quantify the type and magnitude of watershed changes in water quality and quantity to climate change, and suggest that weathering mechanisms, in particular weathering driven by oxidation of trace sulfide minerals, plays an important role in the geochemical response of watersheds to climate change.

Using geogenic radon potential to assess radon priority area designation, a case study around Castleisland, Co. Kerry, Ireland

Globally, indoor radon exposure is the leading cause of lung cancer in non-smokers and second most common cause after tobacco smoking. Soil-gas radon is the main contributor to indoor radon, but its spatial distribution is highly variable, which poses certain challenges for mapping and predicting radon anomalies. Measurement of indoor radon typically takes place over long periods of time (e.g. 3 months) and is seasonally adjusted to an annual average concentration. In this article we investigate the suitability of using soil-gas radon and soil-permeability measurements for rapid radon risk assessments at local scale. The area of Castleisland, Co. Kerry was chosen as a case study due to availability of indoor radon data and the presence of significant radon anomalies. In total, 135 soil-gas and permeability measurements were collected and complemented with 180 indoor radon measurements for an identical 6 km2 area. Both soil-gas and indoor radon concentrations ranged from very low (<10 kBqm−3, 0.1 Bqm−3) to anomalously high (>1433 kBqm−3, 65,000 Bqm−3) values. Our method classifies almost 50% of the area as a high radon potential area, and allows assessment of geogenic controls on radon distribution by including other geological variables. Cumulatively, the percentage of indoor radon variance explained by soil-gas radon concentration, bedrock geology, subsoil permeability and Quaternary geology is 34% (16%, 10%, 4% and 4% respectively). Soil-gas and indoor radon anomalies are associated with black shales, whereas the presence of karst and geological faults are other contributing factors. Sampling of radon soil-gas and soil permeability, used in conjunction with other geogenic data, can therefore facilitate rapid designation of radon priority areas. Such an approach demonstrates the usefulness of high-resolution geogenic maps in predicting indoor radon risk categories when compared to the application of indoor radon measurements alone. This method is particularly useful to assess radon potential in areas where indoor radon measurements are sparse or lacking, with particular application to rural areas, land rezoned for residential use, or for sites prior to building construction.

Constraints for the Vs profiles from engineering-geological qualitative characterization of shallow subsoil in seismic microzonation studies

A statistical analysis has been performed aiming at determining to what extent a qualitative engineering-geological characterization of subsoil may provide constraints to the shear wave velocity (Vs) profile. For this purpose, a large database of experimental values provided by seismic microzonation studies carried out in the last 10 years in Italy has been considered. This analysis suggests that statistical constraints can be provided to Vs values as a function of depth by considering main lithological characteristics of cover terrains and geological bedrock. The effectiveness and unbiasedness of resulting relationships are tested against some experimental situations. This information can be used to feed stochastic numerical simulations aiming at preliminary assessment of probability distribution of the expected seismic response in wide areas where an experimental geophysical/geotechnical characterization of the local subsoil is scarce or unavailable.

Detached structural model of the Keweenaw fault system, Lake Superior region, North America: Implications for its origin and relationship to the Midcontinent Rift System

Abstract The Keweenaw fault system along Lake Superior’s south shore in Michigan, USA is one of the most significant fault systems associated with North America’s Midcontinent Rift System. Reverse slip has thrust Portage Lake Volcanics (ca. 1.1 Ga) southeastward over Jacobsville Sandstone (ca. 1.0 Ga). Growing consensus in the 1970s about a major rift beneath Lake Superior led to the idea that reverse movement on the Keweenaw fault involved inversion of a rift-bounding normal fault. To test this idea, we integrated bedrock geology maps, subsurface mining data, and geophysical data to build a wellconstrained cross-section from the Minnesota, USA-Ontario, Canada border to central Upper Michigan. The cross-section shows the Keweenaw and Hancock faults to be parts of a reverse, listric system detached deep within the layered volcanic section. Correlation of offshore seismic units with onshore stratigraphic units defines a gradual change in stratal dip from 55° NW near the faults to horizontal near the center of Lake Superior. This stratal geometry implies that onshore listric fault geometry continues offshore and that the fault system soles into a basal detachment at 12–15 km depth. Absence of second-order folds northwest of the peninsula indicates that the fault system does not ramp downward from the basal detachment through the lower crust. The observations and model preclude ideas that the Keweenaw fault was a rift-bounding normal fault inverted by post-rift crustal shortening, or that it formed by upward propagation of a deeper normal fault undergoing inversion. Instead, our results imply that the fault initiated as a detached thrust in relatively brittle upper crust and that shortening of relatively ductile lower crust occurred on other structures.

Uranium in groundwater in parts of India and world: A comprehensive review of sources, impact to the environment and human health, analytical techniques, and mitigation technologies

Uranium concentration/contamination in groundwater is currently a subject of concern all over the world due to related severe health problems to humans, as groundwater is the main drinking water source in rural and urban India and also in several parts of the world. Uranium concentration in groundwater in shallow aquifers in various states such as Punjab, Rajasthan, Karnataka Telangana, and Madhya Pradesh of India varies from 0 to 1443 ng/ml exceeding the permissible levels by WHO for drinking water (30 ng/ml), at several places. Very high concentrations ranging up to 1400 ng/ml were reported in some areas in other countries such as Canada, the USA, Mongolia, Burundi, Zambia, Nigeria, South Korea, Pakistan, Jordon, Afghanistan, China, and Myanmar. Various natural aspects which influence the uranium concentration in groundwater such as bedrock geology, water chemistry, and redox conditions, and anthropogenic sources such as mining activities (uranium, coal, and phosphate rock), nuclear activities, agricultural practices of using phosphate fertilizers, and prevalence of excessive nitrate in some areas, are described with examples. Some of the important analytical techniques for the precise and accurate determination of elemental and isotopic concentrations of uranium in water samples, such as LED fluorimetry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), high-resolution ICP-MS (HR-ICP-MS), and multi-collector ICP-MS (MC-ICP-MS), are described. A number of advancements have taken place in remediation technologies for the removal of uranium in drinking water using different physical, chemical, and biological methods including rainwater harvesting. Various mitigation strategies for the effective removal of uranium from water during treatment, such as bioremediation using biochars from different sources, nanoparticle technology, and adsorption by magnesium (Mg)-iron (Fe)-based hydrotalcite-like compounds (MF-HT), are described in detail.

Solid-phase Mn speciation in suspended particles along meltwater-influenced fjords of West Greenland

Manganese (Mn) is an essential micro-nutrient that can limit or, along with iron (Fe), co-limit phytoplankton growth in the ocean. Glacier meltwater is thought to be a key source of trace metals to high latitude coastal systems, but little is known about the nature of Mn delivered to glacially-influenced fjords and adjacent coastal waters. In this work, we combine in-situ dissolved Mn (dMn) measurements of surface waters with Mn K-edge X-ray absorption spectroscopy (XAS) data of suspended particles in four fjords of West Greenland. Data were collected from transects of up to 100 km in fjords with different underlying bedrock geology from 64 to 70°N. We found that dMn concentrations generally decreased conservatively with increasing salinity (from 80 to 120 nM at salinity < 8 to < 40 nM at salinities > 25). Dissolved Fe (dFe) trends in these fjords similarly declined with increasing distance from glacier outflows (declining from > 20 nM to < 8 nM). However, the dMn/dFe ratio increased rapidly likely due to the greater stability of dMn at intermediate salinities (i.e. 10–20) compared to rapid precipitation of dFe across the salinity gradient. The XAS data indicated a widespread presence of Mn(II)-rich suspended particles near fjord surfaces, with structures akin to Mn(II)-bearing phyllosilicates. However, a distinct increase in Mn oxidation state with depth and the predominance of birnessite-like Mn(IV) oxides was observed for suspended particles in a fjord with tertiary basalt geology. The similar dMn behaviour in fjords with different suspended particle Mn speciation (i.e., Mn(II)-bearing phyllosilicates and Mn(IV)-rich birnessite) is consistent with the decoupling of dissolved and particulate Mn and suggests that dMn concentrations on the scale of these fjords are controlled primarily by dilution of a freshwater dMn source rather than exchange between dissolved and particle phases. This work provides new insights into the Mn cycle in high latitude coastal waters, where small changes in the relative availabilities of dMn, dFe and macronutrients may affect the identity of the nutrient(s) proximally limiting primary production.

Identification of stream sediment geochemical anomalies in lithologically complex regions: case study of Cu mineralization in Hunan province, SE China

Owing to the strong control bedrock geology may exert on the chemical composition of stream sediments, the determination of stream sediment geochemical anomalies is always affected by the lithology background in areas with variable lithologies. In this study, the expectation–maximization (EM) algorithm was used to separate lithologies of different chemical compositions in a 1: 200 000 scale regional geochemical data set of stream sediments in a lithologically complex region in Hunan province, SE China. The data set included 1024 minerogenic stream sediment samples which were analysed for Cu, La, Li, Be, Cr, Ni, Sr, V, Th, Ti and Zr. A comparison between Cu anomalies determined with and without taking into account the separation of lithologies was carried out. The result shows that stream sediment geochemical anomalies in lithologically complex regions can be determined in a more reasonable way by application of the EM clustering method. Strong but false or meaningless anomalies can be eliminated, and weak but important or meaningful anomalies are more clearly revealed.

Urban geology from a GIS-based geotechnical system: a case study in a medium-sized city (Oviedo, NW Spain)

This paper describes the development of a GIS-based geotechnical system designed to face challenges on urban geology in a Spanish mid-sized city. Its multipurpose nature is based on a relational database that holds a wide variety of georeferenced ground data, mostly extracted from geotechnical reports or acquired during fieldwork. At present it includes, among other unpublished information, more than 2000 site investigations and the results from 5000 tests carried out on rock, soil and groundwater samples. This desk tool provides a better understanding of the bedrock and superficial geology through the spatial analysis of the collected subsurface data. The main achievements include the classification and mapping of man-made grounds, fluvial sediments and residual soils; the identification of unreported faults; the review and detailed study of geotechnical parameters and properties of the rocks and soils; and the hydrogeological characterization of the permeable units. It also provided the surface geological mapping of the urban area; the development of a geo-engineering map based on lithological, geotechnical and construction criteria; and the creation of a preliminary 3D layer-based ground model of the city centre, where the subsurface contains stone used for heritage buildings listed by UNESCO.

New chronological constraints on the Plio-Pleistocene uplift of the Guizhou Plateau, SE margin of the Tibetan Plateau

The Guizhou Plateau represents a geomorphic transition between the Tibetan Plateau and the Yangtze River Plain. It likely formed in response to the propagation of surface uplift in southeastern Tibet during India-Eurasia continental collision. However, the uplift history of the region is unclear largely due to a lack of datable material. The bedrock geology is dominated by carbonate rocks, which contains numerous multi-level caves in the main river valleys that are linked to the river incision history. Cosmogenic 26 Al and 10 Be burial dating of sediments in caves and river terraces from the northwestern and southern plateau reveals the fluvial chronology and provides the first direct determination of long-term river incision rates. The caves and terraces on the Liuchong River in NW Guizhou yield burial ages of between 0.41 ± 0.12 Ma and 2.85 ± 0.21 Ma, indicating an average incision rate of 57 ± 3 m/Ma. Four level caves at Libo in southern Guizhou yield burial ages of between 0.56 ± 0.16 Ma and 3.54 (+0.25/-0.22) Ma, indicating slightly slower incision rate (47 ± 5 m/Ma). These new results imply that the high elevation of the Guizhou Plateau had developed before the Late Pliocene, and that surface uplift during the Late Cenozoic was largely uniform across the region.

Caffeine and Paraxanthine as Tracers of Anthropogenic Wastewater in Coastal Lagoons in Yucatan, Mexico.

Due to karstic bedrock geology and poor wastewater management practices, anthropogenic activities are impacting water quality in Yucatan's aquatic systems. Specifically, raw wastewater inputs to the aquifer subsequently flow to coastal lagoons through groundwater fluxes. This study establishes the presence of anthropogenic wastewater by measuring caffeine and its metabolite, paraxanthine, in four of Yucatan's major coastal lagoons: Celestun, Chelem, Dzilam de Bravo, and Ria Lagartos. Concentrations of caffeine ranged from non-detected (ND) to 2390ng L-1 and paraxanthine from ND to 212ng L-1, which correspond with pollution threats from anthropogenic wastewater inputs. The potential sources are: (1) direct in situ discharges from nearby urban settlements; and (2) contribution from submerged groundwater discharges. Overall, results indicate the potential of caffeine as an environmental tracer of anthropogenic wastewater contamination for the region.

Bedrock Geologic Map of the Northern Half of the Bedford 30- X 60-Minute Quadrangle, Indiana

The Bedrock Geologic Map of the Northern Half of the Bedford 30- X 60-Minute Quadrangle is an Esri File Geodatabase that contains six feature data sets, five geodatabase tables, and two raster data sets detailing the bedrock geology of the northern half of the Bedford 30- X 60-minute quadrangle in Indiana. This data set conforms to "GeMS (Geologic Map Schema)--a standard format for the digital publication of geologic maps." For more information on GeMS please refer to the supplemental information within this metadata.

Runoff change induced by vegetation recovery and climate change over carbonate and non-carbonate areas in the karst region of South-west China

Karst plant habitats are generally harsh and vulnerable to climate and human interferences. Restoration of karst vegetation and its effect on water resources are affected not only by climate and anthropological interferences but also by different bedrock lithologies. In this study, changes to climatic factors, vegetation indices of the normalized difference vegetation index (NDVI), the leaf area index (LAI) and runoff during 1982–2015 were statistically identified over the Yangchang river basin (YRB) with two contrasting bedrock lithologies (carbonate rock and detrital rock) in southwest China. The Budyko equation and the hydrological model in LPJ (the Lund-Potsdam-Jena Dynamic Global Vegetation Model) were calibrated and improved to separate runoff change that could be attributed to climate and vegetation changes during 1982 ~ 2015. LPJ was used to predict the potential vegetation for natural recovery without human interference and its effect on the hydrological budget in YRB. Results reveal that the execution of the major ecological restoration project (the Grain for Green Project) in YRB since the early 2000 s has significantly increased NDVI and LAI even in the drier period of 2004 ~ 2015. However, the human effort of vegetation restoration only reaches about 25% of the potential capacity in the whole study area. The reforestation in YRB could decrease runoff by about 7.0 to 7.6% in the period from 2004 to 2015, and 11.2% in the future when vegetation shifts from artificial to natural vegetation recovery. Meanwhile, thick soil in the non-carbonate area can store more water to support a large proportion of forest, and raise drought resistance. However, the limited water holding capacity of weathered bedrock in the carbonate area restricts large tree growth, and thus reduces drought resistance. These results point a need for consideration of how bedrock geology influences available water limitations when designing suitable reforestation strategies in southwest China.

Identifying factors that affect mountain lake sensitivity to atmospheric nitrogen deposition across multiple scales

Increased nitrogen (N) deposition rates over the past century have affected both North American and European mountain lake ecosystems. Ecological sensitivity of mountain lakes to N deposition varies, however, because chemical and biological responses are modulated by local watershed and lake properties. We evaluated predictors of mountain lake sensitivity to atmospheric N deposition across North American and European mountain ranges and included as response variables dissolved inorganic N (DIN = NNH4+ + NNO3–) concentrations and phytoplankton biomass. Predictors of these responses were evaluated at three different spatial scales (hemispheric, regional, subregional) using regression tree, random forest, and generalized additive model (GAM) analysis. Analyses agreed that Northern Hemisphere mountain lake DIN was related to N deposition rates and smaller scale spatial variability (e.g., regional variability between North American and European lakes, and subregional variability between mountain ranges). Analyses suggested that DIN, N deposition, and subregional variability were important for Northern Hemisphere mountain lake phytoplankton biomass. Together, these findings highlight the need for finer-scale, subregional analyses (by mountain range) of lake sensitivity to N deposition. Subregional analyses revealed differences in predictor variables of lake sensitivity. In addition to N deposition rates, lake and watershed features such as land cover, bedrock geology, maximum lake depth (Zmax), and elevation were common modulators of lake DIN. Subregional phytoplankton biomass was consistently positively related with total phosphorus (TP) in Europe, while North American locations showed variable relationships with N or P. This study reveals scale-dependent watershed and lake characteristics modulate mountain lake ecological responses to atmospheric N deposition and provides important context to inform empirically based management strategies.

Groundwater Quality Determination from hand-dug wells in Ososo Town, Akoko-Edo North Local Government Area Edo State

&#x0D; &#x0D; &#x0D; Groundwater is water beneath the surface of the earth. The primary source is precipitation from rain, snow, and hail. Groundwater commonly occurs as water that fills pore spaces between mineral or rock grains in sediments and sedimentary rocks. This study is to evaluate the physiochemical characteristics and selected heavy metal levels of Water from Hand Dug Wells in Ososo in Akoko Edo Local Government Area of Edo State, Nigeria. A total of twenty (20) water samples were collected in very clean containers from twenty (20) hand dug wells in Ososo town, and taken to the laboratory immediately for physical, chemical and heavy metal analysis using standard laboratory techniques. The physical analysis results from the study show that depth to ground water is very shallow. Ph was below 7.5. Conductivity varies from 167.8-2120.00/cm. The temperatures were uniform. The ground water is odorless and tasteless. The amounts of total suspended soil (TSS) in all the samples vary from 10–20 ppm. The total dissolved solid content (TDS) concentration for all the samples varies from 132–1320.00 ppm. Total hardness is soft to moderately hard. Total alkalinity values vary between 3.0 to 18.0 ppm. The phenolphthalein value for the sample tested was zero. Chemical analysis results for the cations shows that Calcium (Ca) is one of the most abundant cations in the entire well water samples with concentration varying from 6.4 – 40.0 mg/L. Magnesium (Mg) concentration vary from 2.0 -9.5 ppm. Dissolved Sodium (Na) content values vary from 17.9- 92.5 mg/L. Chemical analysis results for the anions shows that the concentration of sulphate (SO4) ions varies from 93–125 mg/L. The bicarbonate (CO3) concentration in all samples varies from 25.7–90 mg/L. The dissolved nitrites and nitrates concentrations varies from 5.7 – 9.1. Heavy metals analysis shows the concentrations of copper (CU) in the samples range from 0.1 – 0.5 mg/l. The result of the analysis indicates high values of lead (Pb) in nine samples, but lead was not detected in wells 6 and 7. The values for other wells ranged between 0.1-0.2 mg/l. The values for the concentration of chromium (Cr)range from 0.4 -0.89 mg/l. The values of barium (Ba) range from 0.05- 0.3 mg/l. Result from the heavy mineral analysis for Cadmium (Cd) gave an approximate value of 0.2 and below detectable limit in the other wells. The values of Zinc (Zn) range from 0.8 – 11.4 mg/l. The values of Nickel (Ni) range from 0.1–0.5 mg/l.The hand-dug wells in the study area contain free Carbon IV Oxide and the alkalinity of the well water is entirely due to Bicarbonate ions. Sodium, chloride, bicarbonates, calcium, iron, potassium and magnesium are the most abundant. All the dissolved anions in the well water sample are generally below the recommended maximum limits by WHO. Samples also showed high bacteria load which primarily originated from effluent discharge from pit toilets and waste dumps and can constitute health risk on ingestion. Highly populated areas have groundwater with high concentration of dissolved ions and the converse for areas of low population. From the results of the analysis, conclusion is drawn to the fact that, the groundwater chemistry in the study area has been influenced greatly by human activities than the bedrock geology of the area. It is therefore recommended that well location should be at least, 30 m away from any source of contamination such as soak- ways, adequate treatment must be given to well water such as chlorination, boiling to destroy any bacteria and filtration to remove all unwanted/undesirable constituents that may be present, and a policy on land use planning and urban development to guard against indiscriminate setting of wells within the centre of the village should be established. This study has been able to enhance sustainable water development, since the health of inhabitants in a community depends to a large extent on the quality of groundwater supply.&#x0D; &#x0D; &#x0D;

Decoupling of particles and dissolved iron downstream of Greenlandic glacier outflows

Glaciers can be a significant and locally dominant source of iron (Fe), a biologically essential micronutrient, in high latitude coastal seas. The vast majority of this glacial Fe delivery is associated with particles, yet the speciation of the solid-phase Fe and specifically the relationships that govern exchange between particulate and dissolved Fe phases in these environments are poorly described. In this work, we performed measurements of in situ dissolved Fe (dFe) along meltwater and particle plumes in three transects around Disko Bay and Ameralik Fjord (West Greenland). Measurements of dFe were combined with Fe K-edge X-ray absorption spectroscopy analysis of ∼40 suspended sediment samples obtained from the same transects and from select depth profiles down to 300 m. We observed relatively constant dFe levels (4 to 10 nM for nearly all dFe measurements) across fjords with widely varying particulate Fe(II) contents (from 20 to 90% Fe(II)), indicating that dFe concentrations had little dependence on the oxidation state of Fe in the suspended sediment. Particulate Fe data were grouped by underlying bedrock geology, with suspended sediment consisting of 80-90% biotite-like Fe(II) in fjords with Precambrian shield geology and poorly-ordered Fe(III) particles (<20-30% Fe(II)) in one fjord with suspended sediments derived from tertiary basalts. Our characterization data indicated no significant change in the average Fe oxidation state and bonding environment of particles along the fjord transects, implying that Fe(II) in biotite-like coordination is not a readily labile Fe form on this spatial scale. Our results suggest that dFe in these glacially-modified coastal waters is buffered at a relatively constant low nM concentration due to factors other than particle Fe mineralogy and that glacier-derived Fe phases are relatively inert on this spatial scale.

Hydrogeochemical Characteristics of Uranium and Radon in Groundwater from the Goesan Area of the Ogcheon Metamorphic Belt (OMB), Korea

Uranium and radon concentrations in groundwater from the Goesan area of the Ogcheon Metamorphic Belt (OMB), central Korea, whose bedrock is known to contain the highest uranium levels in Korea, were analyzed from 200 wells. We also measured the uranium concentrations in the bedrock near the investigated wells to infer a relationship between the bedrock geology and the groundwater. The five geologic bedrock units in the Goesan area consist of Cretaceous granite (Kgr), Jurassic granite (Jgr) and three types of metasedimentary rocks (og1, og2, and og3). The percentages of the groundwater samples over 30 μg/L (maximum contaminant level, MCL of US EPA) were 2.0% of the 200 groundwater samples; 12% of Kgr and 1.8% of Jgr exceeded the MCL, respectively. Overall, 16.5% of the 200 groundwater samples exceeded 148 Bq/L (alternative maximum contaminant level, AMCL of US EPA); 60.0% of Kgr and 25.0% of Jgr exceeded the AMCL, but only 0% of og1, 7.9% of og2, and 2.6% of og3 exceeded the value, respectively. No direct correlation was found between uranium concentration and radon concentration in water samples. Radon has a slightly linear correlation with Na (0.31), Mg (−0.30), and F (0.36). However, uranium behavior in groundwater was independent of other components. Based on thermodynamic calculation, uranium chemical speciation was dominated by carbonate complexes, namely the Ca2UO2(CO3)3(aq) and CaUO2(CO3)32− species. Although uraniferous mineral phases designated as saturation indices were greatly undersaturated, uranium hydroxides such as schoepite, UO2(OH)2 and U(OH)3 became possible phases. Uranium-containing bedrock in OMB did not significantly affect radioactive levels in the groundwater, possibly due to adsorption effects related to organic matter and geochemical reduction. Nevertheless, oxidation prevention of uranium-containing bedrock needs to be systematically managed for monitoring the possible migration of uranium into groundwater.