Bedrock Weathering Research Articles

Geochemical and Multivariate Statistical Evaluation of Trace Elements in Groundwater of Niğde Municipality, South-Central Turkey: Implications for Arsenic Contamination and Human Health Risks Assessment.

This study was conducted to determine the concentrations of trace elements, their sources, and human health risks associated with arsenic contamination in groundwater of the Niğde Municipality, south-central Turkey. Fourteen groundwater samples were collected from groundwater supply sources fed by the Niğde water distribution system and were analysed for Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, and Ba concentrations. Multivariate statistical analyses were applied to decipher the source and interrelationships among trace elements in groundwater. The groundwater is mainly tapped from Quaternary alluvial and volcanic aquifers of the Niğde Massif. The pH of groundwater is slightly acidic to neutral, which controls the solubility and mobility of the trace elements. The mean concentrations of the trace elements vary in the order Zn > Fe > Ba > As > Cr > Ni > Se > Cu > Co > Mn > Al. All of the trace element concentrations comply with the maximum permissible values provided by the Turkish Standards Institution and the World Health Organization, except Zn, Cr, and As. However, approximately 7.14% of the studied samples are contaminated with Zn and Cr, whereas 86% are contaminated with As. The As concentrations range from 9.47 to 32.9µg/L with an average value of 16.8µg/L. Contamination assessment indicates that the As contamination is dominant in the southern and southwestern parts of the area. The primary source of As in groundwater is attributed to geogenic processes involving weathering and dissolution of bed rocks and other factors, such as pH conditions, adsorption, and surface complexation. Three bimetallic complex associations are distinguished in groundwater: Fe-coordination group, As-coordination group and Ba-coordination group, all showing strong positive correlation with Cu and Ni. The As-coordination group is the most dominant in groundwater, which resulted in the high As content of groundwater. Multivariate statistical analyses indicate that As mobilization in groundwater is associated with pH, EC, Ni, Cu, and Ba depending on the redox conditions of the aquifer, controlled mainly by geogenic processes. The carcinogenic risk of arsenic affecting children and adults reaches 2 × 10-4 and 3 × 10-4, respectively, exceeding the guideline value of 1 × 10-4. The estimated hazard quotient for children is in the range of 1.79-6.21, whereas that of adults is 0.77-2.66, indicating that children in the municipality are more exposed to the noncarcinogenic effects of the consumption of high groundwater arsenic.

Seasonal hydrochemical dynamics of surface water in the Limbang River, Northern Borneo—evaluating for spatial and temporal trends

Limbang River Basin (LRB), an equatorial tropical river basin which witnesses the effect of climate change and terrain modification, is hydro-statistically characterized in the present research. In order to characterize the seasonal dynamics of hydrochemical characteristics of surface water, a total of 72 surface water samples were collected from 24 locations in the Limbang River and its tributaries for three different sampling periods (November 2016 (S1), March 2017 (S2), and September 2017 (S3)). Physical parameters (pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), turbidity), nutrients (sulfate, nitrate, ammonia, phosphate), major ions (Ca, Mg, Na, K, Cl, HCO3), and trace metals (Co, Ni, Cd, Fe, Mn, Pb, Zn, Cu) were analyzed using standard procedures and the results were statistically processed through Pearson correlation and factor analysis. Gibbs diagram, Piper plot, partial pressure of carbon dioxide, and saturation index of carbonate minerals were also employed to determine the geochemical characteristics and dominant processes operating in the river basin. Higher mean EC value of 129.28 μS/cm in S3 and higher mean pH (6.77) in S1 were observed. The results show spatial and temporal variations in analyzed parameters but are within tolerable limits of the Malaysian water quality and WHO standards. A decreasing order of HCO3- > Cl- > Na+ > Mg2+ > Ca2+ > K+ was noted in the mean concentration of major ions, whereas the mean concentration of trace metals follows the order of Fe > Ni > Pb > Mn > Zn > Co > Cu > Cd. Higher mean concentration of HCO3 (47.09 mg/L) in S2 and higher mean concentration of Fe (1.77 mg/L) in S1 were observed. The Pearson correlation test (r ≥ ± 0.70) shows varying relationships among the parameters and is different in three sampling periods. Piper diagram revealed two distinct chemical facies such as mixed Ca2+-Mg2+-Cl- and Ca2+-Mg2+-HCO3- irrespective of seasons. At the same time, Gibbs plots indicated dominant control of precipitation (rainfall) with an influence of mineral dissolution over the surface water chemistry. An increasing trend of log pCO2 values from upstream to downstream shows the direct recharge of rainwater with lower log pCO2 values in the upstream side and mixed water with higher log pCO2 in the downstream side. The saturation index indicates the under-saturated state of the carbonate minerals in the order of SIMagnesite > SICalcite > SIAragonite > SIDolomite and suggesting the effect of dilution through monsoon rainfall. Factor analysis revealed the dominance of high sediment load in response to severe rainfall, weathering, leaching and dissolution of bed rocks, hydrolysis of organic nitrogen through decomposition of microorganisms, and the aerobic decomposition of organic nitrogenous matter and atmospheric fallout as the major contributors of surface water geochemistry.

Seismic evidence of glacial deposits inhibiting weathering of local bedrock at a snow-dominated subalpine watershed

Previously glaciated landscapes are often covered with glacial sediments with poorly sorted particles. The thickness of glacial sediments can reach hundreds of meters. These sediments, which have experienced high intensity erosion through glacial transportation, are susceptible to chemical weathering processes because of the increased reactive mineral surfaces induced via erosion. Infiltrated meteoric water will first attack the glacial sediments, becoming (partially) saturated with weathering products, before interacting with the local bedrock underneath. As a consequence, the glacial deposits will hinder the weathering processes of the underlying local bedrock. In this study, we test this hypothesis by imaging the weathered layer of a previously glaciated terrain in the Medicine Bow Mountains, Wyoming using full-3D seismic ambient-noise tomography. To the best of our knowledge, our study provides the first full-3D seismic velocity model of the Critical Zone structure under a previously glaciated landscape. Our 3D seismic velocity model reveals that the saprolite weathered from local bedrock is thinner where the overlying glacial deposit layer is thicker. This anti-correlation suggests that the glacial deposits may locally protect the underlying bedrock from chemical weathering by depleting reactive chemicals in the meteoric water and (partially) saturate the meteoric water with weathering products. Our study may provide a potential counter mechanism against glaciation-induced acceleration of chemical weathering of the continents, which regulates atmospheric concentration of carbon dioxide and the global climate.

Structural controls on the hydrogeological functioning of a floodplain

Floodplains are often conceptualized as homogeneous sediment bodies which connect streams with their respective catchment and buffer agricultural inputs. This has led to a general bias within the hydrological community towards research on sites where the floodplain is a clear conduit for groundwater flow. In humid temperate regions of central Europe, floodplains have experienced rapid environmental changes since the last glaciation, yielding significant bedrock weathering and predominantly fine-grained, highly stratified hillslope and floodplain sediments. Such heterogeneous sedimentary architecture leads to conceptual ambiguities in the interpretation of the hydrogeological functioning of floodplains, thus raising the question: Do floodplains act as barriers or conduits to groundwater flow? This study analyzes the Ammer floodplain close to Tübingen in south-western Germany as a representative mid-section floodplain in a temperate climate where the regional bedrock-geology is dominated by mudstones. Geological, geophysical, and geochemical characterization and monitoring techniques were combined to shed light on the internal geological structure as a key control modulating the floodplain hydrology. Two partially separate groundwater systems were identified: a gravel body at the bottom of the Quaternary sediments and a Holocene confined tufaceous aquifer, separated by low-permeability clays. Despite flow being predominantly along-valley, sulfate concentrations in the floodplain aquifers showed evidence of a strong connection to the gypsum-bearing hillslope, particularly where tributary valley sediments are present (e.g., alluvial fans). Results from a floodplain water balance suggest the hillslope- and floodplain-aquifer material act as a barrier to hillslope groundwater recharge, where a large fraction may be bypassing the local floodplain groundwater system.

Tracking denudation and sediment production and transport with cosmogenic 10Be in arid, high‐altitude Himalayan half‐grabens, Zanskar, northern India

AbstractUnderstanding the extent to which local factors, including bedrock and structure, govern catchment denudation in mountainous environments as opposed to broader climate or tectonic patterns provides insight into how landscapes evolve as sediment is generated and transported through them, and whether they have approached steady‐state equilibrium. We measured beryllium‐10 (10Be) concentrations in 21 sediment samples from glaciated footwall and hanging wall catchments, including a set of nested catchments, and 12 bedrock samples in the Puga and Tso Morari half‐grabens located in the high‐elevation, arid Zanskar region of northern India. In the Puga half‐graben where catchments are underlain by quartzo‐feldspathic gneissic bedrock, bedrock along catchment divides is eroding very slowly, about 5 m/Ma, due to extreme aridity and 10Be concentrations in catchment sediments are the highest (~60–90 × 105 atoms/g SiO2) as colluvium accumulates on hillslopes, decoupled from their ephemeral streams. At Puga, 10Be concentrations and the average erosion rates of a set of six nested catchments demonstrate that catchment denudation is transport‐limited as sediment stagnates on lower slopes before reaching the catchment outlet. In the Tso Morari half‐graben, gneissic bedrock is also eroding very slowly but 10Be concentrations in sediments in catchments underlain by low grade meta‐sedimentary rocks, are significantly lower (~10–35 × 105 atoms/g SiO2). In these arid, high‐elevation environments, 10Be concentrations in catchment sediments have more to do with bedrock weathering and transport times than steady‐state denudation rates. © 2020 John Wiley & Sons, Ltd.

Comparison of Uranium Isotopes and Classical Geochemical Tracers in Karst Aquifer of Ljubljanica River catchment (Slovenia)

The karst aquifer of the Ljubljanica River catchment, which has numerous springs and sinks, presents an interesting environment for studying hydrogeological processes. This study aims to explore the behavior of U isotopes and to evaluate their use as tracers of hydrogeochemical processes as an alternative to classical geochemical tracers (i.e., physicochemical parameters, elemental ratios, and alkalinity) involved in water–rock interactions and water flow in this karst water system. Basic hydrochemical parameters, as well as the spatiotemporal variations of total U concentrations, 234U/238U activity ratios, and δ238U values, were monitored in water samples from springs and sinks under different hydrological conditions. The bedrock as the source of dissolved and detrital U was also analyzed. Multi-collector inductively couple plasma-mass spectrometry results reveal variations of the 234U/238U activity ratios, which are consistently negatively correlated with the discharge at most analyzed sites. Large 238U/235U isotope fractionation occurred during bedrock weathering, and the large variability of the measured δ238U values is seemingly unrelated to the lithological characteristics of the bedrock or discharge. Our results confirm that 234U/238U activity ratios in water can be used as a tracer for studying changes in groundwater flows and the mixing of waters of different origins under different hydrological conditions.

The impact of earthquakes on orogen-scale exhumation

Abstract. Individual, large thrusting earthquakes can cause hundreds to thousands of years of exhumation in a geologically instantaneous moment through landslide generation. The bedrock landslides generated are important weathering agents through the conversion of bedrock into mobile regolith. Despite this, orogen-scale records of surface uplift and exhumation, whether sedimentary or geochemical, contain little to no evidence of individual large earthquakes. We examine how earthquakes and landslides influence exhumation and surface uplift rates with a zero-dimensional numerical model, supported by observations from the 2008 Mw 7.9 Wenchuan earthquake. We also simulate the concentration of cosmogenic radionuclides within the model domain, so we can examine the timescales over which earthquake-driven changes in exhumation can be measured. Our model uses empirically constrained relationships between seismic energy release, weathering, and landsliding volumes to show that large earthquakes generate the most surface uplift, despite causing lowering of the bedrock surface. Our model suggests that when earthquakes are the dominant rock uplift process in an orogen, rapid surface uplift can occur when regolith, which limits bedrock weathering, is preserved on the mountain range. After a large earthquake, there is a lowering in concentrations of 10Be in regolith leaving the orogen, but the concentrations return to the long-term average within 103 years. The timescale of the seismically induced cosmogenic nuclide concentration signal is shorter than the averaging time of most thermochronometers (>103 years). However, our model suggests that the short-term stochastic feedbacks between weathering and exhumation produce measurable increases in cosmogenically measured exhumation rates which can be linked to earthquakes.

Influence of canopy and topographic position on soil moisture response to rainfall in a hilly catchment of Three Gorges Reservoir Area, China

Rainfall provides essential water resource for vegetation growth and acts as driving force for hydrologic process, bedrock weathering and nutrient cycle in the steep hilly catchment. But the effects of rainfall features, vegetation types, topography, and also their interactions on soil water movement and soil moisture dynamics are inadequately quantified. During the coupled wet and dry periods of the year 2018 to 2019, time-series soil moisture was monitored with 5-min interval resolution in a hilly catchment of the Three Gorges Reservoir Area in China. Three hillslopes covered with evergreen forest (EG), secondary deciduous forest mixed with shrubs (SDFS) and deforested pasture (DP) were selected, and two monitoring sites with five detected depths were established at upslope and downslope position, respectively. Several parameters expressing soil moisture response to rainfall event were evaluated, including wetting depth, cumulative rainfall amount and lag time before initial response, maximum increase of soil water storage, and transform ratio of rainwater to soil water. The results indicated that rainfall amount is the dominant rainfall variable controlling soil moisture response to rainfall event. No soil moisture response occurred when rainfall amounts was 30 mm. In the wet period, the cumulative rainfall amount to trigger surface soil moisture response in EG-up site was significantly higher than in other five sites. However, no significant difference in cumulative rainfall amount to trigger soil moisture response was observed among all study sites in dry period. Vegetation canopy interception reduced the transform ratio of rainwater to soil water, with a higher reduction in vegetation growth period than in other period. Also, interception of vegetation canopy resulted in a larger accumulated rainfall amount and a longer lag time for initiating soil moisture response to rainfall. Generally, average cumulative rainfall amount for initiating soil moisture response during dry period of all sites (3.5–5.6 mm) were less than during wet period (5.7–19.7 mm). Forests captured more infiltration water compared with deforested pasture, showing the larger increments of both soil water storage for the whole soil profile and volumetric soil water content at 10 cm depth on two forest slopes. Topography dominated soil subsurface flow, proven by the evidences that less rainfall amount and less time was needed to trigger soil moisture response and also larger accumulated soil water storage increment in downslope site than in corresponding upslope site during heavy rainfall events.

Soil, regolith, and weathered rock: Theoretical concepts and evolution in old-growth temperate forests, Central Europe

Evolution of weathering profiles (WP) is critical for landscape evolution, soil formation, biogeochemical cycles, and critical zone hydrology and ecology. Weathering profiles often include soil or solum (O, A, E, and B horizons), non-soil regolith (including soil C horizons, saprolite), and weathered rock. Development of these is a function of weathering at the bedrock weathering front to produce weathered rock; weathering at the boundary between regolith and weathered rock to produce saprolite, and pedogenesis to convert non-soil regolith to soil. Relative thicknesses of soil (Ts), non-soil regolith (Tr) and weathered rock (Tw) can provide insight into the relative rates of these processes at some sites with negligible surface removals or deposition. Scenarios of weathering profile development based on these are developed in current study. We investigated these with ground penetrating radar, electrical resistance tomography, and seismic profiling at three old growth forest sites in the Czech Republic, on gneiss, granite, and flysch bedrock.We found that the geophysical methods – which generated thousands of separate measurements of Ts, Tr, Tw – to produce good estimates. The weathered rock layer (sensu lato) was generally the thickest of the weathering profile layers. Mean soil thicknesses were about 0.64–0.75 m at the three sites, with typical maxima around 1.5 m. Non-soil regolith thicknesses averaged about 2.5 m on the gneiss site and 1.2–1.4 at the other sites. Weathered rock had a mean thickness of 7 m at the gneiss site (up to 10.3), 4.6 at the granite site, and 3.4 on flysch. Results indicate that weathering at the bedrock weathering front is more rapid than conversion of weathered rock to regolith, which is in turn more rapid than saprolite-to-soil conversion by pedogenesis on all three bedrock types. No evidence was found of steady-state soil, non-soil regolith, or weathered rock thicknesses or evolution toward steady-state. Steady-state would require that weathering rates at the bedrock and/or regolith weathering fronts decline to negligible rates as profiles thicken, but the relative thicknesses at our study sites do not indicate this is the case.

Multivariate assessment of groundwater quality in the basement rocks of Osun State, Southwest, Nigeria

Groundwater is a major source of drinking water in many rural and urban areas of developing nations. Pollution of groundwater from diverse sources is an issue of concern due to inherent health problems. This study assessed the possible contamination source to groundwater quality in the basement rocks of Osun State, South-Western Nigeria using multivariate analyses of Principal Component Analysis (PCA) and Cluster Analysis (CA). The secondary data from 536 wells across the 30 Local Government Areas in the State were collected from the Rural Water and Environmental Sanitation Agency (RUWESA). The groundwater data include pH, temperature, turbidity, oxido-reduction potential, total dissolved solids, electrical conductivity, total alkalinity, magnesium hardness, calcium hardness, total hardness, free chlorine, total chlorine, chloride, fluoride, nitrate, nitrite, iron, manganese and zinc. The data were subjected to simple and inferential statistics using the Statistical Package for Social Sciences (SPSS vs. 21.0). The mean results of groundwater parameters such as nitrate and Mn were higher than the World Health Organisation (WHO) limits of 0.4 and 10 mg/L, respectively. The results of the PCA and CA revealed possible sources of pollutants to the groundwater quality as weathering of bedrocks, leachate from septic tanks and dumpsites, runoff of materials, hardness, nutrients from agricultural lands, and chlorine pollution.

Evaluation of zircon U-Pb geochronology as a tool to determine soil provenance in a limestone terrane, Middle TN, USA

Soil can form by bedrock weathering or by deposition of alluvial or aeolian material. To test the utility of detrital zircon UPb geochronology for determining soil provenance, and to determine the provenance of soils in Middle Tennessee, samples of soil and underlying bedrock were collected from two sites, along with alluvium from a nearby river and loess from West Tennessee. Multi-dimensional scaling plots were used to compare complex detrital zircon LA-ICP-MS UPb sample age distributions. Concentration ratios of immobile elements and Nd and Hf isotope compositions were also used as provenance indicators for comparison. At one site zircon UPb ages and bulk sample trace element and isotopic compositions of soil were similar to the underlying limestone bedrock, indicating soil formation by bedrock weathering. In contrast, at a second site provenance tests indicate that soil from a late Pleistocene river terrace was sourced from alluvium rather than the underlying bedrock. Provenance inferences based on zircon UPb ages were generally consistent with evidence from Zr/Hf ratios and Hf isotope compositions, which are all dominated by zircon, and Nd isotope compositions, which are not, although the best matches for different provenance indicators did not always agree. Zircon geochronology should be used with other soil provenance indicators to reduce effects of bias introduced by sedimentary sorting and sample processing.

Investigating the Depth and the Geometry of the Quarzitic Panafrican Basement Using Near-Surface 3D Seismic Refraction Tomography: Case Study of the Locality of Bakel (Senegal)

Seismic refraction investigations have been carried out in Bakel, Eastern Senegal. The purpose was to map geometrical relationship between the existing rock types and the Panafrican quarzitic basement, which is valuable information for the project of the Bakel fluviatile port construction. Four seismic refraction profiles were acquired. The obtained data have been processed by inversion. The obtained four seismic P-wave velocity profiles have been integrated to obtain a 3D model. By comparing the outcropping geological formations with the observed seismic data at the surface, it was possible to identify the lithology corresponding to each measured range of seismic velocity for the alluvium, the weathered bed rock, and the fresh rock. The results showed that the depth of the fresh rock of the basement varies from 0 to 18 meters above the sea level, with a deepening toward the Senegal River and toward the Northern part of the studied area. The presence of alluviums and their thickness are linked to the existence of bays and gulfs. The results of this study give valuable information for the river bed dredging cost assessment prior to the port construction phase.

Soil production and the soil geomorphology legacy of Grove Karl Gilbert

AbstractGeomorphologists are quantifying the rates of an important component of bedrock's weathering in research that needs wide discussion among soil scientists. By using cosmogenic nuclides, geomorphologists estimate landscapes’ physical lowering, which, in a steady landscape, equates to upward transfers of weathered rock into slowly moving hillslope‐soil creep. Since the 1990s, these processes have been called “soil production” or “mobile regolith production”. In this paper, we assert the importance of a fully integrated pedological and geomorphological approach not only to soil creep but to soil, regolith, and landscape evolution; we clarify terms to facilitate soil geomorphology collaboration; and we seek a greater understanding of our sciences’ history. We show how the legacy of Grove Karl Gilbert extend across soil geomorphology. We interpret three contrasting soils and regoliths in the USA's Southern Piedmont in the context of a Gilbert‐inspired model of weathering and transport, a model of regolith evolution and of nonsteady systems that liberate particles and solutes from bedrock and transport them across the landscape. This exercise leads us to conclude that the Southern Piedmont is a region with soils and regoliths derived directly from weathering bedrock below (a regional paradigm for more than a century) but that the Piedmont also has significant areas in which regoliths are at least partly formed from paleo‐colluvia that may be massive in volume and overlie organic‐enriched layers, peat, and paleo‐saprolite. An explicitly integrated study of soil geomorphology can accelerate our understanding of soil, regoliths, and landscape evolution in all physiographic regions.

Microbial chemolithotrophy mediates oxidative weathering of granitic bedrock

The flux of solutes from the chemical weathering of the continental crust supplies a steady supply of essential nutrients necessary for the maintenance of Earth's biosphere. Promotion of weathering by microorganisms is a well-documented phenomenon and is most often attributed to heterotrophic microbial metabolism for the purposes of nutrient acquisition. Here, we demonstrate the role of chemolithotrophic ferrous iron [Fe(II)]-oxidizing bacteria in biogeochemical weathering of subsurface Fe(II)-silicate minerals at the Luquillo Critical Zone Observatory in Puerto Rico. Under chemolithotrophic growth conditions, mineral-derived Fe(II) in the Rio Blanco Quartz Diorite served as the primary energy source for microbial growth. An enrichment in homologs to gene clusters involved in extracellular electron transfer was associated with dramatically accelerated rates of mineral oxidation and adenosine triphosphate generation relative to sterile diorite suspensions. Transmission electron microscopy and energy-dispersive spectroscopy revealed the accumulation of nanoparticulate Fe-oxyhydroxides on mineral surfaces only under biotic conditions. Microbially oxidized quartz diorite showed greater susceptibility to proton-promoted dissolution, which has important implications for weathering reactions in situ. Collectively, our results suggest that chemolithotrophic Fe(II)-oxidizing bacteria are likely contributors in the transformation of rock to regolith.

Influence of late-Holocene climate change on the solid-phase speciation and long-term stability of arsenic in sub-Arctic lake sediments

Sediment cores were collected from two lakes in the Courageous Lake Greenstone Belt (CLGB), central Northwest Territories, Canada, to examine the influence of late-Holocene warming on the transport and fate of arsenic (As) in sub-Arctic lakes. In both lakes, allochthonous As-bearing minerals (i.e. arsenopyrite and scorodite) were identified in sediment deposited during times of both regional warming and cooling, suggesting that weathering of bedrock and derived surficial materials provides a continual source of As to lakes of the CLGB. However, maximum porewater As (84 μg·L−1 and 15 μg·L−1) and reactive organic matter (OM; aquatic and terrestrial-derived) concentrations in each lake are coincident with known periods of regional climate warming. It is inferred that increased biological production in surface waters and influx of terrigenous OM led to the release of sedimentary As to porewater through reductive dissolution of As-bearing Fe-(oxy)hydroxides and scorodite during episodes of regional warming. Elevated sedimentary As concentrations (median: 36 mg·kg−1; range: 29 to 49 mg·kg−1) are observed in sediment coeval with the Holocene Thermal Maximum (ca. 5430 ± 110 to 4070 ± 130 cal. years BP); at these depths, authigenic As-bearing framboidal pyrite is the primary host of As in sediment and the influence of organic matter on the precipitation of As-bearing framboidal pyrite is apparent petrographically. These findings suggest that increased biological productivity and weathering of terrestrial OM associated with climate warming influences redox cycles in the near-surface sediment and enhances the mobility of As in northern lakes. Knowledge generated from this study is relevant for predicting future climate change-driven variations in metal(loid) cycling in aquatic systems and can be used to interpret trends in long-term environmental monitoring data at historical, modern, and future metal mines in northern environments.

Elements in surface and well water from the central North China Plain: Enrichment patterns, origins, and health risk assessment

The principal aim of this study was to understand the enrichment patterns of elements in water from typical coal mine and irrigation areas. For this study, samples of surface water, shallow water, and deep water were collected from Handan, Jining, and Heze cities and their surrounding areas in the central North China Plain. The results showed that the hydrochemical characteristics were dominated by Ca–Mg–Cl and Ca–HCO3. Elements in the studied surface water, including strontium, iron and boron, were anomalously enriched at levels more than 654, 294 and 134 times their global river water averages, respectively. The concentrations of elements in the studied area were influenced by both natural processes and anthropogenic sources, but the dominant origins of the anomalous enriched elements were bedrock weathering and soil leaching. The deep well water quality in the Handan coal mining area was good, while the poor-quality water samples in the study area were mainly distributed in the alluvial plain, which is characterized by Neogene-Quaternary sediments and aquifers. The measured hazard quotient and hazard index values indicate that the arsenic and nickel in the studied samples could pose a noncarcinogenic risk to the health of local residents, especially children. The leading source of the high arsenic levels is influenced by natural process. Monitoring plans for arsenic, iron, manganese, nitrate and other potentially harmful elements in surface water and groundwater and effective health education on pollution by these elements are essential.

26Al/10Be ratios reveal the source of river sediments in the Kimberley, NW Australia

AbstractWe use cosmogenic 10Be and 26Al in both bedrock and fluvial sediments to investigate controls on erosion rates and sediment supply to river basins at the regional scale in the Kimberley, NW Australia. The area is characterised by lithologically controlled morphologies such as cuestas, isolated mesas and extensive plateaus made of slightly dipping, extensively jointed sandstones. All sampled bedrock surfaces at plateau tops, ridgelines, and in the broader floodplain of major rivers over the region show similar slow lowering rates between 0.17 and 4.88 m.Myr‐1, with a mean value of 1.0 ± 0.6 m.Myr‐1 (n=15), whilst two bedrock samples collected directly within river‐beds record rates that are one to two orders of magnitude higher (14.4 ± 1.5 and 20.9 ± 2.5 m.Myr‐1, respectively). Bedrock 26Al/10Be ratios are all compatible with simple, continuous sub‐aerial exposure histories. Modern river sediment yield lower 10Be and 26Al concentrations, apparent 10Be basin‐wide denudation rates ranging between 1.8 and 7.7 m.Myr‐1, with a median value of 2.6 m.Myr‐1, more than double the magnitude of bedrock erosion rates. 26Al/10Be ratios of the sediment samples are lower than those obtained for bedrock samples. We propose that these depleted 26Al/10Be ratios can largely be explained by the supply of sediment to river basins from the slab fragmentation and chemical weathering of channel gorge walls and plateau escarpments that result in diluting the cosmogenic nuclide concentration in river sediments measured at the basin outlets. The results of a mass‐balance model suggest that ~60–90% of river sediment in the Kimberley results from the breakdown and chemical weathering of retreating vertical sandstone rock‐walls in contrast to sediment generated by bedrock weathering and erosion on the plateau tops. This study emphasises the value of analysing two or more isotopes in basin‐scale studies using cosmogenic nuclides, especially in slowly eroding post‐orogenic settings. © 2019 John Wiley & Sons, Ltd.

Features of modeling gabion retaining walls for engineering protection of roads on landslide slopes

During the construction of roads in mountainous areas, engineering protection of the highway from landslide processes is often required. Currently, there are many designs used to protect against landslides. However, the engineers are faced with the task of choosing the optimal structural solution both in terms of the boundaries of the field of application of the structures and in terms of economic efficiency. In addition, the problem arises of correct modeling of the predicted situation. The article discusses the engineering protection of the road under construction in Sochi, Krasnodar Territory. In the study of the territory on the site, three landslides were found that are in extreme condition, erosion processes, an elevated level of groundwater, planar flushing, and also weathering of bedrock when they are opened during the laying of the route. Two schemes of constructive solutions using gabion construction both on a natural basis and on a pile are considered. The choice of the type of protective structure is determined by the presence of both surface and ground waters, as well as by a technical and economic comparison (in comparison with a reinforced concrete retaining wall). The authors reviewed existing software systems used in the calculation of underground structures, and also analyzed the basic methods for calculating the slope stability and structural strength. As a result of the study, such geotechnical software systems as: Plaxis, GeoStudio, Geo5 were selected to simulate a landslide slope. Slope stability was determined both for the main combination of loads and for the special one (seismic of 8 points) using such methods as: Phi/c reduction, Morgenstern-Price method and Shahunyants method. The results obtained showed good convergence.

Evidence for accelerated weathering and sulfate export in high alpine environments

High elevation alpine ecosystems—the ‘water towers of the world’—provide water for human populations around the globe. Active geomorphic features such as glaciers and permafrost leave alpine ecosystems susceptible to changes in climate which could also lead to changing biogeochemistry and water quality. Here, we synthesize recent changes in high-elevation stream chemistry from multiple sites that demonstrate a consistent and widespread pattern of increasing sulfate and base cation concentrations or fluxes. This trend has occurred over the past 30 years and is consistent across multiple sites in the Rocky Mountains of the United States, western Canada, the European Alps, the Icelandic Shield, and the Himalayas in Asia. To better understand these recent changes and to examine the potential causes of increased sulfur and base cation concentrations in surface waters, we present a synthesis of global records as well as a high resolution 33 year record of atmospheric deposition and river export data from a long-term ecological research site in Colorado, USA. We evaluate which factors may be driving global shifts in stream chemistry including atmospheric deposition trends and broad climatic patterns. Our analysis suggests that recent changes in climate may be stimulating changes to hydrology and/or geomorphic processes, which in turn lead to accelerated weathering of bedrock. This cascade of effects has broad implications for the chemistry and quality of important surface water resources.

Hydrogeochemistry of the deglaciated lacustrine systems in Antarctica: Potential impact of marine aerosols and rock-water interactions

The deglaciated lacustrine systems in Grovnes, Larsemann Hills, East Antarctica was assessed for its solute dynamics and hydrogeochemical interactions. These pristine high latitude lacustrine systems serve as a natural laboratory to understand the interaction between hydrosphere, lithosphere and atmosphere thus providing valuable insights on the functioning of major biogeochemical cycles. A total of 14 fresh water lakes were identified and the water samples were analysed for its physico-chemical characteristics. The abundance of anions and cations in the lake water samples were in the following order of Cl− > HCO3– > SO42− > NO3− and Na+ > Mg2+ > Ca2+ > K+ respectively. Moreover, the lakes exhibit slightly alkaline condition due to dissolution of alkaline earth metals and atmospheric fallout. Na+-Cl−–HCO3– and Na+-Cl− are the commonly noticed water type in the study area and higher concentration of Na+-Cl− were due to the effect of sea spray through marine aerosols. Reverse ion exchange is noticed in most of the lakes due to saline influence. Three major mechanisms such as rock dominance, precipitation/snow and evaporation/sea spray controls the lake water geochemistry in the study area. Silicate weathering and evaporite dissolution also contribute ionic load to the lake water. Significant positive correlations (p < .01) among major ions reveal sources from bedrock weathering along with marine aerosols. Trace element chemistry shows that rock-water interaction is the primary source for dissolved metals in the lake water followed by long range atmospheric transport in the form of aeolian dust. Mineral groups such as evaporites, sulphates, carbonates, metal oxides and hydroxides are responsible for the dissolution of metal complexes in the lake water. Furthermore, lakes falling within a micro basin have shown higher Na+-Cl− content which is due to the catchment effect where snow enriched with sea spray melts during the austral summer feeding these lakes.