Natural Concentration Levels Research Articles

Evaluation of Radiation Rates and Health Hazards from Different Cement Types in Pakistan

The raw materials of cement contain radioactive elements that come from natural sources. Members of the decay chains of uranium, thorium, and potassium radioisotope 40K are the primary sources of this radioactivity. The natural radionuclide concentration levels in cement differ greatly depending on different geographic areas. To estimate the radionuclides concentration in cement specimens from twelve diverse Pakistani companies, gamma-ray spectroscopy analysis was used in the study. 226Ra, 232Th, and 40K had activity concentration levels ranging from 18.08 to 43.18 Bq/kg, 16.73 to 23.53 Bq/kg, and 14.24 to 315.22 Bq/kg, respectively. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) threshold for the 226Ra was surpassed by five of the studied samples. The indoor and outdoor dose rates as well as different radiological health hazard indices were also examined. The Indoor Absorbed Dosage (Din) for some of the samples exceeded the permissible limit. These samples also had a high Indoor Effective Lifetime Cancer Risk (ELCR) factor, which makes them unsafe for interior construction purposes. The outdoor dosages as well as the hazard indices were well within the permitted ranges. The outdoor ELCR factor is low for all the cement brands, which makes them safe for exterior construction purposes. The findings were compared with published data from other countries around the globe. Finally, a thorough statistical analysis was performed and Pearson’s Correlation Coefficient (r) exhibited a very strong correlation between the different outdoor and indoor radiological health hazard indices.

Determination of Radionuclides Concentrations in Surface Soil Samples in the District of Bandirma, Balıkesir

Determination of the environmental radioactivity concentration value is very important as it directly effects human health. Natural and artificial radionuclide concentration levels have been determined by looking 226Ra, 232Th, 40K, and 137Cs radionuclides. In this study, natural and artificial continental radionuclide concentrations were measured in the Bandirma district of Balikesir. 226Ra, 232Th, 40K, and 137Cs radioactivity concentrations were detected with the aid of a high-purity germanium (HpGe) detector. Soil samples used in the study were selected from 30 different locations sampling points located in Bandirma. The radiological hazard indices such as absorbed gamma dose rate (D), annual gonadal dose equivalent (AGDE), exposure dose (ER), total annual effective dose (AED), excess lifetime cancer risk (ELCR), internal hazard index (Hin), external hazard index (Hex) and gamma representative level (GRL) were determined. The mean values of 226Ra, 232Th, 40K, and 137Cs concentrations in this study were 15.81 ± 1.35 Bq kg−1, 28.86 ± 1.07 Bq kg−1, 276.86 ± 11.69 Bq kg−1, and 1.98 ± 0.31 Bq kg−1 respectively. The calculated radiological hazard parameters were compared with the world averages. The obtained radioactivity concentration values were measured to be below the world average.

Radiological hazard levels of construction rocks excavated from quarries in Kericho county, Kenya

The study determined the natural activity concentration levels of 40K, 232Th and 238U in rocks used for construction from the 15 selected quarries in Kericho County, Kenya through Gamma-ray Spectrometric analysis at the Physical Sciences department of South Eastern Kenya University (SEKU). IAEA procedures were followed from sample collection, preparation and measurement. Samples were collected, crushed, oven dried at 105 , weighed and packed in sealed containers and kept for four weeks in order for secular equilibrium to be achieved between 226Ra and 232Th. The average activity concentration of 232Th, 238U and 40K were 101 ± 5 Bq/kg, 56 ± 3 Bq/kg and 1100 ± 55 Bq/kg and ranged from 41 ± 2 to 138 ± 7 Bq/kg, 26 ± 1 to 116 ± 6 Bq/kg and 512 ± 26 to 1919 Bq/kg ± 96 Bq/kg respectively. The average external and internal hazard indices were 0.8 mSv/y and 0.9 mSv/y respectively. Radium equivalent ranged from 222 ± 11 Bq/kg to 366 ± 18 Bq/kg with an average value of 285 ± 14 Bq/kg which was below the permissible limit of 370 Bq/kg; therefore, the excavated rocks for construction from the selected quarries in Kericho county poses insignificant health risk to the general population and quarry workers.

Semiochemical signatures associated with differential attraction of Anopheles gambiae to human feet.

BackgroundSeveral human-produced volatiles have been reported to mediate the host-seeking process under laboratory conditions, yet no effective lure or repellent has been developed for field application. Previously, we found a gradation of the attractiveness of foot odors of different malaria free individuals to Anopheles gambiae sensu stricto Giles. In this study, foot odor of the individual with the most attractive ‘smelly’ feet to the An. gambiae was collected, analyzed and attractive blend components identified.MethodsThe foot odor of the individual with the most attractive ‘smelly’ feet to the An. gambiae was trapped on Porapak Q and analyzed by gas chromatography-linked mass spectrometry (GC-MS). Specific constituents perceived by the insect olfactory system were then identified by GC-linked to electro-antennography detector (GC-EAD) and characterized by GC-MS. The contribution of each constituent to the behavioral response of An. gambiae was assessed through subtractive assays under semi-field conditions in a screen-house using Counter Flow Geometry (CFG traps) baited with (i) the blend of all the EAD-active and (ii) other blends containing all components with exclusion of one component at a time. The number of mosquitoes trapped in the baited CFG traps were compared with those in the control traps.ResultsEleven major and minor constituents: 2 carboxylic acids, six aldehydes, two ketones and one phenolic compound, were confirmed to be EAD-active. The contribution of each constituent to the behavioral response of An. gambiae was assessed through subtractive assays under semi- field conditions. Exclusion/ subtraction of one of the following compounds: i-butyric acid, i-valeric acid, n-octanal, n-nonanal, n-decanal, n-dodecanal, undecanal or n-tridecanal, from each blend led to reduction in the attractiveness of all the resulting blends, suggesting that all of them are critical/important for the attractiveness of the foot odor to An. gambiae mosquitoes. However, exclusion/subtraction of 4-ethoxyacetophenone, 4-ethylacetophenone and/or 2-methylphenol, led to significant enhancements in the attractiveness of the resulting blends, suggesting that each of these compounds had repellent effect on An. gambiae ss. Undecanal exhibited kairomonal activity at low natural concentrations under semi-field conditions but repellent activity at high unnatural conditions in the laboratory. Furthermore, the comparison of the mean mosquito catches in traps baited with the nine-component blend without 4-ethoxyacetophenone, 4-ethylacetophenone and the complete foot odor collection revealed that the former is significantly more attractive and confirmed the repellent effect of the two carbonyl compounds at low natural concentration levels.ConclusionThese results suggest that differential attractiveness of An. gambiae to human feet is due to qualitative and/or qualitative differences in the chemical compositions of the foot odors from individual human beings and relative proportions of the two chemical signatures (attractants versus repellents) as observed from the ratios of the bioactive components in the foot odors of the most attractive and least attractive individuals. Chemical signature means the ensemble of the compounds released by the organism in a specific physiological state. The chemical signature is emitter-dependent, but does not depend on receiver response. Thus, there is only one chemical signature for one individual or species that may eventually include inactive, attractive and repellent components for another organism. The nine-component attractive blend has a potential as an effective field bait for trapping of malaria vectors in human dwellings.

Modeling of zircon nucleation and growth rates using crystal size distributions in a cooling magmatic intrusion

With a rapid increase in the use of zircons for geochronology and in situ isotopic and chemical analyses it is important to quantify growth rates and nucleation rates of zircons in natural magmatic systems. Here we present a mathematical model of the nucleation and growth of a population of zircon crystals in a cooling magmatic intrusion and apply nucleation laws to derive zircon crystal size distributions (CSD) and particle number density (n per cm3 of melt) from first principles. The model is based on a numerical solution of the one-dimensional diffusion equation that accounts for the nucleation and growth of individual crystals and the dependence of the equilibrium concentration of Zr on temperature. As experimental studies of zircon nucleation at natural concentration levels of Zr are nearly impossible, we rely on measured CSDs of age-invariant (within error of the method <±5ky) zircon populations in rapidly quenched eruptive products of known crystallization duration to calibrate our model. The CSDs of zircon crystals are calculated at different rates of cooling of the magma chamber and are compared to measurements. The combination of the zircon growth software with measurements of zircon CSDs and particle number density permits direct estimation of the zircon nucleation rates and their evolution with time in cooling magmatic systems. We observe a delayed zircon nucleation of 500–2000 years after the melt becomes zircon saturated. Zr supersaturations that drive grown in simulations range from 1 to ∼30ppm and vary non-monotonically as crystallization proceeds. Initially, the nucleation rates increase exponentially from 10−3 to ∼1crystals/cm3/yr but then decrease by an order of magnitude as the distance between zircons decreases. Growth rates stay in 10−15cm/s range for the most duration of zircon growth. The ratio of growth to nucleation rates in our model also varies insignificantly and is used to estimate crystallization time based on the CSD slope, which decreases with the increased duration of cooling. Flatter slopes correspond to longer crystallization durations as is also noted for major phases. Due to non-monotonic variations in growth and nucleation rates with time, the observed deficiency of small zircons resulting in concave up CSD shapes can be reproduced from first principles assuming monotonic cooling of the magmatic system. Variations in the mode of cooling from linear to monotonic during conductive heat loss of a cooling intrusion, and minor coeval precipitation (<10vol%) of major phases has little impact on zircon CSD and its evolution. This study has implication to individual zircons IDTIMS dates and demonstrates that most zircons crystallize much later than magma becomes saturated with Zr, despite sometimes having nominally long tail crystallization rate in the inherited cores. For natural CSDs from eight different eruptions randomly selected zircons predate eruption age only by ∼300–1000years.

Spatial distribution, environmental risk assessment, and source identification of potentially toxic metals in Atikhisar dam, Turkey.

The objective of this study was to determine the ecological risk created by metal contents of the surface sediments of Atikhisar dam, Çanakkale, NW Turkey. Enrichment factor (EF) and geoaccumulation index (Igeo) were calculated to determine anthropogenic effects. Ecological risk was assessed using the modified potential ecological risk index (mPER), with its levels being evaluated using the modified ecological risk index (mER). Toxic effects were determined using the toxic risk index (TRI). The ecological risk indices were mapped to provide their spatial distributions. Our findings indicate that enrichment was very high for Hg and significant for Pb, Tl, Cd, and As. The following mER pattern was detected: Hg > Cd > TI > As > Pb > Ni > Cr > Co > Zn > Mn > V. Hg and Cd exhibited extremely high and very high ecological risks, respectively, while TI and As had a significant ecological risk, with Pb exerting a medium ecological risk. Hg, Pb, Tl, Cd, As, Cr, Ni, Zn, and Cu were enriched via anthropogenic effects exceeding their natural concentration levels. Due to their high toxic effects, Hg, Cd, Tl, As, and Pb were identified as the very high risk elements. Mining, household wastes, agriculture, and natural mineral deposits were identified as the possible sources of the potential ecological risk.

Object oriented spatial analysis of natural concentration levels of chemical species in regional-scale aquifers

We address the problem of characterizing spatially variable Natural Background Levels (NBLs) of concentrations of chemical species of environmental concern in a large-scale groundwater body. Assessment of NBLs is critical to identify significant trends of (possibly hazardous) chemical concentrations in aquifer systems, the latter being typically associated with spatially heterogeneous hydrogeochemical characteristics. Our study considers the entire probability density function (PDF) of the concentration of the chemical species of interest as atom of the statistical analysis. These PDFs are estimated across a network of observation boreholes in the investigated spatial domain, and modeled as random points in a Bayes Hilbert space, in the context of Object Oriented Data Analysis. This approach enables one to take advantage of the entire information content provided by these objects for the purpose of spatial prediction and uncertainty quantification. As a key element of innovation, we investigate the use of depth measures for distributional data with the distinctive aims of (i) detecting central and outlying NBL distributions in the dataset, and (ii) building prediction regions for NBL distribution at unsampled locations. We illustrate the results of the proposed approach to the analysis of NBLs of a selected chemical species detected at an environmental monitoring network within a large-scale alluvial aquifer in Northern Italy.

Measurement the natural radioactivity concentration levels of radionuclides in selected vegetables collected from Kirkuk, Iraq using HPGe detector

ABSTRACT The aim of this study is to determine the natural radioactivity levels and evaluate the radiological hazard in vegetable samples collected from Kirkuk city by using gamma-ray spectrometer HPGe. The results show that the highest specific activity of 226Ra and 232Th in vegetables was (9.65, 7.9) Bq.kg–1 in Vg27 (Root/Garlic) while, the highest specific activity of 40K was (221.08 Bq.kg–1 in Vg37 (Leguminous/kidney bean), respectively. The results show that the average specific activities in vegetable samples for 226Ra and 232Th, and 40K was (6.119, 4.763 and 135.595) Bq.kg–1, respectively, these results were found to be below natural radiation exposure reported by UNSCEAR, radium equivalent activity (Raeq) were varied from maximum value (30.345 Bq.kg–1 in Vg15 (Leafy/coriander leaves)) to minimum value 13.002 Bq.kg–1 in Vg37 (Leguminous/kidney bean)) with average value 23.371 Bq.kg–1, the total average annual effective dose in vegetable samples for adults, children (10 years old) and infants are estimated to be (60.487, 128.090 and 170.431 μSvy–1), respectively, than those below the WHO permissible limit of 0.3 m μSvy–1. The calculated values of external and internal hazard index in the samples which were lower than the worldwide average value 1, respectively; therefore, these values are found to be safe. The level of radioactivity concentrations in vegetables was determined to ensure consumer safety and the results provide useful information to assess the dose emitted from this radioactivity due to ingestion of these vegetables. This study is very important to investigate the level of radioactivity of vegetables and the findings of this study will useful to determine a baseline of radioactivity exposure to the human from ingestion of vegetables.

Assessment of gamma radiation levels of beach sands in Bitlis region of Lake Van

Natural gamma radioisotope activity concentration levels in beach sands in the Bitlis region of Lake Van, in eastern Turkey, were determined using an HPGe detector. A total of 15 different beach sand samples were collected from Ahlat, Adilcevaz, and Tatvan shoreline regions, and then 226Ra, 232Th, 40K, and 137Cs radioisotope activity concentrations were measured. Mean values of gamma emissions for each radioisotope were determined as 58.78, 65.89, 1590.25, and 4.84 Bq kg−1 for 226Ra, 232Th, 40K, and 137Cs, respectively. Mean radium equivalent activity, absorbed gamma dose rate, annual effective dose, and external hazard index values were calculated as 275.45 Bq kg−1, 135.41 nGy h−1, 0.17 mSv year−1, and 0.74, respectively.

Risk assessment due to various terrestrial radionuclides concentrations scenarios

Purpose: The purpose of this paper is to evaluate the morbidity excess cancer risk (ECR) due to internal and external exposure to three category levels of natural radionuclides in soil like 238U, 232Th and 40K. Although the exposure rate in soil is low but effect this radiation over time can lead to cancer risk and this risk can be calculated.Materials and methods: Natural activity concentration levels of 40K, 238U and 232Th in soil were selected from last reports in three concentration categories including: low, medium and high levels. The excess cancer risks of three concentration levels were calculated by means of RESidual-RADioactivity (RESRAD) code.Results and conclusions: The calculated average morbidity ECR from 40K, 238U and 232Th in three concentration categories levels in soil were 1.40 × 10−4, 8.56 × 10−4 and 1.35 × 10−3, respectively. This calculation shows that the excess cancer risk value is the highest value in 100 years’ time in all categories. Overall ECR from 40K radionuclide was maximal and the highest exposure pathways was through plant pathway; however, these pathway changes over 60 years to the drinking water pathway. The results of this study may be useful to risk assessment and for decision making for public health protection against high-level radiation.

Olivine compositional changes in primitive magmatic skarn environments: A reassessment of divalent cation partitioning models to quantify the effect of carbonate assimilation

The geochemical evolution of olivine from primitive magmatic skarn environments has been studied by atmospheric pressure experiments carried out at 1250, 1200, and 1150 °C under QFM oxygen buffering conditions. The starting materials were three synthetic basalts (i.e., meltMg#78, meltMg#75, and meltMg#72) doped with variable amounts of CaCO3, in order to reproduce the natural concentration levels of CaO-rich magmas interacting with the skarn rock shells. Results from decarbonation experiments evidence that the crystallization of Fo-CaO-rich, NiO-poor olivines is more favored at higher temperatures when primitive basaltic magmas assimilate increasing amounts of carbonate materials. The number of large size Ca cations entering olivine crystal lattice is proportional to the amount of Ca-O-Si bonds available in the melt. Due to differences between Fe2+ and Mg cation radii, the Ca-Fe2+ substitutions into M2 crystallographic site are more facilitated than CaMg ones, thus enhancing the forsterite component in olivine. The partitioning behavior of Ni, Mg, Fe2+, Mn, and Ca between olivine and melt has been also investigated to better understand cation redistribution mechanisms at the magma‑carbonate reaction zone. In this context, some partitioning models from the literature have been refined to more accurately quantify the geochemical evolution of primitive skarn systems. Under the effect of CaCO3 assimilation, the partitioning of divalent cations, can be parameterized as a function of temperature, bulk composition (mostly, CaO and MgO contents in both olivine and melt) and melt structure (expressed as the number of non-bridging oxygens per tetrahedrally coordinated cations). Conversely, the exchange partition coefficients between Fe2+/Ca/Mn/Ni and Mg do not vary significantly as a function of temperature and meltMg#, due to the limited influence of these parameters on the melt structure. In turn, cation exchange reactions are primarily controlled by the strong depolymerizing effect of CaCO3 assimilation that increases the number of structural sites critically important to accommodating network-modifying cations in the melt phase. The comparison between cumulates and magmatic skarns from the Colli Albani Volcanic District (Italy) and experiments from this study provides quantitative constraints on the geochemical evolution of olivine phenocrysts and their melt inclusions as a function of carbonate assimilation.

High-Energy Resolution Fluorescence Detected X-Ray Absorption Spectroscopy: A Powerful New Structural Tool in Environmental Biogeochemistry Sciences.

The study of the speciation of highly diluted elements by X-ray absorption spectroscopy (XAS) is extremely challenging, especially in environmental biogeochemistry sciences. Here we present an innovative synchrotron spectroscopy technique: high-energy resolution fluorescence detected XAS (HERFD-XAS). With this approach, measurement of the XAS signal in fluorescence mode using a crystal analyzer spectrometer with a ∼1-eV energy resolution helps to overcome restrictions on sample concentrations that can be typically measured with a solid-state detector. We briefly describe the method, from both an instrumental and spectroscopic point of view, and emphasize the effects of energy resolution on the XAS measurements. We then illustrate the positive impact of this technique in terms of detection limit with two examples dealing with Ce in ecologically relevant organisms and with Hg species in natural environments. The sharp and well-marked features of the HERFD-X-ray absorption near-edge structure spectra obtained enable us to determine unambiguously and with greater precision the speciation of the probed elements. This is a major technological advance, with strong benefits for the study of highly diluted elements using XAS. It also opens new possibilities to explore the speciation of a target chemical element at natural concentration levels, which is critical in the fields of environmental and biogeochemistry sciences.

Arsenic, lead, and uranium concentrations on sediments deposited in reservoirs in the Rio Grande Basin, USA–Mexico border

The El Granero reservoir is the last reservoir of the Rio Conchos before it joins the Rio Grande at the Mexico–USA border. This reservoir, together with the San Marcos reservoir, is located in the arid region of Chihuahua, Mexico. High, naturally occurring radioactivity levels, as well as high arsenic (As) concentrations, have been found in both reservoirs. The main goal of this research was to establish the spatial and temporal distribution of trace and radioactive elements in surface sediments and cores collected from these reservoirs. Sediment cores were dated using 210Pb and 137Cs measurements and applying the constant rate of supply (CRS) model. Major, trace, and radioactive elements were determined in surface samples and three sediment cores. Radioactive elements were determined by both alpha and gamma spectrometry. Major and trace elements were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using the EPA 3051a method. Enrichment factors (EF), contamination factors (CF), and pollution load indexes (PLI) were calculated in order to identify the human impact in both reservoirs, whereas the chemical index weathering (CIW) was used to assess differences in the degree of weathering. High uranium (U) enrichment (EFs = 24.9–54.7) was observed in core layers at the San Marcos reservoir, while in surface sediments, this enrichment was lower. The high variability of lead (Pb) and As in sediment cores from the Granero reservoir was attributed to human influence. Arsenic and Pb enrichment differences between entry and exit sediment cores were explained by the filtering capabilities of the elongated shape, the topography, and the presence of plants on the reservoir’s bed. The highest PLI was found at the entrance core of the Granero reservoir. The natural element concentration levels of As, Pb, and U were established at the Granero reservoir. High EFs for As and Pb suggest an anthropogenic origin of these pollutants at specific time intervals. High U concentrations in the San Marcos area are explained as naturally occurring. The concentrations of As in most of the studied sediments could pose a risk to human health by As ingestion, since they are above the probable effect level (PEL).

Heavy metals of Santiago Island (Cape Verde) top soils: Estimated Background Value maps and environmental risk assessment

In this work we present maps of estimates of background values of some harmful metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, and Zn) in the soils of Santiago Island, Cape Verde, analyse their relationships with the geological cartography, and assess their environmental risks. The geochemical survey (soil sampling at a spatial resolution of 3 sites per 10km2, sample preparation, geochemical analysis, data treatment, and mapping) was conducted following the guidelines proposed by the International Projects IGCP 259 and IGCP 360. The concentration of the selected elements was determined in the fraction <2mm. Each sample was digested with aqua regia and analysed by ICP-MS.The Estimated Background Value spatial distributions of the studied metals are found to be strongly linked to the geological cartography. These links are identified by a direct comparison of the geochemical maps with the geological cartography, and confirmed by either simple statistics and a Principal Component Analysis. The metals with higher loadings in the first Principal Component, Ni, Cr, Co, Cu, and V, clearly show the influence of a lithology rich in siderophile elements, typical of basic rocks and of its related minerals. The elements with higher loadings in the second Principal Component, Mn, Zn, Pb, As, Hg, and Cd, are chalcophile elements, except for Mn, but an anthropogenic contamination for these elements cannot be discarded.We propose an index to numerically access the environmental risk of one element, which we denominate by Environmental Risk Index, and a Multi-element Index which is simply the average taken over all elements. The occurrence of values greater than 1 in the maps of the Environmental Risk Index shows where the content of the respective element is above the permissible levels according to the available legislation for agricultural and residential purposes. The same applies to the multi-element risk index maps. High values of these risk indices are found, both for agricultural and residential purposes, for Co, Cr, Ni, Cu, and V. These metals are precisely those with higher loadings in PC1, which are demonstrated to be of natural origin in Santiago. This behaviour is also shown in the Multi-element Environmental Risk maps computed with these five metals. The high natural concentration levels of heavy metals at some areas of Santiago should be of concern not only to scientists but also to policymakers. To further evaluate the environmental risks associated with the presence of these metals, their bioavailability should be assessed in future works.

Trace element fluxes and natural potential risks from 210Pb-dated sediment cores in lacustrine environments at the Central Mexican Plateau

The accumulation, enrichment and provenance of selected trace metals (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, V and Zn) were studied in sediment cores collected from three lakes located in the Central Mexican Plateau, selected on the basis of their contrasting degree of urbanization: Santa Elena Lake, in a rural and remote area; El Tule Lake, in a rural and slightly urbanized area; and Chapala Lake, in a highly urbanized area. Grain size, magnetic susceptibility and sedimentary constituents such as organic carbon, calcium carbonate, as well as major (Al, Fe, Mn) and minor (Ca, Li, Rb, Sr, Th) elements were analyzed to explain the concentration trends of trace metals. Factor analysis (FA) was used to assess the provenance of the trace elements. The highest metal enrichment factor (EF) above natural concentration levels was found at Chapala Lake for Ag (EF=3.9), although other trace element EF in all lakes was <2.0, indicating slight contamination. However, the concentration levels of Cr and Ni in all lakes, Hg and Zn in Chapala Lake, Cu in El Tule Lake and As in Santa Elena Lake were above international benchmarks for which adverse effects are expected to occur frequently, even for those metals only slightly enriched (e.g. As, Cr). Through FA, the terrigenous contribution was identified as the most important source of trace metals to the three lakes, most likely related to deforestation and erosion of the surrounding areas, followed by atmospheric transport of volcanic ashes, rather than to direct sources.

Distribution and temporal variation of selected heavy metals in sediment of River Osara mainstream drainage in North Central Nigeria

The concentration levels of selected iron-ore composite heavy metals were investigated in mainstream sediment of River Osara traversing by Itakpe iron-ore deposit and mining area in North Central Nigeria. The sediment samples collected along the drainage course, up-, mid- and downstream for 24 months were digested using standard methods, and levels of Cd, Cr, Ni, Cu and Pb determined using flame atomic absorption spectrophotometer (AAS). The mean concentrations of Pb, 15.63±2.35-18.98±2.04 mg/kg was the highest followed by Ni, 5.20±1.79-15.83±3.04 mg/kg, relative to other metals. The concentrations of Cu and Cr were 3.18±1.14-10.02±2.89 mg/kg and 1.12±0.27-20.93±4.89 mg/kg,respectively, while Cd, 0.24±0.12-0.40±0.26 mg/kg was the least. There was significant (p < 0.05) positive correlation between the concentration of the measured metals with organic carbon level in sediment, with coefficient of correlation γ=0.68, Cd; γ=0.69, Ni; γ=0.54, Cr; γ=0.85, Pb and γ=0.81, Cu implying that metals levels in sediments are partly defined by organic carbon levels. Seasonal fluctuations were observed in sediment concentrations of metals with higher concentration during dry season than in wet season.The concentration of heavy metals in River Osara sediment by Itakpe iron-ore deposit and mining area are low and within natural concentration levels. The result could serve as benchmark required for effective water management and environmental monitoring. Key words: Heavy metals, concentration, bottom sediment, iron-ore, monitoring, River Osara, Nigeria.

Hydrochemical trends for public supply well fields in The Netherlands (1898–2008), natural backgrounds and upscaling to groundwater bodies

Summary Statistical trend analysis is applied to a 110 years long groundwater quality time series from the national network of public supply well fields (PSWFs) in The Netherlands. Such a groundwater quality monitoring network should be available in many countries, so that approaches and experiences presented here could be of interest world wide. Trendless concentration data series measured in the early years, which should bear the least anthropogenic influences, are selected to quantify the regional natural background concentration levels (NBLs) of groundwater resources at the depth of abstraction. Trends in the period 1960–2005, which contained a more homogeneous data set, are normalized to drinking water standards, mapped in planar view and cross sections, and used to identify the responsible hydrochemical processes. Seven representative trend bundles are defined by aggregation of trends for individual chemical parameters. Trend reversals due to either environmental sanitation measures or well field adaptation measures are identified by comparing significant trends obtained for two different periods within the time series. Natural background levels (NBLs) for individual PSWFs are upscaled to the national groundwater body level (as reported to EU), by aggregating them according to a PSWF typology based on a Hydrochemical System Analysis. This aggregation method groups together PSWFs that deliver waters of the same origin and similar hydrogeochemical environment. PSWFs delivering old groundwaters with a very stable quality are clearly differentiated from PSWFs pumping highly vulnerable aquifers characterized by strongly deteriorating water quality trends. Results are presented on national maps of The Netherlands with NBLs and water quality trends for selected major constituents. A normalized concentration change index (NCC) is defined and mapped to relate the quality difference between a recent survey (in 2008) and calculated NBLs, to the EU drinking water standards.

High-pressure Hydrous Phase Relations of Radiolarian Clay and Implications for the Involvement of Subducted Sediment in Arc Magmatism

Melting of subducted oceanic sediment is considered to play a key role in the generation of the arc magmatic signature. We have carried out an experimental study on hydrous melting of trace element-doped radiolarian clay at 3 GPa and temperatures from 700 to 1250°C; 7–15 wt % H2O was added to the sediment to simulate the effects of flushing by fluids derived from underlying dehydrating lithologies, such as serpentinites. Melting begins at ∼750°C owing to the breakdown of phengite + clinopyroxene + coesite and a hydrous melt coexists with mostly garnet + kyanite ± quartz up to around 1250°C. Rutile and Fe–Ti oxides are present to ∼1000°C. Very high degrees of melting occur at relatively low, supra-solidus temperatures (e.g. with 15 wt % added H2O, the clay is ∼54% molten at 800°C), in marked contrast to fluid-absent melting of similar rock compositions, which yields negligible melt fractions (<∼10%) for similar temperatures. A particular focus of this study is residual monazite, which preferentially incorporates light rare earth elements (LREE) and Th, thereby exerting a powerful control on the Th/La ratio of sediment-derived fluids and melts. In contrast to previous studies, we find that DTh/La varies widely and can be significantly above or below unity. Our dataset suggests that this pattern arises because the various members of the monazite solid solution series are influenced independently by different parameters. We also demonstrate that monazite–melt partition coefficients based on doped experiments cannot be used uncritically to predict fractionation processes in nature because of monazite–huttonite solid solution. However, extrapolation of our results to natural concentration levels suggests fractionation of Th from La in the presence of monazite in most cases. We propose that a solid residue with little or no residual monazite is needed to explain a wide range of geochemical features of arc magmas, including Th/La ratios. A monazite-free residue can be achieved at relatively low sub-arc temperatures provided that enough water is made available (e.g. through antigorite breakdown) to promote sufficient melting to dissolve the entire LREE + Th budget of the sediment.

Distribution of uranium in German bottled and tap water

The results presented in this paper on uranium in bottled and tap water were determined within the scope of the project “European Groundwater Geochemistry: Bottled Water” of the Geochemistry Expert Group of EuroGeoSurveys. The analyses of bottled water provide an inexpensive approach to obtain information about European groundwater geochemistry. For this study, the uranium concentrations in 1785 European mineral water samples were analyzed by ICP–QMS in the BGR laboratories. The dataset is used to obtain a first impression about natural concentration levels and variation of uranium in groundwater (and bottled water) at the German and European scale. A range of < 0.0005–16.0 µg U/L (median 0.17 µg/L) was obtained in 908 bottled water samples in Germany. A range of 0.00115–9.0 µg U/L (median 0.073 µg U/L) was obtained for tap water from 163 municipal tap water systems. The regional distribution of uranium in the analyzed bottled and tap water is influenced primarily by lithological (Bunter and Keuper strata, crystalline basement rocks, Permian strata, and loess) and anthropogenic (old mining districts, phosphate fertilizers, and industrial emissions) factors. Elevated uranium concentrations (> 2 µg U/L) in bottled water have geological sources and were found in Hesse, Thuringia, North Rhine–Westphalia, Saxony, southern part of Saxony–Anhalt and in Baden–Württemberg (Black Forest). Bunter and Keuper sandstone are the main source of uranium, followed by Permian and crystalline basement aquifers. The EU Guidelines for Drinking Water and the German Drinking Water Regulations give no upper limit for uranium; however, a provisional value of 15 µg U/L exists in the Guidelines for Drinking Water Quality of the World Health Organization. The only value for German bottled water is 2 µg U/L, above which the label may not say that the water may be used for the preparation of baby food. Nevertheless the uranium content of bottled and tap water needs to be monitored and controlled by governmental offices. In all, 14% of all the analyzed German bottled water samples contain > 2 µg U/L and 15% of all analyzed European bottled water. Only one German bottled mineral water sample exceeded the guideline value of 15 µg U/L in 2008.

Halogen diffusion in magmatic systems: Our current state of knowledge

Diffusion of halogens has the potential to influence petrogenetic processes in magma chambers and conduit degassing processes. This contribution reviews our current state of knowledge concerning halogen diffusion and the influence of halogens on the diffusion of major elements in silicate melts. The addition of halogens to silicate melts at common, natural concentration levels will have little effect on the diffusion of major elements. However, the differences between the diffusivity of water, the diffusivities of halogens, and the diffusivity of sulfur are significant enough that during melt inclusion entrapment, or during rapid bubble or crystal growth, diffusive fractionation between water and the halogens, and between halogens and sulfur, are expected to occur and can influence the compositions of melt inclusions, crystals and volcanic gases.