The session aims at collecting contributions from all scientists daily faced with the need of discriminating between what is natural and what is the result of the interaction of humans with the surrounding environment, with respect to elemental concentrations. Commonly, geoscientists involved in environmental projects are requested to define local or regional reference concentration values for those chemical substances (mostly potentially harmful elements) and, recently, radioisotopes which can be originating from both geological materials and human driven processes.
To discriminate natural contributions from anthropogenic ones is a very complicated task and several scientists have applied different methods and multiple approaches (from statistics to the weight of evidence) in order to provide guidance and reliable solutions to government institutions and professional stakeholders.
Case studies on solid matrices (soil, sediments, etc.), natural water and other environmental media are of interest for the session together with more methodological studies mostly focusing on the proposal of innovative techniques for defining these values.
Dorota Moroniak-Wawryszuk, Mateusz Wawryszuk, Stanisław Chmiel, Miłosz Huber, Paweł Kramarz, Lesia Lata, and Sebastian Skupiński
In this study the geochemical background of waters of Kola Peninsula in the context of decreasing the athropogenic pollution in that region was indicated. The study was conducted on 14 water samples from different phases of hydrological cycle- precipitation water, snow-melting water, ground water, river water, lake water, sea water; also 12 samples of rocks and soils were used. pH of waters, conductivity, isotopic ratio of δ18O i δD, concentration of ions (anions and cations) along with metal ions were analysed. For conductivity measure InoLab 1 (WTW) was used, cations and anions were indicated by ions chromatograph (Metrohm MIC 3), metal ions were indicated by spectrometer ICP-MS (Thermo Xseries2). Laser analyzer PICARRO L2130 was used for defining the isotopic ratio of δ18O i δD. Soils and rocks samples were analysed using scanning electrone microscope (Hitachi SU6600) with EDS add-on and spectroscope XRF Epsilon 3 (Pananalytical).
The study showed significant impact of bedrock and soils on ion composition of waters in different locations in Kola Peninsula in example on several geogenical metal ions of P, F, Cl, Fe, Mn, Cu, Ni, S. Chemical composition of water backround is strictly related to polymetalic rocks and metal ores of the Baltic Shield which build analysed area. The waters' richness in alkali minerals is due to alkaline bedrock occuring in numerous areas of Kola Peninsula. The content of metal ions like Zn, Pb, Cr, Cd in numerous water samples indicates severe anthropogenic influence on water composition which can be especially noticed in the composition of surface water affected by the nearby heavy industry plants thus pollution of surface water.
Analisys of water samples proves significant impact of geological structure on chemical composition of water and should be considered in reclamation of natural environment of Kola Peninsula from anthropogenic pollution.
How to cite:
Moroniak-Wawryszuk, D., Wawryszuk, M., Chmiel, S., Huber, M., Kramarz, P., Lata, L., and Skupiński, S.: Determination of geochemical backgroud of waters of Kola Peninsula in order to decrease anthropogenic pollution in analysed area, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-761, https://doi.org/10.5194/egusphere-egu2020-761, 2020.
Environmental geochemistry is playing an increasingly important role in mineral exploration, environmental management, agricultural practices as well as links with health. With rapidly growing databases available at regional, national, and global scales, environmental geochemistry is facing the challenges in the “big data” era. One of the main challenges is to find out useful information hidden in a large volume of data, with the existence of spatial variation found at all the sizes of global, regional (in square kilometers), field (in square meters) and micro scales (in square centimeters). Meanwhile, the rapidly developing techniques in machine learning become useful tools for classification, identification of clusters/patterns, identification of relationships and prediction. This presentation demonstrates the potential uses of a few practical spatial machine learning techniques (spatial analyses) in environmental geochemistry: neighborhood statistics, hot spot analysis and geographically weighted regression.
Neighborhood (local) statistics are calculated using data within a neighborhood such as a moving window. In this way, spatial variation at the local level can be quantified and more details are revealed. Hot spot analysis techniques are capable of revealing hidden spatial patterns. The techniques of hot spot analysis including local index of spatial association (LISA) and Getis Ord Gi* are investigated using examples of geochemical databases in Ireland, China, the UK and the USA. The geographically weighted regression (GWR) explores the relationships between geochemical parameters and their influencing factors at the local level, which is effective in identifying the complex spatially varying relationships. Machine learning techniques are expected to play more important roles in environmental geochemistry. Challenges for more effective “data analytics” are currently emerging in the era of “big data”.
How to cite:
Zhang, C.: Towards spatial machine learning to reveal hidden patterns and relationships in national and international geochemical databases, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2179, https://doi.org/10.5194/egusphere-egu2020-2179, 2020.
The definition of natural background concentration levels (NBLs) of geogenic trace metals in groundwater is a challenging issue, particularly in areas where anthropogenic activities are also present. The estimation of NBLs, in combination with environmental quality standards, in such areas is particularly important for the establishment of relevant groundwater threshold values. Over 100 groundwater samples were collected and analysed from four Cr(VI) impacted, alluvial groundwater bodies of central Greece during two consecutive hydrologic years. A common feature of the examined aquifers is the presence of weathered ultramafic rock material in the alluvial sediments. Most sampled boreholes (79 %) are used for irrigation, whereas 21 % of them are used for domestic drinking water supply. Hexavalent Cr concentrations in groundwater, ranging from below detection limit to 430 μg/L, have been attributed to both geogenic and anthropogenic factors. The scope of the present study is to estimate the NBL of Cr(VI) by using a classical statistical approach and a deterministic preselection method and test the comparability of results. In the statistical approach the distribution of samples versus Cr(VI) concentrations has been explored by using probability plots. In this way, the concentration variations within the examined groundwater bodies can be studied and the presence of sub-populations becomes evident by breaks in the slope. In the instance of the preselection method, the concentrations of a set of additional analyzed parameters in ground water, including major water ions and nitrate as well as dissolved oxygen, have been taken into account in order to categorize the samples into two groups of low and high anthropogenic influence, respectively. The comparability of the results derived by the two approaches are discussed in the context of EU Water Framework Directive.
How to cite:
Argyraki, A., Pyrgaki, K., Kelepertzis, E., Botsou, F., and Megremi, I.: Estimation of natural background level of Cr(VI) in ultramafic rock related alluvial aquifers of central Greece: Comparison of results by statistical and deterministic preselection method approaches, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11699, https://doi.org/10.5194/egusphere-egu2020-11699, 2020.
Soil pollution is a worldwide concern and several countries are established guidelines. In the case of Chile, the very diverse soils characteristics along the country made difficult to set guidelines to acceptable levels of potentially toxic elements (PTEs) in soils. However, due to several reasons such as anthropogenic contamination, and increment of erosion rates there is urgency in to establish guidelines values to this parameters. In Chile, the most of abandoned mining wastes are located in the northern part which could negatively have impacted the ecosystem and human health. Thus, in absence of guidelines to PTEs in soils, the use of regional geochemical baseline (GBL) as a reference values could be a first approach to preliminary determine pollution levels of PTEs in soils. The objective of this study was to use the calculated GBL values to determine the influence of mining activities on the levels of PTEs in soils and to determine the spatial distribution maps of PTEs. A regional mapping of soils was conducted in northern part of Chile during 2017-2018 and the pH, electrical conductivity, redox potential and concentration of PTEs was determined. A systematic sampling in a 20,000 square-kilometer area was conducted and 467 rural top and sub soil samples were taken to determine their physical and chemical composition. The content of PTEs was determined by ICP-OES. The GBL values were estimated following the upper-whisker limit method. The pH, electrical conductivity, and redox potential of soils were 4.9-9.5, 10.5-56,000 mS/cm, and 89.7-348.3 mV, respectively. The median concentration of Mn (695.9 mgkg-1) was the highest followed by V (148.4 mgkg-1), Ni (75.2 mgkg-1), Zn (59.7 mgkg-1), Cu (59.0 mgkg-1), Sb (34.0 mgkg-1), As (18.3 mgkg-1), Cr (17.9 mgkg-1), Sn (17.5 mgkg-1), Pb (14.6 mgkg-1), Co (13.0 mgkg-1), Cd (12.9 mgkg-1), Hg (3.6 mgkg-1), and Mo (3.3 mgkg-1). The GBL for Cu, Zn, V, As, Mo, and Sb were higher than the reported average for world soils. The spatial distribution maps of Cu, Pb, Zn, Cr, As and V were used to determine pollution levels. Statistical correlation models showed the influence of either abandoned mining sites or active mining operation on the pollution levels of PTEs in the surrounding soils. The geochemical baseline values could contribute for government decision-makers to choose the best available remediation technologies for the impacted area.
How to cite:
Reyes, A. and Delgado, J.: Spatial distribution maps of Cu, Pb, Zn, Cr, As and V in rural soils in northern part of Chile: The use of geochemical baseline values as an index in environmental assessment., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12342, https://doi.org/10.5194/egusphere-egu2020-12342, 2020.
Urban areas are typical examples of disturbed natural environments where human development has significantly altered the geochemical background of trace elements in surface soil and sediment. Road dusts and gully sediments are reflective of a wide range of anthropogenic activities in cities and are a useful resource for evaluating the level and distribution of trace metal contaminants in the surface environment. The evaluation of contamination in these sinks provides useful information of how the drainage system of the cities contributes to urban pollution.
A total of 26 urban road deposited sediment samples were collected from different altitudes within the Athens basin based on the hydrographic network of the area. The samples were analyzed for 33 elements following an aqua regia dissolution. Sample organic carbon content, pH and grain size distribution have been determined and magnetic susceptibility measurements and mineralogical analysis by powder X-ray diffraction were also performed in order to identify possible factors explaining the variability of elemental concentrations. Also, sixteen samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) in order to detect their sources in the Athens urban environment.
Aqua regia concentrations in the analyzed sediments reached maximum values of 18 mg/kg for As, 2 mg/kg for Cd, 14 mg/kg Co, 193 mg/kg Cr, 640 mg/kg Cu, 25600 mg/kg Fe, 112 mg/kg Ni, 3092 mg/kg Pb and 1469 mg/kg Zn. The median values of the studied elements were estimated to be 13 mg/kg for As, 1 mg/kg for Cd, 8 mg/kg Co, 98 mg/kg Cr, 215 mg/kg Cu, 17154 mg/kg Fe, 70 mg/kg Ni, 267 mg/kg Pb and 598 mg/kg Zn, respectively. With the exception of Co and As, both maximum and median values were found to be much higher than those in Athens soils from a previous study. Cluster analysis on the results identified two major groups of elements based on an over 43.59% criterion of similarity. The first cluster contains elements of geogenic origin including Co, Fe, Mn and Ni. The parameters of % organic carbon, magnetic susceptibility, Cu and Cr are grouped together in a second cluster showing a similarity level over 65% while a third cluster groups together Pb, Zn and Cd and is interpreted as anthropogenic.
In a previous systematic baseline study of Athens, it was found that the major factor controlling variability of the chemical composition of surface soil was the bedrock chemistry, resulting in a significant enrichment in concentrations of Ni, Cr, Co and possibly As. Anthropogenic influences were also significant in soil, controlling a spectrum of elements that are typical of human activities, i.e. Pb, Zn, Cu, Cd, Sb, and Sn. The clustering of elements in the present study indicates that although the geogenic origin of some elements is retained in road sediments, a greater number of elements indicate anthropogenic influence in their distribution. Briefly, it was documented that road deposited sediments reflect the characteristics of the anthropogenic activities taking place, and that traffic- related activities are the primary sources of contaminants.
How to cite:
Kourgia, P.-M. and Argyraki, A.: Trace element concentrations in road deposited sediments of Athens, Greece: A comparison with baseline soil data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13246, https://doi.org/10.5194/egusphere-egu2020-13246, 2020.
Mining is an important pillar of economic growth of many African countries. However, problems arising from this activity pose serious challenges, which most of these countries have difficulties to address properly because of poor environmental governance as highlighted in the Africa Mining Vision. Many African countries also lack a precise inventory and assessment of environmental impacts of abandoned and derelict mines. As a consequence, there is an urgent need to evaluate the true extent of the detrimental effects of metal and metalloid pollutants and their impact on human and animal health, as well as on ecosystems. Between 2013 and 2017 and thanks to a Partnership Programme between UNESCO and the Swedish International Development Cooperation Agency (Sida), a network of over 100 Earth scientists from 29 Africa assessed the impacts of mining activities in sub-Saharan Africa. The project intended to provide crucial scientific knowledge that will contribute to understanding the factors that control cycling of pollutants from mine sites (abandoned or active) to soils, water and vegetation and the impact on the food chain. We anticipate that the results of the project will be used to improve the environmental norms in individual countries in Sub-Saharan Africa and the efficiency of governments in addressing the challenges related to the adverse effects of mining activities. The preliminary results of the project have recently been published as a Special Issue in the Journal of Geochemical Exploration. During the presentation, we intend to highlight few examples where mining activities alone or in interaction geological background are contributing to threat the ecosystem and health of neighbouring communities. We will also draw the lessons learnt from the implementation of this continental-scale project.
How to cite:
S. Félix, T.: Highlights on a UNESCO/Sida project to assess the environmental and health challenges of mining activities in Sub-Saharan Africa, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18709, https://doi.org/10.5194/egusphere-egu2020-18709, 2020.
Roland Stumpf, Dörte Budziak, Nico Deus, and Jörg Elbracht
Uranium is a trace metal yielding an average concentration in the Earth’s crust of about 2 to 4 mg/kg, and it occurs naturally in low levels in rock, soil, and water. Although widely known for its radioactive properties, at low levels dissolved uranium is more harmful by its chemical toxicity. The World Health Organisation (WHO) recommends a maximum concentration of 30 µg/l uranium in tap water, as well as a tolerable daily intake limit of 0.6 µg/kg body weight. Since 2011, tap water in Germany must not exceed uranium concentrations of 10 µg/l.
The uranium budget of the groundwater in Lower Saxony comprises mainly of geogenic input through water-rock interaction along the hydrological cycle and within the respective hydrogeological units, and possibly through century-old mining activities, and more recently the use of uranium bearing mineral fertilisers in farming. While the vast majority of uranium concentrations are significantly below 10 µg/l with many values below detection limit, some detached areas display elevated uranium with one confined maximum concentration of 124 µg/l. In order to determine uranium background values, statistical analyses accounted for hydrogeological units of the aquifer, land use, and well depths. Anomalous peak concentrations are unlikely to be a result of variations in geogenic background values alone and require further investigations. A possible rise of uranium concentrations caused by a downward shifting redox front, as proposed in other regions in Northern Germany, is yet to be identified in Lower Saxony.
How to cite:
Stumpf, R., Budziak, D., Deus, N., and Elbracht, J.: Spatial anomalies of uranium background levels in groundwater of Lower Saxony, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21458, https://doi.org/10.5194/egusphere-egu2020-21458, 2020.
Stefano Albanese, Annalise Guarino, Daniela Zuzolo, Antonio Aruta, Domenico Cicchella, Antonio Iannone, Raffaele Melito, Francesco Verrilli, and Alessandro Fedele Gianvito
Radon is an ubiquitous radioactive gas proceeding from the decay of some radionuclides, mostly abundant in igneous rock and volcanic soils; it is the main source of natural radiation to which human beings are exposed during their life. Campania, a region located on the south-western sector of the Italian peninsula, has a territory mostly characterized by the presence of volcanic lithotypes and sediments. An empirical method was applied to determine the concentration of Rn-222 in soils of Campania region by using radiometric and compositional data recorded in two extensive different environmental prospecting campaigns completed in 2003 and 2015, respectively.
Radiometric surveys were carried out with a nominal density of 1 station per 5 sqkm with a GRS-500 portable scintillometer produced by Scintrex Ltd (Ontario, Canada); topsoil samples were collected at 3535 sites regularly spread across the whole regional area with a nominal density of 1 sample per sqkm. Samples destinated to chemical analyses were analysed by ICP-MS after an aqua regia digestion at the ACME Analytical Laboratories Ltd (now Bureau Veritas) in Vancouver, Canada.
Specifically, the concentrations of U, Th and K in topsoil samples and the activity (gamma radiation) generated by the decay of U-238, Th-232 and K-40 (expressed as Bq) at each measurement station were used as proxies in order to determine the variation of Rn-222 flux from the ground and to estimate the distribution pattern of geogenic radon potential (GPR) across the region.
The use of a sequence of specific equations led to estimate the terrestrial gamma dose rate (nSv/h) at 1 m above the ground surface starting from both datasets and, therefore, allowed the generation of the Rn-222 flux and GPR maps for the whole regional territory.
Both Radon flux and GPR raster maps were produced by mean of some specific geospatial elaborations and the estimated values were compared among them and validated trough the completion of some field measurements.
How to cite:
Albanese, S., Guarino, A., Zuzolo, D., Aruta, A., Cicchella, D., Iannone, A., Melito, R., Verrilli, F., and Gianvito, A. F.: Extending the concept of background to soil gas: natural radon concentrations in soils of Campania region., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22687, https://doi.org/10.5194/egusphere-egu2020-22687, 2020.