National Institute of Geophysics, Geodesy and Geography

Abstract Nature-based solutions (NBS) can protect, manage and restore natural or modified ecosystems. They are a multidisciplinary, integrated approach to address societal challenges and some natural hazards effectively and adaptively, simultaneously providing human well-being and biodiversity benefits. NBS applications can be easily noticed in circular cities, establishing an urban system that is regenerative and accessible. This paper aims to offer a review on NBS for urban water management from the literature and some relevant projects running within the COST Action ‘Implementing nature-based solutions for creating a resourceful circular city’. The method used in the study is based on a detailed tracking of specific keywords in the literature using Google Scholar, ResearchGate, Academia.edu, ScienceDirect and Scopus. Based on this review, three main applications were identified: (i) flood and drought protection; (ii) the water-food-energy nexus; and (iii) water purification. The paper shows that NBS provide additional benefits, such as improving water quality, increasing biodiversity, obtaining social co-benefits, improving urban microclimate, and the reduction of energy consumption by improving indoor climate. The paper concludes that a systemic change to NBS should be given a higher priority and be preferred over conventional water infrastructure.

The paper describes results of the studies devoted to the solar activity impact on the Earth’s upper atmosphere and ionosphere, conducted within the frame of COST ES0803 Action.

Abstract We present a new GPS velocity field covering the peri‐Adriatic tectonically active belts and the entire Balkan Peninsula. From the velocities, we calculate consistent strain rate and interpolated velocity fields. Significant features of the crustal deformation include (1) the eastward motion of the northern part of the Eastern Alps together with part the Alpine foreland and Bohemian Massif toward the Pannonian Basin, (2) shortening across the Dinarides, (3) a clockwise rotation of the Albanides‐Hellenides, and (4) a southward motion south of 44°N of the inner Balkan lithosphere between the rigid Apulia and Black Sea, toward the Aegean domain. Using this new velocity field, we derive the strain rate tensor to analyze the regional style of the deformation. Then, we devise a simple test based on the momentum balance equation, to investigate the role of horizontal gradients of gravitational potential energy in driving the deformation in the peri‐Adriatic tectonically active mountain belts: the Eastern Alps, the Dinarides, the Albanides, and the Apennines. We show that the strain rate fields observed in the Apennines and Albanides are consistent with a fluid, with viscosity η ∼ 3×10 21 Pa s, deforming in response to horizontal gradients of gravitational potential energy. Conversely, both the Dinarides and Eastern Alps are probably deforming in response to the North and North‐East oriented motion of the Adria‐Apulia indenter, respectively, and as a consequence of horizontal lithospheric heterogeneity.

Mapping and Assessment of Ecosystems and their Services (MAES) are central to the EU Biodiversity Strategy to 2020. Action 5 of the Strategy’s second target asks all EU member states to map and assess the state of ecosystems and their services in their national territories. Such comprehensive mapping and assessment builds on several individual tasks and their systematic integration. Therefore, an integrated and operational framework is needed, supporting and coordinating these activities. The presented framework builds on existing work done by the European Commission’s MAES Working Group and provides a clear nine-step approach including the identification of relevant questions or themes to be addressed, identification and mapping of ecosystem types, ecosystem condition and ecosystem services, their integration and dissemination of results. This framework can be used to set-up related research and development initiatives and to guide involved scientists, decision-makers and practitioners through the different steps and related tasks of the process.

The river catchment management is a complex problem, which requires analysis of massive amounts of mandatory monitoring data on analytical, spatial, and temporal level. The present study deals with the application of a novel water quality assessment approach combining water quality index (WQI) developed by the Canadian Council of Ministers of the Environment (CCME) and self-organizing maps of Kohonen (SOM). The study is carried out by using long-term water quality monitoring data (2008–2018) collected from 10 sampling stations located in the Mesta River catchment, Bulgaria. In the first step, the assessment of annual water quality categories of each sampling station was estimated by the calculation of CCME WQI modified according to the Bulgarian legislation. In the next step, all annual water quality categories (n = 105) characterized by the factors used for CCME WQI calculation (scope, frequency, amplitude) underwent SOM analysis. The results of implementation of the WQI factors in SOM calculations reveal similar groups of annual water quality categories with specific CCME WQI patterns among the whole river catchment. The obtained patterns represent different water quality situations, which could be treated by different management activities. Additionally, the visualization advantages of the SOM algorithm allowed for detection of the water quality temporal changes and similarity between sampling stations among river catchment. Thus, the combination between integral CCME WQI assessment and multivariate technique SOM made it possible to achieve a precise river catchment water quality assessment, which could be used by water management authorities.

SUMMARY We calculate and analyse the coordinate time-series of 282 permanent GPS stations located in Greece and 47 in surrounding countries. The studied period is 2000–2020. The average GPS time-series length is 6.5 yr. The formal velocity uncertainties are rescaled to be consistent with the velocity scatters measured at 110 pairs of stations separated by less 15 km. We remove the effect of the crustal earthquakes of Mw ≥ 5.3. We quantify and model the post-seismic deformations. Two relaxation times are usually needed: one short of some weeks and one long of 1 yr or more. For the large Mw = 6.9 events of Samothraki 2014 and Methoni 2008, the post-seismic deformation equals or exceeds the coseismic one. We detect at three stations a deformation transient in May 2018 that may correspond to a slow earthquake beneath Zakynthos and northwest Peloponnese, with equivalent magnitude 5.8. The density and accuracy of the velocities make it possible to better quantify several characteristics of the deformation in the Aegean, in particular: (i) the transition from the Anatolian domain, located in the southeast, to the European domain through the western end of the North Anatolian fault; (ii) the north–south extension in the western Aegean; (iii) the east–west extension of the western Peloponnese; (iv) the clockwise rotation of the Pindos; (v) the north–south extension in central Macedonia. Large parts of the central Aegean, eastern Peloponnese and western Crete form a wide stable domain with internal deformation below 2 nstrain yr−1. We build a kinematic model comprising 10 crustal blocks corresponding to areas where the velocities present homogeneous gradients. The blocks boundaries are set to fit with known localized deformation zones, for example, the rift of Corinth, the North Anatolian fault and the Katouna fault. When the velocity steps are clear but not localized, for example, through the Peloponnese, the boundary line is arbitrary and represents the transition zone. The model fits the velocities with a root-mean-square deviation of ±0.9 mm yr−1. At the boundaries between blocks we compare the predicted and observed deformations. We find shear rates of 7.4 and 9.0 mm yr−1 along the Movri and Katouna faults, 14.9 and 8.7 mm yr−1 along the North Anatolian fault near Lemnos and near Skopelos respectively, extension of 7.6, 1.5 and 12.6 mm yr−1 across the Gulf of Patras, the Trichonis Lake and the Ambracian Gulf. The compression across western Epirus is 3.7 mm yr−1. There is a dextral transtensional movement of 4.5 mm yr−1 between the Amorgos and Astypalea islands. Only the Ionian Islands region shows evidence of coupling along the subduction interface.

Abstract A global background total electron content (TEC) model is built by using the Center for Orbit Determination of Europe (CODE) TEC data for full 13 years, 1999–2011. It describes the climatological behavior of the ionosphere under both its primary external driver, i.e., the direct photo‐ionization by incident solar radiation, and regular wave particularly tidal forcing from the lower atmosphere. The model construction is based on the very different time scales of the solar cycle, seasonal, and diurnal TEC variabilities (at least an order of magnitude); this leads to modulations of shorter‐period variabilities with periods of the longer ones. Then the TEC spatial‐temporal variability is presented as a multiplication of three separable functions. The solar activity is described by both parameters: F10.7 and its linear rate of change K F while the seasonal variability is presented by sine functions including four subharmonics of the year. The diurnal variability of the TEC model is described by 2D (longitude‐time) sine functions with zonal wave numbers up to 4 and 4 subharmonics of the solar day. The model offers TEC maps which depend on geographic coordinates (5°×5° in latitude and longitude) and UT at given solar activity and day of the year. The presented background model fits to the CODE TEC input data with a zero systematic error and an RMS error of 3.387 TECU. It is able to reproduce the well‐known ionospheric structures as Weddell Sea Anomaly and some longitudinal wave‐like structures.

Uncertainty over the data quality of Volunteered Geographic Information (VGI) is the largest barrier to the use of this data source by National Mapping Agencies (NMAs) and other government bodies. A considerable body of literature exists that has examined the quality of VGI as well as proposed methods for quality assessment. The purpose of this chapter is to review current data quality indicators for geographic information as part of the ISO 19157 (2013) standard and how these have been used to evaluate the data quality of VGI in the past. These indicators include positional, thematic and temporal accuracy, completeness, logical consistency and usability. Additional indicators that have been proposed for VGI are then presented and discussed. In the final section of the chapter, the idea of integrated indicators and workflows of quality assurance that combine many assessment methods into a filtering system is highlighted as one way forward to improve confidence in VGI.

In December 2019, a relatively unknown disease was detected in the city of Wuhan, the capital of the Chinese Hubei province. Identified as a new respiratory virus and largely defined as a novel type of coronavirus (Huang et al., 2020), what is known as SARS-CoV-2 but commonly referred as COVID-19, has spread worldwide with unprecedented speed and infection rate. The World Health Organization (WHO) declared a global health emergency on 30 January 2020 which further escalated to a worldwide global pandemic declared on 11 March 2020. At the time of writing in mid-May 2020, around 4.5 million infections had been reported with nearly 300,000 cases with a fatal outcome (John Hopkins University, 2020). Although the world has previously been exposed to notable epidemics/pandemics such as Ebola, severe acute respiratory syndrome (SARS) and Zika (Buheji & Ahmed, 2020), none of them has had such a notorious and holistic impact on the world’s economy and society. The OECD and the International Monetary Fund (IMF) have already warned that the overall economic impact is expected to be substantially higher than the global financial crisis in 2008 (Hunt, 2020). The tourism industry has been one of the hardest hits by the disruption from the COVID-19 with the imposed restrictions on both international and domestic travel, and the immediate closure of hotels, restaurants and visitor attractions. According to UNWTO (2020), the industry is expected to decline by 20–30% with an anticipated loss of around 300 USD-450 billion. As WHO currently “does not recommend any travel or trade restriction based on the current information available” (WHO, 2020), the tourism as we know it has disappeared and “overtourism” (Milano et al., 2019) has become “non-tourism at all”. As Niewiadomski (2020) points out, the world is now experiencing a “de-globalization” with around 90% of the world’s population subject to a certain level of travel restrictions, imposed home-stay lockdowns or arrival quarantines (Hall et al., 2020; Gössling et al., 2020). As Novelli et al. (2018) argue, there is a limited academic scholarship on health-related crisis and their impact on the tourism industry, particularly in the developing world. Despite the notable and timely appearance of many studies focused on COVID-19 and tourism, the majority of them are conceptual in nature and more focused on the “transformation” of tourism from a range of social science perspectives (see for example, Ateljevic, 2020; Brouder, 2020; Cheer, 2020; Higgins-Desbiolles, 2020; Nepal, 2020; Prideaux et al., 2020). Our paper focuses on another crucial dimension of the post-COVID-19 era – the importance of safety, sanitation and hygiene in the context of tourism and hospitality, and more specifically, sanitation measures as a decision-making factor for choosing an accommodation provider and willingness of the tourists to use their own sanitation products to ensure good personal hygiene.

Abstract The vast thickness (>10 km) of relatively undeformed Cambrian to Recent sedimentary cover of the Moesian Platform in Romania and Bulgaria offers an exceptional record of Cimmerian and Alpine tectonics in the surrounding Carpathian and Balkan thrust-fold belts. Above the Hercynian unconformity, Permian to Middle Triassic continental to shallow marine sediments deposited in a facies succession are quite typical for the European passive margin. Widespread Anisian-Carnian vol- canism indicates an aborted rifting period also marked by locally very thick (>2000 m) evaporites. Based on systematic analysis of reflection seismic data and isopach maps, we interpret two large-scale subsurface features (Optasi- Peris uplift and North Bulgarian arch) as Middle Triassic rift flanks associat-ed with two aborted, E-trending branches of the Paleotethys Basin. The striking appearance of the crystalline basement and the deeper levels of the Paleozoic succession (Cambrian-Silurian systems) in the subcrop of the over-lying Jurassic can be understood in terms of rapid uplift and severe denuda-tion of the rift shoulders. The extensional period was replaced during the Norian-Rhaetian times by a compressional regime in the whole Moesian Platform. Although these Late Triassic Cimmerian folds were undoubtedly formed due to compression, detailed structural analysis permitted a more specific interpretation of the deformation in terms of fault-bend folding in a north-vergent, thin-skinned thrust-fold belt. Structural modeling of the anticlines suggests relatively minor shortening (9-18%). Whereas these structures are very characteristic for North Bulgaria, their structural significance is gradually diminishing to the north, in the Romanian part of the platform. In a wider paleotectonic sce-nario, the north-vergent anticlines beneath the Moesian Platform are inter-preted as the frontal, foreland thrust-fold belt of the Mediterranean Cimmerides propagating into the foreland. Above the Cimmerian unconformity, the sedimentary facies and thickness relations of Lower to Middle Jurassic carbonates clearly show the develop-ment of a south-facing passive margin. East-west-trending Jurassic troughs bounded by normal faults can be documented in the southern, Bulgarian side of the Moesian Platform. From the Early Cretaceous on, sedimentation was clearly influenced by successive compressional periods in the Balkans approaching the southern edge of the Moesian Platform. These consecutive Cretaceous through Eocene Alpine compressive periods, such as the Austrian, Mediterranean, Laramian, Illyrian, and Pyrenean, created the north-vergent thrust-fold belt of the Balkans separated from the platform sequence by a series of relatively narrow foredeeps. Whereas the final docking of the Balkans on the Moesian Platform margin occurred at the end of the Eocene, this did not happen on the northern edge until the late Miocene, when the Carpathians stopped moving onto the platform.

This paper for the first time presents a detailed comparison between simulated and observed global electron density responses to different atmospheric tides forced from below. The recently developed Earth's whole atmospheric model from the troposphere to the ionosphere, called GAIA, has been used for the simulation of the electron density tidal responses. They have been compared with the extracted from the COSMIC electron density data tidal responses for the period of time October 2007 to March 2009. Particular attention has been paid to the nonmigrating DE3/DE2 and migrating DW1, SW2 and TW3 electron density responses. The GAIA model reproduced quite well the COSMIC DE3/DE2 responses. Both simulations and observations revealed three altitude regions of enhanced electron density responses: (1) an upper level response, above 300 km height, apparently shaped mainly by the “fountain effect”; (2) a response located near altitudes of ∼200–270 km, and (3) a lower thermospheric response situated near 120–150 km height. A possible mechanism is suggested for explaining the two lower level responses. For the first time the GAIA model simulations supported the observational evidence found in the COSMIC measurements that the ionospheric WN4 (WN3) longitude structure is not generated only by the DE3 (DE2) tide as it has been often assumed. As regards the comparison of the migrating DW1, SW2 and TW3 responses the obtained results clearly demonstrate that the GAIA model reproduce very well of the SW2 and TW3 COSMIC electron density responses. The only main discrepancy is seen in the migrating DW1 response; the observation does not support the splitting of the simulated response at both sides of the equator. This is due mainly to the difference between the SABER and GAIA SW2 tide in the lower thermosphere as it turned out that the DW1 electron density response strongly depends on the mean features of the lower thermospheric SW2 tide.

Abstract The EUREF Permanent Network Densification is a collaborative effort of 26 European GNSS analysis centers providing series of daily or weekly station position estimates of dense national and regional GNSS networks, in order to combine them into one homogenized set of station positions and velocities. During the combination, the station meta-data, including station names, DOMES numbers, and position offset definitions were carefully homogenized, position outliers were efficiently eliminated, and the results were cross-checked for any remaining inconsistencies. The results cover the period from March 1999 to January 2017 (GPS week 1000-1933) and include 31 networks with positions and velocities for 3192 stations, well covering Europe. The positions and velocities are expressed in ITRF2014 and ETRF2014 reference frames based on the Minimum Constraint approach using a selected set of ITRF2014 reference stations. The position alignment with the ITRF2014 is at the level of 1.5, 1.2, and 3.2 mm RMS for the East, North, Up components, respectively, while the velocity RMS values are 0.17, 0.14, and 0.38 mm/year for the East, North, and Up components, respectively. The high quality of the combined solution is also reflected by the 1.1, 1.1, and 3.5 mm weighted RMS values for the East, North, and Up components, respectively.

Settled indoor and outdoor dusts in urban environment represent an important source of secondary pollution. Magnetic characteristics of the settled dust from six cities in Bulgaria are explored, allowing comparison on a national (country) scale. Monthly variations of the mass‐specific magnetic susceptibilities ( χ indoor ) and ( χ outdoor ) and calculated dust loading rates for a period of 17 months do not show seasonal variability, probably due to the dominant role of traffic‐related emissions and soil‐derived particles in the settled dust. The main magnetic mineral is magnetite, present as spherules and irregular particles of pseudo‐single‐domain grain sizes. Systematically lower remanence coercivities are obtained for outdoor dusts when compared with the corresponding indoor samples, implying that penetration of smaller particles of ambient origin indoors is the main source of the indoor dust. Mean yearly values of the ratio ( χ indoor / χ outdoor ) for each city show statistically significant correlation with mortality due to cardiovascular diseases. This ratio reveals the source‐ and site‐specific importance of the anthropogenically derived toxicogenic fraction. Heavy metal content of the settled dust is related to the contribution from several pollution sources (soil‐derived, combustion and industrial), discriminated through analysis of principal components. SEM/EDX analyses reveal abundant presence of anthopogenic Fe‐containing spherules, irregular particles and diesel exhaust conglomerates. High molecular weight polyaromatic hydrocarbons (PAH) dominate the total PAH content of the outdoor dust samples. The observed linear correlation between total PAH content, coercivity of remanence and the ratio M rs / χ suggest either adsorption of PAHs on iron oxide particles and especially magnetite, or emission related increase in total PAH concentration along with a decrease of effective magnetic grain size of the accompanying magnetic fraction.

Abstract The identification of epsilon iron oxide (ɛ‐Fe 2 O 3 ) as the low Curie temperature high coercivity stable phase (HCSLT) carrying the remanence in heated archeological samples has been achieved in samples from two archeological sites that exhibited the clearest evidence of the presence of the HCSLT. This uncommon iron oxide has been detected by Confocal Raman Spectroscopy (CRS) and characterized by rock magnetic measurements. Large numbers of ɛ‐Fe 2 O 3 microaggregates (in CO) or isolated clusters (in HEL) could be recognized, distributed over the whole sample, and embedded within the ceramic matrix, along with hematite and pseudobrookite and with minor amounts of anatase, rutile, and maghemite. Curie temperature estimates of around 170°C for CO and 190°C for HEL are lower than for pure, synthetic ɛ‐Fe 2 O 3 (227°C). This, together with structural differences between the Raman spectra of the archeologically derived and synthetic samples, is likely due to Ti substitution in the ɛ‐Fe 2 O 3 crystal lattice. The γ‐Fe 2 O 3 ‐ɛ‐Fe 2 O 3 ‐α‐Fe 2 O 3 transformation series has been recognized in heated archeological samples, which may have implications in terms of their thermal history and in the factors that govern the formation of ɛ‐Fe 2 O 3 .

This paper analyses and compares a set of case studies on ecosystem services (ES) mapping and assessment with the purpose of formulating lessons learned and recommendations. Fourteen case studies were selected during the EU Horizon 2020 “Coordination and Support Action” ESMERALDA to represent different policy- and decision-making processes throughout the European Union, across a wide range of themes, biomes and scales. The analysis is based on a framework that addresses the key steps of an ES mapping and assessment process, namely policy questions, stakeholder identification and involvement, application of mapping and assessment methods, dissemination and communication and implementation. The analysis revealed that most case studies were policy-orientated or gave explicit suggestions for policy implementation in different contexts, including urban, rural and natural areas. Amongst the findings, the importance of starting stakeholder engagement early in the process was confirmed in order to generate interest and confidence in the project and to increase their willingness to cooperate. Concerning mapping and assessment methods, it was found that the integration of methods and results is essential for providing a comprehensive overview from different perspectives (e.g. social, economic). Finally, lessons learned for effective implementation of ES mapping and assessment results are presented and discussed. Graphical Abstarcat in Fig. 1.

Abstract. The global character of the millennial-scale climate variability associated with the Dansgaard–Oeschger (DO) events in Greenland has been well-established for the last glacial cycle. Mainly due to the sparsity of reliable data, however, the spatial coherence of corresponding variability during the penultimate cycle is less clear. New investigations of European loess records from Marine Isotope Stage (MIS) 6 reveal the occurrence of alternating loess intervals and paleosols (incipient soil horizons), similar to those from the last climatic cycle. These paleosols are correlated, based on their stratigraphical position and numbers as well as available optically stimulated luminescence (OSL) dates, with interstadials described in various Northern Hemisphere records and in GLt_syn, the synthetic 800 kyr record of Greenland ice core δ18O. Therefore, referring to the interstadials described in the record of the last climate cycle in European loess sequences, the four MIS 6 interstadials can confidently be interpreted as DO-like events of the penultimate climate cycle. Six more interstadials are identified from proxy measurements performed on the same interval, leading to a total of 10 interstadials with a DO-like event status. The statistical similarity between the millennial-scale loess–paleosol oscillations during the last and penultimate climate cycle provides direct empirical evidence that the cycles of the penultimate cycle are indeed of the same nature as the DO cycles originally discovered for the last glacial cycle. Our results thus imply that their underlying cause and global imprint were characteristic of at least the last two climate cycles.

Natural Capital Accounting (NCA) has evolved rapidly in recent years through substantial efforts of both international organizations and the scientific community. Water regulation ecosystem services (ES) are key elements of regulating services in ecosystem accounting, with most relevant studies strongly relying on models for ES quantification up to now. In this paper, we provide a review of modeling efforts for water regulation ES based on 148 scientific papers, properly systematized, analyzed and interpreted by using a detailed and structured original template. We examined emerging trends and gaps in model applications and the readiness to integrate them into the NCA and SEEA-EA frameworks. We propose a classification scheme which organizes the 92 different models and modeling approaches identified in the review process into eight model categories so that this scheme can be efficiently used in the water ES assessment of and for further integration into the accounting framework. Among the models, the hydrologic model SWAT and the modeling tool InVEST are by far the most popular. The results of the review revealed differences between the general ES literature and the accounting-related papers. Moreover, our analysis sets the basis for useful recommendations of which model categories are the most appropriate for the water regulation ES, included in the SEEA-EA reference list. Based on the number of relevant papers, the reliability and the confidence level of the recommendations for the use of models have been incorporated in our analysis. We highlight as model category with the highest confidence the ones relative to quantification water flow and flood control service aiming at ES accounting. Models for erosion control ES can only be recommended with a lower confidence, while for water purification the results lack clear evidence for using a particular group of models. Based on the research findings we identified the main research priorities on model integration in the accounting of water regulation ES: 1) further development of guidelines for the use of models in ecosystem accounting; 2) analyses of the spatial aspects of the model towards a clear distinction between ecosystem service supply and use; and 3) development of integrated modeling approaches for water regulation ES accounting.

Urban green space forms an integral part of urban ecosystems. Quantifying urban green space is of substantial importance for urban planning and development. Considering the drawbacks of previous urban green space index models, which established either through a grid method or green distribution, and the difficulty of the validation process of earlier urban green space index models, this study exploits the advantages of multisource high-resolution remote sensing data to establish a Building Neighborhood Green Index (BNGI) model. The model which analyzes the spatial configuration of built-up areas and the vegetation is based on the building-oriented method and considers four parameters – Green Index (GI), proximity to green, building sparsity, and building height. Comparing BNGI with GI in different types of characteristic building regions, it was found that BNGI evaluates urban green space more sensitively. It was also found that high-rise low-sparsity area has a lower mean value of BNGI (0.56) as compared with that of low-rise low-sparsity neighborhood (0.62), whereas mean GI (0.24) is equal for both neighborhoods. Taking characteristics of urban building and green types into consideration, BNGI model can be effectively used in many fields such as land suitability analysis and urban planning.

Abstract A global total electron content (TEC) model response to geomagnetic activity described by the K p index is built by using the Center for Orbit Determination of Europe (CODE) TEC data for a full 13 years, January 1999 to December 2011. The model describes the most probable spatial distribution and temporal variability of the geomagnetically forced TEC anomalies assuming that these anomalies at a given modified dip latitude depend mainly on the K p index, local time (LT), and longitude. The geomagnetic anomalies are expressed by the relative deviation of TEC from its 15 day median and are denoted as rTEC. The rTEC response to the geomagnetic activity is presented by a sum of two responses with different time delay constants and different signs of the cross‐correlation function. It has been found that the mean dependence of rTEC on K p index can be expressed by a cubic function. The LT dependence of rTEC is described by Fourier time series which includes the contribution of four diurnal components with periods 24, 12, 8, and 6 h. The rTEC dependence on longitude is presented by Fourier series which includes the contribution of zonal waves with zonal wave numbers up to 6. In order to demonstrate how the model is able to reproduce the rTEC response to geomagnetic activity, three geomagnetic storms at different seasons and solar activity conditions are presented. The model residuals clearly reveal two types of the model deviation from the data: some underestimation of the largest TEC response to the geomagnetic activity and randomly distributed errors which are the data noise or anomalies generated by other sources. The presented TEC model fits to the CODE TEC input data with small negative bias of −0.204, root mean squares error RMSE = 4.592, and standard deviation error STDE = 4.588. The model offers TEC maps which depend on geographic coordinates (5° × 5° in latitude and longitude) and universal time (UT) at given geomagnetic activity and day of the year. It could be used for both science and possible service (nowcasting and short‐term prediction); for the latter, a detailed validation of the model at different geophysical conditions has to be performed in order to clarify the model predicting quality.

Floodplain soils are frequently contaminated with metal(loid)s due to present or historic mining, but data on the bioaccessibility (BA) of contaminants in these periodically flooded soils are scarce. Therefore, we studied the speciation of As and Fe in eight As-contaminated circumneutral floodplain soils (≤ 21600 mg As/kg) and their size fractions using X-ray absorption spectroscopy (XAS) and examined the BA of As in the solids by in-vitro gastrointestinal (IVG) extractions. Arsenopyrite and As(V)-adsorbed ferrihydrite were identified by XAS as the predominant As species. The latter was the major source for bioaccessible As, which accounted for 5-35% of the total As. The amount of bioaccessible As increased with decreasing particle size and was controlled by the slow dissolution kinetics of ferrihydrite in the gastric environment (pH 1.8). The relative BA of As (% of total) decreased with decreasing particle size only in a highly As-contaminated soil--which supported by Fe XAS--suggests the formation of As-rich hydrous ferric oxides in the gastric extracts. Multiple linear regression analyses identified Al, total As, C(org), and P as main predictors for the absolute BA of As (adjusted R(2) ≤ 0.977). Health risk assessments for residential adults showed that (i) nearly half of the bulk soils may cause adverse health effects and (ii) particles <5 μm pose the highest absolute health threat upon incidental soil ingestion. Owing to their low abundance, however, health risks were primarily associated with particles in the 5-50 and 100-200 μm size ranges. These particles are easily mobilized from riverbanks during flooding events and dispersed within the floodplain or transported downstream.