Natural Geochemical Background Research Articles

Locational and Seasonal Bioaccumulation of Heavy Metals in Bivalves Sinanodonta woodiana and Unio tigridis from the Al-massab alam River, Thi-qar province

The aim of this research was to measure and compare the contents of three elements (chromium, uranium, and aluminum) in water, sediments, and oysters (Unio tigridis and Sinanodonta woodiana) from three stations in different seasons. The results showed that the concentration of these elements varied widely while exhibiting some trends and patterns. Chromium had very low concentration in water as well as oysters yet there was an increase in sediments during winter until autumn. Uranium had low concentrations in water plus oysters however its concentration increased significantly during summer including autumn season in water as well as sediments. Aluminum exhibited wide variations among stations and seasons with no clear trend or pattern both in water, sediments and oysters. Several factors might have caused variations of these elements such as; natural geochemical background, anthropogenic activities, hydrological conditions, biological processes and analytical methods used. It is therefore necessary to conduct more research on these variations so that their causes could be identified as well as their effects while assessing the potential ecologic impacts plus human health risks within the study area.

Biogeochemical researches of trace elements content in vegetation of Tatarstan

The paper presents the review of the results of studies of trace elements contents in wild plants in the Middle Volga conditions (in the example of the Republic of Tatarstan) based on literature data and data obtained by the authors. The natural range of natural concentrations has been determined. A comparison of the concentrations of microelements obtained by different authors made it possible to establish that the microelements contents in herbaceous plants of the Republic of Tatarstan does not exceed the world average clarke. The content of Cu and Zn tends to the lower limit. The identified tendency for the trace elments accumulation in plants allows to conclude about a relatively favorable biogeochemical situation in the republic as a whole. Individual local biogeochemical specializations of plants are determined by the natural geochemical background of the region.

Bottom Sediments as an Indicator of the Geoecological State of Natural Water Currents

The parameters of the natural geochemical background of ecosystems of the Lunnoye deposit area were studied and the geoecological conditions of large and small watercourses of the Yukhukhta — Yukungra interfluve were assessed according to the state of the total pollution index of bottom sediments. 27 elements of the gross content were determined by the method of emission spectral analysis. The elements that determine the geochemical specificity of the territory were revealed: Bi, Li, Sn, Y, Be, Sc, K, Th, Cs and Ra. At the time of research, the state of the surface watercourses of the territory is assessed as moderately polluted. With further monitoring, special attention should be paid to the state of the river basin Yukhukhta and especially the dynamics of changes in the chemical composition of bottom sediments of the brook. Lunny and Mramorny. The elements K, Th, Cs, Ra, Be, Zn, Pb, As, Cr, and Ni are proposed as parameters for monitoring the geoecological state of bottom sediments.

Mercury in soils of intermountain depressions in the Western Baikal region

The article presents original data on the gross concentration of Hg in soils of various types in the territory of the southwestern Baikal region. Quantitative estimates of Hg distribution over the area of intermountain depressions and slopes of mountain ranges have been obtained. The features of the distribution of Hg concentrations in the surface component of soils depending on the type of soils, granulometric composition, hydrolytic acidity, the sum of exchangeable bases, the degree of saturation with bases, pH, humus, CO, N, and humic acids were revealed. The forms of Hg occurrence in soils of different types are determined: the largest proportion of Hg is in the forms associated with organic complexes and exchangeable bases. The calculated indicators indicate an increased natural geochemical background of mercury in soils, which is associated with the territorial belonging to the Baikal rift zone.

Mercury in Soils and Air in Areas with Anthropogenic Dispersion Halos and High Natural Geochemical Background

A monitoring study of Hg distribution in soils and air (pedogenic and atmospheric) in residential settlements and surrounding areas with high natural geochemical Hg background and/or affected by man-caused impacts due to mining activities has been performed. Sites of the AltaiSayan mercury province have been studied: part of the Kurai mercury zone (Aktash settlement, Kurai campo, Chazan-Uzun settlement, Altai Republic) and part of the Ursk ore field (Ursk settlement and Ursk tailing dump, Kemerovo region). The third site is located in Kuznetsk Alatau (part of the Saralinsky gold ore cluster, settlement of Priiskovy and its tailing dump, the settlement of Ordzhonikidzevsky, Republic of Khakassia). Hg background concentrations in air and soils have been detected.

Development and implementation of a multi-criteria aggregation operator to estimate the contributions of the natural geochemical background and anthropogenic inputs in groundwater in former mining regions: An application to arsenic and antimony in the Gardon river watershed (southern France)

Establishing the contribution of natural enrichment of a substance and anthropogenic inputs has become a major issue for the management of groundwater systems. The issue is made more complex when the geology of the concerned territories is heterogeneous, at variable geographical scales, at a site that has experienced mining activity that has left behind mining remains. Several studies have tried to answer this problem using different approaches: statistical, geostatistical, geological, and geochemical. The limits of these studies are seen through the incomplete integration of geological and geomorphological parameters in the results. The aim of the present research is, therefore, to look deeper into an approach to estimate the respective contributions of the natural geochemical background and anthropogenic inputs, by simultaneously considering the heterogeneity of the geology, the variability of the spatial scale, and the combination of geological, geomorphological and statistical factors. A multi-criteria aggregation operator was thus developed and implemented on underground water bodies delimited by the Gardon watershed in the Cevennes (a region with former mining activities — France), in order to produce quantitative and qualitative maps for discriminating between the natural geochemical background and anthropogenic inputs. 176 geochemical observation points on groundwater quality were collected by sampling and through the acquisition of public data on water sources (ADES database), wells and boreholes, to reconstruct the spatial distribution of arsenic and antimony in the study site. An aggregation operator was developed, which enabled the determination of the formulae to calculate the natural geochemical background and hence deduce the anthropogenic contributions. Cartography of the quantitative and qualitative aspects of the geochemical concentrations that have been impacted by anthropogenic activity made it possible to determine remarkable focal points located on the Cevennes fault and other specific points of geochemical interest.

Možnosti hodnocení zatížení říčních sedimentů stopovými prvky na příkladu řeky Svratky a jejích přítoků

Most methods of evaluating river system contamination use an enrichment factor, but there is no consensus concerning the specific values of the natural geochemical background to be. This is critical for evaluation of the anthropogenic loading. Taking into account that the final evaluation is strongly dependent on the choice of this parameter, the aim of the paper is to show the importance of the choice of the natural background in assessing the pollution degree of river sediments. Element concentrations of the surrounding rocks are considered to be the natural geochemical background. The Svratka River springs in the Žárské vrchy Highlands. It flows through crystalline rocks in upstream, and further then through metamorphic volcanic rocks, sediments of the Boskovice furrow and plutonic rocks of the Brno Massif. Further on, it flows through a straight watercourse over the plain of the Dyje-Svratka deep valley, and the downstream flows through Miocene sediments of the Carpathian foredeep and flysch units of the Western Carpathians (Fig. 1). 24 samples of river sediments were taken from the Svratka River and its tributaries (Fig. 1). The samples were decomposed in a solution of 1 ml HF (40%) and 3 ml HNO3 (65%). The Al, Ti and As contents were determined by AAS, the Pb, Zr contents were determined by FAAS, and Cr and Ni element contents were determined by ICP-MS (Table 2). The Enrichment Factor (EF) was calculated for each sample using Al, Ti and Zr as reference elements and recommended concentration of the natural background values in Table 1. The resulting EF values are very different (Fig. 2a, b). The results of the statistical processing for lead, arsenic, nickel and chromium (Fig. 3a–d) using the reference elements titanium, aluminium and zirconium demonstrated that the choice of the reference element is not the main factor that significantly influences the final evaluation. The choice of the appropriate natural geochemical background value is absolutely crucial for the evaluation of the anthropogenic loading

Baseline Concentrations of 11 Elements as a Function of Land uses in Surface Soils of the Katangese Copperbelt Area (D.R. Congo)

The Katangese Copperbelt Area (KCA) located south-eastern of D.R. Congo presents high concentration of Metal Trace Elements (MTE) due to a rich natural geochemical background and intense mining activities. However, the lack of data on specific baseline concentrations makes it difficult to assess and monitor the environmental quality of soils in the region. In this study, 11 MTE were measured across three land uses (croplands, forest and mining areas) to assess their baseline concentrations in topsoils of the KCA. Results showed the following (geometric) mean concentrations (mg.kg-1) in cropland soils: Al (54.6), Co (0.5), Cr (0.1), Cu (3.7), Fe (33.0), Mn (44.8), Ni (0.2), Pb (0.6), Zn (1.0), Ti (2.4), pH (5.3); in forests: Al (148.0), Cd (0.1), Co (1.9), Cr (2.2), Cu (12.3), Fe (156.4), Mn (86.9), Ni (1.1), Pb (1.9), Zn (3.7), Ti (0.4), pH (4.3); and in mining areas: Al (42.8), Cd (1.3), Co (7.0), Cr (0.1), Cu (115.5), Fe (53.3), Mn (26.1), Ni (0.5), Pb (8.2), Zn (93.1), Ti (0.3), pH (5.8). Cu and Zn were higher in mining areas compared to other land uses, demonstrating a prevalent influence of mining activities in altering the natural background of metals concentrations in the region. By contrast, croplands and forest shared a similar trend of Al and Mn contents, suggesting a mild influence of agricultural activity. This study is the first attempt to establish reference values of MTE contents in the KCA soils and thus provides valuable information for legislative purposes and for soil quality assessment.

Morphobiological Response of Different Genotypes of Pinus sylvestris to the Influence of Iron and Copper Nanoparticles

The article presents the results of studying the effect of Cu and Fe nanoparticles on the development of Scots pine seedlings of two genotypically different populations growing in different geobotanical, soil-geological conditions in Orenburg oblast. It was found that the morphobiological reaction of seedlings to the effect of Cu and Fe nanoparticles, regardless of the origin of the seed material, is unidirectional in seedlings obtained from pines adapted to an increased natural geochemical background for Cu and Fe (population of the Kvarkensky district), and in seedlings obtained from seeds collected from pine trees growing in a lower geochemical background conditions (population of Buzuluk region). The presence of Cu nanoparticles had a toxic effect on the growth of pine seedlings while Fe had a stimulating one. However, the morphometric parameters of the seedlings obtained from the seeds collected in the population of the Kvarkensky district significantly differed from the seedlings of the Buzuluk district. In the presence of Cu nanoparticles in the medium, the first group of seedlings exceeded the second in main root length by 2.1–4.9%; in the number of adventitious roots, by up to 10.2%; and in the length of adventitious roots, by 0.84–7.61%. In the presence of Fe nanoforms in the medium, the first group of seedlings also exceeded the second in main root length by 0.39–2.23%; in the number of adventitious roots, by up to 3.1%; and in the length of adventitious roots, by 0.55–1.04%.

A grain-size correction for metal pollution indexes in river sediments

According to the List of Hazardous Substances of the Agency of the Toxic Substances and Disease Registry (ATSDR 2017), some metallic elements such as Pb or Cd are still considered as the most polluting elements in the world. These elements accumulate in sediments, and there are various methods available that differentiate lithogenic sources from anthropogenic sources. For that, the natural geochemical background is required, however, its definition is far from unanimous: it can be a global or local value, single or statistically estimated value, depending on the studies. Our study is focused on the Subaé River in the state of Bahia, Northeastern Brazil, which was historically contaminated by lead metallurgy. The river sediments were sampled at 21 locations: one at the discharge point of the plant's rainwater basin, ten upstream, and ten downstream. The total contents of Fe, Ti, Mn, Pb, Zn, Cu, Cr, particle-size distribution, and organic matter were analyzed. The conventional geochemical indexes, i.e., the pollution degree (mCd), pollution load index, and enrichment factor indicated contamination by Zn, Pb, Cr, and Cu. Then, a new enrichment factor is introduced, assuming that the sediments come from erosion of soils in the watershed. After obtaining the natural concentrations of metals in the clay, silt, and sand fractions of uncontaminated reference soils, we corrected the pollution indexes by calculating a new individual background in each sediment sample, according to its grain size distribution. This new approach provided more precise indexes in the assessment of sediment pollution, by highlighting higher contamination of Zn and Pb (around 50%) and at the same time the absence of Cr and Cu contamination, two metals not involved with the metallurgical activity.

Ecological analysis of agricultural environmental management problems in the Central Chernozem Region

Abstract. Land resources of the Central Chernozem Region are intensively used in economic activities that have affected the degradation of the natural environment components. The 100-year observation period revealed changes in biogenic components and humus in the regions soils. To determine the environmental problems of agricultural environmental management, we have calculated modular indicators of geochemical impact of various agricultural sectors. We have calculated the modular indicator of agricultural impact assessment on agricultural systems of the Central Chernozem Region. In order to preserve land resources it is important to quantify the impact of agricultural production. To assess the impact the authors have introduced three types of coefficients: taking into account the agricultural, livestock and technogenic impact. They can be used as the main diagnostic indicators to identify environmental problems. The coefficients make it possible to determine trends in environmental management and by the results of geochemical analysis environmental problems and the degree of impact of different types of agricultural production are identified. Balance violations of the substances cycle in forest-steppe landscapes have been revealed. The landscape and geochemical approach reveals migration processes, the cycle of substance and violations of self-regulating properties of the natural landscape. The analysis of potassium and phosphorus distribution is important in agrochemical aspect. The coefficient was calculated based on the mass of matter introduced and removed from the soil in relation to their content in the soil. The degree of geochemical agricultural impact exceeds the natural geochemical background. It gives an opportunity to define negative features of agricultural nature use. A complex geochemical analysis of different nature users will make it possible to determine the degree of their impact on the natural environment in the region. Soil transformation in agrosystems is accompanied by ecological losses both for the natural environment and for life activity of the population. Due to wide application of chemicalization means for implementation of the agricultural intensification program, it became necessary to determine quantitatively the geochemical load on the landscape in order to optimize and protect it. In this regard, issues of renewal of natural material and energy resources are relevant for agricultural production.

Assessment of anthropogenic load and ecosystem stability in the land cadastre zoning of megacities

With the increasing number of megacities, the constant expansion of their borders, and the often chaotic, unreasonable land-use planning, even those sites with potential recreational use suffer from enormous anthropogenic pressure. Defining the limits of ecosystem stability is one of the most important scientific research, which allows setting permissible anthropogenic impact in the land cadastre zoning of megacities. This investigation presents the integral assessment of net anthropogenic load on the environment and boundaries of the natural soil geochemical background change.

Nature management on the Arctic territories of the Russian Far East

The established structure of environmental management, which depends on economic activities, determines the ecological situation of a particular territory. Such studies are particularly important and relevant for areas with low ecological capacity and resistance, which include the territory of the Arctic zone of the Russian Far East (RFE). The discussed territories have a high vulnerability of the natural environment to anthropogenic impacts and a low recovery rate of the disturbed state. Analysis of information on the environmental state of the Chukotka Autonomous Region and the Republic of Sakha (Yakutia) allows us to conclude that the environmental situation is unfavorable in the regions. The established system of environmental management in certain areas of the Russian Arctic has led to the emergence of heavily modified areas as a result of economic activity, where the disturbing dynamic equilibrium of the natural environment has led to changes in the natural geochemical background, depletion of biodiversity, degradation of soil and vegetation, development of erosion processes, and environmental pollution. The paper presents the socio-economic, natural-geographical, ecological characteristics of the Arctic zone of the RFE in the context of ulus, proposed the structure of existing and possible future directions of environmental management.

Mercury isotopes in frozen soils reveal transboundary atmospheric mercury deposition over the Himalayas and Tibetan Plateau

The concentration and isotopic composition of mercury (Hg) were studied in frozen soils along a southwest-northeast transect over the Himalaya-Tibet. Soil total Hg (HgT) concentrations were significantly higher in the southern slopes (72 ± 54 ng g−1, 2SD, n = 21) than those in the northern slopes (43 ± 26 ng g−1, 2SD, n = 10) of Himalaya-Tibet. No significant relationship was observed between HgT concentrations and soil organic carbon (SOC), indicating that the HgT variation was not governed by SOC. Soil from the southern slopes showed significantly negative mean δ202Hg (−0.53 ± 0.50‰, 2SD, n = 21) relative to those from the northern slopes (−0.12 ± 0.40‰, 2SD, n = 10). The δ202Hg values of the southern slopes are more similar to South Asian anthropogenic Hg emissions. A significant correlation between 1/HgT and δ202Hg was observed in all the soil samples, further suggesting a mixing of Hg from South Asian anthropogenic emissions and natural geochemical background. Large ranges of Δ199Hg (−0.45 and 0.24‰) were observed in frozen soils. Most of soil samples displayed negative Δ199Hg values, implying they mainly received Hg from gaseous Hg(0) deposition. A few samples had slightly positive odd-MIF, indicating precipitation-sourced Hg was more prevalent than gaseous Hg(0) in certain areas. The spatial distribution patterns of HgT concentrations and Hg isotopes indicated that Himalaya-Tibet, even its northern part, may have been influenced by transboundary atmospheric Hg pollution from South Asia.

The Effect of Natural Geochemical Background on Neurological and Mental Health

The natural geochemical (geogenic) background is exerted through the local drinking water, food grown on the local soils and the atmospheric aerosols inhaled. The misbalance of certain elements, in the most acute case, may lead to the development of so-called ‘endemic’ symptoms and diseases. Compared to anthropogenic contamination, the effect of the geogenic background may have an implicit character due to its not extreme, chronic and pervading action. Moreover, the brain must be viewed somewhat separately to the other body organs from the toxicological point of view because of the specific protective blood–brain (hematoencephalic) barrier. Nowhere is homeostasis and the control of the constant of internal milieu more pronounced than in the brain. However, certain metal compounds, presumably of lipophilic character, can overcome the natural defence and are especially dangerous to the nervous system. The neurologically detrimental geogenic excess was determined and assumed for Al, As, Ba, Cd, Fe, Hg, Mn, Pb, Se, Tl and Zn. Moreover, deficiency of certain elements can cause disturbances to the brain functioning. These elements are Cu, Fe, I, Li and Se. There are also elements for which small-dose neurological effects were described and the natural geochemical anomalies have been reported. These are B, Br, Rb, Sn and, possibly, others. Nevertheless, the information on their chronic environmental neurological activity is still a matter of future studies. In this review, we focus on the geogenic background as a cause of neurological and mental effects on human health.

MODERN CONTAMINATION OF BOTTOM SEDIMENTS AND ECOLOGICAL STATE OF MACROZOOBENTHOS IN THE COASTAL ZONE AT VLADIVOSTOK (PETER THE GREAT BAY, JAPAN SEA)

Contamination of bottom sediments in Peter the Great Bay is spatially variable, but for majority of stations it exceeds the natural geochemical background and «safe» level with at least one pollutant, mainly with hydrocarbons, pesticides, cadmium and mercury. The main sources of contaminants are the waste discharge of Vladivostok and other cities (oil products, pesticides, phenols, heavy metals: Cd, Cu, Hg, Pb, Zn) and rivers fall into the northern parts of Amur and Ussuri Bays (Co, Mn, Ni, Fe). The Golden Horn Bay and the Bosphorus East Strait are the most polluted areas, where concentrations of both heavy metals and hydrocarbons exceed the natural background and «safe» level considerably. The Amur Bay has moderate contamination, and the Ussuri Bay is contaminated slightly. Recently the chemical contamination and eutrophication are the main factors that determine the ecological status of bottom populations, though the former one is valid locally, in the most contaminated areas only.

Comparative Analysis of Copper and Cadmium Accumulation by Macrophytes of the Chupa Inlet, Kandalaksha Bay, White Sea

The content of dry matter, copper (Cu), and cadmium (Cd) have been studied in five species of brown algae and one species of higher plants at six sampling sites in the Chupa Inlet of the Kandalaksha Bay of the White Sea. Despite a common natural geochemical background, a variability in the content of Cu and Cd has been observed in algae species which have similar systematic positions. No simple functional relationship could be established between the dry matter content and content of metals. Copper affects the accumulation of cadmium only when the Cu content is high. Species of the family Fucaceae (Fucus vesiculosus, F. serratus, and Pelvetiacanaliculata) accumulated Cu and Cd most effectively. The minimum content of Cd was found in the leaves of Triglochinmaritimum.

An emerging market for groundwater remediation in China: Policies, statistics, and future outlook

There is a rapidly emerging and potentially huge market for the remediation of contaminated groundwater in China. The Chinese government published a Water Action Plan in April 2015, a Soil Action Plan in May 2016, and a draft Soil Pollution Prevention and Control Law in June 2017. All of these new policies and regulations put pressures on local governments and contaminated site owners, obliging them to conduct site investigation and to cleanup contaminated groundwater. The Chinese population in northern regions heavily depend on groundwater, with nearly 70% of water supply coming from aquifer sources in the Beijing-Tianjin-Hebei region. However, poor groundwater quality due to natural geochemical background and anthropogeic pollution is a serious concern, with poor or very poor quality water observed in nearly 80% of groundwater monitoring wells in 17 northern provinces. Shallow groundwater in many areas has been contaminated by toxic pollutants such as heavy metals and chlorinated organic compounds. There is an urgent need to better understand the situation and to conduct groundwater remediation at contaminated sites. The Chinese government is investing heavily in the research and development for groundwater remediation, which is expected to greatly add to the quality and quantity of groundwater remediation projects in the near future.

The paradigm of high concentration of metals of natural or anthropogenic origin in soils – The case of Neves-Corvo mine area (Southern Portugal)

The aim of this study is to evaluate the spatial distribution of arsenic, copper, lead and zinc in soils, often used for agriculture, collected in the vicinity of Neves-Corvo mine, and understand how the geological context and local and natural geochemical anomalies can be differentiated from anthropogenic loads.It was found that mean and median concentrations of arsenic observed in soils used for agriculture in the vicinity of Neves-Corvo mine, exceeded more than twice the recommended value of 11mgkg−1, in accordance with the Ontario Guidelines (OG). Furthermore, at 83% of sampling sites, arsenic in soils exceeded the above-mentioned limit. A similar situation held for copper, whose soil concentrations were above the levels recommended by the OG. In contrast, lead and zinc levels did not exceed OG-recommended levels. In addition, natural geochemical background threshold values were above (As and Cu), below (Zn) and above and/or below (Pb) the OG-recommended levels, indicating that even in the absence of anthropogenic contamination, the area in the vicinity of the mine poses a risk for agriculture.It was concluded that all the areas with the highest probability of the occurrence of concentrations above threshold values were located very close to the mine complex, mainly southeast, and were of anthropogenic origin. Spatial results deriving from probability maps were also consistent with positive Pearson's correlation coefficients.

Bioaccumulation of thallium and other trace metals in Biscutella laevigata nearby a decommissioned zinc-lead mine (Northeastern Italian Alps)

The mineral body exploited in Salafossa (Eastern Dolomites) was one of the largest lead/zinc-containing mineral deposits in Europe. Both metals were mainly present as sulphides (sphalerite, ZnS and galena, PbS). Mining activity started around 1550, but it was only around 1960 that the richest veins of the minerals were discovered. The mine closed in 1985, and concentrations of several trace metals, such as thallium (Tl), iron (Fe), manganese (Mn), lead (Pb) and zinc (Zn), were detected in the soils and plant samples (Biscutella laevigata L.) that were collected from eighteen sites selected outside the mine. B. laevigata is a pseudometallophyta species, and it often grows near mining areas where the soil's metal concentrations are significantly higher than those of soil with a natural geochemical background.The total metal concentrations in the plant tissue (roots and leaves of Biscutella laevigata) and in the soil samples – both bulk-soil and the B. laevigata root system (rhizo-soil) – were determined through Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The metal extractability and leachability of the soil samples were estimated using soil extractions with DTPA (Diethylenetriaminepentaacetic acid). In addition, metal mobility caused by rainwater runoff was estimated by using a leaching test with a dilute solution of H2SO4 and HNO3.The results showed that metals were present in a chemical form available for uptake by the plants' roots. In fact, high concentrations of the metals were also found in the plant tissue (roots and leaves) of B. laevigata, and these concentrations were higher than those whose soils present natural geochemical background levels in the corresponding rhizo-soil. Thus, B. laevigata has shown a marked ability to bioaccumulate trace metals, especially Tl and, to a lesser extent, Zn, Pb, Fe and Mn, and it can influence metal mobility in the rhizo-soil.To assess the uptake and translocation processes of the trace metals, resulting in their bioaccumulation, two different indices were calculated: the enrichment factor in roots (EFr), as the ratio between the metal concentration in belowground biomass and in the respective rhizo-soil, and the translocation factor (TF), as the ratio between the metal concentration in the leaves and the corresponding roots. For both indices, values > 1 denoted enrichment of the metal in the roots or its translocation to the upper tissues. The results showed that EFr and TF were considerably high only for Tl, reaching a maximum value of 60 for EFr and 11.6 for TF. Conversely, the other investigated metals did not show significant bioaccumulation (EFr < 1), and they showed TF > 1 only at a few sites.