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Lead contamination in soils and sediments is a major threat to water quality. In surface and near-surface environments, Pb is not redox active; however, common Pb hosts, including Fe(III)-(hydr)oxides and sulfides, dissolve and precipitate as redox conditions change. Dissolution of Pb hosts may release Pb to porewater, leading to spikes in dissolved Pb concentrations and potential transport into surface or groundwater. Here, we examine the impacts of hydrologically coupled redox transitions on Pb partitioning in contaminated floodplain soils. We find that the affinity of Pb for particulate organic matter (POM), inclusive of mineral-associated organic matter, ensures that across redox transitions Pb is retained in the solid phase, despite host-phase (Fe(III)-(hydr)oxide and sulfide) dissolution. As seasonal hydrologic dynamics shift porewater redox conditions, Pb-bearing Fe(III)-(hydr)oxides (Pb-HFO) and sulfides (PbS) are dissolved and (re)precipitated. However, despite these shifts in redox conditions and associated host-phase transformations, Pb retention on POM, coupled with the formation of PbS and Pb-HFO, maintains dissolved Pb concentrations below 17 μg L

The concentrations of 28 polychlorinated biphenyls (PCBs) were determined in soils collected at three depths from thirteen different sites along the floodplain of the lower reaches of the River Niger (LRRN) in Nigeria. The aim of the study was to provide data on the levels of contamination, sources of the contaminants, and risks to the ecosystem and humans. Soil samples were Soxhlet extracted with a solvent mixture of dichloromethane (DCM)/n-hexane and cleaned up on a column packed with Florisil and silica gel. The PCBs in the samples were quantified by gas chromatography-mass spectrometry. The Ʃ28 PCB concentrations in the floodplain soils varied between not detected (nd) and 11,151 ng g−1 for different sampling sites and depths. The PCB concentrations and homologue distribution patterns in soil profiles of the floodplain of the LRRN showed remarkable differences with respect to sites and depths. The results obtained were used to evaluate the ecological and human health risks, which indicated that there is a potential risk to organisms and humans from exposure to PCBs in these soil profiles. The source evaluation as determined by principal component analysis suggested that PCBs in these soil profiles came from burnt circuit boards, cable wires, use of paints, discharges from transformers, long-range migration, and deposition.

The pollution of floodplain, deltaic and adjacent coastal soils in large fluvial systems, considered an urgent environmental problem, as well as potentially toxic elements in such environments, can negatively affect aquatic ecosystems, as well as pose significant risks to human health. This paper is devoted to the geochemistry of potentially toxic elements in soils of the Lower Don basin, which is one of the largest and most anthropogenically transformed water bodies in Southern Russia, as well as the adjacent areas of the Taganrog Bay coast. The median element concentrations in the soils of the study area were consistent with the world soil average and the contents of elements in background soils. Comparative assessment of the spatial distributions as well as the results of Pearson’s correlations, cluster analysis and principal component analysis showed that Cr, Ni, Cu and Zn are predominantly of natural origin; Mn and As are of mixed sources; and Cd and Pb are predominantly of anthropogenic origin. The geochemical anomalies of elements were associated with the impact of local anthropogenic sources. Geochemical background values for Cr, Mn, Ni, Cu, Zn, As, Cd and Pb in the soils of the Lower Don and the Taganrog Bay coast determined using the ‘median + 2 median absolute deviations’ approach are presented. The highest values of the integrated pollution indices were observed in floodplain soils of small rivers.

The frequency and duration of flooding events are increasing due to land-use changes increasing run-off of precipitation, and climate change causing more intense rainfall events. Floodplain soils situated downstream of urban or industrial catchments, which were traditionally considered a sink of potentially toxic elements (PTEs) arriving from the river reach, may now become a source of legacy pollution to the surrounding environment if PTEs are mobilised by unprecedented flooding events.\ud \ud When a soil floods, the mobility of PTEs can increase or decrease due to the net effect of five key processes; (i) the soil redox potential decreases which can directly alter the speciation, and hence mobility, of redox sensitive PTEs (e.g. Cr, As), (ii) pH increases which usually decreases the mobility of metal cations (e.g. Cd2+, Cu2+, Ni2+, Pb2+, Zn2+), (iii) dissolved organic matter (DOM) increases, which chelates and mobilises PTEs, (iv) Fe and Mn hydroxides undergo reductive dissolution, releasing adsorbed and co-precipitated PTEs, and (v) sulphate is reduced and PTEs are immobilised due to precipitation of metal sulphides. These factors may be independent mechanisms, but they interact with one another to affect the mobility of PTEs, meaning the effect of flooding on PTE mobility is not easy to predict. Many of the processes involved in mobilising PTEs are microbially mediated, temperature dependent and the kinetics are poorly understood.\ud \ud Soil mineralogy and texture are properties that change spatially and will affect how the mobility of PTEs in a specific soil may be impacted by flooding. As a result, knowledge based on one river catchment may not be particularly useful for predicting the impacts of flooding at another site. This review provides a critical discussion of the mechanisms controlling the mobility of PTEs in floodplain soils. It summarises current understanding, identifies limitations to existing knowledge, and highlights requirements for further research.

Denitrification in floodplain soils is one key process that determines the buffering capacity of riparian zones in terms of diffuse nitrate pollution. One widely used approach to measure the denitrification potential is the acetylene inhibition technique that requires fresh soil samples. We conducted experiments with air-dried soils using a time series analysis to determine the optimal rewetting period. Thus, air-dried soil samples from six different floodplain areas in Germany were rewetted for 1 to 13days to 100% water-filled pore space. We analyzed nitrogen accumulated as N2O in the top of anaerobic flasks with and without acetylene by gas chromatography after four hours of incubation. We observed an overall optimal rewetting of at least seven days for complete denitrification. We also saw the strong influence of pH and field capacity on the denitrification product ratio, in soils with pH &lt, 7, we hardly assumed complete denitrification, whereas the treatments with pH &gt, 7 achieved stable values after seven days of rewetting. This advanced method provides the opportunity to carry out campaigns with large soil sample sizes on the landscape scale, as samples can be stored dry until measurements are taken.

The enrichment of potentially harmful elements (PHEs) in stream sediments (SS) and floodplain soils (FS) poses great environmental hazards to water bodies and other parts of the ecosystem. The aim of this research was to evaluate the distribution pattern of selected PHEs (Cu, Pb, Zn, Co, Mn, As, Cd, V, Cr, Ni, Th, Sr and La) in SS of selected rivers that drain Ile-Ife area and their adjacent FS, to ascertain the pollution status of these elements in the study area. Sixty samples (40 SS and 20 FS) were purposely collected for this study; the samples were analysed with ultra-trace inductively coupled plasma mass spectrometry method (ICP-MS). The PHEs results showed decreasing trend of average contents of PHEs studied; Mn > Zn > V > Cr > Pb > La > Sr > Cu > Ni > Co > Th > As > Cd for both SS and FS. Also, PHEs concentration in the studied geo media showed a significant level of enrichment as observed from the results. Elemental association showed positive correlation for topsoil, Pb/Zn = R2, 0.85 and negative correlation for topsoil Cr/Zn = R2 0.02 among the other PHEs. Source apportionment showed that the studied metal enrichment is largely anthropogenic rather than geogenic. Geoaccumulation and metal ratio indexes indicated that FS and SS studied have received significant PHEs of between moderately to strongly polluted, which implies significant environmental implications in the study area.

Пожалуйста, вставьте свой абстрактный HTHigh anthropogenic impact and the rate of urbanization result in a decrease of urban soils’ capacity to perform ecosystem services. Carbon sequestration is an important soil-based ecosystem service, which can be assessed through quantity and quality soil carbon stocks. The stability of soil organic matter (SOM) is characterized by the resistance of its constituent components to biological, chemical and physical destruction. In the study, SOME stability in peat-sand mixture used for urban soils’ construction; floodplain soil was analyzed in response to temperature-moisture conditions. The decomposition rate of various soils was assessed. Decomposition was assessed through studying microbial production of CO2. In the research the CO2 emissions were studied under following temperatures and moisture conditions: temperature – 7°C, 22°C, 30°C and 40°C and moisture – 0.2 WHC, 0.4 WHC, 0.6 WHC, 0.8 WHC, 1 WHC. Moisture affects the amount and activity of microbial biomass, controls the availability of oxygen to microorganisms, causes periods of water microbial stress and also can destabilize organic matter, resulting in increased availability of carbon to soil microorganisms. Different patterns of moisture and temperature impacts on the soil organic carbon (SOC) decomposition rates were observed. It was concluded that, depending on the qualitative composition of carbon, the impact of hydrothermal conditions on the emission of carbon dioxide changed.ML здесь.

The soils developed from the Ganges sediments in the coastal area of Bangladesh and India extend several thousand hectares and important from the view point of rice cultivation. Phosphorus, one of the important environmental and agricultural element, retention behavior of the Ganges floodplain soils is poorly reported. The objective of this study was to determine maximum phosphorus adsorption capacity (MPAC) and to develop Psat for 13 Ganges Tidal Floodplain soils of Bangladesh. The MPAC value and Psat based on Mehlich-3 extractions were determined. The conventional adsorption equations, such as the Langmuir, Freudlich and Temkin equations were used to describe the P sorption of the studied soils. The MPAC value varied from 1250 to 2000 mg/kg and correlated with EC (r = 0.59, p

The chemical fractionation of nine metals, Cd, Pb, Cr, Ni, Cu, Co, Ba, Mn and Zn, in soil profiles of the floodplain of the lower reaches of the River Niger in Nigeria, was investigated with a view to providing information on the forms, bioavailability and mobility of these metals in the soil profiles. The chemical forms of metals in the soil were determined by using the European Community Bureau of Reference (BCR) sequential chemical extraction method and the concentrations were measured by inductively coupled plasma-atomic emission spectrophotometry (ICP-AES). The results indicated that the residual and Fe-Mn oxide/hydroxide phases were the predominant forms of the metals in the soil profiles. The percentage of metals in the readily available and potentially available fractions followed the order: Pb > Ba > Cd > Ni > Co > Zn > Mn > Cu > Cr. Significant proportions of these metals were found in the potentially available phases, which indicate an increase in mobility and availability as a result of change...

CORRECTION: Due to a number of formatting and layout issues, the PDF of this paper was replaced on 10th October 2016. The page numbers of this article have changed from 55-61 to 57-63. The present investigation aimed to evaluate different fractions of P of Ganges tidal floodplain soils of Bangladesh in terms of plant availability in the selected soil. The samples were analyzed for solution P, labile pool, alkali-extracted inorganic pool, organic pool, acidic pool and residual P.The soil solution P in the tested soils ranged from 0.03 to 0.11 mg L –1 . The concentration of 0.5M NaHCO 3 extracted P had a range of 8-34 mg kg –1 . Dilute NaOH extracted inorganic P had a range of 25-59 mg kg –1 . NaOH extracted organic P ranged from 334 to 542 mg kg –1 and acid extracted P represented from 140 to 443 mg kg –1 , respectively. Residual P of the tested soils showed a concentration of 104-262 mg kg –1 . On average of the 12 soils, the relative concentration of solution P was 0.01%, NaHCO 3 P was 3.2%, NaOH-Pi was 6.8%, NaOH-Po was 44.6%, acid pool was 27.3% and residual fraction was 18.1%. Different P pools showed strong correlation either with sand, silt, clay, electrical conductivity, pH(H 2 O), pH (KCl), organic carbon or extractable Fe content. The tested Ganges tidal floodplain soils demonstrated wide variation in the relative proportion of different P pools. Bangladesh Rice j. 2015, 19(2): 57-63

Microplastics (MPs) are small (5 mm diameter) but have clear implications for the environment. These artificial particles are found in and pose threats to aquatic systems worldwide. MPs have terrestrial sources, but their concentrations and fates in the terrestrial environment are poorly understood. While global plastic production continues to increase, so do the environmental concentrations and impacts of MPs. In this first study of MPs in floodplain soils, we developed a method for identifying, quantifying, and measuring the sizes of most commonly produced MPs in soil by FT-IR microscopy. For small MP (1 mm) analysis, MP were separated by density separation and oxidation of organic matter. In this study we analyzed 29 floodplains in Swiss nature reserves associated with catchments covering 53% of Switzerland. We found evidence that 90% of Swiss floodplain soils contain MPs. The highest MP concentrations were associated with the concentration of mesoplastics (5 mm - 2.5 cm diameter), indicating plastic waste as source. Furthermore, MP concentration was correlated with the population of the catchment. The wide distribution of MPs, their presence in remote unsettled high mountain areas, decoupling of MEP and MP compositions, and the dominance of MPs by small (500 μm diameter) particles, indicate that MPs enter soils via diffuse aeolian transport.

Phosphorus (P) availability, which depends on both P concentration and speciation, often controls primary productivity and algal-bloom formation in river systems. The river P pool is also connected to P pools of adjacent sediments, soils and vegetation. Thus, informed management of P in floodplain–river systems requires detailed understanding of P concentration and speciation in all of these interconnected components. We studied P speciation in river sediments and water, floodplain soils and river red gum (Eucalyptus camaldulensis) leaf litter from the Lower Murray region using conventional spectroscopic measurements, solution 31P nuclear magnetic resonance (31P NMR) spectroscopy, and leaching experiments to simulate floodplain re-wetting of leaf litter. Almost all (>85%) of the P in river sediments was in the orthophosphate form, whereas floodplain soils had higher proportions of organic P (PO) species. Both fresh and senescent river red gum leaf litter also had a much higher concentration of PO, primarily in the form of phytate. On submersion, there was a rapid (0–96h) loss of dissolved P from senescent leaves; release of dissolved organic carbon showed similar kinetics. Loss of P from the leaves included both organic and inorganic forms. The results have important implications for aquatic primary productivity and environmental management strategies.

The concentrations of the USEPA 16 priority polycyclic aromatic hydrocarbons (PAHs) in soils of the floodplain of the lower reaches of River Niger, Nigeria, were investigated following the Lagdo Dam flood disaster of 2012. The aim was to provide information on the extent of contamination, sources, and risks of PAHs in these soils. The concentrations of Σ16 PAHs in the floodplain soils ranged from 812 to 10,700 μg kg. The benzo(a)pyrene (BaP) toxic equivalence and incremental lifetime cancer risk (ILCR) factors were used to evaluate the risk of human exposure to PAHs in these soils. The concentrations of benzo(a)pyrene carcinogenic equivalence (BaP) and benzo(a)pyrene mutagenic equivalence (BaP) ranged from not detected to 4090 μg kg and not detected to 4150 μg kg, respectively. The total ILCR for children and adults was calculated as the summation of the individual risks through the three routes of exposure, (ingestion, dermal, and inhalation of vapor or dust). The values obtained indicate that there are 6450 and 4480 chances in one million equally exposed persons to develop the risk of cancer for children and adults, respectively, which were higher than the USEPA acceptable guideline value of one cancer case in one million (10) equally exposed persons. The PAHs source evaluation, using the diagnostic ratios and principal component analysis (PCA), indicated that the major sources of PAHs in these soils were fossil fuel combustion, gas flaring, wood combustion, traffic emissions, and input from petroleum.

Two long-term submerged Eutric Gleysols (GLe) and two short-term flooded Eutric Fluvisols (FLe) with high organic carbon contents (Corg between 5.1 and 12.9%) were selected to characterize soil microbial communities at the Elbe River (Germany). Measurements included dehydrogenase activity (DHA), soil microbial carbon (Cmic), soil basal respiration (BR), metabolic quotient (qCO2), Cmic/Corg ratio, and phospholipid fatty acids (PLFA). PLFA biomass, DHA, and Cmic/Corg ratios were considerable lower in GLe's than in FLe's. Whereas the BR as well as qCO2 were higher in GLe's what seems to be an unspecific response of aerobic soil microorganisms to the long flooding period and the resulting short time for development following flooding. Cmic/Corg ratios were low in comparison to terrestrial soils. PLFA profiles were dominated by saturated fatty acids (FA). Principal component analyses (PCA) of FAs revealed clear differences among the four floodplain soils. In GLe's all fractions of PLFAs were lower tha...

Two long-term submerged Eutric Gleysols (GLe) and two short-time flooded Eutric Fluvisols (FLe) at the Elbe River (Germany) with high organic carbon contents (Corg between 4.9 and 11.6%) were selected to evaluate dehydrogenase activity (DHA), soil microbial carbon (Cmic), Cmic/Corg ratio, and phospholipid fatty acids (PLFA) to characterize and discriminate these soils with microbial parameters. DHA, Cmic and PLFA-biomass as well as Cmic/Corg ratios are considerable lower in GLe's than in FLe's what seem to be an unspecific response of aerobic soil microorganisms on the long flooding period and the resulting short time for development after last flooding. Cmic/Corg ratios are low in comparison to terrestrial soils. PLFA profiles were dominated by saturated fatty acids (FA). Principal component analyses (PCA) with the identified FAs revealed a clear discrimination among the four floodplain soils. In GLe's, all groups of PLFA, inclusive monounsaturated FA, are lowest and in FLe's highest. Polyunsaturated FA ...

Small concentrations of mercury are determined by the example of the quantitative recovery of a toxicant from snow water in a segregating system with no organic solvent (water-antipyrine-sulfosalicic acid). The organic component of the system in situ forming as a result of acid-base interactions was used in microliter amounts to modify a graphite indicator electrode and register an analytical signal of mercury. The reliability of the results of voltammetric determination was checked by the independent cold vapor method. Organic components obtained by segregation were used to extract mercury from the conservative ecosystem component, solid snow particles, snow water preconcentrated with a membrane filter, river suspensions from surface water and floodplain soils, and also fish samples. The characteristic features of mercury extraction with a mixture if mineral acids and the liquid organic component of a segregating system with no organic solvent are discussed.

Gleyzation-mediated leaching of radiostrontium from floodplain soils of the Krasnoyarsk Mining and Chemical Combine (MCC) activity zone [Atamanovskii Island (front part), Oseredysh Island (front part), and Berezovyi Island (rear part)] is studied with model systems. Leaching of radiostrontium from waterlogged soils is analyzed in terms of the model of anaerobic biosolubilization of gel films. The leaching of radiostrontium is found to correlate with that of iron, confirming the cosolubilization model. Addition of glucose (0.5%) as a stimulant for growth of iron-reducing microorganisms increases the dynamic coefficient of radiostrontium leaching, particularly in soils with lower organic matter content. The model experiments showed that the radiostrontium leaching rate from floodplain soil is higher by 2–3 orders of magnitude than that of radio-cesium, suggesting the possibility of escape of radiostrontium from the floodplain of the Yenisei River with the intrasoil runoff. This conclusion is supported by the experimental data on the 90Sr/137Cs ratio in the floodplain of the Yenisei River downstream of MCC (0.01–0.1).

Although the qualities of the river water and the sediments of the river Elbe have greatly improved over the past twenty years, both the suspended matter and the sediments are still contaminated with heavy metals and arsenic (HM). This contamination exceeds the action values specified in the Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV). The status of floodplain soil contamination with HM along the entire German alluvial Elbe was investigated and evaluated, based on former research activities and recently performed analyses after the extreme flood event in August 2002 and the subsequent winter flooding. The section downstream of the river Mulde inflow was contaminated much higher than the upstream section. With the installation of permanently marked observation areas a tool for soil quality monitoring has been established for the future. Die hochwasserbedingte Belastung der Auen mit Schwermetallen und Arsen entlang der Elbe Obgleich sich die Flusswasser- und Sedimentqualitat der Elbe in den letzten 20 Jahren erheblich verbessert haben, sind die Schwebstoffe und schwebstoffburtigen Sedimente immer noch hoch mit Schwermetallen belastet. Dies fuhrt bei Bodenbildungen aus diesen Substraten haufig zur Uberschreitung der in der Bundesbodenschutz- und Altlastenverordnung (BBodSchV) festgelegten Masnahmewerte. Basierend auf fruheren Untersuchungen und aktuellen Erhebungen wahrend des extremen Hochwassers vom August 2002 und des folgenden Winterhochwassers wurde der gegenwartige Belastungsstatus der Boden in den Uberflutungsgebieten entlang der gesamten deutschen tidefreien Elbe ermittelt und bewertet. Dabei war der Flussabschnitt unterhalb der Muldemundung wesentlich hoher als der oberhalb gelegene belastet. Durch die Anlage dauerhaft markierter Beobachtungsflachen wird es ermoglicht, in Zukunft Veranderungen des Stoffbestandes exakt zu erfassen.

Depth profiles of various organic micropollutants were measured in floodplain soils of the river Elbe, Germany. The study area lies in the former East Germany (GDR) and displays elevated concentrations of pesticides and polycyclic aromatic hydrocarbons. Depth distributions were found to vary at different sampling points and among the individual compounds, which could only partly be explained by comparing normalized concentrations (organic carbon). Metabolization, mobilization, and effects of sedimentation and erosion also need to be taken into account to understand the contaminant patterns found in the different profiles. Tiefenverteilung von chlorierten und polycyclischen aromatischen Kohlenwasserstoffen in Auenboden der Elbe Es wurden Tiefenverteilungen verschiedener organischer Spurenstoffe in Auenboden der Elbe bestimmt. Das Untersuchungsgebiet befindet sich am Mittellauf des Flusses und zeigt erhohte Konzentrationen an Pestiziden und polycyclischen aromatischen Kohlenwasserstoffen. Unterschiedliche Tiefenverteilungen wurden an den verschiedenen Probenahmestellen und fur die verschiedenen Verbindungen gefunden, die sich nur teilweise nach einer Normierung auf den organischen Kohlenstoffgehalt erklaren lassen. Metabolisierung, Mobilisierung sowie Sedimentations- und Erosionseffekte mussen zusatzlich berucksichtigt werden, um die unterschiedlichen Schadstoffmuster zu verstehen.

Am and Pu speciation in floodplain soils and bottom sediments of the Yenisei River is studied. Pu is more tightly associated with amorphous hydroxides as compared to Am. Am associated with organic matter is potentially more mobile than Pu. Model experiments showed that fulvic acids decelerate Am sorption from water to floodplain soil.

In floodplain soils, As may be released during flooding-induced soil anoxia, with the degree of mobilization being affected by microbial redox processes such as the reduction of As(V), Fe(III), and SO4(2-). Microbial SO4(2-) reduction may affect both Fe and As cycling, but the processes involved and their ultimate consequences on As mobility are not well understood. Here, we examine the effect of microbial SO4(2) reduction on solution dynamics and solid-phase speciation of As during flooding of an As-contaminated soil. In the absence of significant levels of microbial SO4(2-) reduction, flooding caused increased Fe(II) and As(III) concentrations over a 10 week period, which is consistent with microbial Fe(III)- and As(V)-reduction. Microbial SO4(2-) reduction leads to lower concentrations of porewater Fe(II) as a result of FeS formation. Scanning electron microscopy with energy dispersive X-ray fluorescence spectroscopy revealed that the newly formed FeS sequestered substantial amounts of As. Bulk and microfocused As K-edge X-ray absorption near-edge structure spectroscopy confirmed that As(V) was reduced to As(III) and showed that in the presence of FeS, solid-phase As was retained partly via the formation of an As2S3-like species. High resolution transmission electron microscopy suggested that this was due to As retention as an As2S3-like complex associated with mackinawite (tetragonal FeS) rather than as a discrete As2S3 phase. This study shows that mackinawite formation in contaminated floodplain soil can help mitigate the extent of arsenic mobilization during prolonged flooding.

It is demonstrated in model experiments that in the presence of Ca ions (typomorphous cations of water of the Yenisei River) fulvic acids of floodplain soils and associated radionuclides (Am, Eu) form poorly soluble mixed Ca, Fe, Al(Am, Eu) fulvates. As a result, under the flooding conditions the migration of Am and Eu in the form of solubilized organomineral complexes is practically totally suppressed. With decreasing pH in the model system from 8 to 6 the mobility of the radionuclides noticeably increases.

study area was assessed with respect to its heavy-metal load on the basis of the current guideline values. The heavy-metal loads of the soils in the study area have ranges of

A novel mercury-specific sequential extraction procedure (SEP) for the assessment of mercury (Hg) speciation in soils and sediments, with emphasis on studying the interaction between Hg and organic matter (OM), was developed and tested. It was applied to determine Hg speciation in floodplain topsoils and surface sediments along the Hg-contaminated part of the river Elbe, and to simultaneously derive some information on the (re)mobilization potentials for Hg from these matrices. The majority of the total Hg in the ecosystem today is bound in the floodplains, which also still geographically reflect the historic emission record. Most of the Hg in both matrices is bound strongly to OM, suggesting low availability. However, distinct differences between Hg speciation in the floodplain soils and sediments were also discovered. Mercury deposited in the floodplains shows speciation patterns that indicate stronger fixation compared with Hg in the sediments. This difference is attributed to the association of Hg with larger quantities of OM, which presumably also has higher molecular weight (MW). By comparison, Hg in the sediments was distributed among weaker binding forms, which are more likely to liberate Hg. Particularly, sediments showed a total lack of sulfidic binding forms for Hg. Pronounced geographical trends were detected in the Hg speciation along the river transect, with a general downstream shift from weaker to stronger binding forms, probably due to increased association with OM. These studies indicate that Hg speciation in riverine ecosystems is dynamic and reflects the chemical mechanisms underlying (bio)geochemical processes like distribution and transport.

The study deals with the combined contribution of polycyclic aromatic hydrocarbons (PAHs) and metals to health risk in Delhi soils. Surface soils (0–5 cm) collected from three different land-use regions (industrial, flood-plain and a reference site) in Delhi, India over a period of 1 year were characterized with respect to 16 US Environmental Protection Agency priority PAHs and five trace metals (Zn, Fe, Ni, Cr and Cd). Mean annual ∑16PAH concentrations at the industrial and flood-plain sites (10,893.2 ± 2826.4 and 3075.4 ± 948.7 μg/kg, respectively) were ~15 and ~4 times, respectively, higher than reference levels. Significant spatial and seasonal variations were observed for PAHs. Toxicity potentials of industrial and flood-plain soils were ~88 and ~8 times higher than reference levels. Trace metal concentrations in soils also showed marked dependencies on nearness to sources and seasonal effects. Correlation analysis, PAH diagnostic ratios and principal component analysis (PCA) led to the identification of sources such as coal and wood combustion, vehicular and industrial emissions, and atmospheric transport. Metal enrichment in soil and the degree of soil contamination were investigated using enrichment factors and index of geoaccumulation, respectively. Health risk assessment (incremental lifetime cancer risk and hazard index) showed that floodplain soils have potential high risk due to PAHs while industrial soils have potential risks due to both PAHs and Cr.

Concentrations of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) in Tittabawassee River floodplain soils and biota downstream of Midland, Michigan, USA, are greater than regional background concentrations. From 2005 to 2008, a multiple lines of evidence approach was utilized to evaluate the potential for effects of PCDD/DFs on American robins (Turdus migratorius) breeding in the floodplains. A dietary-based assessment indicated there was potential for adverse effects for American robins predicted to have the greatest exposures. Conversely, a tissue-based risk assessment based on site-specific PCDD/DF concentrations in American robin eggs indicated minimal potential for adverse effects. An assessment based on reproductive endpoints indicated that measures of hatch success in study areas were significantly less than those of reference areas. However, there was no dose-response relationship between that endpoint and concentrations of PCDD/DF. Although dietary-based exposure and reproductive endpoint assessments predicted potential for adverse effects to resident American robins, the tissue-based assessment indicates minimal to no potential for adverse effects, which is reinforced by the fact the response was not dose related. It is likely that the dietary assessment is overly conservative given the inherent uncertainties of estimating dietary exposure relative to direct tissue-based assessment measures. Based on the available data, it can be concluded that exposure to PCDD/DFs in the Tittabawassee River floodplain would not likely result in adverse population-level effects to American robins. Environ Toxicol Chem 2013;32:1304–1316. © 2013 SETAC

Vanadium (V) is a naturally occurring trace element, but total concentrations in soils and sediments are also dependent on the parent material and might be influenced by anthropogenic activities (e.g., steel industry). Despite the fact that threshold values for V in soils and/or sediments exist in various European countries, in Belgium, V is not taken into account when the environmental quality of soils and sediments has to be evaluated, despite the existence of several (diffuse) sources for V. In the first part of the study, the occurrence of V alluvial soils in Belgium was compared with V concentrations in alluvial soils (floodplain soils) across Europe. By analysis of both the Belgian and European data, the relationship between physicochemical soil characteristics and total V concentrations was quantified and some areas polluted with V were detected. A regression equation, in which V concentrations in alluvial soils were expressed as a function of major element composition, was proposed for the Belgian and European data. Additionally, single extractions with CaCl2(0.01 mol L-1) and ammonium-EDTA (0.05 mol L-1) were used to estimate short- and long-term mobility of V in the alluvial soils.

Several fractions of technogenic radionuclides were separated from floodplain soil by sequential extraction, among them radiocolloids of 60Co and Eu nuclides associated with components of polymeric organomineral films [Fe(III) and Al(III) oxides and hydroxides] and organomineral complexes of 60Co, 137Cs, and Eu nuclides with humic compounds. Changing the oxidizing agent, H2O2, for chromic acid in the sequential extraction procedure allowed a considerable increase in the yield of the radionuclides to the solution: from 6.5 to 46% for 60Co, from 1.4 to 36% for 137Cs, and from 5.2-8.5 to 23-32% for the Eu isotopes.

This paper reviews the role of earthworms in the early colonisation of contaminated soils as well as sediment and waste deposits, which are worm-free because of anthropogenic activities such as open-cast mining, soil sterilisation, consistent pollution or remediation of contaminated soil. Earthworms live in close interaction with their soil environment and are able to change it considerably by their burrowing and litter comminuting behaviour. While earthworms have been studied extensively, several questions still remain unanswered such as: What are the characteristics of successful early colonisers? Do they function well in dispersal, individual establishment or population growth? Do the negative environmental conditions in these kinds of anthropogenic soils hamper colonization or are these colonizers relatively resistant to it? To what extent does colonization change the characteristics of the colonized substrate? In short, do earthworms impact the soil? In this paper, the characteristics that make earthworms successful colonisers are briefly described as well as which species are the most successful and under what circumstances, and what do earthworms contribute to the total process of succession. We propose that it is not so much eco-type or r-K strategy that govern success and succession of earthworm colonisation but rather environmental flexibility not only towards pH, desiccation, and temperature but also towards contaminants such as heavy metals. Moreover, the formation of an organic litter layer, in close connection with re-vegetation of the area, is essential for establishing earthworm populations, which, at first, are mainly superficially and shallow active species. The burrowing and organic matter digesting activity of these earthworms changes the upper soil to a well mixed humus layer suitable for deep burrowing earthworm species.

Five soil profiles were studied along a soil sequence in the Niger river floodplain to determine their soil properties and water-stable aggregates (WSA) between 4.75-2.00 mm, 2.00-1.00 mm, 1.00-0.50 mm, 0.50-02.5 mm and Key words: Soil organic carbon, Water-stable aggregates, Floodplain, C/N ratio, Soil profile. Agro-Science Vol.2(2) 2001: 52-61

Trace elements are potentially toxic to human life and the environment. Element toxicity depends on chemical associations in soils. Therefore, determining the chemical form of an element in soils is important to evaluate its mobility and bioavailability. Initial soil development in river floodplains influences soil properties, processes and therefore behavior of trace elements. In this study, three different floodplain soils sampled at three rivers (Nile/Egypt, Elbe/Germany and Penios/Greece) were used to link soil development and properties to the geochemical fractions and mobility of some trace elements. Sequential extraction was used to fractionate five trace elements (Cd, Cu, Ni, Pb and Zn) into five operationally defined groups: water soluble + exchangeable, carbonate, Fe-Mn oxide, organic, and residual. German soil showed the highest total concentration of the studied elements (except Ni). The Greek soil had the greatest amount of Ni. The residual fraction was the abundant pool for the studied elements examined in the Egyptian and Greek soils while the non-residual fraction was the dominant pool for all elements in the German soil. A significant amount (71- 94%) of all elements was present in German soil in the potentially available fraction: non-residual fraction, while the amount of this fraction ranged between 9 and 39 % in Greek soil and between 9 and 34 % in Egyptian soil. These suggest that the potential availability of the studied trace elements was extremely high in German soil compared to the Egyptian and Greek soil. In the German soil, most of the non-residual Cd, Ni and Zn were bounded with the Fe-Mn oxide fraction, while Cu and Pb distributed in the organic fraction. While in the Egyptian and Greek soils Fe-Mn oxide fraction was the abundant pool for the studied elements except for Cd, in which the exchangeable and the carbonate fractions had the greatest amount of Cd. Assuming that mobility and bioavailability of these elements are related to their solubility and geochemical forms, and that they decrease in the order of extraction sequence, the apparent mobility and potential bioavailability for the studied elements in the soils were: Cu > Cd > Ni ≥ Pb = Zn in Egyptian soil, Cd > Cu > Pb> Ni = Zn in Greek soil and Cd > Zn> Pb> Cu > Ni in German soil.