This paper reviews the factors affecting trace metal behaviour in estuarine and riverine floodplain soils and sediments. Spatial occurrence of processes affecting metal mobility and availability in ...floodplains are largely determined by the topography. At the oxic–anoxic interface and in the anoxic layers of floodplain soils, especially redox-sensitive processes occur, which mainly result in the inclusion of metals in precipitates or the dissolution of metal-containing precipitates. Kinetics of these processes are of great importance for these soils as the location of the oxic–anoxic interface is subject to change due to fluctuating water table levels. Other important processes and factors affecting metal mobility in floodplain soils are adsorption/desorption processes, salinity, the presence of organic matter, sulphur and carbonates, pH and plant growth. Many authors report highly significant correlations between cation exchange capacity, clay or organic matter contents and metal contents in floodplain soils. Iron and manganese (hydr)oxides were found to be the main carriers for Cd, Zn and Ni under oxic conditions, whereas the organic fraction was most important for Cu. The mobility and availability of metals in a floodplain soil can be significantly reduced by the formation of metal sulphide precipitates under anoxic conditions. Ascending salinity in the flood water promotes metal desorption from the floodplain soil in the absence of sulphides, hence increases total metal concentrations in the water column. The net effect of the presence of organic matter can either be a decrease or an increase in metal mobility, whereas the presence of carbonates in calcareous floodplain soils or sediments constitutes an effective buffer against a pH decrease. Moreover, carbonates may also directly precipitate metals. Plants can affect the metal mobility in floodplain soils by oxidising their rhizosphere, taking up metals, excreting exudates and stimulating the activity of microbial symbionts in the rhizosphere.
An automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) ...as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg Hg kg−1 and >30 mg Hg kg–1). The experiment was conducted under stepwise variation from reducing (approximately −350 mV at pH 5) to oxidizing conditions (approximately 600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10Me16:0, cy17:0, 10Me18:0, cy19:0) or Desulfovibrio species (18:2ω6,9), which are considered to promote Hg methylation. The products of the methylation process are lipophilic, highly toxic methyl mercury species such as the monomethyl mercury ion MeHg+, which is named as MeHg here. The ln(MeHg/Hgt) ratio is assumed to reflect the net production of monomethyl mercury normalized to total dissolved Hg (Hgt) concentration. This ratio increases with rising dissolved organic carbon (DOC) to Hgt ratio (ln(DOC/Hgt) ratio) (R2 = 0.39, p<0.0001, n= 63) whereas the relation between ln(MeHg/Hgt ratio and lnDOC is weaker (R2 = 0.09; p<0.05; n = 63). In conclusion, the DOC/Hgt ratio might be a more important factor for the Hg net methylation than DOC alone in the current study. Redox variations seem to affect the biogeochemical behavior of dissolved inorganic Hg species and MeHg indirectly through related changes in DOC, sulfur cycle, and microbial community structure whereas EH and pH values, as well as concentration of dissolved Fe3+/Fe2+ and Cl– seem to play subordinate roles in Hg mobilization and methylation under our experimental conditions.
Floodplain soils at the Elbe river are frequently polluted with metals and arsenic. High contents of these pollutants were detected down to subsoil layers. NH
4NO
3-extractable (phytoavailable) Cd, ...Ni, and Zn were elevated in horizons with high acidity. Among five common floodplain plant species,
Artemisia vulgaris showed highest concentrations of Cd, Cu, and Hg,
Alopecurus pratensis of As and
Phalaris arundinacea of Ni, Pb, and Zn. Relationships were weak between metal concentrations in plants and phytoavailable stocks in soil. As and Hg uptake seems to be enhanced on long submerged soils. Enrichments of Cd and Hg are linked to a special plant community composition. Grassland herbage sampled in July/August revealed higher concentrations of As (+122%), Hg (+124%), and Pb (+3723%) than in May. To limit harmful transfers into the food chain, low-lying terraces and flood channels revealing highest contaminations or phytoavailabilities should be excluded from mowing and grazing.
Soils in the Elbe river floodplains are highly polluted with metals and arsenic and a critical enrichment in the grassland herbage seems to be most likely in flood channels or within special plant species.
In this review, we present the environmental perspectives of the viruses and antiviral drugs related to SARS-CoV-2. The present review paper discusses occurrence, fate, transport, susceptibility, and ...inactivation mechanisms of viruses in the environment as well as environmental occurrence and fate of antiviral drugs, and prospects (prevalence and occurrence) of antiviral drug resistance (both antiviral drug resistant viruses and antiviral resistance in the human). During winter, the number of viral disease cases and environmental occurrence of antiviral drug surge due to various biotic and abiotic factors such as transmission pathways, human behaviour, susceptibility, and immunity as well as cold climatic conditions. Adsorption and persistence critically determine the fate and transport of viruses in the environment. Inactivation and disinfection of virus include UV, alcohol, and other chemical-base methods but the susceptibility of virus against these methods varies. Wastewater treatment plants (WWTPs) are major reserviors of antiviral drugs and their metabolites and transformation products. Ecotoxicity of antiviral drug residues against aquatic organisms have been reported, however more threatening is the development of antiviral resistance, both in humans and in wild animal reservoirs. In particular, emergence of antiviral drug-resistant viruses via exposure of wild animals to high loads of antiviral residues during the current pandemic needs further evaluation.
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•We analysed environmental perspectives of antiviral drugs and SARS-CoV-2.•Susceptibility and inactivation causes seasonality in the prevalence of SARS-CoV-2.•Surface-charge interactions govern environmental fate and transport of SARS-CoV-2.•Unprecedented use of antiviral drugs is hazardous to the environment.•Emergence of antiviral drug-resistant viruses needs further investigations.
Seasonal dynamics of microbial community under frequently fluctuating oxidized and reduced conditions in floodplain soils are poorly understood, but are considered to be important for understanding ...microbial community and carbon cycling dynamics in these ecosystems. We determined the microbial community structure using phospholipid fatty acid analysis (PLFA) of three different floodplain soils (Eutric Gleysol = GLe, Eutric Fluvisol = FLe, and Mollic Fluvisol = FLm) at the Elbe River, Germany, for 17 months. Flood duration, soil moisture, soil temperature were also monitored, and hot and cold water extractable carbon (CHWE, CCWE) were determined. Flood duration seems to have a negative impact on total PLFA biomass which increased in the order GLe < FLe << FLm. All PLFA profiles were dominated by Gram-positive bacteria (GPB) and actinomycetes, respectively, and a low content of fungi and arbuscular mycorrhizal fungi (AMF). In the briefly flooded relatively quickly drained soils (FLe and FLm) Gram-negative bacteria (GNB) were abundant compared to the longer flooded, relatively slow drained soil (GLe). This was also obvious in the significant lowest fungi-bacteria ratio and aerobe-anaerobe ratio of GLe. Non-metric dimensional scaling (NMDS) and canonical discriminant analysis (CDA) as multivariate statistical procedures reveal that FLm could be separated from GLe and FLe probably due to aerobic conditions and available soil organic carbon. The GLe can be discriminated from FLe and FLm mainly due to different flooding durations. The GNB, fungi and AMF were more affected by changes of soil moisture and extractable carbon than the GPB, actinomycetes and anaerobes. We conclude that more stable properties of bulk soil such as the magnitude of soil organic carbon, soil texture, and associated flood duration had a stronger impact on soil microbial community than monthly fluctuations of more dynamic properties, such as soil moisture, soil temperature, and CHWE, CCWE in our soils.
•Three different floodplain soils can be discriminated via microbial community.•Stable soil features determine microbial community stronger than dynamic properties.•Long-term flooded soil shows lowest fungi–bacteria-ratio and aerobe–anaerobe-ratio.•Mollic Fluvisol has highest fungi–bacteria-ratio and aerobe–anaerobe-ratio.
Vanadium (V), although serving as an important component of industrial activities, has bioinorganic implications to pose highly toxic hazards to humans and animals. Soils and sediments throughout the ...world exhibit wide ranges of vanadium concentrations. Although vanadium toxicity varies between different species, it is mainly controlled by soil redox potential (EH). Nonetheless, knowledge of the redox geochemistry of vanadium lags in comparison to what is known about other potentially toxic elements (PTEs). In particular, the redox-induced speciation and mobilization of vanadium in soils and sediments and the associated risks to the environment have not been reviewed to date. Therefore, this review aims to address 1) the content and geochemical fate of vanadium in soils and sediments, 2) its redox-induced release dynamics, 3) redox-mediated chemical reactions between vanadium and soil organic and inorganic colloidal materials in soil solution, 4) its speciation in soil solution and soil-sediments, and 5) the use of advanced geochemical and spectroscopic techniques to investigate these complex systems. Vanadium (+5) is the most mobile and toxic form of its species while being the thermodynamically stable valence state in oxic environments, while vanadium (+3) might be expected to be predominant under euxinic (anoxic and sulfidic) conditions. Vanadium can react variably in response to changing soil EH: under anoxic conditions, the mobilization of vanadium can decrease because vanadium (+5) can be reduced to relatively less soluble vanadium (+4) via inorganic reactions such as with H2S and organic matter and by metal-reducing microorganisms. On the other hand, dissolved concentrations of vanadium can increase at low EH in many soils to reveal a similar pattern to that of Fe, which may be due to the reductive dissolution of Fe(hydr)oxides and the release of the associated vanadium. Those differences in vanadium release dynamics might occur as a result of the direct impact of EH on vanadium speciation in soil solution and soil sediments, and/or because of the EH-dependent changes in soil pH, chemistry of (Fe)(hydr)oxides, and complexation with soil organic carbon. Release dynamics of vanadium in soils may also be affected positively by soil pH and the release of aromatic organic compounds. X-ray absorption spectroscopy (XAS) is a powerful tool to investigate the speciation of vanadium present in soil. X-ray absorption near edge structure (XANES) is often used to constrain the average valence state of vanadium in soils and sediments, and in limited cases extended X-ray absorption fine structure (EXAFS) analysis has been used to determine the average molecular coordination environment of vanadium in soil components. In conclusion, this review presents the state of the art about the redox geochemistry of vanadium and thus contributes to a better understanding of the speciation, potential mobilization, and environmental hazards of vanadium in the near-surface environment of uplands, wetlands, and agricultural ecosystems as affected by various colloidal particles. Further research is needed to elucidate the geochemistry and speciation of vanadium in the dissolved, colloidal, and soil sediments phases, including the determination of factors that control the redox geochemistry of vanadium.
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•The review presents the state of the art of the redox geochemistry of Vanadium (V).•The EH-dependent changes of pH, Fe oxides, and organic carbon affect V mobilization.•XAS is a powerful tool to investigate the speciation of V present in soil.•XANES is used to constrain the average valence state of V in soils and sediments.•The review contributes to a better understanding of the environmental hazards of V.
Inductively Coupled Plasma Mass Spectrometry (ICP-MS) hyphenated to High Performance Liquid Chromatography (HPLC) and Ion Chromatography (IC) are widely used for simultaneous speciation of arsenic ...(As). Longer retention time resulting in a slow separation is the major drawback of these existing approaches. Besides, fast separations achieved from HPLC based methods have always resulted in poor resolution and baseline separation between peaks. For the first time, the present study aimed to improve the existing HPLC related methods in order to develop a fast analytical protocol based on Ultra-High Performance Liquid Chromatography (UHPLC) hyphenated to ICP-MS detection for simultaneous separation and quantification of arsenite (As(III)), arsenate (As(V)), dimethylarsonate (DMA(V)) and monomethylarsenate (MMA(V)). Two types of ammonium-based mobile phases (i.e. NH4H2PO4 and NH4NO3) were examined at different eluent concentrations and pH to choose the most effective eluent system. Results demonstrated that the mixed mobile phase containing 8.5 mM of NH4H2PO4 and NH4NO3 (1:1) at pH 6.0 is the most effective eluent achieving the separation of As species with improved resolutions within 5 min which is almost a double saving in analysis time per sample compared to the existing methods (9–15 min). Faster separation is analytically cost effective in terms of ICP-MS running cost and energy consumption. Unlike HPLC, UHPLC did not generate a higher column back pressure with increasing flow rate up to 2.5 mL/min resulting in a faster separation with excellent resolution of peaks. Limits of detection for As species were in the range of 0.3–0.5 μg/L. The proposed method was applied to quantify As species present in commercially available rice varieties in Australia and Sri Lanka. Results of speciation analysis indicated that As(III) is the dominant species, ranging from 53 to 100% in the rice grains. The proposed analytical protocol based on UHPLC-ICP-MS provided an accurate and reliable identification and quantification of As species with the advantages of rapid separation, excellent resolution, and low detection limits. Such a recent trend in fundamental research could be a turning point for future environmental and biological research to further improve this strategy for the speciation of other toxic metal(loid)s in food, water and biological samples.
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•A fast analytical protocol by UHPLC coupled to ICP-MS for arsenic speciation.•Full separation of As(III), DMA(V), MMA(V) and As(V) achieved within 5 min.•It is a double serving of analysis time per sample compared to existing methods.•Unlike HPLC, UHPLC generates lower column back pressure with increasing flowrate.•UHPLC-ICP-MS is a promising analytical tool for a rapid analysis of samples.
Different methods exist for measuring water and solute flux in and below the root zone. Besides indirect methods (e.g. water balance, tensiometer, time domain reflectometry, frequency domain ...reflectometry and environmental tracer), direct methods (e.g. drainagetype lysimeter, water flux meter) have a long tradition and have been successfully used in seepage research. However, lysimeters are most reliable and accurate for in situ water and solute assessment. A large weighable outdoor lysimeter is the best method for obtaining reliable data about seepage water quantity and quality, but it involves significant investment and additional expenses for maintenance. To tackle this problem new methods for the vertical collection of large volume soil monoliths and for the placement of the lysimeter in a container lysimeter unit have been developed. The design of lysimeters typically used in Europe – a weighable gravitation lysimeter and a weighable groundwater lysimeter are explained. An example is given for the high precision of the new lysimeter weighing technique. Besides recording rainfall and seepage, its weighing precision makes it possible to register mass input by dew, fog or rime. It also permits accurate calculation of actual evapotranspiration. The newly developed lysimeter types will be an essential tool for scaling up results obtained in small-scale experiments to larger geographical units. Furthermore, the newly developed experimental set-up allows a scenario simulation of topical climatic and hydrologic questions, e.g. global warming and its impact on the water and solute balance, the influence of dew and fog on the establishment of a vegetation cover in arid areas or the transport of contaminants during heavy rainfall following a severe drying-up of the soil profile.
The immobilization of toxic metals in soils using amendments is a cost-effective remediation technique for contaminated soils. Therefore, this study aimed to assess the efficiency of various ...amendments to immobilize nickel (Ni) and zinc (Zn) in soil and reduce their phytoavailability. A greenhouse pot experiment was established with a contaminated agricultural floodplain soil. The soil was treated with activated carbon (AC), bentonite (BE), biochar (BI), cement bypass kiln dust (CBD), chitosan (CH), coal fly ash (FA), limestone (LS), nano-hydroxyapatite (HA), organo-clay (OC), sugar beet factory lime (SBFL), and zeolite (Z) with an application rate of 1 % (0.2 % for HA) and cultivated by rapeseed (
Brassica napus
). After plant harvesting, the soil was analyzed for water-soluble and geochemical fractions of Ni and Zn. Additionally, both metals were analyzed in the aboveground biomass. Application of the amendments increased significantly the biomass production of rapeseed compared to the control (except for OC, HA, and FA). Water-soluble Ni and Zn decreased significantly after adding the amendments (except OC, Z, and CH). The SBFL, CBD, LS, BE, AC, and BI were most effective, resulting in a 58–99 and 56–96 % decrease in water-soluble Ni and Zn, respectively. The addition of SBFL, CBD, and LS leads to the highest decreasing rate of concentrations of Ni in plants (56–68 %) and Zn (40–49 %). The results demonstrate the high potential of CBD, SBFL, LS, BE, AC, and BI for the immobilization of Ni and Zn in contaminated floodplain soils.
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