The effects of long-standing industrialization processes and poor environmental management practices have often left a harmful legacy for marine-coastal sites worldwide, causing a wide range of unforeseen impacts on the ecosystem and on human health. A critical revision of available data from three highly contaminated Italian sites (Augusta Bay, Sicily; Cagliari Gulf, Sardinia; Pozzuoli Bay, Campania) revealed the crucial role of biogeochemical/physical dynamics and potential widespread delivery of contaminants as key components for a wider comprehensive sediment management.
Materials and methodsDatasets of organic pollutants (ΣPAHs, ΣPCBs), heavy metals (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, V, and Zn), radionuclides, and grain size composition of marine sediments of all three sites were critically reviewed and seafloor bathymetric data were analyzed.
Results and discussionA critical review of available physical and chemical information of sediments collected from the three marine sites provides a better understanding of the physical and biogeochemical dynamics of large-scale dispersion of contaminants in those areas, as well as new insights in terms of improved sediments management policies with actions of larger scale monitoring of the “buffer zone” confining with the national relevance and highly contaminated site to trace inputs and accumulation effects of pollutants deriving from the point-source.
ConclusionsThis study demonstrates how the presence of polluted sediments on the coastal areas can have, also after the closure of anthropogenic activities, a potential impact at a large scale. Then to better evaluate the effective impact, we suggest the adoption of a buffer zone contiguous to the national relevance sites (SIN) area. While SINs are optimized to define the state of the art of the near-source pollution, buffer zones may help to outline the rate of delivery of pollutants to the deep sea. Buffer zones must be designed by taking into account the local hydrodynamics, sedimentology, and geomorphology, and should be monitored, even if at a lower resolution, like SINs.
相似文献Here, the roles of sediment components in perfluorooctane sulfonate (PFOS) adsorption onto aquatic sediments and relevant adsorption mechanisms were investigated in terms of adsorption isotherms and influences of TiO2 nanoparticles (NPs) contamination.
Materials and methodsDue to the complexity of the sediments, instead of randomly selecting different component sediments, the selective dissolution method was used to better explore the effects of sediment compositions, such as sediment organic matter (SOM) and ferric oxides (dithionite–citrate–bicarbonate [DCB] Fe), and TiO2 NPs pollution on PFOS adsorption. Mathematical equations (Freundlich, Langmuir, and Temkin) were used to describe the adsorption behavior of PFOS on different sediments and adsorption mechanisms of multiple pollutant interactions. Moreover, the characterization methods of zeta potential, nitrogen (N2) adsorption–desorption, and scanning electron microscopy (SEM) analysis, as well as Fourier transform infrared (FT-IR) spectroscopy, explained effects of the sediment components and TiO2 NPs on PFOS adsorption properties in view of physicochemical theories.
Results and discussionThe adsorption isotherms of PFOS on six tested sediments were all nonlinear (Freundlich model, R2 = 0.992~1.000). The Freundlich sorption affinities (KF) of PFOS on S (original sediments), S1 (sediment organic matter (SOM)-removed S), and S2 (ferric oxides (DCB Fe)-removed S1) were 0.232, 0.179, and 0.120, respectively. Both SOM and DCB Fe influenced the physicochemical properties of the sediments, e.g., zeta potential, specific surface area, and permanent negative charge. The addition of TiO2 NPs increased the KF of PFOS for S, S1, and S2 by approximately 9.9%, 14.5%, and 26.7%, respectively, by increasing the zeta potential and specific surface area (SBET, Sext, and Smicro) and by changing the water and oil properties of the three sediments. However, the addition of TiO2 NPs decreased the linearity of the sorption isotherm (1/n). FT-IR spectroscopy showed that hydrophobicity, ion exchange, surface complexation, and hydrogen bonding interactions (non-fingerprint region) could all play a role in PFOS sorption onto tested sediments. However, the hypothesis of hydrogen bonding to promote PFOS adsorption on sediment layer silicates (fingerprint region) should be studied further.
ConclusionsThe content of both SOM and DCB Fe affected the physicochemical properties of sediment. Both SOM and DCB Fe showed a positive relationship with sorption of PFOS on sediment. The addition of TiO2 NPs increased PFOS sorption by altering the sediment surface properties. Hydrophobic interactions certainly impelled and ligand and ion exchange and hydrogen bonding (non-fingerprint region) could promote PFOS sorption on the sediments.
相似文献Fluvial sediments can act as archives for lipophilic pollutants. However, their distribution within the highly dynamic regime of the river corridor is scarcely investigated. Herein, a novel approach combining geochemical investigations of sediment bodies in the river corridor of the Wurm River (catchment < 400 km2) and aerial photograph evaluation provide information about the history of river course change and the distribution of pollution by selected persistent organic compounds (POPs) and selected heavy metals.
Materials and methodsThe study is based on nine sediment cores and a total number of 45 subsamples. The sediment samples were analyzed for trace element inventory (X-ray fluorescence), grain size composition (laser diffraction particle size analyzer), and organic compounds (chromatography-mass spectrometry). On the basis of quantitative data of persistent organic substances as well as three heavy metals (Cu, Pb, and Zn) and morphological changes from 1953 until 2016 of the area of investigation provided by eight aerial photographs, analyzed sediments were assigned to different decades, and lateral migration rates as well as deposition rates were calculated.
Results and discussionHigh morphodynamics within the river corridor limits the explanatory power of single approaches (for example, geochronology and radiometric dating). However, a combination enables further insight into floodplains such as the pollution history, spatial pollutant dispersal, hotspot localization, meander migration rates (0.2–0.5 m year?1), sedimentation rates (0.5–5.2 cm year?1) and estimation of hotspot remobilization. Quantitative data for the analyzed heavy metals (Cu, Pb, and Zn) show a decreasing trend for locations with younger sediment bodies, whereas quantitative data for the synthetic organic pollutants reflect the corresponding history of emissions with increasing concentrations until a climax followed by decreasing concentrations due to restrictions regarding their application.
ConclusionsResults reveal hotspot areas for POPs and their degree of remobilization. This study demonstrates that by knowing the history of emissions of a lipophilic substance, potential hotspots can be localized solely based on a sufficient number of aerial photographs documenting the river channel migration and sediment body formation in the corresponding period of time.
相似文献The pollution of marine sediments by heavy metals is still a major concern, especially in zones affected by industry or mariculture. Toxicity of sediment heavy metal contents may be assessed using sequential extraction (SE) procedures, minding inherent constraints of such approaches. In this study, we investigated heavy metal speciation and toxicity in anoxic marine sediments in Zhelin Bay, a mariculture bay in Southern China, using an SE and acid volatile sulfur-simultaneously extracted metals (AVS-SEM) approach.
Materials and methodsSpeciation of Cd, Cu, Ni, Pb, and Zn were studied by a modified SE of five fractions, adapted to separate organic and sulfidic metal fractions in anoxic sediments: F1 weak acid soluble (readily available), F2 reducible fraction, F3 organic matter-bound fraction, F4 sulfide-bound fraction, and F5 residually bound fraction. Toxicity predictions based on the sum of non-residual (NR) metal fractions from sequential extraction were compared to predictions based on AVS-SEM.
Results and discussionResults showed that Cd, Ni, and Pb predominantly occurred in the weak acid soluble fraction (F1), residual fraction (F5), and sulfide-bound fraction (F4), respectively; Cu and Zn were mainly obtained in F4 and F5. Based on the distribution of indicator elements for metal fractions, the SEM from AVS extraction included different yields of non-residual and residual fractions besides the sulfidic fraction. Estimates for potential heavy metal toxicity based on NR metals of the SE procedure were thus based on a better-defined speciation compared to the simplistic approach of the AVS-SEM method.
ConclusionsBased on the contents of NR metals and normalizing them by organic matter content, toxic effects are not expected for any of the sampling sites, irrespective of the presence or absence of mariculture. Using Pearson correlation analysis to identify predominant fractions influencing toxicity, we conclude that toxicity of heavy metals in anoxic sediments can be well predicted by their non-residual heavy metal contents.
相似文献This paper focuses on determining the geochemical fractionation pattern of trace elements (As, Cd, Cu, Pb, Tl, and Zn) naturally occurring at elevated levels in chestnut grove soils of SW Spain. The goal was to explore how environmental changes triggered by land use and management decisions might affect the resilience and adaptive capacity of soil to retain geogenic trace elements.
Materials and methodsTwo plausible scenarios were considered: conversion of forestland to cropland (scenario I) and mining area (scenario II). The potential for trace element removal under the assumed scenarios was assessed by chemical extraction procedures designed to simulate the combined effects of experimentally induced pH and redox changes. Trace elements were partitioned into residual and labile fractions using a five-step sequential extraction scheme optimized for soils enriched in well-crystallized Fe oxides, and their concentrations in the soil extract solutions were measured by inductively coupled plasma mass spectrometry.
Results and discussionMost metals are tightly bonded to residual and reducible phases, indicating that silicate minerals and Fe oxy-hydroxides, respectively, played a remarkable role in the metal geo-accumulation. Limited mobilization and dispersion of exchangeable and acid-soluble contaminants would be expected to occur through releases or accidental spills from hazardous wastes. An increase in the oxidation state of the soil environment would affect the stability of the organic matter involving the release of the associated trace elements, particularly Cu. Upon reducing conditions induced by land-degradation processes, reductive dissolution of Fe oxy-hydroxides could release large proportions (45–60%) of adsorbed and occluded potentially harmful elements, notably As, Pb, and Cd.
ConclusionsThe increasing abandonment of the chestnut groves constitutes a driving force for environmental changes that might affect the geochemical status of the trace elements stored in the soil. Soil could shift from a sink to a source of harmful contaminants over time. This fact should be considered by local stakeholders engaged in planning and decision-making on future land uses.
相似文献Suspended matter (SM) in streams is usually considered of minor importance in Danish environmental management. However, SM has some ecological effects as it may (1) clog fish spawning grounds and (2) act as an important agent for transport and exposure of biota to chemical substances, such as phosphorus and toxic inorganic (e.g. heavy metals) and organic (e.g. pesticides) substances.
Materials and methodsA large national data set of >?100,000 water samples analysed for SM and loss on ignition was investigated for spatial concentration patterns, sediment yields and temporal trends. Moreover, the importance of SM as a transport agent for phosphorus and heavy metals in streams was investigated through a correlation analysis.
Results and discussionThe mean suspended matter concentration (SMC) (including organic matter) amounted to 12 mg l?1, with an organic content of 4.9 mg l?1 (41%). A clear difference in SMC temporal trends over the sampling period was found between geographical regions. Sediment yields were calculated for all major catchments revealing low sediment yields (1–15 t km?2 year?1) compared to neighbouring countries and showed clear geographical patterns. Statistically significant relationships were established between SMCs, suspended sediment concentrations (SSCs) (excluding organic matter) and organic matter concentrations (OMCs) and particulate phosphorus (PP) concentrations, and again spatial patterns appeared. However, it was clearly shown that SMC/SSC/OMC could not be used as a robust, nationwide, indicator for PP concentrations. Analyses of the relationship between SMC and particle-bound heavy metal concentrations generally revealed weak correlations except for Pb and Ni (median R2?>?0.3).
ConclusionsRelatively low SM concentrations and sediment yields were found. SM is, in some geographical regions, an important transport agent for PP. Clear geographical patterns occurred in the relationships between SMC/SSC/OMC and both river water discharge and PP, as well as for sediment yields and for temporal trends in SMC.
相似文献Potentiometric and ion-selective electrode titrations together with batch sorption/desorption experiments, were performed to explain the aqueous and surface complexation reactions between kaolinite, Pb, Cd and three organic acids. Variables included pH, ionic strength, metal concentration, kaolinite concentration and time. The organic acids used were p-hydroxybenzoic acid, o-toluic acid, and 2,4-dinitrophenol. Titrations were used to derive previously unavailable aqueous conditional stability constants for the organometallic complexes. Batch results showed that aqueous lead-organic complexation reduced sorption of Pb by kaolinite. Cadmium behavior was similar, except for 2,4-dinitrophenol, where Cd sorption was increased. Metal sorption increased with increasing pH and decreasing ionic strength. Distribution ratios (K d 's) decreased with increasing solid/solution ratio. The subsurface transport of lead and cadmium may be enhanced via complex interactions with organic wastes or their degradation products and sorbent mineral surfaces.
相似文献This field study was performed to assess the variation in chemical and agronomic properties and total and extractable concentrations of heavy metals in soils fertilized with regulated doses of urban sewage sludge (USS) for 6 consecutive years in the framework of an agronomic treatment program.
Materials and methodsChemical and agronomical properties, total contents and extractable concentrations of Cd, Cr, Cu, Hg, Ni, Pb and Zn were determined in agricultural soils treated with USS for 6 consecutive years, agricultural soils cultivated using mineral fertilizers and uncultivated soils representative of the local geochemical background.
Results and discussionUSS application caused a decrease in pH and an increase in extractable concentrations of Cr, Cu, Pb and Zn. No organic carbon, total nitrogen and total phosphorus enrichment trend was observed in the treated soils due to biodegradation of the organic compounds supplied by USS. The decomposition of USS organic matter was presumably the main process responsible for the pH decrease in the USS-fertilized soils. There was no heavy metal accumulation in treated soils, and total heavy metal contents were below the corresponding maximum threshold concentrations set by European and Italian legislation. Increased availability of Cr, Cu, Pb and Zn was found in treated soils due to an increase in their extractable concentrations in the treatment period.
ConclusionsThe results of this study suggest that the environmental risks related to the accumulation and availability of heavy metals in agricultural soils fertilized with USS are limited when treatment observes recommended doses in agronomic treatment programs.
相似文献River sediment pollution by heavy metals/metalloids has attracted widespread attention due to a serious threat to the ecosystem and human health. As an effective and economical alternative, the stabilization method was considered by previous studies for the remediation of sediments polluted by metals/metalloids. However, a comprehensive study is required for an extensive comparison on the effects of metal/metalloid immobilization based on the application of different materials as sediment amendments.
Materials and methodsIn this study, the Maozhou River was selected as the study area, and the stabilization method was applied for the remediation of the river sediment polluted by metals and metalloids. Five materials (CaCO3, Ca(OH)2, zeolite, kaolin, FeCl2) were selected as amendments for the metal/metalloid stabilization in the collected sediment. A modified BCR procedure was employed for the speciation analysis of heavy metals and metalloid in the sediment before and after remediation. A TCLP (toxicity characteristic leaching procedure) investigation was performed to further evaluate the immobilization of heavy metals in acidic environment.
Results and discussionThe sediment of the Maozhou River was heavily polluted by heavy metals and metalloid. The speciation of As, Pb, Cr, and Mn mainly exists as residual fraction (F4), while that of Ni, Cu, and Zn was identified as exchangeable metal and carbonate-associated fraction (F1) and fraction associated with Fe-Mn oxides (F2). Moreover, the F2 fraction of Co was observed as the major speciation. Through the application of five materials (CaCO3, Ca(OH)2, zeolite, kaolin, FeCl2) as sediment amendments, the metal/metalloid speciation was transferred into F4. When five amendments were compared, the stabilization effect can be ordered as CaCO3?>?zeolite?>?FeCl2?>?kaolin?>?Ca(OH)2 based on the modified BCR results. TCLP results showed that using Ca(OH)2 and CaCO3 as amendments can significantly reduce the metal leachability in an acidic environment, while zeolite is effective for most of the heavy metals and metalloid.
ConclusionsThe results showed that the sediment of the Maozhou River was seriously polluted by a variety of heavy metals and metalloids. This study provided extensive information on the speciation of metals or metalloid and the effect of various amendments on metals and metalloid stabilization, which can be of vital importance for further remediation of metal/metalloid-polluted sediment.
相似文献A large-scale managed reed wetland in Yancheng Biosphere Reserve of China has been irrigated by treated papermaking wastewater (TPW) for approximately 8 to 12 years. This report details the risk evaluation of long-term TPW irrigation on the soil and its microbial viability, providing important perspective on the suitability of TPW reuse for irrigation.
Materials and methodsAn extensive field survey was employed for assessing the impacts of long-term TPW irrigation of reed fields (F1 to F6), as compared to river water irrigated field, on soil physicochemical properties, accumulation of heavy metals (Cu, Cd, Pb), soil enzyme activities (i.e., urease, invertase, catalase, and polyphenol oxidase), and soil microbial community metabolic profiles.
Results and discussionThe results revealed that long-term TPW reuse for irrigation resulted in a slight increase of pH value, while a remarkable increase was identified regarding to soil organic carbon, as expected from the organic carbon content of the wastewater, but was not proportional to the time of irrigation. TPW irrigation caused a remarkable increase in soil electrical conductivity and resulted in soil salinization, having strong correlation with the duration of irrigation. Soil salinization increase in irrigated area was mainly due to the high sodium content of the wastewater applied for irrigation. Furthermore, soil enzymes displayed significantly increased activities (except for catalase) in the irrigated fields, while the microbial ability of utilizing carbon source was enhanced. The diversity of microbial communities was boomed due to the increase of soil organic matter, as evidenced by the calculated diversity indices. However, a remarkable increase of heavy metals was also identified regarding Cd and Pb concentrations, which may pose potential risks to human health.
ConclusionsThe input of excessive pollutants and nutrients will disrupt the equilibrium mechanism of the wetland ecosystem. Although long-term TPW irrigation may increase the soil fertility and microbial activity, heavy metals (i.e., Cd and Pb) in wastewater can be accumulated in the soil. Furthermore, alkaline TPW caused an increase in soil salinity. Therefore, more cautions should be exercised in the reuse of TPW for irrigation.
相似文献Basing decisions for the management of contaminated sediments on ecotoxicological data is still often met with skepticism by European stakeholders. These concerns are discussed as they pertain to bioassays to show how ecotoxicological data may provide added value for the sustainable management of sediment in aquatic systems.
Materials and methodsFive “concerns” are selected that are often raised by stakeholders. The ecotoxicological practice is discussed in light of the knowledge gained in recent decades and compared with chemical sediment analysis and chemical data.
Results and discussionCommon assumptions such as a higher uncertainty of biotest results for sediments compared to chemical analyses are not supported by interlaboratory comparisons. Some confusion also arises, because the meaning of biotest data is often misunderstood, questioning their significance in light of a limited number of organisms and altered test conditions in the lab. Because biotest results describe a sediment property, they should not be directly equated with an impact upon the biological community. To identify a hazard, however, the possibility of false-negative results due to the presence of contaminants that are not analyzed but are toxic is lower.
ConclusionsThe cost of increased investment in ecotoxicological tests is, in our view, small compared with that of making false-negative assessments of sediment/dredged material that can ultimately have long-term environmental costs. As such, we conclude that ecotoxicological testing is an opportunity for sediment management decision-making that warrants more attention and confidence in Europe.
相似文献