Assessment of Highly Polluted Fluvisol in the Spittelwasser Floodplain Based on National Guideline Values and MNA-Criteria (11 pages)

Background, Goal and Scope

Nearly all large European rivers have been used as disposal pathways for several unwanted substances. Deposition of the contaminated solids occurs in regions of slack water and also during floods in adjacent floodplains. As a result of the recurrent input, most of the floodplains in central Europe are contaminated by manifold inorganic and organic pollutants, representing a risk for both plants and groundwater at the site, and for areas downstream. The aim of the present paper is to demonstrate and assess the sink and source functions of a highly contaminated 'fluvisol' (= alluvial soil) for inorganic and persistent organic pollutants. The extent of contamination is described on the basis of national guidelines. These results are further discussed on the basis of the 'monitored natural attenuation' (MNA) potential, i.e., with respect to the requirements for the cheapest problem solution for large scale contamination of floodplains. The MNA potential is assessed according to several lines of evidence such as contaminant burial, mechanical and chemical mobility, transformation to less toxic forms, and dilution due to dispersion.

Methods

The existing inorganic and organic pollutant status and the ecotoxicological potential of the Spittelwasser floodplain near Jeßnitz was documented by analysing several element and compound depth profiles of a typical alluvial soil site. Geochemical analyses were performed on solid material and soil solution according to standard procedures. In laboratory experiments monoliths were continuously irrigated with deionised water and the leachate was analysed weekly. In addition to the geochemical, the ecotoxicological status of the samples was studied using different biotests for the dissolved and the solid phase.

Results

The measured alluvial soil profile is severely contaminated with numerous inorganic and organic pollutants. Highest enrichment factors according to the catchment based, element specific geological background were found for Hg (402), Pb (8.9), Cr (7.1) and Cd (6.3). Assessment was made of the hazard potential of both the solid material and the soil solution according to the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV). Relating to the respective maximum contents in the soil profile, the overstepping of BBodSchV trigger values is highest for Hg with a coefficient of 49.0 followed by Cd (14.3), Pb (12.2), Zn (7.3), Cr (5.9) and Cu (3.6). Pollutant concentrations in the soil solution exceed the threshold values for Cd, Cu and Zn by factors of 6.3 to 12. While DDT is retained in the topsoil, there is a considerable translocation of HCH towards deeper horizons.

Discussion

The algae test confirms a strong toxicity in the top layer of the soil profile. In contrast, no such toxic reactions were indicated by the luminescent bacteria test and the Daphnia test at this depth. However, the deeper layers (10 - 100 cm) show a toxic reaction by the Daphnia test, thus indicating a relevant translocation of contaminants.

Conclusions and Perspectives

The Spittelwasser floodplain represents a significant sink for inorganic and persistent organic pollutants. Simultaneously, the area is a relevant secondary source of dissolving contaminants like heavy metals and HCH. Although strict criteria in the lines of evidence for applying MNA are not fulfilled, it can be stated that the alluvial soil offers a high natural retention potential for As, Hg, DDT, and PCDD/F. These pollutants are firmly retained and are not found in the soil leachate. This meets the demands of the EC-WFD for pollutant retention close to their primary source. But for agricultural use and groundwater recharge the natural attenuation potential of the soils in the Spittelwasser area will not be sufficient to achieve acceptable conditions medium-term. The main problem for the dissemination of pollutants is not chemical stability but mechanical dispersion. This is particularly the case for PCDD/F, with concentrations of more than 10,000 ng/kg I-TEQ in the upper Spittelwasser soil layers. Dispersion processes can result in a wide spatial contamination of downstream floodplains.     

Changes in agrophysical properties of floodplain soils under different anthropogenic loads

Agrophysical properties of alluvial soils were studied in the floodplains of the Oka River and the small rivers of Besputa (the Oka tributary) and Pol’noi Voronezh (the Voronezh tributary). The properties of the soils under different land use types (plowland, hayfield, pasture, and meadow) were compared. The features and degrees of alteration of the properties of the floodplain soils under different uses were determined. The greatest changes in the properties were found for saturated alluvial meadow soils of the Oka River floodplain under plowland. In these areas, strong degradation of the physical status of the soils was noted: compaction of the plow and subplow soil layers, an increase in the content of coarse aggregates and clods, changes in the porespace structure, and a decrease in the soil water permeability. It was shown that the soils of small river floodplains were sensitive to anthropogenic loads. In saturated alluvial soddy soils of the Besputa River floodplain, the soil water permeability decreased because of their compaction under the impact of cattle grazing. Saturated alluvial meadow soils of the Pol’noi Voronezh River floodplain were resistant to anthropogenic loads. Only a tendency towards an increase in the topsoil bulk density was observed under the impact of cattle grazing.     

Review of Ecological Engineering Solutions for Rural Non-Point Source Water Pollution Control in Hubei Province,China

Anthropogenic contamination by heavy metals in fluvial systems is mostly bound to fine-grained clay minerals and organic substances, which accumulate by vertical accretion in sediment traps along river courses (oxbow lakes, dams and floodplains). These environmental settings are considered as good archives of historical changes in contamination. Much less attention, however, is paid to deposits of river channels, which act as sourcing transport paths for these archives and/or build archives of their own. In order to provide a better insight into the spatio-temporal distribution of pollutants in channel deposits, we investigated contamination levels of Cu, Pb and Zn in a series of sediment cores along the River Morava, a left-hand tributary of the Danube River, Czech Republic. In particular, the relationships between metal concentrations, sediment lithology (facies), grain size, magnetic susceptibility and mineralogy and chemistry of fly-ash particles were investigated. Element chemistry and lithology of channel deposits were compared with those of the nearby floodplain deposits in the same catchment. Four river-channel facies were defined, ranging from sandy gravels to clayey silts, and confronted with the floodplain sediments. Al/Si ratios were found to be useful proxies of grain size, and Al was utilized as an excellent normalizing element for heavy metals, which filters out much of the grain size effects on contamination. The floodplain deposits are significantly less contaminated than their river-channel counterparts. Heavy-metal contamination of river bed sediments (expressed as enrichment factors, EFs) is not simply bound to fine-grained particles, and much of the contamination was found in coarse-grained, sandy facies. Elevated EFs of Zn, Cu and Pb in several sediment layers, which show high magnetic susceptibility (MS), high values of MS normalized to Fe and a high proportion of magnetic fly-ash spherules and their chemistry suggest that significant part of the heavy-metal contamination can be carried by magnetic fly-ash spherules. A part of this contamination is bound to coarse-grained fluvial facies, indicating that the magnetic spherules can be transported as bed load sediments. Magnetic pollution and heavy-metal pollution can therefore coincide in river bed deposits. It is suggested that most of this contamination can be related to local point sources of pollutants (fly-ash deposit spills).     

Soil‐ecological evaluation of willows in a floodplain

Willows (Salix spp.) were supposed to be suitable candidates for the phytoremediation of polluted floodplain soils, but it is unknown how willow growth alters concentrations and mobility of pollutants under the conditions of ongoing periodically flooding. Therefore, effects of willow cropping on total concentrations and mobility of As and heavy metals and soil microbial properties were determined after three and four growing seasons under willows in comparison to native grassland in a flood channel of a River Elbe floodplain (Central Germany). After 4 y of willow coppice, the heavy metal concentrations (mg kg^–1) were increased not only in the grass control plots (final Cu 274, Pb 276, Zn 935) but also under the willows (final Cu 248, Pb 251, Zn 779) compared to the initial concentrations (initial Cu 170, Pb 156, Zn 579). This increase might likely be caused by the ongoing sedimentation by flood events. The smaller increase under willows compared to grass might be related to an initial net effect of phytoextraction. The concentrations of the mobile fractions of Cd, Cu, Ni, and Zn were significantly lower under willows than under grass. Higher β‐glucosidase activities under willows than under grass might indicate a starting net decomposition of organic matter. Therefore, the study of long‐term and large‐scale effects are recommend before an appropriate evaluation of willow short‐rotation coppice for phytoremediation of polluted floodplains will be established.     

The Impact of Bioturbation by Small Mammals on Heavy Metal Redistribution in an Embanked Floodplain of the River Rhine

Floodplains along large European rivers are diffusely polluted with heavy metals due to emissions in the past. Because of low mobility of heavy metals in floodplain soils and improvements of water quality, these pollutants will remain in place, and can gradually become covered with less contaminated sediments. Bioturbators, especially earthworms, can play an important role in the mixing and surfacing of contaminated substrate. Surfaced substrate can be redistributed by recurrent flooding events, even to areas outside the floodplain. The question remained to what extent bioturbation by small mammals contributes to the redistribution of heavy metals from river sediments in floodplains. Extensive fieldwork on bioturbators such as voles, moles and earthworms and their distribution patterns, as well as on sediment deposition and bioturbation, was conducted at the ‘Afferdensche en Deestsche Waarden’ floodplain over the years 2001–2003. Field data were combined with data of experiments in field enclosures and substrate columns to calculate the amounts of sediment and heavy metals (Zn, Cu, Pb and Cd) redistributed during the floods as well as on an annual basis. Moles and voles surfaced considerable amounts of substrate and heavy metals, but not as much as earthworms which contribute a substantial proportion of the total deposition and redistribution during floods. Although the impact of moles and voles on the redistribution during floods was only locally important, on an annual basis the bioturbation activity of especially moles in floodplains cannot be neglected. The annual amounts of substrate and heavy metals surfaced by all investigated bioturbators were even larger than the total amounts of substrate and heavy metals deposited during floods.     

大沽河湿地表层沉积物重金属分布特征及污染评价

胶州湾属半封闭海湾,水体交换能力较弱,受多条河流入海影响,污染日趋加重,通过大沽河的径流量、输沙量和溶解污染物占到胶州湾入海河流的首位。根据区域特征,于2009年2、5、8、11月对大沽河湿地48个采样点表层沉积物中的Cu、Zn、Pb、Cd、Hg、As、有机碳、粒度进行测定,探讨了重金属含量和污染特征与总有机碳、粒度的关系,利用污染评价法和潜在生态风险评价法进行污染和风险分析。结果表明：胶州湾大沽河湿地表层沉积物重金属含量较低,大部分测站符合海洋沉积物质量（GB 18668—2002）Ⅰ类标准的要求。表层沉积物中Cu、Pb、Zn含量8月份最高、2月份次之、5月份最低。Pb、Hg、As 3种重金属含量在2月份最高。Cu、Pb、Zn和Cd重金属之间存在显著正相关关系,Hg与As存在明显的相关关系;除Cd和As外的4种重金属与沉积物粘土、有机碳含量之间也存在显著正相关性。重金属单因子污染程度总体较轻,属于低污染水平,污染程度依次为Hg〉Cd〉Pb〉Cu〉As〉Zn。大沽河河口区表层沉积物重金属潜在生态风险总体处于较低水平,风险程度依次为Hg〉Cd〉Pb〉Cu〉As〉Zn。     

Dispersal of Contaminant Metals in the Mining-Affected Danube and Maritsa Drainage Basins, Bulgaria, Eastern Europe

Metal dispersal in the Danube and Maritsa drainage basins resulting from metal mining activities in Bulgaria has been assessed through the collection of 611 samples of river water, river channel and floodplain sediment, and mine waste from over 218 sites. Concentrations of Cd, Cu, Pb, and Zn in river water were found to be highest in close proximity to locations of Cu and Pb–Zn mining regions in the Maritsa catchment. Downstream dispersal of solute metals in these catchments, and into the River Danube, was found to be limited by physical dilution and a well-buffered pH environment. Dispersal of contaminant metals in channel and floodplain sediment was found to be extensive. Contamination was particularly severe in the Rivers Timok and Iskar (Danube catchment) and the Topolnitsa, Chepelarska, and Arda Rivers (Maritsa catchment) and creates the potential of transboundary dispersal of contaminant metals.     

Contamination history of suspended river sediments accumulated in oxbow lakes over the last 25 years

Background, aims, and scope  Embankment of meandering river systems in many industrial areas results in the formation of artificial oxbow lakes that may act as perennial or intermittent traps for river sediments. Their deposits can be dated using a combination of historical and stratigraphic data, providing a good means to study historical records of contamination transported by rivers. Contamination history over the last few decades is of special significance for Central and Eastern Europe as it can reflect high pollutant levels in the second half of the twentieth century and the subsequent improvement after the fall of the Iron Curtain. The purpose of this study was to investigate recent sediments of an oxbow lake of the Morava River, Czech Republic, their stratigraphic records, sediment architecture, and history of contamination. Materials and methods  Seven ground-penetrating radar (GPR) profiles and three sediment cores up to 4 m deep were studied. The stratigraphy of the cores was inferred from visible-light spectrophotometry, X-ray radiography, grain size analysis, and semiquantitative modal analysis of sandy fractions. The sediments were dated using the ¹³⁷Cs mass activity and combinations of stratigraphic and historical data. The cores were sampled for concentrations of heavy metals and persistent organic pollutants. Wet sampled, lyophilized, and sieved sediments were extracted and analyzed for heavy metals by inductively coupled plasma mass spectrometry (ICP-MS) of aqua regia leachate and for persistent organic pollutants by gas chromatography (GC-ECD and GC-MS). Results  Three distinct sedimentary sequences (S1, S2, and S3) were identified. The basal sequence S1 represents river channel sediments deposited before the formation of the oxbow lake, most likely before the 1930s. The boundary between the S1 and S2 sequence correlates with the level of sediment dredging from 1981 evidenced from historical data. The overlying sequences S2 and S3 represent a postdredging sediment wedge, which progrades into the lake. ¹³⁷Cs dating revealed a distinct Chernobyl 1986 peak at ∼150 cm depth inferring sedimentation rates up to 7.7 cm/year. Sediment contamination abruptly increased from the pre-1930s deposits to the post-1981 deposits. The concentration levels increased two to five times for Pb, As, Zn, and Cu, about 10 to 15 times for Cr, Sb, and Hg, up to 34 times for Cd, and 25 to 67 times for DDTs, PCBs, and PAHs. The concentrations of most contaminants remained approximately constant until the late 1980s when they started to decrease slowly. The decreasing trends were most prominent for heavy metals and anthracene, less prominent for DDTs, and almost absent for PCBs and most PAHs. Discussion  Different temporal and spatial patterns for various contaminants make it possible to distinguish between anthropogenic point sources from local industry (anthracene, Cr, Cd), possible diffuse sources (most PAHs), and geological background (V, Co, Ni, and Mo). The observed recent trends in heavy metal and persistent organic pollutant contamination are generally consistent with data from other Central European rivers. The roughly balanced contamination levels in sediments from the lake and the adjacent river channel suggest that the oxbow lake deposits reflect immediate levels of the contamination bound to suspended particulate matter passing through the river. Conclusions  The investigated oxbow lake accumulated suspended sediment from Morava River, developing a thick sedimentary body. The sediments offer a good time framework to study historical contamination of the river on a decade time scale. Continuous contamination trends can be traced back to the early 1980s. The results show that stratigraphic analysis of cores has a good potential for identification of uninterrupted historical trends and unconformities, e.g., due to dredging. Recommendations and perspectives  Oxbow lakes may provide an alternative to floodplains and reservoir deposits when studying river contamination history. High sedimentation rates of up to 7.7 cm/year offer a very good stratigraphic resolution, making it possible to study contamination patterns on annual or even seasonal time scales. On the other hand, oxbow lakes may represent long-term contamination stores, which are unlikely to be redistributed by river erosion and, hence, may possess significant environmental risks for the farther future.     

沈阳地区河流灌渠沿岸农田表层土壤中重金属的污染现状评价

用地积累指数法和单因子内梅罗综合指数法研究了沈阳地区蒲河、浑河、细河以及沈抚灌渠周边农田表层土壤中7种重金属的污染状况。结果表明,表层土壤中As、Hg、Cd、Pb和Cr的最大值出现在细河周边,Zn和Cu的最大值出现在沈抚灌渠周边,Hg、Cd、Pb、Zn、Cu、Cr6种重金属的平均含量在各个区域中差别明显。Cd与Hg之间的相关系数高,表明Cd、Hg来源相同;Pb、Zn、As、Cu相关性好,判定可能来自同一来源。地积累指数和单因子内梅罗综合指数计算结果表明,Cd、Hg、Zn污染在这些河流地区较普遍,Pb、Cu、Cr和As在部分地区受到污染,部分细河沿岸农田土壤受到严重污染。     

Potential hotspots of persistent organic pollutants in alluvial sediments of the meandering Wurm River,Germany

Purpose

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 methods

The 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 discussion

High 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.

Conclusions

Results 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.

     

Distinguishing regional and local sources of pollution by trace metals and magnetic particles in fluvial sediments of the Morava River, Czech Republic

Purpose

Regional contamination of southern Moravia (SE part of the Czech Republic) by trace metals and magnetic particles during the twentieth century was quantified in fluvial sediments of the Morava River. The influence of local pollution sources on regional contamination of the river sediments and the effect of sampling site heterogeneity were studied in sediment profiles with different lithologies.

Materials and methods

Hundreds of sediment samples were obtained from regulated channel banks and naturally inundated floodplains and proxy elemental analyses were carried out by energy dispersive X-ray fluorescence spectroscopy (ED XRF) and further calibrated by inductively coupled plasma mass spectrometry (ICP MS). Magnetic susceptibility was determined as a proxy for industrial contamination. The age model for the floodplain sediments was established from ¹³⁷Cs and ²¹⁰Pb dating. Trace metal contamination was assessed by establishing the lithological background values from floodplain profiles and calculating enrichment factors (EF) of trace metals (i.e. Pb, Zn, Cu) and magnetic susceptibility for the entire study area.

Results and discussion

Channel sediments are unsuitable for the reconstruction of historical regional contamination due to their lithological heterogeneity and the “chaotic” influence of local sources of contamination, as well as the possibility of geochemical mobility of pollutants. On the other hand, sediments from regulated river banks qualitatively reflected the actual, local contamination of the river system.

Conclusions

This approach allowed us to distinguish the influence of local sources of contamination by comparison with more spatially averaged contamination signals from distal floodplain profiles. The studied area is weakly contaminated (EF ～1–2), while individual sediment strata from regulated channel banks reflect local sources of contamination and contain up to several times higher concentrations of trace metals.     

Redistribution of organic pollutants in river sediments and alluvial soils related to major floods

Background, Aims, and Scope  More frequent occurrence of stronger floods in Europe as well as in other parts of the world in recent years raises major concern about the material damages, but also an important issue of contamination of the affected areas through flooding. The effects of major floods on levels and distribution of contamination with hydrophobic organic pollutants were examined from the continuous set of data for floodplain soils and sediments from a model industrial area in the Czech Republic where a 100-year flood occurred in 1997. The goal of this study was to evaluate the risk related to contamination associated with such extensive natural events and characterize the spatial and temporal distribution and dynamics of pollutants related to a major flooding shortly after the floods and also in the time period several years after floods. Methods  Sediments and alluvial soils from fourteen sites each were repeatedly sampled during the period from 1996 until 2005. The sampling sites represented five regions. Collected top-layer sediment and soil samples were characterized and analyzed for hydrophobic organic pollutants PCBs, OCPs and HCB using GC-ECD and PAHs using a GC-MS instrument. Spatial and temporal differences as well as the relative distribution of the pollutants were examined in detail by statistical analysis including multivariate methods with special emphases placed on the changes related to floods. Results  The organic pollutants levels in both alluvial soils and sediments exceeded the safe environmental limits at numerous sites. Pollutants concentrations and relative distribution as well as organic carbon content in both sediment and floodplain soils were significantly affected by the flooding, which resulted in a decrease of all studied contaminants in sediments and significant rise of the PAH pollution in the flooded soils. There was a unique and highly conserved PAH pattern in soils regardless of the floods and greater changes in PAH pattern in sediments related to floods. The relative distribution of individual PAHs reflected a combustion generated PAH profile. PAH levels in the river sediments rose again at the sites with continuous sources several years after floods. Discussion  The results showed different dynamics of PAHs and PCBs during the floods when PAHs were redistributed from the sediments to alluvial soils while PCBs have been washed out of the study regions. The data reveal longer contamination memory and consistent contamination pattern in soils, whereas sediments showed more dynamic changes responding strongly to the actual situation. The stable PAH pattern within the regions also indicates that a relative amount of all compounds is comparable across the samples and, thus, that the sources at different sites have similar character. Conclusions  Sediments have the potential to function as a secondary source of contamination for the aquatic ecosystem, but also for the floodplain soils and other flooded areas. The floods served as a vector of PAHs contamination from sediments to soils. The reloading of river sediments in time, namely with PAHs, due to present sources increases their risk as a potential source in the next bigger flood event both to the downstream river basin and affected alluvial soils. Recommendations and Perspectives  The results stress the importance of including the floodplain soil contamination in the risk assessment focused on flood effects. Floodplain soils have stable long-term environmental memory related to contamination levels, pattern and distribution, whereby they can provide relevant information on the overall contamination of the area. The sediments will continue to serve as a potential source of contaminants and alluvial soils as the catchment media reflecting the major flood events, especially until effective measures are taken to limit contamination sources. ESS-Submission Editor: Dr. Henner Hollert (Hollert@uni-heidelberg.de) This article is openly accessible!     

Heavy metal and PCB spatial distribution pattern in sediments within an urban catchment—contribution of historical pollution sources

Purpose

This work analyzes polychlorinated biphenyl (PCB) and heavy metal contamination in fluvial sediments and soils in an urban catchment, according to the geo-accumulation index and to soil and sediment quality guidelines. The catchment is located in Coimbra, Portugal, being affected by frequent flooding, and its main stream is a tributary to one of the major rivers in Portugal (Mondego). Given the presence of industrial activities over time, some inputs of pollutants are expected, but so far, the legacy of historic pollution in this catchment has not yet been investigated.

Materials and methods

Twenty-five samples were collected from nine sampling sites at the depths of 0–20, 20–40 and 40–60 cm (to provide a historic perspective) along longitudinal profiles (streamlines) and in soils downstream of pollution sources. These samples were analyzed for six heavy metals (Cu, Cr, Pb, Cd, Zn, Ni), organic carbon, pH and ten PCBs (IUPAC numbers 28, 30, 52, 101, 138, 153, 166, 180, 204, 209).

Results and discussion

Total PCB concentrations ranged 0.47–5.3 ng g^?1 dry weight (dw), and levels increase from the bottom to the top layers, suggesting an increased input over the last 100 years. PCB congener distribution shows the dominance of hexachlorobiphenyls, especially PCB138, suggesting the existence of local sources. PCB levels did not exceed sediment quality levels, placing sediments/soil under class 1 (not contaminated) or class 2 (trace contamination) with respect to PCB. All six metals exceeded the lowest effect level for sediment quality criteria, and three (Cd, Pb and Zn) largely exceeded the clean levels for dredged materials, placing sediments in class 5 (heavily contaminated). Sampling site S1 presented the highest concentrations of Zn, Pb and Cd, and historic vehicle traffic was identified as the most likely source, given the vertical and horizontal profiles.

Conclusions

High levels of Pb, Cd and Zn were found in fluvial sediments at some locations of the Loreto catchment, likely from historic traffic sources. This urban area is frequently affected by flooding events and is currently being subject to urban redevelopment. During these events/actions, historic pollutants in the sediments might surface and be redistributed, impacting the downstream ecosystem of the major Mondego River or increasing the risk of exposure of the urban population.

     

中国太原市农业土壤的重金属污染状况

To evaluate the current state of the environmental quality of agricultural soils in Taiyuan City, a hotspot for China’s industrial development, the concentrations of 8 heavy metals in soils were investigated by means of extensive sampling in farmlands, forestlands, and grasslands in the city. Statistical analyses and spatial distribution maps were used to identify the most significant heavy metal pollutants. The mean concentrations of As, Cd, Cu, Hg, Pb, Zn, Ni, and Cr were slightly higher than their background values in Taiyuan’s topsoil, but were lower than the maximum permissible concentrations in the Chinese Environmental Quality Standard for agricultural soils. Farmland soils in Taiyuan had the highest average Cd, Cu, Hg, Pb, Zn, and Cr concentrations, but the As and Ni concentrations did not differ significantly among the farmland, forestland, and grasslands. Soil contamination by Cd, Cu, Hg, Pb, Zn, and Cr was mainly derived from farming practices, especially the use of sewage water for irrigation. In contrast, As and Ni might derive mainly from the soil parent material. The identification of heavy metal sources in agricultural soils may provide a basis for taking appropriate action to protect soil quality.     

Heavy metal contamination of soils in Northern Slovakia

Environmental damages like forest decline in Northern Slovakia could be a result of long-distance transport of pollutants with the dominating north-west winds. On 10 sites, primarily in the northbound upper slopes of west-east oriented mountain ranges in Northern Slovakia, the extent of the heavy metal contamination in soils along a north-south transect was examined. Oi, Oe, Oa, A, and B horizons were sampled and the total concentrations of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined. The ranges of heavy metal concentrations in the forest floor were higher than reported for comparable samples from Bavarian soils except for Zn (Cd: 0.65–1.77; Cr: 12–40; Cu: 19–41; Ni: 8–24; Pb: 70–187; Zn: 31–92 mg kg^?1), in the mineral soil the concentrations were lower. The depth distribution of the metal concentrations indicated a contamination with Cd, Cr, Cu, Ni, Pb, and Zn. The concentration differences between forest floor and mineral soil tended to be higher at the northern than at the southern sites for Cu, Ni, Pb, and Zn, indicating a long-distance transport from the north. Correlation and principal component analyses of the total metal concentrations revealed three groups: Cu, Pb, and Zn inputs mainly seemed to result from long-distance transport from the north, Cr and Ni inputs additionally from local sources. Cd probably had its origin mainly in local sources. This result was further confirmed by the grouping of the sites when clustered.     

Effects of acidification on the concentrations of heavy metals in running waters in Sweden

Heavy metals in running water are analysed within the Swedish Surface Water Monitoring Programme at about 80 stations. Data for selected rivers and brooks has been used to assess the effect of soil acidification on the concentrations of metals in waters. In southern Sweden, acidification shows a significant effect on Zn and Cd. In the upper parts of the drainage areas, there is an marked increased leakage of these metals from soils to waters indicated by elevated concentrations of Zn and Cd in brooks and also by high maxima during periods of low pH values. The increased leaching from forest soils also influences the concentrations in rivers in southern Sweden. During periods of high water flow, the pH values of the rivers decreases and the concentrations of Zn and Cd increases. At pH levels of 6.2–6.5 the concentrations of these metals are mostly 2–5 times higher as compared to pH levels of about 7.0. Since high concentrations of Zn and Cd coincides with high water flow, the transport of these metals has most certainly increased several times compared to the pre-industrial period. Hence, the by far most important human impact on the loading of Zn and Cd on the marine areas, surrounding southern Sweden is the increased leakage of these metals due to acidification. In northern Sweden the effects of acidification on Zn and Cd are less evident. In general, the concentrations of these metals are lower and the connection between pH and these metals are much less significant in the rivers. The links between acidification and the concentrations of Pb and Cu in the watercourses are comparatively much weaker. These two metals are more related to the content of organic matter in the waters and a possible effect of acidification is overshadowed by natural transport processes in soils and waters.     

Contamination of Urban Soils in an Area of Northern France Polluted by Dust Emissions of Two Smelters

The contamination of 27 urban topsoils has been assessed around two lead and zinc smelters (Metaleurop Nord and Umicore) in the North of France. Eighteen trace elements have been analysed (Ag, As, Bi, Cd, Co, Cr, Cu, Hg, In, Ni, Pb, Sb, Se, Sn, Tl, Th, U and Zn). The investigation included the study of the vertical distribution of Cd, Pb and Zn as indicators of pollution. It was shown that Cd, In, Pb, Sb and Zn were major pollutants followed in lesser quantities by Ag, Bi, Cu and Hg. In addition, As, Ni, Se, Sn and Tl were present at levels slightly higher than regional agricultural values. The other elements (Co, Cr, Th and U) were at endogenous levels. The observations have highlighted the strong heterogeneity of the physico-chemical parameters of urban soils and the existence of heavy contamination of the under layers by Cd, Pb and Zn. A potential transfer of metals from the topsoil to the deeper layers and especially Cd and Zn, is not excluded. Indeed the soil rework is not the only factor explaining contamination level of the deeper layers of the studied soils. The comparison of the studied element concentrations in urban soils with nearby local agricultural values shows that the dust emission originating from the Metaleurop and Umicore smelters were not the only source of contamination. Thus a large contamination of the studied urban soils by Sb and In could be explained by domestic combustion of coal for heating.     

Potentially toxic elements in the riparian soils of the Sava River

Purpose

Riparian zone contamination is a growing problem for several European catchments due to high anthropogenic pressures. This study investigates As, Cd, Cr, Cu, Ni, Pb, and Zn concentrations in the Sava River riparian zone, characterized by wide agricultural areas, various geological substrates, and different types of industrial pollution. The accumulation and mobility of these elements were studied because they are listed as priority substances in the Water Framework Directive and environmental objectives for surface waters.

Materials and methods

Sampling was performed during the sampling campaign of the EU 7th FW-funded GLOBAQUA project in September 2015 during a low-water event. Soil samples were collected along the Sava River at 12 selected sampling sites, from a depth of 0–30 cm, at a distance of 10–15 m from the river bank. The extent of pollution was estimated by determining total and readily soluble element concentrations in the soils. Potential ecological risk and the source of the selected elements in the soils was determined using the enrichment factor (EF), potential ecological risk index (RI), and statistical methods such as the principal component analysis (PCA) and multiple linear regression analysis (MLRA).

Results and discussion

This study showed that concentrations of the selected elements increase along the Sava. In terms of origin, PCA and MLRA indicated that Cr and Ni in soils are predominantly lithogenic, while As, Cd, Pb, and Zn are both lithogenic and anthropogenic (ore deposits, industry, and agriculture). PCA singled out Cu since its origin in soil is most probably from specific point-source pollution. EF was generally minor to moderate for most of the examined elements, apart from Cu, for which the EF was significant at one sampling site. Overall ecological risk (RI) fell within the low-risk category for most sites, apart from Belgrade sampling site (BEO), where high total Cd content affected individual and overall ecological risk indicators, indicating Cd could represent a considerable ecological risk for the downstream riparian zone.

Conclusions

At downstream sites, there was a noticeable increase in PTE content, with Cd, Cr, Ni, and Zn exceeding the proposed threshold values for European soils, indicating rising contamination in riparian soils. In terms of the ecological risk, only Cd could pose a potential ecological threat for the downstream riparian zone.

     

Mining Impacts on Trace Metal Content of Water,Soil, and Stream Sediments in the Hei River Basin,China

The impacts of mining to watersheds are highly variabledepending on the type of mining, processing of ores, andenvironmental factors. This study examined the Hei River incentral China, for impacts of gold and iron mining onconcentrations of metals in river water, river sediments andstream-channel soils. No production processing of ores occurson-site at either mine. Total metal content and extractablemetals using DTPA were determined. Total concentrations of Cd,Cu, Pb and Zn were high in some stream sediments and soils nearthe mine sites; metal concentrations ranged from 4–24, 11–100,11–380, and 33–1600 μg g^-1 for Cd, Cu, Pb, and Zn,respectively, in soil. Total cadmium was high in all soilsand sediments. Extractable metals were low, with the exceptionof Pb and Cu. At the gold mine, extractable Pb ranged from 8 to33%; extractable Cu ranged from 3 to 21% of total metalconcentration. Chromium and Ni were not above typicalconcentrations in either soils or river sediments. An abundance of carbonates, high river water pH, and high water flow rates all appear to contribute to limiting quantities of metals in the river water. If mining activities are not changed, impacts of mining on downstream metal concentrations in river water should be nominal.