Dredged Sediment Disposal Sites Research Articles

Fraction distribution and leaching behavior of heavy metals in dredged sediment disposal sites around Meiliang Bay, Lake Taihu (China).

The objectives of this study were to characterize the heavy metal contamination status of surface soils sampled at two dredged sediment land disposal sites (the Baimao and Kongwan landfills) in Meiliang Bay, Lake Taihu, China, as well as to investigate the effect on their leaching behaviors due to acid rain. Among all the metals, only the nickel content in the Baimao landfill was higher than the Chinese reference value, and all metal contents were below the limit values for agricultural soils. The fraction distribution of metals by sequential extraction was similar at both sites. Cadmium had a relatively high proportion of exchangeable-carbonate fractions, while the other metals were mainly classified as residue fractions. The metals released from soils by simulated rainwater comprised less than 1% of the total soil metal content, and the effect of acid rain on heavy metal release from dredged sediments in land disposal sites was found to be negligible at both sites. All results indicate no environmental concern for the land disposal of dredged sediments and support the feasibility of beneficially reusing dredged sediment soils as a supplement to agricultural soils.

镉胁迫下杞柳对金属元素的吸收及其根系形态构型特征

采用水培方法,研究了杞柳(<em>Salix integra</em>)2个品种在0-90 μmol/L Cd处理下不同组织对Cd的吸收和积累规律,探讨了镉胁迫下杞柳根系形态学功能响应特征以及对矿质离子吸收的影响。结果发现,镉在杞柳2个品种不同组织的含量均表现为根>韧皮部>木质部>叶。2个品种地上部组织对镉的吸收和积累规律相似:在0-70 μmol/L Cd处理浓度范围内,随着溶液Cd浓度的增加,叶、木质部、韧皮部中镉的含量逐渐增加,到50 μmol/L时,镉在地上部组织的含量达到最高,当Cd处理浓度达90 μmol/L时,地上部各组织中Cd含量出现下降趋势。而2个品种根系对Cd的吸收则不同,"微山湖"品种在溶液Cd达70 μmol/L时,根系镉的积累量最大,在90 μmol/L时,根系Cd的积累量明显下降;"一枝笔"品种根系在0-90 μmol/L范围内,根系Cd的积累量均为增加趋势。通过分析2个品种根系形态学参数变化发现,Cd胁迫抑制了杞柳2个品种根的伸长,促进了"微山湖"品种根的径向生长,导致根系平均直径增加;进一步对叶片矿质营养状态分析发现, Ca、Mn的吸收受镉胁迫的影响较大,在高浓度镉胁迫下(50-70 μmol/L)"微山湖"和"一枝笔"对Ca和Mn的吸收明显下降;Cd胁迫对Fe在叶片的含量影响不明显;同时发现,在50 μmol/L Cd处理下,Cu²⁺在叶片的积累明显增加。由此可见,杞柳2个品种间对镉的吸收和积累差异主要体现在根系,地上部对镉毒害的响应差异不大。;Willows (<em>Salix </em>spp.) are suitable for heavy metal phytoextraction due to their high element accumulation, high metal transport from roots to the shoots and high biomass production. Many species and hybrids of Salix spp. are known to colonise contaminated soils. For example, <em>S. alba</em>, <em>S. viminalis</em>,<em> S. cinerea</em> and <em>S. caprea</em> naturally invade polluted dredged sediment disposal sites. Therefore, there is an opportunity for genotype selection by checking survival, regeneration, and potentially also by testing metals accumulating in tissues which could then be harvested with remediating contaminated soils. Willow species and clones have different tolerance to particular metals, and significant differences were found for the uptake and accumulation of metals among willow varieties and clones. Soil contamination by cadmium due to human and natural activities is one of the most serious environmental problems in the world. The aim of this study is to investigate the cadmium uptake potential of two cultivated varieties (‘Weishanhu’ and ‘Yizhibi’) of <em>Salix integra</em>, of which the variety ‘Yizhibi’ has stronger tolerance to cadmium stress than ‘Weishanhu’ according to previous studies, and to discuss the possible mechanisms which involved in root adaptation under hydroponically cadmium treatment.<br>The results showed the highest content of cadmium was observed in root tissues for both varieties of <em>S. integra,</em> and the cadmium content in phloem tissues was lower than that in roots. The cadmium content in leaves showed the lowest level among roots, phloem and xylem. The cadmium content in the aboveground (including phloem, xylem and leaf) tissues of two varieties of <em>S.integra</em> increased significantly compared to the control with the increase of cadmium treatment in the range of 10-70 μmol/L, and it came to the highest cadmium accumulation at the concentration of 70 μmol/L cadmium, while when exposed to 90 μmol/L cadmium solution, the cadmium content declined in the aboveground parts. The same accumulation patterns were found in roots for two varieties of <em>S. integra</em> in the range of 10-70 μmol/L cadmium treatment. However, when the roots were exposed to 90 μmol/L cadmium treatment, the cadmium content in ‘Weishanhu’ declined sharply, but still rose for that in ‘Yizhibi’. This suggests the roots of ‘Yizhibi’ have greater potentential in uptake of cadmium than the variety ‘Weishanhu’ when exposed to higher concentration of cadmium. <br>The higher uptake and accumulate potential of ‘Yizhibi’ depends on the relatively unchangeable root morphology and fractal dimension under cadmium stress. Comparing to the root images of ‘Weishanhu’ and ‘Yizhibi’ under cadmium treatment, we found the total length, total surface area and volume of roots of ‘Yizhibi’ changed a little compared to the control, while that of ‘Weishanhu’ decreased under cadmium treatment. The fractal dimension of two varieties of <em>S. integra</em> had minor decline, which may suggest both ‘Weishanhu’ and ‘Yizhibi’ prefer to simple root configuration under cadmium treatment. We also found the nutrient uptake in leaves of two varieties of <em>S. integra</em> changed in different cadmium concentration. The Ca and Mn content in leaves decreased significantly in the concentration of 50 and 70 μmol/L cadmium, and no obvious change was observed for Fe content in leaves. It is interesting that the Cu content in leaves of ‘Weishanhu’ increased significantly in the concentration of 50 μmol/L cadmium.

Metal Contaminated Dredged Sediment Derived Soils: A Case Of Diffuse Contamination

Significant areas in Flanders, Belgium exhibit moderate contamination with trace metals caused by deposition or disposal of contaminated sediments. After disposal, the sediments develop into a soil-like material, on which vegetation is planted or develops spontaneously. Behaviour, cycling and ecosystem impacts of trace metals in calcareous dredged sediment disposal sites in Flanders was investigated. Although soil physico-chemical properties favour a low metal bioavailability, pore water concentrations can be elevated compared to pore water in uncontaminated soils. While metal leaching is not considered to be of concern, several plants accumulate elevated levels of Cd and Zn in leaves. Also metal levels in soil dwelling organisms and small mammals, particularly Cd, are elevated compared to reference situations. This raises concern for an enhanced transfer of metals to the food chain. A comprehensive knowledge of metal behaviour in these sites is essential for developing appropriate management options for these sites.

Cycling and ecosystem impact of metals in contaminated calcareous dredged sediment-derived soils (Flanders, Belgium)

Significant areas in Flanders, Belgium exhibit moderate contamination with trace metals caused by disposal of contaminated dredged sediments. After disposal, the sediments develop into a soil-like material, on which vegetation is planted or develops spontaneously. Behaviour, cycling and ecosystem impacts of trace metals in calcareous dredged sediment disposal sites in Flanders is reviewed. Although soil physico-chemical properties favour a low metal bioavailability, pore water concentrations can be elevated compared to pore water in uncontaminated soils. While metal leaching is not considered to be of concern, several plants accumulate elevated levels of Cd and Zn in leaves. Also metal levels in soil dwelling organisms and small mammals, particularly Cd, are elevated compared to reference situations. This raises concern for an enhanced transfer of metals to the food chain. Future research should identify biological effects on organisms caused by the contamination. A comprehensive knowledge of metal behaviour in these sites is essential for developing appropriate management options for these sites.

Short- and longer-term effects of the willow root system on metal extractability in contaminated dredged sediment.

Willow (Salix spp.) stands are often proposed as vegetation covers for the restoration and stabilization of contaminated and derelict land. Planting willows on dredged sediment disposal sites for biomass production can be an alternative to traditional capping techniques. However, with the introduction of willow stands on dredged sediment disposal sites, the possibility of increased contaminant availability in the root zone must be acknowledged as it can increase the risk of leaching. Two trials investigated the availability of Cd, Zn, Cu, and Pb in the root zones of willows grown on contaminated sediment. To assess the effects of willow root growth on metal extractability and mobility, bulk and rhizosphere sediment samples were extracted with deionized water, ammonium acetate at pH 7, and ammonium acetate-EDTA at pH 4.65. A rhizobox experiment was used to investigate the short-term effect of willow roots on metal availability in oxic and anoxic sediment. Longer-term effects were assessed in a field trial. The rhizobox trial showed that Cd, Zn, and Cu extractability in the rhizosphere increased while the opposite was observed for Pb. This was attributed to the increased willow-induced oxidation rate in the root zone as a result of aeration and evapotranspiration, which masked the direct chemical and biological influences of the willow roots. The field trial showed that Cu and Pb, but not Cd, were more available in the root zone after water and ammonium acetate (pH 7) extraction compared with the bulk sediment. Sediment in the root zone was better structured and aggregated and thus more permeable for downward water flows, causing leaching of a fraction of the metals and significantly lower total contents of Cd, Cu, and Pb. These findings indicate that a vegetation cover strategy to stabilize sediments can increase metal availability in the root zone and that potential metal losses to the environment should be considered.

Cadmium and Zinc uptake by volunteer willow species and elder rooting in polluted dredged sediment disposal sites

Salix species and Sambucus nigra L. (elder) naturally invade dredged sediment landfills and are commonly encountered on substrates contaminated with heavy metals. Foliar concentrations of Cd and Zn in four Salix species and elder were explored in the field. Metal contents in dredged sediment derived soils were elevated compared to baseline concentration levels reported for Flanders. To evaluate foliar concentrations, reference data were compiled from observations in nurseries, young plantations and unpolluted sites with volunteer willow vegetation. Willows grown on polluted dredged sediment landfills showed elevated foliar Cd and Zn concentrations (>6.6 mg Cd/kg DW and >700 mg Zn/kg DW). This was not the case for elder. For willow, a significant relation was found between soil total Zn or Cd and foliar Zn or Cd, regardless of age, species, or clone. Willows proved to be useful bioindicators. Results indicated a possible threat in long-term habitat development of willow brushwood from transfer of Cd and Zn to the food web.

Heavy Metal Transport from Dredged Sediment Derived Surface Soils in a Laboratory Rainfall Simulation Experiment

Heavy metals in dredged sedimentdisposal sites may be transported through runoff andpercolation. In the present study metal fluxes byrunoff and percolation were determined under simulatedrainfall at a slope of 19% and a rainfall intensityof approximately 40 mm h-1. These circumstancescorrespond to half the mean annual erosivity of rainunder Belgian weather conditions. Surface runoff andpercolating water samples were analysed for suspendedsolids, total dissolved carbon and Cd, Cr, Cu, Ni, Pb and Zn.Runoff rate and sediment yields were highest for asilt loam sediment, characterised by a low clay andorganic matter content. Metal concentrations in runoffand percolating water varied widely between thesediments studied and were related to the total metalcontent in the sediment. In runoff and percolatingwater from the contaminated sediments, metalconcentrations strongly exceeded the Netherlands Areference values for ground water quality. Very highmetal fluxes were observed for the recently oxidiseddredged sediment. Metal transport per unit surfacearea through percolating water was from two to morethan twenty times greater than that in surface runoff.

Leaching behaviour of Cd, Cu, Pb and Zn in surface soils derived from dredged sediments

Leaching of heavy metals from land-disposed dredged sediment spoils is a potential environmental hazard. The leaching behavior of Cd, Cu, Pb and Zn in surface soils sampled from abandoned dredged sediment disposal sites was assessed. Using simple mass-balance calculations, the significance of the leaching test results with respect to metal migration into underlying clean soil was appraised. The potential leachability, defined as the amounts released at constant pH 4, decreased in the order (% of total contents): Zn (58%)≈Cd (49%)>Cu (5%)≈Pb (2%). The kinetics of metal release were determined in a cascade shaking test using de-mineralized water acidified to pH 4 (HNO 3). Metal concentrations in the leachates were low and metal migration was, assuming uniform convective flow, predicted to be of no environmental concern. It is emphasized that any long-term prediction of metal migration is uncertain.

Heavy metal fractionation and extractability in dredged sediment derived surface soils

The objective of this study was to characterise pollution with heavy metals in surface soils sampled at various dredged sediment disposal sites in the Flemish region (Belgium). The sites selected varied in the period since sediment disposal ceased and in current vegetation and land use.

Temporal changes in the composition and abundance of the macro-benthic invertebrate communities at dredged material disposal sites in the anse à Beaufils, baie des Chaleurs, eastern Canada

Temporal changes in the composition and abundance of the macro-benthic invertebrate communities were studied at dredged sediment disposal sites located near L'Anse-à-Beaufils, baie des Chaleurs, Québec, Canada, in July and September 1994. A total of 5109 m 3, 2485 m 3 and 6002 m 3 of dredged material from L'Anse-à-Beaufils harbour were damped within the study area in 1992, 1993 and 1994, respectively. Pre-disposal collection of samples was conducted from 4 to 13 July 1994 at five stations located within the targeted dumpsite of 1994 as well as at five nearby control stations. Post-disposal sample collection was carried out from 5 to 16 September 1994. 15 days after the 1994 disposal activities ceased, at five stations in each of the 1994, 1993 and 1992 dumping areas (15 stations total) as well as at five stations in the control zone. The impact was estimated at the community level of the system, using both descriptive statistics and multivariate analytical methods. The surface sediment composition and the benthic community structure were changed drastically shortly after the open-sea deposition of dredged materials. The faunal response may be characterized as a decrease in the density of the less opportunistic families and a major increase in the density of families with the most opportunistic life-style. Both direct burial by dredged sediment discharged in large quantities within a short time interval and an enhanced food supply are the two factors that may explain the changes in density in various families. More than 2 years are required for the disturbed areas to re-establish a sediment composition and a macro-benthic community structure similar to undisturbed areas of the Anse à Beaufils sea bottom.

Temporal Changes in the Composition and Abundance of the Macro-benthic Invertebrate Communities at Dredged Material Disposal Sites in the Anse à Beaufils, Baie des Chaleurs, Eastern Canada

Temporal changes in the composition and abundance of the macro-benthic invertebrate communities were studied at dredged sediment disposal sites located near L'Anse-à-Beaufils, baie des Chaleurs, Québec, Canada, in July and September 1994. A total of 5109 m3, 2485 m3 and 6002 m3 of dredged material from L'Anse-à-Beaufils harbour were damped within the study area in 1992, 1993 and 1994, respectively. Pre-disposal collection of samples was conducted from 4 to 13 July 1994 at five stations located within the targeted dumpsite of 1994 as well as at five nearby control stations. Post-disposal sample collection was carried out from 5 to 16 September 1994. 15 days after the 1994 disposal activities ceased, at five stations in each of the 1994, 1993 and 1992 dumping areas (15 stations total) as well as at five stations in the control zone. The impact was estimated at the community level of the system, using both descriptive statistics and multivariate analytical methods. The surface sediment composition and the benthic community structure were changed drastically shortly after the open-sea deposition of dredged materials. The faunal response may be characterized as a decrease in the density of the less opportunistic families and a major increase in the density of families with the most opportunistic life-style. Both direct burial by dredged sediment discharged in large quantities within a short time interval and an enhanced food supply are the two factors that may explain the changes in density in various families. More than 2 years are required for the disturbed areas to re-establish a sediment composition and a macro-benthic community structure similar to undisturbed areas of the Anse à Beaufils sea bottom.

Solid-phase distribution of heavy metals as affected by single reagent extraction in dredged sediment derived surface soils

ABSTRACTEDTA is useful to assess mobile metal pools in polluted soils and sediments. There is a need to enhance our understanding of the significance of metal fractions released. The impact of single reagent extraction with 0.05 mol L−1 EDTA on the solid phase distribution of trace metals in surface soils sampled from confined dredged sediment disposal sites was investigated. Not extracted and EDTA extracted soils were subjected to sequential extraction to fractionate the total contents into: (1) easily exchangeable and carbonate bound fraction; (2) reducible fraction; (3) oxidisable fraction; and (4) residual fraction. With EDTA, significant portions of metals associated with the acid extractable and reducible fractions were released. The oxidisable and residual fractions remained unaffected for most of the investigated metals except for the organic matter associated metals (Cu and Pb). A decrease in the residual fraction after EDTA-extraction for Cu and Pb was attributed to artifacts of the sequential e...

Wave-Forced Resuspension of Upper Chesapeake Bay Muds

Moored instruments were used to make observations of near bottom currents, waves, temperature, salinity, and turbidity at shallow (3.5 m and 5.5 m depth) dredged sediment disposal sites in upper Chesapeake Bay during the winters of 1990 and 1991 to investigate time-varying characteristics of resuspension processes over extended periods. Resulting time series data show the variability of two components of the suspended sediment concentration field. Background suspended sediment concentrations varied inversely with salinity and in direct relation to Susquehanna River flow. Muddy bottom sediments were also resuspended locally by both tidal currents and wind-wave forcing, resulting in short-term increases and decreases in suspended concentration, with higher peak concentrations near the bottom. In both years, episodes of wave-forced resuspension dominated tidal resuspension on an individual event basis, exceeding most tidal resuspension peaks by a factor of 3 to 5. The winds that generated the waves responsible for the observed resuspension events were not optimal for wave generation, however. Application of a simple wind-wave model showed that much greater wave-forced resuspension than that observed might be generated under the proper conditions. The consolidated sediments investigated in 1990 were less susceptible to both tidal and wave-forced resuspension than the recently deposited sediments investigated in 1991. There was also some indication that wave-forced resuspension increased erodibility of the bottom sediments on a short-term basis. Wave-forced resuspension is implicated as an important part of sediment transport processes in much of Chesapeake Bay. Its role in deeper, narrower, and more tidally energetic estuaries is not as clear, and should be investigated on a case-by-case basis.