contaminated sediment
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Author(s):  
Erlend Sørmo ◽  
Ludovica Silvani ◽  
Hans Fredrik Veiteberg Braaten ◽  
Tina Bryntesen ◽  
Espen Eek ◽  
...  

Abstract Purpose As the formation of toxic and bioaccumulative methylmercury (MeHg) in Hg-contaminated sediments is of great concern worldwide, suitable remediation options are needed. Activated carbon (AC) amendment is a contested alternative due to uncertainties surrounding sorption efficiency and its potential role in aiding MeHg formation. The purpose of this study was therefore to demonstrate AC performance under favourable conditions for Hg-methylation and to further understand the role AC plays in the methylation process. Materials and methods Mercury-contaminated sediment (57.1 mg kg−1) was sampled from the Gunneklev fjord, a site known as the most heavily contaminated fjord in Norway. In a laboratory experiment, lignite AC (A-AC, 5%) or activated biochar (A-BC, 5%) along with dried algae biomass, serving as an excess source of easily degradable organic matter (OM) and sulphate, were added to sediment samples that were kept anoxic and dark over a period of 12 months. Results and discussion The amount of MeHg in sediment and porewater of the amended samples were measured at 0, 1, 3, 6, and 12 months and compared to an unamended control. A net increase of MeHg in the sediment was observed in both control and amended samples, but contrary to expectations, sediment MeHg was 5 and 3 times higher in the A-AC and A-BC treatments, respectively, relative to the control after 12 months. As the stimulation of Hg-methylation could not be attributed to the sorbents supplying more available OM or sulphate for dissimilatory sulphate reduction, it is speculated that the sorbents rather aid this process through shuttling of electrons between the substrates involved. Meanwhile, the A-AC and A-BC amendments strongly reduced the available MeHg-concentration in porewater (by 87% for A-AC and by 93% for A-BC after 12 months), confirming that AC sorbents can be used to effectively limit the transport of MeHg from sediments. Conclusion When considering remediation of OM-rich Hg-contaminated sediments with AC, caution is thus warranted, as the overall effect of reducing MeHg-transport out of the sediment could partly be offset by an increased fraction of MeHg in the sediment. Thin-layer capping with AC might therefore be preferable to complete mixing of AC and sediment.


Author(s):  
Anna Norén ◽  
Célia Lointier ◽  
Oskar Modin ◽  
Ann-Margret Strömvall ◽  
Sebastien Rauch ◽  
...  

AbstractMetal and tributyltin (TBT) contaminated sediments are problematic for sediment managers and the environment. This study is the first to compare Fenton’s reagent and electrochemical treatment as remediation methods for the removal of TBT and metals using laboratory-scale experiments on contaminated dredged sediment. The costs and the applicability of the developed methods were also compared and discussed. Both methods removed > 98% TBT from TBT-spiked sediment samples, while Fenton’s reagent removed 64% of the TBT and electrolysis 58% of the TBT from non-spiked samples. TBT in water phase was effectively degraded in both experiments on spiked water and in leachates during the treatment of the sediment. Positive correlations were observed between TBT removal and the added amount of hydrogen peroxide and current density. Both methods removed metals from the sediment, but Fenton’s reagent was identified as the most potent option for effective removal of both metals and TBT, especially from highly metal-contaminated sediment. However, due to risks associated with the required chemicals and low pH level in the sediment residue following the Fenton treatment, electrochemical treatment could be a more sustainable option for treating larger quantities of contaminated sediment.


Chemosphere ◽  
2022 ◽  
Vol 287 ◽  
pp. 132363
Author(s):  
Wenjing Xue ◽  
Shan Cao ◽  
Jing Zhu ◽  
Wanyao Li ◽  
Jun Li ◽  
...  

Water ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 62
Author(s):  
Elena Alekseenko ◽  
Bernard Roux ◽  
Konstantin Kuznetsov

The present study concerns the erosion and transport of severely contaminated sediments in a Canal. It begins in the context of an engineering project aimed to re-introduce a forced convection at the entrance of this Canal by pumping marine water. The local wind is often strong enough to overpass the resuspension threshold; thus, there is a serious risk of downstream contamination of a Mediterranean lagoon. So, the goal is to evaluate this risk as a function of the pumping rate; this contamination is transported by the fine suspended particles. Different scenarios are investigated to determine the downstream transport of suspensions in terms of runoff. These scenarios (of 24 h) contains a succession of 3 periods: constant wind speed, wind slowdown and calm, for two opposite wind directions. Special attention is devoted to the modeling of complex mechanisms of erosion and resuspension during wind periods, deposition during windless periods and sediment consolidation. The main results concern the total flux of the suspended particles through the exit of the Canal at the confluence with the lagoon. It is shown that even for moderate runoff (<6 m3/s) this total flux is large enough, not only during the wind period, but also after several hours of calm.


2021 ◽  
Vol 9 (2) ◽  
Author(s):  
Vlasta Dudková ◽  
Kateřina Demnerová ◽  
Donna L. Bedard

Polychlorinated biphenyls (PCBs) are organic xenobiotics contaminating environment for at least 50 years. They could be eventually eliminated by various organisms under different conditions. The degree of chlorine substitution per biphenyl molecule influences biodegradability which decreases with increasing chlorination. Our work is focused on the PCBs biodegradation under anaerobic conditions. The suitable high chlorinated biphenyls are converted via reductive dechlorination to the chlorinated biphenyls with lower extent of chlorine, which could be eventually fully mineralized by aerobic bacteria. Microbial consortium was isolated from sediment of Strážský Creek (located near by plant producing PCBs in the past). This consortium was able to dechlorinate polychlorinated biphenyls under anoxic conditions. The effectiveness of this process was tested under different cultivation condition – different energetic sources (Aroclor 1248 or Aroclor 1260 or Delor 103 or Delor 106), addition of potential electron donors (pyruvate, lactate or acetate with hydrogen) and further if there is necessary to add yeast extract into fresh low sulphur cultivation media. Our microbial consortia so far do not need supplementation by non-contaminated sediment to maintain dechlorination activity. Addition of yeast extract is non essential, but needs to be further proved in serial transfers. In all cases (except acetate without yeast extract) dechlorination proceeds at meta- and flanked paraposition.


Author(s):  
David Glaser ◽  
Kevin Russell ◽  
James Rhea ◽  
Wen Ku ◽  
Deirdre Reidy ◽  
...  

2021 ◽  
Author(s):  
Yunfei Li

With the rapid development of industry, large amounts of untreated industrial waste water and domestic sewage carried heavy metal pollutants below into the water body with enrichment in sediments. When environmental conditions change, enrichment of heavy metals in sludge may be released into the overlying water causing the overlying water quality standard. The agent on immobilization of heavy metals in sludge is to be an extremely promising remediation technology in order to reduce impact on the environment. This test selects Hydroxyapatite and Nano Hydroxyapatite as curing agent and puts it into heavy metal pollution by different proportion. The paper conducts the research of curing agent and optimizes the better one. The paper selected HAP as matrix and CaO and MgO as different additives and studied complex condition of heavy metals in sediment of curing effect. Also the paper conduct the static releases test for pollutants in cured sediment in order to provide technical support for contaminated sediment remediation of heavy metal.


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