Review on utilization of biochar for metal-contaminated soil and sediment remediation

Biochar is a carbon-neutral or even carbon-negative material produced through thermal decomposition of plant-and animal-based biomass under oxygen-limited conditions.Recently, there has been an increasing interest in the application of biochar as an adsorbent, soil ameliorant and climate mitigation approach in many types of applications.Metal-contaminated soil remediation using biochar has been intensively investigated in small-scale and pilot-scale trials with obtained beneficial results and multifaceted effects.But so far, the study and application of biochar in contaminated sediment management has been very limited, and this is also a worldwide problem. Nonetheless, there is reason to believe that the same multiple benefits can also be realized with these sediments due to similar mechanisms for stabilizing contaminants. This paper provides a review on current biochar properties and its use as a sorbent/amendment for metal-contaminated soil/sediment remediation and its effect on plant growth, fauna habits as well as microorganism communities. In addition, the use of biochar as a potential strategy for contaminated sediment management is also discussed, especially as regards in-situ planning. Finally, we highlight the possibility of biochar application as an effective amendment and propose further research directions to ensure the safe and sustainable use of biochar as an amendment for remediation of contaminated soil and sediment.

Carbon and nitrogen budget in fish-polychaete integrated aquaculture system

Integrated multi-tropic aquaculture(IMTA)systems have been used in China for many years and have achieved significant economic,social,and ecological benefits.However,there is still a lack of benthic bioremediation species that can effectively utilize the aquaculture particulate organic waste in the system.Polychaete Perinereis aibuhitensis Grube is used as an environmental remediation species for large-scale aquaculture to reduce particulate organic waste,which is of great significance to environmental protection.To improve bio-elements utilization efficiency,P.aibuhitensis was applied for IMTA indoor fish(Hexagrammos otakii)farming.Results showed that in the system,production of 1 kg of the fish discharged 2141-2338 mg of carbon and 529-532 mg of nitrogen,while in the monoculture of the fish,the figures were 3033-3390 mg and 764-794 mg,or 24.84%-35.26%and 30.35%-33.32%less,respectively.This approach promoted IMTA technology that could utilize the particulate organic waste from intensive aquaculture and reduce the adverse environmental effects.

Electrocoagulation coupled with electrooxidation for the simultaneous treatment of multiple pollutants in contaminated sediments

In situ and simultaneous remediation of a variety of pollutants in sediments remains a challenge.In this study,we report that the combination of electrocoagulation(EC)and electrooxidation(EO)is efficient in the immobilization of phosphorus and heavymetals and in the oxidation of ammonium and toxic organicmatter.The integratedmixed metal oxide(MMO)/Fe anode system allowed the facile removal of ammonium and phosphorus in the overlying water(99% of 10 mg/L NH_(4)^(+)-N and 95% of 10 mg/L P disappeared in 15 and 30 min,respectively).Compared with the controls of the single Fe anode and single MMO anode systems,the dual MMO/Fe anode system significantly improved the removal of phenanthrene and promoted the transition of Pb and Cu from the mobile species to the immobile species.The concentrations of Pb and Cu in the toxicity characteristic leaching procedure extracts were reduced by 99%and 97% after an 8 hr operation.Further tests with four real polluted samples indicated that substantial proportions of acid-soluble fraction Pb and Cu were reduced(30%-31% for Pb and 16%–23% for Cu),and the amounts of total organic carbon and NH_(4)^(+)-N decreased by 56%–71% and 32%–63%,respectively.It was proposed that the in situ electrogenerated Fe(II)at the Fe anode and the active oxygen/chlorine species at the MMO anode are conducive to outstanding performance in the co-treatment of multiple pollutants.The results suggest that the EC/EO method is a powerful technology for the in situ remediation of sediments contaminated with different pollutants.

Stabilization of heavy metals in sediments:A bioavailability-based assessment of carbon adsorbent efficacy using diffusive gradients in thin films

This study investigated the effectiveness of carbon adsorbents as remediation material for sediments contaminated with heavy metals and the feasibility of utilizing diffusive gradients in thin films(DGT)as a biomimetic tool to estimate the accumulation of heavy metals in Venerupis philippinaram(Manila clam).The results showed that carbon materials had significant inhibitory effects(14.0-53.0%)on the enrichment of heavy metals in organisms and the order of increasing overall inhibitory effect was:charcoal,peat,activated carbon,and biochar.There were significant correlations(P<0.0001)between the four heavy metals accumulated in Venerupis philippinaram and those accumulated in DGT devices after 28 days in the laboratory.Observed concentrations of heavy metals enriched in DGT(5.4-42.0%)were less than accumulations in Venerupis philippinaram.The results of in situ DGT applications showed significant correlations between the amount accumulated in DGT and the acid-soluble portion in sediments for both Cu and Pb,with positive linear correlations and R-squares of 0.97 and 0.92,respectively.These results supported the notion that a DGT device can be used as a biomimetic tool that predicts and monitors the accumulation of heavy metals in aquaculture ponds.Future studies should focus on improving the stabilization of heavy metals in sediments using different types of carbon sorbents,as well as minimizing simulation deviations using DGT.