Both Sides of Coin: Benefits and Potential Negative Consequences of Biochar in Sediment Remediation

Abstract

Biochar has been widely used for in situ remediation of sediments in recent years because of its advantages including suitable surface area, pore structure, and abundant surface oxygen-containing functional groups. Nevertheless, leaching of some hazardous components of biochar, e.g., potentially toxic elements (PTEs), polycyclic aromatic hydrocarbons, persistent free radicals, dioxins-like compounds, etc., can pose ecological risks to the water–sediment system. In this review, the applications and associated mechanisms of biochar in the remediation of PTEs- and organic pollutants contaminated sediment systems have been illustrated and critically discussed. Additionally, the potentially hazardous constituents in biochar were summarized and the effects of biomass and production conditions on their bioavailability were reviewed. Furthermore, the effects of biochar addition on water/sediment eutrophication, phytotoxicity, benthic damage, and microbial community changes were discussed. On this basis, the monitoring and assessment measures of the potential risks of biochar were summarized, and the corresponding avoidance strategies for different risks were proposed. This paper aims to provide a baseline reference and guidance implications for the biochar selection, toxicity detection, and evaluation in the field of sediment remediation.