Polycyclic aromatic hydrocarbons and volatile organic compounds in biochar and biochar‐amended soil: a review

Abstract

Residual pollutants including polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and carbon (aceous) nanoparticles are inevitably generated during the pyrolysis of waste biomass and remain on the solid coproduct called biochar. Such pollutants could have adverse effects on the plant growth as well as microbial community in soil. Although biochar has been proposed as a ‘carbon negative strategy’ to mitigate the greenhouse gas emissions, the impacts of its application with respect to long‐term persistence and bioavailability of hazardous components are not clear. Moreover, the co‐occurrence of low molecular weight VOCs with PAHs in biochar may exert further phytotoxic effects. This review describes the basic need to unravel key mechanisms driving the storage vs. emission of these organics and the dynamics between the sorbent (biochar) and soil microbes. Moreover, there is an urgent need for standardized methods for quantitative analysis of PAHs and VOCs in biochar under environmentally relevant conditions. This review is also extended to cover current research gaps including the influence of biochar application on the short‐ and long‐term fate of PAHs and VOCs and the proper control tactics for biochar quality and associated risk.

Comparative Metagenomics Reveals Enhanced Nutrient Cycling Potential after 2 Years of Biochar Amendment in a Tropical Oxisol

“…Additionally, pathways involved in the metabolism of aromatic compounds were significantly higher in biochar-amended samples, including pathways for the degradation of some naturally occurring aromatics from plants and polycyclic aromatic hydrocarbons (PAHs), likely associated with the biochar (68). This finding contrasts with previous studies that observed decreased degradation of PAHs in biochar-amended soils due to limited bioavailability, such as PAH adsorption onto the biochar surface (69,70). Interestingly, control samples were enriched in the pathways involved in the degradation of lignin precursors, (i.e., cinnamic acid) (71) and several ring-cleaving enzymes within the 4-hydroxyphenylacetic acid catabolism pathway (72).…”

Cycling and Budgets of Organic and Black Carbon in Coastal Bohai Sea, China: Impacts of Natural and Anthropogenic Perturbations

“…It constitutes a significant fraction of OC and has received considerable attention due to its physical and chemical properties being remarkably different from those of other fractions of OC. As a result, the roles of BC differ from those of OC in a wide range of biogeochemical processes, such as the regional/global carbon cycle (Bird et al, 2015;Guo et al, 2004;Sánchez-García et al, 2012), climate change (Menon et al, 2002;Ramanathan & Carmichael, 2008), sorption of toxic pollutants, and bioavailability/fate (Dutta et al, 2017). It is therefore of great necessity to calculate and compare OC and BC fluxes independently and to determine the factors that regulate these fluxes in coastal regimes accurately.…”

Dissipation and sorption processes of polycyclic aromatic hydrocarbons (PAHs) to organic matter in soils amended by exogenous rich-carbon material

“…It is assumed that soils amended with exogenous organic matter increase pollutant sorption and reduce their availability. Many different amendments have been dedicated for this purpose (Koltowski et al 2016;Kuśmierz et al 2016;Dutta et al 2017;Ćwieląg-Piasecka et al 2018;Bejger et al 2018).…”

“…Increasingly, various researchers propose the application of ERCM to immobilize PAHs in soils (Beesley et al 2011;Ghosh et al 2011;Koltowski et al 2016;Kuśmierz et al 2016;Dutta et al 2017). These sorbents mainly reduce the freely dissolved fraction of the contaminants that reach the pore water by diffusion, sorption, and partitioning processes (Pignatello 2012;Wang et al 2017).…”