Fly bioash-borne polycyclic aromatic hydrocarbon removal by rapid-growth remediation systems of poplar, industrial hemp and parsley

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous, persistent, potentially carcinogenic organic pollutants in the environment. They are emitted mainly from the incomplete combustion of coal, oil, and wood, and energy crops. During biomass combustion for energy production, PAHs can accumulate mainly in fly ashes, and these ‘fly bioashes’ are sometimes used in agriculture as a source of mineral nutrients. The main aim of this study was to investigate the use of fast-growing plants for the removal of PAH contamination from fly bioash-treated soil. For PAH phytoremediation we chose fast-growing trees (poplars), an energy crop (industrial hemp), and a taproot vegetable (parsley). The removal of total PAHs from soil by natural attenuation in control treatments was less than 10%. Phytoremediation using poplar resulted in the greatest removal of 27% of the PAHs and there was no significant difference in PAH removal between poplar and hemp at 120 days post-planting. Individually screened PAHs with 2 to 4 benzene rings were removed from soil by poplars or hemp to a level of 21 − 39%. The parsley crop’s ability to accumulate and remove PAH was very low. Localization data showed the greatest accumulation of the tested PAHs in the roots, with little translocation of fly bioash PAHs from roots to shoots. Although the uptake of PAHs by plants is relatively low in general, poplar and hemp seem very promising for phytoremediation of soil containing PAHs from fertilization with biomass ash. We found that the removal efficiency of poplar could be improved through extended use over different vegetation periods. Innovation points include the identification of specific PAH removal efficiencies by different fast-growing plants, particularly highlighting the effectiveness of poplar and hemp in fly bioash-treated soils. The practical implications of this research suggest that integrating these plants into agricultural practices could enhance soil remediation while simultaneously serving as bioenergy crops, thereby providing a sustainable solution for managing soil PAH contamination.