Polycyclic aromatic hydrocarbon occurrence in forest soils in response to fires: a summary across sites

Biwei Yang, Yameng Shi, Shan Xu, Yinghui Wang, Sifang Kong, Zongwei Cai*, Junjian Wang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Forest fires are important sources of polycyclic aromatic hydrocarbons (PAHs) in soils. However, factors controlling PAH production in soils subjected to fires in different sites are poorly understood. Here, we analyzed 143 sets of previously published data to evaluate the concentrations and composition profiles of PAHs in ash and soils associated with forest fires and to assess the impacts of soil depth, fire intensity, post-fire duration, and vegetation type on their occurrence. Compared to unburned soils, the total PAH concentrations increased by 205% (95% confidential interval of 152–269%; n = 136) in soils associated with fires. This increase surpassed that of PAH toxic equivalents (73%) because fires produce dominantly low-ring PAHs with relatively low toxicity. PAH concentrations in fire-impacted sites increased by 684%, 258%, and 155% in the ash, 0–5 cm soil depth interval, and >5 cm soil depth interval, respectively. The increases in PAH concentrations associated with mild-intensity fires (412%) exceeded those associated with moderate-intensity (163%) and high-intensity (168%) fires, which is possibly due to pyromineralization or volatilization of organic matters at high burning temperatures. These increases were highest within a month after the fire (280%), gradually decreasing over time, and showed no significant difference compared to the reference sites after 24 months. The concentration increases exhibit no major difference between various vegetation types (broad-leaved forest vs. coniferous forest vs. shrub). Assessments reveal that exposure to post-fire soil PAHs involves no serious human health risk. However, potential adverse effects of soil PAHs on other organisms (e.g., microbes and plants) and ecosystems should be further examined. The present study highlights the strong impacts of soil depth, fire intensity, and post-fire duration, and the relatively weak impact of the vegetation type on PAH concentrations in soils associated with fires in different areas.
Original languageEnglish
Pages (from-to)32-41
Number of pages10
JournalEnvironmental Sciences: Processes and Impacts
Volume24
Issue number1
Early online date30 Nov 2021
DOIs
Publication statusPublished - 1 Jan 2022

Scopus Subject Areas

  • Public Health, Environmental and Occupational Health
  • Management, Monitoring, Policy and Law
  • Environmental Chemistry

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