Polycyclic aromatic hydrocarbons in terrestrial and aquatic environments following wildfire: a review

Abstract

Wildfires are a natural landscape disturbance in many climates and forest types, but the cumulative impact of human-caused climate change, historical fire management and suppression, and changing species diversity in forests has led to an increase in the size and/or severity of wildfires in certain regions across the globe. There are a significant number of research studies on the effects of wildfire on human health, forest ecology, hydrology, and the physical, chemical, and biological properties of soils. However, research on the impact of wildfire on watersheds including toxicity in aquatic organisms, water chemistry, and fluvial sediment quality is less extensive, focusing primarily on water quality indicators such as nutrients and sediment flux. Recent research has shown that wildfires contribute to the environment significant amounts of polycyclic aromatic hydrocarbons (PAHs), which are compounds produced during the incomplete combustion of organic material, and are known to be toxic and mutagenic compounds. The primary objective of this paper is to review the recent literature that pertains to the contamination of surface waters and sediments, and source apportionment of wildfire-derived PAHs to determine where research gaps remain. Additional objectives are to assess the use of molecular ratios to apportion PAH sources, and finally, to create a roadmap for future studies in designing and conducting research that seeks to determine sources of wildfire-derived PAHs in water and sediment.

Determination of sediment sources following a major wildfire and evaluation of the use of color properties and polycyclic aromatic hydrocarbons (PAHs) as tracers

“…Using PAHs as tracers in sediment fingerprinting studies has not previously been undertaken, though there has been a growing interest in PAHs as a contaminant of terrestrial and aquatic systems after large wildfires (for a review, see Kieta et al 2023a ). The literature on tracing sediment after wildfire is also relatively sparse (Smith et al 2013 ), and therefore, the significant fires in the NRB that impacted many of its tributaries presented a unique opportunity to determine the suitability of PAHs as tracers.…”

“…They can be mutagenic or toxic to aquatic organisms and some are regulated in surface and drinking water (WHO 2008 ; CCME 2010 ). Therefore, PAHs are important to study post-wildfire due to their possible detrimental impacts on aquatic and terrestrial ecosystems (Incardona 2017 ; Ainerua et al 2020 ; Wallace et al 2020 ; Kieta et al 2023a ). Furthermore, as PAHs are usually enriched in the surface layers of soils following wildfire (Kim et al 2003 ; Choi 2014 ), they could be a potential tracer for wildfire-specific studies.…”

Polycyclic Aromatic Hydrocarbons (PAHs) in Freshwater Systems: A Comprehensive Review of Sources, Distribution, and Impacts

“…Although PAHs can have mixed influence of petrogenic and pyrogenic origins in urban streams, pyrogenic is the dominant source in most of recent reports [120]. In the case of forested streams, postwildfire runoff contribute substantially with pyrogenic PAHs content through various pathways (Figure 6) [47,121,122]. Although, streams presents mix of petrogenic and pyrogenic origin of PAHs, most of them are emitted in distant parts [123].…”

Molecular insights and impacts of wildfire-induced soil chemical changes

“…The burning of vegetation and SOM can induce the formation of polycyclic aromatic hydrocarbons (PAHs), a class of hundreds of organic compounds consisting of two or more merged benzene rings 38,39 . PAHs and their metabolites are carcinogenic, and some compounds (for example naphthalene) can inhibit post-fire seed germination 14,40,41 .…”