Release of mercury from Rocky Mountain forest fires

Abstract

Concentrations of mercury (Hg) in soil profiles and vegetation were examined in unburned areas and in areas recently burned by wildfires of low, medium, and high fire severities in western Wyoming. Paired unburned and burned sampling sites with similar tree species composition, forest stand age, climate, and geological substrate were studied. Results indicate that Hg release from forest fires is dependent on the tree species composition of the forest, which affects prefire Hg accumulation, as well as the forest fire severity. On the basis of an average of 2.7 × 106 ha of forest and shrubland burned annually in the United States we estimate that wildfires and prescribed burns in the United States release 19 to 64 × 106g of Hg annually. This represents between 13 and 42% of the estimated United States anthropogenic Hg flux of 150 × 106g.

Remobilization of trace elements by forest fire in Patagonia, Chile

“…However, these contaminants are released in more labile forms when vegetation and soil organic matter are burned and volatilized by fire (Young and Jan 1977;Biswas et al 2007;Wiedinmyer and Friedli 2007). In addition, wildfires increase erosion rates by as much as two orders of magnitude, which subsequently increases the transport rates of remobilized contaminants to water bodies (Cohen et al 2005;Stein et al 2012;Warrick et al 2012).…”

“…Trace elements sorb to terrestrial sediments, vegetation, and soil organic matter in forests, where they are relatively immobile (Siccama et al 1980;Friedland et al 1984;Biswas et al 2007;Obrist et al 2008). However, these contaminants are released in more labile forms when vegetation and soil organic matter are burned and volatilized by fire (Young and Jan 1977;Biswas et al 2007;Wiedinmyer and Friedli 2007).…”

The impact of over 100 years of wildfires on mercury levels and accumulation rates in two lakes in southern California, USA

“…A date for RDL-6 (59-63 cm) was not assigned, since this section of the core was deposited below measurable levels for 210 Pb, which were used to date the core Mailman and Bodaly 2005), while atmospheric Hg levels (i.e., Hg o ) increase (Friedli et al 2003a, b, Sigler et al 2003. Ash may contain lower Hg levels compared to unburned soil (Biswas et al 2007), however, Kelly et al (2006) reported a higher release of total Hg and methylmercury (MeHg) in burned compared to unburned catchments within one year following a fire near Moab Lake (Canada). Veiga et al (1994) also suggested elevated Hg concentrations in the Brazilian Amazon may be due to increased erosion of Hg-laden soil and ash resulting from slash and burn agricultural methods.…”

“…Hg levels in soils typically decrease following a fire (Amirbahman et al 2004;Biswas et al 2007;DiCosty et al 2006;Engle et al 2006;Friedli et al 2001; Harden , black dotted line) for CL-1. For the latter, the maximum value was 6,000 lg m -2 year -1 (not included on the graph).…”

Pyrogenic Remobilization of Historic Industrial Lead Depositions

“…20 Forests are a reservoir for trace metals sequestered in sediments, soil organic matter, and vegetation, where they are relatively immobile. 21,22 The combustion of soil organic matter and vegetation releases those sequestered trace metals and increases their bioavailability. 21,23,24 Forest fires also increase soil erosion by as much as 2 orders of magnitude, 25 accelerating the transport of those mobilized trace metals to water bodies and further increasing their bioavailability.…”