Polycyclic Aromatic Hydrocarbons in the Snowpack and Surface Water in Blackwood Canyon, Lake Tahoe, CA, as Related to Snowmobile Activity

Abstract

Snowpack in alpine environments may contain appreciable levels of regional pollution acquired through natural processes of wet and dry deposition, as well as from immediate sources such as snowmobile engine exhaust. Understanding the fate and transport of pollutants in alpine environments is a crucial step towards managing emission sources in alpine terrain to mitigate their impacts on natural resources. This study presents detailed chemical analysis for 94 species of polycyclic aromatic hydrocarbons (PAH) in 55 samples of snow and surface water collected in Blackwood Canyon, a tributary to the west shore of Lake Tahoe that is a popular winter recreation area for snowmobile riders. Analyses included toxic and persistent PAH, emitted as products of incomplete combustion and useful for identifying fossil fuel combustion emissions in the environment. Average background snow PAH concentrations were used to estimate background PAH surface loading (μg.m −2 ). Loadings in excess of the estimated background are mapped and compared with observations of snowmobile activity to determine effects of snowmobile emissions on snow water quality. Loading of heavy PAH, those having three or more aromatic rings, in snow was found to be significantly greater than background loading (α = 5%) where snowmobile tracks cover more than 50% of the snow surface. Loadings were 8-20 times greater than background levels where snowmobile traffic was most concentrated over snow covered roads. PAH were also measured in snow melt and surface water samples in Blackwood Canyon for comparison with snow samples. Flux of PAH (g.day −1 ) from Blackwood Creek into Lake Tahoe was calculated and compared to estimates of background flux, increasing from 74 g.day −1 to 480 g.day −1 over an 8-day period during spring run-off.

Polycyclic aromatic hydrocarbons (PAHs) and their nitrated and oxygenated derivatives in the Arctic boundary layer: seasonal trends and local anthropogenic influence

“…Overall, benzo[a]anthracene, phenanthrene, and 1methylnaphthalene accounted for 68 % of the average PAH profile of these days with known high snowmobile traffic. The predominance of phenanthrene and methylated PAHs in snow samples contaminated by snowmobile emissions has previously being reported (McDaniel and Zielinska, 2014), although the contribution of 2-methylnaphthalene and 2methylfluoranthene in the present study was found to be negligible. Different engine technologies and fuel quality may have been responsible for this.…”

“…No scientific studies on PAC emissions from snowmobiles have been reported yet. Nonetheless, snowmobile driving is a well-documented major source of a list of aromatic hydrocarbons (Zhou et al, 2010;Reimann et al, 2009;Eriksson et al, 2003;Shively et al, 2008), and PAHs were detected in snow along snowmobile tracks (McDaniel and Zielinska, 2014;Rhea et al, 2005;Oanh et al, 2019). Moreover, a factor of 3 higher NO x emissions from snowmobiles compared to gasolinedriven cars in Svalbard are reported by the Norwegian Climate and Pollution Agency (Vestreng et al, 2009) with the main contribution from four-stroke snowmobiles.…”

Deposition of brown carbon onto snow: changes in snow optical and radiative properties

“…OC compounds that are absorbing in the ultraviolet (UV) and short-visible wavelengths are colloquially known as BrC. The wavelength dependency of BrC aerosol absorption coefficients can be described by an absorption Ångström exponent (AAE) that is significantly greater than one (Chakrabarty et al, 2010;Corr et al, 2012;Kirchstetter et al, 2004;McNaughton et al, 2011;Moosmüller et al, 2011), whereas BC aerosol absorption coefficients are less wavelength-dependent (i.e., AAE ≈ 1) over the visible range and its periphery (Bergstrom et al, 2007;Moosmüller et al, 2009). The optical properties of BrC are described by the wavelength-dependent BrC complex refractive index m λ written as…”

Nutrient and mercury deposition and storage in an alpine snowpack of the Sierra Nevada, USA

“…Finally, estimates of basin-wide loading based on spatially extrapolated concentrations and a satellite-based snow water equivalent reconstruction model identify snowpack chemical loading from atmospheric deposition as a substantial source of nutrients and pollutants to the Lake Tahoe Basin, accounting for 113 t of N, 9.3 t of P, and 1.2 kg of Hg each year. McDaniel, 2013;Sickman et al, 2003;TERC, 2011;Vicars and Sickman, 2011;Williams and Melack, 1991a, b). Sierra Nevada snowpack supplies the majority of water to downstream communities as well as to some of the nation's largest agricultural areas.…”