Influence of Asian and Western United States Agricultural Areas and Fires on the Atmospheric Transport of Pesticides in the Western United States

Abstract

Historic and current use pesticides (HUPs and CUPs), with respect to use in the United States and Canada, were identified in trans-Pacific and regional air masses at Mt. Bachelor Observatory (MBO), a remote high elevation mountain in Oregon’s Cascade Range located in the United States, during the sampling period of April 2004 to May 2006 (n=69), including NASA’s INTEX-B campaign (spring 2006). Elevated hexachlorobenzene (HCB) and α-hexachlorocyclohexane (α-HCH) concentrations were measured during trans-Pacific atmospheric transport events at MBO, suggesting that Asia is an important source region for these HUPs. Regional atmospheric transport events at MBO resulted in elevated dacthal, endosulfan, metribuzin, triallate, trifluralin, and chlorpyrifos concentrations, with episodic increases in concentration during some spring application periods, suggesting that the Western U.S. is a significant source region for these CUPs. Endosulfan I, γ-HCH, and dacthal concentrations were significantly positively correlated (p-value < 0.05) with increased air mass time in Western U.S. agricultural areas. Elevated γ-HCH concentrations were measured at MBO during both trans-Pacific and regional atmospheric transport events, including regional fire events. In addition to γ-HCH, elevated Σchlordane, α-HCH, HCB, and trifluralin concentrations were associated with fires in Western North America due to revolatilization of these pesticides from soils and vegetation. Trans-chlordane/cis-chlordane and α-HCH/γ-HCH ratios were calculated and may be used to distinguish between free tropospheric and regional and/or Asian air masses.

Transpacific transport of benzo[a]pyrene emitted from Asia

“…At the MBO site, the modeled concentrations were poorly correlated with measured concentrations (r=0.09),likely because of the high altitude (2700 m a.s.l.) and strong influence by local North American emissions of this site (Primbs et al, 2008). At this site local wind patterns are strongly influenced by the local topography, which cannot be captured by course wind data in a global-scale transport model.…”

“…The model results were compared with the observations at six monitoring sites including Changdao, Gosan, Kanazawa, Okinawa, Cheeka Peak Observatory (CPO), and Mount Bachelor Observatory (MBO) during different time periods when observations were actually conducted (Feng et al, 2007;Lee et al, 2006;Tamamura et al, 2007;Primbs et al, 2007;Killin et al, 2004;Primbs et al, 2008). A map of the location of these sites as well as a comparison of their measured concentrations is shown in Fig.…”

“…Zhang et al: Transpacific transport of benzo [a]pyrene emitted from Asia PAH compounds (Lang et al, 2008;Primbs et al, 2008;Klasmeier et al, 2006), higher emissions of PAHs from Asia might threaten ecological environments and human health on an intercontinental or even global scale.…”

“…Surface concentration measurements combined with backward trajectories have shown that semi-volatile organic compounds (SVOCs), including PAHs, can be transported across the Pacific Ocean in about a week under certain meteorological conditions (Primbs et al, 2007;Primbs et al, 2008;Killin et al, 2004). For example, Killinet al (2004) observed significantly elevated concentrations of PAHs and other SVOCs during 15-16 March, 27-28 March and 22-23 April 2002, when backward trajectories passed over Asia, suggesting Asia as the potential source of these compounds.…”

Currently used pesticides, hexachlorobenzene and hexachlorocyclohexanes in the air and seawater of the German Bight (North Sea)

“…The pre-emergence herbicide dacthal has been reported to be one of the most frequently detected CUPs in the air of North America, [28,29] but its occurrence in the European environment has been rarely reported. Dacthal has been frequently detected in snow and rain.…”