540 Environmental Toxicology and Chemistry, Vol. 23, No. 3, pp. 540–549, 2004  2004 SETAC Printed in the USA 0730-7268/04 $12.00 + .00 PERSISTENT ORGANIC POLLUTANTS IN AIR AND VEGETATION FROM THE CANADIAN ROCKY MOUNTAINS DEBORAH A. DAVIDSON,*² A NDREW C. WILKINSON,² L YNDA E. KIMPE,‡ and JULES M. BLAIS² ²Program for Chemical and Environmental Toxicology, Department of Biology, University of Ottawa, P.O. Box 450, Station A, Ottawa, Ontario K1N 6N5, Canada ‡Department of Biology, University of Ottawa, P.O. Box 450, Station A, Ottawa, Ontario K1N 6N5, Canada ( Received 5 December 2002; Accepted 7 July 2003) Abstract—The exchange of chlorinated organic pollutants between air and vegetation in cold, mountain environments was inves- tigated through the extraction of coniferous vegetation and high-volume air samples collected from the Canadian Rocky Mountains during the summers of 1999 and 2000. Concentrations of several compounds in vegetation increased as temperatures decreased, whereas atmospheric concentrations were not related to temperature. Daily cycling of these compounds between air and vegetation as a result of diurnal temperature changes was not observed. Compared with concentrations in vegetation from the Canadian Rocky Mountains, plant samples from the western valley in British Columbia (Canada) showed higher pollutant levels. Chemical partitioning between vegetation and air was not correlated with temperature, indicating that air contamination is governed by long-range transport and not by local revolatilization events. Based on these observations, we show that both deposition at higher altitudes and long- range atmospheric transport influence chemical accumulation in vegetation from the Canadian Rocky Mountains. Keywords—Vegetation Pollutants Altitude Air Mountains INTRODUCTION Several chlorinated organic contaminants, such as poly- chlorinated biphenyls (PCBs) and the pesticides hexachloro- cyclohexane (HCH), persist in the environment, resulting in their widespread global distribution. The semivolatile nature of these compounds allows them to travel great distances through the air and causes them to accumulate in colder regions via atmospheric deposition [1]. It has been documented that this global distillation contributes to high contaminant con- centrations in polar environments [2]. Recent studies have examined the possibility that alpine ecosystems may also retain semivolatile organic compounds (SVOCs) due to the cold temperatures observed at high alti- tudes [3–5]. However, the importance of terrestrial vegetation in this process has not been examined in detail. The tendency for vegetation to retain SVOCs is particularly important in heavily forested areas such as northern Canada. Forests can intercept gaseous airborne chemicals traveling north before they reach higher latitudes where colder temperatures favor their condensation and deposition [6]. Coniferous needles can grow on the tree for several years and, provided chemical volatility is low enough, these plants can adsorb and accumulate airborne lipophilic compounds throughout their lifetime [7]. Semivolatile pesticides are in- troduced into the environment via revolatilization following application, initial scatter upon application, and wind erosion of soil. In the air, they travel to cold regions within days, where they are more resistant to breakdown than in temperate cli- mates where pesticides are commonly applied [8]. The per- sistent and bioaccumulative nature of organochlorine (OC) compounds may permit them to remain in a cycle of volatil- * To whom correspondence may be addressed (deborahannedavidson@hc-sc.gc.ca). ization and deposition between vegetation, soil, and the air for decades [7]. If such cycles are occurring in the Canadian Rocky Mountains, alpine and subalpine ecosystems may be contin- uously exposed to certain hazardous chemicals. We recently examined the accumulation of several organ- ochlorine compounds in terrestrial vegetation in the Canadian Rocky Mountains and demonstrated that more volatile chem- icals are progressively distilled toward higher altitudes and subsequently become concentrated in mountain environments [9]. This study provides a more detailed investigation into the temperature dependence of persistent organic pollutant (POP) concentrations in vegetation and air from this mountain area using data collected from the previous examination. In this article, we also examine the daily variations in plant POP concentrations and the accumulation of these chemicals in veg- etation along a longitudinal gradient from the interior of British Columbia toward the Rocky Mountains. EXPERIMENTAL SECTION Sample collection Vegetation was sampled from seven sites in the Canadian Rocky Mountains (Fig. 1) [9]. Vegetation samples were also collected along a longitudinal transect in British Columbia from Kamloops to Revelstoke in mid-July 2000 (Table 1). To ascertain if daily cycling of POPs occurs between air and vegetation, diurnal samples were collected in early morning (n = 12) and late afternoon (n = 12) on three separate oc- casions at Bow Lake (AB, Canada). Air was sampled using a high-volume air sampler placed at Bow Lake and Donald Station (AB, Canada) in 1999 and at Bow Lake, Sundre (AB, Canada), and Lower Kananaskis Lake (BC, Canada) in 2000. Air samplers were run for a period of 4 d during the 1999 sampling season and for 2 d during the summer of 2000, coinciding with vegetation sampling. An