Toxaphene Deposition to Lake Ontario via Precipitation, 1994−1998

Abstract

Precipitation samples collected continuously at Point Petre on Lake Ontario from November 1994 through December 1998 were analyzed for total toxaphene (=sum of hexa-, hepta-, octa-, and nonachloro bornanes) and chlorobornane congeners (1997-98 only). Composite triplicate samples were collected during 4-week intervals throughoutthe 4-year study using heated wet-only samplers. These results represent the first detailed data for toxaphene in Great Lakes precipitation. Seasonal volume-weighted mean concentrations for total toxaphene in precipitation ranged from 0.25 to 1.5 ng/L. Highest concentrations were found during the four spring (March-May) periods at roughly twice the annual means. The pattern for hexathrough nona-homologues over the 4 years did not vary appreciably with average ratios (relative to hepta-) of 0.08: 1.0:1.3:0.2. The volume-weighted mean concentrations for individual chlorobornane congeners were consistent in their season pattern with maximums seen in the spring. The major chlorobornane in precipitation, B8-2229 (Parlar 44), which was present at concentrations ranging from 0.016 to 0.079 ng/L, constituted 28 and 29% of the congener sum for 1997 and 1998, respectively. Lakewide loadings of toxaphene for Lake Ontario via precipitation were estimated to be 12, 17, 12, and 13 kg/year for 1995-1998, respectively. Previous toxaphene loading estimates were calculated for the individual Great Lakes on the basis of the only concentration data available, a single precipitation estimate of 0.2 ng/L from early work in northwestern Ontario. The loading estimates in this study indicate that precipitation inputs of toxaphene are 3-4 times higher than previously reported for Lake Ontario. The 1998 estimates of Lake Ontario wet deposition flux are 50% of the estimated gas deposition flux. However, wet flux values from this study exceed the net gas-phase mass transfer of toxaphene across the air-water interface.

Modeling of temporal patterns and sources of atmospherically transported and deposited pesticides in ecosystems of concern: A case study of toxaphene in the Great Lakes

“…Since atmospheric toxaphene is primarily in gas phase [Li et al, 2011b], either wet or dry deposition is dominated by that of gas-phase toxaphene. The toxaphene gas-phase dry deposition (approximately equaling to the total dry deposition of both phases) into Lake Ontario for the year 2000 predicted in Scenario 1 of this study, the scenario including the background as well as U.S. and Mexican residue sources, is 27 kg/year, which agrees very well with a measurement-based estimate of 26 kg/year calculated by Burniston et al [2005] based on toxaphene air concentration measurements including unpublished data of Jantunen and Bidleman as well as published data from Shoeib et al [1999] and Glassmeyer et al [1999]. Scenario 2, which considers the U.S. residues as the only source, yielded an annual dry deposition of 22 kg/year to Lake Ontario, which also agrees reasonably with the measurement-based estimate of 26 kg/year.…”

“…The toxaphene gas‐phase dry deposition (approximately equaling to the total dry deposition of both phases) into Lake Ontario for the year 2000 predicted in Scenario 1 of this study, the scenario including the background as well as U.S. and Mexican residue sources, is 27 kg/year, which agrees very well with a measurement‐based estimate of 26 kg/year calculated by Burniston et al . [] based on toxaphene air concentration measurements including unpublished data of Jantunen and Bidleman as well as published data from Shoeib et al . [] and Glassmeyer et al .…”

“…Figure compares the seasonal wet depositions into Lake Ontario modeled for the year 2000 with those measured for the year 1998 reported by Burniston et al . [], since there are no measured data for the year 2000. Figure shows that there is good qualitative agreement between the modeled seasonal pattern of wet deposition in both Scenarios 1 and 2 in 2000 and that of measured data in 1998 and good quantitative agreement as well except for spring.…”

“…Given the dependence of deposition on interannual variability in meteorology discussed later in this section, the modeled annual toxaphene wet depositions into Lake Ontario for 2000 in Scenarios 1 and 2 (23 and 21 kg/year, respectively) are in reasonable agreement with the toxaphene loadings for the years 1995 through 1998 (12, 17, 12, and 13 kg/year, respectively) that were estimated based on precipitation measurements and reported by Burniston et al . []. In contrast, Scenario 3 predicted an annual wet deposition of 1.87 kg/year to Lake Ontario, which is much lower than the measurements.…”

“…[23] We also compared the seasonal patterns of modeled and measured dry and wet toxaphene deposition to Lake Ontario. Figure 1 shows a comparison of the measurementbased seasonal dry deposition estimates of toxaphene into Lake Ontario reported by Burniston et al [2005] with the corresponding modeled values in Scenarios 1 through 3. The respective modeled values in Scenario 1 (green bars) agree quite well with the corresponding measurement-based values (red bars).…”