Environ. Sci. Technol. 2000, 34, 5097-5105
Toxaphene, Chlordane, and Other Organochlorine Pesticides in Alabama Air L I I S A M . M . J A N T U N E N , * ,† TERRY F. BIDLEMAN,† TOM HARNER,† AND WILLIAM J. PARKHURST‡ Meteorological Service of Canada, ARQP, 4905 Dufferin Street, Downsview, Ontario, M3H 5T4 Canada, and Tennessee Valley Authority, Muscle Shoals, Alabama 35660
Air samples were collected in Alabama in JanuaryOctober 1996 and in May 1997, to determine the seasonal variations of toxaphene and other OC pesticides (chlordanes, DDTs, dieldrin, and HCHs). Log partial pressure versus 1/T plots for γ-HCH, dieldrin, chlordanes, and their metabolites showed significant relationships, whereas those for toxaphene, heptachlor, and p,p′-DDE did not. The chromatographic profile of toxaphene congeners in air and soil showed depletion of certain labile congeners, notably B8-531 and B8-806/809; other persistent congeners (B81412 and B9-1679) were enriched in air samples. Concentrations of toxaphene in Alabama air were 6-40 times higher than in the Great Lakes region, and chlordane in Alabama air exceeded Great Lakes concentrations by 3-9fold. This suggests that transport from the southern U.S. is a continuing source of toxaphene and chlordane to the Great Lakes. Levels of HCHs and dieldrin in Alabama were similar to those in the Great Lakes region. Patterns of 8-chlorinated bornanes in air more closely resemble residues in soil than the technical toxaphene standard. Enantiomer ratios of chlordanes in air were nearly racemic, indicating that their source is probably evaporation from termiticide usage rather than from soils, which contain nonracemic chlordanes.
Introduction Organochlorine pesticides (OCs) were at one time widely used in North America. Compounds included toxaphene, chlordane, aldrin, dieldrin, heptachlor, and DDT. Although these chemicals were banned 10-28 years ago they are still present in ambient air in the Great Lakes (1) and the Arctic (2). Air monitoring in the early to mid 1990s by the Integrated Atmospheric Deposition Network (IADN) found a decrease in the concentrations of OCs around the Great Lakes, and these time trends were used to project virtual elimination dates (when concentrations fall below detectability by today’s methods) of 2010-2070 (1). Since these pesticides have not been used for decades, some mechanisms are maintaining current ambient levels. These may include transport from countries south of the U.S.A. border where some OCs are currently applied (3) and re-emissions from agricultural soils * Corresponding author phone: (416)739-4473; fax: (416)739-5708; e-mail:
[email protected]. † Meteorological Service of Canada, ARQP. ‡ Tennessee Valley Authority. 10.1021/es001197y CCC: $19.00 Published on Web 11/16/2000
2000 American Chemical Society
in past usage regions. Spencer et al. (4) measured DDT in air above the soils of a farm in California where DDT was last used 23 years previously and found 9.2-16.9 ng/m3 total DDTs in February and September. These levels are 2-3 orders of magnitude higher than those at IADN stations (1). Elevated concentrations of OCs were also found in air above agricultural soils in British Columbia (5). High episodes of OCs in air sampled in southern Ontario were associated with air masses that arrived from the southern U.S, versus lower concentrations during northerly transport (6, 7). Ambient air samples taken in South Carolina in 19941995 showed levels of chlordanes and toxaphene that were an order of magnitude higher than those found in the Great Lakes region (8). No relationship of toxaphene concentrations in South Carolina to air transport direction was found, suggesting that the toxaphene was volatilized from regional soils. The purpose of this study was to measure airborne OC pesticides in Alabama to determine whether the southern U.S. is a potential source region for transport to the Great Lakes. Alabama was selected because toxaphene usage there was the highest in southern states in 1980 (9). Residues of toxaphene and other OCs were recently reported for Alabama agricultural soils (10). In a companion paper (11), measured atmospheric concentrations are compared to those predicted from fugacity-based volatilization model, which uses soil residues as drivers.
Experimental Section Sample Collection and Preparation. Air samples were collected in northern Alabama at the Tennessee Valley Authority (TVA) reservation. The 176 000 ha site (34°48′N, 87°40′W) abuts the towns of Muscle Shoals and Florence and is surrounded by farmland. Samples were collected from January to October 1996 and in May 1997. In most months, 1-2 samples were collected except for August 1996 and May 1997 when 6 and 7 samples per month were taken (Table 1). A PS-1 (Wedding) sampler was used, consisting of a 10.2 cm diameter glass fiber filter followed by two polyurethane foam (PUF) traps (6.8 cm diameter × 4.2 cm) in a glass cylinder. Indoor air was also sampled for chlordanes in five private homes in Muscle Shoals, using a low-volume (30 L/min) collector and smaller PUF traps (5 cm diameter × 3 cm thick). PUF traps and filters were cleaned before use as previously described (12). Samples were collected over a ∼24 h period with air volumes ranging from 334 to 465 m3. Filters were refluxed in dichloromethane and PUF traps were Soxhlet extracted in petroleum ether overnight. The extracts were concentrated by rotary evaporation, blown down with a gentle stream of nitrogen and exchanged into isooctane. Extracts were cleaned up and fractionated on an alumina-silicic acid column to separate PCBs from the chlorinated pesticides. The column consisted of 3 g of silicic acid (deactivated with 3% water), overlaid with 1 g neutral alumina (deactivated with 6% water), and topped with 1 cm anhydrous granular Na2SO4 (13). The column was prewashed with 30 mL of dichloromethane and then 30 mL of petroleum ether. The sample was eluted with 20 mL of petroleum ether (fraction 1, containing the PCBs, heptachlor, a portion of the p,p′-DDE and o,p′-DDT, and a small amount of the Cl-8 toxaphenes) and then 30 mL of dichloromethane (fraction 2, containing the remainder of the chlorinated pesticides). Fractions were transferred to isooctane and adjusted to ∼1.0 mL for analysis. Additional cleanup was done by shaking the extract with 18 M H2SO4 (omitted for analysis of the oxygenVOL. 34, NO. 24, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
5097
annual mean SD
May 1966 and 1997 were b a HCH, hexachlorocyclohexane; TC, trans-chlordane; CC, cis-chlordane; TN, trans-nonachlor; CN, cis-nonachlor; HEPT, heptachlor; HEPX, heptachlor epoxide; and OXY, oxychlordane. averaged.
176 151 38 25 10 22 6.5 4.6 16 10 26 20 1.00:0.56:0.52 0:0.09:0.13 3.1 2.9 23 16 25 19 47 33 50 26 92 68
8 172-224 135 58 113 ( 64 474-611 121-545 194 ( 105 284 75 6 10-15 12 17 64 ( 66 55-89 50-74 58 ( 31 46 30 0.3-0.5 4-7 3.5
