Pesticides in the Atmosphere Across Canadian Agricultural Regions

Pesticides in the Atmosphere Across Canadian Agricultural Regions ... at St. Anicet, QC, a corn-growing region; (v) the Kensington site in PEI, Canada...
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Environ. Sci. Technol. 2008, 42, 5931–5937

Pesticides in the Atmosphere Across Canadian Agricultural Regions Y U A N Y A O , † T O M H A R N E R , * ,† PIERRETTE BLANCHARD,† LUDOVIC TUDURI,‡ DON WAITE,§ LAURIER POISSANT,| CLAIR MURPHY,⊥ WAYNE BELZER,# FABIEN AULAGNIER,| AND ED SVERKO∇ Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, M3H 5T4, Canada, Laboratoire de PhysicoToxicochimie des Syste`mes Naturels, ´ ´ Site universitaire, Equipe Perigourdine de Chimie Appliquee, ´ 24019 Perigueux cedex, France, Science and Technology Branch, Environment Canada, 2365 Albert Street, Park Plaza, Regina, Saskatchewan, S4P 4K1, Canada, Science and Technology Branch, Environment Canada, 105 rue McGill, 7e ´ etage (Youville), Montreal, Quebec, H2Y 2E7, Canada, Environmental Protection Branch, Environment Canada, 97 Queen Street, Charlottetown, Prince Edward Island, C1A 4A9, Canada, Environmental Conservation Branch, Environment Canada, 201-401 Burrard Street, Vancouver, British Columbia, V6C 3S5, Canada, and National Laboratory for Environmental Testing, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, L7R 4A6, Canada

Received March 28, 2008. Revised manuscript received May 28, 2008. Accepted May 29, 2008.

The Canadian Atmospheric Network for Currently Used Pesticides (CANCUP) was the first comprehensive, nationwide air surveillance study of pesticides in Canada. This paper presents the atmospheric occurrence and distribution of pesticides including organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), acid herbicides (AHs), and neutral herbicides (NHs) during the spring to summer of 2004 and 2005 across agricultural regions in Canada. Atmospheric concentrations of pesticides varied within years and time periods, and regional characteristics were observed including the following: (i) highest air concentrations of several herbicides (e.g., mecoprop, triallate, and ethalfluralin) were found at Bratt’s Lake, SK, a site in the Canadian Prairies; (ii) the west-coast site at Abbotsford, BC, had the maximum concentrations of diazinon; (iii) the fruit and vegetable growing region in Vineland, ON, showed highest levels for several insecticides including chlorpyrifos, * Corresponding author phone: + 1 416 739 4837; fax: + 1 416 739 4281; e-mail: [email protected]. † Science and Technology Branch, Environment Canada, Toronto, ON. ‡ Equipe Pe´rigourdine de Chimie Applique´e. § Science and Technology Branch, Environment Canada, Regina, SK. | Science and Technology Branch, Environment Canada, Montreal, QC. ⊥ Environmental Protection Branch, Environment Canada, Charlottetown, PEI. # Environmental Conservation Branch, Environment Canada, Vancouver, BC. ∇ National Laboratory for Environmental Testing, Environment Canada, Burlington, ON. 10.1021/es800878r CCC: $40.75

Published on Web 07/12/2008

 2008 American Chemical Society

endosulfan, and azinphos-methyl; (iv) high concentrations of atrazine and metolachlor were measured at St. Anicet, QC, a corngrowing region; (v) the Kensington site in PEI, Canada’s largest potato-producing province, exhibited highest level of dimethoate. Analysis of particle- and gas-phase fractions of air samples revealed that most pesticides including OCPs, OPPs, and NHs exist mainly in the gas phase, while AHs exhibit more diversity in particle-gas partitioning behavior. This study also demonstrated that stirred up soil dust does not account for pesticides that are detected in the particle phase. The estimated dry and wet deposition fluxes indicate considerable atmospheric inputs for some current-use pesticides (CUPs). This data set represents the first measurements for many pesticides in the atmosphere, precipitation, and soil for given agricultural regions across Canada.

Introduction Synthetic pesticides are among the most widely used chemicals in the world. The total use and number of different pesticide compounds has grown steadily since the early 1960s. In Canada, there are over 7000 pesticide products and over 500 active ingredient (a.i.) are currently registered for use, mainly (ca. 91%) for agriculture (total Canadian agricultural use 41 684 t a.i. in 1988) (1). This high level of use coupled with the persistence of some pesticides has led to contamination of various environmental media. Ecosystem exposure and potential adverse human effects have also been an increasing concern. In 1952, Daines (2) first reported 2,4-D as an air pollutant. Since then, a great deal of effort has been made to investigate the occurrence and processes of pesticides in the atmosphere and monitor agricultural worker exposure, pesticide drift during application, and volatilization of applied pesticides after application (3). However, most North American studies have been done in the United States and focused on organochlorine pesticides (OCPs) of which many are now banned or greatly restricted due to their high toxicity, persistence, bioaccumulation, and long-range transport potential. Canadian studies, likewise, generally concentrated on OCPs, with the exception of several that monitored the occurrence of selected herbicides in Saskatchewan (SK), Manitoba (MB), British Columbia (BC), and Ontario (ON) and fungicides in Prince Edward Island (PEI) (4, 5). Information on the nationwide atmospheric distribution of a wide range of pesticides in Canada is needed. In addition, the atmospheric transport and fate of airborne organic chemicals are strongly dependent on their distribution between the gas and particle phases. An accurate understanding of the air-particle interaction is essential to predict the long-range atmospheric transport (LRAT) potential for a particular chemical with subsequent deposition to nontarget regions, especially sensitive ecosystems such as the Great Lakes and Arctic. Very few measurements have been made to determine the particle-gas characteristics for pesticides and potential interaction between surface soil and ambient air. In May of 2000 and 2001, Clymo et al. (6) addressed the tillage-induced erosion of herbicides bound to airborne soil particles as a mechanism for off-site herbicide transport. They found that metolachlor and pendimethalin were released to the atmosphere as gas- and particle-phase species during soil incorporation activities, respectively. Most recently, Yao et al. (7) reported the long-term (1996-2002) trends of atrazine concentrations in both the vapor and particle phases at three Canadian Integrated Atmospheric Deposition Network (IADN) VOL. 42, NO. 16, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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sites. These studies only targeted a single or few pesticide compound(s); a comprehensive understanding of the pesticide particle-gas partitioning characteristics is still lacking. The Canadian Atmospheric Network for Currently Used Pesticides (CANCUP) was a 3-year national air surveillance program which was initiated in 2003 to assess atmospheric levels of pesticides, especially current-use pesticides (CUPs) in agricultural regions across Canada. The first-year field study (8) demonstrated that the spatial and temporal distribution of pesticides in the Canadian atmosphere generally reflects the pesticide use in each region. During the second and third years, new strategies for analyzing a wider range of pesticides including OCPs, organophosphate pesticides (OPPs), neutral herbicides (NHs), and acid herbicides (AHs) in air, precipitation, and soil samples were introduced. This paper presents the full data set obtained during the 2004 and 2005 air sampling campaigns and reveals the geographic pattern and particle-gas distribution of pesticides in the Canadian atmosphere. Results are also used to estimate dry and wet deposition fluxes for selected pesticides. The study also addresses the relationship between pesticide concentrations in the atmosphere and potential inputs from treated soil.

Methodology Sample Collection. The details of the sampling sites and periods for 2004 and 2005 sampling campaigns are provided in the Supporting Information (see Figure S1 and Table S1). Briefly, atmospheric samples were collected at eight locations (including six agricultural sites, one receptor site, and one urban site) across the country. Air samples were collected weekly using PS-1 high-volume samplers (Tisch Environmental, Inc., Village of Cleves, OH) at a flow rate of about 250 L min-1 (ca. 2500 m3 sample volume). Gaseous compounds were collected with polyurethane foam (PUF)/XAD-2/PUF sandwiches, while particulates were trapped on glass fiber filters (GFF) (8). To better understand the particle-gas partitioning characteristics of pesticides in the Canadian atmosphere, the gas- and particle-phase samples collected in BC, SK, Quebec (QC), and PEI regions in 2005 were analyzed separately. This approach was not applied to the samples from ON because the investigation on particle-gas partitioning of pesticides has been previously conducted at the same sites under the IADN program (7). Precipitation samples were collected monthly using MIC samplers (MIC Co., Thornhill, ON) equipped with XAD-2 columns (7). At the SK site, Bratt’s Lake, rainfall samples were collected using a Waite-Banner sampler (9). To address the issue of possible contamination of the air samples by windblown soil dust, composite soil samples were collected at all sites in 2005 (except Vineland, ON) by taking subsamples (∼20 g, 0-10 cm depth) at four locations about 10 m radius from the highvolume air sampler and then combining them. Field blanks for air and precipitation sampling were collected to determine possible contamination due to sample transport, storage, and treatment procedures. All samples were stored at ∼4 °C and in the dark until extraction. Sample Analysis. Prior to Soxhlet extraction, surrogate compounds (1,3-dibromobenzene and endrin ketone for OCPs, azinphos-methyl-d6 for OPPs, trifluralin-d14 for NHs, and 2,3-D for AHs) were added, then gas-phase (PUF/XAD2/PUF) samples and particle-phase (GFF) samples were extracted together (for all 2004 samples and ON samples collected in 2005) or separately (for all 2005 samples, except ON samples) using 400 mL hexane/acetone (50/50 v/v) for 24 h. The extracts were reduced in volume by rotary evaporation and exchanged into hexane (12 mL). Each final extract was split into four equal portions (3 mL) for different analyses and archiving. Rainfall (XAD-2 column) and soil (∼10 g) samples were treated in the same fashion. The extract 5932

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portions were further cleaned using silica gel (for OCPs, OPPs, and AHs) or Florisil (for NHs) columns, followed by gas chromatography (GC)/electron capture detector (ECD) and GC/mass spectrometry (MS) analyses for OCP and OPP/NH/ AH measurements, respectively. The analytical conditions are shown in Table S2-5. QA/QC. Sample analysis was performed at Environment Canada’s National Laboratory for Environmental Testing (NLET). All laboratory operations were monitored using strict QA/QC measures. These included a laboratory blank, blank spike and blank spike duplicate for every 12 samples. NLET also participates in, and is accredited by, the Canadian Association for Environmental Analytical Laboratories (CAEAL) as described by ISO 17025. The method detection limits (MDLs) are given in Table S6. Average recoveries were 109% (standard deviation/SD: 22%) for 1,3-dibromobenzene, 95% (SD: 19%) for endrin ketone, 91% (SD: 18%) for azinphosmethyl-d6, 90% (SD: 25%) for trifluralin-d14, and 73% (SD: 33%) for 2,3-D, respectively. Levels of selected pesticides in the field blanks were negligible compared to sample amounts. No recovery or blank correction was applied to the results.

Results and Discussion Atmospheric Occurrence and Regional Characteristics. In total, 83 pesticides were targeted in this study, and 66 and 73 compounds were detected in 2004 and 2005 air samples, respectively. Mirex, naled, terbufos, diallate, endaven, and hoegras were not detected in any of the air samples analyzed. Because chlorobenzenes (di- through penta-) have high vapor pressures and are known to have breakthrough artifacts during weekly air sampling, results for these compounds, although detected, are not presented in this paper. Figure 1(a-d) shows the box-and-whisker plots (n ) 44) for OCP, OPP, NH, and AH air concentrations measured in 2004 and 2005 across Canada. The top and bottom ends of the box indicate the 75th and 25th percentiles of the data set, respectively. The horizontal bar within the box is the median value. The highest and lowest values on the straight line (“whisker”) extending from the both ends of the box represent the maximum and minimum data. Overall, the 2004 and 2005 data pairs are similar for all four pesticide classes, indicating similar pesticide usage in Canada during the sampling periods. More detailed results on a site-by-site basis are summarized in Tables S7-9 of the Supporting Information. Although the air concentrations of individual compounds at a specific site varied between years and time periods, there were some clear regional characteristics with certain pesticides and/or pesticide classes showing elevated concentrations in certain regions. For example, endosulfan is the most frequently detected current-use OCP across the country. The highest average air concentrations of the two endosulfan isomers, R- and βendosulfans, were observed at Vineland, ON for both 2004 (R-: 1 220 pg m-3; β-: 274 pg m-3) and 2005 (R-: 7 540 pg m-3; β-: 1 340 pg m-3) (Table S9). This site also showed highest levels of p,p′-DDT and p,p′-DDE for 2004 (p,p′-DDT: 59.4 pg m-3; p,p′-DDE: 507 pg m-3) and 2005 (p,p′-DDT: 85.6 pg m-3; p,p′-DDE: 1 610 pg m-3). These high values are likely related to the heavy use of technical DDT in the past. The observed p,p′-DDT/p,p′-DDE ratio is less than 1, indicating an aged/ degraded source of DDT. This is consistent with the findings of previous studies (10, 11). For instance, a study in southern ON (10) showed that DDT residues persist in agricultural soils many decades after DDT was banned for agricultural use and that soil-to-air transfer is a big contributor to observed atmospheric burdens. Shen et al. (11) found low p,p′-DDT/ p,p′-DDE ratios at U.S. sites (e.g., 0.8 at Youngstown, OH in Cornbelt region and 0.9 at Muscle Shoals, AL) during summer 2000-summer 2001, consistent with the U.S. DDT ban in the early 1970s. They also reported high DDT/DDE ratios in

FIGURE 1. Box plot (log) air concentrations (pg m-3) of (a) OCPs, (b) OPPs, (c) NHs, and (d) AHs across Canada in 2004 and 2005. Central America (e.g., 1.2 at Belmopan, Beliza) indicating recent DDT use for malaria vector control in the region. Vineland also exhibited highest levels for several OP compounds including chlorpyrifos (2004: 21 900 pg m-3; 2005: 20 600 pg m-3), azinphos-methyl (777 pg m-3; 2 830 pg m-3), phosmet (6 260 pg m-3; 500 pg m-3), and parathion (784 pg m-3; 81.5 pg m-3) (Table S9). All these observations can be attributed to the fact that Vineland is an intensive agricultural area where insecticides are widely used for fruit and vegetable production. The Abbotsford site in BC showed the highest

average concentrations for diazinon in 2004 (27 400 pg m-3) and 2005 (437 000 pg m-3). This is likely associated with its application on berry crops in the region. On the east coast of Canada, the Kensington site in PEI showed maximum average concentration of dimethoate (268 pg m-3) in 2005 (no detection of this compound under CANCUP in 2004) (Table S9). This is in line with its intensive use on potato production on the island. Endosulfan concentrations at this site were much lower during 2004 and 2005 (99%) was calculated for 2,4-DB, whereas lower values were predicted for bromoxynil (0.4%) and dicamba (1%). The high calculated particle percentage for 2,4-DB is consistent with its predominance in the particle phase mentioned above (see also Figure 2d). Uncertainties with model predictions are expected for several reasons. First, the literature data for KOA (KOW and H) and pL° are variable. In this paper, evaluated and/or recommended KOW and H data by previous studies were preferentially selected (Table S11). Furthermore, and in the case of AHs, the Junge-Pankow and KOA models were not developed for polar chemicals. For example, Go¨tz et al. (19) compared a novel model of particle-gas partitioning based

on polyparameter linear free energy relationships to a widely adopted KOA model for polar and nonpolar pesticides. The two models were shown to be highly correlated for nonpolar pesticides and cases where sorption was dominated by absorption into organic matter (OM), while significant differences between the models existed for polar compounds and aerosols with low OM content. This underlines the need to develop new empirical models of particle-gas partitioning for polar pesticides. Data such as these, obtained through CANCUP, will contribute to this effort. Precipitation and Deposition Fluxes. Results for pesticides detected in precipitation samples are summarized in Tables S12 and S13 and illustrated for selected compounds as box-and-whisker plots in Figure 3a-d. In total, 42 and 58 pesticides were detected in 2004 and 2005 rainfall samples, respectively. To assess the impact of precipitation scavenging, especially for pesticides that have relatively high water solubility, the wet deposition fluxes at all sites were calculated using the following eq 5 FW ) (CrVr) ⁄ (ta)

(5)

where FW (ng m-2 d-1) is wet deposition flux, Cr is pesticide concentration in rainwater (ng L-1), Vr is rainfall volume (L), t is sampling time (d), and a is the surface area (0.25 m2) of the collection funnel. The estimated wet deposition fluxes of pesticides at each site in 2004 and 2005 are shown in Table S14. In 2005, of all target compounds, the highest fluxes were found for azinphos-methyl (2 700 ng m-2 d-1) and endosulfan (50.1 ng m-2 d-1) at Vineland, atrazine (848 ng m-2 d-1) at Egbert, diazinon (2 070 ng m-2 d-1) at Abbotsford, bromoxynil (414 ng m-2 d-1) at Bratt’s Lake, and metolachlor (406 ng m-2 d-1) at Baie St. Francois. To compare the relative importance of wet and dry deposition fluxes in the Canadian atmosphere, the dry deposition fluxes of pesticides at the BC, SK, QC, and PEI sites in 2005 were estimated using the mean particle-phase concentrations (Table S10) following Fd ) CpVd

(6)

where Fd (ng m-2 d-1) is the dry deposition flux, Cp (pg m-3) is the average pesticide concentration in the particle phase, and Vd is the deposition velocity of the particles, which is taken as 0.2 cm s-1 for all chemicals. This default value for Vd has been used to calculate pesticide dry deposition loading to the Great Lakes by IADN studies (7, 20). Resulting dry deposition fluxes are shown in Table S15 alongside wet deposition values according to site and for the four pesticide classes. The wet deposition fluxes are higher than dry deposition fluxes for most OCPs, OPPs, and NHs, while the opposite was observed for most AHs, mainly due to their higher particle percentages as discussed previously. These estimates suggest important atmospheric inputs through dry and wet deposition for given pesticides in certain areas. For example, a high dry deposition flux was observed for mecoprop (137 ng m-2 d-1) at Bratt’s Lake (Table S15), and a high wet deposition flux for diazinon (2 070 ng m-2 d-1) was found at Abbotsford (Table S14) in 2005 and similarly high wet deposition fluxes for atrazine at Egbert (848 ng m-2 d-1), Vineland (538 ng m-2 d-1), St. Anicet (447 ng m-2 d-1), and Baie St. Francois (692 ng m-2 d-1). Yao et al. (7) previously estimated a wet deposition load of 120-340 kg of atrazine into Lake Ontario during May-July 2004 based on the atrazine rainfall data from Egbert and Vineland for that year. Wet deposition fluxes of atrazine increased in 2005 by factors of 6.3 and 1.4 at Egbert and Vineland, respectively, corresponding to a wet deposition load of 643-900 kg into Lake Ontario over a 2-month period during the spring to summer of 2005 (estimated based on the measurement results from Egbert VOL. 42, NO. 16, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 3. Box plot (log) precipitation concentrations (ng L-1) of (a) OCPs, (b) OPPs, (c) NHs, and (d) AHs across Canada in 2004 and 2005. from May 12 to July 7 and Vineland from June 3 to August 5). This apparent increase may be related to increasing use of atrazine over this period, differences in sampling time (see Table S1), and/or variable meteorological conditions. Soil Measurement. In total, 51 pesticides were detected in the 2005 surface soil samples with results summarized in Table S16. Abbotsford shows highest soil concentrations for many OC compounds. These include current-use endosulfan (R: 4.65 ng g-1; β: 11.8 ng g-1) and legacy OCPs and their metabolites (dieldrin: 62.3 ng g-1; hexachlorobenzene: 4.37 ng g-1; heptachlor: 0.25 ng g-1; heptachlor epoxide: 9.68 ng g-1; cis-chlordane: 2.15 ng g-1; trans-chlordane: 4.52 ng g-1; cis-nonachlor: 2.54 ng g-1; trans-nonachlor: 3.00 ng g-1; and oxychlordane: 2.12 ng g-1). These high values are in agreement 5936

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with observed air concentrations. For instance, maximum average air concentrations of dieldrin have been measured at this site for 2003 (71.6 pg m-3) (8) and 2005 (279 pg m-3) (Table S9). This suggests that volatilization of residues from soil may be an important source to observed air burdens of legacy pesticides. In addition, highest soil levels of triallate (22.3 ng g-1) and bromoxynil (6.23 ng g-1) were found at Bratt’s Lake, supporting the observed highest air levels of these herbicides as described previously. Likewise, the highest atrazine soil concentration of 32.3 ng g-1 was detected at St. Anicet, consistent with its high air concentrations at this site. The soil residue data can also be useful to assess potential contamination of the air sampler, particularly the GFF, by

windblown soil dust. If suspended soil dust is an important source, we would have expected particle-phase detections for pesticides that had high soil concentrations. However, this was not the case. For example, although the highest soil concentrations of ∑DDT (p,p′: 121 ng g-1; o,p′: 16.2 ng g-1), ∑DDE (p,p′: 33.8 ng g-1; o,p′: 0.14 ng g-1), and ∑DDD (p,p′: 6.18 ng g-1; o,p′: 0.92 ng g-1) were found at Kensington site (Table S16, Figure S3), none of these compounds was detected in the particle phase (Table S10, Figure S3). Another example is for the polar herbicide 2,4-DB (Figure 2d) that was primarily in the particle phase at Bratt’s Lake, however this compound was below the detection limit in soil samples collected at the site. In summary, CANCUP results provide a comprehensive overview of the status of current-use and legacy pesticides in Canadian agricultural regions over the period of 2003-2006. In addition to providing some of the first measurements for certain pesticides in air, precipitation, and soils, the study has also yielded new information on atmospheric phase partitioning and estimates of deposition fluxes. As pesticide formulations and use practices change over the years, the CANCUP results may serve as a useful reference point for future investigations of pesticides in Canada.

Acknowledgments The study was supported by Environment Canada’s Pesticide Science Fund (PSF). We thank Frank Froude, Helena Dryfhout-Clark, Martin Pilote, Conrad Beauvais, Chris Marvin, Sean Backus, Christine Garron, Young Ryu, Phil Fellin, and Henrik Li for their assistance with sample collection and analysis.

Supporting Information Available Information on sampling sites and periods; GC/ECD and GC/MS conditions; method detection limits; ranges and average air concentrations of pesticides; average concentrations in gas and particle phases; particle-phase fraction (φ) values estimated from the pL°- and KOA-based models and literature used for model calculation; pesticide precipitation concentrations; estimated dry and wet deposition fluxes; soil concentration data; temporal trends of pesticide concentrations in gas and particle phases; comparison of the pesticide concentrations in air and soil samples from Kensington; and chemical information of target pesticides. This material is available free of charge via the Internet at http://pubs.acs.org.

Literature Cited (1) Brimble, S.; Bacchus, P.; Caux, P.-Y. Pesticide Utilization in Canada: A Compilation of Current Sales and Use Data; Environment Canada: Gatineau, QC, 2005. (2) Daines, R. H. 2,4-D as an air pollutant and its effect on various species of plants. In Air Pollution; McCabe, L. C., Ed.; McGrawHill Book Co., Inc.: New York, 1952; pp 140-143. (3) Majewski, M. S.; Capel, P. D. Pesticides in the Hydrologic System; Gilliom, R. J., Ed.; Ann Arbor Press, Inc.: Chelsea, MI, 1995; Vol. 1 (Pesticides in the Atmosphere: Distribution, Trends, and Governing Factors).

(4) Tuduri, L.; Harner, T.; Blanchard, P.; Li, Y.-F.; Poissant, L.; Waite, D. T.; Murphy, C.; Belzer, W. A review of currently used pesticides (CUPs) in Canadian air and precipitation: Part 1: Lindane and endosulfans. Atmos. Environ. 2006, 40, 1563–1578. (5) Tuduri, L.; Harner, T.; Blanchard, P.; Li, Y.-F.; Poissant, L.; Waite, D. T.; Murphy, C.; Belzer, W. A review of currently used pesticides (CUPs) in Canadian air and precipitation: Part 2: Regional information and perspectives. Atmos. Environ. 2006, 40, 1579– 1589. (6) Clymo, A. S.; Shin, J. Y.; Holmen, B. A. Herbicide sorption to fine particulate matter suspended downwind of agricultural operations: Field and laboratory investigations. Environ. Sci. Technol. 2005, 39, 421–430. (7) Yao, Y.; Galarneau, E.; Blanchard, P.; Alexandrou, N.; Brice, K. A.; Li, Y.-F. Atmospheric atrazine at Canadian IADN sites. Environ. Sci. Technol. 2007, 41, 7639–7644. (8) Yao, Y.; Tuduri, L.; Harner, T.; Blanchard, P.; Waite, D.; Poissant, L.; Murphy, C.; Belzer, W.; Aulagnier, F.; Li, Y.-F.; Sverko, E. Spatial and temporal distribution of pesticide air concentrations in Canadian agricultural regions. Atmos. Environ. 2006, 40, 4339– 4351. (9) Waite, D. T.; Cessna, A. J.; Gurprasad, N. P.; Banner, J. A new sampler for collecting separate dry and wet atmospheric depositions of trace organic chemicals. Atmos. Environ. 1999, 33, 1513–1523. (10) Meijer, S. N.; Shoeib, M.; Jantunen, L. M. M.; Jones, K. C.; Harner, T. Air-soil exchange of organochlorine pesticides in agricultural soils. 1. Field measurements using a novel in situ sampling device. Environ. Sci. Technol. 2003, 37, 1292–1299. (11) Shen, L.; Wania, F.; Lei, Y. D.; Teixeira, C.; Muir, D. C. G.; Bidleman, T. F. Atmospheric distribution and long-range transport behavior of organochlorine pesticides in North America. Environ. Sci. Technol. 2005, 39, 409–420. (12) Pankow, J. F. Review and comparative analysis of the theories on partitioning between the gas and aerosol particulate phases in the atmosphere. Atmos. Environ. 1987, 21, 2275–2283. (13) Whitby, K. T. The physical characteristics of sulfur aerosols. Atmos. Environ. 1978, 12, 135–159. (14) Finizio, A.; Mackay, D.; Bidleman, T.; Harner, T. Octanol-air partition coefficient as a predictor of partitioning of semi-volatile organic chemicals to aerosols. Atmos. Environ. 1997, 31, 2289– 2296. (15) Shoeib, M.; Harner, T. Using measured octanol-air partition coefficients to explain environmental partitioning of organochlorine pesticides. Environ. Toxicol. Chem. 2002, 21, 984– 990. (16) Yao, Y.; Harner, T.; Ma, J.; Tuduri, L.; Blanchard, P. Sources and occurrence of dacthal in the Canadian atmosphere. Environ. Sci. Technol. 2007, 41, 688–694. (17) Xiao, H.; Li, N.; Wania, F. Compilation, evaluation, and selection of physical-chemical property data for R-, β-, and γ-hexachlorocyclohexane. J. Chem. Eng. Data 2004, 49, 173–185. (18) Shen, L.; Wania, F. Compilation, evaluation, and selection of physical-chemical property data for organochlorine pesticides. J. Chem. Eng. Data 2005, 50, 742–768. (19) Go¨tz, C. W.; Scheringer, M.; Macleod, M.; Roth, C. M.; Hungerbu ¨ hler, K. Alternative approaches for modeling gas-particle partitioning of semivolatile organic chemicals: Model development and comparison. Environ. Sci. Technol. 2007, 41, 1272– 1278. (20) Hoff, R. M.; Strachan, W. M. J.; Sweet, C. W.; Chan, C. H.; Shackleton, M.; Bidleman, T. F.; Brice, K. A.; Burniston, D. A.; Cussion, S.; Gatz, D. F.; Harlin, K.; Schroeder, W. H. Atmospheric deposition of toxic chemicals to the Great Lakes: A review of data through 1994. Atmos. Environ. 1996, 30, 3505–3527.

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