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Atmospheric concentrations of DDTs and chlordanes measured from Shanghai, China to the Arctic Ocean during the Third China Arctic Research Expedition in 2008
Atmospheric Environment 45 (2011) 3750e3757
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Atmospheric concentrations of DDTs and chlordanes measured from Shanghai, China to the Arctic Ocean during the Third China Arctic Research Expedition in 2008 Xiaoguo Wu a, b, c, d, James C.W. Lam c, d, Chonghuan Xia a, b, c, d, Hui Kang b, Zhouqing Xie a, b, *, Paul K.S. Lam a, c, d, ** a
Advanced Lab for Environmental Research and Technology (ALERT), University of Science and Technology of China e City University of Hong Kong (USTCeCityU), Joint Advanced Research Center, Dushu Lake Higher Education Town, SIP, Suzhou, Jiangsu, China Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China c Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong, China d State Key Lab in Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong, China b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 October 2010 Received in revised form 11 March 2011 Accepted 4 April 2011
In July to September 2008, air samples were collected aboard a research expedition icebreaker, Xuelong (Snow Dragon), under the support of the 2008 Chinese Arctic Research Expedition Program. DDTs and P chlordanes were quantified in all samples. DDTs concentrations over the whole cruise varied 3 substantially, ranging from 2.0 to 110 pg m with the average concentration of 36 31 pg m3. The fresh inputs of p,p0 -DDT and o,p0 -DDT indicated by DDT/DDE ratios and the relatively higher levels of p,p0 -DDT and o,p0 -DDT observed in East Asia and North Pacific Ocean may reflect direct transport of these compounds from the adjacent continent where continuing usage of DDT-related compounds is potentially occurring. In the Arctic, increase in sea ice melting in the summer of 2008 might result in the remobilization of DDT and enhance its atmospheric levels in this region. Air-borne pollutants arising from the fire occurring in the East Europe during the summer of 2008 might make a large contribution to higher levels of DDTs observed in the atmosphere of North Pacific Ocean and adjacent Arctic Ocean during our expedition. The ratios of o,p0 -DDT/p,p0 -DDT were higher than that in technical DDT but much lower than those observed in air samples from China, indicating the atmosphere during the present P study was likely influenced by a mixture of DDT-containing products. The concentrations of chlordanes 3 3 varied between 1.8 and 11 pg m , with an average of 5.4 2.6 pg m . Trans-chlordane (TC) and cischlordane (CC) were the most abundant among the chlordanes isomers, accounting for 40% and 39% of total chlordane for all samples. The TC/CC ratios measured in all samples were lower than in the technical mixture, reflecting the main influence by weathered chlordane. The sampling sites with low levels of TC and CC often have relatively low TC/CC ratios, and may be influenced by older air masses. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: DDT Chlordanes Marine boundary layer Arctic Ocean Atmospheric concentration
1. Introduction Organchlorine pesticides (OCPs) were extensively used from the 1950s to the 1970s (Shen et al., 2005). According to the Stockholm
* Corresponding author. Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China. Tel./fax: þ86 551 3601415. ** Corresponding author. Advanced Lab for Environmental Research and Technology (ALERT), University of Science and Technology of China e City University of Hong Kong (USTCeCityU), Joint Advanced Research Center, Dushu Lake Higher Education Town, SIP, Suzhou, Jiangsu, China. Tel.: þ86 852 2788 7681. E-mail addresses: [email protected] (Z. Xie), [email protected] (P.K.S. Lam). 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.04.012
Convention, usage of OCPs should be eliminated or reduced due to their characteristics of persistence, bioaccumulation, and toxicity to biota and humans (Stockholm Convention, 2008; Stockholm Convention, 2009a). DDTs which are a group of OCPs have been used in agriculture and applied for disease vector control, like mosquito (malaria) and tsetse fly (trypanosomiases), since 1940s (Ding et al., 2009; Qiu et al., 2004). Technical DDT, containing w85% p,p0 -DDT and 15% o,p0 -DDT had been banned in the U.S., Canada, Japan and in most of western European countries in the early 1970s (Li et al., 1999). However, DDT production in China, India, Russia, and possibly other countries continued during the 1970s and 1980s (Stockholm Convention, 2009b). Currently, DDT is being produced in three countries, India, China and DPR Korea (Stockholm
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Convention, 2009b). Recently studies have demonstrated the occurrence of high concentrations of o,p0 -DDT in air samples from China (Jaward et al., 2005; Qiu et al., 2004, 2005). Dicofol which contains relatively high levels of o,p0 -DDT as an impurity is regarded as a main contributor to ambient o,p0 -DDT (Qiu et al., 2004). Chlordanes which are another group of OCPs have been deregistered since the 1980s in most European and North American countries (Barrie et al., 1992). Technical chlordane is a mixture of at least 120 compounds, with the major constituents be transchlordane (TC, 13%), cis-chlordane (CC, 11%), trans-nonachlor (TN, 5%), and heptachlor (HEPT, 5%), along with trace amount of cisnonachlor (CN) and other species (Bidleman et al., 2002; Su et al., 2008). Chlordanes were released into the environment primarily from its application as an agricultural pesticide on corn and citrus, for home lawns and gardens and as a termiticide in house foundations (Jantunen et al., 2000). In China and Japan, chlordane can still be found as termiticide until 2008 (Stockholm Convention, 2008). Once released to the environment, DDTs and chlordanes distribute to different environmental media such as soil, water, air, atmospheric aerosols, vegetation, ice and snow, and transported by air and ocean currents from emission regions to the remote areas (Wania, 2003). Their residues can be detected in various environmental media all around the world include Arctic where they are not, or never have been used (Scheringer, 2009). Research on OCPs currently focuses on uncertainties over their ambient sources, long range atmospheric transport (LRAT)
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and fate, and air-surface exchange to improve understanding of the complex array of factors controlling air concentrations (Jaward et al., 2004b). These vary spatially and temporally and ultimately influence the global fate of OCPs. Long-range spatial surveys are necessary and effective to understand the global sources, distribution, and LRAT potential of OCPs. Several studies have been done describing the atmospheric fate of OCPs over a continental scale (Hung et al., 2005; Pozo et al., 2009; Jaward et al., 2004b). But in the open oceans, the collection of atmospheric data for the concentrations of OCPs is challenging, and reports in the literature are sparse. Although LRAT of OCPs from Eurasia has been found to have profound influence on the Arctic atmosphere (Bailey et al., 2000), only one cruise in 2003 is available regarding the LRAT of DDTs and HCHs in the North Pacific Ocean and adjacent Arctic Ocean last decade (Ding et al., 2007, 2009). Air samples were collected during the 2008 Chinese Arctic Research Expedition (CHINARE2003) from the Bohai Sea to the Arctic (33 N to 85 N) aboard the icebreaker Xuelong (Snow Dragon). The purposes of the current study are 1. to update information about DDTs and chlordanes along the cruise and compare the spatial variations in the North Pacific Ocean and remote Arctic Ocean, 2. to make a comparison with the previous monitoring data in these regions and reveal the temporal variations, and 3. to identify the sources areas and factors influencing the fate and distribution of these organic contaminants through LRAT.
Fig. 1. Origins of air masses sampled during the cruise.
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2. Methodologies 2.1. Sampling Shipboard air samples are collected from July to September 2008 during a cruise from Shanghai, China to the high-latitude Arctic (33 N to 85 N). The preparation, collection, storage and transportation of samples were accomplished according to previously established methods (Ding et al., 2007, 2009) with minor modifications: in order to avoid potential sample contamination by the ship itself, air samplers were controlled by a wind sensor to make sure the samples were collected when air was flowing from the direction of the ship’s bow. Before deployed for sampling, polyurethane foam plugs (PUFs) were pre-cleaned by Soxhlet extraction for 24 h using acetone and hexane (1:1 v/v) at ALERT laboratory, Joint Research Center of USTCeCityU, Suzhou, China. 23 PUFs were collected using two 6.5 cm diameter 6 cm height polyurethane foam plugs (PUFs). The downward PUFs were used to test any potential breakthrough. The air volumes ranged from 567 to 2916 m3 (at 0 C and 1 atm, flow rate of w1.0 m3 min1). Field/ travel blanks included three pre-cleaned PUFs, which were exposed to atmosphere over the sampling period. 2.2. Sample preparation and analytical procedure Analysis of DDTs and chlordanes was accomplished by use of previously established methods with modifications (Lam et al., 2008; Zhang et al., 2008). Briefly, PUFs were spiked with PCB 30 as surrogate standard, and then were put into pre-cleaned extraction cells and extracted by accelerated solvent extraction (ASE 200, DIONEX Inc.) using a mixture of hexane and dichloromethane (1:4 v/v) at 110 C and 1500 psi for two static
cycles with a heating time of 6 min, static time of 3 min. Extracts were evaporated to about 1 mL and then purified by elution with 80 mL of hexane and 80 mL of hexane and dichloromethane mixture (1:1 v/v) through a chromatographic column of activated silica gel (60 Å average pore size) and deactivated alumina. Elutes were spiked with 2,4,5,6-Tetrachloro-m-xylene (TCMX) and concentrated to 100 mL under a nitrogen stream. All extracts were then kept in sealed vials at 20 C prior to instrument analysis. Quantification of DDTs and chlordanes was performed using a GC (Agilent 7890A) equipped with a mass-selective detector (Agilent 5975c) in the negative chemical ionization (NCI) mode with methane used as the reactant gas. The GC column used for quantification was a DBeXLB fused silica capillary (J&W Scientific Inc., Folsom, CA) having 0.25 mm i.d. 60 m 0.25 mm film. Standard of OCPs was measured and the samples were analyzed separately in selective ion monitoring (SIM). The most abundant ions were selected for quantification and two references ions were used for confirmation of each analyte in SIM mode. 2.3. Quality control Three field blanks, six laboratory blanks, and three downward PUFs were processed to check for laboratory and field contamination. Little or no DDTs and chlordanes were detected in the blanks and downward PUFs, indicating contamination during the analysis was negligible and no breakthrough occurred during the sampling. Samples were blank corrected using the mean of the field blanks. Method detection limits (MDL) defined as mean of field blank with 3 times the standard deviations were 0.04e1.6 pg m3 for chlordane compounds, 0.1e1 pg m3 for DDTs. Surrogate recovery (n ¼ 32, including field and laboratory blanks) was 96 13% for PCB
Table 1 Method detection limits and summary of DDTs and chlordanes concentrations in the marine atmosphere from Far East Asia to the Arctic Ocean (pg m3). P Site Latitude Longitude a Temperature Sampling CC TC CN TN Chlordanes c o,p0 o,p0 - o,p0 p,p0 - p,p0 p,p0 a b Date ( N) ( C) DDE DDD DDT DDE DDD DDT 1 38.45 133.27 e 2 46.35 145.45 12.8 Far East Asia 12.8 20 54.45 163.63 14.8 3 56.3 174.26 10.7 4 58.99 176.99 10.1 5 61.32 173.27 9.5 19 61.86 177.6 12.5 6 63.14 170 9.4 7 64.22 168.32 9.5 North Pacific Ocean 11 8 66.91 166.87 3.9 9 70.45 166.05 4.2 18 70.96 170.52 2.4 10 73.18 165.53 5 11 73.56 156.01 4 Chukchi and Beaufort Sea 3.9 12 76.84 151.85 3.3 17 77.71 165.03 0.1 13 80.7 146.14 0.4 16 82.57 152.58 0.1 14 84.46 144.88 0.9 15 85.1 147.08 0.3 Central Arctic Ocean 0.5 The Entire Cruise 5.9 3 Method detection limits (pg m )
13e15 Jul. 15e17 Jul. e 12e14 Sep. 19e21 Jul. 21e23 Jul. 23e25 Jul. 9e12 Sep. 25e27 Jul. 27e29 Jul. e 31Jul.e2Aug. 2e4 Aug. 5e8 Sep. 2e4 Aug. 9e12 Aug. e 12e15 Aug. 1e5 Sep. 15e18 Aug. 28Aug.e1.Sep. 20e24 Aug. 27e28 Aug. e e
4.1 1.3 2.7 2.6 3 3.1 2.6 2.2 ND 2.2 2.3 2.7 2.3 ND 1.5 ND 1.5 2.8 ND 1.9 4.2 1.4 2.5 2.2 2.1 1.2
3.3 NDe 2.1 2.4 3.6 3.6 2.9 ND ND 2.1 2.3 3.2 2.5 ND 1.7 ND 1.8 3.2 ND 1.8 5 ND 3.1 2.5 2.2 1.6
0.25 0.07 0.16 0.13 0.08 0.09 0.1 0.09 0.05 0.08 0.089 0.1 0.09 0.08 ND 0.07 0.072 ND 0.18 0.09 0.13 0.12 0.08 0.1 0.096 0.04
2.2 0.68 1.5 1.2 1.1 1.2 1.1 0.97 0.39 0.98 0.99 1.1 0.83 0.59 0.57 0.39 0.70 1 1.3 0.74 1.4 0.8 0.67 0.99 0.96 0.37
9.9 2.9 6.4 6.3 7.8 8.0 6.7 4.1 1.8 5.4 5.7 7.1 5.7 2.1 3.8 1.9 4.1 7.0 2.9 4.5 11 3.1 6.4 5.7 5.4 e
ND 1.6 0.95 ND 1.5 2.1 2.4 0.18 0.8 1.8 1.3 6.6 0.55 0.38 0.54 0.59 1.7 0.99 1.7 0.28 0.87 0.46 ND 0.72 1.2 0.097
6.9 3 5 7 0.92 4.1 2 5.2 6.3 6.5 4.6 2.4 0.33 ND 1.03 2.5 1.3 ND 1.9 0.67 2.2 0.38 0.26 0.93 2.7 0.16
24 30 27 20 2.7 23 6.2 13 21 41 18 11 7.9 ND 8.6 3.7 6.2 ND 0.41 2.4 1.9 ND 2 1.2 11 0.16
11 7.7 9.2 5.4 4.5 16 7.9 4.3 6.2 11 7.8 13 2.8 2.4 2.9 2.8 4.8 ND 9.8 3.7 3.2 ND ND 3 5.8 1.0
1.1 2.4 1.7 17 2.6 ND 4.4 10 10 12 8.1 4.7 ND ND 3.9 5.3 2.9 ND 1.9 1.7 6.2 ND 0.73 1.9 4.3 0.47
54 25 39 15 NDe 22 6.2 3.3 ND 35 12 12 8.7 1.4 12 8.4 8.5 ND ND 2.6 11 ND 1.8 2.8 11 0.64
P DDTsd 96 70 83 64 12 67 29 36 45 110 52 50 21 4.6 29 23 25 2.2 16 11 26 2 5.3 10 36 e
a The latitude and the longitude indicate the mean location of the start and end of each sampling episode. Sample sites in longitude west and east are denote with “” and “þ” respectively. b All the samples were collected in 2008. c P Chlordanes: sum of CC, TC, CN, TN. d P DDTs: sum of p,p0 -DDT, o,p0 -DDT, p,p0 -DDE, o,p0 -DDE, p,p0 -DDD and o,p0 -DDD. e ND means the concentration is less than MDL. 1/2 MDL is assigned to the value of ND when calculating the sum of OCPs and the average concentration.
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30. The recoveries (n ¼ 3) of analytes from spiked PUF plugs were 97.8%e114.5% for chlordane compounders, 72.5%e109.5% for DDTs. 2.4. Air mass back trajectories Air mass back trajectories (BTs) were calculated to determine the origin of the air masses sampled using the HYSPLIT transport and dispersion model from the NOAA Air Resources Laboratory (Draxler and Rolph, 2003). BTs were traced for 3 days with 6 h steps at 100, 500, and 1000 m above sea level for the mean location of the start and end of one sampling episode. Air mass origins were generally indicated in Fig. 1. 3. Results and discussion To elucidate the spatial distribution of OCPs in the air samples, the sampling area was geographically separated into four different regions: East Asia (EA), North Pacific Ocean (NPO), the Chukchi and Beaufort Seas (CBS) with open water and the central Arctic Ocean (CAO) covered by seasonal or multiyear sea ice. Fig. 1 shows the air mass origins during the cruise. As the route for the EA and NPO locations was close to the coast of the Eurasian continent, air masses in this area were partly continental and partly oceanic or predominantly continental. In CBS and CAO, the air mass for some samples originated from the Arctic Ocean, while those of other samples originated from the adjacent land masses of Eurasia and North America. Noteworthy, there is some uncertainty associated with the BTs due to the changing position of the ship, the long sampling period and the different elevations calculated for the BTs. In the current study, the three elevations (100, 500 and 1000 m) represent the bottom, middle and top of atmospheric boundary layer. The BTs at the three elevations are often different. Hence, the arrows in Fig. 1 mean the average of these three levels.
P Fig. 2. Spatial distribution of DDTs in the North Pacific Ocean and the Arctic Ocean. Concentrations are displayed at the average sampling locations.
3.1.1. Spatial distribution of DDTs Two DDT isomers (p,p0 -DDT and o,p0 -DDT) and four degradation products (p,p0 -DDE, o,p0 -DDE, p,p0 -DDD and o,p0 -DDD) were P detected in 75%e90% of all the air samples (Table 1). DDTs concentrations over the whole cruise varied substantially, ranging from 2.0 to 110 pg m3 with the average concentration of 36 31 pg m3. The details of DDT-related substances in four different regions can be found in Table 1. The spatial distributions of P DDTs are shown in Fig. 2. The highest concentration was observed when the ship harbored at Nome, Alaska (site 7), while the lowest concentration was found in the CAO (site 14). A P decreasing spatial trend of mean concentrations of DDTs was observed as follow: EA, NPO, CBS and CAO with 83 19, 52 31, 25 20 and 10 9.4 pg m3, respectively. The concentrations of p,p0 -DDE, p,p0 -DDT, o,p0 -DDD and o,p0 -DDT were relatively significantly correlated with latitude, with R2 > 0.32 and p < 0.01 (Fig. 3).
the measurements made in the East China Sea in 1989e1990 (Iwata et al., 1993) (Table 2). Compared with those reported for the surrounding land in 2004, our measurements are comparable to the result of China and about twenty-eight and five times higher than those for South Korea and Japan (Jaward et al., 2005) (Table 2). P However, our data of DDTs in EA were about two to five times lower than the previous study in Qingdao, China and over the Yellow Sea in 2003 (Lammel et al., 2007) (Table 2). Relatively higher levels of p,p0 -DDT (315 pg m3) was also found at background site P of Dalian, China (Pozo et al., 2009). In the NPO, levels of DDTs during this cruise were higher by factors about 4 and 8 than those for 1989e1990 (Iwata et al., 1993) and CHINARE2003 (Ding et al., 2009) in the same area (Table 2). In the Arctic region (CBS and P CAO), levels of DDTs were about three and ten times higher than those measured by CHINARE2003 (Ding et al., 2009) and in 1989e1990 (Iwata et al., 1993) (Table 2). Compared with the monitoring data of nearby Arctic stations collected after 2000, our measurements were in the same range of those for Valkarkai but about one order of magnitude higher than those reported at Barrow, Alert and Zeppelin (Su et al., 2008; Hung et al., 2010) (Table 2).
3.1.2. Comparison with CHINARE2003 and the other previous reports P Although the concentrations of DDTs varied in different studies, our measurements were comparable to the data for global oceanic air, which ranged from below MDL to several hundred pg m3 (Ding et al., 2009; Iwata et al., 1993; Jaward et al., 2004a; Montone et al., 2005; Wurl et al., 2006). Specifically, the average P concentration of DDTs was 36 31 pg m3 during the whole cruise and was higher by a factor of 2.8 than that reported for CHINARE2003, which was 13 48 pg m3 (Ding et al., 2009). P In the EA, DDTs in our study were comparable with those of CHINARE2003 (Ding et al., 2009), but about four times higher than
3.1.3. Potential sources and fates of DDTs DDT congener patterns in different regions are presented in Fig. 4. In EA and NPO, p,p0 -DDT and o,p0 -DDT exhibited higher P concentrations (Table 1) as well as higher contributions to DDTs (Fig. 4) compared to the higher latitude areas. This finding was similar to those observed during CHINA2003 (Ding et al., 2009). In the environment, p,p0 -DDT and o,p0 -DDT will be converted to p,p0 DDE and o,p0 -DDE by UV radiation during the atmospheric transport. Hence, the ratio of DDT over DDE can be used to trace the degree of DDT decomposition and to distinguish recent and historical inputs of DDT (Ding et al., 2009). The ratios of o,p0 -DDT/ o,p0 -DDE (calculated with the average concentrations of o,p0 -DDT
3.1. DDTs
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60 o,p'-DDD
o,p'-DDT
p,p'-DDE
p,p'-DDT
Concentration(pg m-3 )
50 40 30 20 10 0 35
45
55
65
75
85
o
Latitude( N) Fig. 3. Latitudinal trends of DDTs. Correlation coefficients of DDT concentration with latitude are as follows: o,p0 -DDD, r2 ¼ 0.44 (p ¼ 0.001); o,p0 -DDT, r2 ¼ 0.47 (p ¼ 0.001); p,p0 DDE, r2 ¼ 0.32 (p ¼ 0.009); p,p0 -DDT, r2 ¼ 0.45 (p ¼ 0.001).
and o,p0 -DDE) in EA and NPO were 28 and 14; and p,p0 -DDT/p,p0 DDE in EA and NPO were 4.3 and 1.5. Commonly, DDT/DDE ratios greater than one indicate relatively fresh DDT inputs, while DDT/ DDE ratios less than one imply the presence of aged material (Pozo et al., 2006). Therefore, the fresh inputs of p,p0 -DDT and o,p0 -DDT indicated by DDT/DDE ratios in EA and NPO may reflect direct transport of these compounds from the adjacent continent where continuing usage of DDT-related compounds is potentially occurring. Although the use of technical DDT was banned in China in 1983, there is little evidence of declining DDT concentrations in the region, and high concentrations of DDTs were detected in air and sediment in China recently (Jaward et al., 2005; Lammel et al., 2007; Qiu et al., 2004). Previous estimate of emissions of semivolatile organic compounds from EA also found elevated concentrations of DDTs were attributed to air massed from China (Primbs et al., 2007). Hence there may be still local or regional emission sources for DDT in China. It’s notable that our samples were collected during summer. Relatively higher levels of DDTs were also
found in the summer samples (Lammel et al., 2007) than samples collected in autumn in China (Jaward et al., 2005) (Table 2). Those higher concentrations in summer were partly related to the enhanced volatilization of DDTs residue during the warmer seasons (Zheng et al., 2010). Application of dicofol in late spring and summer in China may be the fresh source of o,p0 -DDT (Qiu et al., 2005; Zheng et al., 2010). In addition that DDT-containing antifouling paint usage to maintain fish ship may be another fresh source of DDTs in EA and NPO (Zheng et al., 2010). In the Arctic region (CBS and CAO), DDT/DDE ratios of the present study suggested that both p,p0 -DDT (p,p0 -DDT/p,p0 DDE ¼ 1.8) and o,p0 -DDT (o,p0 -DDT/o,p0 -DDE ¼ 3.5) were fresh in CBS. Considering that use of DDTs has been banned in adjacent Canada and USA for about 40 years, these parent compounds should have degraded to other compounds (Li et al., 1999), and direct transport of these parent compounds from these two countries should be unlikely. An elevated p,p0 -DDT/p,p0 -DDE ratio was found in Russian air samples, suggesting that these might be usage
Table 2 Comparison of DDT concentrations in the present study with previous data (average concentrations and rages in pg m3). P 0 P 0 P Location Year o,p -DDTsa p,p -DDTsb DDTs East China Sea 1989e1990 North Pacific Ocean 1989e1990 Bering Sea 1989e1990 Chukchi Sea 1989e1990 Southwest Atlantic and Antarctic oceans 1995 Far East Asia 2003 North Pacific Ocean 2003 Arctic Ocean 2003 Qingdao, China 2003 Gosan, Korea 2003 2002e2003 Alert (82 300 N, 62 200 W) 0 0 Barrow(71 18 N, 156 36 W) 2002e2003 0 0 2002e2003 Valkarkai (70 05 N, 170 56 E) 2002e2003 Zeppelin(78 550 N, 11 560 E) China 2004 Japan 2004 Korea 2004 Indian Ocean 2004e2005 2004e2005 Alert (82 300 N, 62 200 W) 0 0 Zeppelin(78 55 N, 11 56 E) 2004e2006 Far East Asia 2008 North Pacific Ocean 2008 Chukchi and Beaufort Sea 2008 Central Arctic Ocean 2008 a P o,p0 -DDTs: sum of o,p0 -DDE, o,p0 -DDD and o,p0 -DDT. b P p,p0 -DDTs: sum of p,p0 -DDE, p,p0 -DDD and p,p0 -DDT.
8.3(1.3e20) 5.1(0.9e17) 0.3(<0.3e1.3) 0.9(<0.3e1.7) e 27(0.97e110) 4.7(0.55e14) 0.94(0.26e1.9) 53(<76e140) 8.3(6.6e10) 0.23(0.03e0.92) 0.34(0.07e0.75) 5.4(1.3e16) 0.37(0.02e2) 29(1.2e100) 3.8(0.36e16) 1.5(0.44e2.9) e 0.38(0.14e1.7) 0.33(0.04e2.1) 33(31e35) 24(5.1e49) 12(0.6e22) 2.8(0.84e5)
10.6(1.6e23) 6.7(1.1e22) 3.3(1.2e5.7) 5(3.5e6.6) 16(3.7e100) 38(0.74e160) 1.8(0.43e4.4) 0.65(0.26e4.2) 110(35e210) 380(190e520) 0.5(0.07e4.7) 0.74(0.14e5) 17(3.9e59) 0.86(0.07e6.8) 28(0.95e260) 14(<0.67e140) 2.9(<0.67e5.9) 10(2.5e33) 0.9(0.37e4.2) 0.84(0.10e24) 50(35e65) 28(7.4e58) 18(4.1e30) 7.7(
19(2.9e43) 12(2e39) 3.6(1.1e5.6) 5.8(3.4e8.3) e 65(1.7e270) 6.5(1e19) 1.6(0.52e5.9) 160(53e270) 390(200e530) 0.73(0.1e5.6) 1.1(0.21e5.8) 22(5.2e75) 1.2(0.09e8.8) 57(2.1e340) 16(0.36e150) 3.1(0.44e8.3) e 1.3(0.51e5.9) 1.2(0.14e26.1) 83(70e96) 52(12e110) 30(4.7e50) 11(1.9e26)
Reference Iwata et al., 1993 Iwata et al., 1993 Iwata et al., 1993 Iwata et al., 1993 Montone et al., 2005 Ding et al., 2009 Ding et al., 2009 Ding et al., 2009 Lammel et al., 2007 Lammel et al., 2007 Su et al., 2008 Su et al., 2008 Su et al., 2008 Su et al., 2008 Jaward et al., 2005 Jaward et al., 2005 Jaward et al., 2005 Wurl et al., 2006 Hung et al., 2010 Hung et al., 2010 This study This study This study This study
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The Entire Cruise
Central Arctic Ocean
Chukchi and Beaufort Seas
North Pacific Ocean
East Asia 0%
20%
40%
60%
80%
100%
Fig. 4. Congener patterns of DDTs in the entire cruise and four regions sampled.
of old stocks of DDT and related compounds in Russia (Iwata et al., 1995). Hence, Russian region may be an important source of DDT which can influence the Arctic by atmospheric transport. It is notable than an obvious increasing trend of annual air concentrations of DDTs was found at Arctic station of Zeppelin during 2004e2006 (Stockholm Convention, 2009a,b; Hung et al., 2010). A possible reason was that DDT deposited in the snow surface or stored inside the sea ice will evaporate to atmosphere when ice or snow melts (Halsall, 2004; Wania and Halsall, 2003). In the present P study, relatively higher concentration of DDTs was observed in the area within w75 N to w83 N (Site 13, 16 and 17 in CAO, Table 1) covered with seasonal and multiyear sea ice, the so-called “floating ice region” (Lu et al., 2010). Parts of the sea ice in this region were observed to melt during the cruise. Remobilization of DDT through retreat of sea ice during the cruise might contribute to the atmospheric DDTs in this region (Halsall, 2004; Wania and Halsall, 2003). Known sources of DDT include the technical type and dicofol type, both of which contain o,p0 -DDT and p,p0 -DDT. The o,p0 -DDT/ p,p0 -DDT ratios was reported to be 0.2e0.3 in technical DDT.
Nevertheless, extremely high ratios of o,p0 -DDT/p,p0 -DDT were observed in air samples from China (about 7), indicating the influence of the usage of dicofol (Qiu et al., 2005). In our study, o,p0 DDT/p,p0 -DDT ratios were 0.58, 1.6, 0.73 and 0.41 in EA, NPO, CBS and CAO, respectively. Compared to the ratio in technical DDT, results of current study were w2e5 times higher. The ratios in the present study were slightly lower to those reported for CHINARE2003 (1.1, 2.5 and 1.7 in EA, NPO and Arctic region) (Ding et al., 2009), and were more than w5 times lower than those found in China (Qiu et al., 2005). In NPO, both the measurements of CHINARE2003 and CHINARE2008 showed higher o,p0 -DDT/p,p0 -DDT ratios than in EA and Arctic region, suggesting the increasing contribution of dicofol to atmospheric DDT in this area. This phenomenon may caused by intensely transport of air masses from source region of dicofol like China during the sampling period. For the entire cruise, the atmosphere was likely influenced by a mixture of DDT-containing products. P As mentioned above, the highest concentration of DDTs was observed at Nome, Alaska (Site 7). In fact, all the samples collected near Bering Strait (Site 6e8) showed relatively higher levels than
Fig. 5. The fire maps in the summer of 2008 in Eurasia. (Color ranges from red where the fire count is low to yellow where number of fires is large).
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those others collected in NPO and CBO. Fig. 1 indicates these sites were deeply influenced by air masses from Eurasia. Previous study advanced that trans-Pacific atmospheric transport of biomass burning emissions would result in elevated pesticide levels in western North America (Genualdi et al., 2009). In order to reveal the influence of biomass burning during our sampling period, fire maps in Eurasia for the summer of 2008 are generated by using the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA’s satellites (MODIS website) (Fig. 5). Results shown in Fig. 5 indicate that there were occurrences of great fire in EA, east Siberia and east Europe during our cruise in EA and NPO Ocean in July 2008 (Site 1e7, Table 1). The scale of fire increased in the east Europe and decreased in EA and east Siberia in August. East Europe countries and Russia where agricultural activity was great had heavy historical use of DDT (Li et al., 2006). The agriculture usage of DDT in Soviet Union was about 320 kt between 1948 and 2000, and was the second highest of the world (Li and Bidleman, 2003). Biomass burning is widespread, especially during the summer time. Fire serves to clear land for shifting cultivation, to convert forests to agricultural lands, to remove dry vegetation, and to promote agricultural productivity. Biomass burning in the Eurasia may cause high volatilization of previously deposited DDTs from soil. Release of air-borne gaseous substances such as DDTs in the fire places had been streaming across Eurasia and out over the Pacific Ocean off and on for months, and had traveled around the world (Genualdi et al., 2009). Therefore the occurrences of fire in EA and east Siberia during the July of 2008 might make a significant contribution to high levels of DDTs observed in the atmosphere of NPO adjacent CBO during our expedition. 3.2. Chlordanes P The concentrations of chlordanes (sum of TC, CC, TN, CN) varied between 2.2 and 11 pg m3, with an average concentration of 5.7 2.8 pg m3. TC was detected above the MDL in 65% of all samples, while CC, CN and TN were detectable in more than 80% samples. CC and TC with the average concentrations of 2.1 1.1 and 2.2 1.3 pg m3 were the most abundant of the chlordanes isomers, accounting for about 37% and 38% of total chlordane for all P samples. The average concentrations of chlordanes in four different geographic regions were 7.2 5.7, 6.1 2.1, 4.3 2.2 and 6 3 pg m3 in EA, NPO, CBS and CAO, respectively, showing little P difference (Table 1). Highest concentration of chlordanes was found in the Sea of Japan (site 1), and the lowest concentration was in NPO (site 6) (Table 1). For site 1 in EA, relatively high concenP tration of chlordanes may due to the influence of nearby source regions where high concentrations were found recently (Jaward et al., 2005). For most samples in Arctic region, the concentrations of chlordanes were consistent with those in a previous passive air sampling study conducted in several Arctic sites (Hung et al., 2005; Pozo et al., 2006; Su et al., 2008). The average concentraP tion of chlordanes (6.4 pg m3, site 12, 13, 16 and 17 within 75 N to 83 N) in the floating ice region was slightly higher than those in NPO (5.7 pg m3), CBS (4.1 pg m3), CAO (5.7 pg m3) and the entire cruise (5.4 pg m3). Volatilization emissions from previous deposited sinks were potential source of atmospheric chlordanes in the Arctic (Su et al., 2008). Isomer ratios of TC/CC may convey information on the relative degradability and relative importance of chlordanes (Bidleman et al., 2002). The TC/CC ratio in technical chlordane mixtures is 1.17 (Jantunen et al., 2000). TC is slightly more volatile than CC (Shen and Wania, 2005), and if volatility alone were to control the atmospheric composition, the ratio at 0 C and 20 C would be expected to be 1.41 and 1.74 (Hinckley et al., 1990; Shen et al., 2005; Su et al., 2008). Fig. 6 displays the concentrations of TC and CC and
Fig. 6. Change of the air concentrations of CC, TC and TC/CC ratio over the latitudes of the sampling cruise.
TC/CC ratio along the cruise. The TC/CC ratios measured in all samples were lower than in the technical mixture, reflecting the main influence by weathered chlordane (Bidleman et al., 2002; Hung et al., 2005). Previous study had suggested that TC is lost from the atmosphere faster than CC (Bidleman et al., 2002; Shen et al., 2005), and the partitioning properties and atmospheric deposition rates of TC and CC are similar. These will cause the decrease of TC/CC ratios with the increasing distance from sources. Hence, the sampling sites with relatively low levels of TC and CC in the present study also have low TC/CC ratios (Fig. 6), and may be influenced by older air masses. 4. Conclusions This study reports atmospheric concentrations of DDTs and chlordanes measured from Shanghai, China to the Artic Ocean during the Third China Arctic Research Expedition, 2008. The data were measured over a large area of North Pacific Ocean and adjacent Arctic region, and thus provide updated information about spatial variations in these areas. Different spatial distributions were found, indicating the fate of these pollutants was influenced by their emission pattern around the world and distribution of source regions. For DDTs, relatively higher DDT/DDE ratios found along the cruise might indicate that continuing usage of different DDTrelated compounds was potentially occurring approximately in 2008. The occurrences of fire in the East Europe during the summer of 2008 might make a significant contribution to high levels of DDTs observed in the atmosphere of North Pacific Ocean and adjacent Arctic Ocean during our expedition. Ratios of o,p0 -DDT/ p,p0 -DDT were higher than that in technical DDT but lower than those in China, suggesting the atmosphere in North Pacific Ocean and adjacent Arctic area was likely influenced by a mixture of DDTcontaining products. For chlordanes, TC/CC ratios were lower than in the technical mixture, reflecting that the atmosphere in the sampling areas was mainly influenced by weathered chlordane. Acknowledgments This study was supported by grants from the National Natural Science Foundation of China (Project Nos. 41025020, 40776001), the Foundation for the Author of National Excellent Doctoral Dissertation of PR China (Grant 200354), the Chinese Academy of Sciences (Grant KZCX2-YW-QN506) and the Fundamental Research Funds for the Central Universities. The work described in this paper
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was also funded by the Area of Excellence Scheme under the University Grants Committee of the Hong Kong Special Administrative Region, China (Project No. AoE/P-04/2004), and a Hong Kong Research Grants Council (CityU 160610). Field work was supported by China Arctic and Antarctic Administration and the third China Arctic Research Expedition. References Bailey, R., Barrie, L.A., Halsall, C.J., Fellin, P., Muir, D.C.G., 2000. Atmospheric organochlorine pesticides in the western Canadian Arctic: evidence of transpacific transport. J. Geophys. Res.-Atmos 105, 11805e11811. Barrie, L.A., Gregor, D., Hargrave, B., Lake, R., Muir, D., Shearer, R., Tracey, B., Bidleman, T., 1992. Arctic contaminantsdsources, occurrence and pathways. Sci. Total Environ. 122, 1e74. Bidleman, T.F., Jantunen, L.M.M., Helm, P.A., Brorstrom-Lunden, E., Juntto, S., 2002. Chlordane enantiomers and temporal trends of chlordane isomers in arctic air. Environ. Sci. Technol. 36, 539e544. Ding, X., Wang, X.M., Wang, Q.Y., Xie, Z.Q., Xiang, C.H., Mai, B.X., Sun, L.G., 2009. Atmospheric DDTs over the North Pacific Ocean and the adjacent Arctic region: spatial distribution, congener patterns and source implication. Atmos. Environ. 43, 4319e4326. Ding, X., Wang, X.M., Xie, Z.Q., Xiang, C.H., Mai, B.X., Sun, L.G., Zheng, M., Sheng, G.Y., Fu, J.M., 2007. Atmospheric hexachlorocyclohexanes in the North Pacific Ocean and the adjacent Arctic region: spatial patterns, chiral signatures, and sea-air exchanges. Environ. Sci. Technol. 41, 5204e5209. Draxler, R.R., Rolph, G.D., 2003. HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory). Model Access via NOAA ARL READY Website. NOAA Air Resources Laboratory, Silver Spring, MD. http://www.arl.noaa.gov/ready/ hysplit4.html. Genualdi, S.A., Killin, R.K., Woods, J., Wilson, G., Schmedding, D., Simonich, S.L.M., 2009. Trans-pacific and regional atmospheric transport of polycyclic aromatic hydrocarbons and pesticides in biomass burning emissions to Western North America. Environ. Sci. Technol. 43, 1061e1066. Halsall, C.J., 2004. Investigating the occurrence of persistent organic pollutants (POPs) in the arctic: their atmospheric behaviour and interaction with the seasonal snow pack. Environ. Pollut. 128, 163e175. Hinckley, D.A., Bidleman, T.F., Foreman, W.T., Tuschall, J.R., 1990. Determination of vapor-pressures for nonpolar and semipolar organic-compounds from gaschromatographic retention data. J. Chem. Eng. Data 35, 232e237. Hung, H., Blanchard, P., Halsall, C.J., Bidleman, T.F., Stern, G.A., Fellin, P., Muir, D.C.G., Barrie, L.A., Jantunen, L.M., Helm, P.A., Ma, J., Konoplev, A., 2005. Temporal and spatial variabilities of atmospheric polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and polycyclic aromatic hydrocarbons (PAHs) in the Canadian Arctic: results from a decade of monitoring. Sci. Total Environ. 342, 119e144. Hung, H., Kallenborn, R., Breivik, K., Su, Y.S., Brorstrom-Lunden, E., Olafsdottir, K., Thorlacius, J.M., Leppanen, S., Bossi, R., Skov, H., Mano, S., Patton, G.W., Stern, G., Sverko, E., Fellin, P., 2010. Atmospheric monitoring of organic pollutants in the Arctic under the Arctic Monitoring and Assessment Programme (AMAP): 1993e2006. Sci. Total Environ. 408, 2854e2873. Iwata, H., Tanabe, S., Sakal, N., Tatsukawa, R., 1993. Distribution of persistent organochlorines in the oceanic air and surface seawater and the role of ocean on their global transport and fate. Environ. Sci. Technol. 27, 1080e1098. Iwata, H., Tanabe, S., Ueda, K., Tatsukawa, R., 1995. Persistent organochlorine residues in air, water, sediments, and soils from the lake Baikal region, Russia. Environ. Sci. Technol. 29, 792e801. Jantunen, L.M.M., Bidleman, T.F., Harner, T., Parkhurst, W.J., 2000. Toxaphene, chlordane, and other organochlorine pesticides in Alabama air. Environ. Sci. Technol. 34, 5097e5105. Jaward, F.M., Barber, J.L., Booij, K., Dachs, J., Lohmann, R., Jones, K.C., 2004a. Evidence for dynamic airewater coupling and cycling of persistent organic pollutants over the open Atlantic Ocean. Environ. Sci. Technol. 38, 2617e2625. Jaward, F.M., Farrar, N.J., Harner, T., Sweetman, A.J., Jones, K.C., 2004b. Passive air sampling of PCBs, PBDEs, and organochlorine pesticides across Europe. Environ. Sci. Technol. 38, 34e41. Jaward, T.M., Zhang, G., Nam, J.J., Sweetman, A.J., Obbard, J.P., Kobara, Y., Jones, K.C., 2005. Passive air sampling of polychlorinated biphenyls, organochlorine compounds, and polybrominated diphenyl ethers across Asia. Environ. Sci. Technol. 39, 8638e8645.
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Lam, J.C.W., Murphy, M.B., Wang, Y., Tanabe, S., Giesy, J.P., Lam, P.K.S., 2008. Risk assessment of organohalogenated compounds in water bird eggs from South China. Environ. Sci. Technol. 42, 6296e6302. Lammel, G., Ghim, Y.S., Grados, A., Gao, H.W., Huhnerfuss, H., Lohmann, R., 2007. Levels of persistent organic pollutants in air in China and over the Yellow Sea. Atmos. Environ. 41, 452e464. Li, Y.F., Bidleman, T., 2003. Usage and Emissions of Organochlorine Pesticides. Northern Contaminants Program, Hull, Quebec. Canadian Arctic Contaminants Assessment Report II. Li, Y.F., Cai, D.J., Singh, A., 1999. Historical DDT use trend in China and usage data gridding with 1/4 by 1/6 longitude/latitude resolution. Adv. Environ. Res. 2, 497e507. Li, Y.F., Zhulidov, A.V., Robarts, R.D., Korotova, L.G., Zhulidov, D.A., Gurtovaya, T.Y., Ge, L.P., 2006. Dichlorodiphenyltrichloroethane usage in the former Soviet Union. Sci. Total Environ. 357, 138e145. Lu, P., Li, Z.J., Cheng, B., Lei, R.B., Zhang, R., 2010. Sea ice surface features in Arctic summer 2008: aerial observations. Remote Sens. Environ. 114, 693e699. MODIS website. http://rapidfire.sci.gsfc.nasa.gov/. Montone, R.C., Taniguchi, S., Boian, C., Weber, R.R., 2005. PCBs and chlorinated pesticides (DDTs, HCHs and HCB) in the atmosphere of the southwest Atlantic and Antarctic oceans. Mar. Pollut. Bull. 50, 778e782. Pozo, K., Harner, T., Wania, F., Muir, D.C.G., Jones, K.C., Barrie, L.A., 2006. Toward a global network for persistent organic pollutants in air: results from the GAPS study. Environ. Sci. Technol. 40, 4867e4873. Pozo, K., Harner, T., Lee, S.C., Wania, F., Muir, D.C.G., Jones, K.C., 2009. Seasonally resolved concentrations of persistent organic pollutants in the global atmosphere from the first year of the GAPS study. Environ. Sci. Technol. 43, 796e803. Primbs, T., Simonich, S., Schmedding, D., Wilson, G., Jaffe, D., Takami, A., Kato, S., Hatakeyama, S., Kajii, Y., 2007. Atmospheric outflow of anthropogenic semivolatile organic compounds from East Asia in spring 2004. Environ. Sci. Technol. 41, 3551e3558. Qiu, X.H., Zhu, T., Jing, L., Pan, H.S., Li, Q.L., Miao, G.F., Gong, J.C., 2004. Organochlorine pesticides in the air around the Taihu Lake, China. Environ. Sci. Technol. 38, 1368e1374. Qiu, X.H., Zhu, T., Yao, B., Hu, J.X., Hu, S.W., 2005. Contribution of dicofol to the current DDT pollution in China. Environ. Sci. Technol. 39, 4385e4390. Scheringer, M., 2009. Long-range transport of organic chemicals in the environment. Environ. Toxicol. Chem. 28, 677e690. Shen, L., Wania, F., 2005. Compilation, evaluation, and selection of physicalechemical property data for organochlorine pesticides. J. Chem. Eng. Data 50, 742e768. Shen, L., Wania, F., Lei, Y.D., Teixeira, C., Muir, D.C.G., Bidleman, T.F., 2005. Atmospheric distribution and long-range transport behavior of organochlorine pesticides in north America. Environ. Sci. Technol. 39, 409e420. Stockholm Convention, 2008. Global Monitoring Plan for Persistent Organic Pollutants, First Regional Monitoring Report: Asia-Pacific Region. Stockholm Convention, 2009a. Global Monitoring Plan for Persistent Organic Pollutants, First Regional Monitoring Report: Western Europe and Other States Group (WEOG) Region. Stockholm Convention, 2009b. Report of the Expert Group on Assessment of the Production and Use of DDT and its Alternatives for Disease Vector Control. Su, Y.S., Hung, H.L., Blanchard, P., Patton, G.W., Kallenborn, R., Konoplev, A., Fellin, P., Li, H., Geen, C., Stern, G., Rosenberg, B., Barrie, L.A., 2008. A circumpolar perspective of atmospheric organochlorine pesticides (OCPs): results from six Arctic monitoring stations in 2000e2003. Atmos. Environ. 42, 4682e4698. Wania, F., 2003. Assessing the potential of persistent organic chemicals for longrange transport and accumulation in polar regions. Environ. Sci. Technol. 37, 1344e1351. Wania, F., Halsall, C., 2003. Air/Snow Exchange of Persistent Organic Pollutants. Northern Contaminants Program, Hull, Quebec. Canadian Arctic Contaminants Assessment Report II185e190. Wurl, O., Potter, J.R., Obbard, J.P., Durville, C., 2006. Persistent organic pollutants in the equatorial atmosphere over the open Indian Ocean. Environ. Sci. Technol. 40, 1454e1461. Zhang, G., Chakraborty, P., Li, J., Sampathkumar, P., Balasubramanian, T., Kathiresan, K., Takahashi, S., Subramanian, A., Tanabe, S., Jones, K.C., 2008. Passive atmospheric sampling of organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers in urban, rural, and wetland sites along the coastal length of India. Environ. Sci. Technol. 42, 8218e8223. Zheng, X.Y., Chen, D.Z., Liu, X.D., Zhou, Q.F., Liu, Y., Yang, W., Jiang, G.B., 2010. Spatial and seasonal variations of organochlorine compounds in air on an urbanerural transect across Tianjin, China. Chemosphere 78, 92e98.
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Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv
Atmospheric concentrations of DDTs and chlordanes measured from Shanghai, China to the Arctic Ocean during the Third China Arctic Research Expedition in 2008 Xiaoguo Wu a, b, c, d, James C.W. Lam c, d, Chonghuan Xia a, b, c, d, Hui Kang b, Zhouqing Xie a, b, *, Paul K.S. Lam a, c, d, ** a
Advanced Lab for Environmental Research and Technology (ALERT), University of Science and Technology of China e City University of Hong Kong (USTCeCityU), Joint Advanced Research Center, Dushu Lake Higher Education Town, SIP, Suzhou, Jiangsu, China Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China c Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong, China d State Key Lab in Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong, China b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 October 2010 Received in revised form 11 March 2011 Accepted 4 April 2011
In July to September 2008, air samples were collected aboard a research expedition icebreaker, Xuelong (Snow Dragon), under the support of the 2008 Chinese Arctic Research Expedition Program. DDTs and P chlordanes were quantified in all samples. DDTs concentrations over the whole cruise varied 3 substantially, ranging from 2.0 to 110 pg m with the average concentration of 36 31 pg m3. The fresh inputs of p,p0 -DDT and o,p0 -DDT indicated by DDT/DDE ratios and the relatively higher levels of p,p0 -DDT and o,p0 -DDT observed in East Asia and North Pacific Ocean may reflect direct transport of these compounds from the adjacent continent where continuing usage of DDT-related compounds is potentially occurring. In the Arctic, increase in sea ice melting in the summer of 2008 might result in the remobilization of DDT and enhance its atmospheric levels in this region. Air-borne pollutants arising from the fire occurring in the East Europe during the summer of 2008 might make a large contribution to higher levels of DDTs observed in the atmosphere of North Pacific Ocean and adjacent Arctic Ocean during our expedition. The ratios of o,p0 -DDT/p,p0 -DDT were higher than that in technical DDT but much lower than those observed in air samples from China, indicating the atmosphere during the present P study was likely influenced by a mixture of DDT-containing products. The concentrations of chlordanes 3 3 varied between 1.8 and 11 pg m , with an average of 5.4 2.6 pg m . Trans-chlordane (TC) and cischlordane (CC) were the most abundant among the chlordanes isomers, accounting for 40% and 39% of total chlordane for all samples. The TC/CC ratios measured in all samples were lower than in the technical mixture, reflecting the main influence by weathered chlordane. The sampling sites with low levels of TC and CC often have relatively low TC/CC ratios, and may be influenced by older air masses. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: DDT Chlordanes Marine boundary layer Arctic Ocean Atmospheric concentration
1. Introduction Organchlorine pesticides (OCPs) were extensively used from the 1950s to the 1970s (Shen et al., 2005). According to the Stockholm
* Corresponding author. Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China. Tel./fax: þ86 551 3601415. ** Corresponding author. Advanced Lab for Environmental Research and Technology (ALERT), University of Science and Technology of China e City University of Hong Kong (USTCeCityU), Joint Advanced Research Center, Dushu Lake Higher Education Town, SIP, Suzhou, Jiangsu, China. Tel.: þ86 852 2788 7681. E-mail addresses: [email protected] (Z. Xie), [email protected] (P.K.S. Lam). 1352-2310/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.04.012
Convention, usage of OCPs should be eliminated or reduced due to their characteristics of persistence, bioaccumulation, and toxicity to biota and humans (Stockholm Convention, 2008; Stockholm Convention, 2009a). DDTs which are a group of OCPs have been used in agriculture and applied for disease vector control, like mosquito (malaria) and tsetse fly (trypanosomiases), since 1940s (Ding et al., 2009; Qiu et al., 2004). Technical DDT, containing w85% p,p0 -DDT and 15% o,p0 -DDT had been banned in the U.S., Canada, Japan and in most of western European countries in the early 1970s (Li et al., 1999). However, DDT production in China, India, Russia, and possibly other countries continued during the 1970s and 1980s (Stockholm Convention, 2009b). Currently, DDT is being produced in three countries, India, China and DPR Korea (Stockholm
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Convention, 2009b). Recently studies have demonstrated the occurrence of high concentrations of o,p0 -DDT in air samples from China (Jaward et al., 2005; Qiu et al., 2004, 2005). Dicofol which contains relatively high levels of o,p0 -DDT as an impurity is regarded as a main contributor to ambient o,p0 -DDT (Qiu et al., 2004). Chlordanes which are another group of OCPs have been deregistered since the 1980s in most European and North American countries (Barrie et al., 1992). Technical chlordane is a mixture of at least 120 compounds, with the major constituents be transchlordane (TC, 13%), cis-chlordane (CC, 11%), trans-nonachlor (TN, 5%), and heptachlor (HEPT, 5%), along with trace amount of cisnonachlor (CN) and other species (Bidleman et al., 2002; Su et al., 2008). Chlordanes were released into the environment primarily from its application as an agricultural pesticide on corn and citrus, for home lawns and gardens and as a termiticide in house foundations (Jantunen et al., 2000). In China and Japan, chlordane can still be found as termiticide until 2008 (Stockholm Convention, 2008). Once released to the environment, DDTs and chlordanes distribute to different environmental media such as soil, water, air, atmospheric aerosols, vegetation, ice and snow, and transported by air and ocean currents from emission regions to the remote areas (Wania, 2003). Their residues can be detected in various environmental media all around the world include Arctic where they are not, or never have been used (Scheringer, 2009). Research on OCPs currently focuses on uncertainties over their ambient sources, long range atmospheric transport (LRAT)
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and fate, and air-surface exchange to improve understanding of the complex array of factors controlling air concentrations (Jaward et al., 2004b). These vary spatially and temporally and ultimately influence the global fate of OCPs. Long-range spatial surveys are necessary and effective to understand the global sources, distribution, and LRAT potential of OCPs. Several studies have been done describing the atmospheric fate of OCPs over a continental scale (Hung et al., 2005; Pozo et al., 2009; Jaward et al., 2004b). But in the open oceans, the collection of atmospheric data for the concentrations of OCPs is challenging, and reports in the literature are sparse. Although LRAT of OCPs from Eurasia has been found to have profound influence on the Arctic atmosphere (Bailey et al., 2000), only one cruise in 2003 is available regarding the LRAT of DDTs and HCHs in the North Pacific Ocean and adjacent Arctic Ocean last decade (Ding et al., 2007, 2009). Air samples were collected during the 2008 Chinese Arctic Research Expedition (CHINARE2003) from the Bohai Sea to the Arctic (33 N to 85 N) aboard the icebreaker Xuelong (Snow Dragon). The purposes of the current study are 1. to update information about DDTs and chlordanes along the cruise and compare the spatial variations in the North Pacific Ocean and remote Arctic Ocean, 2. to make a comparison with the previous monitoring data in these regions and reveal the temporal variations, and 3. to identify the sources areas and factors influencing the fate and distribution of these organic contaminants through LRAT.
Fig. 1. Origins of air masses sampled during the cruise.
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2. Methodologies 2.1. Sampling Shipboard air samples are collected from July to September 2008 during a cruise from Shanghai, China to the high-latitude Arctic (33 N to 85 N). The preparation, collection, storage and transportation of samples were accomplished according to previously established methods (Ding et al., 2007, 2009) with minor modifications: in order to avoid potential sample contamination by the ship itself, air samplers were controlled by a wind sensor to make sure the samples were collected when air was flowing from the direction of the ship’s bow. Before deployed for sampling, polyurethane foam plugs (PUFs) were pre-cleaned by Soxhlet extraction for 24 h using acetone and hexane (1:1 v/v) at ALERT laboratory, Joint Research Center of USTCeCityU, Suzhou, China. 23 PUFs were collected using two 6.5 cm diameter 6 cm height polyurethane foam plugs (PUFs). The downward PUFs were used to test any potential breakthrough. The air volumes ranged from 567 to 2916 m3 (at 0 C and 1 atm, flow rate of w1.0 m3 min1). Field/ travel blanks included three pre-cleaned PUFs, which were exposed to atmosphere over the sampling period. 2.2. Sample preparation and analytical procedure Analysis of DDTs and chlordanes was accomplished by use of previously established methods with modifications (Lam et al., 2008; Zhang et al., 2008). Briefly, PUFs were spiked with PCB 30 as surrogate standard, and then were put into pre-cleaned extraction cells and extracted by accelerated solvent extraction (ASE 200, DIONEX Inc.) using a mixture of hexane and dichloromethane (1:4 v/v) at 110 C and 1500 psi for two static
cycles with a heating time of 6 min, static time of 3 min. Extracts were evaporated to about 1 mL and then purified by elution with 80 mL of hexane and 80 mL of hexane and dichloromethane mixture (1:1 v/v) through a chromatographic column of activated silica gel (60 Å average pore size) and deactivated alumina. Elutes were spiked with 2,4,5,6-Tetrachloro-m-xylene (TCMX) and concentrated to 100 mL under a nitrogen stream. All extracts were then kept in sealed vials at 20 C prior to instrument analysis. Quantification of DDTs and chlordanes was performed using a GC (Agilent 7890A) equipped with a mass-selective detector (Agilent 5975c) in the negative chemical ionization (NCI) mode with methane used as the reactant gas. The GC column used for quantification was a DBeXLB fused silica capillary (J&W Scientific Inc., Folsom, CA) having 0.25 mm i.d. 60 m 0.25 mm film. Standard of OCPs was measured and the samples were analyzed separately in selective ion monitoring (SIM). The most abundant ions were selected for quantification and two references ions were used for confirmation of each analyte in SIM mode. 2.3. Quality control Three field blanks, six laboratory blanks, and three downward PUFs were processed to check for laboratory and field contamination. Little or no DDTs and chlordanes were detected in the blanks and downward PUFs, indicating contamination during the analysis was negligible and no breakthrough occurred during the sampling. Samples were blank corrected using the mean of the field blanks. Method detection limits (MDL) defined as mean of field blank with 3 times the standard deviations were 0.04e1.6 pg m3 for chlordane compounds, 0.1e1 pg m3 for DDTs. Surrogate recovery (n ¼ 32, including field and laboratory blanks) was 96 13% for PCB
Table 1 Method detection limits and summary of DDTs and chlordanes concentrations in the marine atmosphere from Far East Asia to the Arctic Ocean (pg m3). P Site Latitude Longitude a Temperature Sampling CC TC CN TN Chlordanes c o,p0 o,p0 - o,p0 p,p0 - p,p0 p,p0 a b Date ( N) ( C) DDE DDD DDT DDE DDD DDT 1 38.45 133.27 e 2 46.35 145.45 12.8 Far East Asia 12.8 20 54.45 163.63 14.8 3 56.3 174.26 10.7 4 58.99 176.99 10.1 5 61.32 173.27 9.5 19 61.86 177.6 12.5 6 63.14 170 9.4 7 64.22 168.32 9.5 North Pacific Ocean 11 8 66.91 166.87 3.9 9 70.45 166.05 4.2 18 70.96 170.52 2.4 10 73.18 165.53 5 11 73.56 156.01 4 Chukchi and Beaufort Sea 3.9 12 76.84 151.85 3.3 17 77.71 165.03 0.1 13 80.7 146.14 0.4 16 82.57 152.58 0.1 14 84.46 144.88 0.9 15 85.1 147.08 0.3 Central Arctic Ocean 0.5 The Entire Cruise 5.9 3 Method detection limits (pg m )
13e15 Jul. 15e17 Jul. e 12e14 Sep. 19e21 Jul. 21e23 Jul. 23e25 Jul. 9e12 Sep. 25e27 Jul. 27e29 Jul. e 31Jul.e2Aug. 2e4 Aug. 5e8 Sep. 2e4 Aug. 9e12 Aug. e 12e15 Aug. 1e5 Sep. 15e18 Aug. 28Aug.e1.Sep. 20e24 Aug. 27e28 Aug. e e
4.1 1.3 2.7 2.6 3 3.1 2.6 2.2 ND 2.2 2.3 2.7 2.3 ND 1.5 ND 1.5 2.8 ND 1.9 4.2 1.4 2.5 2.2 2.1 1.2
3.3 NDe 2.1 2.4 3.6 3.6 2.9 ND ND 2.1 2.3 3.2 2.5 ND 1.7 ND 1.8 3.2 ND 1.8 5 ND 3.1 2.5 2.2 1.6
0.25 0.07 0.16 0.13 0.08 0.09 0.1 0.09 0.05 0.08 0.089 0.1 0.09 0.08 ND 0.07 0.072 ND 0.18 0.09 0.13 0.12 0.08 0.1 0.096 0.04
2.2 0.68 1.5 1.2 1.1 1.2 1.1 0.97 0.39 0.98 0.99 1.1 0.83 0.59 0.57 0.39 0.70 1 1.3 0.74 1.4 0.8 0.67 0.99 0.96 0.37
9.9 2.9 6.4 6.3 7.8 8.0 6.7 4.1 1.8 5.4 5.7 7.1 5.7 2.1 3.8 1.9 4.1 7.0 2.9 4.5 11 3.1 6.4 5.7 5.4 e
ND 1.6 0.95 ND 1.5 2.1 2.4 0.18 0.8 1.8 1.3 6.6 0.55 0.38 0.54 0.59 1.7 0.99 1.7 0.28 0.87 0.46 ND 0.72 1.2 0.097
6.9 3 5 7 0.92 4.1 2 5.2 6.3 6.5 4.6 2.4 0.33 ND 1.03 2.5 1.3 ND 1.9 0.67 2.2 0.38 0.26 0.93 2.7 0.16
24 30 27 20 2.7 23 6.2 13 21 41 18 11 7.9 ND 8.6 3.7 6.2 ND 0.41 2.4 1.9 ND 2 1.2 11 0.16
11 7.7 9.2 5.4 4.5 16 7.9 4.3 6.2 11 7.8 13 2.8 2.4 2.9 2.8 4.8 ND 9.8 3.7 3.2 ND ND 3 5.8 1.0
1.1 2.4 1.7 17 2.6 ND 4.4 10 10 12 8.1 4.7 ND ND 3.9 5.3 2.9 ND 1.9 1.7 6.2 ND 0.73 1.9 4.3 0.47
54 25 39 15 NDe 22 6.2 3.3 ND 35 12 12 8.7 1.4 12 8.4 8.5 ND ND 2.6 11 ND 1.8 2.8 11 0.64
P DDTsd 96 70 83 64 12 67 29 36 45 110 52 50 21 4.6 29 23 25 2.2 16 11 26 2 5.3 10 36 e
a The latitude and the longitude indicate the mean location of the start and end of each sampling episode. Sample sites in longitude west and east are denote with “” and “þ” respectively. b All the samples were collected in 2008. c P Chlordanes: sum of CC, TC, CN, TN. d P DDTs: sum of p,p0 -DDT, o,p0 -DDT, p,p0 -DDE, o,p0 -DDE, p,p0 -DDD and o,p0 -DDD. e ND means the concentration is less than MDL. 1/2 MDL is assigned to the value of ND when calculating the sum of OCPs and the average concentration.
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30. The recoveries (n ¼ 3) of analytes from spiked PUF plugs were 97.8%e114.5% for chlordane compounders, 72.5%e109.5% for DDTs. 2.4. Air mass back trajectories Air mass back trajectories (BTs) were calculated to determine the origin of the air masses sampled using the HYSPLIT transport and dispersion model from the NOAA Air Resources Laboratory (Draxler and Rolph, 2003). BTs were traced for 3 days with 6 h steps at 100, 500, and 1000 m above sea level for the mean location of the start and end of one sampling episode. Air mass origins were generally indicated in Fig. 1. 3. Results and discussion To elucidate the spatial distribution of OCPs in the air samples, the sampling area was geographically separated into four different regions: East Asia (EA), North Pacific Ocean (NPO), the Chukchi and Beaufort Seas (CBS) with open water and the central Arctic Ocean (CAO) covered by seasonal or multiyear sea ice. Fig. 1 shows the air mass origins during the cruise. As the route for the EA and NPO locations was close to the coast of the Eurasian continent, air masses in this area were partly continental and partly oceanic or predominantly continental. In CBS and CAO, the air mass for some samples originated from the Arctic Ocean, while those of other samples originated from the adjacent land masses of Eurasia and North America. Noteworthy, there is some uncertainty associated with the BTs due to the changing position of the ship, the long sampling period and the different elevations calculated for the BTs. In the current study, the three elevations (100, 500 and 1000 m) represent the bottom, middle and top of atmospheric boundary layer. The BTs at the three elevations are often different. Hence, the arrows in Fig. 1 mean the average of these three levels.
P Fig. 2. Spatial distribution of DDTs in the North Pacific Ocean and the Arctic Ocean. Concentrations are displayed at the average sampling locations.
3.1.1. Spatial distribution of DDTs Two DDT isomers (p,p0 -DDT and o,p0 -DDT) and four degradation products (p,p0 -DDE, o,p0 -DDE, p,p0 -DDD and o,p0 -DDD) were P detected in 75%e90% of all the air samples (Table 1). DDTs concentrations over the whole cruise varied substantially, ranging from 2.0 to 110 pg m3 with the average concentration of 36 31 pg m3. The details of DDT-related substances in four different regions can be found in Table 1. The spatial distributions of P DDTs are shown in Fig. 2. The highest concentration was observed when the ship harbored at Nome, Alaska (site 7), while the lowest concentration was found in the CAO (site 14). A P decreasing spatial trend of mean concentrations of DDTs was observed as follow: EA, NPO, CBS and CAO with 83 19, 52 31, 25 20 and 10 9.4 pg m3, respectively. The concentrations of p,p0 -DDE, p,p0 -DDT, o,p0 -DDD and o,p0 -DDT were relatively significantly correlated with latitude, with R2 > 0.32 and p < 0.01 (Fig. 3).
the measurements made in the East China Sea in 1989e1990 (Iwata et al., 1993) (Table 2). Compared with those reported for the surrounding land in 2004, our measurements are comparable to the result of China and about twenty-eight and five times higher than those for South Korea and Japan (Jaward et al., 2005) (Table 2). P However, our data of DDTs in EA were about two to five times lower than the previous study in Qingdao, China and over the Yellow Sea in 2003 (Lammel et al., 2007) (Table 2). Relatively higher levels of p,p0 -DDT (315 pg m3) was also found at background site P of Dalian, China (Pozo et al., 2009). In the NPO, levels of DDTs during this cruise were higher by factors about 4 and 8 than those for 1989e1990 (Iwata et al., 1993) and CHINARE2003 (Ding et al., 2009) in the same area (Table 2). In the Arctic region (CBS and P CAO), levels of DDTs were about three and ten times higher than those measured by CHINARE2003 (Ding et al., 2009) and in 1989e1990 (Iwata et al., 1993) (Table 2). Compared with the monitoring data of nearby Arctic stations collected after 2000, our measurements were in the same range of those for Valkarkai but about one order of magnitude higher than those reported at Barrow, Alert and Zeppelin (Su et al., 2008; Hung et al., 2010) (Table 2).
3.1.2. Comparison with CHINARE2003 and the other previous reports P Although the concentrations of DDTs varied in different studies, our measurements were comparable to the data for global oceanic air, which ranged from below MDL to several hundred pg m3 (Ding et al., 2009; Iwata et al., 1993; Jaward et al., 2004a; Montone et al., 2005; Wurl et al., 2006). Specifically, the average P concentration of DDTs was 36 31 pg m3 during the whole cruise and was higher by a factor of 2.8 than that reported for CHINARE2003, which was 13 48 pg m3 (Ding et al., 2009). P In the EA, DDTs in our study were comparable with those of CHINARE2003 (Ding et al., 2009), but about four times higher than
3.1.3. Potential sources and fates of DDTs DDT congener patterns in different regions are presented in Fig. 4. In EA and NPO, p,p0 -DDT and o,p0 -DDT exhibited higher P concentrations (Table 1) as well as higher contributions to DDTs (Fig. 4) compared to the higher latitude areas. This finding was similar to those observed during CHINA2003 (Ding et al., 2009). In the environment, p,p0 -DDT and o,p0 -DDT will be converted to p,p0 DDE and o,p0 -DDE by UV radiation during the atmospheric transport. Hence, the ratio of DDT over DDE can be used to trace the degree of DDT decomposition and to distinguish recent and historical inputs of DDT (Ding et al., 2009). The ratios of o,p0 -DDT/ o,p0 -DDE (calculated with the average concentrations of o,p0 -DDT
3.1. DDTs
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60 o,p'-DDD
o,p'-DDT
p,p'-DDE
p,p'-DDT
Concentration(pg m-3 )
50 40 30 20 10 0 35
45
55
65
75
85
o
Latitude( N) Fig. 3. Latitudinal trends of DDTs. Correlation coefficients of DDT concentration with latitude are as follows: o,p0 -DDD, r2 ¼ 0.44 (p ¼ 0.001); o,p0 -DDT, r2 ¼ 0.47 (p ¼ 0.001); p,p0 DDE, r2 ¼ 0.32 (p ¼ 0.009); p,p0 -DDT, r2 ¼ 0.45 (p ¼ 0.001).
and o,p0 -DDE) in EA and NPO were 28 and 14; and p,p0 -DDT/p,p0 DDE in EA and NPO were 4.3 and 1.5. Commonly, DDT/DDE ratios greater than one indicate relatively fresh DDT inputs, while DDT/ DDE ratios less than one imply the presence of aged material (Pozo et al., 2006). Therefore, the fresh inputs of p,p0 -DDT and o,p0 -DDT indicated by DDT/DDE ratios in EA and NPO may reflect direct transport of these compounds from the adjacent continent where continuing usage of DDT-related compounds is potentially occurring. Although the use of technical DDT was banned in China in 1983, there is little evidence of declining DDT concentrations in the region, and high concentrations of DDTs were detected in air and sediment in China recently (Jaward et al., 2005; Lammel et al., 2007; Qiu et al., 2004). Previous estimate of emissions of semivolatile organic compounds from EA also found elevated concentrations of DDTs were attributed to air massed from China (Primbs et al., 2007). Hence there may be still local or regional emission sources for DDT in China. It’s notable that our samples were collected during summer. Relatively higher levels of DDTs were also
found in the summer samples (Lammel et al., 2007) than samples collected in autumn in China (Jaward et al., 2005) (Table 2). Those higher concentrations in summer were partly related to the enhanced volatilization of DDTs residue during the warmer seasons (Zheng et al., 2010). Application of dicofol in late spring and summer in China may be the fresh source of o,p0 -DDT (Qiu et al., 2005; Zheng et al., 2010). In addition that DDT-containing antifouling paint usage to maintain fish ship may be another fresh source of DDTs in EA and NPO (Zheng et al., 2010). In the Arctic region (CBS and CAO), DDT/DDE ratios of the present study suggested that both p,p0 -DDT (p,p0 -DDT/p,p0 DDE ¼ 1.8) and o,p0 -DDT (o,p0 -DDT/o,p0 -DDE ¼ 3.5) were fresh in CBS. Considering that use of DDTs has been banned in adjacent Canada and USA for about 40 years, these parent compounds should have degraded to other compounds (Li et al., 1999), and direct transport of these parent compounds from these two countries should be unlikely. An elevated p,p0 -DDT/p,p0 -DDE ratio was found in Russian air samples, suggesting that these might be usage
Table 2 Comparison of DDT concentrations in the present study with previous data (average concentrations and rages in pg m3). P 0 P 0 P Location Year o,p -DDTsa p,p -DDTsb DDTs East China Sea 1989e1990 North Pacific Ocean 1989e1990 Bering Sea 1989e1990 Chukchi Sea 1989e1990 Southwest Atlantic and Antarctic oceans 1995 Far East Asia 2003 North Pacific Ocean 2003 Arctic Ocean 2003 Qingdao, China 2003 Gosan, Korea 2003 2002e2003 Alert (82 300 N, 62 200 W) 0 0 Barrow(71 18 N, 156 36 W) 2002e2003 0 0 2002e2003 Valkarkai (70 05 N, 170 56 E) 2002e2003 Zeppelin(78 550 N, 11 560 E) China 2004 Japan 2004 Korea 2004 Indian Ocean 2004e2005 2004e2005 Alert (82 300 N, 62 200 W) 0 0 Zeppelin(78 55 N, 11 56 E) 2004e2006 Far East Asia 2008 North Pacific Ocean 2008 Chukchi and Beaufort Sea 2008 Central Arctic Ocean 2008 a P o,p0 -DDTs: sum of o,p0 -DDE, o,p0 -DDD and o,p0 -DDT. b P p,p0 -DDTs: sum of p,p0 -DDE, p,p0 -DDD and p,p0 -DDT.
8.3(1.3e20) 5.1(0.9e17) 0.3(<0.3e1.3) 0.9(<0.3e1.7) e 27(0.97e110) 4.7(0.55e14) 0.94(0.26e1.9) 53(<76e140) 8.3(6.6e10) 0.23(0.03e0.92) 0.34(0.07e0.75) 5.4(1.3e16) 0.37(0.02e2) 29(1.2e100) 3.8(0.36e16) 1.5(0.44e2.9) e 0.38(0.14e1.7) 0.33(0.04e2.1) 33(31e35) 24(5.1e49) 12(0.6e22) 2.8(0.84e5)
10.6(1.6e23) 6.7(1.1e22) 3.3(1.2e5.7) 5(3.5e6.6) 16(3.7e100) 38(0.74e160) 1.8(0.43e4.4) 0.65(0.26e4.2) 110(35e210) 380(190e520) 0.5(0.07e4.7) 0.74(0.14e5) 17(3.9e59) 0.86(0.07e6.8) 28(0.95e260) 14(<0.67e140) 2.9(<0.67e5.9) 10(2.5e33) 0.9(0.37e4.2) 0.84(0.10e24) 50(35e65) 28(7.4e58) 18(4.1e30) 7.7(
19(2.9e43) 12(2e39) 3.6(1.1e5.6) 5.8(3.4e8.3) e 65(1.7e270) 6.5(1e19) 1.6(0.52e5.9) 160(53e270) 390(200e530) 0.73(0.1e5.6) 1.1(0.21e5.8) 22(5.2e75) 1.2(0.09e8.8) 57(2.1e340) 16(0.36e150) 3.1(0.44e8.3) e 1.3(0.51e5.9) 1.2(0.14e26.1) 83(70e96) 52(12e110) 30(4.7e50) 11(1.9e26)
Reference Iwata et al., 1993 Iwata et al., 1993 Iwata et al., 1993 Iwata et al., 1993 Montone et al., 2005 Ding et al., 2009 Ding et al., 2009 Ding et al., 2009 Lammel et al., 2007 Lammel et al., 2007 Su et al., 2008 Su et al., 2008 Su et al., 2008 Su et al., 2008 Jaward et al., 2005 Jaward et al., 2005 Jaward et al., 2005 Wurl et al., 2006 Hung et al., 2010 Hung et al., 2010 This study This study This study This study
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The Entire Cruise
Central Arctic Ocean
Chukchi and Beaufort Seas
North Pacific Ocean
East Asia 0%
20%
40%
60%
80%
100%
Fig. 4. Congener patterns of DDTs in the entire cruise and four regions sampled.
of old stocks of DDT and related compounds in Russia (Iwata et al., 1995). Hence, Russian region may be an important source of DDT which can influence the Arctic by atmospheric transport. It is notable than an obvious increasing trend of annual air concentrations of DDTs was found at Arctic station of Zeppelin during 2004e2006 (Stockholm Convention, 2009a,b; Hung et al., 2010). A possible reason was that DDT deposited in the snow surface or stored inside the sea ice will evaporate to atmosphere when ice or snow melts (Halsall, 2004; Wania and Halsall, 2003). In the present P study, relatively higher concentration of DDTs was observed in the area within w75 N to w83 N (Site 13, 16 and 17 in CAO, Table 1) covered with seasonal and multiyear sea ice, the so-called “floating ice region” (Lu et al., 2010). Parts of the sea ice in this region were observed to melt during the cruise. Remobilization of DDT through retreat of sea ice during the cruise might contribute to the atmospheric DDTs in this region (Halsall, 2004; Wania and Halsall, 2003). Known sources of DDT include the technical type and dicofol type, both of which contain o,p0 -DDT and p,p0 -DDT. The o,p0 -DDT/ p,p0 -DDT ratios was reported to be 0.2e0.3 in technical DDT.
Nevertheless, extremely high ratios of o,p0 -DDT/p,p0 -DDT were observed in air samples from China (about 7), indicating the influence of the usage of dicofol (Qiu et al., 2005). In our study, o,p0 DDT/p,p0 -DDT ratios were 0.58, 1.6, 0.73 and 0.41 in EA, NPO, CBS and CAO, respectively. Compared to the ratio in technical DDT, results of current study were w2e5 times higher. The ratios in the present study were slightly lower to those reported for CHINARE2003 (1.1, 2.5 and 1.7 in EA, NPO and Arctic region) (Ding et al., 2009), and were more than w5 times lower than those found in China (Qiu et al., 2005). In NPO, both the measurements of CHINARE2003 and CHINARE2008 showed higher o,p0 -DDT/p,p0 -DDT ratios than in EA and Arctic region, suggesting the increasing contribution of dicofol to atmospheric DDT in this area. This phenomenon may caused by intensely transport of air masses from source region of dicofol like China during the sampling period. For the entire cruise, the atmosphere was likely influenced by a mixture of DDT-containing products. P As mentioned above, the highest concentration of DDTs was observed at Nome, Alaska (Site 7). In fact, all the samples collected near Bering Strait (Site 6e8) showed relatively higher levels than
Fig. 5. The fire maps in the summer of 2008 in Eurasia. (Color ranges from red where the fire count is low to yellow where number of fires is large).
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those others collected in NPO and CBO. Fig. 1 indicates these sites were deeply influenced by air masses from Eurasia. Previous study advanced that trans-Pacific atmospheric transport of biomass burning emissions would result in elevated pesticide levels in western North America (Genualdi et al., 2009). In order to reveal the influence of biomass burning during our sampling period, fire maps in Eurasia for the summer of 2008 are generated by using the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA’s satellites (MODIS website) (Fig. 5). Results shown in Fig. 5 indicate that there were occurrences of great fire in EA, east Siberia and east Europe during our cruise in EA and NPO Ocean in July 2008 (Site 1e7, Table 1). The scale of fire increased in the east Europe and decreased in EA and east Siberia in August. East Europe countries and Russia where agricultural activity was great had heavy historical use of DDT (Li et al., 2006). The agriculture usage of DDT in Soviet Union was about 320 kt between 1948 and 2000, and was the second highest of the world (Li and Bidleman, 2003). Biomass burning is widespread, especially during the summer time. Fire serves to clear land for shifting cultivation, to convert forests to agricultural lands, to remove dry vegetation, and to promote agricultural productivity. Biomass burning in the Eurasia may cause high volatilization of previously deposited DDTs from soil. Release of air-borne gaseous substances such as DDTs in the fire places had been streaming across Eurasia and out over the Pacific Ocean off and on for months, and had traveled around the world (Genualdi et al., 2009). Therefore the occurrences of fire in EA and east Siberia during the July of 2008 might make a significant contribution to high levels of DDTs observed in the atmosphere of NPO adjacent CBO during our expedition. 3.2. Chlordanes P The concentrations of chlordanes (sum of TC, CC, TN, CN) varied between 2.2 and 11 pg m3, with an average concentration of 5.7 2.8 pg m3. TC was detected above the MDL in 65% of all samples, while CC, CN and TN were detectable in more than 80% samples. CC and TC with the average concentrations of 2.1 1.1 and 2.2 1.3 pg m3 were the most abundant of the chlordanes isomers, accounting for about 37% and 38% of total chlordane for all P samples. The average concentrations of chlordanes in four different geographic regions were 7.2 5.7, 6.1 2.1, 4.3 2.2 and 6 3 pg m3 in EA, NPO, CBS and CAO, respectively, showing little P difference (Table 1). Highest concentration of chlordanes was found in the Sea of Japan (site 1), and the lowest concentration was in NPO (site 6) (Table 1). For site 1 in EA, relatively high concenP tration of chlordanes may due to the influence of nearby source regions where high concentrations were found recently (Jaward et al., 2005). For most samples in Arctic region, the concentrations of chlordanes were consistent with those in a previous passive air sampling study conducted in several Arctic sites (Hung et al., 2005; Pozo et al., 2006; Su et al., 2008). The average concentraP tion of chlordanes (6.4 pg m3, site 12, 13, 16 and 17 within 75 N to 83 N) in the floating ice region was slightly higher than those in NPO (5.7 pg m3), CBS (4.1 pg m3), CAO (5.7 pg m3) and the entire cruise (5.4 pg m3). Volatilization emissions from previous deposited sinks were potential source of atmospheric chlordanes in the Arctic (Su et al., 2008). Isomer ratios of TC/CC may convey information on the relative degradability and relative importance of chlordanes (Bidleman et al., 2002). The TC/CC ratio in technical chlordane mixtures is 1.17 (Jantunen et al., 2000). TC is slightly more volatile than CC (Shen and Wania, 2005), and if volatility alone were to control the atmospheric composition, the ratio at 0 C and 20 C would be expected to be 1.41 and 1.74 (Hinckley et al., 1990; Shen et al., 2005; Su et al., 2008). Fig. 6 displays the concentrations of TC and CC and
Fig. 6. Change of the air concentrations of CC, TC and TC/CC ratio over the latitudes of the sampling cruise.
TC/CC ratio along the cruise. The TC/CC ratios measured in all samples were lower than in the technical mixture, reflecting the main influence by weathered chlordane (Bidleman et al., 2002; Hung et al., 2005). Previous study had suggested that TC is lost from the atmosphere faster than CC (Bidleman et al., 2002; Shen et al., 2005), and the partitioning properties and atmospheric deposition rates of TC and CC are similar. These will cause the decrease of TC/CC ratios with the increasing distance from sources. Hence, the sampling sites with relatively low levels of TC and CC in the present study also have low TC/CC ratios (Fig. 6), and may be influenced by older air masses. 4. Conclusions This study reports atmospheric concentrations of DDTs and chlordanes measured from Shanghai, China to the Artic Ocean during the Third China Arctic Research Expedition, 2008. The data were measured over a large area of North Pacific Ocean and adjacent Arctic region, and thus provide updated information about spatial variations in these areas. Different spatial distributions were found, indicating the fate of these pollutants was influenced by their emission pattern around the world and distribution of source regions. For DDTs, relatively higher DDT/DDE ratios found along the cruise might indicate that continuing usage of different DDTrelated compounds was potentially occurring approximately in 2008. The occurrences of fire in the East Europe during the summer of 2008 might make a significant contribution to high levels of DDTs observed in the atmosphere of North Pacific Ocean and adjacent Arctic Ocean during our expedition. Ratios of o,p0 -DDT/ p,p0 -DDT were higher than that in technical DDT but lower than those in China, suggesting the atmosphere in North Pacific Ocean and adjacent Arctic area was likely influenced by a mixture of DDTcontaining products. For chlordanes, TC/CC ratios were lower than in the technical mixture, reflecting that the atmosphere in the sampling areas was mainly influenced by weathered chlordane. Acknowledgments This study was supported by grants from the National Natural Science Foundation of China (Project Nos. 41025020, 40776001), the Foundation for the Author of National Excellent Doctoral Dissertation of PR China (Grant 200354), the Chinese Academy of Sciences (Grant KZCX2-YW-QN506) and the Fundamental Research Funds for the Central Universities. The work described in this paper
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