Factors Affecting the Occurrence and Transport of ... - ACS Publications

Article pubs.acs.org/est

Factors Affecting the Occurrence and Transport of Atmospheric Organochlorines in the China Sea and the Northern Indian and South East Atlantic Oceans Rosalinda Gioia,†,‡,* Jun Li,§ Jasmin Schuster,† Yanlin Zhang,§ Gan Zhang,§ Xiangdong Li,∥ Baruch Spiro,⊥ Ravinder S. Bhatia,# Jordi Dachs,‡ and Kevin C. Jones† †

Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, U.K. Institute of Environmental Assessment and Water Research, CSIC-IDAEA C/Jordi Girona 18-26, Barcelona 08034, Catalunya, Spain § State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China ∥ Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong ⊥ Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, U.K. # Joint ALMA Observatory, Alonso de Cordova 3107, Santiago, Chile ‡

S Supporting Information *

ABSTRACT: Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are reported in 97 air samples collected on board the RV Polarstern in November 2007 from the equator to Cape Town, South Africa and the MV Oceanic II (The Scholar Ship) in January-March 2008 from Shanghai, China to Cape Verde in the Central Atlantic Ocean. The atmospheric concentrations were higher close to the coast and lower in remote regions of the Indian and South Atlantic Ocean. Groups of samples were selected in the South China Sea, Indian Ocean and South Atlantic Ocean where the relative wind direction matched the trajectory of the ship, thus all the samples had the same input of sources upwind. In these three regions the concentrations of OCPs and PCBs declined during atmospheric transport following first order kinetics. These sets of measurements provided estimates of field derived residence times (FDRTs) for individual compounds. These values were compared with predicted atmospheric residence times (PARTs) computed using a model of long-range atmospheric transport potential of POPs. The FDRTs are 5−10 times longer for the more volatile PCB congeners and TC, CC, p,p′-DDT and p,p′-DDE than the respective PARTs, while they are similar to PARTs for the less volatile compounds. Possible causes of discrepancies between PARTs and FDRTs are discussed, and revolatilization from the ocean surface seems to be the main cause for the higher values of FDRTs of the more volatile compounds in comparison with the respective PARTs.

■

INTRODUCTION The atmosphere is the major pathway for the transport of persistent organic pollutants (POPs) to remote aqueous and terrestrial ecosystems; in this sense it represents a critical compartment for the global distribution and cycling of POPs. Emissions and long-range atmospheric transport (LRAT) distribute and redistribute POPs on a global scale.1−3 Longterm studies on the atmosphere over the open ocean and other remote locations are scarce relative to those carried out on land, in particular in densely populated and industrialized areas. This may be because of the difficulties in collecting reliable, large volume air samples on board ships needed to detect POPs far from their sources. © 2012 American Chemical Society

A few studies available on North−South transects in the Atlantic ocean indicate higher concentrations in the Northern Hemisphere than in the Southern Hemisphere.4−7 These findings broadly reflect the historical and ongoing emissions of POPs from populated/industrialized regions of the Northern Hemisphere. 8 On the other hand, the remote ocean atmosphere receives an ongoing supply of POPs, presumably from the continents, which compensates for deposition and Received: Revised: Accepted: Published: 10012

May 23, 2012 July 30, 2012 August 8, 2012 August 8, 2012 dx.doi.org/10.1021/es302037t | Environ. Sci. Technol. 2012, 46, 10012−10021

Environmental Science & Technology

Article

Figure 1. Sampling locations and 120 h air mass back trajectories. The black arrows approximately indicate the areas from which samples were used to derive the FDRTs.

■

MATERIALS AND METHODS Sample Collection. Samples were collected during two scientific voyages. A total of 76 12-h day/night (6:00am-6:00 pm as day and 6:00 pm-06:00am as night) air samples were collected onboard the MV Oceanic II (The Scholar Ship, http://en.wikipedia.org/wiki/The_Scholar_Ship) from 16th January to 14th March, 2008 from Shanghai (31°N, 128°E), China to Cape Verde (15°N, 23°W), in the central Atlantic Ocean and 21 12-h day/night samples (6:00 am to 6:00 pm as day and 6:00 pm to 6:00 am as night) were also collected on board the RV Polarstern in the Southern Atlantic Ocean in November 2007 from 6°N to 23°S. On the Oceanic II−The Scholar Ship−the particle phase was collected using a quartz microfibre filter (QFF) (Grade GF/A, 20.3 × 25.4 cm, Whatman, Maidstone, England), and the gas phase was collected on a polyurethane foam (PUF) plug (Guangzhou Mingye Environmental Technology Co. Ltd., Guangzhou, China) followed by another XAD-2 resin (Amberlite, Guangzhou Mingye Environmental Technology Co. Ltd., Guangzhou, China) and an other PUF plug. An average air volume of ∼140 m3 was used. For samples collected on the RV Polarstern an average volume of 150 m3 was collected. The particle phase was collected on a Whatman glass fiber filters grade A (GFF/A) and the gas phase was trapped on PUF (Tisch Scientific) plugs. The sampler operated at about 13 m3 h−1. Details of the sampling are given in the Supporting Information (SI).

degradation of POPs from the atmosphere in agreement with the relatively constant concentration of PCBs over the Atlantic ocean reported by Gioia et al.6 Semivolatile chemicals can undergo LRAT and successive deposition and volatilization events, a process known as grass-hopping, before reaching their final sink. Therefore, atmospheric transport and deposition on the oceans surface are key processes in the cycling and ultimate fate of these compounds in the marine environments.9,10 Here we present air concentrations data for PCBs and OCPs obtained in the course of two extensive voyages in the open ocean on board the RV Polartsern from Bremerhaven (53°N, 8°E), Germany to Cape Town (33°S, 18°E), South Africa (but only samples collected from off the coast of São Tomé island, 1°S 9°W, to off the coast of South Africa, 23°S 13°E, are reported here) and an east−west transect on board the MV Oceanic II (The Scholar Ship) from Shanghai (31°N, 128°E), China to Cape Verde (15°N, 23°W) in the Central Atlantic Ocean merged as a single data set. We discuss (i) regional differences and identify potential sources of different classes of POPs; (ii) differences/similarities with land-based data from Asia, Europe, and North America;11−14 and other oceanic data15 to get insights into large-scale atmospheric phenomena and processes; (iii) the relationship between field-derived atmospheric residence times (FDRTs) and predicted atmospheric residence times (PARTs) to investigate LRAT potential and removal processes from the atmosphere. 10013

dx.doi.org/10.1021/es302037t | Environ. Sci. Technol. 2012, 46, 10012−10021


Article

Figure 2. Spatial distribution of HCB, DDT, PCBs, and HCHs (pg m−3).

Sample Treatment and Analytical Procedure. All samples were processed and analyzed as reported in Gioia et al.16 Details of preparation, quality assurance/quality control and analysis are given in the SI. Briefly, GF/A, QFFs, PUF plugs and PUF+XAD+PUFs were Soxhlet-extracted for 24 h using n-hexane. The extracts were then purified through (a) a neutral, acid and basic silica (Merck Silica 60) multilayer column, (b) a GPC (Gel permeation chromatography) column containing 6 g of Biobeads SX 3 (BIO RAD Laboratory). Prior to instrumental analysis the extracts were blown down under a gentle stream of nitrogen, solvent exchanged to n-dodecane containing internal standards. PCBs including 28/31, 52, 90/101, 118, 138, 153/132, 180, hexachlorobenzene (HCB), chlordanes, and dichlorodiphenyltrichloroethane (DDTs) were analyzed by gas chromatography−mass spectrometry (GC-MS) from Thermo Scientific DSQ Single Quadrupole using an electron impact (EI) source in selected ion mode (SIM). Analysis for hexachlorocyclohexanes (HCHs) and endosulfans was performed by GC-MS using negative chemical ionization (NCI) in SIM. Details of the instruments, temperature program and monitoring ions are reported elsewhere.17,18 Standards were obtained from the Cambridge Isotope Laboratories. Quality Assurance/Quality Control. Eight laboratory blanks (analyte solvent analyzed with the samples), eight travel

blanks (PUFs and GF/As which traveled but were not exposed to the atmosphere), and 22 field blanks (sampling media exposed to air during sample exchange) were collected and analyzed. Recovery standards were added to each of the samples to monitor procedural performance. Details of blank levels, recoveries and limit of detection are given in the SI. Back Trajectories. NOAA’s HYSPLIT model and the NCEP/NCAR Global Reanalysis19 data set were used to calculate back trajectories and atmospheric mixing height for all samples. Back trajectories (BTs) were traced for 5 days at 6 h intervals at 100 m above sea level. Three trajectories were plotted for each sampling period, namely, the starting, middle and end time. Global Orientation, Sampling Locations and Comparison with Other Studies. For the discussion, it is helpful to consider different geographical regions. These are shown in Figure 1 as the East and South China Seas, the Andaman Sea and the Bay of Bengal, the Indian Ocean, the South and North Atlantic Ocean (only between 0 and 13°N). The sampling locations represent regions of the world characterized by different global air masses in the lower atmosphere. BT analysis (Figure 1) for each sample shows that for samples collected in the Atlantic and Indian Ocean, air masses were predominantly oceanic (defined as air that has been away from the land for 3 days), whereas for the samples collected in the East and South 10014



Article

Table 1. Average, Standard Deviation (stdev), Maximum (max), and Minimum (min) Concentrations (pg m−3) for PCBs PCB 31/28

PCB 52

average stdev max min

50 21 83 15

8.2 4.2 17 1.8


19 16 51 3

3.3 2.0 6.1 1.2


23 15 47 0.69

4.2 3.8 14 0.35


7.9 9.5 87 0.57

4.1 5.1 37 1.1


10 9.5 34 0.54

2.8 2.7 11 0.55

PCB 90/101

PCB 118

PCB 153/132

East and South China Seas 7.8 4.1 2.6 1.3 11 5.5 2.5 0.9 Andaman Sea and Bay of Bengal 3.3 2.1 2.2 1.3 7 4.3 0.7 0.6 Indian Ocean 5.5 3.2 4.7 2.6 15 8.3 1.1 1 North Atlantic Ocean 3.6 3.9 2.8 3.9 17 6.3 0.41 0.26 South Atlantic Ocean 2.8 3.7 3.0 4.3 10 16 0.66 0.90

Σ7PCBs

PCB 138

PCB 180

4.1 1.4 5.6 1.3

3 1.3 4.7 0.8

0.46 0.26 1.0 0.33

77 30 122 22

1.9 1.1 4.2 0.46

0.3 0.25 0.47 0.2

0.21 0.15 0.5 0.21

30 22 73 5

5.4 5.7 21 0.22

2.8 3.4 9.5 0.36

0.43 0.27 1.1 0.27

42 29 91 1.4

4.0 2.1 7 2.3

0.6 0.5 4.0 2.3

0.28 0.3 1.76 0.22

23 21 106 1.4

2.7 3.6 15 0.29

1.8 1.5 4.4 0.78

0.35 0.14 0.62 0.18

20 19 71 0.73

Table 2. Average, Standard Deviation (stdev), Maximum (max), and Minimum (min) Concentrations (pg m−3) for OCPs αHCH

γ-HCH 72 62 238 23

αendosulfan 12 7.98 33 3

βendosulfan


10 4.28 21 4.1

11 7 22 0.51


9.9 6.9 26 1.3

27 11.4 42 3.6

111 155 489 7.6

8.9 7.7 22 3.2


8.7 12 46 7.4

189 397 1341 7.4

31 26 86 4.5

5.1 3.8 11 2.4


3.4 2 6.2 1

28.6 12.9 45 7.8

4.5 2.3 8.4 2.2

1.2 1.3 3.6 0.4


2.3 2.4 8.2 0.7

24.9 51.2 170 0.5

4 5.2 17.7 0.9

2 1.3 3.6 1.3

transchlordane

cischlordane

o,pDDE

East and South China Seas 18 11 4.3 14 9.6 2.1 55 45 7.4 7.5 3.2 1.3 Andaman Sea and Bay of Bengal 5.3 3.6 1.2 2.4 1.5 0.5 9.2 5.9 1.8 1.6 1 1.1 Indian Ocean 21 18 1.5 41 36 1.3 138 119 4.1 2.4 1.8 0.61 North Atlantic Ocean 10.1 8.4 1.4 16 15.8 NA 49.3 47.3 1.4 0.9 0.7 1.4 South Atlantic Ocean 4 3 0.9 5.1 4.3 0.8 17.6 14.9 2.4 1 0.4 0.2

China Seas, the Bay of Bengal and the Andaman Sea air masses

p,pDDE

o,pDDD

p,pDDD

o,pDDT

p,pDDT

HCB

9.3 16 65 0.92

1.1 16 65 0.92

1.1 0.33 1.3 0.85

3.3 2.49 9.2 0.36

8.2 22 80 0.64

69 25 99 22

2.2 1.7 5.2 0.2

NA NA NA NA

NA NA NA NA

2.6 2.8 9.3 0.38

2.3 2 6.7 0.27

24 11 38 4.6

1.4 1.5 3.7 0.43

NA NA NA NA

NA NA NA NA

1.6 0.88 2.9 0.34

0.2 0.25 0.85 0.1

22 16 54 1

NA NA NA NA

NA NA NA NA

0.8 0.6 1.7 0.1

NA NA NA NA

NA NA NA NA

1 0.9 2.7 0.1

1 NA 1 1 0.6 0.5 1.1 0.3

NA NA NA NA 0.4 0.4 1 0.25

12.3 7.3 21.9 0.8 9.6 6.6 20.5 2

The comparison of results with those of land-based and other oceanic studies should give insights into changing levels and distributions of OCPs and PCBs over the different geographical regions. This comparison must be done cautiously, because they only reflect short sampling periods and therefore specific

were partly continental (northeast China, Bangladesh, Northeast part of India and Philippines) and partly oceanic (Figure 1). 10015



Article

are highly influenced by the historical usage of technical HCH and Lindane (containing 99% of γ-HCH) and the environmental behaviors of the two isomers. In the present study the average ratio ranges from 0.050 to 0.65 over the East and South China Seas and the Andaman Sea and the Bay of Bengal, and from 0.010 to 0.36 over the Atlantic and the Indian Oceans. These ratios are similar to those measured in the Tibetan atmosphere (0.080−0.48),28 lower than those measured on Mt. Everest29 in India12 or in the Arctic.26,30 This is probably reflecting atmospheric transport of lindane identified by a greater proportion of γ-HCH or fresh input of lindane. In fact the ratios are different from those reported by Iwata et al.,15 over the same oceanic regions, which ranged from 1 to 5 (close to the typical technical mixture) indicating changes in the historical use of technical HCH. DDTs. The highest Σ6-DDT concentrations were found close to land over the East and South China Seas (2.2−89 pg m−3), while the lowest was measured in the Atlantic Ocean (0.17−5.3 pg m−3) (Figure 2). These concentrations were in the same range as those reported by Iwata et al.,15 with the exception of the Bay of Bengal where their reported levels are 25 times higher than those reported in the present study. Although DDT is registered and currently produced in India,31 levels have decreased in the last two decades. Generally, the DDT concentrations in the present study are lower than those measured in mainland China32 and India,31 presumably due to travel distance and dispersion of DDTs from the air mass origin. The average DDT/DDE ratio was 1 in most of the samples collected in the Bay of Bengal and the Andaman Sea where back trajectories (Figure 1) show air masses coming partly from the coastal area of India. Iwata et al.,15 reported a higher proportion of p,p′-DDT in the lower latitudes, including the South China Sea and the Bay of Bengal (ratio ranged from ∼5−20). The data presented here indicate a decline of the ratio in all geographical regions due to the phasing out and ongoing atmospheric degradation of DDTs; however, a ratio >1 in the Bay of Bengal still indicates fresh DDT input from India. Chlordanes. With only a few exceptions, concentrations of Σ-chlordane (trans-chlordane and cis-chlordane, TC and CC) were low and in the range of 1.4−50 pg m−3 (SI Figure SI.1). Higher values were observed at one site in the East and South China Seas, two sites in the Indian Ocean and at one site in the North Atlantic Ocean with concentrations reaching as high as 160 pg m−3. The Σ-chlordane concentrations were in the same range as those measured by Pozo et al.,12 at land-based sites in India and those measured by Iwata et al.15 However, Σchlordane levels are generally lower than those measured in other studies in India and China14,31 and in the same range as those measured in North America and the Great Lakes region.33,34 α- and β-Endosulfan. The highest endosulfan concentrations were observed over the Bay of Bengal, indicating that India is an important source region of this pesticide. The lowest concentrations occurred over the Atlantic Ocean. α-endosulfan was the most abundant isomer with concentrations ranging from 0.9 to 1190 pg m−3, while β-endosulfan ranged from 0.4 to 190 pg m−3 and below detection in 50% of the samples (SI Figure SI.2).

conditions such as atmospheric circulation and also the exact route of the sampling vessel and different sampling techniques which influence the sampling in the ocean. Therefore, tracing back the source areas and documenting the BTs are of great importance.

■

RESULTS AND DISCUSSION General Comments on Spatial Distribution. The concentrations of PCBs and OCPs for each sample in each region are shown in Figure 2 and in Figure SI.1 and SI.2 of the SI. Concentrations data are also reported in Table SI.1 and SI.2 in the SI. Average, standards deviations, minimum and maximum concentrations for each sampling region are reported in Tables 1 and 2. Generally, the proximity to land of the ship route in the East and South China Seas as compared to the proximity to the coast in the Indian Ocean strongly influenced the concentrations reported in the present study. This was also evidenced by the results of other compound classes such as particulate matter (PM) and trace elements measured during the same voyage20,21 on the MV Oceanic II (The Scholar Ship). Distance from sources was responsible of the low levels of PCBs and some OCPs in the Indian and the Atlantic Ocean. HCB. The highest concentrations of HCB was recorded over the East and South China Seas, while the lowest were over the South Atlantic Ocean. The average concentrations of HCB were 69 ± 25, 24 ± 11, 22 ± 16, 12 ± 7.3pg m−3 and 9.6 ± 6.6 pg m−3 over the East and South China Seas, the Bay of Bengal and the Andaman Sea, the Indian Ocean, the North and South Atlantic Ocean, respectively (Figure 2). The HCB levels in the East and South China Seas are in the same range of those reported for regions in the Northern Hemisphere such as the North Atlantic, the Arctic, Europe, and North America22−26 whereas the levels in Bay of Bengal and the Andaman Sea, the Indian Ocean, the North and South Atlantic Ocean are more similar to those reported for the South Atlantic Ocean.4 Unlike the relatively uniform distributions of HCB in Europe, North America and the Arctic,22−26 the spatial patterns of HCB during the cruise displayed distinct regional variations (Figure 2). HCHs. α-HCH and γ-HCH concentrations were the highest of the chemicals determined in most locations. The concentration of α-HCH averaged 10 ± 4 pg m−3, 9.9 ± 6.9 pg m−3, 8.7 ± 12 pg m−3, 3.4 ± 2 pg m−3 and 2.3 ± 2.4 pg m−3 over the East and South China Seas, the Bay of Bengal and the Andaman Sea, the Indian Ocean, the North and South Atlantic Ocean, respectively, whereas γ-HCH averaged 72 ± 62 pg m−3, 27 ± 11 pg m−3, 189 ± 397 pg m−3, 28 ± 12 pg m−3 and 25 ± 51 pg m−3 over the East and South China Seas, the Bay of Bengal and the Andaman Sea, the Indian Ocean, the North and South Atlantic Ocean, respectively. A few samples had unexpectedly relatively high concentration of γ-HCH which could not be explained by the back trajectories predominantly oceanic and therefore carrying relatively clean air. On average these concentrations are lower by a factor of 30−40 than those measured at land-based sites in different regions of India by Pozo et al.,12 and lower by a factor of 3−6 of those reported by Iwata et al.15 However, the concentrations are in the same range of those measured in Europe,2,11 North America2,11 in the Arctic26 and the Atlantic Ocean.27 The relative abundance of the two HCH isomers is often expressed by the α/γ ratio and it has been suggested as a marker for atmospheric transport of γ-HCH versus the technical mixture of the product (α/γ-HCH ratio ranging from 4 to 7).26 Variations of α/γ-HCH ratios in space and time 10016



Article

Table 3. (a) Atmospheric Field-Derived Residence Times (FDRTs) for PCBs (days); (b) Predicted Atmospheric Residence Times (PARTs) for PCBs (days)a (a) FDRTs (days) East and South China Seas PCB PCB PCB PCB PCB PCB PCB

PCB PCB PCB PCB PCB PCB PCB

28 52 101 118 138 153/132 180

28 52 101 118 138 153/132 180

12 ± 15 ± 61 ± 58 ± NS 20 ± 11 ±

4 6 15 20 9 10

Andaman Sea and Bay of Bengal NA NA NA NA NA NA NA (b) PARTs (days)

Indian Ocean

South Atlantic

North Atlantic

6.1 ± 2 7.4 ± 3.2 4.9 ± 1.3 6.7 ± 4.5 NS 4.2 ± 1.3 20 ± 1.5

10 ± 5 8.4 ± 3.4 8.1 ± 5.3 64 ± 24 NS 16 ± 1.6 11 ± 4.5

NA NA NA NA NA NA NA

East and South China Seas

Andaman Sea and Bay of Bengal

Indian Ocean

South Atlantic

North Atlantic

1.3 1.4 1.9 1.4 3.8 2.6 5.1

2.2 3.4 7.4 7.7 15 16 23

2.0 2.9 6.0 5.8 12 12 18

2.3 3.2 4.9 4.3 10 8 14

2.3 3.2 5.8 5.3 12 10 18

a NA = not available because there were no sampling points that satisfied the criteria of having the same air mass travelling over these locations. NS = not statistically significant. East and South China Seas: sample (9°N, 108°E to 3°N, 104°E), South Atlantic: samples (6°S, 21°W to 4°S, 9°W); Indian Ocean: samples (1.6°S, 61°E to 15°S, 43°E).

Table 4. (a) Atmospheric Field-Derived Residence Times (FDRTs) for OCPs (days); (b) Predicted Atmospheric Residence Times (PARTs) for OCPs (days)a (a) PARTs (days) East and South China Seas α-HCH γ-HCH p,p’-DDT p,p’-DDE trans-chlordane cis-chlordane HCB

α-HCH γ-HCH p,p’-DDT p,p’-DDE trans-chlordane cis-chlordane HCB

0.39 0.32 0.32 0.09 0.3 0.3 3.8

Andaman Sea and Bay of Bengal 1.24 0.75 0.55 0.1 0.43 0.43 37 (b) FDRTs (days)

Indian Ocean

South Atlantic

North Atlantic

1.25 0.81 0.54 0.1 0.4 0.4 36

0.89 0.49 0.39 0.1 0.44 0.44 26

1.29 0.83 0.5 0.1 0.45 0.45 30

South Atlantic

North Atlantic

East and South China Seas

Andaman Sea and Bay of Bengal

Indian Ocean

6 ± 5.3 5 ± 2.3 2.2 ± 1.6 2.9 ± 2.6 6.2 ± 2.3 5 ± 1.6 22 ± 9.8


1 ± 0.2 0.9 ± 0.1 1.28 ± 0.56 NS 2.5 ± 1.0 2.2 ± 1.2 0.57 ± 0.40

0.8 ± 0.6 ± NA NA 1.5 ± 1.5 ± 1.5 ±

0.1 0.1

1.2 1.1 1.3


a NA = not available because there were no sampling points that satisfied the criteria of having the same air mass travelling over these locations. NS = not statistically significant. East and South China Seas: samples (9 °N, 108 °E to 3 °N, 104 °E), South Atlantic: samples ( 6 °S, 21 °W to 9 °S, 9 °W); Indian Ocean: samples (1.6 °S, 61 °E to 15 °S, 43 °E).

Ocean had the lowest concentrations (0.73−71 pg m−3) (see Figure 2). In comparison, Σ7PCBs concentrations measured in this study are lower by a factor of ∼10 than those measured by Pozo et al.,12 in India (range 166−1364 pg m−3) and those measured by Zhang et al.,13 in Mumbai, Bangalore, and Kolkata with levels of 253, 243, and 239 pg m−3. Breivik et al.,37 reported that potential sources in the African and Asian regions of relatively high levels of PCBs may include illegal dumping of

Endosulfan has been mainly used for controlling cotton bollworm, resulting in high concentrations in cotton production areas in China and India.13,14 The average annual consumption in India and China was 3600 Mt from 1995 to 200035 and 2300 t from 1994 to 2004 respectively.36 PCBs. The samples collected had generally the highest Σ7PCBs concentrations (22−122 pg m−3) over the East and South China Seas, while samples collected in the South Atlantic 10017



Article

conditions are assumed and depend on physical factors (i.e., temperature and wind speed) and biogeochemical characteristics (i.e., biomass concentrations and organic carbon fluxes).10,44 The contribution of wet deposition to the overall depositional fluxes can be important (contributing up to 35% of the total flux) in the Intertropical Convergence Zone (ITCZ), where convective precipitation rates are high.45 However, precipitation periods did not occur during sampling in the present study so r WD was considered negligible. Dry depositional fluxes for less volatile PCBs may be the dominant deposition mechanism at midlatitudes to high latitudes (±50° to ±80°), where low temperatures and high wind speeds can enhance the relative importance of dry depositional fluxes for the less volatile PCB congeners.45 Although gas and particle phase were not analyzed separately, many studies have demonstrated that PCBs and most OCPs are predominantly found in the gas-phase.46−48 Therefore, since these samples were collected in the intertropical environments (30°N to 30°S), where the temperatures are relatively high (>25 °C), rDD was also considered to be negligible. Equation 2 was then expressed as follows:

PCB-containing wastes with release via volatilization and uncontrolled burning, and the storage and breakup of old ships. Therefore, emissions of some industrial organic contaminants may be decreasing faster in former use regions (due to emission reductions combined with uncontrolled export), at the expense of regions receiving these substances as obsolete products and wastes.38 There has been extensive (international) media coverage of the serious environmental contamination and danger to public health stemming from the improper disposal of e-waste in Asia and especially in China.38 However, the mean concentration of Σ7PCBs in the present study is in the same range as those measured in European background sites (2−121 pg m−3).39 A comparison with the oceanic data set of Iwata et al.,15 cannot be performed because Iwata reported only the sum of 40 PCB congeners. Atmospheric Residence Times. The atmospheric residence time, τa (days), gives an indication of the potential for LRAT, as well as persistence in terms of average life expectancy of the pollutants in the atmosphere. It is defined as the transport time needed for the concentration of a pollutant to decrease to 1/e, 37% of the initial concentration. Field Derived Residence Times (FDRTs). Groups of samples were selected for which the air concentrations decline followed a first order kinetics decline over time40−43 in which for the respective sampling period the relative wind direction matched the trajectory of the ship, thus all the samples had the same input of sources upwind. The first order kinetics decline is given in the following equation: C = C0 e−kt or ln C = ln C0 − kt

τa =

(1)

where C is the concentration of the compound in air (ng m ), C0 is the concentration at time 0, k is the rate constant, and t is time (days). t is the estimated travel time needed for atmospheric transport from one sampling point to the other using the measured relative wind speed and relative wind direction (see SI Figure SI.3 for an example of the graphical derivation of k). The atmospheric residence times (days) can then be calculated as τa = 1/k; these are shown in Table 3a for PCBs and Table 4a for OCPs. Eight samples collected from the East and South China Sea, eight samples from the Indian Ocean and 13 samples from the South Atlantic satisfied the above-mentioned conditions. These sets of measurements provided estimates of f ield derived residence times (FDRTs) for individual compounds. PARTs. Predicted atmospheric residence times (PARTs) were computed using a model of long-range atmospheric transport potential of POPs based on physical-chemical factors.10By assuming that the compounds are well mixed in the atmospheric boundary layer (ABL [m]) of height h (m), the atmospheric residence time can be parametrized as reported by Jurado et al.10 Therefore: 1 rAWabs + rDD + rWD + rOHdegr − rAWvol

rAWabs + rOHdegr − rAWvol

(3)

PARTs are shown in Table 3b for PCBs and 4b for OCPs. Comparison of FDRTs and PARTs in the Three Test Areas. The FDRTs were calculated for congeners PCB 28, 52, 101, 118, 138, 153, and 180, HCB, TC, CC, p,p′-DDT, p,p′-DDE and α- and γ-HCH for the sampling sites satisfying the criterion of having the wind direction matched the trajectory of the ship and the same input of sources upwind. These test areas are located between 9°N, 108°E and 3°N, 104°E in the South China Sea, 1.6°S, 61°E and 15°S, 43°E in the Indian Ocean and 7°S, 22°W and 0°, 13°W in South Atlantic Ocean. Of a total of 42 linear regressions between gas phase concentrations and time (eq 1), 35 were statistically significant at 95% confidence level (p < 0.05). Generally, the FDRTs were shorter for the more volatile and longer for the less volatile chemicals, with the exception of PCB 101 and 118 in the East and South China Seas and PCB 118 in the South Ocean for which the residence times were significantly higher than PCB 180 (61, 58, and 64 days respectively. See SI Figure SI.4). The FDRTs were also considerably different between geographical regions; for PCBs, those measured in the East and South China Seas and the South Atlantic were higher by a factor of 2 to 5 than those measured in the Indian Ocean, whereas for OCPs, atmospheric residence times measured in East and South China Seas were higher by a factor 2−5 than those measured in the South Atlantic and the Indian Ocean. The comparison of FDRTs and PARTs in the three test areas shows that the FDRTs are higher by a factor of 5−10 for the more volatile PCB congeners (PCB 28 and 52), whereas they are in the same range as the PARTs values for the less volatile PCBs (PCB 153 and 180) for all three test areas (see SI Figure SI.4 and Figure SI.5). For TC, CC, p,p′-DDT and p,p′-DDE, the FDRTs were always higher than the PARTs values for the three test areas. A different scenario appears for α- and γ-HCHs for which predictions are in good agreement with the FDRTs in the Indian and South Atlantic Ocean, while the FDRTs are higher than the PARTs by a factor of 2−10 in the East and South China Seas.

−3

τa =

1

(2)

where rAWabs, rDD, rWD, rOHdegr, rAWvol are the removal rates (day−1) due to diffusive absorption, dry deposition, wet deposition, degradation with OH radicals and diffusive volatilization, respectively. These removal rates can be derived from fluxes parametrization as described elsewhere,10,44 which account for air-deep water transport of POPs due to settling fluxes of POPs bound to organic matter. The removal rates are independent of the gas phase concentrations when steady state 10018



Article

Possible Causes of Differences between the FDRTs and PARTs. Trophic Status of the Ocean. The three selected sampling regions in the present study are oligotrophic areas of the oceans with chlorophyll concentrations ranging from 0.09 to 2 mg m−3 during the sampling period. Therefore, the biological pump is not an efficient removal mechanism of POPs, especially the less hydrophobic ones, from the atmosphere to the deep ocean as it is in high latitude regions.49 In fact, estimation of the rAWabs and rAWvol from the model reveal that air and water are very close to equilibrium conditions, with rAWabs and rAWvol being very similar. If the role of the biological pump was important, atmospheric POPs would be sequestered from the atmosphere decreasing their atmospheric concentrations. Therefore the FDRTs would be shorter than those in the present study. Overestimation of the OH Radical Degradation in the Model Computation. The overestimation of the OH degradation rates (rOHdegr) in the atmosphere in the modeling approach used would lead to estimation of shorter PARTs. COH were estimated from atmospheric temperature with the following equation from Beyer et al.50 COH = (0.5 + 4 × (T − 273))105

between the FDRTs and the PARTs is larger for the more volatile compounds. On the contrary the atmospheric concentrations of the less volatile chemicals for which the OH degradation is less important will be controlled by air− water exchange and the biological pump (factors considered in the model above) leading to similar FDRTs and PARTs for the less volatile compounds. The volatilization from subtropical oligotrophic oceans was not accounted for in eq 3 of the model, thus underestimating the atmospheric residence times (lower PARTs than FDRTs, Tables 3 and 4). Re-emission from surface waters of the remote ocean has already been observed in the Southern Atlantic for dibenzo-p-dioxins and furans (PCDD/Fs) by Nizzetto et al.55 and in the Atlantic and Pacific Ocean for PCBs in various studies.56,57 It is unclear from the present and previous studies55−57 whether the revolatilization observed in the subtropical ocean is due to a temporary or to a permanent condition of the ocean and to what extent potential new sources of PCBs37,38 and OCPs12,14,29−31,57,58 in Asia and Africa affect the reservoir capacity of POPs in the remote or adjacent ocean.

■

(4)

ASSOCIATED CONTENT

S Supporting Information *

Clearly, it is expected that atmospheric degradation would be greater in warmer periods of the day and during day-time when the [OH] would be at its maximum. Indeed, analysis based on mass balance modeling in combination with field observations of PCBs suggests that the OH reaction may be significantly overestimated by models.51 Therefore, the rate rOHdegr could be corrected by a factor of 0.5 to account for this overestimation; however, even with this correction the FDRTs are still higher than the PARTs for low chlorinated PCB congeners, TC, CC, p,p′-DDT and p,p′-DDE. Conversely, α- and γ-HCHs, with relatively low Kow (4.2) and relatively low Henry’s Law constants (4.85 Pa-m3/mol), will prefer to be more in the surface water and are not efficiently depleted in the water column by settling fluxes of organic matter. However, it has been shown that degradation in the surface water is also an important removal process for α- and γ- HCHs52 and surface waters degradation may compensate for the atmospheric degradation maintaining air and water close to equilibrium as predicted by the model, leading to similar FDRTs and PARTs for the South Atlantic and Indian oceans. Revolatilization from the Ocean Surface Water. Revolatilization of POPs from the ocean surface waters can resupply the atmosphere representing a removal mechanism for POPs in the oligotrophic subtropical waters and a secondary source of these compounds to the atmosphere. Revolatilization of POPs can be due to different factors depending on whether sampling sites are located in coastal regions or the oligotrophic oceanic gyres. In the South China Sea the revolatilization of POPs from the ocean could be influenced by enhanced concentrations in seawater driven by runoff/riverine inputs as usually found in coastal regions.47,53 This revolatilization can be favored as well by atmospheric degradation due to OH radicals. The OH radical degradation can play a major role in the remote oligotrophic regions of the oceanic gyres (south Atlantic and Indian ocean) by removing the more volatile compounds efficiently enough to modify the air−water concentration gradients and therefore cause a reverse of the air−water exchange flux (calculated using a modified version of the Whitman two-film resistance model54) to net volatilization from the surface ocean to air. In fact the difference

Tables of full data sets for PCBs and OCPs concentrations in the air, distribution maps of the compounds and figures of the residence times. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*Phone: +34-93-400-6169; e-mail: [email protected]. es. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the Chinese Academy of Sciences (No. KZCX2-YW-GJ02), Natural Science Foundation of China (NSFC) (Nos. 40821003 and 41073080), and the Research Grants Council (RGC) of the Hong Kong SAR Government (PolyU 5132/08E and N_PolyU535/05). K C Jones wants to thank the support from Chinese Academy of Sciences for the Visiting Professorship for Senior Scientists. We are grateful for the National Oceanic and Atmospheric Administration’s Air Resources Laboratory to provide the HYSPLIT transport model and the READY website (http://www.arl.noaa.gov/ ready. html). We would like to thank Melanie Hanvey for help during the sampling on the cruise of MV Oceanic II (The Scholar Ship), and the owner, officers and crew for provision of laboratory infrastructure and operational assistance. R. Bhatia and The Scholar Ship Program, LLC were financially supported by Royal Caribbean International.

■

REFERENCES

(1) Gioia, R.; Sweetman, A. J.; Jones, K. C. Coupling passive air sampling with emission estimates and chemical fate modeling for persistent organic pollutants (POPs): A feasibility study for northern Europe. Environ. Sci. Technol. 2007, 41 (7), 2165−2171. (2) Pozo, K.; Harner, T.; Lee, S. C.; Wania, F.; Muir, D. C. G.; Jones, K. C. Seasonally resolved concentrations of persistent organic pollutants in the global atmosphere from the first year of the GAPS study. Environ. Sci. Technol. 2009, 43 (3), 796−803.

10019



Article

(3) Schuster, J. K.; Gioia, R.; Breivik, K.; Steinnes, E.; Scheringer, M.; Jones, K. C. Trends in European background air reflect reductions in primary emissions of PCBs and PBDEs. Environ. Sci. Technol. 2010, 44 (17), 6760−6766. (4) Jaward, F. M.; Barber, J. L.; Booij, K.; Dachs, J.; Lohmann, R.; Jones, K. C. Evidence for dynamic air-water coupling and cycling of persistent organic pollutants over the open Atlantic Ocean. Environ. Sci. Technol. 2004, 38 (9), 2617−2625. (5) Jaward, F. M.; Barber, J. L.; Booij, K.; Jones, K. C. Spatial distribution of atmospheric PAHs and PCNs along a north-south Atlantic transect. Environ. Pollut. 2004, 132 (1), 173−181. (6) Gioia, R.; Nizzetto, L.; Lohmann, R.; Dachs, J.; Temme, C.; Jones, K. C. Polychlorinated biphenyls (PCBs) in air and seawater of the Atlantic Ocean: Sources, trends and processes. Environ. Sci. Technol. 2008, 42 (5), 1416−1422. (7) Nizzetto, L.; Lohmann, R.; Gioia, R.; Jahnke, A.; Temme, C.; Dachs, J.; Herckes, P.; Di Guardo, A.; Jones, K. C. PAHs in air and seawater along a North-South Atlantic transect: Trends, processes and possible sources. Environ. Sci. Technol. 2008, 42 (5), 1580−1585. (8) Breivik, K.; Sweetman, A.; Pacyna, J. M.; Jones, K. C. Towards a global historical emission inventory for selected PCB congeners−A mass balance approach-3. An update. Sci. Total Environ. 2007, 377 (2− 3), 296−307. (9) Jurado, E.; Lohmann, R.; Meijer, S.; Jones, K. C.; Dachs, J. Latitudinal and seasonal capacity of the surface oceans as a reservoir of polychlorinated biphenyls. Environ. Pollut. 2004, 128 (1−2), 149−162. (10) Jurado, E.; Dachs, J. Seasonality in the “grasshopping” and atmospheric residence times of persistent organic pollutants over the oceans. Geophys. Res. Lett. 2008, 35, L17805 DOI: 1029/ 2008GL034698. (11) Pozo, K.; Harner, T.; Wania, F.; Muir, D. C. G.; Jones, K. C.; Barrie, L. A. Toward a global network for persistent organic pollutants in air: Results from the GAPS study. Environ. Sci. Technol. 2006, 40 (16), 4867−4873. (12) Pozo, K.; Harner, T.; Lee, S. C.; Sinha, R. K.; Sengupta, B.; Loewen, M.; Geethalakshmi, V.; Kannan, K.; Volpi, V. Assessing seasonal and spatial trends of persistent organic pollutants (POPs) in Indian agricultural regions using PUF disk passive air samplers. Environ. Pollut. 2011, 159 (2), 646−653. (13) Zhang, G.; Chakraborty, P.; Li, J.; Sampathkumar, P.; Balasubramanian, T.; Kathiresan, K.; Takahashi, S.; Subramanian, A.; Tanabe, S.; Jones, K. C. 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. 2008, 42 (22), 8218−8223. (14) Liu, X.; Zhang, G.; Li, J.; Yu, L. L.; Xu, Y.; Li, X. D.; Kobara, Y.; Jones, K. C. Seasonal patterns and current sources of DDTs, chlordanes, hexachlorobenzene, and endosulfan in the atmosphere of 37 Chinese cities. Environ. Sci. Technol. 2009, 43 (5), 1316−1321. (15) Iwata, H.; Tanabe, S.; Sakal, N.; Tatsukawa, R. 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. 1993, 27 (6), 1080−1098. (16) Gioia, R.; Eckhardt, S.; Breivik, K.; Jaward, F. M.; Prieto, A.; Nizzetto, L.; Jones, K. C. Evidence for major emissions of PCBs in the West African region. Environ. Sci. Technol. 2011, 45 (4), 1349−1355. (17) Thomas, G. O.; Sweetman, A. J.; Parker, C. A.; Kreibich, H.; Jones, K. C. Development and validation of methods for the trace determination of PCBs in biological matrices. Chemos. 1998, 36 (11), 2447−2459. (18) Gouin, T.; Thomas, G. O.; Cousins, I.; Barber, J.; Mackay, D.; Jones, K. C. Air-surface exchange of polybrominated biphenyl ethers and polychlorinated biphenyls. Environ. Sci. Technol. 2002, 36 (7), 1426−1434. (19) HYSPLIT−Hybrid Single Particle Lagrangian Integrated Trajectory Model. http://ready.arl.noaa.gov/HYSPLIT.php (accessed). (20) Perez, N.; Moreno, T.; Querol, X.; Alastuey, A.; Bhatia, R.; Spiro, B.; Hanvey, M. Physicochemical variations in atmospheric

aerosols recorded at sea onboard the Atlantic-Mediterranean 2008 Scholar Ship cruise (Part I): Particle mass concentrations, size ratios, and main chemical components. Atmos. Environ. 2010, 44 (21−22), 2552−2562. (21) Moreno, T.; Perez, N.; Querol, X.; Amato, F.; Alastuey, A.; Bhatia, R.; Spiro, B.; Hanvey, M.; Gibbons, W. Physicochemical variations in atmospheric aerosols recorded at sea onboard the Atlantic-Mediterranean 2008 Scholar Ship cruise (Part II): Natural versus anthropogenic influences revealed by PM(10) trace element geochemistry. Atmos. Environ. 2010, 44 (21−22), 2563−2576. (22) Barber, J. L.; Sweetman, A. J.; van Wijk, D.; Jones, K. C. Hexachlorobenzene in the global environment: Emissions, levels, distribution, trends and processes. Sci. Total Environ. 2005, 349 (1−3), 1−44. (23) Gioia, R.; Lohmann, R.; Dachs, J.; Temme, C.; Lakaschus, S.; Schulz-Bull, D.; Hand, I.; Jones, K. C., Polychlorinated biphenyls in air and water of the North Atlantic and Arctic Ocean. J. Geophys. Res. 2008, 113, D19302, DOI: 10.1029/2007JD009750. (24) Jaward, F. M.; Farrar, N. J.; Harner, T.; Sweetman, A. J.; Jones, K. C. Passive air sampling of PCBs, PBDEs, and organochlorine pesticides across Europe. Environ. Sci. Technol. 2004, 38 (1), 34−41. (25) 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 (2), 409−420. (26) Su, Y.; Hung, H.; Blanchard, P.; Patton, G. W.; Kallenborn, R.; Konoplev, A.; Fellin, P.; Li, H.; Geen, C.; Stern, G.; Rosenberg, B.; Barrie, L. A. Spatial and seasonal variations of hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) in the Arctic atmosphere. Environ. Sci. Technol. 2006, 40 (21), 6601−6607. (27) Lakaschus, S.; Weber, K.; Wania, F.; Bruhn, R.; Schrems, O. The air-sea equilibrium and time trend of hexachlorocyclohexanes in the Atlantic Ocean between the Arctic and Antarctica. Environ. Sci. Technol. 2002, 36 (2), 138−145. (28) Li, J.; Lin, T.; Qi, S. H.; Zhang, G.; Liu, X.; Li, K. C. Evidence of local emission of organochlorine pesticides in the Tibetan plateau. Atmos. Environ. 2008, 42 (32), 7397−7404. (29) Li, J.; Zhu, T.; Wang, F.; Qiu, X. H.; Lin, W. L. Observation of organochlorine pesticides in the air of the Mt. Everest region. Ecotoxicol. Environ. Saf. 2006, 63 (1), 33−41. (30) Kutz, F. W.; Wood, P. H.; Bottimore, D. P. Organochlorine pesticides and polychlorinated biphenyls in human adipose tissue. Rev. Environ. Contamin. Toxicol. 1991, 120, 1−82. (31) Chakraborty, P.; Zhang, G.; Li, J.; Xu, Y.; Liu, X.; Tanabe, S.; Jones, K. C. Selected organochlorine pesticides in the atmosphere of major indian cities: Levels, regional versus local variations, and sources. Environ. Sci. Technol. 2010, 44 (21), 8038−8043. (32) Li, J.; Zhang, G.; Guo, L.; Xu, W. H.; Li, X. D.; Lee, C. S. L.; Ding, A.; Wang, T. Organochlorine pesticides in the atmosphere of Guangzhou and Hong Kong: Regional sources and long-range atmospheric transport. Atmos. Environ. 2007, 41 (18), 3889−3903. (33) Jantunen, L. M. M.; Bidleman, T. F.; Harner, T.; Parkhurst, W. J. Toxaphene, chlordane, and other organochlorine pesticides in Alabama air. Environ. Sci. Technol. 2000, 34 (24), 5097−5105. (34) Buehler, S. S.; Basu, I.; Hites, R. A. A comparison of PAH, PCB, and pesticide concentrations in air at two rural sites on Lake Superior. Environ. Sci. Technol. 2001, 35 (12), 2417−2422. (35) Usha, S.; Harikrishnan, V. R. Endosulfan−Fact sheet and answers to common questions 2005. www.thanal.org (accessed). (36) Jia, H.; Li, Y.-.; Wang, D.; Cai, D.; Yang, M.; Ma, J.; Hu, J. Endosulfan in China 1−gridded usage inventories. Environ. Sci. Pollut. Res. 2009, 16 (3), 295−301. (37) Breivik, K.; Gioia, R.; Chakraborty, P.; Zhang, G.; Jones, K. C. Are reductions in industrial organic contaminants emissions in rich countries achieved partly by export of toxic wastes? Environ. Sci. Technol. 2011, 45 (21), 9154−9160. (38) Ni, H. G.; Zeng, E. Y. Law Enforcement and global collaboration are the keys to containing e-waste tsunami in China. Environ. Sci. Technol. 2009, 43 (11), 3991−3994. 10020



Article

(39) Halse, A. K.; Schlabach, M.; Eckhardt, S.; Sweetman, A.; Jones, K. C.; Breivik, K. Spatial variability of POPs in European background air. Atmos. Chem. Phys. 2011, 11 (4), 1549−1564. (40) Del Vento, S.; Dachs, J.. Atmospheric occurrence and deposition of polycyclic aromatic hydrocarbons in the northeast tropical and subtropical Atlantic ocean. Environ. Sci. Technol. 2007, 41, 5608−5613. (41) Gioia, R.; Steinnes, E.; Thomas, O. G.; Meijer, N. S.; Jones, K. C. Persistent organic pollutants in European background air: Derivation of temporal and latitudinal trends. J. Environ. Monit. 2006, 8, 700−710. (42) Sweetman, A. J.; Jones, K. C. Declining PCB concentrations in the U.K. atmosphere: Evidence and possible causes. Environ. Sci. Technol. 2000, 34, 863−869. (43) 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. 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. 2005, 342, 119−144. (44) Dachs, J.; Lohmann, R.; Ockenden, W.; Mejanelle, L.; Eisenreich, S. J.; Jones, K. C. Oceanic biogeochemical controls on global dynamics of persistent organic pollutants. Environ. Sci. Technol. 2002, 36, 4229−4237. (45) Jurado, E.; Jaward, F.; Lohmann, R.; Jones, K. C.; Simoa, R.; Dachs, J. Wet deposition of persistent organic pollutants to the global ocean. Environ. Sci. Technol. 2005, 39, 2426−2435. (46) Cindoruk, S. S.; Tasdemir, Y. Dynamics of atmospheric polychlorinated biphenyls (PCBs): Concentrations, patterns, partitioning, and dry deposition level estimations in a residential site of turkey. Environ Monit Assess. 2010, 162 (1−4), 67−80. (47) García-Flor, N.; Dachs, J.; Bayona, J. M.; Albaigés, J. Surface waters are a source of polychlorinated biphenyls to the coastal atmosphere of the north-western mediterranean sea. Chemosphere 2009, 75, 1144−52. (48) Cindoruk, S. S. Atmospheric organochlorine pesticide (OCP) levels in a metropolitan city in turkey. Chemos. 2011, 82, 78−87. (49) Galbán-Malagón, C., Berrojalbiz, N, Ojeda, M. J., Dachs, J. The oceanic biological pump modulates the atmospheric transport of persistent organic pollutants to the Arctic. In Nature Commun. 2012, 3, 862, DOI: 10.1038/ncomms1858. (50) Beyer, A.; Wania, F.; Gouin, T.; Mackay, D.; Matthies, M. Temperature dependence of the characteristic travel distance. Environ. Sci. Technol. 2003, 37, 766−771. (51) Anderson, P. N.; Hites., R. A. OH radical reactions: The major removal pathway for polychlorinated biphenyls from the atmosphere. Environ. Sci. Technol. 1996, 30, 1757−1763. (52) Miguel, N.; Ormad, M. P.; Mosteo, R.; Ovelleiro, J. L. Photocatalytic degradation of pesticides in natural water: Effect of hydrogen peroxide. Int. J. Photoenergy 2012, DOI: 10.1155/2012/ 371714D. (53) Sandy, A. L.; Guo, J; Miskewitz, R. J.; McGillis, W. R.; Rodenburg, L. A. Fluxes of polychlorinated biphenyls volatilizing from the Hudson River, New York measured using micrometeorological approaches. Environ. Sci. Technol. 2012, 46, 885−91. (54) Withman, W. G. The two film theory of gas-absorption. Chem. Metall. Eng. 1923, 29, 146−148. (55) Nizzetto, L.; Lohmann, R.; Gioia, R.; Dachs, J.; Jones, K. C. Atlantic ocean surface waters buffer declining atmospheric concentrations of persistent organic pollutants. Environ. Sci. Technol. 2010, 44, 6978−6984. (56) Zhang, L.; Lohmann, R.. Cycling of PCBs and HCB in the surface ocean-lower atmosphere of the open pacific. Environ. Sci. Technol. 2010, 44, 3832−3838. (57) Lohmann, R.; Klanova, J.; Kukucka, P.; Yonis, S. Bollinger, K. PCBs and OCPs on an East-to-West transect: The importance of major currents and net volatilization for PCBs in the Atlantic Ocean. Environ. Sci. Technol., 2012, DOI:10.1021/es203459e

(58) van den Berg, H.; et al. Global trends in the use of insecticides to control vector-borne diseases. Environ. Health Perspect. 2012, 120 (4), 577−582.

10021


Factors Affecting the Occurrence and Transport of ... - ACS Publications

Recommend Documents