Environ. Sci. Technol. 1996, 30, 2294-2304
Seasonal Changes and Relations between Levels of Organochlorines in Arctic Ambient Air: First Results of an All-Year-Round Monitoring Program at Ny-Ålesund, Svalbard, Norway M I C H A E L O E H M E , * ,† JOHN-ERIK HAUGEN,‡ AND MARTIN SCHLABACH‡ Institute for Organic Chemistry, University of Basel, St. Johanns-Ring 19, CH-4056 Basel, Switzerland, and Norwegian Institute for Air Research, P.O. Box 100, N-2007 Kjeller, Norway
The influence of seasonal changes and long-range transport on levels of selected polychlorinated compounds was studied by taking ambient air samples at Ny-Ålesund (78°55′ N, 11°56′ E), Svalbard, Norway, once a week from March to October 1993 and with 48-h sampling intervals from November to December 1993. Polychlorinated pesticides such as chlordanes, hexachlorocyclohexanes (HCH), and DDT compounds as well as polychlorinated biphenyl (PCB) congeners were quantified by high-resolution gas chromatography combined with high- or low-resolution mass spectrometry. Due to levels being often in the subpicogram per cubic meter range, a comprehensive quality control program was applied. This first continuous measurement campaign in the Norwegian Arctic showed a clear seasonal variation of transchlordane and cis-nonachlor. Circumpolar trajectories allowed identification of long-range transport from different source regions. The temporal concentration profiles of compounds with different industrial and agricultural sources allowed us to confirm such transport episodes and to differentiate between the influence of industrial and agricultural areas. A significant correlation was found between concentrations of some chlordane congeners, R- and γ-HCH isomers, and the most volatile PCB congeners. No seasonal change of the PCB concentrations was found, indicating that a weekly average temperature of 5-8 °C during summer is not large enough for a measurable revolatilization of already deposited material. * Corresponding author fax: +41-61-267 11 04; e-mail address:
[email protected]. † University of Basel. ‡ Norwegian Institute for Air Research.
2294
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 30, NO. 7, 1996
Introduction Until the end of the 1970s, the Arctic was considered as a region being too remote to be the subject of any pollution by persistent organic compounds. In fact, early measurements were started in this pristine area to establish global background concentrations (1). However, the monitoring work of the last decade revealed that concentrations of organochlorines found in Arctic biota such as seals (2) as well as in aborigines (3) living in this region are surprisingly high. Long-range atmospheric transport has been identified as the main transfer route to the Arctic (4). At present, no clear trend of a decline is visible in the observed levels (2, 5) though the emissions of persistent organochlorines have been reduced and the use of most chlorinated pesticides is banned in the industrialized countries of the northern hemisphere. Therefore, the monitoring of levels in biota and air as the main transport medium is still of high importance. So far, a number of studies of levels of polychlorinated compounds in ambient air have been published. A selection is represented by refs 6-10. Mainly polychlorinated biphenyls (PCB) and polychlorinated pesticides such as hexachlorocyclohexanes (HCH), chlordane, and compounds from the DDT group were determined. The measurement period was normally limited to a period of a few months. Only Hoff et al. (6) published results of an ambient air monitoring program where one-three samples per week were taken over a 14-month period. To their and our knowledge, this was the first data set that covered such a long period. It clearly showed a seasonal variation of ambient air levels of some organochlorines. This is not surprising since air concentrations are influenced by temperature-dependent factors such as volatilization, deposition, and transport as well as degradation (11-13). Earlier measurements in the European Arctic at NyÅlesund, Svalbard, in 1981-1984 also showed seasonal concentration changes of HCH and chlordane congeners (14). However, long-range air transport from more polluted source areas might lead to short and significant concentration changes in Arctic air that will bias average levels found during short measuring periods of a few weeks. Even in a very remote region such as the Arctic, concentration changes of more than a factor of 5-10 can occur during a long-range transport episode (14, 15). Several long-range air transport episodes from both Europe and North America were identified in 1984 (14) and 1992 (15) by correlating significant concentration increases with calculated air back trajectories for the period of interest. Former measurements of ambient air in the Norwegian Arctic covered just a few months of the year, and only a few compounds such as HCH isomers, hexachlorobenzene, and cis/trans-chlordane were determined (14, 16, 17). PCBs were only occasionally measured during 1981-1984. In 1992, a short measurement campaign was carried out during a few weeks during winter/spring and summer to evaluate an improved analysis methodology including a congenerspecific PCB analysis. This measurement period underscored also the importance of a comprehensive quality control system, which was introduced simultaneously. During earlier campaigns, quite often single samples or whole sample series had to be rejected due to elevated
S0013-936X(95)00701-2 CCC: $12.00
1996 American Chemical Society
TABLE 1
Comparison of Annual Mean, Minimum, and Maximum Values for PCB and Selected Pesticides with Mean Blank Values and Lower Limit of Determination (LOD)a blank values (pg/m3)
sample concentrations (pg/m3)
mean x
SD
LOD
annual mean
min
max
samples below lod
PCB-28(+16) PCB-31 PCB-52 PCB-101 PCB-105 PCB-118 PCB-138 PCB-153 PCB-156 PCB-180
0.27 0.31 0.23 0.25 0.022 0.030 0.105 0.068 0.007 0.027
0.14 0.21 0.16 0.17 0.016 0.031 0.083 0.051 0.007 0.025
0.69 0.94 0.71 0.42 0.070 0.123 0.35 0.22 0.028 0.102
4.30 2.97 2.47 1.28 0.20 0.53 0.54 0.61 0.051 0.16
0.98 0.67 0.77 0.39 0.067 0.19 0.22 0.22 0.015 0.061
46.6 31.0 23.5 10.4 1.18 2.93 3.15 3.61 0.30 0.99
0 4 0 1 1 0 18 0 13 18
R-HCH γ-HCH trans-chlordane cis-chlordane trans-nonachlor cis-nonachlor
0.12 0.10 0.011 0.020 0.017 0.007
0.069 0.075 0.009 0.0160 0.010 0.007
0.32 0.33 0.038 0.068 0.047 0.028
6.8 3.3 0.16 0.42 0.35 0.031
203 38.3 1.35 2.00 1.60 0.39
0 0 0 0 0 0
congener no.
a
77.4 14.4 0.53 1.09 0.85 0.18
The number of samples that were below the LOD is also given. The total number of samples was between 49 and 51. SD, standard deviation.
method or field blanks (16, 17). The experience from this campaign allowed us to improve the method and quality control scheme further. In 1993, a continuous ambient air monitoring program at Ny-Ålesund, Svalbard, was established as part of the Arctic Monitoring and Assessment Programme (AMAP). The aims of this still on-going campaign can be summarized as follows: (a) Determination of average seasonal levels of selected PCB congeners (nos. 28, 31, 52, 101, 105, 118, 138, 153, 156, 180), hexachlorobenzene, R-HCH, γ-HCH, cis/trans-chlordane, and cis/trans-nonachlor as well as p,p′- and o,p′ isomers of DDT, DDE, DDD. (b) Comparison of found concentrations with other measuring stations in the Arctic established by Canada. (c) Evaluation of the number and influence of longrange air transport episodes on monthly and seasonal averages. (d) Study of seasonal variations of levels and concentration ratios. (e) Identification of a possible correlation between concentration levels of compounds as well as temperature. (f) Long-term experience with the applied quality control and measuring technique. This paper presents the results of the weekly measurements of polychlorinated compounds at Ny-Ålesund, Svalbard, Norway, in 1993 and the data interpretation according to some of the aspects given above. The applied sampling and measuring technique is described, or reference is made to earlier publications. The applied quality control system was in accordance with the recommendations of the quality assurance working group of the workshop about Techniques of Persistent Organic Pollutant Measurements in Northern Environments (18). Results are presented that are relevant for the evaluation of the data quality.
Experimental Section Sampling Site and Sampling Method. Samples of about 1000-1100 m3 of air were collected over a period of 48 h at Ny-Ålesund (78°55′ N, 11°56′ E, Svalbard, Norway). From April to October only one sample per week was taken. The 48-h samples were collected for every 2-day period in
November and December to study if the sampling frequency of one 48-h sample per week was sufficient to detect all long-range transport episodes. Samples are marked by the number of the week. Additional characters label the first (a), second (b), and third (c) 48-h sample of a week. The sampling flow was about 20 m3/h using the same high-volume sampler as described in ref 19. Particles were collected on a glass fiber filter of 142 mm diameter (Gelman Type AE, Type 61635, cut off >99% for 0.2 µm), which was pretreated at 450 °C for 8 h. Compounds in the vapor phase were adsorbed on two sequential polyurethane foam (PUF) plugs (100 mm diameter, 50 mm thickness, and a density of 25 kg/m3). Further details about cleaning and the type of foam are given in ref 15. Selection of Compounds. Since the presented study was part of the AMAP, the selection of the compounds to be quantified had to be coordinated with the analysis of other matrices such as, for example, biota and sediments. A very large number of compound classes were included in the whole project such as polycyclic aromatic hydrocarbons, polychlorinated dibenzo-p-dioxins and dibenzofurans, mono- and non-ortho-substituted polychlorinated biphenyls, and chlorinated pesticides. Due to restricted resources, only a limited number of congeners could be analyzed from some compound groups in all environmental samples. Some of the selection criteria were the compound’s toxicity, the complete lack of data, and/or the testing of new methodology. For 1993, priority was given to the analysis of DDT compounds and pesticides in air samples. The number of PCB congeners was restricted to those being monitored routinely in biota and other matrices. Therefore, only a limited number of PCBs are part of this data set. Trajectory Calculations. The 850-hPa trajectories were provided by the National Oceanic and Atmospheric Administration (NOAA, courtesy of Dr. Joyce Harris). Isobaric back trajectories for up to 9 days were calculated for 0 and 12 h UTC (Universal Time Coordinated) using the GAMBIT program developed under the geophysical monitoring for climatic change group (GMCC) (20). Reference Compounds. For quantification, officially certified crystalline reference material of >99% purity were
VOL. 30, NO. 7, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
2295
TABLE 2
Concentrations of Polychlorinated Biphenyls at Ny-Ålesund, Svalbard, in 1993a vol (m3)
HCBb
PCB-28
PCB-31
PCB-52
PCB-101
PCB-105
PCB-118
PCB-138
PCB-153
PCB-156
PCB-180
Apr 2-4 Apr 7-9 Apr 13-15 Apr 20-22 Apr 27-29
1100 1100 1207 1165 1137
100 102 73 46 73
10 2.3 4.1 1.1 1.7
7.6 1. 9 3.0 0.79* 1.3
6.4 2.3 3.9 1.1 1.6
3.0 0.93 2.3 0.54 0.86
0.53 0.12 0.34 0.080 0.16
1.2 0.29 1.1 0.24 0.33
1.0 0.27* 0.90 0.23* 0.38
1.1 0.36 1.0 0.26 0.44
0.16 0.020* 0.080 0.028 0.030
0.41 0.11 0.27 0.11 0.12
May 4-6 May 11-13 May 18-20 May 25-27
1153 1145 1109 1109
68 89 87 69
1.9 2.8 1.4 1.6
1.4 2.2 1.1 1.3
2.0 2.5 1.4 1.7
1.1 1.3 0.71 0.93
0.17 0.17 0.12 0.12
0.52 0.44 0.28 0.37
0.74 0.52 0.28* 0.47
0.84 0.67 0.31 0.50
0.045 0.030 0.021* 0.037
0.28 0.18 0.089* 0.16
Jun 1-3 Jun 8-10 Jun 15-17 Jun 22-24 Jun 30-Jul 1
1162 1131 1138 1171 681
88 92 100 67 88
1.2 2.1 2.0 3.9 2.7
0.98 1.5 1.4 2.8 1.9
1.1 1.9 1. 8 3.6 2.3
0.57 0.96 1.3 2.2 1.3
0.090 0.14 0.12 0.20 0.19
0.20 0.34 0.453 0.719 0.448
0.27* 0.379 0.584 0.878 0.474
0.29 0.443 0.72 1.11 0.573
0.020* 0.0495 0.0907 0.0532 0.0681
0.090* 0.134 0.213 0.174 0.225
Jul 6-8 Jul 14-15 Jul 20-22 Jul 27-29
1060 1138 1157 1154
312 48 85 133
47 1.9 1.5 10
24 2.0 1.4 6.6
10 1.2 0.71 2.8
0.79 0.16 0.12 0.30
2.5 0.50 0.26 0.90
2.10 0.47 0.28* 0.74
3.0 0.53 0.27 0.82
0.15 0.070 0.079 0.051
0.35 0.22 0.12 0.15
Aug 3-5 Aug 10-12 Aug 17-19 Aug 24-26 Aug 31-Sep 2
965 1157 1133 1165 1143
162 214 162 189 91
8.0 4.1 2.6 2.8 1.3
5.6 3.0 1.8 2.1 0.97
5.1 4.2 2.3 2.9 1.4
1.8 2.4 1.3 1.4 0.73
0.24 0.56 0.20 0.23 0.091
0.67 1.2 0.61 0.71 0.25
0.66 1.1 0.54 0.52 0.35
0.62 1.4 0.58 0.68 0.31
0.034 0.090 0.045 0.038 0.028
0.11 0.31 0.12 0.13 0.11
Sep 7-9 Sep 14-16 Sep 21-23 Sep 28-30
1134 1141 1140 1128
99 79 74 82
1.5 0.98 1.5 1.6
1.0 0.67* 1.1 1.1
1.2 0.93 1.4 1.3
0.54 0.44 0.83 0.59
0.082 0.079 0.16 0.078
0.21 0.22 0.38 0.23
0.25* 0.25* 0.41 0.22*
0.24 0.25 0.45 0.25
0.020 0.021* 0.039 0.018*
0.072* 0.089* 0.11 0.070*
Oct 5-7 Oct 12-14 Oct 19-21 Oct 26-28
1136 1253 1098 1158
74 79 112 83
1.2 1.1 1.6 2.1
0.74* 0.72* 1.0 1.4
0.94 0.95 1.4 1.6
0.43 0.47 0.93 0.87
0.067* 0.073 0.21 0.16
0.19 0.20 0.61 0.43
0.23* 0.23* 0.79 0.46
0.22 0.25 0.56 0.46
0.015* 0.021* 0.094 0.038
0.069* 0.099* 0.18 0.12
Nov 2-4 Nov 9-11 Nov 16-18 Nov 23-25 Nov 25-27 Nov 27-29 Nov 29-30
1118 1156 1151 1114 1269 1003 742
77 74 75 47 104 23 44
9.1 3.2 3.9 9.9 8.3 3.6 6.2
6.7 2.2 2.8 6.6 5.5 2.4 4.0
1.9 1.4 1.8 2.2 3.4 1.3 1.8
0.81 0.83 1.3 0.70 2.4 0.57 0.66
0.15 0.12 0.29 0.089 0.40 0.097 0.091
0.38 0.34 0.73 0.26 1.2 0.26 0.24
0.36 0.39 0.72 0.26 1.0 0.26* 0.28*
0.37 0.40 0.70 0.29 1.26 0.31 0.33
0.041 0.019* 0.088 0.017* 0.071 0.023 0.019*
0.086* 0.11 0.17 0.067* 0.276 0.079* 0.099*
Dec 1-3 Dec 3-5 Dec 5-7 Dec 7-9 Dec 9-11 Dec 11-14 Dec 14-16 Dec 16-18 Dec 18-20 Dec 20-22 Dec 22-24 Dec 24-26 Dec 26-28 Dec 28-30
1149 1145 1140 1169 1141 1131 1132 844 1175 1141 1131 1207 1137 1113
79 73 82 69 97 139 81 82 41 75 77 77 75 67
5.0 4.0 7.3 2.2 2.8 4.7 2.91 3.6 1.7 3.6 3.4 3.4 2.1 2.9
3.3 2.6 5.5 1.4 2.1 3.0 1.7 2.3 1.1 2.3 2.1 2.3 1.4 1.9
1.6 1.1 4.1 0.85 1.4 2.5 1.6 1.5 0.77 1.5 1.2 1.2 1.3 1.4
0.76 0.46 4.2 0.39* 0.72 1.25 0.90 0.95 0.50 0.82 0.60 0.53 0.74 0.73
0.12 0.078 1.2 0.081 0.11 0.24 0.16 0.14 0.091 0.15 0.096 0.092 0.14 0.11
0.31 0.21 2.93 0.22 0.31 0.67 0.44 0.46 0.25 0.41 0.27 0.24 0.38 0.30
0.38 0.30* 3.2 0.37 0.33* 0.58 0.38 0.36 0.24* 0.38 0.25* 0.24* 0.35 0.30*
0.44 0.33 3.6 0.35 0.36 0.59 0.43 0.42 0.24 0.43 0.27 0.27 0.41 0.37
0.024 0.022 0.30 0.036 0.030 0.049 0.041 0.030 0.062 0.023 0.018* 0.019* 0.016* 0.026
0.11 0.12 0.99 0.17 0.096* 0.13 0.10* 0.087* 0.20 0.083* 0.061* 0.063* 0.113 0.087*
date
31 1.4 1.1 7.2
aAll values are given in pg/m3. Data that were below the lower limit of determination given in Table 1 are marked with an asterisk. Levels in combined filter and polyurethane foam extracts are given. bHCB, hexachlorobenzene.
used and obtained from Promochem (Wesel, Germany). 13C-isotope labeled PCB compounds were purchased from Cambridge Isotope Laboratories (Woburn, MA) as solutions in n-nonane (40 µg/mL). Sample Extraction and Cleanup. Prior to sample extraction, 50 ng of -HCH in 10 µL of isooctane and 13Cisotope labeled PCB compounds (one for each congener to be quantified) were added to the first PUF plug. The glass fiber filter and the PUF plugs were Soxhlet extracted separately for 8 h with 150 or 300 mL of n-hexane/diethyl ether 9:1, respectively. The extracts were combined since earlier studied have shown that the fraction being present
2296
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 30, NO. 7, 1996
in the vapor phase exceeded 90% for most compound including PCBs (19). Furthermore, the very low levels in the filter extract in most cases were too close to the detection limit and blank level. Details about sample cleanup are given in ref 15; therefore, the method is only briefly described. A total of 100 µL of n-nonane was added to the combined extracts as a less volatile solvent. It prevents losses during volume concentration and acts as a kind of keeper. The extract was then treated with concentrated sulfuric acid. The hexane phase was dried with sodium sulfate and placed on a silica column, and the compounds of interest were eluted
TABLE 3
Concentrations of Selected Polychlorinated Compounds in Extract of Ambient Air Control Samplea concn (pg/m3) compd
1992, n ) 9 x ( SD
1993, n ) 8 x ( SD
γ-HCH trans-chlordane PCB-153
62.0 ( 3.6 2.27 ( 0.14 6.1 ( 1.3
60.7 ( 5.1 2.51 ( 0.21 4.5 ( 0.5
a
x, mean; SD, standard deviation.
FIGURE 2. γ- and r-HCH concentrations at Ny-Ålesund (79 °N) and Lista (58 °N), south Norway in 1993. Long-range transport episodes confirmed by trajectories are marked with LR for Lista, and those for Ny-Ålesund are marked with either the main source region or with an asterisk (*). (?) concentration increase not identifiable by trajectories; (C), sample eliminated due to contamination; (a, b, and c), first, second, and third 48-h sample of the corresponding week.
FIGURE 1. Weekly minimum, maximum, and average temperature for the 1993 campaign at Ny-Ålesund, Svalbard, Norway.
with n-hexane/diethyl ether. After volume concentration to about 0.5 mL, 10 ng of octachloronaphthalene in 10 µL of isooctane was added as the recovery standard. Then, the sample was further concentrated to about 100 µL by applying a gentle stream of purified nitrogen. Quantification by Low-Resolution Mass Spectrometry. High-resolution gas chromatography (HRGC) combined with low-resolution negative ion chemical ionization mass spectrometry (NICI-LRMS) was used for the quantification of the pesticides and hexachlorobenzene. Better detection limits were obtained for the chlordanes than by highresolution electron ionization mass spectrometry. A Hewlett-Packard (HP) 5989 mass spectrometer with an HP 5890 Series II gas chromatograph was employed. Negative ion chemical ionization (NICI) was carried out at an ion source temperature of 200 °C and an ion source pressure of 1.0 hPa using methane as reagent gas. The ion source was tuned for optimum performance with perfluorotributylamine at m/z 312, 414, and 464. The electron energy of the primary electrons was about 170 eV, and the high-
energy dynode voltage was set to 10 kV. The M•- and (M + 2)•- ions were recorded for each compound [for HCH, (M - Cl)-] in the selected ion mode employing a dwell time of 50 ms per ion and up to 10 ions per group. For quantification, the most abundant ion was used. The HRGC conditions were as follows: Separation on a 25 m × 0.2 mm i.d. fused silica capillary coated with 0.11 µm of HP Ultra 2 (5% diphenyl-, 95% dimethylpolysiloxane, Hewlett-Packard); carrier gas, He, at a flow velocity of 3540 cm/s (180 °C); splitless injection of 1 µL; splitless time 2 min; injector temperature 250 °C; transfer line 260 °C; temperature program, 60 °C for 2 min, then 20 °C/min to 150 °C, and 4 °C/min to 280 °C (10 min isothermal). Quantification by High-Resolution Mass Spectrometry. To obtain a sufficient sensitivity, PCB and DDT compounds had to be quantified by high-resolution electron ionization mass spectrometry (EI-HRMS) at a resolution of 10000. A VG Autospec system (Fisons VG Analytical, Manchester, England) with an HP 5890 II gas chromatograph was employed in the selected ion detection mode. Up to 16 ions with a channel time of 20-70 ms and two perfluorokerosene lock masses were measured per group. For each PCB congener to be quantified, both the (M + 2)•+ and
VOL. 30, NO. 7, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
2297
TABLE 4
Concentrations of Polychlorinated Pesticides at Ny-Ålesund, Svalbard, in 1993a date
vol (m3)
r-HCH
γ-HCH
tr-CD
cis-CD
tr-No
cis-No
Apr 2-4 Apr 7-9 Apr.13-15 Apr 20-22 Apr 27-29
1100 1100 1207 1165 1137
69 136 74 21 92
16 22 18 7.7 24
0.70 0.67 0.62 0.56 0.65
0.791 1.034 0.857 0.727 1.194
0.63 0.89 0.79 0.97 1.2
0.093 0.094 0.18 0.19 0.20
May 4-6 May 11-13 May 18-20 May 25-27
1153 1145 1109 1109
31 111 146 6.8
11 27 38 3.3
1.1 0.48 0.26 0.55
2.0 0.92 1.1 1.9
1.6 0.89 0.91 1.3
0.20 0.16 0.14 0.27
Jun 1-3 Jun 8-10 Jun 15-17 Jun 22-24 Jun 30-Jul 1
1162 1131 1138 1171 681
95 85 74 110 53
17 15 14 18 6.8
0.45 0.32 0.33 0.30 0.26
1.5 0.88 1.1 0.94 0.67
1.2 0.81 0.89 0.75 0.62
0.34 0.27 0.31 0.24 0.17
Jul 6-8 Jul 14-15 Jul 20-22 Jul 27-29
1060 1138 1157 1154
68 47 64 203
37 18 5.4 25
0.56 0.16 0.27 0.37
0.78 0.63 1.1 1.5
0.71 0.48 0.80 1.1
0.20 0.16 0.32 0.34
Aug 3-5 Aug 10-12 Aug 17-19 Aug 24-26 Aug 31-Sep 2
965 1157 1133 1165 1143
79 46 105 82 80
16 11 14 9.1 8.8
0.29 0.48 0.31 0.36 0.21
1.2 0.94 1.5 1.2 1.0
0.82 0.67 0.98 0.77 0.66
0.28 0.21 0.39 0.25 0.23
Sep 7-9 Sep 14-16 Sep 21-23 Sep 28-30
1134 1141 1140 1128
71 64 64 50
8.0 7.8 9.1 6.8
0.19 0.21 0.25 0.37
0.81 0.94 0.74 1.0
0.62 0.58 0.56 0.81
0.21 0.27 0.24 0.27
Oct 5-7 Oct 12-14 Oct 19-21 Oct 26-28
1136 1253 1098 1158
70 86 86 81
11 17 13 15
0.25 0.35 0.22 0.56
0.909 1.245 0.861 1.473
0.710 0.796 0.610 1.141
0.234 0.162 0.145 0.268
Nov 2-4 Nov 9-11 Nov 16-18 Nov 23-25 Nov 25-27 Nov 27-29 Nov 29-30
1118 1156 1151 1114 1269 1003 742
81 99 64 53 109 25 33
14 19 8.6 11 30 3.9 6.2
0.34 0.91 1.0 0.56 1.4 0.38 0.52
0.85 2.0 2.0 0.93 1.8 0.50 0.86
0.60 1.5 1.5 0.73 1.4 0.40 0.69
0.098 0.30 0.30 0.12 0.22 0.069 0.13
Dec 1-3 Dec 3-5 Dec 5-7 Dec 7-9 Dec 9-11 Dec 11-14 Dec 14-16 Dec 16-18 Dec 18-20 Dec 20-22 Dec 22-24 Dec 24-26 Dec 26-28 Dec 28-30
1149 1145 1140 1169 1141 1131 1132 844 1175 1141 1131 1207 1137 1113
60 81 97 83 84 134 93 77 22 90 77 77 91 49
9.6 11 13 9.0 13 24 16 19 4.9 16 15 11 17 9.8
0.73 0.49 0.54 0.39 0.72 0.97 0.63 0.68 0.32 0.80 0.56 0.83 0.91 1.0
1.2 0.88 0.90 0.70 1.2 1.4 0.87 0.95 0.42 1.2 0.86 1.3 1.3 1.5
0.96 0.64 0.62 0.48 0.86 1.1 0.65 0.74 0.35 0.90 0.64 0.97 1.0 1.1
0.17 0.066 0.057 0.031 0.053 0.11 0.076 0.099 0.053 0.052 0.057 0.083 0.097 0.17
o,p′-DDE
p,p′-DDE
o,p-DDD
p,p′-DDD
o,p′-DDT
p,p′-DDT
0.20
0.47
0.045
