Chlorinated Hydrocarbon Pesticides in Western North Atlantic Ocean Robert B. Jonas and Frederic K. Pfaender' Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, N.C. 27514
w Both DDE and dieldrin are detected in the offshore waters
Experimental
Water samples were collected from the western North Atlantic Ocean between May 31,1972, and June 13,1972, during cruise E-8B-72 of the R. V. Eastward. Samples were collected by means of either a diethyl ether washed bucket (for surface samples) or 10-1. polyvinylchloride Niskin bottles. Samples were obtained from the surface, 50,500, and 1000 m depth. Figure 1shows a chart of the cruise route and sample stations, which are numbered according to the standard R. V.Eastward continuous station numbers. Surface samples only were obtained from the three westernmost stations. The samples were stored in the dark in 6-1. ether-washed polyethylene jerricans which were taken to the University of North Carolina, Department of Environmental Sciences and Engineering, for extraction and subsequent analysis. Reagents. Reagents used were diethyl ether, pesticide grade; hexane, pesticide grade; and sodium sulfate, anhydrous, granular, AR grade washed in diethyl ether before use. Extraction. Samples were extracted with boiling ether in Although the presence of various chlorinated hydrocarbons 2-1. continuous extraction chambers. In each case 1.8 1. of in oceanic biota has been well documented (1-4), the occurseawater was extracted for 4 h. This procedure was chosen rence and concentration of these compounds in seawater itself since continuous extraction is a more reproducible method have only recently been reported (5-7). These reports suggest than traditional separatory funnel extractions (9, 10). The that polychlorinated biphenyls (PCB), and to a lesser extent ether extract was dried over anhydrous sodium sulfate which DDT, are widespread contaminants of the North Atlantic had been previously extracted with pesticide grade ether. This Ocean. However, even with these reports, very limited data latter procedure was necessary since the sodium sulfate was are available concerning the distribution of chlorinated hycontaminated with a substance which produced gas chromadrocarbons in the sea. The present paper is a report of the tographic peaks very similar to those produced by the PCB distribution and concentration of DDT [l,l-bis-(p-Chlorophenyl)-2,2,2-trichloroethane],DDD [l,l-bis-(p-Chloro- Arochlor 1254. Ether washing eliminated this problem. To be certain that no part of the system was causing further conphenyl)-2,2-dichloroethane], DDE [ 1,l-bis-(pXhlorophenyl)-2,2-dichloroethylene],dieldrin (1,2,3,4,10,10-Hexa- tamination, all glassware was washed with ether and periodically tested for interfering contaminants. (Several containers chloro-6,7-epoxy-1,4,4a,5,6,7,'8,8a-octahydro-1,4-endo-exo5,8-dimethano-naphthalene), aldrin (1,2,3,4,10,10-Hexa- of diethyl ether, AR grade, were also contaminated with chloro-1, 4, 4a, 5, 8, 8a-hexahydro-1, 4-endo-exo-5, 8-dicompounds yielding chromatograms very similar to Arochlor methano-naphthalene), and lindane (1,2,3,4,5,6-Hexa1254. Unlined plastic caps appeared to be the source of the chlorocyclohexane) with depth and distance from shore in the contamination.) This testing revealed no further contamination problem. The volume of the ether extract was then North Atlantic Ocean. reduced to a few drops under reduced pressure in a rotary Despite current bans on the use of certain hazardous subevaporator, and the residue suspended in hexane. Pesticide stances (i.e., the DDT ban and limitations on the use of PCB concentrations in the extracts were then determined by Ni-63 in the United States), the ever-increasing worldwide use of electron capture gas chromatography. industrial and agricultural chemicals, as part of the effort to Gas Chromatographic Parameters. Instrument: Percombat hunger and disease, continues to assault the biosphere kin-Elmer Model 900 (The Perkin-Elmer Corp., Norwalk, with persistent toxic compounds. Considerable quantities of Conn. 06856). Column: glass, circular, 6 f t (1.8 m) X 0.25 in. chlorinated hydrocarbons find their way into the world's (0.64 cm) 0.d. X 0.08 in. i.d. (0.20 cm), packed with 3% OV-1 oceans, primarily by the atmospheric route (4,8).There, they and 7% OV-210 (combined liquid phase) on 60/80 mesh acid are acted upon by a myriad of physical and biological forces washed Chromosorb W; all column packings were conditioned which eventually lead to the dispersal of these compounds in by baking with gas flow for five days a t 250 OC. Detector: the sea. Knowledge of this distribution pattern is significant Nickel 63 electron capture operated in pulse mode (50 V for in that we might better trace the fate of important biospheric 1 ws). Carrier gas: nitrogen (zero gas grade), 80 ml/min. pollutants, determine what effects they may have on marine Thermal parameters: column temperature, programmed organisms, and gain insight into the complex forces acting to 165-180 "C, 4 "C/min, 6-min initial time, 12-min final time: distribute compounds within the sea. injector temperature, 200 "C: manifold temperature, 240 "C: Recent data of Harvey et al. (7) suggest that the concendetector temperature, 270 "C. tration of a t least one class of these compounds, PCB, has The procedure for the analysis of chlorinated hydrocarbons decreased dramatically (40X) in North Atlantic surface waters in water is well known ( 1 1 ) .In the present case, however, the since 1972. This reduction has followed a decline in certain procedure was modified in two ways. First, nitrogen, was industrial applications of PCB. These authors present some employed as the carrier gas in pulse mode electron capture gas arguments which support the hypothesis that PCB associated chromatography. Additionally, the temperature programming with sedimenting particulate matter can account for the obcapability of the GC was utilized with the electron capture served rapid decline in surface PCB concentrations. of the western North Atlantic Ocean from the surface to 1000 m depth. The mean concentrations of the two pesticides are 3.8 (DDE) and 5.8 (dieldrin) parts per trillion (ng/l.). Other chlorinated pesticides (lindane, aldrin, DDD, and DDT) could not be detected, at most sample sites, by currently available analytical techniques. The data suggest that considerable variability, both with depth and distance from shore, is a dominant feature of the distribution of chlorinated pesticides in the North Atlantic Ocean. Concentrations of DDE and dieldrin range from 0.1 to 18.1 and 0.4 to 19.4 ng/l., respectively. The observed environmental distribution of these pesticides would be consistent with an hypothesis of uptake and transport of these compounds on particulates in the sea.
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Environmental Science & Technology
detector. These modifications, in combination with the liquid packing employed, provided for adequate separation of all the compounds under study. Figure 2 shows (A) a typical chromatogram of a standard mixture of the six chlorinated hydrocarbons and (B) a sample chromatogram (station 20129, 1000 m depth). Tests with the PCB Arochlor 1254 and chromatograms of other PCB mixtures (12) suggest that there are no compounds of PCB origin which interfere with DDE and dieldrin peaks under the conditions employed in this study. Although DDT and DDD might still be confused with chlorinated biphenyls of PCB origin, these evaluations increase confidence in the qualitative identification of DDE and dieldrin. Samples were analyzed on two additional columns to aid in confirming the identity of the observed peaks. Peaks with retention times corresponding to the same pesticide standards were observed when ocean water extracts were injected on a DC-200 (5%) and an SE-30 (5%) column in addition to the
Figure 1. Chart of North Atlantic Ocean sample sites at which water was collected for pesticide analysis during cruise E-88-72 of the R. V.
Eastward Station numbers (from east to west) are: 20120, 20125, 20127, 20129, 20132, 20139, 20144, 20145, 20146, and 20147
I""
50
W
e
25
m
z
x o m W
a: 75
50
25
22
18
14
IO
6
2
MINUTES Figure 2. Chromatograms of chlorinated hydrocarbons A. Mixture of six pesticides, 1-lindane, 2-aldrin. 3-DDE, 4dieidrin, 5-DDD, and 6-DDT. B. Extract of ocean water from 1000 m depth at station 20129
analytical column. The observed pesticide concentrations were not sufficient to allow the use of combined gas chromatography-mass spectrometry as a supplementary identification tool. Blank values for the handling and storage conditions were determined by holding distilled, deionized, carbon filtered water in polyethylene jerricans which were subsequently extracted and analyzed as the seawater samples. Reported data have been corrected for blank values of 0.7 ng/l. for DDE and 0.8 ng/l. for dieldrin. Duplicate extraction and analyses of aliquots of selected samples and water mixtures spiked with known concentrations of pesticide suggest that the overall quantitative variability of the technique was about f 2 5 % a t the 1 ng/l. level. Usual minimum detectability limits were: DDT, 8.0 ng/l.; DDD, 0.8 ng/l.; DDE, 0.4 ng/l.; dieldrin, 0.4 ng/l.; aldrin, 0.2 ng/l.; and lindane, 0.1 ng/l. The data were corrected for the 60% extraction efficiency observed when water spiked with authentic pesticides ( 5 ng/l. DDE and dieldrin) was extracted.
Results and Discussion There are numerous problems involved in the analysis of pesticide concentrations at these very low levels. For example, contamination from a variety of sources, including sample bottles, surface slicks, and laboratory glassware, is always a potential problem. In this instance, all glassware, sample bottles, and solvents were tested periodically, and the extracts checked for pesticide or PCB contamination. Only in the two cases cited previously were contaminating compounds found. Similarly, since there was no correlation of the concentration of pesticide in the samples with the wind or sea conditions prevailing a t the time of sampling (hence surface slick conditions), lowering of sample bottles through the surface seems not to have been a source of contamination. The concentrations of DDE and dieldrin in the ocean water samples are reported in Table I. Both DDE and dieldrin were detected in all but four samples. The mean concentration of DDE was 3.8 ng/l., whereas the corresponding dieldrin value was 5.8 ng/l. The concentrations of DDT and DDD were less than the detectability limits of this technique. Lindane and aldrin were also generally undetectable in these samples. Peaks corresponding to the retention times of lindane and aldrin were observed in some samples. At station 20125 a trace (0.1 ng/l.) of lindane was present a t the surface, a t 50 m, and at 1000 m depth, and the surface aldrin concentration was 0.2 ng/l. Water from station 20127 contained 0.15 ng/l. lindane at the surface and 50 m and 0.6 ng/l. a t a depth of 1000 m. Peaks corresponding to DDE and dieldrin (refer to Figure 2A) are clearly evident in the sample chromatogram in Figure 2B. Repeated extraction of aliquots of water from the same original sample produced very similar results qualitatively and quantitatively, whereas extraction of surface water samples from stations a short distance apart yielded values which are apparently unrelated (stations 20145-20147). Perhaps the most striking features of the data is the lack of any systematic variation in concentration of pesticide with depth or distance from shore. In the latter respect, the data presented here are in agreement with the conclusions of two previous reports (5,6),both of which reported that chlorinated hydrocarbon concentrations did not vary systematically with distance from shore in the North Atlantic. Indeed, a dominant feature of previous reports and the data presented here is the wide range of chlorinated hydrocarbon concentrations even in samples collected only a few miles apart. Apparently atmospheric transport, the postulated principal transport route of pesticides to the ocean, does not lead to entirely uniform oceanic distribution of those compounds (at least in the North Atlantic) as is assumed in most distribution system models (4,8). Volume 10, Number 8, August 1976
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Table 1. Concentrations (ng/l.) of DDEBand Dieldrinb in North Atlantic Ocean Water of 0, 50, 500, and 1000 m Depth North 34' 32'
35' 02'
35' 08'
35' 13'
37' 07'
36' 17'
35' 00'
33' 50'
33' 22'
32' 00'
61' 38'
59' 00'
55O 51'
53' 13'
48' 54'
20129
20 127
20125
20120
West 76' 31'
75' 03'
74' 42'
74' 18'
67' 14'
Station Depth, m
Mean f SD
20147
20146
20145
20144
20139
20132
DDE
0 50 500 1000
4.9 f 5.2 2.7 f 3.6 4.0 f 5.3 3.0 f 2.5
3.5
3.9
18.1
... ...
... ...
...
...
...
... ...
0 50 500 1000
6.4f 5.6 6.2 f 2.7 3.6f 4.3 6.9 f 6.2
6.2
19.4
2.4
... ...
... ...
...
...
6.1 5.7 6.2
...
...
...
...
6.0 0.7 2.3
7.5 4.3 5.1 1.2
...
3.3 10.3 15.4 4.9
