Environ. Sci. Techno/. 1995, 29,272-275
Changes in the PCB
Air between 1972 and 1992
concentrations (8). Subsamples of the filters had been stored and were analyzed retrospectively for PCBs. The same analytical procedures were applied to all the samples, and the time series extends back over 21 years.
Experimental Section KEVIN C. JONES,*,+ R A Q U E L DUARTE-DAVIDSON,’ A N D PETER A . CAWSE$ Environmental Science Division, Institute of Environmental and Biologcal Sciences, Lancaster University, Luncaster, LA1 4YQ, U.K., and AEA Technology, Terrestrial Environment Studies, Building 364, Harwell, Didcot, Oxfordshire OX11 ORA, U.K.
Introduction Movement through the atmosphere and air-surface exchange processes are of fundamental importance in the global cycling and redistribution of PCBs. While at any one time the loading of PCBs in air is minor compared to the burden held in other environmental compartments such as soils or water bodies (1, 2), long-range atmospheric transport has been invoked to explain the presence of PCBs and other persistent semivolatile compounds in remote areas of the globe. Indeed, some workers have argued that atmospheric transport processes operating on the global scale may result in a global distillation of semivolatile organic compounds from warmer source areas to the colder polar regions (3). Global scale source areas of PCBs would be the temperate industrialized nations, where PCBs were manufactured and used extensivelythroughthe 1960- 1970s (1, 4,
5).
Data on long-term air concentration trends for PCBs are needed for two reasons: first, to monitor the effectiveness of strategies designed to reduce emissions to the environment which came into force during the 1970- 1980s in many industrialized countries; and second, to provide input data to unsteady state global cycling and surface-air exchange models, such as those developed by Wania and Mackay (6)and Harner et al. (7). These models are based on the premise that past PCB inputs to soils and water bodies in industrialized temperate latitudes may subsequently be released by volatilization back to the air (2, 4 ) . Consequently, whereas inputs to the atmosphere during the 1960s may have been dominated by fresh releases incurred by the widespread use of PCBs at that time, contemporary inputs to the atmosphere are likely to be primarily due to the remobilization or volatilization of previously emitted compounds “outgassing” back to the atmosphere (1-4, 6, 7). Alcock e t al. (4) and Jeremiason e t al. (2)have provided evidence that PCB concentrations in U.K. soils and Lake Superior waters have declined since the 1970s due to volatilization of previously deposited inputs. This paper presents data from the analysis of a set of archived air filter samples, collected at two U.K. sites since 1972 for an ongoing survey of atmospheric trace metal +
Lancaster University.
4
AEA Technology.
272 1 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 29, NO. 1, 1995
The Harwell Laboratory of AEA Technology at Chilton near Oxford started the collection of air filters for the analysis of trace elements in air on a monthly basis at various rural U.K. sites in 1972. Cellulose filters (Whatman 40) are used to retain air particulates at 1.5 m above ground. The volume of air filtered is about 250 m3 per month and is measured by meter. Portions of these filters have been retained, stored, and sealed in plastic bags in a dark, locked cupboard at room temperature at the Harwell Laboratory. For this study, samples were selected from two sites, Chilton itself (grid reference SU 468861, altitude 130 m) and Wraymires near Windermere in the English Lake District (gridreference SD 362974, altitude 84 m). Chilton is in a rural location ca. 90 km to the west of London, surrounded by arable agricultural land. Wraymires is a rural site in northwest England, surrounded by rough and pasture-grazing land. Rainfall at the two sites from 1972 to 1991was 0.65 and 1.9 m per annum, respectively, while the total suspended particulates (TSP) at the two sites are similar and have averaged 22 and 18 pg m-3 at Chilton and Wraymires, respectively. Because more PCBs are found on filters in the winter (9),the monthly samples for the winter quarter (November, December, January) were bulked to give an average air volume sampled of 400 m3 for analysis (range between 170 and 675 m3). Data are therefore available for winter filter-borne PCBs at the rural sites of Chilton and Wraymires for 1972-1992. The samples were extracted and analyzed with procedures routinely used at Lancaster for the determination of PCBs in contemporary air samples, collected under the Toxic Organics Micro-Pollutants (TOMPS)program. These have been described elsewhere (10,111, but essentially involve Soxhlet extraction with hexane, sample cleanup, and quantification by GC/ECD,with confirmation by GC/ MSD. A standard mix of the following congeners is used to determine the so-called “total” (E) PCB content: 18, 28/31, 30, 37, 40, 44, 52, 54, 61/74 (co-elute), 66, 77/110, 82/151,99, 101, 104, 105, 118, 119, 126, 128, 138, 149, 153, 156, 169, 170, 180, 183, 185, 187, 188, 1941205, 198, 201, 202,204,206,208, and 209 (4). Some congeners were never detected (e.g., 104, 119, 126, and 1691, while others were quantified for analytical reasons (e.g.,30 was employed as an internal standard, 209 as a retention time marker). In this paper, the data for the individual congeners 28, 52, 138, 153, and 180 are presented together with the CPCB
information. Mean filter blank values were ‘2 pg/filter for all individual congeners.
Results and Discussion The concentrations of congeners 28,52,138,153, and 180, and the CPCBs are presented in Table 1. Concentrations at Chilton have been consistently higher than those at Wraymires throughout the time series and have clearly
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TABLE 1
Concentrations of Selected PCB Congeners and ZPCBs on Air Filters from Two U.K. Rural Sites between 1972 and 1992 (pg md3) Chilton
year
28
52
1972 175 73 25 11 1973 1974 14 13 1975 45 16 58 13 1976 22 1977 14 1978 26 11 1979 13 2.8 16 1980 17 1981 91 36 1982 10 13 1983 3.3 2.0 1984 4.9 2.9 1985 24 7.4 1986 5.4 3.9 1987 7.3 4.5 1988 15 3.9 1989 19 11 1990 2.9 4.8 1991 22 5.6 1992 9.0 3.3 EPCB is defined in the text.
Wraymires
138
153
180
EPCBs’
28
52
138
153
180
ZPCB’
3.3 7.8 5.0 16 14 44 13 ‘1
