Environ. Sci. Techno/. 1995,29, 346-355
T i Trarnls in Levels, Pattern, and Pm&s for Pdychhm~ ed Dibenzag-diadns, Diberuofurans, and Biphyls in a Sediment Core f” the Baltic Proper LARS-OWE K J E L L E R * AND C H R I S T O F F E R RAPPE Institute of Environmental Chemistry, Ume& University, S-901 87 Umed, Sweden
A rural laminated sediment core from the northwestern part of the Baltic Proper (station P18) was sliced into nine dated disks. (Average age: 1882, 1906, 1922, 1938, 1954, 1962, 1970,1978, and 1985). Each disk was analyzed for tetra- to octachlorinated dibenzo-pdioxins/dibenzofurans (PCDD/Fs) and seven congeners of chlorinated biphenyls (PCBs). Both PCDD/Fs and PCB were detected in small but significant levels during the period 1882-1962 (total PCDD/F 92-234 pg/ 9). The proposed sources are combustion of various natural items like coal, wood, and peat. Increased PCDD/Fand PCB levels were found during the period 1970-1985 (total PCDD/Fs 520-1800 pg/g). The increased concentrations coincide with a change in PCDD/F congener profiles and isomeric patterns. Detailed examination of the profile and pattern demonstrates that chloroorganics, and among them pentachlorophenol (PCP), are the main contributors to PCDD/Fs. Polychlorinated alkyldibenzofurans (alkylPCDFs) were detected in the 1985 and 1978 disks, providing evidence of coastal transport and demonstrating the impact of pulp mill chlorine bleaching activities. The transporttime for particulates with coastal origin is estimated to be in order of decades. This should be compared to the atmospheric input via dry and w e t deposition, which is estimated to have a residence time in the water column of a maximum of 2 years. Degradation is assumed to be insignificant, but an estimate of minimum half-life times for PCDD/F in buried sediment is made.
Introduction Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and polychlorinated biphenyls (PCBs)are found worldwide as background trace contaminants and locally as a serious hot-spot problem. They are formed during the production ofvariouschemicals,by industrialmanufacturing processes, and by combustion. Transport is foremost in the atmosphere and hydrosphere, followed by deposition resulting in dispersal throughout the total environment (1-3). The contribution of PCDDlF from different sources is a discussed topic. One approach for retrospective source identification is to use dated sediment cores. Using this method, Hites and co-workers have reported that in Lake Siskwit and three Swiss lakes the PCDDlF concentrations in dated sediment cores have increased since 1940. Combustion is implicated as the major source of PCDDlFs in the atmosphere from their occurrence in these remote lakes. The PCDDlF profile leads to a hypothesis of a congener group discrimination related to vapor pressure and the photostability of PCDD/F (4). Our group has recently reported evidence for an atmospheric input of PCDDlF in U.K. soil and herbage since 1846 (5). The PCDDlF source in the early samples is suggested to be the combustion of firewood, coal, peat, etc. The profile of PCDDlFs is related to combustion as found in the old (pre1940) soil and herbage (6, 7). A drastic increase of the PCDDlF concentration in U.K. herbage occurs during the period 1944-1960; this increase is followed by a change in PCDDlF profiles, which indicates the impact of a new PCDDlF source or sources. Comparedwithknown sources, the recent samples have a profile more influenced by chloroorganics, especially pentachlorophenol (PCP), than by combustion (8, 9). Our results from soil and herbage samples support the conclusion drawn by Hites that anthropogenic sources of chloroorganics contribute to the present burden of PCDDlF, but the observed change in pattern poses the question of whether the combustion of chloroorganics or chloroorganics themselves are the main contributors of PCDDlF. Our results also cast some doubt on the environmental significance of vapor pressure and photostability for the discrimination process of PCDDlF. Probably the resulting OCDD-dominated profile is a combination both of sources and processes. Several sediment cores from the Baltic Sea have been investigated for their content of PCBs (10-13). The trend shows increased concentration of PCB, followed by a leveling out or decrease in present times. PCBs have not been detected in the deeper core layers (pre-industrial samples). Investigation Area The Baltic Proper (see Figure 1) has turned from a sea with clean, oligotrophic, clear water to one of the most contaminated and euthrophic sea areas in the world. A small but important part of the contamination consists of PCDDlFs and PCBs (14). An estimation of the relative contribution of various PCDD/F sources has been made by the Swedish National Environmental Protection Board (15). The agency implicates municipal incinerators, pulp bleaching, vehicle exhausts, and other combustion activitiesas being the major sources of PCDD/ * To whom correspondence should be addressed Telephone: (46) 90-165000; Fax: (46) 90-186155.
346 1 ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 2. 1995
0013-936w95/0929-0346$09.00/0
D 1995 American Chemical Society
TABLE 1
Physical Parameters and Age Determinatioif disk no. 1 2 3 4 5 6 7 8 9
core depth (cm) 0-2 2-4 4-6 6-8 8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24 24-26 26-28
VOW %LO1
age range (year)
average age(year)
comment
95 90 81 75 71
25 14 8 7 7
1982-1988 1974-1981 1966-1973 1958-1965 (1950-1957)
1985 1978 1970 1962 (1954)
laminated laminated laminated laminated mixed
70
7
(1934-1941)
(1938)
mixed
68
7
(1918-1925)
(1922)
mixed
77
7
(1902-1909)
(1906)
mixed
69
7
(1878-1885)
(1882)
mixed
a Physicalparametersfor the sediment core at station P18. The age in the 0-8-cm part is determined by counting the annual lamina in the sediment. The age in the 8-28-cm part of the core is calculated from the sedimentation rate in the 2-8-cm part of the core (2.5 mm/year). Calculatedage is given in parentheses. Sediment water content (%W) and percentage loss of ignition (%Lollis determined according to ref
24.
FIGURE 1. Map of the samplings site in Baltic Proper. The station PI8 (this work) and station 40 (ref 24) is given.
F. Other reported sources of PCDD/F into the Baltic Proper are municipal waste water (16‘)and the chloralkali industry (17). A budget has been proposed for PCB (18). Several reports describing the Baltic Proper and the specific sampling position (P18) have been published (19-22).
Materials and Methods Sampling. A sediment core sample was taken from station P18 January 22, 1988 (see Figure 1). The position is SW Gotska Sandon (latitude 58’10’00” and longitude 18’1 1’10’’) at a depth of 132 m. The sediment was taken with a box corer (231, and it was immediately subsampled by gently pressing polyethene tubes through the sediment core. The subcores were sliced into 2-cm disks, transferred to unused glass jars, and acidified with sulfuric acid. Samples for PCDDlF and PCB analysis consist of composite from five subcores. Sediment water content (%Wl and percentage loss of ignition (%LOI)were determined (24). Experimental Methods. The procedure for the analysis of PCDDlF is described elsewhere and is summarized as follows (24, 25). Sediments are air-dried, crushed- and Soxhlet-extracted with toluene for 12 h. Eight tetra- to octaCDD/F 13C-labeledinternal standards are added for recovery measurements. Sample cleanup includes chromatography on silica, alumina, and carbon adsorbents. Final separations allowing quantification are made on a high-resolution gas chromatograph equipped with a 60-m SP-2330 (Supelco)or a 60-m DB5 U&W Scientific) column. Detection is performed on a VG70-250s double focusing mass spectrometer, operating with single ion recording at a resolution of 9000. PCB fractions from the alumina and from the carbon columns are concentrated and analyzed for seven PCB congeners (IUPACNos. 28,52,101,118,138, 153, and 180) (12). Principal Component Analysis (PCA). Calculationsare done with the SIMCA software version 3B (UMETRI). Each detected isomer or isomer cluster constitutes a variable in
the calculation. Nondetects are treated as missing values. Before calculation, variables in the sample are dividedwith the variable sum for the sample (to remove difference due to concentrations among samples). Then each variable is autoscaled to equal standard deviation (to remove size difference between individual variables). Above this are variables centered by removing the average values (26).
Results and Discussion Physical Data from Sediment Core. The sampling resulted in a 28-cm deep sediment core. The sediment is of the accumulation type and is laminated in the upper 0-8-cm section. Age determination is effected by simply counting the lamina in the 0-8-cm section, which corresponds to 31 years, indicating that the bottom of the Baltic Proper at this location becomes anoxic around 1957. The age determination by counting the varve has been found to correspond well with radio nucleotide age determination (zlOPb)in the Baltic Sea (13, 27). From the 2-8-cm laminated section in the core, the sedimentation rate is determined to be 2.5 mm/year; this sedimentation rate is also used for the age determination of the 8-28-cm section (seeTable 1). This approximation did not take into account any gradual compression, bioturbation, or other processes in the core, but is an reasonable estimation of the age in the deeper core section. The dating of burial sediment below 8 cm is then more approximate. The upper disks have a higher content of water and of organic compounds as expressed by %LOI, a consequence of anaerobic and abiotic conversion processes, resuspension of organic compounds, and diffusionlosses to the water column which occurs from the recently deposited sediment surface in combination with compressing (28). The approach to use one single sediment core to describe PCDDlF contamination in the Baltic Proper is risky; however, this core is a typical representative average core for the area, based on the composition of eight independent sampled sediment cores where varve counting and 37 analyses of extractable organic chlorine (EOCl) have a been performed (29, 30). We do not suggest a direct correlation between the EOCl VOL. 29. NO. 2, 1995 I ENVIRONMENTAL SCIENCE & TECHNOLOGY I 3 4 7
TABLE 2
levels of TCDD and TCDF from a Sediment Care at Station P 1 8 d n * average age core deep (cm)
disk 1 1985 0-2
disk 2 1978 2-4
disk 3 1970 4-6
disk 6 1938 12-14
disk 7 1922 16-18
disk 8 1906 20-22
disk 9 1882 26-28
1.15 1.01 2.24 2.19 1.03 0.98 0.62 0.55 1.73 1.81 0.73 0.58 1.33 1.20 3.76 3.42 1.12 1.44 4.03 3.35
