- Email: [email protected]
Analysis of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in soil and digested sewage sludge from Stockholm, Sweden
Chemosphere, Vol.21, Nos.lO-ll, Printed in Great Britain
pp 1213-1220,
1990
0045-6535/90 $3.00 + .00 Pergamon Press plc
ANALYSIS OF POLYCHLORINATED DIBENZO'P'DIOXINS (PCDD) AND POLYCHLORINATED DIBENZOFURANS (PCDF) IN SOIL AND DIGESTED SEWAGE SLUDGE FROM STOCKHOLM, SWEDEN Dag Broman*, Carina NM*#, Carl Rolff*and Yngve Zeb0hr*# *Aquatic Chemical Ecotoxicology, Department of Zoology and #Department of Analytical Chemistry University of Stockholm, 106 91 Stockholm, Sweden
ABSTRACT In this investigation the content of PCDDs and PCDFs in sewage sludge samples and top soil from fields situated in the County of Stockholm has been investigated. Further, the contribution of PCDDs and PCDFs to the fields from sewage sludge is compared with the contribution from two non-point emission sources i.e. road traffic and the urban area of the city of Stockholm. The mean concentration in four analyzed sludge samples is 79 pg TEQ/g (organic weight; o.w.). Soil samples taken close to major roads vary between 13 and 49 pg TEQ/g (o.w.) and soil samples (t b-4b) which were not taken close to major roads vary between 9 and 32 pg TEQ / g (o.w.). The results indicate that both road traffic and outlets from the urban area influence the PCDD and PCDF concentrations in the arable soil. Fertilization with sludge (1 tonne dry weight/hectare and year) raise the initial soil concentrations of PCDD and PCDF In the fields by approx. 2 - 3 %.
INTRODUCTION In Sweden, and many other countries, there is a continuous discussion concerning the significance of sewage sludge fertilization of cultivated land in terms of contamination of the soil and crops with dibenzop-dioxins (PCDDs) and dibenzofurans (PCDFs). Several studies have investigated the concentrations of these pollutants in different types of sewage sludge samples (Lamparski et al., 1984 ; N~tf et al., 1990; Rappe et al., 1989). The purpose of this investigation was to determine the content of PCDDs and PCDFs in sewage sludge samples and top soil from fields situated in the County of Stockholm. Further, the contribution of PCDDs and PCDFs to the fields from sewage sludge were to be compared with the contribution from two nonpoint emission sources i.e. road traffic and the urban area of the city of Stockholm. The investigated fields are used for the cultivation of cereal crops and have not been previously fertilized with digested sludge. Fields at different distances from the city center of Stockholm and at distances close and remote from major roads were selected. The potential effect on PCDD and PCDF concentrations in these fields was calculated assuming that they were subjected to one tonne sewage sludge fertilization per year. The concentrations of PCDDs and PCDFs in the sludge were based on analysis of digested sludge collected over a long period at the four largest sewage treatment plants in the County of Stockholm.
1213
1214
MATERIALS AND METHODS The soil samples were collected along a gradient with a logarithmically Increasing distance from the city center of Stockholm in the dominating wind direction, I.e. towards the north-east, in May, 1989 (see Figure 1). The soil samples were taken with a microarthropod drill, with a sampling area of 10 cm2. Within one square metre of field area, 10 cores were taken to the sole of the plough, i.e. at a depth of 15o25 cm (approx. 10 cm dried core) depending on the stoniness. The sampling area was located 10 metres In from the edge of the field In order to avoid possible edge effects. The 10 cores were homogenized and a subsample (approx. 200 g dry weight; dw) was taken from this homogenate for analysis. For extraction, cleaning and analytical procedures see Zebf.ihr el' al. (1989).
Fig 1. Map showing sampling locations.
Four pairs of samples were taken. Each pair was taken at approximately the same distance from the city centre of Stockholm (see Table 1). One sample from each pair was taken as close to a major road as possible, and the other at a large distance from the road. On the map (Figure 1) the sample pairs are numbered 1-4 and samples taken in the vicinity of a road are marked with an "a" and samples taken at a distance from a road are marked with a "b ~. The sewage sludge samples were collected from the sewage treatment plants Henriksdal (approx. 560 000 personal equlvivalents; pe) Bromma/Akeshov (approx.250 000 pe), KSppala (approx.450 000 pe) and Himmerfj~trdens (approx.250 000 pe). A subsample of digested and dewatered sludge (approx. 300 g wet weight; ww) was taken each week from the end of May until the end of August, 1989. In other words, sampling was carried out continuously for about 13 weeks. The samples were homogenized and a subsample (approx. 200 g ww) was extracted from this homogenate for analysis using the method referred to above. The dry weight of all samples was determined (oven drying at 105 °C for 24 h) and the organic weight (o.w.) was determined by weighing the remainder of the sample after heating the material at 500 °C for 12 h.
1215
Tab 1. Sampling locations for soil samples
Sampling location No.
Distance from centre of Stockholm (km)
Distance from major road (km)
la
9
0.03
lb
8
0.5
2a
17
0.03
2b
13
3
3a
26
0.03
3b
27
2
4a
44
0.03
4b
41
4
a = near road b = not near road
RESULTS AND DISCUSSION
Sludge and soft concent~fions The total concentrations of PCDD and PCDF in the 8 soil samples and the 4 sludge samples, expressed in toxic equivalents (TEQ) according to the Nordic model, are presented In Figure 2. They are also Isomer-specifically described in Table 1 and 2. The mean concentration in the sludge samples was 79 pg TEQ/g (o.w.). These samples displayed a concentration variation of between 41 and 130 pg TEQ/g (o.w.). This variation cannot be explained by variation of organic matter, which did not exceed 3 % between the different samples (46-49 % of the dry weight consisted of organic matter). The different sewage treatment works have therefore been exposed to different loads during the sample collection period. The soil samples taken close to major roads (la-4a) vary between 13 and 49 pg TEQ/g (o.w.) and the four samples (lb-4b) which were not taken close to major roads vary between 9 and 32 pg TEQ/g (o.w.). Two factors appear to influence the PCDD and PCDF concentrations in the arable soil. The first Is proximity to the possible "point source', city of Stockholm. This results in sample l b having a higher content than samples 2b, 3b ar, d 4b. The second factor appears to be proximity to major roads, which probably explains why the "a" samples are generally higher than the "b" samples, with the exception of location 4 where the difference between "a" and "b" sample Is small. The mean concentration for the "a" samples, i.e. those situated near roads, is 29 pg TEQ/g (o.w.) while 17 pg TEQ/g (o.w.) Is the mean for the "b" samples, i.e. the fields which are not situated in the vicinity of roads.
Significance of digested sludge as contributors to the PCDD and PCDF concentrations in arable soft Presented below are two calculations of how much PCDD and PCDF is supplied to a field which Is annually treated with digested sludge, considered in relation to the initial concentration. As a rule in the area, digested sludge is applied only once every five years and then In an amount of about 5 tonnes dry weight/hectare. In the following calculation, however, an annual supply of one tonne dry weight/hectare has been assumed for the sake of simplicity. Two initial concentrations in the arable soil have been used in the calculation. The first is based on a mean value of the 4 fields which are situated close to major roads and the second on a mean value of the 4 fields which are not situated close to roads.
1216
A
d
65 58 5 52 45 5 39 32 5 26 19 5 t3 65 B
II+i Jib Jla
J2b J2a
|
|l
J~ J~
J~ J~
O
ILl }--
52 45 5 39 32 5 26 t9 5 13 65 B
m SL9
SLI8
SLil
SL12
Fig 2 The total concentration of PCDD and PCDF in soil (J1-J4; a = near road, b = not near road) and sludge samples (SL9 SL12) expressed in pg toxic equivalents (Nordic model), TEQ/g organic weight (ow) (For sampling locations see Figure 1; SL9 = Bromma-Akeshov sewage treatment works, SL10 = Henriksdal sewage treatment works, SL11 = HimmerfjSrd sewage treatment works, SL12 = K~tppala sewage treatment works)
1217
Tab 2. The concentrations ( W g o.w. and pg TEG/g o.u.) of PCDD and PCDF in the d i f f e r e n t s o i l samples. (Tk,o s i g n i f i c a n t figures.)
Jlb
Jla
J2b
J2a
J3b
J3a
J4b
J4a
COMPOUND TEQ
TEQ
TEQ
26.4 262.4
2.6
20.6 307.0
2.1
3.1 ~.3
3.1
3.1 1~.6
3.1
1~-/123~-P~F 2~-P~F TotP~F
20.4 12.6 214.7
0.2 6.3
17.8 16.4 2~.1
0.2 8.2
18.6 4.0 115.4
I~-P~D TOrPiD
18.3 208.2
9.2
17.7 240.0
8.9
l~4~-/1~4~-HxCDF20.8 123678-HxCOF 19.8 123789-HxCOF 0.8 234678-HxCOF 12.5 Tot HxCDF 1~.2
2.1 2.0 0.1 1.3
22.0 18.8 0.5 14.3 2~.6
123478-HxCDD 123678-HxCOD 123789-HxCDD TOt HxCDD
6.7 13.1 11.0 1~.8
0.7 1.3 1.1
7.0 ~.7 15.4 287.4
1234678- HpCDF 1234789- HpCDF Tot HpCDF
38.9 2.9 38.9
0.4 0.03
12]4768- HpCDD Tot HpCDO
77.8 167.8
0.8
2348-/2378-TCDF Tot TCDF 2378-TCOD Tot TCDD
OCDF
<7.4
38.9 <1.0 38.9 297.7 563.2
1.4
1.1 ~.5
1.1
<3.0 ~.9
0.2 2.0
12.5 9.6 1~.6
0.1 4.8
7.4 3.1 ~.5
3.7 45.6
1.9
7.7 110.2
3.9
<2.6 ~.2
2.2 1.9 0.0 1.4
7.8 9.2 <2.5 <2.5 54.1
0.8 0.9
13.3 8.9 3.8 5.6 109.5
1.3 0.9 0.4 0.6
6.5 7.7 <0.6 3.2 53.0
0.7 0.8
0.7 2.5 1.5
7.0 3.3 <1.6 ~.8
0.7 0.3
4.3 7.3 5.0 110.0
0.4 0.7 0.5
3.9 3.1 2.5 42.6
0.4 0.3 0.3
0.4
93.8 <2.0 93.8
0.9
131.2 5.4 187.2
1.3 0.1
53.5 <1.0 60.2
0.5
0.5
53.8 118.9
0.5
43.3 83.2
0.4
19.0
0.02
<3.5
0.9
TEQ
13.5 185.7
3.0
8.7 137.6
TEQ
<2.2 52.3
53.7 107.0 <3.0
57.5 454.2
5.7
0.1 1.5
0.3
<3.0
TEQ
TEQ
34.8 327.6
3.5
8.4 116.4
2.2 217.1
2.2
<1.7 125.2
32.1 26.5 457.0
0.3 13.3
11.5 5.9 110.6
0.1 2.9
9.5 7.7 ~.8
0.1 3.9
15.5 4~.3
7.8
7.4 ~.7
3.7
6.0 ~.3
3.0
29.1 ~.9 1.9 21.5 3~.6
2.9 2.9 0.2 2.2
18.4 11.5 <0.8 3.3 ~.5
1.8 1.1
9.4 8.5 <0.6 5.2 ~.1
0.9 0.8
8.0 32.2 16.6 ~9.5
0.8 3.2 1.7
5.0 8.4 7.1 1~.4
0.5 0.8 0.7
4.5 7.2 5.7 ~.3
0.4 0.7 0.6
0.6
134.2 <6.3 134.2
1.3
31.4 0.3 <2 31.4
4.9
67.6 134.2
0.7
61.7 <1.0 61.7 491.5 904.1 <2.9
0.8
TEQ
10.0 109.3
1.0
<0.6 36.9
0.3
<13.5
65.6 137.2
0.5
0.7
<11
OCOO
155.1
0.2
1157
1.2
112.5
0.1
116.7
0.1
525.8
0.5
2659
2.7
450.7
0.5
321.3
0.3
TOTAL
1~B8
31
3;~59
37
811
9
1191
18
1369
12
5761
49
1~48
15
985
13
1218
Tub 3. The concentrations (pg/g o.w. and pg TEQ/g o.w.) of PCDD and PCOF in the d i f f e r e n t sewage studge samples. (Two s i g n i f i c a n t figures.)
SL9
SLIO
SL11
SL12
COMPOUND TEQ
TEQ
TEQ
TEQ
2348-/2378- TCDF Tot T(:DF
9.7 67.4
1.0
10.8 81.6
1.1
9.8 52.5
1.0
14.6 92.7
1.5
2378- TCOD Tot TCDD
1.5 76.9
1.5
2.2 59.3
2.2
1.7 87.5
1.7
1.3 41.5
1.3
12348-/12378-PnCDF 23478-PNCDF Tot PnCDF
5.2 7.1 86.5
0.1 3.5
10.3 15.9 126.7
0.1 7.9
6.8 7.7 71.4
0.05 3.8
6.1 8.4 114.3
0.1 4.2
12378-PNC00 Tot PnCDO
6.2 322.6
3.1
11.3 211.7
5.6
7.9 577.6
3.9
3.8 220.9
1.9
123479-/123478-HxCDF 123678-llxCDF 123789-HxCDF 23~78- HxCDF Tot HxCDF
11.6 10.3 1.7 11.1 200.7
1.2 1.0 0.2 1.1
21.6 27.2 1.4 36.2 351.7
2.2 2.7 0.1 3.6
11.5 11.7 1.5 12.0 267.9
1.2 1.2 0.2 1.2
6.9 7.7 <1.0 8.1 220.0
0.7 0.8
123478-HxCDD 123678-HxCOD 123789-Hx(:DD Tot HxCDD
4.7 68.8 13.3 480.2
0.5 6.9 1.3
11.2 53.9 26.0 558.9
1.1 5.4 2.6
11.8 210.7 36.4 1904.1
1.2 21.1 3.6
2.5 23.5 9.1 272.1
1234678-HpCDF 1Z34789-HpCDF Tot HpCDF
84.8 1.1 88.6
0.8 0.01
101.1 1.3 110.3
1.0 0.01
90.2 1.4 101.7
0.9 0.01
1234768-HPCDD Tot HpCDD
2167.0 6234.8
21.7
1495.4 2854.9
15.0 6102.7 8997.3
61.0
OCDF
5.0
0.01
8.7
0.01
OCDD
32864.4
TOTAL
/droll
<2.4
32.9 16354.4
75
22535
16.4 30765.7
67
491.156
23.4 <2.3 23.4 1324.1 2762.2
0.3 2.4 0.9
0.2
13.2
<5.5
30.8 12829.2
133
0.8
18816
12.8
41
1219
On the conditions set out below, the following results are obtained when the mean concentration value of PCDD and PCDF on the four fields situated near malor roads is utilized:
Soil density (kg dw/m3) = Volume of top soil on 1 hectare (100m*100m*0.1 m) (m3) = The mass of top soil on 1 hectare (g dw) = Mean dioxin concentration in top soil (pg TEQ/g dw) = Total content of dloxin in top soil layer (mg TEQ/hectare = Mean dioxin concentration in sludge samples (pg TEQ/g dw) = Annual supply of sludge to top soil (tonne dw/hectare) =
1200 1000 1.20"109 1.58 1.90
37.7 1
Amount of dioxin supplied annually in per cent of total content of top soil = Number of years it takes to supply as much PCDD and PCDF as the soil initially contains =
50
Under the conditions set out below, the following results are obtained when the mean concentration value of PCDD and PCDF from the 4 fields which are not Fituat~d close to malor roads is utilized:
Soil density (kg dw/m3) = Volume of top soil on 1 hectare (100m*100m*0.1m) (m3) = The mass of top soil on 1 hectare (g dw) = Mean dioxin concentration In top soil (pg TEQ/g dw)= Total content of dioxin in top soil layer (mg TEQ/hectare = Mean dioxin concentration in sludge samples (pg TEQ/g dw) = Annual supply of sludge to top soil (tonne dw/hectare) =
1200 1000 1.20"109 0.98 1.2 37.7 1
Amount of dioxln supplied annually in per cent of total content of top soil = Number of years It takes to supply as much PCDD and PCDF as the soil Initially contains =
31
Consequently, 2 % and 3 % respectively of the initial concentrations of PCDD and PCDF in the fields are supplied annually with the digested sludge. Moreover, it takes 50 years and 30 years respectively to supply as much PCDD and PCDF as is present in the fields initially. Sacchi et.al, find that the uptake of 2,3,7,8-TCDD to the aerial part of maize and beans from cotaminated soil is low and further reduced by addition of peat. The soils of the fields in this investigation are comparatively low in organic content (5-6% of the dry weight of soil passed through a 1 mm. sieve). Finally it should be pointed out that in these calculations no estimate of the degradation of PCDD and PCDF in soil has been Included. Neither has the possibility of transformation from less toxic to more toxic Isomers by photodegradation been assessed. The potential uptake of PCDD/Fs by plant roots is likely to be dependant of the concentration of pollutants in the organic matter rather then the total amounts present. Since sludge fertilization adds not only pollutants but also increases the soil organic matter the increase in concentration is slower than the Increase in total amounts. The average organic matter content of the soil is 5-6% of dry weight (approx. 72000 kg organic matter/ha). An addition of 1 tonne sludge (approx. 480 kg organic matter/ha) represents a total addition of approx. 0.7 % organic matter to the total soil organic matter. The decomposition rate of the organic matter in sludge has been estimated to be as low as 15% per year. At fields close to roads the concentration of TEQ (pg/g o.w.) In sludge organic matter is 2.7 times higher than in the soil organic matter. At fields distant from roads the concentration in sludge is 4.7 times higher than in the soil organic matter. If steady state is assumed for the initial amount of organic matter, 15% annual loss of organic matter from sludge the time required to double concentrations of
1220
PCDD/Fs will be 37 years at fields distant from roads and 62 years at fields close to roads. This will be a conservative estimate since no degradation of PCDD/Fs is assumed. Revolatilization of PCDD/Fs from soil and soil deposition on leaf surfaces are likely to be affected according to soil concentrations. Reichl et. al. have shown that the vicinity to air emission sources, affects the levels of PCDD/F in spruce needles. The Importance of soil concentration in relation to other uptake routs e.g. aerial deposition if difficult to assess since no good estimates of aerial deposition in the Investigated area are available. ACKNOWLEDGMENTS We like to acknowledge KSppala, Himmerfj&rdens and Stockholm Water and Wastewater Works which financially supported the study. REFERENCES Broman, D., C. N&f, Co Rolff and Y. ZebOhr (1989b). Analys av polyklorerade dibenso-p-dioxiner (PCDD) och polyklorerade dibensofuraner (PCDF) I jord och r6tslam fr&n Stockholms I&n. Stockolms vattenoch avloppsverk (Stockholm Water and Wastewater Works). Report, In Swedish. Lamparskl, L. L., T. J. Nestrick and V. A. Stenger (1984). Presence of chlorodlbenzo dloxins In a sealed 1933 sample of dried municipal sewage sludge. Chemosphere, 13, 361-365. N~f, C., Broman, D., Ishaq, R. and Zeb0hr, Y. (1990) PCDDs and PCDFs in water, sludge and air samples from various levels in a waste water treatment plant with respect to composition changes and total flux. (Submitted for publication). Reischl, A., Reissinger, M., Thoma, H., Hutzinger, O. (1989) Accumulation of organic air contituents by plant surfaces: Part IV. Plant surfaces: A sampling system for athmospherlc polychlorodibenzo-p-dioxin (PCDD) and polychlorodibenzo-p-furan (PCDF). Chemosphere, vol. 18, nos.t-6, pp. 561-568. Rappe, C., L-O. Kjeller and R. Andersson (1989). Analyses of PCDDs and PCDFs in sludge and water samples. Chemosphere, 19, 13-20. Sacchi, G.A., Vigano, P., Fortunati, G., Cocucci, S.M. (1986) Accumulation of 2,3,7,8-tetrachlorodibenzo-pdioxin from soil and nutrient solution by bean and maize plants. Experientia, 5,586-588. Zeb0hr, Y., C. N~if, D. Broman, K. Lexdn, C. ColmsjO and C. (~stman (1988). Sampling techniques and clean up procedures for some complex environmental samples with respect to PCDDs and PCDFs and other organic contaminants. Chemosphere, 19, 39-44.
(Received
in Germany
30 April 1990; accepted
5 November
1990)
pp 1213-1220,
1990
0045-6535/90 $3.00 + .00 Pergamon Press plc
ANALYSIS OF POLYCHLORINATED DIBENZO'P'DIOXINS (PCDD) AND POLYCHLORINATED DIBENZOFURANS (PCDF) IN SOIL AND DIGESTED SEWAGE SLUDGE FROM STOCKHOLM, SWEDEN Dag Broman*, Carina NM*#, Carl Rolff*and Yngve Zeb0hr*# *Aquatic Chemical Ecotoxicology, Department of Zoology and #Department of Analytical Chemistry University of Stockholm, 106 91 Stockholm, Sweden
ABSTRACT In this investigation the content of PCDDs and PCDFs in sewage sludge samples and top soil from fields situated in the County of Stockholm has been investigated. Further, the contribution of PCDDs and PCDFs to the fields from sewage sludge is compared with the contribution from two non-point emission sources i.e. road traffic and the urban area of the city of Stockholm. The mean concentration in four analyzed sludge samples is 79 pg TEQ/g (organic weight; o.w.). Soil samples taken close to major roads vary between 13 and 49 pg TEQ/g (o.w.) and soil samples (t b-4b) which were not taken close to major roads vary between 9 and 32 pg TEQ / g (o.w.). The results indicate that both road traffic and outlets from the urban area influence the PCDD and PCDF concentrations in the arable soil. Fertilization with sludge (1 tonne dry weight/hectare and year) raise the initial soil concentrations of PCDD and PCDF In the fields by approx. 2 - 3 %.
INTRODUCTION In Sweden, and many other countries, there is a continuous discussion concerning the significance of sewage sludge fertilization of cultivated land in terms of contamination of the soil and crops with dibenzop-dioxins (PCDDs) and dibenzofurans (PCDFs). Several studies have investigated the concentrations of these pollutants in different types of sewage sludge samples (Lamparski et al., 1984 ; N~tf et al., 1990; Rappe et al., 1989). The purpose of this investigation was to determine the content of PCDDs and PCDFs in sewage sludge samples and top soil from fields situated in the County of Stockholm. Further, the contribution of PCDDs and PCDFs to the fields from sewage sludge were to be compared with the contribution from two nonpoint emission sources i.e. road traffic and the urban area of the city of Stockholm. The investigated fields are used for the cultivation of cereal crops and have not been previously fertilized with digested sludge. Fields at different distances from the city center of Stockholm and at distances close and remote from major roads were selected. The potential effect on PCDD and PCDF concentrations in these fields was calculated assuming that they were subjected to one tonne sewage sludge fertilization per year. The concentrations of PCDDs and PCDFs in the sludge were based on analysis of digested sludge collected over a long period at the four largest sewage treatment plants in the County of Stockholm.
1213
1214
MATERIALS AND METHODS The soil samples were collected along a gradient with a logarithmically Increasing distance from the city center of Stockholm in the dominating wind direction, I.e. towards the north-east, in May, 1989 (see Figure 1). The soil samples were taken with a microarthropod drill, with a sampling area of 10 cm2. Within one square metre of field area, 10 cores were taken to the sole of the plough, i.e. at a depth of 15o25 cm (approx. 10 cm dried core) depending on the stoniness. The sampling area was located 10 metres In from the edge of the field In order to avoid possible edge effects. The 10 cores were homogenized and a subsample (approx. 200 g dry weight; dw) was taken from this homogenate for analysis. For extraction, cleaning and analytical procedures see Zebf.ihr el' al. (1989).
Fig 1. Map showing sampling locations.
Four pairs of samples were taken. Each pair was taken at approximately the same distance from the city centre of Stockholm (see Table 1). One sample from each pair was taken as close to a major road as possible, and the other at a large distance from the road. On the map (Figure 1) the sample pairs are numbered 1-4 and samples taken in the vicinity of a road are marked with an "a" and samples taken at a distance from a road are marked with a "b ~. The sewage sludge samples were collected from the sewage treatment plants Henriksdal (approx. 560 000 personal equlvivalents; pe) Bromma/Akeshov (approx.250 000 pe), KSppala (approx.450 000 pe) and Himmerfj~trdens (approx.250 000 pe). A subsample of digested and dewatered sludge (approx. 300 g wet weight; ww) was taken each week from the end of May until the end of August, 1989. In other words, sampling was carried out continuously for about 13 weeks. The samples were homogenized and a subsample (approx. 200 g ww) was extracted from this homogenate for analysis using the method referred to above. The dry weight of all samples was determined (oven drying at 105 °C for 24 h) and the organic weight (o.w.) was determined by weighing the remainder of the sample after heating the material at 500 °C for 12 h.
1215
Tab 1. Sampling locations for soil samples
Sampling location No.
Distance from centre of Stockholm (km)
Distance from major road (km)
la
9
0.03
lb
8
0.5
2a
17
0.03
2b
13
3
3a
26
0.03
3b
27
2
4a
44
0.03
4b
41
4
a = near road b = not near road
RESULTS AND DISCUSSION
Sludge and soft concent~fions The total concentrations of PCDD and PCDF in the 8 soil samples and the 4 sludge samples, expressed in toxic equivalents (TEQ) according to the Nordic model, are presented In Figure 2. They are also Isomer-specifically described in Table 1 and 2. The mean concentration in the sludge samples was 79 pg TEQ/g (o.w.). These samples displayed a concentration variation of between 41 and 130 pg TEQ/g (o.w.). This variation cannot be explained by variation of organic matter, which did not exceed 3 % between the different samples (46-49 % of the dry weight consisted of organic matter). The different sewage treatment works have therefore been exposed to different loads during the sample collection period. The soil samples taken close to major roads (la-4a) vary between 13 and 49 pg TEQ/g (o.w.) and the four samples (lb-4b) which were not taken close to major roads vary between 9 and 32 pg TEQ/g (o.w.). Two factors appear to influence the PCDD and PCDF concentrations in the arable soil. The first Is proximity to the possible "point source', city of Stockholm. This results in sample l b having a higher content than samples 2b, 3b ar, d 4b. The second factor appears to be proximity to major roads, which probably explains why the "a" samples are generally higher than the "b" samples, with the exception of location 4 where the difference between "a" and "b" sample Is small. The mean concentration for the "a" samples, i.e. those situated near roads, is 29 pg TEQ/g (o.w.) while 17 pg TEQ/g (o.w.) Is the mean for the "b" samples, i.e. the fields which are not situated in the vicinity of roads.
Significance of digested sludge as contributors to the PCDD and PCDF concentrations in arable soft Presented below are two calculations of how much PCDD and PCDF is supplied to a field which Is annually treated with digested sludge, considered in relation to the initial concentration. As a rule in the area, digested sludge is applied only once every five years and then In an amount of about 5 tonnes dry weight/hectare. In the following calculation, however, an annual supply of one tonne dry weight/hectare has been assumed for the sake of simplicity. Two initial concentrations in the arable soil have been used in the calculation. The first is based on a mean value of the 4 fields which are situated close to major roads and the second on a mean value of the 4 fields which are not situated close to roads.
1216
A
d
65 58 5 52 45 5 39 32 5 26 19 5 t3 65 B
II+i Jib Jla
J2b J2a
|
|l
J~ J~
J~ J~
O
ILl }--
52 45 5 39 32 5 26 t9 5 13 65 B
m SL9
SLI8
SLil
SL12
Fig 2 The total concentration of PCDD and PCDF in soil (J1-J4; a = near road, b = not near road) and sludge samples (SL9 SL12) expressed in pg toxic equivalents (Nordic model), TEQ/g organic weight (ow) (For sampling locations see Figure 1; SL9 = Bromma-Akeshov sewage treatment works, SL10 = Henriksdal sewage treatment works, SL11 = HimmerfjSrd sewage treatment works, SL12 = K~tppala sewage treatment works)
1217
Tab 2. The concentrations ( W g o.w. and pg TEG/g o.u.) of PCDD and PCDF in the d i f f e r e n t s o i l samples. (Tk,o s i g n i f i c a n t figures.)
Jlb
Jla
J2b
J2a
J3b
J3a
J4b
J4a
COMPOUND TEQ
TEQ
TEQ
26.4 262.4
2.6
20.6 307.0
2.1
3.1 ~.3
3.1
3.1 1~.6
3.1
1~-/123~-P~F 2~-P~F TotP~F
20.4 12.6 214.7
0.2 6.3
17.8 16.4 2~.1
0.2 8.2
18.6 4.0 115.4
I~-P~D TOrPiD
18.3 208.2
9.2
17.7 240.0
8.9
l~4~-/1~4~-HxCDF20.8 123678-HxCOF 19.8 123789-HxCOF 0.8 234678-HxCOF 12.5 Tot HxCDF 1~.2
2.1 2.0 0.1 1.3
22.0 18.8 0.5 14.3 2~.6
123478-HxCDD 123678-HxCOD 123789-HxCDD TOt HxCDD
6.7 13.1 11.0 1~.8
0.7 1.3 1.1
7.0 ~.7 15.4 287.4
1234678- HpCDF 1234789- HpCDF Tot HpCDF
38.9 2.9 38.9
0.4 0.03
12]4768- HpCDD Tot HpCDO
77.8 167.8
0.8
2348-/2378-TCDF Tot TCDF 2378-TCOD Tot TCDD
OCDF
<7.4
38.9 <1.0 38.9 297.7 563.2
1.4
1.1 ~.5
1.1
<3.0 ~.9
0.2 2.0
12.5 9.6 1~.6
0.1 4.8
7.4 3.1 ~.5
3.7 45.6
1.9
7.7 110.2
3.9
<2.6 ~.2
2.2 1.9 0.0 1.4
7.8 9.2 <2.5 <2.5 54.1
0.8 0.9
13.3 8.9 3.8 5.6 109.5
1.3 0.9 0.4 0.6
6.5 7.7 <0.6 3.2 53.0
0.7 0.8
0.7 2.5 1.5
7.0 3.3 <1.6 ~.8
0.7 0.3
4.3 7.3 5.0 110.0
0.4 0.7 0.5
3.9 3.1 2.5 42.6
0.4 0.3 0.3
0.4
93.8 <2.0 93.8
0.9
131.2 5.4 187.2
1.3 0.1
53.5 <1.0 60.2
0.5
0.5
53.8 118.9
0.5
43.3 83.2
0.4
19.0
0.02
<3.5
0.9
TEQ
13.5 185.7
3.0
8.7 137.6
TEQ
<2.2 52.3
53.7 107.0 <3.0
57.5 454.2
5.7
0.1 1.5
0.3
<3.0
TEQ
TEQ
34.8 327.6
3.5
8.4 116.4
2.2 217.1
2.2
<1.7 125.2
32.1 26.5 457.0
0.3 13.3
11.5 5.9 110.6
0.1 2.9
9.5 7.7 ~.8
0.1 3.9
15.5 4~.3
7.8
7.4 ~.7
3.7
6.0 ~.3
3.0
29.1 ~.9 1.9 21.5 3~.6
2.9 2.9 0.2 2.2
18.4 11.5 <0.8 3.3 ~.5
1.8 1.1
9.4 8.5 <0.6 5.2 ~.1
0.9 0.8
8.0 32.2 16.6 ~9.5
0.8 3.2 1.7
5.0 8.4 7.1 1~.4
0.5 0.8 0.7
4.5 7.2 5.7 ~.3
0.4 0.7 0.6
0.6
134.2 <6.3 134.2
1.3
31.4 0.3 <2 31.4
4.9
67.6 134.2
0.7
61.7 <1.0 61.7 491.5 904.1 <2.9
0.8
TEQ
10.0 109.3
1.0
<0.6 36.9
0.3
<13.5
65.6 137.2
0.5
0.7
<11
OCOO
155.1
0.2
1157
1.2
112.5
0.1
116.7
0.1
525.8
0.5
2659
2.7
450.7
0.5
321.3
0.3
TOTAL
1~B8
31
3;~59
37
811
9
1191
18
1369
12
5761
49
1~48
15
985
13
1218
Tub 3. The concentrations (pg/g o.w. and pg TEQ/g o.w.) of PCDD and PCOF in the d i f f e r e n t sewage studge samples. (Two s i g n i f i c a n t figures.)
SL9
SLIO
SL11
SL12
COMPOUND TEQ
TEQ
TEQ
TEQ
2348-/2378- TCDF Tot T(:DF
9.7 67.4
1.0
10.8 81.6
1.1
9.8 52.5
1.0
14.6 92.7
1.5
2378- TCOD Tot TCDD
1.5 76.9
1.5
2.2 59.3
2.2
1.7 87.5
1.7
1.3 41.5
1.3
12348-/12378-PnCDF 23478-PNCDF Tot PnCDF
5.2 7.1 86.5
0.1 3.5
10.3 15.9 126.7
0.1 7.9
6.8 7.7 71.4
0.05 3.8
6.1 8.4 114.3
0.1 4.2
12378-PNC00 Tot PnCDO
6.2 322.6
3.1
11.3 211.7
5.6
7.9 577.6
3.9
3.8 220.9
1.9
123479-/123478-HxCDF 123678-llxCDF 123789-HxCDF 23~78- HxCDF Tot HxCDF
11.6 10.3 1.7 11.1 200.7
1.2 1.0 0.2 1.1
21.6 27.2 1.4 36.2 351.7
2.2 2.7 0.1 3.6
11.5 11.7 1.5 12.0 267.9
1.2 1.2 0.2 1.2
6.9 7.7 <1.0 8.1 220.0
0.7 0.8
123478-HxCDD 123678-HxCOD 123789-Hx(:DD Tot HxCDD
4.7 68.8 13.3 480.2
0.5 6.9 1.3
11.2 53.9 26.0 558.9
1.1 5.4 2.6
11.8 210.7 36.4 1904.1
1.2 21.1 3.6
2.5 23.5 9.1 272.1
1234678-HpCDF 1Z34789-HpCDF Tot HpCDF
84.8 1.1 88.6
0.8 0.01
101.1 1.3 110.3
1.0 0.01
90.2 1.4 101.7
0.9 0.01
1234768-HPCDD Tot HpCDD
2167.0 6234.8
21.7
1495.4 2854.9
15.0 6102.7 8997.3
61.0
OCDF
5.0
0.01
8.7
0.01
OCDD
32864.4
TOTAL
/droll
<2.4
32.9 16354.4
75
22535
16.4 30765.7
67
491.156
23.4 <2.3 23.4 1324.1 2762.2
0.3 2.4 0.9
0.2
13.2
<5.5
30.8 12829.2
133
0.8
18816
12.8
41
1219
On the conditions set out below, the following results are obtained when the mean concentration value of PCDD and PCDF on the four fields situated near malor roads is utilized:
Soil density (kg dw/m3) = Volume of top soil on 1 hectare (100m*100m*0.1 m) (m3) = The mass of top soil on 1 hectare (g dw) = Mean dioxin concentration in top soil (pg TEQ/g dw) = Total content of dloxin in top soil layer (mg TEQ/hectare = Mean dioxin concentration in sludge samples (pg TEQ/g dw) = Annual supply of sludge to top soil (tonne dw/hectare) =
1200 1000 1.20"109 1.58 1.90
37.7 1
Amount of dioxin supplied annually in per cent of total content of top soil = Number of years it takes to supply as much PCDD and PCDF as the soil initially contains =
50
Under the conditions set out below, the following results are obtained when the mean concentration value of PCDD and PCDF from the 4 fields which are not Fituat~d close to malor roads is utilized:
Soil density (kg dw/m3) = Volume of top soil on 1 hectare (100m*100m*0.1m) (m3) = The mass of top soil on 1 hectare (g dw) = Mean dioxin concentration In top soil (pg TEQ/g dw)= Total content of dioxin in top soil layer (mg TEQ/hectare = Mean dioxin concentration in sludge samples (pg TEQ/g dw) = Annual supply of sludge to top soil (tonne dw/hectare) =
1200 1000 1.20"109 0.98 1.2 37.7 1
Amount of dioxln supplied annually in per cent of total content of top soil = Number of years It takes to supply as much PCDD and PCDF as the soil Initially contains =
31
Consequently, 2 % and 3 % respectively of the initial concentrations of PCDD and PCDF in the fields are supplied annually with the digested sludge. Moreover, it takes 50 years and 30 years respectively to supply as much PCDD and PCDF as is present in the fields initially. Sacchi et.al, find that the uptake of 2,3,7,8-TCDD to the aerial part of maize and beans from cotaminated soil is low and further reduced by addition of peat. The soils of the fields in this investigation are comparatively low in organic content (5-6% of the dry weight of soil passed through a 1 mm. sieve). Finally it should be pointed out that in these calculations no estimate of the degradation of PCDD and PCDF in soil has been Included. Neither has the possibility of transformation from less toxic to more toxic Isomers by photodegradation been assessed. The potential uptake of PCDD/Fs by plant roots is likely to be dependant of the concentration of pollutants in the organic matter rather then the total amounts present. Since sludge fertilization adds not only pollutants but also increases the soil organic matter the increase in concentration is slower than the Increase in total amounts. The average organic matter content of the soil is 5-6% of dry weight (approx. 72000 kg organic matter/ha). An addition of 1 tonne sludge (approx. 480 kg organic matter/ha) represents a total addition of approx. 0.7 % organic matter to the total soil organic matter. The decomposition rate of the organic matter in sludge has been estimated to be as low as 15% per year. At fields close to roads the concentration of TEQ (pg/g o.w.) In sludge organic matter is 2.7 times higher than in the soil organic matter. At fields distant from roads the concentration in sludge is 4.7 times higher than in the soil organic matter. If steady state is assumed for the initial amount of organic matter, 15% annual loss of organic matter from sludge the time required to double concentrations of
1220
PCDD/Fs will be 37 years at fields distant from roads and 62 years at fields close to roads. This will be a conservative estimate since no degradation of PCDD/Fs is assumed. Revolatilization of PCDD/Fs from soil and soil deposition on leaf surfaces are likely to be affected according to soil concentrations. Reichl et. al. have shown that the vicinity to air emission sources, affects the levels of PCDD/F in spruce needles. The Importance of soil concentration in relation to other uptake routs e.g. aerial deposition if difficult to assess since no good estimates of aerial deposition in the Investigated area are available. ACKNOWLEDGMENTS We like to acknowledge KSppala, Himmerfj&rdens and Stockholm Water and Wastewater Works which financially supported the study. REFERENCES Broman, D., C. N&f, Co Rolff and Y. ZebOhr (1989b). Analys av polyklorerade dibenso-p-dioxiner (PCDD) och polyklorerade dibensofuraner (PCDF) I jord och r6tslam fr&n Stockholms I&n. Stockolms vattenoch avloppsverk (Stockholm Water and Wastewater Works). Report, In Swedish. Lamparskl, L. L., T. J. Nestrick and V. A. Stenger (1984). Presence of chlorodlbenzo dloxins In a sealed 1933 sample of dried municipal sewage sludge. Chemosphere, 13, 361-365. N~f, C., Broman, D., Ishaq, R. and Zeb0hr, Y. (1990) PCDDs and PCDFs in water, sludge and air samples from various levels in a waste water treatment plant with respect to composition changes and total flux. (Submitted for publication). Reischl, A., Reissinger, M., Thoma, H., Hutzinger, O. (1989) Accumulation of organic air contituents by plant surfaces: Part IV. Plant surfaces: A sampling system for athmospherlc polychlorodibenzo-p-dioxin (PCDD) and polychlorodibenzo-p-furan (PCDF). Chemosphere, vol. 18, nos.t-6, pp. 561-568. Rappe, C., L-O. Kjeller and R. Andersson (1989). Analyses of PCDDs and PCDFs in sludge and water samples. Chemosphere, 19, 13-20. Sacchi, G.A., Vigano, P., Fortunati, G., Cocucci, S.M. (1986) Accumulation of 2,3,7,8-tetrachlorodibenzo-pdioxin from soil and nutrient solution by bean and maize plants. Experientia, 5,586-588. Zeb0hr, Y., C. N~if, D. Broman, K. Lexdn, C. ColmsjO and C. (~stman (1988). Sampling techniques and clean up procedures for some complex environmental samples with respect to PCDDs and PCDFs and other organic contaminants. Chemosphere, 19, 39-44.
(Received
in Germany
30 April 1990; accepted
5 November
1990)