Association of PAHs, PCBs, 137Cs, and 210Pb with clay, silt, and organic carbon in sediments

e

Pergamon

Waf. Sci. Tech. Vol. 34, No. 7-8, pp. 29-35, 1996. Copyright © 1996 IAWQ. Published by Elsevier Science Ltd Printed in Great Britain. All rights reserved. 0273-1223/96 $15'00 + 0'00

PH: S0273-1223(96)00719-6

ASSOCIATION OF PAHs, PCBs, 137Cs, AND 210Pb WITH CLAY, SILT, AND ORGANIC CARBON IN SEDIMENTS I. A. Ab Razak, A. Li, and E. R. Christensen Department of Civil Engineering and Mechanics, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA

ABSTRACT The association of PAHs, PCBs, 137Cs, and 210pb with various components of sediments, i.e., clay, silt, and organic carbon is determined. The work is based on the data from 6 deep (2-3 m) vibra cores collected from a stretch of the Kinnickinnic River running through Milwaukee, Wisconsin, USA. Priority organics were determined by extraction, clean-up, and gas chromatography with either a mass selective (PAHs) or an electron capture (PCBs) detector. Loss on ignition, porosity, and radionuclide analyses were carried out by standard techniques, and the association of the variables was investigated by principal component analysis. The results indicate that PAHs are associated with organic carbon, porosity and silt. Both 137Cs and PCBs are associated with clay but not with organic carbon. 210pb is mainly associated with the organic fraction, but covaries also to some extent with clay. Copyright © 1996 IAWQ. Published by Elsevier Science Ltd.

KEYWORDS PAHs; PCBs; 137Cs; 21OPb; sediments; organic carbon; clay; silt. INTRODUCTION The association of priority organics such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), as well as 137Cs and 21OPb, with clay, silt, and organic carbon in bottom sediments has both a theoretical and practical interest. The cycling of organics depends on the type of particle they are associated with, and models for 137Cs and 210Pb depend on particle size (Fukumori et ai., 1992). PAHs may be associated with organic carbon (Boehm and Farrington, 1984). Likewise, Evans et ai. (1990), investigating the variation of PAHs with both size fraction and organic carbon, found a correlation between PAHs and organic carbon. However, they failed to distinguish between clay and silt by considering only a single size fraction (63 /lm. For PCBs, the association with organic carbon is less certain (Simmons et ai., 1980; Swackhamer and Armstrong, 1988). 137Cs is known to be associated with clay minerals (Tamura, 1964; Comans et ai., 1991). For 210pb, there is an indication that organic complexation or adsorption to hydrous oxides is important (Shimp et ai., 1971; Leland et ai., 1973) although adsorption to clay is a possibility (Krishnaswamy et ai., 1971). The purpose of this work is to clarify the association of PAHs, PCBs, and 210Pb with silt, clay, and organic carbon in sediments of a freshwater environment.

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I. A. AB RAZAK et at.

30

METHODS AND MATERIALS Sampling The Kinnickinnic River sediments were sampled in early June 1994. In all, six locations or stations ,:ere sampled (Figure 1). For this study, the materials analyzed w~re from the. six deep cores (2 to 3 m) obtaIned by vibrating aluminium tubes with inside diameter of 6.7 cm mto th~ sedIments. Each of the cores were then sliced into 15 subintervals providing 90 sediment samples for analysIs.

1

N

t

lKm Outer Harbor

LAKE MICHIGAN

MilwRukee Solvay --------, Coke Co.

• Sampling Station Figure 1. Sampling sites.

Porosity. loss-on-ignition. and grain size Porosity was calculated based on the assumption that the solid sediment density was 2.45 g/cm 3. To determine loss on ignition (LOI), a portion of samples weighing about 0.25 g each was heated in an oven for 10 to 15 minutes at 550°C. For grain size classification, sieve analysis, and hydrometer analysis (AASHTO, 1982) for portions passing sieve No 200 (0.075 nun diameter), were performed. PAHs and PCBs The sediment sample was freeze-dried and homogenized by grinding. An aliquot of 5 g of the sample was added with surrogate standards for both PAHs (2-florobiphenyl) and PCBs (dibutylchlorendate + tetrachloro-m-xylene) and then extracted in the Soxhlet apparatus using 150 rn1 hexane:acetone (1: 1) for 24 hrs. The volume of the extract was reduced in a Kudema-Danish (K-D) concentrator to about 5 ml and solvent-exchanged to about 50 rn1 hexane. The volume was reduced again to about 5 ml. Then a gentle stream of nitrogen was used to bring down the volume of the extract to about 2 ml. The sample were charged onto a chromatographic column (11 x 300 mm) packed with HCI-rinsed copper at the bottom to absorb elemental sulfur, 10 g of 1% deactivated silica-gel, and about 10 g of anhydrous

Association of PAHs, PCSs, 137Cs and 210Pb with sediments

31

sodium sulfate on the top to absorb residual water. The column was eluted sequentially with 30 mI hexane, 45 mI 10% methylene chloride in hexane, and 40 ml of methylene chloride. All PAHs are eluted in the second and third fractions, and PCBs were found in both first and second fractions. Fractions were collected in flasks and the volumes reduced by K-D concentrator to about 4 mI, and then further reduced by nitrogen to 2 mI. PAHs were analyzed by a HP GC(5890-II)/MS(5971A) system equipped with a DB-5 column (30 m x 0.25J.1m id). PCBs were analyzed by GC/ECD with another DB-5 column (30 m x 0.32J.1m id). Peak areas obtained were corrected based on the internal standards which were added before injection. The average recoveries of the surrogate compounds are 84 (44-142)% for PCBs and 72 (30-138)% for PAHs. At least one sample in each sediment core was analyzed by duplicate subsamples to assess the analytical reproducibility. The relative standard deviation of the duplicates had average values of 10% for PCBs and 11 % for PAHs. 137CS and 210Pb The determination of 137Cs activity was accomplished by placing a plastic bag with a sediment pellet on top of a high resolution, lithium-drifted germanium, Ge(Li), detector overnight. Data from the detector were collected and analyzed using EG&G Maestro™ Adcam® Multichannel Analyzer Software. 137Cs emits gamma energy at 661 KeY, and this was quantified using the software as net area count per second. 210Pb activity, on the other hand, was determined by detecting alpha emissions from 208po and 21Opo decay. The procedures involved in chemical separation are described in detail in a separate report (Li et al., 1995) Principal component analysis Principal component analysis (PCA) was carried out on the following variables: porosity, loss-on-ignition (LOI), clay, silt, fine sand, PAHs, benzo(a)pyrene (BaP), benz(a)anthracene (BaA), Chrysene (Chy), PCBs, 137Cs, and 210Pb (SAS, 1989). The result is a series of factors accounting for more than 80% of the variance. We consider all six vibra cores which are each divided into 15 sections. Thus there are a total of 90 samples. For comparison, PCA was also carried out separately on samples from individual cores. The factor loading of a variable is the correlation of that variable with the factor. The advantage of using PCA rather than ordinary correlation analysis is that the degree of association is measured on the variations and not the absolute values of the variables. RESULTS AND DISCUSSION Table 1 shows the results of porosity, LOI, and grain size distribution for core YC94-1. Layer 6 exhibits an increase in silt (7.3% vs. 4.6 and 1.7% for layers 5 and 7) whereas the clay fraction remains zero (Table 1). From Fig. 2, it is seen that total PAHs increase considerably in layer 6 (489 ppm) compared to layers 5 (115 ppm) and 7 (44 ppm). By contrast, the increase in PCBs is rather modest: 3.15 ppm (layer 6) vs. 2.14 and 1.16 ppm for layers 5 and 7, respectively. Similarly, 210pb exihibits an increase in layer 6 (2.14 dpm/g) vs. layers 5 and 7 (1.02 and 0.91 dpm/g, respectively) while 137Cs remains near zero (0.07, 0, and 0 dpm/g for layers 5, 6, and 7). This supports the result of PCA, discussed below, that PAHs and 210pb are associated with the silt and organic carbon fraction, whereas PCBs and 137Cs are linked with clay.

32

I. A. AB RAZAK et al.

Table 1. Summary of porosity, LO!, and grain size distribution for core VC94-1 Core Section

Sediment Interval

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

0-12 12 - 24 24 - 36 36 - 48 48 - 60 60 -72 72 - 84 84 - 96 96 - 108 108 - 120 120 - 132 132 - 144 144 - 156 156 - 168 168 - 180

Coarse Fine Particles Clay Sand Silt Sand Porosity %LOI <0.002 mm 0.074 mm- 0.42 mm- 2.0mm- >2.0mm 0.002mm 0.074mm 0.42 mm % % % % % 5.2 18.84 2.7 27.5 17.8 0.559 46.8 20.9 3.3 0.495 8.78 2.0 62.9 10.9 4.7 5.26 1.3 8.7 14.6 0.576 70.8 2.31 0.0 1.7 71.9 22.4 4.0 0.379 0.338 1.64 0.0 4.6 75.1 13.0 7.3 0.533 3.17 0.0 7.3 66.9 18.5 7.3 0.335 2.06 0.0 1.7 24.8 71.9 1.7 0.275 1.76 0.0 0.7 50.4 40.2 8.7 0.260 3.14 4.7 16.0 34.4 32.9 12.0 0.543 3.95 7.3 27.3 48.8 15.4 1.1 0.556 5.45 7.3 24.6 54.6 13.4 0.0 0.530 4.76 8.0 37.4 51.0 3.6 0.0 0.566 7.50 10.0 38.9 44.2 6.8 0.0 0.523 3.35 7.3 40.2 49.8 2.4 0.3 0.546 3.69 12.0 42.4 39.1 6.5 0.1 ppm

year

1993 1991 1989 1987 1984 1982 1980 1978 1976 1974 1972 1969 1967 1965 1963

~~ __ • _

.•. :aA.1

90

~~ • • I_"---"----...._...~.---..J. • . c~ •

1999~ 600

400

20g 20

~50~

50

I'"----~_~ ____..J._....

••

.....

1---18

30

42

54

_

66

-,

LhJ ..-,

I

_

t:~kr_ 6

•

1

tPAH I

j----_tPCB_

••• • BaP

78

LhJ ••

1

90 102 114 126 138 150 162 174 depth (em)

Figure 2. Concentration of selected organic contaminants in sediment core VC94-1.

Association ofPAHs. PCSs. \37Cs and 2\Opb with sediments

33

Table 2. Factor loadings for the sediment cores YC94-1

YC94-2

POROSITY LOI CLAY SILTS FINE SAND PAHs BaP BaA CHY PCBs CS-137 PB-2\0

POROSITY LOI CLAY SILTS FINE SAND PAHs BaP BaA CHY PCBs CS-137 PB-2\0

YC94-3

YC94-4

POROSITY LOI CLAY SILTS FINE SAND PAHs BaP BaA CHY PCBs CS-137 PB-2\0

POROSITY LOI CLAY SILTS FINE SAND PAHs BaP BaA CHY PCBs CS-137 PB-210

-0.16 -0.28 -0.\3 -0.23 0.00

FACTOR 2 FACTOR 3 0.18 -0.65 0.02 -0.37

YC94-6

YC94-5 POROSITY LOI CLAY SILTS FINE SAND PAHs BaP BaA CHY PCBs CS-137 PB-2\0

POROSITY LOI CLAY SILTS FINE SAND PAHs BaP BaA CHY PCBs CS-137 PB-210

FACTOR 3 0.12 -0.06 -0.03

0.15 0.15 -0.31 -0.15

All Cores POROSITY LOI CLAY SILTS FINE SAND PAHs BaP BaA CHY PCBs CS-\37 PB-2\0

FACTOR 3 -0.09 -0.21 0.18 -0.24 0.\5 0.\\

0.11 0.05

0.13

PAHs, PCBs, 137Cs, and 210Pb vs. clay silt and organic carbon Table 2 gives the results of PCA conducted on samples from each individual core, and on all cores. In general it can be seen that there is a correlation between PAHs, silt, organics, and 210pb activity; especially

I A. AS RAZAK er a/.

for materials from all 90 samples. On the other hand, PCBs, clay, eand I.nCs tend to covary for almost every case considered. The covariance of 210Pb with silt, and of LnCs with clay, is in accor~ance wlt~l the modeling results of Fukumori et al. (1992) that I :nCs ~ppea~ed. to be associated with col,IOldal and Opb with settling particles. The third factor for all cores mdlcate SimIlar transport patterns, or sou~ces, of P~Bs and LnCs. These associations become even more pronounced if PCA is followed by Vanmax rotatIon (Table 3). It is seen that 210Pb also is linked to the clay fraction to some extent (factor 2). Table 3. Factor loadings for all cores after Varimax rotation

POROSITY LOI

CLAY SILTS FINE SAND

PAHs BaP BaA

CHY PCBs CS-137 PB-210

CONCLUSIONS Principal component analysis is an effective tool to investigate the association of priority organics and radionuclides with clay, silt, and organic carbon in aquatic sediments. PAHs may be associated not only with organic carbon but also with porosity and silt. The association of PAHs with organic carbon and silt is confirmed by measurements on one of the sediment cores (VC94-1). Both 137Cs, and PCBs are associated with clay, but not with organic carbon. The association of PCBs with clay is consistent with measurements on one of the sediment cores (YC94-1). 210Pb covaries to a similar degree with both organic carbon and clay. Because the weight fraction of silt is about four times that of clay, the main linkage of 210pb is to the organic fraction (and silt). The association of 210Pb with organic carbon, and of 137Cs with clay, is confirmed by measurements on one of the sediment cores (YC94-1). The above findings regarding 137Cs and 210Pb are consistent with a previous modeling result that 137Cs appears to be associated with colloidal, and 210pb with settling particles. ACKNOWLEDGMENT This work was supported by a contract from the U.S. Army Corps of Engineers, and by a grant from the U.S. National Science Foundation (BES-93 14725). REFERENCES American Association of State Highway and Transportation Officials Standard Specifications for Transportation Materials and Methods of Sampling and Testing. (1982). 13th Ed. Particle Size Analysis of Soils. AASHTO Designation: T 88- 8 J,

276-287.

Association ofPAHs, PCSs, 137Cs and 210Pb with sediments

35

Boehm, P. D. and Farrington, J. W. (1984). Aspects of the polycyclic aromatic hydrocarbon geochemistry of recent sediments in the Georges Bank region. Environ. Sci. Technol. 18(11),840-845. Comans, R. N. J., Haller, M. and De Preter, P. (1991). Sorption of cesium on illite: Non-equilibrium behavior and reversibility. Geochim. Cosmochim. Acta 55, 433-440. Evans, K. M., Gill, R. A. and Robotham, P. W. J. (1990). The PAH and organic content of sediment particle size fractions. Water Air Soil Pollut., 51. 13-31. Fukumori, E., Christensen, E. R. and Klein, R. J. (1992). A model for 137Cs and other tracers in lake sediments considering particle size and the inverse solution. Earth Planet. Sci. Lett., 114,85-99. Krishnaswamy, S., Lat, D., Martin, J. M. and Meybeck, M. (1971). Geochronology of lake sediments. Earth Planet. Sci. Lett., 11, 407-414. Leland, H. V., Shukla, S. S. and Shimp, N. F. (1973). Factors affecting the distribution of lead and other trace elements in sediments of southern Lake Michigan. In: Trace Metals and Metal-Organic Interactions in Natural Waters, Singer, P.C. (Ed.). Ann Arbor Science, Michigan, pp. 89-129. Li, A., Ab Razak, I. A. and Christensen, E. R. (1995). Toxic Organic Contaminants in the Sediments of the Milwaukee Harbor Estuary Phase III Kinnickinnic River Sediments. Final report to the u.S. Anny Corps of Engineers, Detroit. Dept. of Civil Engineering and Mechanics, University of Wisconsin-Milwaukee. SAS Institute Inc., (1989). SAS/STAT User's Guide, Version 6, Fourth Ed., Volume 1, Cary, NC. Shimp, N. F., Schleicher, 1. A., Ruch, R. R., Heck, D. B. and Leland, H. V. (1971). Trace Element and Organic Carbon Accumulation in the Most Recent Sediments of Southern Lake Michigan. Illinois State Geol. Surv. Environ. Geol. Notes, No. 41. Simmons, M. S., Bialosky and Rossmann, R. (1980). Polychlorinated biphenyl contamination in surficial sediments of northeastern Lake Michigan. J. Great Lakes Res., 6(2),167-171. Swackhamer, D. L. and Annstrong, D. E. (1988). Horizontal and vertical distribution of PCBs in the southern Lake Michigan sediments and the effect of Waukegan Harbor as a point source. J. Great Lakes Res., 14(3),277-290. Tamura, T. (1964). Selective sorption reactions of cesium with soil minerals. Nucl. Safety, 5(3),262-265.