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Total contents and sequential extractions of mercury, cadmium, and lead in coastal sediments
M a r i n e Pollution Bulletin 0025-326x/92 $5.00+0.00 © 1992 PergamonPress Ltd
Marine Pollution Bulletin, Volume 24, No. 7, pp. 351)-357, 1992.
Printed in Great Britain.
Total Contents and Sequential Extractions of Mercury, Cadmium, and Lead in Coastal Sediments R. GIORDANO, L. MUSMECI, L. CIARALLI, I. VERNILLO, M. CHIRICO, A. PICCIONI and S. COSTANTINI* lstituto Superiore di Sanitd, Applied Toxicology Department, Viale Regina Elena, 229, 00161 Rome, Italy *To w h o m c o r r e s p o n d e n c e should be a d d r e s s e d .
Samples of sediments collected along Italian coasts were analysed for mercury, cadmium, and lead contents by means of atomic absorption spectrometry methods. Determinations of iron and organic carbon were also performed. In addition, selective extractions were applied to the samples in order to evaluate the presence of the elements investigated in different chemical fractions. The mean values of total metals, expressed on the basis of dry weight, were 0.23+0.41 mg kg-1 for Hg, 0.16+0.12 mg kg -I for Cd, and 41.1+37.3 mg kg -1 for Pb. In general, the levels of metals found in the stations where there was not much shipping activity were quite low and typical of unpolluted coastal sediments, whereas the highest concentrations noted were in the stations placed inside harbours. The procedure of selective extractions evidenced high percentages of metals in the residual fraction. For lead and cadmium, the concentrations obtained through leaching showed the anomaly/background contrast better than the total concentrations.
Tessier et al., 1979). However, all of these have some limitations and their use as analytical tools is controversial (Kersten & Frrstner, 1990; Kheboian & Bauer, 1987). The main problems include the non-selectivity of extractants, and a possible trace element redistribution among phases during extraction. Despite this, the leaching techniques still represent one of the few tools available for examining trace metal associations in sediments. In the present study the concentrations are reported of mercury, cadmium, and lead determined in coastal sediments collected along Italian coasts. Among the various procedures of selective extraction reported in the literature, we adopted Tessier's method which has been applied and discussed widely by a number of authors (Kheboian & Bauer, 1987; Tessier et al., 1982). In addition, the determinations of total iron and organic carbon were also performed. Both flame and flameless atomic absorption spectrometry methods were employed in the metal determinations. Materials and M e t h o d s
Presently, the role of heavy metals as pollutants is widely recognized (Ballester et al., 1980; Samhan et aL, 1987; Ober et al., 1987). Some elements, notably mercury, cadmium, and lead, have at times been found in anomalously high concentrations in the marine environment, apparently in relation to naturally occuring deposits (Catsiki & Arnoux, 1987). Anthropogenic activities, however, still remain the cause of the increased amount of heavy metals which have been dumped into oceans. For this reason, the analysis of metals in sediments can be quite helpful in detecting sources of pollution in the aquatic system. Since the distribution of trace metals in various chemical fractions is important in evaluating the more readily available forms of metals that are associated with sediments, several extraction procedures with chemical solutions have been developed (Agemian & Chau, 1977; Calmano & F6rstner, 1983; Gupta & C h e n , 1975; 350
Sample collection and treatment Samples of the overlying layer of sediment (upper 5 cm) were collected by the WWF (World Wide Fund for Nature) in the summer of 1986 at a series of 36 main stations and 108 sub-stations along Italian coasts, with a total of 144 sampling sites (Fig. 1). All sediments were taken by a grap sampler and stored below -20°C in polyethylene containers until analysis. Before chemical manipulation, all visible marine organisms and shell fragments were removed. The analyses were performed on the < 6 3 ~tm fractions which were obtained by sieving through a nylon net. Dry weight determination (105°C) was made on further aliquots of samples which were not used in the investigation. Analysis of total and residual metals About 0.30 g of homogenized air-dried material were digested in a microwave system using teflon vessels under pressure (CEM, USA, model MDS-81 D). The
Volume 24/Number 7/July 1992
1
5A_ Ligurian SeaE]5
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Adriatic Sea 3~
a[Z
E
Tyrrhenlan
17[~ 18
E
)1
22
Ionian Sea
1 Genoa 2 Portoflno 3 La Spezla 4 Llvorno 5 Gorgona 6 Plomblno 7 Porto S.Stefano 8 Montecrlsto 9 Flumlclno 10 Olbla 11 Tavolara 12 Orosel 13 Cala Gonone 14 Cala Slslne 15 Terraclna 16 Ponza 17 Ischla 18 Capri 19 Naples 20 Salerno 21 Agropoll 22 Pallnuro 23 Maratea 24 Vlbo Valentla 25 Glola Tauro 26 Messlna 27 Taormlna 28 Llparl 29 Palermo 3 0 Taranto 31 S.Marla dl Leuca 3 2 Brlndlsl 3 3 Barl 3 4 Manfredonla 35 Termoll 36 Tremltl
Fig. I Sampling stations.
sample was allowed to rest overnight in a mixture of 3 ml of nitric and 2 ml of hydrochloric concentrate acids. After adding 3 ml of perchloric and 4 ml of hydrofluoric concentrate acids, digestion was carried out under microwave action. Finally, the solution was neutralized with 20 ml of boric acid (saturated solution) and the volume was taken up to 50 ml with doubly-distilled water. All reagents were of the Suprapur type (Merck, Germany). Samples were analysed three times and the measurements were made in triplicate. Determination of mercury was performed by the cold vapour AAS technique according to the Official Italian Method (G.U., 1971). Cadmium and lead determinations were made by the SPTF-AAS technique (PerkinElmer 5100 Zeeman, HGA 600 graphite furnace, AS-60 autosampler). A mixture of magnesium nitrate (Cd: 0.2 g 1-1; Pb: 2 g 1-l) and ammonium dihydrogen phosphate (Cd: 2 g 1-1; Pb: 20 g1-1) was used as a matrix modifier. The standard addition method was employed as a calibration procedure. The iron analysis was performed by the flame AAS technique. Determination of total organic carbon (TOC) was made by a method described in a previous paper (Castagnoli et al., 1987). Sequential extractions According to the method proposed by Tessier et al., 1979, five metal fractions were obtained: /. exchangeable; 2. bound to carbonates; 3. bound to iron and manganese oxides; 4. bound to organic matter and sulphides; 5. residual The determinations of the metals in leaching solutions (LS) were performed by the same techniques employed for total metal analysis. Neverthe-
less, owing to the complexity of the extractant solutions (e.g. MgC12 1M, NaOAc 1M, NH2OH.HC1 0.04M in HOAc 25% v/v, H202 pH2), some changes were necessary. The determination of mercury in LS4 required the use of sodium borohydride instead of the mixture of stannous chloride and hydroxilamine hydrochloride. A 32 g 1-1 ammonium phosphate solution prepared in 6% v/v nitric acid was used as a matrix modifier for the determination of cadmium and lead in LS1. In this case, a minimum dilution ratio of 1:4 was compulsory; the temperatures in the ashing and atomization stages were: Cd 600 and 1700°C, Pb 1000 and 2000°C, respectively. LS2 required the use of two diluents: a mixture of 20 g 1-~ ammonium phosphate and 2 g 1-I magnesium nitrate prepared in 1% v/v nitric acid was used for Pb (ashing 1100°C, atomizing 2100°C); for Cd (ashing 500°C, atomizing 1500°C) instead, a mixture of 3.6 g 1-T of ammonium phosphate and 2.5 g 1-j of magnesium nitrate prepared in 0.2% v/v nitric acid was employed. The dilution ratio was 1:10 or higher. In LS3 and LS4 a mixture of 20 g 1-l ammonium phosphate and 2 g 1-~ magnesium nitrate was used for both cadmium (ashing 8000C, atomizing 1800°C) and lead (ashing 800°C, atomizing 2000°C). The mean dilution ratio in these solutions was 1:5 for lead and 1:2 for Cd. Data quality tests Reference materials from both BCR (Soil, 142) and NCS (BCSS-1, marine sediment), certified for mercury, cadmium, and lead, were used to check accuracy and precision in the analysis of total metals. The values of recovery were: 97.2% for Hg; 103% for Cd, and 98.1% 351
Marine Pollution Bulletin
for Pb. The coefficients of variation were: 9% for Hg; 5% for Cd, and 7% for Pb. The detection limits, with respect to the entire procedures, were: 0.03 mg kg -~ for Hg, 0.03 mg kg -1 for Cd, and 4.2 mg kg -~ for Pb, respectively. As far as the partitioning of trace metals is concerned, the lack of standard reference materials containing known trace element phase distributions made it impossible to determine the accuracy and, consequently, the selectivity of the extraction procedures. This aspect probably represents one of the critical problems of the method. On the other hand, there is not clear evidence that synthetic models are able to effectively reproduce the structure and the reactivity of real sediments. The detection limits (mg kg -~ dry wt) were: Fractions 1 and 2: Hg 0.008, Cd 0.004, Pb 0.040; Fractions 3 and 4: Hg 0.020, Cd 0.010, Pb 0.060; Fraction 5: Hg 0.03, Cd 0.03, Pb 4.2.
Statistical analysis In addition to an initial data manipulation programme, the statistical analysis involved several procedures, such as the analysis of variance, the multiple regression method, the U-Mann-Witney test, the analysis of principal components and the cluster analysis. Since data did not show a normal distribution, they were transformed into natural logarithms so that parametric methods could be applied; however, the nonparametric tests were performed on the original data.
Results and D i s c u s s i o n The concentration values of all the parameters investigated showed wide dispersion, probably as a consequence of both the large sampling area and different degree of pollution in the localities examined. Table 1 summarizes the results of the total metal and TOC concentrations. Table 2 shows the results of the sequential extractions. All data are expressed on the basis of the dry weight as a mean +SD (main station+sub-stations). In Table 3 the matrix correlation for all the variables is reported. Fig. 2 shows the distribution patterns of the elements along the stations. The mean values of TOC (g%) and total metals (mg kg-1 dry wt) were: TOC 0.80+0.42; Hg 0.23+0.41; Cd 0.16+0.12; Pb 41.1+37.3. The highest values were generally found in areas characterized by higher anthropogenic activities, such as principle harbours (see Table 1), with mean concentrations statistically different from those obtained in areas which were probably unpolluted. The highest differences were noted for mercury (0.61+0.64 vs 0.07+0.05, p<0.001) and lead (84+48 vs 28+17, p<0.001); lower differences were instead found for TOC (1.19+0.51 vs 0.69+0.32, p<0.01) and Cd (0.21+0.14 vs 0.13+0.11, p<0.05). The mean level of the mercury concentration in samples collected inside harbours presents the same order of magnitude of data reported for an Italian coastal area affected by a chlor-
TABLE 1 Total mercury, cadmium, lead, iron, and organic carbon concentrations (dry wt).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Station
Hg mgkg-~
Cd mgkg-
Pb mgkg-1
Fe gkg-~
TOC g%
Genova* Portofino La Spezia* Livorno* Gorgona Piombino* S. Stefano* Montecristo Fiumicino Olbia Tavolara Orosei Cala Gonone Cala Sisine Terracina Ponza Ischia Capri Napoli* Salerno* Agropoli Palinuro Maratea V. Valentia Gioia Tauro Messina Taormina Lipari Palermo Taranto* S.M. Leuca Brindisi* Bar±* Manfredonia Termoli Tremiti
0.77±0.32 0.21±0.06 2.03±0.78 0.05±0.02 0.06±0.01 0.34±0.12 1.47±0.29 0.04±0.01 0.19±0.07 0.09±0.03 0.05±0.01 0.04±0.01
0.54±0.23 0.07±0.03 0.38±0.23 0.14±0.01 0.13±0.01 0.16±0.06 0.15±0.10 0.08±0.02 0.24+0.13 0.15+0.05 0.10+0.02 0.07±0.01
155±94 34+11 172+68 86± 12 33±5 47±29 31 ± 14 27+12 32± 14 64± 18 16±9 15±6 16±6 9±3 26±5 24+7 24_+6 16±5 115±54 65± 14 20_+8 23±7 15±8 48+ 16 23±9 30± 14 9±4 32±14 39±12 41 + 13 9±4 59+16 68+ 16 22+ 10 19±7 16±7
23.0±2.7 22.9+3.2 30.4+6.8 10.3±3.1 28.2+5.6 28.5±8.6 23.3± 3.0 4.9±1.1 52.2±29 10.2±2.1 2.4±0.7 12.9±3.5 8.8+2.7 7.5±2.4 18.5±3.9 4.3± 1.2 42.8±5.6 9.6_+1.3 44.7± 12 19.2±5.5 12.6±4.7 39.7±11 5.2±1.9 14.4± 1.7 29.9±9.4 26.8±6.4 20.2±4.0 40.4±6.5 6.0+1.6 14.3+ 3.6 3.4±1.2 9.3+2.6 21.3+5.1 19.6±5.9 23.6±5.8 4.9+1.5
1.37+0.32 0.37+0.10 1.90+0.79 0.48±0.11 0.57±0.08 1.09±0.48 1.42± 1.09 0.70±0.21 0.43±0.10 0.91 ±0.09 1.05±0.38 0.19±0.06 0.72±0.25 0.41±0.02 0.72±0.35 0.76±0.11 0.40±0.11 0.95±0.16 0.75±0.25 0.81 ±0.63 0.49+0.30 1.10±0.47 1.24_+0.35 0.69±0.19 (I.50+0.28 0.39± 0.44 0.25+0.12 1.37±0.19 0.24±0.09 1.34_+0.70 0.60±0.21 0.90±0.65 1.80± 1.55 1.10+0.45 1.07±0.83 0.59±0.36
352
Detection limits: mg kg -1 dry wt. Hg=0.03; Cd=0.03; Pb=4.2.
Volume 24/Number 7/July 1992
TABLE 2 Mercury, cadmium, and lead concentrations in chemical fractions (mg kg-j) Station 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Genova* Portofino La Spezia* Livorno* Gorgona Piombino* S. Stefano* Montecristo Fiumicino Olbia Tavolara Orosei Cala Gonone Cala Sisine Terracina Ponza Ischia Capri Napoli* Salerno* Agropoli Palinuro Maratea V. Valentia Gioia Tauro Messina Taormina Lipari Palermo Taranto* S.M. Leuca Brindisi* Bari* Manfredonia Termoli Tremiti Station
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Genova* Portofino La Spezia* Livorno* Gorgona Piombino* S. Stefano* Montecristo Fiumicino Olbia Tavolara Orosei Cala Gonone Cala Sisine Terracina Ponza Ischia Capri Napoli* Salerno* Agropoli Palinuro Maratea V. Valentia Gioia Tauro Messina Taormina Lipari Palermo Taranto* S.M. Leuca Brindisi* Bari* Manfredonia Termoli Tremiti
Cd 1
Pb 1
0.077:1:0.029 0.006±0.003 0.073±0.044 0.025±0.005 0.0075:0.002 0.016±0.006 0.008±0.006 0.009±0.002 0.008±0.003 0.008±0.002
0.170±0.106
Iqg4
Cd~
0.0435:0.017
Cd 2 0.140±0.053
Pb 2
Cd 3
Pb 3
40.3±23.1 15.4±4.2 51.5±22.5 46.2±8.9 8.6±1.5 10.8±5.1 6.4±2.7 6.25:2.5 5.3±2.3 16.8±4.9 2.1±0.9 2.1±0.8 2.35:0.9 1.9±0.6 3.7±0.7 6.4±1.9 1.55:0.4 4.35:1.3 15.5±7.1 7.2± 1.6 3.2+1.3 3.2±0.9 4.0±1.9 1.95:0.7 1.35:0.5 4.55:2.1 2.25:0.09 2.3±1.0 8.6±2.7 6.45:2.0 2.5± 1.3 16.95:4.9 9.1±2.1 3.9±1.8 3.7±1.4 4.5± 1.9
0.180±0.083 0.019±0.009 0.100±0.770 0.038+0.010 0.0925:0.007 0.047±0.021 0.033:t:0.019 0.017±0.004
52.3±33.4 12.4±3.7 86.75:39.8 28.4±4.8 22.8±3.0 15.5±6.9 15.8±7.1 4.75:2.1 6.8±3.1 13.7±3.9 8.2±0.5 2.1±1.1 1.85:0.7 3.5± 1.2 4.5± 1.3 10.5±3.1 2.25:0.6 6.15:1.9 7.8+3.2 20.2±4.4 4.85:1.9 0.15:0.3 6.65:3.6 5.85:1.9 3.3+ 1.3 4.8± 1.8 4.65:2.5 5.15:2.1 10.45:3.0 20.45:6.7 4.25:1.9 23.3±6.5 18.1±3.9 7.35:3.4 5.9±2.1 4.1± 1.6
Hg s 0.76±0.41 0.145:0.04 1.915:0.75 0.04±0.02 0.045:0.02 0,245:0.09 1.4l+0.30 -
Cd 5 0.11±0.06 0.045:0.02 0.065:0.04 0.055:0.02 0.045:0.01 0.075:0.03 0.085:0.05 0.065:0.02 0.19±0.07 0.065:0.02 0.04±0.01
Pb 5 55.95:34.7 6.7±2.3 29.1 ± 13.1 10.75:1.9
Marine Pollution Bulletin TABLE 3
Correlation Matrix. HgT HgT CdT Pbv TOC Cd I Pb I Cd 2 Pb 2 Cd 3 Pb3 Hg4 Cd 4
Pb4 Fe I Hg5 Cd 5 Pb 5
CdT
1 0.469 1 0.683 0.624 0.546 0.419 0.606 0.535 0.434 0.326 0.476 0.687 0.643 0.532 0.380 0.665 0.519 0.503 0.720 0.198 0.475 0.455 0.469 0.125 0.425 -0.06 0.973 0.475 0 . 2 5 1 0.803 0.435 0.156
PbT
TOC
Cd a
Pb]
Cd 2
1 0.404 0.732 0.651 0.357 0.822 0.310 0.602 0.549 0.632 0.650 0.398 0.629 0.210 0.750
1 0.465 0.215 0.429 0.318 0.377 0.285 0.371 0.370 0.244 0.083 0.529 0.195 0.276
1 0.589 0.443 0.671 0.378 0.407 0.504 0.514 0.489 0.266 0.556 0.228 0.513
1 0.314 0.730 0.369 0.481 0.300 0.471 0.396 0.143 0.413 0.136 0.299
0.419 0.594 0.460 0.179 0.383 0.170 0.068 0.504 0.381 0.234
Pb2
Cd 3
Pb3
Hg4
Cd4
Pb4
Fev
Hg5
Cd 5
Pb5
1
1 0.547 1 0.687 0.554 0.517 0.208 0.580 0.528 0.401 -0.04 0.116 0.207 0.501 0.37 0.239 0.199 0.366 -0.14
1 0.409 0.564 0.123 -0.04 0.475 0.173 0.138
1
0.215 1 0.423 0.511 0.417 -0.04 0.591 0.475 0.015 0.132 0.284 0.386
1 0.348 1 0.460 0.392 0.118 -0.05 0.689 0.457
1 0.266 1 0.421 0.204
0.325 0.519: p<0.001.
21t;2 1.9 ,.s ~
•
~^
+
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l.s
ul 0 1.12.314. 1"5 Ill/ oL) o 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 00 ,=
~
~
Hg mg/kg Cd mg/kg
l/
Pb mg/kg x 10-2
Orgc' arbg' %
~ / ~'~
U
10
20
30
i
40
Sampling stations Fig. 2 Distribution patterns of total mercury, cadmium, lead, and organic carbon along the Italian coasts.
alkaly c o m p l e x ( F e r r a r a et aL, 1989); the d a t a also agree with t h o s e f o u n d in s o m e A m e r i c a n h a r b o u r s ( B r a d f o r d & L u o m a , 1980). T h e m a x i m u m level o f H g (2.03 m g kg -1) was f o u n d in L a Spezia, p r o b a b l y r e l a t e d to p o l l u t i o n f r o m local a n t h r o p o g e n i c sources. T h e value f o u n d in the a r e a o f N a p l e s (0.45_+0.21) falls within the r a n g e o f c o n c e n t r a t i o n o b t a i n e d in a p r e v i o u s investigation c a r r i e d o u t in the s a m e a r e a ( C a m o n i et al., 1980). M o r e o v e r , the m e a n m e r c u r y levels c a l c u l a t e d for the g r o u p o f localities less i n v o l v e d in a n t h r o p o g e n i c activities fall within the interval ( 0 . 0 4 - 0 . 1 5 m g kg -1) r e p o r t e d f o r u n p o l l u t e d a r e a s in E n g l a n d ( H a l c r o w et al., 1973; Phillips, 1977). C a d m i u m c o n t a m i n a t i o n a p p e a r s to b e quite low. B o t h the g e n e r a l m e a n level of c o n c e n t r a t i o n a n d t h e o n e c a l c u l a t e d for s a m p l e s f r o m h a r b o u r s a r e within the ranges r e p o r t e d for s o m e M e d i t e r r a n e a n a r e a s (Ballester et al., 1980; C h e s t e r & V o u t s i n o u , 1981)). T h e m e a n values of l e a d f o u n d in m o s t o f the a r e a s e x a m i n e d a g r e e with t h o s e r e p o r t e d for coastal s e d i m e n t s ( S a m h a n et al., 1987); the highest 354
c o n c e n t r a t i o n s o b s e r v e d in m o r e p o l l u t e d localities have the s a m e o r d e r o f m a g n i t u d e as t h o s e r e p o r t e d for s o m e h a r b o u r s (Catsiki & A r n o u x , 1987; F o w l e r 1990). In o r d e r to e v a l u a t e w h e t h e r the s a m p l i n g was r e p r e s e n t a t i v e in t e r m s o f local variations, Hg, Cd, a n d P b c o n c e n t r a t i o n s in s e d i m e n t s were c o r r e l a t e d with t h o s e f o u n d in m u s s e l s ( G i o r d a n o et al., 1991) c o l l e c t e d in the s a m e cruise in the stations w h e r e the o r g a n i s m s were f o u n d ( n = 2 0 ) . In fact, b e s i d e s s e a s o n a l changes, v a r i o u s factors (e.g. f r a c t i o n a t i o n , turnover, r e s u s p e n sion, etc.) affect the local d i s t r i b u t i o n of m e t a l s in the u p p e r s e d i m e n t l a y e r at the s a m p l i n g p o i n t ( K r u m g a l z et al., 1989). In a d d i t i o n , the analytical p r o c e d u r e s can also influence data; however, it was d e m o n s t r a t e d that this latter f a c t o r is of lesser interest ( C h o r k , 1977). T h e following linear c o r r e l a t i o n s were o b t a i n e d : H g T muss. vs Hgx sed.: r = 0 . 7 8 1 , p < 0 . 0 0 1 ; P b T muss. vs P b T sed.: r = 0 . 6 1 4 , p < 0 . 0 1 . Since m u s s e l s are r e c o g n i z e d as a v a l u a b l e i n d i c a t o r o f t r a c e m e t a l p o l l u t i o n o f the s u r r o u n d i n g waters, these c o r r e l a t i o n s w o u l d i n d i c a t e
Volume 24/Number 7/July 1992
that the levels found in sediments are representative of the degree of contamination in these localities during the under study season. The lack of correlation observed for Cd may be due to the low levels of the element found. Throughout the areas in question, and in spite of the local characteristics, other correlations were observed among the concentrations of the metals examined: Hgv vs CdT:r=0.469, p<0.01; Hg T vs PbT:r=0.683, p < 0.001; Cdv vs Pbv:r=0.624, p < 0.001; These correlations probably indicate that the metals came from similar sources and that their geographic distribution patterns are also similar. Iron showed correlations only with mercury and lead: Fev vs Hgv, r=0.425, p<0.01; Fe T vs Pbv r----().398, p<0.05. Further correlations were also observed among the concentrations of metals and the ones of TOC: Hgv vs TOC, r=0.546, p<0.001 ; Cd v vs TOC, r=0.419, p<0.01; Pb T vs TOC, r=0.404, p<0.05. These latter are probably representative of inputs of anthropogenic origin. However, TOC seems to exert a stronger control on the concentration of total mercury than the other metals. As far as the partitioning of trace metals is concerned, in the fraction (FR) 1, metal concentrations were generally low, and sometimes close to or below the detection limits; a few spikes of concentrations were found in the harbour areas. In FR1, as well as in FR2 and FR3, all mercury levels were below the detection limits calculated for the element. For Cd, the mean concentration of all sites was quite low (0.015+0.017 mg kg-1) but it accounted for 9% of the total amount; thus, it seems that processes occuring in FR1 take on a significant role in the biogeochemical distribution of cadmium in the environment (Forstner, 1980). The mean Pbl concentration (0.063+0.068 mg kg-l) was only 0.15% of the total content. In general, these results may mean that cadmium is a metal which is more easily displaceable from sediment than lead. This agrees with previous observations reported for oxic sediments (Kersten & Forstner, 1986). The lead concentration increased considerably from FR1 to FR3, with a mean level of 9.3+12.1 mg kg-l in FR2 and 12.6+16.2 mg kg-~ in FR3. In FR2, sixteen stations (44.4%) had a cadmium concentration (Cd2) which was lower than the detection limit of 0.004 mg kg-1, whereas only eight stations (22.2%) had a value higher than the mean value (0.025+0.036 mg kg-J). This resulted in an evident and wide dispersion of results, with values particulary high in some sites. Similar considerations can be made for lead (Pb2), even though all values for this element were higher than the detection limit of 0.04 mg kg-~. FR3 represents the metal bound to Fe-Mn oxides which are excellent scavengers for trace metals. Cadmium (Cd3) and lead (Pb3) levels in this fraction accounted for a large proportion (23.7% and 30.7%, respectively) of the total concentrations. The levels of Cd 3 and Pb3 followed a similar pattern and the highest values of the elements were noted once again in harbours. The latter finding was to be expected, owing to a probable thermodynamic instability of the oxides in such sediments. In FR4, the concentration of mercury (Hg4), cadmium (Cd4) and lead (Pb4) were 0.035+0.028 mg kg-~, 0.014+0.007 mg kg-~, and 1.5+2.3 mg kg-1,
respectively. These values accounted for 15.2%, 8.8%, and 3.6% of their respective total amounts. 63.8% of both the levels of Hg 4 and Cd 4 were below their detection limits (0.020 and 0.010 mg kg-l), whereas this occurred with Pb 4 in only three of the stations. A few spikes of Hg 4 were noted in stations having a high TOC content; however, high concentrations of TOC not always correspond to high Hg 4 levels; thus, only a poor correlation between TOC and Hg 4 (p<0.05) was observed. The TOC also weakly correlated with Gd~ (p<0.05), whereas there was no correlation with Pb 4. These results were probably due either to a dissolution of the sulphide phase (Tessier et al., 1979) or to problems of metal redistribution within the phases (Kheboian & Bauer, 1987). FR5 consists of metals bound within the crystalline lattices of mineral particles and it is essentially unvailable in the sedimentary environment. Without exception, the concentrations of the elements in this phase were higher than those observed in each of the former fractions; in fact, the residual metals accounted for 86.9% (Hgs), 46.3% (Cds) and 43.5% (Pbs) of their total contents, respectively. The use of the ETA--AAS technique in the determination of cadmium and lead in leaching solutions allowed considerable improvement to be made in the detection limits usually reported in the literature for this kind of investigation by authors who had used the flame AAS technique (Tessier et al., 1979; 1982). In fact, the complexity of extractant solutions coupled with high ratios of extraction sometimes made it impossible to determine particularly low levels of concentrations (e.g. fractions 1 and 2) by the flame method. In some situations, where its utilization should have been possible, this resulted in being inadequate owing to the poor accuracy caused by the high saline content of the solutions. In relation to mercury determination, the AAS cold vapour technique made it possible to obtain very low detection limits; nevertheless, in FR1, FR2 and FR3 detectable amounts of the element were not found. Moreover, in FR4 quite low concentrations were measured. Our data do not permit establishing whether Hg was effectively present in high percentages in the residual fraction or if this is an artifact caused by the poor capability of the method for this element. We favour the last hypothesis since the leaching did not detect displaceable amounts of Hg even in harbour stations where high levels of Hgv were noted. On the contrary, for Cd and Pb the concentrations obtained through leaching showed the anomaly/background contrast better than the total concentrations. In fact, the 'p coefficient' calculated for Cd v between the group of harbours and the remaining stations was <0.05, while it was consistently better in Cd 1 (p<0.00i); in Cd2, Cd 3 and C d 4 it resulted in being <0.01 and it was not significant in Cd 5. Thus, data suggest that the surplus of the element from anthropogenic activities occurs in less stable chemical forms involved in short- and middleterm geochemical processes. The last considerations can be valid also for lead which showed in FR1, FR2 and FR3 differences which were particularly significant (p<0.001; p~0.0001; p~0.0001, respectively). How355
Marine Pollution Bulletin
ever, for this element the exogenous inputs involved also the residual fraction, where the difference (p<0.01) between the two groups of stations was found still appreciable; this may be due to the high levels of PbT found in harbours (84+48 mg kg -~) which resulted in being statistically very different (p<0.001) from those measured in the other localities (28+17 mg kg-1). Cluster and principal component analyses were applied in order to obtain a more complete interpretation of the results. The analysis of principal components made it possible to combine all variables into a shorter number representing the whole information. Fig. 3 shows that the first four components account for over 75% of data variance. In particular, the first component accounts for 53% and the second for 14.6%. Both on the basis of these observations and the communality found among the variables, it is possible to say that some variables, namely Hga~ Cda~ Pb~ TOC, Pb3, Hgs, Cd 5, and Pb 5 are the most representative of the phenomenon (Fig. 4). The cluster analysis did not identify clearly
outlined groups; this can be explained by the low number of stations with respect to the wide sampling area which was characterized by different geochemical and environmental situations. Nevertheless, as shown in the dendrogram reported in Fig. 5, it was possible to single out six probable clusters (CL) which included twenty-five stations. Values of concentrations particularly low for Hg, Cd, and Pb linked stations 27 (Taormina) and 31 (S. Maria di Leuca) in a little cluster (CLs): these levels were always below those reported for sediments from the open ocean. In station 27, a very low TOC content coupled with a higher iron concentration probably increased the distance from station 31. A large cluster (CL4)of eight stations presented levels of Hg, Cd and TOC similar to the ones found in CLs; the levels of lead were higher than in CL5 but were still comparable to those of unpolluted sediments. CLe had a mercury level which was similar to those from C L 4 and CLs, intermediate lead levels as well as increased levels of 4
45.3
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356
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Fig. 3 Eigen values.
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22
Volume 24/Number 7/July 1992
cadmium; in this group of stations the concentrations of iron were particularly low. CL 1 differed from CL 2 and CL 4 mainly for the mercury values. Hot-spots of TOC occurred in some stations of CL 1 (Manfredonia and Termoli) and CL 2 (Maratea and Capri) probably due to improper waste disposal not related to industrial inputs. Six stations placed inside harbours formed two separate clusters (CL 2 and CL3) but the remaining four stations were unclustered. This finding could be explained by the different degrees of pollution determined by different harbour activities, and agrees with the wide standard deviations of the means calculated among the stations placed in the harbours. Group CL 3 was characterized by levels of Cd which were still acceptable, whereas those of Hg, Pb, and TOC were comparable to a situation of average pollution. CL 6 formed by the most polluted stations (Genoa and La Spezia) resulted in being very distant from the other groups. The large distance between the two stations was probably determined by the large difference both in Hg T and Hg 4 concentrations. In conclusion, our study pointed out that the concentration levels of metals found in the stations not involved in much shipping activity were generally low and typical of an unpolluted coastal environment. The authors wish to thank the Department of Merchant Navy, Rome, Italy, for financial support of this study, and Mrs Susan M. Holt for reviewing the English version of this paper. Agemian, H. & Chau, A. S. Y. (1977). A study of different analytical extraction methods for nondetrital heavy metals in aquatic sediments. Arch. Environ. ToxicoL 6, 69-82. Ballester, A., Miller, J. & Dunyach, M. (1980). Some pollutants present in marine sediments, animals and plants in the coastal waters of Catalonia, Spain. Thalassia JugosL 16,275-287. Bradford, W. L. & Luoma, S. N. (1980). Some perspectives on heavy metal concentrations in shell-fish and sediment in S. Francisco Bay. In Contaminants and Sediments (R. A. Baker, ed.), pp. 501-532. Ann Arbor Science, Michigan, USA. Calmano, W. & F6rsmer, U. (1983). Chemical extraction of heavy metals in polluted river sediments in Central Europe. Sci. Tot. Environ, 28, 77-90. Camoni, 1., Cotta-Ramusino, F., Funari, E., Giordano, R., Ovidi, P., Dohrn, P. & Ballio, A. (1980). Heavy metals and organochlorine residues in marine animals and coastal sediments of the Thyrrenian sea around Naples. Annali 1st. Sup. Sanitd 16, 645-656. Castagnoli, O., Musmeci, L., Chirico, M., & Maialetti, E (1987). Confronto di metodi di determinazione del carbonio organico in R.S.U. lnquinamento 78, 58-59.
Catsiki, A. V. & Arnoux, A. (1987). Etud~ de la variabilit6 des teneurs en Hg, Cu, Zn et Pb de trois espbces de mollusques de l'Etange de Berre (France). Mar. Environ. Res. 21, 175-187. Chester, R. & Voutsinou, E G. (1981). The initial assessment of trace metal pollution in coastal sediments. Mar. Poll. Bull. 12, 84-91. Chork, C. Y. (1977). Seasonal sampling and analytical variations in stream sediment surveys. J. Geochem. Explor. 7, 31-47. Ferrara, R., Maserti, B. E. & Paternb, P. (1989). Mercury distribution in maritime sediment and its correlation with the Posidonia Oceanica prairie in a coastal area affected by a chlor-alkali complex. ToxicoL Environ. Chem. 22, 131-134. F6rstner, U. (1980). Cadmium in polluted sediments. In Cadmium in the environment, Vol. I (J. O. Niriagu, ed.), pp. 305-363, J. Wiley & Sons, New York. Fowler, S. W. (1990). Critical review of selected heavy metal and chlorinated hydrocarbon concentrations in the marine environment. Mar. Environ. Res. 29, 1-64. Gazzetta Ufficiale Repubblica Italiana (1971). Limite di contaminazione da mercurio del pesce e degli altri prodotti alimentari della pesca di provenienza estera. D.M. 14 dicembre 1971, G.U.n.328. Giordano, R., Arata, P., Ciaralli, L., Rinaldi, S., Giani, M., Cicero, A. M., & Costantini, S. (1991). Mar. Pollut. Bull. 22, 10-14. Gupta, S. K. & C h e n , K. Y. (1975). Partitioning of trace metals in selective chemical fractions of nearshore sediments. Environ. Lett. 10(2), 129-158. Halcrow, W., MacKay, D. W. & Thornton, I. (1973). The distribution of trace metals and fauna in the Firth of Clyde in relation to the disposal of sewage sludge. J. Mar. BioL Ass. UK, 53, 721 739. Kersten, M. & F6rstner, U. (1986). Chemical fractionation of heavy metals in anoxic estuarine and coastal sediments. Wat. Sci. Tech. 19, 121-130. Kersten, M. & F6rstner, U. (1990). Speciation of trace elements in sediments. In Trace Element Speciation: Analytical Methods and Problems. (G. E. Batley, ed.), pp. 245-317. CRC Press, Inc., Boca Raton, USA. Kheboian, C. & Bauer, C. F. (1987). Accuracy of selective extraction procedures for metal speciation in model aquatic sediments. A n a l Chem. 59, 1417-1423. Krumgalz, .B S., Fa/nshtein, G., Sahler, M. & Garfunkel, L. (1989). 'Field error' related to marine sediment contamination studies. Mar. Pollut. Bull. 20, 64-69. Ober, A. G., Gonzales, M. & Santa Maria, 1. (1987). Heavy metals in molluscan, crustacean and other commercially important chilean marine coastal water species. Bull. Environ. Contam. ToxicoL 38, 534-539. Phillips, D. J. H. (1977). The use of biological indicator organisms to monitor trace metal pollution in marine and estuarine environments. A review. Environ. Poll. 13,281-317. Samhan, O., Zarba, M. & Anderlini, V. (1987). Multivariate geochemical investigation on trace metal pollution in Kuwait marine sediments. Mar. Environ. Res. 21, 21-48. Tessier, A., Campbell, P. G. C. & Bisson, M. (1979). Sequential extraction procedure for the speciation of particulate metals. A n a l Chem. 51,844-851. Tessier, A., Campbell, P. G. C. & Bisson, M. (1982). Particulate trace metal speciation in stream sediments and relationships with grain size: implication for geochemical exploration. J. Geochem. Explor. 16, 77-104.
357
Marine Pollution Bulletin, Volume 24, No. 7, pp. 351)-357, 1992.
Printed in Great Britain.
Total Contents and Sequential Extractions of Mercury, Cadmium, and Lead in Coastal Sediments R. GIORDANO, L. MUSMECI, L. CIARALLI, I. VERNILLO, M. CHIRICO, A. PICCIONI and S. COSTANTINI* lstituto Superiore di Sanitd, Applied Toxicology Department, Viale Regina Elena, 229, 00161 Rome, Italy *To w h o m c o r r e s p o n d e n c e should be a d d r e s s e d .
Samples of sediments collected along Italian coasts were analysed for mercury, cadmium, and lead contents by means of atomic absorption spectrometry methods. Determinations of iron and organic carbon were also performed. In addition, selective extractions were applied to the samples in order to evaluate the presence of the elements investigated in different chemical fractions. The mean values of total metals, expressed on the basis of dry weight, were 0.23+0.41 mg kg-1 for Hg, 0.16+0.12 mg kg -I for Cd, and 41.1+37.3 mg kg -1 for Pb. In general, the levels of metals found in the stations where there was not much shipping activity were quite low and typical of unpolluted coastal sediments, whereas the highest concentrations noted were in the stations placed inside harbours. The procedure of selective extractions evidenced high percentages of metals in the residual fraction. For lead and cadmium, the concentrations obtained through leaching showed the anomaly/background contrast better than the total concentrations.
Tessier et al., 1979). However, all of these have some limitations and their use as analytical tools is controversial (Kersten & Frrstner, 1990; Kheboian & Bauer, 1987). The main problems include the non-selectivity of extractants, and a possible trace element redistribution among phases during extraction. Despite this, the leaching techniques still represent one of the few tools available for examining trace metal associations in sediments. In the present study the concentrations are reported of mercury, cadmium, and lead determined in coastal sediments collected along Italian coasts. Among the various procedures of selective extraction reported in the literature, we adopted Tessier's method which has been applied and discussed widely by a number of authors (Kheboian & Bauer, 1987; Tessier et al., 1982). In addition, the determinations of total iron and organic carbon were also performed. Both flame and flameless atomic absorption spectrometry methods were employed in the metal determinations. Materials and M e t h o d s
Presently, the role of heavy metals as pollutants is widely recognized (Ballester et al., 1980; Samhan et aL, 1987; Ober et al., 1987). Some elements, notably mercury, cadmium, and lead, have at times been found in anomalously high concentrations in the marine environment, apparently in relation to naturally occuring deposits (Catsiki & Arnoux, 1987). Anthropogenic activities, however, still remain the cause of the increased amount of heavy metals which have been dumped into oceans. For this reason, the analysis of metals in sediments can be quite helpful in detecting sources of pollution in the aquatic system. Since the distribution of trace metals in various chemical fractions is important in evaluating the more readily available forms of metals that are associated with sediments, several extraction procedures with chemical solutions have been developed (Agemian & Chau, 1977; Calmano & F6rstner, 1983; Gupta & C h e n , 1975; 350
Sample collection and treatment Samples of the overlying layer of sediment (upper 5 cm) were collected by the WWF (World Wide Fund for Nature) in the summer of 1986 at a series of 36 main stations and 108 sub-stations along Italian coasts, with a total of 144 sampling sites (Fig. 1). All sediments were taken by a grap sampler and stored below -20°C in polyethylene containers until analysis. Before chemical manipulation, all visible marine organisms and shell fragments were removed. The analyses were performed on the < 6 3 ~tm fractions which were obtained by sieving through a nylon net. Dry weight determination (105°C) was made on further aliquots of samples which were not used in the investigation. Analysis of total and residual metals About 0.30 g of homogenized air-dried material were digested in a microwave system using teflon vessels under pressure (CEM, USA, model MDS-81 D). The
Volume 24/Number 7/July 1992
1
5A_ Ligurian SeaE]5
[]~.
Adriatic Sea 3~
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E
Tyrrhenlan
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1 Genoa 2 Portoflno 3 La Spezla 4 Llvorno 5 Gorgona 6 Plomblno 7 Porto S.Stefano 8 Montecrlsto 9 Flumlclno 10 Olbla 11 Tavolara 12 Orosel 13 Cala Gonone 14 Cala Slslne 15 Terraclna 16 Ponza 17 Ischla 18 Capri 19 Naples 20 Salerno 21 Agropoll 22 Pallnuro 23 Maratea 24 Vlbo Valentla 25 Glola Tauro 26 Messlna 27 Taormlna 28 Llparl 29 Palermo 3 0 Taranto 31 S.Marla dl Leuca 3 2 Brlndlsl 3 3 Barl 3 4 Manfredonla 35 Termoll 36 Tremltl
Fig. I Sampling stations.
sample was allowed to rest overnight in a mixture of 3 ml of nitric and 2 ml of hydrochloric concentrate acids. After adding 3 ml of perchloric and 4 ml of hydrofluoric concentrate acids, digestion was carried out under microwave action. Finally, the solution was neutralized with 20 ml of boric acid (saturated solution) and the volume was taken up to 50 ml with doubly-distilled water. All reagents were of the Suprapur type (Merck, Germany). Samples were analysed three times and the measurements were made in triplicate. Determination of mercury was performed by the cold vapour AAS technique according to the Official Italian Method (G.U., 1971). Cadmium and lead determinations were made by the SPTF-AAS technique (PerkinElmer 5100 Zeeman, HGA 600 graphite furnace, AS-60 autosampler). A mixture of magnesium nitrate (Cd: 0.2 g 1-1; Pb: 2 g 1-l) and ammonium dihydrogen phosphate (Cd: 2 g 1-1; Pb: 20 g1-1) was used as a matrix modifier. The standard addition method was employed as a calibration procedure. The iron analysis was performed by the flame AAS technique. Determination of total organic carbon (TOC) was made by a method described in a previous paper (Castagnoli et al., 1987). Sequential extractions According to the method proposed by Tessier et al., 1979, five metal fractions were obtained: /. exchangeable; 2. bound to carbonates; 3. bound to iron and manganese oxides; 4. bound to organic matter and sulphides; 5. residual The determinations of the metals in leaching solutions (LS) were performed by the same techniques employed for total metal analysis. Neverthe-
less, owing to the complexity of the extractant solutions (e.g. MgC12 1M, NaOAc 1M, NH2OH.HC1 0.04M in HOAc 25% v/v, H202 pH2), some changes were necessary. The determination of mercury in LS4 required the use of sodium borohydride instead of the mixture of stannous chloride and hydroxilamine hydrochloride. A 32 g 1-1 ammonium phosphate solution prepared in 6% v/v nitric acid was used as a matrix modifier for the determination of cadmium and lead in LS1. In this case, a minimum dilution ratio of 1:4 was compulsory; the temperatures in the ashing and atomization stages were: Cd 600 and 1700°C, Pb 1000 and 2000°C, respectively. LS2 required the use of two diluents: a mixture of 20 g 1-~ ammonium phosphate and 2 g 1-I magnesium nitrate prepared in 1% v/v nitric acid was used for Pb (ashing 1100°C, atomizing 2100°C); for Cd (ashing 500°C, atomizing 1500°C) instead, a mixture of 3.6 g 1-T of ammonium phosphate and 2.5 g 1-j of magnesium nitrate prepared in 0.2% v/v nitric acid was employed. The dilution ratio was 1:10 or higher. In LS3 and LS4 a mixture of 20 g 1-l ammonium phosphate and 2 g 1-~ magnesium nitrate was used for both cadmium (ashing 8000C, atomizing 1800°C) and lead (ashing 800°C, atomizing 2000°C). The mean dilution ratio in these solutions was 1:5 for lead and 1:2 for Cd. Data quality tests Reference materials from both BCR (Soil, 142) and NCS (BCSS-1, marine sediment), certified for mercury, cadmium, and lead, were used to check accuracy and precision in the analysis of total metals. The values of recovery were: 97.2% for Hg; 103% for Cd, and 98.1% 351
Marine Pollution Bulletin
for Pb. The coefficients of variation were: 9% for Hg; 5% for Cd, and 7% for Pb. The detection limits, with respect to the entire procedures, were: 0.03 mg kg -~ for Hg, 0.03 mg kg -1 for Cd, and 4.2 mg kg -~ for Pb, respectively. As far as the partitioning of trace metals is concerned, the lack of standard reference materials containing known trace element phase distributions made it impossible to determine the accuracy and, consequently, the selectivity of the extraction procedures. This aspect probably represents one of the critical problems of the method. On the other hand, there is not clear evidence that synthetic models are able to effectively reproduce the structure and the reactivity of real sediments. The detection limits (mg kg -~ dry wt) were: Fractions 1 and 2: Hg 0.008, Cd 0.004, Pb 0.040; Fractions 3 and 4: Hg 0.020, Cd 0.010, Pb 0.060; Fraction 5: Hg 0.03, Cd 0.03, Pb 4.2.
Statistical analysis In addition to an initial data manipulation programme, the statistical analysis involved several procedures, such as the analysis of variance, the multiple regression method, the U-Mann-Witney test, the analysis of principal components and the cluster analysis. Since data did not show a normal distribution, they were transformed into natural logarithms so that parametric methods could be applied; however, the nonparametric tests were performed on the original data.
Results and D i s c u s s i o n The concentration values of all the parameters investigated showed wide dispersion, probably as a consequence of both the large sampling area and different degree of pollution in the localities examined. Table 1 summarizes the results of the total metal and TOC concentrations. Table 2 shows the results of the sequential extractions. All data are expressed on the basis of the dry weight as a mean +SD (main station+sub-stations). In Table 3 the matrix correlation for all the variables is reported. Fig. 2 shows the distribution patterns of the elements along the stations. The mean values of TOC (g%) and total metals (mg kg-1 dry wt) were: TOC 0.80+0.42; Hg 0.23+0.41; Cd 0.16+0.12; Pb 41.1+37.3. The highest values were generally found in areas characterized by higher anthropogenic activities, such as principle harbours (see Table 1), with mean concentrations statistically different from those obtained in areas which were probably unpolluted. The highest differences were noted for mercury (0.61+0.64 vs 0.07+0.05, p<0.001) and lead (84+48 vs 28+17, p<0.001); lower differences were instead found for TOC (1.19+0.51 vs 0.69+0.32, p<0.01) and Cd (0.21+0.14 vs 0.13+0.11, p<0.05). The mean level of the mercury concentration in samples collected inside harbours presents the same order of magnitude of data reported for an Italian coastal area affected by a chlor-
TABLE 1 Total mercury, cadmium, lead, iron, and organic carbon concentrations (dry wt).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Station
Hg mgkg-~
Cd mgkg-
Pb mgkg-1
Fe gkg-~
TOC g%
Genova* Portofino La Spezia* Livorno* Gorgona Piombino* S. Stefano* Montecristo Fiumicino Olbia Tavolara Orosei Cala Gonone Cala Sisine Terracina Ponza Ischia Capri Napoli* Salerno* Agropoli Palinuro Maratea V. Valentia Gioia Tauro Messina Taormina Lipari Palermo Taranto* S.M. Leuca Brindisi* Bar±* Manfredonia Termoli Tremiti
0.77±0.32 0.21±0.06 2.03±0.78 0.05±0.02 0.06±0.01 0.34±0.12 1.47±0.29 0.04±0.01 0.19±0.07 0.09±0.03 0.05±0.01 0.04±0.01
0.54±0.23 0.07±0.03 0.38±0.23 0.14±0.01 0.13±0.01 0.16±0.06 0.15±0.10 0.08±0.02 0.24+0.13 0.15+0.05 0.10+0.02 0.07±0.01
155±94 34+11 172+68 86± 12 33±5 47±29 31 ± 14 27+12 32± 14 64± 18 16±9 15±6 16±6 9±3 26±5 24+7 24_+6 16±5 115±54 65± 14 20_+8 23±7 15±8 48+ 16 23±9 30± 14 9±4 32±14 39±12 41 + 13 9±4 59+16 68+ 16 22+ 10 19±7 16±7
23.0±2.7 22.9+3.2 30.4+6.8 10.3±3.1 28.2+5.6 28.5±8.6 23.3± 3.0 4.9±1.1 52.2±29 10.2±2.1 2.4±0.7 12.9±3.5 8.8+2.7 7.5±2.4 18.5±3.9 4.3± 1.2 42.8±5.6 9.6_+1.3 44.7± 12 19.2±5.5 12.6±4.7 39.7±11 5.2±1.9 14.4± 1.7 29.9±9.4 26.8±6.4 20.2±4.0 40.4±6.5 6.0+1.6 14.3+ 3.6 3.4±1.2 9.3+2.6 21.3+5.1 19.6±5.9 23.6±5.8 4.9+1.5
1.37+0.32 0.37+0.10 1.90+0.79 0.48±0.11 0.57±0.08 1.09±0.48 1.42± 1.09 0.70±0.21 0.43±0.10 0.91 ±0.09 1.05±0.38 0.19±0.06 0.72±0.25 0.41±0.02 0.72±0.35 0.76±0.11 0.40±0.11 0.95±0.16 0.75±0.25 0.81 ±0.63 0.49+0.30 1.10±0.47 1.24_+0.35 0.69±0.19 (I.50+0.28 0.39± 0.44 0.25+0.12 1.37±0.19 0.24±0.09 1.34_+0.70 0.60±0.21 0.90±0.65 1.80± 1.55 1.10+0.45 1.07±0.83 0.59±0.36
352
Detection limits: mg kg -1 dry wt. Hg=0.03; Cd=0.03; Pb=4.2.
Volume 24/Number 7/July 1992
TABLE 2 Mercury, cadmium, and lead concentrations in chemical fractions (mg kg-j) Station 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Genova* Portofino La Spezia* Livorno* Gorgona Piombino* S. Stefano* Montecristo Fiumicino Olbia Tavolara Orosei Cala Gonone Cala Sisine Terracina Ponza Ischia Capri Napoli* Salerno* Agropoli Palinuro Maratea V. Valentia Gioia Tauro Messina Taormina Lipari Palermo Taranto* S.M. Leuca Brindisi* Bari* Manfredonia Termoli Tremiti Station
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Genova* Portofino La Spezia* Livorno* Gorgona Piombino* S. Stefano* Montecristo Fiumicino Olbia Tavolara Orosei Cala Gonone Cala Sisine Terracina Ponza Ischia Capri Napoli* Salerno* Agropoli Palinuro Maratea V. Valentia Gioia Tauro Messina Taormina Lipari Palermo Taranto* S.M. Leuca Brindisi* Bari* Manfredonia Termoli Tremiti
Cd 1
Pb 1
0.077:1:0.029 0.006±0.003 0.073±0.044 0.025±0.005 0.0075:0.002 0.016±0.006 0.008±0.006 0.009±0.002 0.008±0.003 0.008±0.002
0.170±0.106
Iqg4
Cd~
0.0435:0.017
Cd 2 0.140±0.053
Pb 2
Cd 3
Pb 3
40.3±23.1 15.4±4.2 51.5±22.5 46.2±8.9 8.6±1.5 10.8±5.1 6.4±2.7 6.25:2.5 5.3±2.3 16.8±4.9 2.1±0.9 2.1±0.8 2.35:0.9 1.9±0.6 3.7±0.7 6.4±1.9 1.55:0.4 4.35:1.3 15.5±7.1 7.2± 1.6 3.2+1.3 3.2±0.9 4.0±1.9 1.95:0.7 1.35:0.5 4.55:2.1 2.25:0.09 2.3±1.0 8.6±2.7 6.45:2.0 2.5± 1.3 16.95:4.9 9.1±2.1 3.9±1.8 3.7±1.4 4.5± 1.9
0.180±0.083 0.019±0.009 0.100±0.770 0.038+0.010 0.0925:0.007 0.047±0.021 0.033:t:0.019 0.017±0.004
52.3±33.4 12.4±3.7 86.75:39.8 28.4±4.8 22.8±3.0 15.5±6.9 15.8±7.1 4.75:2.1 6.8±3.1 13.7±3.9 8.2±0.5 2.1±1.1 1.85:0.7 3.5± 1.2 4.5± 1.3 10.5±3.1 2.25:0.6 6.15:1.9 7.8+3.2 20.2±4.4 4.85:1.9 0.15:0.3 6.65:3.6 5.85:1.9 3.3+ 1.3 4.8± 1.8 4.65:2.5 5.15:2.1 10.45:3.0 20.45:6.7 4.25:1.9 23.3±6.5 18.1±3.9 7.35:3.4 5.9±2.1 4.1± 1.6
Hg s 0.76±0.41 0.145:0.04 1.915:0.75 0.04±0.02 0.045:0.02 0,245:0.09 1.4l+0.30 -
Cd 5 0.11±0.06 0.045:0.02 0.065:0.04 0.055:0.02 0.045:0.01 0.075:0.03 0.085:0.05 0.065:0.02 0.19±0.07 0.065:0.02 0.04±0.01
Pb 5 55.95:34.7 6.7±2.3 29.1 ± 13.1 10.75:1.9
Marine Pollution Bulletin TABLE 3
Correlation Matrix. HgT HgT CdT Pbv TOC Cd I Pb I Cd 2 Pb 2 Cd 3 Pb3 Hg4 Cd 4
Pb4 Fe I Hg5 Cd 5 Pb 5
CdT
1 0.469 1 0.683 0.624 0.546 0.419 0.606 0.535 0.434 0.326 0.476 0.687 0.643 0.532 0.380 0.665 0.519 0.503 0.720 0.198 0.475 0.455 0.469 0.125 0.425 -0.06 0.973 0.475 0 . 2 5 1 0.803 0.435 0.156
PbT
TOC
Cd a
Pb]
Cd 2
1 0.404 0.732 0.651 0.357 0.822 0.310 0.602 0.549 0.632 0.650 0.398 0.629 0.210 0.750
1 0.465 0.215 0.429 0.318 0.377 0.285 0.371 0.370 0.244 0.083 0.529 0.195 0.276
1 0.589 0.443 0.671 0.378 0.407 0.504 0.514 0.489 0.266 0.556 0.228 0.513
1 0.314 0.730 0.369 0.481 0.300 0.471 0.396 0.143 0.413 0.136 0.299
0.419 0.594 0.460 0.179 0.383 0.170 0.068 0.504 0.381 0.234
Pb2
Cd 3
Pb3
Hg4
Cd4
Pb4
Fev
Hg5
Cd 5
Pb5
1
1 0.547 1 0.687 0.554 0.517 0.208 0.580 0.528 0.401 -0.04 0.116 0.207 0.501 0.37 0.239 0.199 0.366 -0.14
1 0.409 0.564 0.123 -0.04 0.475 0.173 0.138
1
0.215 1 0.423 0.511 0.417 -0.04 0.591 0.475 0.015 0.132 0.284 0.386
1 0.348 1 0.460 0.392 0.118 -0.05 0.689 0.457
1 0.266 1 0.421 0.204
0.325
21t;2 1.9 ,.s ~
•
~^
+
"t Ill
°
l.s
ul 0 1.12.314. 1"5 Ill/ oL) o 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 00 ,=
~
~
Hg mg/kg Cd mg/kg
l/
Pb mg/kg x 10-2
Orgc' arbg' %
~ / ~'~
U
10
20
30
i
40
Sampling stations Fig. 2 Distribution patterns of total mercury, cadmium, lead, and organic carbon along the Italian coasts.
alkaly c o m p l e x ( F e r r a r a et aL, 1989); the d a t a also agree with t h o s e f o u n d in s o m e A m e r i c a n h a r b o u r s ( B r a d f o r d & L u o m a , 1980). T h e m a x i m u m level o f H g (2.03 m g kg -1) was f o u n d in L a Spezia, p r o b a b l y r e l a t e d to p o l l u t i o n f r o m local a n t h r o p o g e n i c sources. T h e value f o u n d in the a r e a o f N a p l e s (0.45_+0.21) falls within the r a n g e o f c o n c e n t r a t i o n o b t a i n e d in a p r e v i o u s investigation c a r r i e d o u t in the s a m e a r e a ( C a m o n i et al., 1980). M o r e o v e r , the m e a n m e r c u r y levels c a l c u l a t e d for the g r o u p o f localities less i n v o l v e d in a n t h r o p o g e n i c activities fall within the interval ( 0 . 0 4 - 0 . 1 5 m g kg -1) r e p o r t e d f o r u n p o l l u t e d a r e a s in E n g l a n d ( H a l c r o w et al., 1973; Phillips, 1977). C a d m i u m c o n t a m i n a t i o n a p p e a r s to b e quite low. B o t h the g e n e r a l m e a n level of c o n c e n t r a t i o n a n d t h e o n e c a l c u l a t e d for s a m p l e s f r o m h a r b o u r s a r e within the ranges r e p o r t e d for s o m e M e d i t e r r a n e a n a r e a s (Ballester et al., 1980; C h e s t e r & V o u t s i n o u , 1981)). T h e m e a n values of l e a d f o u n d in m o s t o f the a r e a s e x a m i n e d a g r e e with t h o s e r e p o r t e d for coastal s e d i m e n t s ( S a m h a n et al., 1987); the highest 354
c o n c e n t r a t i o n s o b s e r v e d in m o r e p o l l u t e d localities have the s a m e o r d e r o f m a g n i t u d e as t h o s e r e p o r t e d for s o m e h a r b o u r s (Catsiki & A r n o u x , 1987; F o w l e r 1990). In o r d e r to e v a l u a t e w h e t h e r the s a m p l i n g was r e p r e s e n t a t i v e in t e r m s o f local variations, Hg, Cd, a n d P b c o n c e n t r a t i o n s in s e d i m e n t s were c o r r e l a t e d with t h o s e f o u n d in m u s s e l s ( G i o r d a n o et al., 1991) c o l l e c t e d in the s a m e cruise in the stations w h e r e the o r g a n i s m s were f o u n d ( n = 2 0 ) . In fact, b e s i d e s s e a s o n a l changes, v a r i o u s factors (e.g. f r a c t i o n a t i o n , turnover, r e s u s p e n sion, etc.) affect the local d i s t r i b u t i o n of m e t a l s in the u p p e r s e d i m e n t l a y e r at the s a m p l i n g p o i n t ( K r u m g a l z et al., 1989). In a d d i t i o n , the analytical p r o c e d u r e s can also influence data; however, it was d e m o n s t r a t e d that this latter f a c t o r is of lesser interest ( C h o r k , 1977). T h e following linear c o r r e l a t i o n s were o b t a i n e d : H g T muss. vs Hgx sed.: r = 0 . 7 8 1 , p < 0 . 0 0 1 ; P b T muss. vs P b T sed.: r = 0 . 6 1 4 , p < 0 . 0 1 . Since m u s s e l s are r e c o g n i z e d as a v a l u a b l e i n d i c a t o r o f t r a c e m e t a l p o l l u t i o n o f the s u r r o u n d i n g waters, these c o r r e l a t i o n s w o u l d i n d i c a t e
Volume 24/Number 7/July 1992
that the levels found in sediments are representative of the degree of contamination in these localities during the under study season. The lack of correlation observed for Cd may be due to the low levels of the element found. Throughout the areas in question, and in spite of the local characteristics, other correlations were observed among the concentrations of the metals examined: Hgv vs CdT:r=0.469, p<0.01; Hg T vs PbT:r=0.683, p < 0.001; Cdv vs Pbv:r=0.624, p < 0.001; These correlations probably indicate that the metals came from similar sources and that their geographic distribution patterns are also similar. Iron showed correlations only with mercury and lead: Fev vs Hgv, r=0.425, p<0.01; Fe T vs Pbv r----().398, p<0.05. Further correlations were also observed among the concentrations of metals and the ones of TOC: Hgv vs TOC, r=0.546, p<0.001 ; Cd v vs TOC, r=0.419, p<0.01; Pb T vs TOC, r=0.404, p<0.05. These latter are probably representative of inputs of anthropogenic origin. However, TOC seems to exert a stronger control on the concentration of total mercury than the other metals. As far as the partitioning of trace metals is concerned, in the fraction (FR) 1, metal concentrations were generally low, and sometimes close to or below the detection limits; a few spikes of concentrations were found in the harbour areas. In FR1, as well as in FR2 and FR3, all mercury levels were below the detection limits calculated for the element. For Cd, the mean concentration of all sites was quite low (0.015+0.017 mg kg-1) but it accounted for 9% of the total amount; thus, it seems that processes occuring in FR1 take on a significant role in the biogeochemical distribution of cadmium in the environment (Forstner, 1980). The mean Pbl concentration (0.063+0.068 mg kg-l) was only 0.15% of the total content. In general, these results may mean that cadmium is a metal which is more easily displaceable from sediment than lead. This agrees with previous observations reported for oxic sediments (Kersten & Forstner, 1986). The lead concentration increased considerably from FR1 to FR3, with a mean level of 9.3+12.1 mg kg-l in FR2 and 12.6+16.2 mg kg-~ in FR3. In FR2, sixteen stations (44.4%) had a cadmium concentration (Cd2) which was lower than the detection limit of 0.004 mg kg-1, whereas only eight stations (22.2%) had a value higher than the mean value (0.025+0.036 mg kg-J). This resulted in an evident and wide dispersion of results, with values particulary high in some sites. Similar considerations can be made for lead (Pb2), even though all values for this element were higher than the detection limit of 0.04 mg kg-~. FR3 represents the metal bound to Fe-Mn oxides which are excellent scavengers for trace metals. Cadmium (Cd3) and lead (Pb3) levels in this fraction accounted for a large proportion (23.7% and 30.7%, respectively) of the total concentrations. The levels of Cd 3 and Pb3 followed a similar pattern and the highest values of the elements were noted once again in harbours. The latter finding was to be expected, owing to a probable thermodynamic instability of the oxides in such sediments. In FR4, the concentration of mercury (Hg4), cadmium (Cd4) and lead (Pb4) were 0.035+0.028 mg kg-~, 0.014+0.007 mg kg-~, and 1.5+2.3 mg kg-1,
respectively. These values accounted for 15.2%, 8.8%, and 3.6% of their respective total amounts. 63.8% of both the levels of Hg 4 and Cd 4 were below their detection limits (0.020 and 0.010 mg kg-l), whereas this occurred with Pb 4 in only three of the stations. A few spikes of Hg 4 were noted in stations having a high TOC content; however, high concentrations of TOC not always correspond to high Hg 4 levels; thus, only a poor correlation between TOC and Hg 4 (p<0.05) was observed. The TOC also weakly correlated with Gd~ (p<0.05), whereas there was no correlation with Pb 4. These results were probably due either to a dissolution of the sulphide phase (Tessier et al., 1979) or to problems of metal redistribution within the phases (Kheboian & Bauer, 1987). FR5 consists of metals bound within the crystalline lattices of mineral particles and it is essentially unvailable in the sedimentary environment. Without exception, the concentrations of the elements in this phase were higher than those observed in each of the former fractions; in fact, the residual metals accounted for 86.9% (Hgs), 46.3% (Cds) and 43.5% (Pbs) of their total contents, respectively. The use of the ETA--AAS technique in the determination of cadmium and lead in leaching solutions allowed considerable improvement to be made in the detection limits usually reported in the literature for this kind of investigation by authors who had used the flame AAS technique (Tessier et al., 1979; 1982). In fact, the complexity of extractant solutions coupled with high ratios of extraction sometimes made it impossible to determine particularly low levels of concentrations (e.g. fractions 1 and 2) by the flame method. In some situations, where its utilization should have been possible, this resulted in being inadequate owing to the poor accuracy caused by the high saline content of the solutions. In relation to mercury determination, the AAS cold vapour technique made it possible to obtain very low detection limits; nevertheless, in FR1, FR2 and FR3 detectable amounts of the element were not found. Moreover, in FR4 quite low concentrations were measured. Our data do not permit establishing whether Hg was effectively present in high percentages in the residual fraction or if this is an artifact caused by the poor capability of the method for this element. We favour the last hypothesis since the leaching did not detect displaceable amounts of Hg even in harbour stations where high levels of Hgv were noted. On the contrary, for Cd and Pb the concentrations obtained through leaching showed the anomaly/background contrast better than the total concentrations. In fact, the 'p coefficient' calculated for Cd v between the group of harbours and the remaining stations was <0.05, while it was consistently better in Cd 1 (p<0.00i); in Cd2, Cd 3 and C d 4 it resulted in being <0.01 and it was not significant in Cd 5. Thus, data suggest that the surplus of the element from anthropogenic activities occurs in less stable chemical forms involved in short- and middleterm geochemical processes. The last considerations can be valid also for lead which showed in FR1, FR2 and FR3 differences which were particularly significant (p<0.001; p~0.0001; p~0.0001, respectively). How355
Marine Pollution Bulletin
ever, for this element the exogenous inputs involved also the residual fraction, where the difference (p<0.01) between the two groups of stations was found still appreciable; this may be due to the high levels of PbT found in harbours (84+48 mg kg -~) which resulted in being statistically very different (p<0.001) from those measured in the other localities (28+17 mg kg-1). Cluster and principal component analyses were applied in order to obtain a more complete interpretation of the results. The analysis of principal components made it possible to combine all variables into a shorter number representing the whole information. Fig. 3 shows that the first four components account for over 75% of data variance. In particular, the first component accounts for 53% and the second for 14.6%. Both on the basis of these observations and the communality found among the variables, it is possible to say that some variables, namely Hga~ Cda~ Pb~ TOC, Pb3, Hgs, Cd 5, and Pb 5 are the most representative of the phenomenon (Fig. 4). The cluster analysis did not identify clearly
outlined groups; this can be explained by the low number of stations with respect to the wide sampling area which was characterized by different geochemical and environmental situations. Nevertheless, as shown in the dendrogram reported in Fig. 5, it was possible to single out six probable clusters (CL) which included twenty-five stations. Values of concentrations particularly low for Hg, Cd, and Pb linked stations 27 (Taormina) and 31 (S. Maria di Leuca) in a little cluster (CLs): these levels were always below those reported for sediments from the open ocean. In station 27, a very low TOC content coupled with a higher iron concentration probably increased the distance from station 31. A large cluster (CL4)of eight stations presented levels of Hg, Cd and TOC similar to the ones found in CLs; the levels of lead were higher than in CL5 but were still comparable to those of unpolluted sediments. CLe had a mercury level which was similar to those from C L 4 and CLs, intermediate lead levels as well as increased levels of 4
45.3
7.7
3
0.5
0.6
tO
2
0.6 1.9 1.4
l*.u
' "~
EIGEN VALUES
• []
Component I Comp
....
t 5
PERCENT
[] Component 2 []
7.4
8.2
Comp
[] Comp .... t 3
tB
....
[]
Comp ....
l 7
[]
Comp ....
34 I 15 ~ 9 1 36 I IB I 32 1 20 1 17 1 12 1 25 i 2z, 1 33 1 27 111 I 19 I z, I 16 35 2 23 14 6 30 29 2G 21 13 8 7 31 10 5 28 t--__l l__J 1__1 L I ~
I
[] Comp .... t.
CLI
I
t8
CL2
1.000-
0.500 -
0.500-
0.000
0.000
-0.500
-0.500-
-1.000
-1.000
I
1.000
,
1.000
O <
CL5
Third Component
........... A . .
I
I
I
i
I
I
I
I
i
I
I
I
I
i
I
I
0.500
Fourth Component 0.500 -I ..............................................• .........................
0.000
00001% A
-0.500
-1.000
I
i
I
I
i
I
I
I
I
I
I
I
I
I
I
I O n
PARAMETERS
Fig. 4 Analysis of principal components.
356
CL6
Fig. 5 Cluster analysis (single linkage).
1.000
w
CL4 STATIONS
Fig. 3 Eigen values.
O
CL3
PARAMETERS
3i _j
22
Volume 24/Number 7/July 1992
cadmium; in this group of stations the concentrations of iron were particularly low. CL 1 differed from CL 2 and CL 4 mainly for the mercury values. Hot-spots of TOC occurred in some stations of CL 1 (Manfredonia and Termoli) and CL 2 (Maratea and Capri) probably due to improper waste disposal not related to industrial inputs. Six stations placed inside harbours formed two separate clusters (CL 2 and CL3) but the remaining four stations were unclustered. This finding could be explained by the different degrees of pollution determined by different harbour activities, and agrees with the wide standard deviations of the means calculated among the stations placed in the harbours. Group CL 3 was characterized by levels of Cd which were still acceptable, whereas those of Hg, Pb, and TOC were comparable to a situation of average pollution. CL 6 formed by the most polluted stations (Genoa and La Spezia) resulted in being very distant from the other groups. The large distance between the two stations was probably determined by the large difference both in Hg T and Hg 4 concentrations. In conclusion, our study pointed out that the concentration levels of metals found in the stations not involved in much shipping activity were generally low and typical of an unpolluted coastal environment. The authors wish to thank the Department of Merchant Navy, Rome, Italy, for financial support of this study, and Mrs Susan M. Holt for reviewing the English version of this paper. Agemian, H. & Chau, A. S. Y. (1977). A study of different analytical extraction methods for nondetrital heavy metals in aquatic sediments. Arch. Environ. ToxicoL 6, 69-82. Ballester, A., Miller, J. & Dunyach, M. (1980). Some pollutants present in marine sediments, animals and plants in the coastal waters of Catalonia, Spain. Thalassia JugosL 16,275-287. Bradford, W. L. & Luoma, S. N. (1980). Some perspectives on heavy metal concentrations in shell-fish and sediment in S. Francisco Bay. In Contaminants and Sediments (R. A. Baker, ed.), pp. 501-532. Ann Arbor Science, Michigan, USA. Calmano, W. & F6rsmer, U. (1983). Chemical extraction of heavy metals in polluted river sediments in Central Europe. Sci. Tot. Environ, 28, 77-90. Camoni, 1., Cotta-Ramusino, F., Funari, E., Giordano, R., Ovidi, P., Dohrn, P. & Ballio, A. (1980). Heavy metals and organochlorine residues in marine animals and coastal sediments of the Thyrrenian sea around Naples. Annali 1st. Sup. Sanitd 16, 645-656. Castagnoli, O., Musmeci, L., Chirico, M., & Maialetti, E (1987). Confronto di metodi di determinazione del carbonio organico in R.S.U. lnquinamento 78, 58-59.
Catsiki, A. V. & Arnoux, A. (1987). Etud~ de la variabilit6 des teneurs en Hg, Cu, Zn et Pb de trois espbces de mollusques de l'Etange de Berre (France). Mar. Environ. Res. 21, 175-187. Chester, R. & Voutsinou, E G. (1981). The initial assessment of trace metal pollution in coastal sediments. Mar. Poll. Bull. 12, 84-91. Chork, C. Y. (1977). Seasonal sampling and analytical variations in stream sediment surveys. J. Geochem. Explor. 7, 31-47. Ferrara, R., Maserti, B. E. & Paternb, P. (1989). Mercury distribution in maritime sediment and its correlation with the Posidonia Oceanica prairie in a coastal area affected by a chlor-alkali complex. ToxicoL Environ. Chem. 22, 131-134. F6rstner, U. (1980). Cadmium in polluted sediments. In Cadmium in the environment, Vol. I (J. O. Niriagu, ed.), pp. 305-363, J. Wiley & Sons, New York. Fowler, S. W. (1990). Critical review of selected heavy metal and chlorinated hydrocarbon concentrations in the marine environment. Mar. Environ. Res. 29, 1-64. Gazzetta Ufficiale Repubblica Italiana (1971). Limite di contaminazione da mercurio del pesce e degli altri prodotti alimentari della pesca di provenienza estera. D.M. 14 dicembre 1971, G.U.n.328. Giordano, R., Arata, P., Ciaralli, L., Rinaldi, S., Giani, M., Cicero, A. M., & Costantini, S. (1991). Mar. Pollut. Bull. 22, 10-14. Gupta, S. K. & C h e n , K. Y. (1975). Partitioning of trace metals in selective chemical fractions of nearshore sediments. Environ. Lett. 10(2), 129-158. Halcrow, W., MacKay, D. W. & Thornton, I. (1973). The distribution of trace metals and fauna in the Firth of Clyde in relation to the disposal of sewage sludge. J. Mar. BioL Ass. UK, 53, 721 739. Kersten, M. & F6rstner, U. (1986). Chemical fractionation of heavy metals in anoxic estuarine and coastal sediments. Wat. Sci. Tech. 19, 121-130. Kersten, M. & F6rstner, U. (1990). Speciation of trace elements in sediments. In Trace Element Speciation: Analytical Methods and Problems. (G. E. Batley, ed.), pp. 245-317. CRC Press, Inc., Boca Raton, USA. Kheboian, C. & Bauer, C. F. (1987). Accuracy of selective extraction procedures for metal speciation in model aquatic sediments. A n a l Chem. 59, 1417-1423. Krumgalz, .B S., Fa/nshtein, G., Sahler, M. & Garfunkel, L. (1989). 'Field error' related to marine sediment contamination studies. Mar. Pollut. Bull. 20, 64-69. Ober, A. G., Gonzales, M. & Santa Maria, 1. (1987). Heavy metals in molluscan, crustacean and other commercially important chilean marine coastal water species. Bull. Environ. Contam. ToxicoL 38, 534-539. Phillips, D. J. H. (1977). The use of biological indicator organisms to monitor trace metal pollution in marine and estuarine environments. A review. Environ. Poll. 13,281-317. Samhan, O., Zarba, M. & Anderlini, V. (1987). Multivariate geochemical investigation on trace metal pollution in Kuwait marine sediments. Mar. Environ. Res. 21, 21-48. Tessier, A., Campbell, P. G. C. & Bisson, M. (1979). Sequential extraction procedure for the speciation of particulate metals. A n a l Chem. 51,844-851. Tessier, A., Campbell, P. G. C. & Bisson, M. (1982). Particulate trace metal speciation in stream sediments and relationships with grain size: implication for geochemical exploration. J. Geochem. Explor. 16, 77-104.
357