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Study of the Contents andSpeciation of Heavy Metalsin River sediments By FactorAnalysisR. Pardo a , E. Barrado a , Y. Castrillejo a , M. A.Velasco a & M. Vega aa Departamento de Química Analítica, Facultadde Ciencias , Prado de la Magdalena, E-47005,Valladolid, SpainPublished online: 23 Sep 2006.

To cite this article: R. Pardo , E. Barrado , Y. Castrillejo , M. A. Velasco& M. Vega (1993) Study of the Contents and Speciation of Heavy Metals inRiver sediments By Factor Analysis, Analytical Letters, 26:8, 1719-1739, DOI:10.1080/00032719308021492

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ANALYTICAL LETIERS, 26(8), 1719-1739 (1993)

S T U D Y O F THE CONTENTS AND SPECIATION O F HEAVY METALS

I N R I V E R SEDIMENTS BY FACTOR ANALYSIS

KEY WORDS: Heavy meta ls , river sediments , voltammetry, s p e c i a t i o n , f a c t o r a n a l y s i s

R . Pardo, E . Barrado, Y . C a s t r i l l e j o , M.A. Velasco and M . Vega

Departamento de Quimica A n a l i t i c a , Facultad de Cienc ias , Prado de l a Magdalena, E-47005 Val ladol id ,

Spain

ABSTRACT

Heavy meta ls Zn, Cd, Pb, Cur N i and Co from two

Spanish r i v e r sediments have been determined by

voltammetric techniques, a long w i t h 8 CaC03 and 9 organic

matter, and t h e whole d a t a set examined by means of Factor

A n a l y s i s , f i n d i n g a d i f f e r e n t behaviour of t h e metals i n

each r i v e r .

Heavy metal s p e c i a t i o n i n t h e sediments was c a r r i e d

out by using t h e Tessier 's scheme: Zn and Pb were mainly

a s s o c i a t e d t o ' r e d u c i b l e p h a s e s ' , C d and Cu bound t o

'o rganic matter and s u l p h i d e s ' , and N i and Co w e r e

d i s t r i b u t e d between t h e above f r a c t i o n s . The ' r e s i d u a l '

1719

Copyright 0 1993 by Marcel Dckkcr, lnc

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1720 PARD0 ET AL.

metals were used a s p o l l u t i o n i n d i c a t o r s from t h e r i v e r s ,

f i n d i n g a s imi la r behaviour t o o t h e r i n d u s t r i a l i z e d r i v e r

systems.

INTRODUCTION

The determinat ion of heavy metals i n environmental

1-3 samples deserves g r e a t i n t e r e s t from seve ra l s tandpoints

a ) t h e i r t o x i c i t y , b ) t h e i r p e r s i s t e n c e and c ) t h e c l o s e

r e l a t i o n between t h e chemical form i n which t h e s e elements

appear ( t h e i r s p e c i a t i o n ) and t h e i r e c o l o g i c a l impact . I n t h e r i v e r systems, t h e presence of sediments a t t h e

b o t t o m o f t h e w a t e r c o l u m n i n t r o d u c e s a n a d d i t i o n a l f a c t o r ,

because they can a c t as c o l l e c t o r s f i x i n g t h e heavy metals.

If t h i s f avourab le r o l e can be r eve r sed by an

a l t e r a t i o n of t h e normal c o n d i t i o n s of t h e water column ,

t h a t releases t h e m e t a l s t o t h e more dangereous d i s so lved

s ta te .

4

5

The main accumulation mechanisms of heavy metals i n

sediments have been summarized by Gibbs ', and imply t h e

e x i s t e n c e of f i v e main s p e c i a t i o n c a t e g o r i e s : (a)

adsorbed and exchangeable, ( b ) bound t o carbonate phases,

(c) bound t o r educ ib le phases ( such as i r o n and manganese

o x i d e s ) , ( d ) bound t o o r g a n i c matter and s u l p h i d e s and ( e )

d e t r i t a l o r l a t t i c e ( res idua l ) metals. These f r a c t i o n s have

7

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HEAVY METALS IN RIVER SEDIMENTS 1721

a d i f f e r e n t behaviour as t o remobi l iza t ion 5, so i t

becomes necessary t o know t h e t o t a l amount of heavy metal

p r e s e n t i n t h e sediment a s w e l l as i ts s p e c i a t i o n , t o

c o r r e c t l y evaluate its ecotoxicological r i s k . A t h e o r e t i c a l

approach ' must be r e j e c t e d due t o t h e l a c k of complete

thermodynamic da ta . The experimental s p e c i a t i o n is based

upon a s e q u e n t i a l e x t r a c t i o n , i n which t h e sediment is

success ive ly e x t r a c t e d with a series of chemical reagents

of i n c r e a s i n g r e a c t i v i t y g iv ing e x t r a c t s corresponding t o

t h e above c a t e g o r i e s , i n which t h e heavy metals a r e then

determined. Themostwidely used scheme is t h e one proposed

by T e s s i e r e t a l . 9 , t h a t can a l s o provide an assessment

of t h e p o l l u t i o n l e v e l of t h e sediments, by t a k i n g t h e

I ' r e s i d u a l ' f r a c t i o n as a guide . I n t h i s paper, w e have s t u d i e d sediment samples taken

from t h e r i v e r s Pisuerga and Carribn, t r i b u t a r i e s of t h e

Duero River , i n f l u e n c e d b y t h e d ischarges of twomoderately

populated and i n d u s t r i a l i z e d towns (Val ladol id and Palencia

r e s p e c t i v e l y ) . The heavy metals determined w e r e : z inc ,

cadmium, l e a d , copper, n i c k e l and c o b a l t , t h a t have been

s p e c i a t e d wi th t h e T e s s i e r ' s scheme ', and determined i n

t h e d i f f e r e n t e x t r a c t s by D i f f e r e n t i a l P u l s e A n o d i c (DPASV)

and D i f f e r e n t i a l Pulse Adsorptive Cathodic (DPAdCSV)

S t r i p p i n g Voltammetries l o . The t o t a l metal conten ts , as

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1722 PARD0 ET AL.

w e l l as % C a C 0 3 and % o r g a n i c matter ( O . M . ) of t h e

sediments w e r e submitted t o F a c t o r Ana lys i s ( F A ) i n o r d e r

t o b e s t e x p l a i n t h e behaviour of both r i v e r s . The

s p e c i a t i o n percentages were compared and f i n a l l y , t h e

pe rcen tages corresponding t o t h e ' r e s i d u a l ' f r a c t i o n were

compared, a l s o by means of FA, with t h e r e s u l t s given by

I Salomons and For s tne r f o r o t h e r r i v e r systems.

EXPERIMENTAL

Samplinq s i t e s

The selected s i t e s are r e p r e s e n t a t i v e of t h e r i v e r i n e

systems as they p a s s through t h e c i t i e s (F igu re 1 ) . The

P i sue rga River f lows through t h e town of Val l ado l id ( ca .

400,000) , c a p i t a l of t h e Autonomous Community of Casti l la

and Leon and t h e l a r g e s t i n d u s t r i a l zone of t h a t

community " ' 1 2 . On t h e o t h e r hand, t h e CarriBn River

t r a v e r s e s t h e town of Pa lenc ia (ca. 6 0 , 0 0 0 ) where a copper

r e f i n i n g i n d u s t r y is l o c a t e d . The sediment samples were

c o l l e c t e d a t r i v e r s i d e s w i t h a dredge d u r i n g October 1989

and s t o r e d a t 3 ° C . W e t samples were always used, and %

CaC03 and b O.M. were determined fo l lowing s t anda rd

methods . Apparatus

1 3

Heavy metal w e r e determined by voltammetric

t echn iques , using a Po la reco rd Metrohm E506, a Metrohm

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HEAVY METALS IN RIVER SEDIMENTS 1723

Figure 1 .- Map of t h e s t u d i e d areas showing t h e sampling p o i n t s . ( A ) CarriBn River; ( B ) Pisuerga River .

VA663 s t a t i c m e r c u r y e l e c t r o d e s t a n d , and a Metrohm E608

c o n t r o l u n i t . The working e l e c t r o d e was i n HMDE mode wi th

a P t c o u n t e r - e l e c t r o d e and aAgCl/Agreference e l e c t r o d e .

Reaqent s

Carlo Erba RPE ACS grade s t a n d a r d s o l u t i o n s of 1000

mg/L were used for heavy me ta l s . D i lu t ed s o l u t i o n s were

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1724 PARD0 ET AL.

prepared u s i n g a GILSON 100 pL micropipet and de-ionized

water. The rest of r e a g e n t s were of a n a l y t i c a l grade.

S p e c i a t i o n scheme

A s u c c e s s i v e e x t r a c t i o n of t h e sediment w i th t h e

fo l lowing r e a g e n t s w a s performed accord ing t o Tessier e t

a l . ( a ) 1 N magnesium c h l o r i d e (adsorbed and exchangeable

metals) , ( b ) 1 M sodium acetate a d j u s t e d t o pH 5 wi th

a c e t i c a c i d (bound t o carbonate p h a s e s ) , ( c ) 0.04 M

h y d r o x i l a m i n e c h l o r h y d r a t e i n 2 5 % ( v / v ) acet ic a c i d ( b o u n d

t o r e d u c i b l e p h a s e s ) , ( d ) 30 % hydrogen peroxide a t pH 2

a d j u s t e d w i t h n i t r i c acid and then 3.2 M ammonium acetate

(bound t o O.M. and s u l p h i d e s ) and ( e ) h y d r o f l u o r i c acid

( r e s i d u a l m e t a l s ) . To ta l metal concentrat ions were obtained

by adding t h e metals found i n t h e f i v e d i f f e r e n t f r a c t i o n s .

Heavy metal de t e rmina t ion

Zn, Cd, Pb and Cu were measured by DPASV a t p H 4 .7

(acetate b u f f e r ) , with t h e following experimental s e t t i n g s :

Accumulation p o t e n t i a l -1 .2 V

Accumulation time 60 s ( s t i r r i n g ) p l u s 30 s ( rest t i m e )

Superimposed p o t e n t i a l ( s t r i p p i n g s t e p ) 50 mV

The o r d e r of appareance (from n e g a t i v e t o p o s i t i v e

p o t e n t i a l s ) is: Zn, C d , Pb and Cu.

C o and N i w e r e measured by DPAdCSV a t pH 9 . 3 (aINIIOnia

b u f f e r ) i n t h e presence of l o F 4 M dimethylglyoxime. The

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HEAVY METALS IN RIVER SEDIMENTS 1725

Ni

-1.12 -0.98

*150 UL

*loo UL

+ 50 UL

sample

E (V)

Figure 2.- Determination of Ni and Co by DPAdCSV. Concentrations of the standards: Ni = 2 mg/L, Co 2 mg/L.

experimental parameters were:

Accumulation potential -0.6 V

Accumulation time as above

Superimposed potential (stripping step) -50 mV

Figure 2 shows an example of the determination of Ni and

Co. In order to avoid the problems derived from the

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1726 PARD0 ET AL.

different analytical matrices accompanying the metals, a

semi-automatized standard addition method was used . Blank solutions were also run along the whole procedure.

All determinations were carried out at 25OC after de-

aeration with nitrogen during 10 minutes.

14

All determinations were performed in duplicate.

RESULTS AND DISCUSSION

Analysis of sediments

The Carrion River was sampled in six points (Figure

1) : upstream of Palencia (Ca-1) , downstream (Ca-6) and in

intermediate locations. The Pisuerga River (Figure 1) was

similarly sampled in f o u r points: upstream (Pi-1) and

downstream town and industrial zone (Pi-4), whereas

the rest of the sediments were taken in intermediate

positions. Table 1 shows the % O.M., % CaC03 and the mean

total metal levels f o r each sediment sample.

Factor Analysis of the total data set

The data set reported in Table 1 was studied by FA 15,16 . The first step is to build the correlation matrix of the original variables, that is shown in T a b l e 2 with

all the significant (at a P=0.05) coefficients highlighted.

From it, we can see a significant positive correlation

between % CaC03 and Ni, as well as between the pairs Zn-Pb,

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HEAVY METALS IN RIVER SEDIMENTS 1727

TABLE 1

Global data i n d r y w e i g h t bas i s for s e d i m e n t s (metal concentrat ions i n p g / g

Ca- 1 Ca-2 Ca-3 Ca-4 Ca-5 Ca-6 P i - 1 P i -2 P i -3 P i -4

4.60 2.09 3 . 7 9 0 .65 0 . 1 1 0.42 5.97 3 .55 7 . 3 7 8 .78

14 .27 14 .87 10 .57 12 .77 8.05

1 4 . 3 7 27.07 1 7 . 2 6 7 .10

1 4 . 9 9

7 3 . 0 1 0 .90 30 .36 43 .99 21.84 1 0 . 4 5 1 0 . 3 2 3 . 9 8 41.09 28 .11 4 0 . 8 9 21 .07

220.22 5 . 4 6 70.19 342 .05 5 9 . 7 1 7 . 4 4 8 8 . 4 9 1 . 5 0 78 .21 6 3 . 8 3 2 1 . 1 1 5 . 3 3 5 1 . 6 3 1 . 9 4 36.06 33 .28 2 7 . 5 2 8 . 3 8

5 2 0 . 9 8 1 0 . 7 7 163.57 494.27 6 7 . 9 1 1 0 . 5 8 195 .46 1 . 0 2 57 .62 1 2 8 . 1 4 3 8 . 6 1 5 .99

4 7 4 . 3 7 3 .24 97 .66 51 .30 358 .10 5 . 3 7 6 9 3 . 0 1 1 . 4 9 136 .20 7 0 . 1 1 49 .93 28 .07

237.10 1.56 97.56 75 .07 2 . 3 8 3 .19

TABLE 2

Corre la t ion matr ix of t h e global da ta set

%O.M. % C a C 0 3 Zn C d Pb c u Ni co ...................................................... % O.M. 1 . 0 0 0 0 . 2 3 8 0.176 0.127 0 .061 0 .062 0 .060 0.058 % CaC03 1 .000 0 . 2 9 1 0 .174 0.126 0 .158 0 . 5 9 9 0.214 Zn 1 . 0 0 0 0 .336 0 .879 0 .363 0 .422 0 .355 Cd 1 .000 0 .565 0 . 8 8 1 0 .135 0 .024 Pb 1.000 0.570 0 .228 0 . 1 9 3 c u 1 .000 0 . 0 5 1 0.124 N i 1 .000 0 . 1 7 5 co 1 , 0 0 0 .............................................................

(P=O.O5, n=18) = 0 . 4 4 4 r c r i t

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1728 PARD0 ET AL.

TABLE 3

A ) Fac to r Analysis of t h e sediment d a t a

Fac to r

% O.M. % C a C 0 3 Zn C d Pb cu N i co

0.183 0.227 0.122 -0.895 0.838 -0.286 0.788 0.363 0.909 -0.056 0.762 0.405 0.355 -0.767 0.165 0.213

0.253 -0.907 -0.123 0.098

0.397 0.018 -0.344 -0.004

0.148 0.152 -0.440 0.083 -0.098 -0.287

0.859 0.255

B ) V a r i m a x r o t a t i o n of t h e f a c t o r s

% O.M. 0 .041

Zn 0.166 Cd 0 . 9 5 0 Pb 0.381 cu 0.918 Ni 0.015 co -0.063

% C a C 0 3 -0 .140

- - - - - - - - % Variance 24.30

-0.037 -0.325 -0.240 -0.125 -0.051

0.124 0 .930 0 .090

0.020 -0.125

0.247 0.047 0.059

-0.140 -0.097

0 . 9 7 1 --------- 13.40 13.18

-0.990 0 . 1 5 1

-0.121 -0.060

0.010 -0.007 -0.049 -0.021

12.80

.-------

-0.062 -0.147 -0.885 -0.195 -0.910 -0.288 -0.186 -0.184

22.83

-_------

-0.112 0 . 9 0 3 0.171

-0.104 0.039

-0.053 0.296

-0.107

12.14

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HEAVY METALS IN RIVER SEDIMENTS 1729

Cd-Cu, Cd-Pb and Pb-Cu. However, as t h e sediments come from

two d i f f e r e n t r i v e r systems, a l l t h e s e c o r r e l a t i o n s cannot

be analysed a t t h i s p o i n t .

A B a r t l e t t ' s s p h e r i c i t y t e s t proved t h a t FA w i l l provide

a r e d u c t i o n of t h e o r i g i n a l v a r i a b l e s , and Table 3-A shows

a summary of t h e subsequent FA: t h e r e are f o u r s i g n i f i c a n t

f a c t o r s which e x p l a i n t h e 89.08 % of t h e v a r i a n c e ( O r

i n fo rma t ion ) con ta ined i n t h e d a t a set . W e can see f r o m t h e

f a c t o r l o a d i n g s t h a t Zn, Cd, Pb and Cu mainly appear i n t h e

f i r s t factor (which spans 36.63 % of v a r i a n c e ) , N i i s found

i n t h e second f a c t o r (23.34 % ) w i t h % C a C 0 3 , whereas CO i s

found i n t h e t h i r d f a c t o r ( 1 6 . 4 9 % ) and %O.M. i n t h e f o u r t h

one ( 1 2 . 6 2 % ) .

Tha above p i c t u r e can be modified by a Varimax r o t a t i o n ,

whose r e s u l t s are shown i n Table 3-B: now t h e r e are Six

s i g n i f i c a n t v a r i f a c t o r s e x p l a i n i n g a 9 8 . 6 4 % o f t h e v a r i a n c e ,

and t h e heavy meta l s have been r e d i s t r i b u t e d : t h u s Cd and

Cu are a s s o c i a t e d i n t h e f i r s t v a r i f a c t o r ( 2 4 . 3 0 % of

v a r i a n c e ) , Zn and Pb i n t h e f i f t h (86.50 % ) , whereas Co i s

i n t h e t h i r d (13.18 % ) and N i i n t h e second (13 .40 % ) . The

% CaC03, and %O.M. a p p e a r , r e s p e c t i v e l y , i n t h e s i x t h ( 1 2 . 1 4

% ) and f o u r t h (12 .80 % ) v a r i f a c t o r s . The r e d i s t r i b u t i o n

maintains t h e s i n g u l a r i t y i n t h e behaviour of N i and Co,

whereas t h e group i n i t i a l l y formed by Zn, Cd, Pb and Cu i s

broken i n two couples: Zn-Pb and Cd-Cu.

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1730 P A R D 0 ET AL.

From t h e f a c t o r l o a d i n g s and t h e o r i g i n a l v a r i a b l e s ,

we can c a l c u l a t e t h e f a c t o r s ( o r v a r i f a c t o r s ) of t h e

sediments. These new v a r i a b l e s account f o r a greater amount

of va r i ance than t h e o r i g i n a l ones, so t h e i r p l o t t i n g s w i l l

con ta in a correspondingly g r e a t e r amount of in fo rma t ion .

Figure 3-a shows a p l o t of t h e two f i r s t f a c t o r s ,

i n c l u d i n g t h e more dangerous metals (Cd, Pb and N i ) and

spanning t h e g r e a t e r amount of va r i ance ( 5 6 . 7 2 % ) . A s c a n

be seen, t h e P i s u e r g a R i v e r samples are no t i n t e r m i n g l e d w i t h

t h e C a r r i o n River ones, s o w e can say t h a t b o t h r i v e r s seem

t o behave i n a d i f f e r e n t way. Taking i n t o account t h e f a c t o r

loadings (Table 3 ) , t h e sediments w i th a h ighe r va lue of

f a c t o r 1 (P-3, P-4, C-3 and C - 6 ) a r e more p o l l u t e d than t h e

rest .

Making similar c o n s i d e r a t i o n s with t h e v a r i f a c t o r s , w e

a r r i v e a t Figure 3-b, which i s a p l o t of v a r i f a c t o r s 1 and

5 ( con ta in ing t h e more dangerous heavy me ta l s ) . Again, t h e

sediments corresponding t o P i sue rga and Car r idn are l o c a t e d

i n a d i f f e r e n t zone of t h e p lo t . Moreover, t h e two r i v e r

systems seem t o fo l low two d i f f e r e n t l i n e a r r e l a t i o n s h i p s

on which t h e sediments appear according t o t h e i r con ten t i n

heavy metals, w i t h t h e more p o l l u t e d samples (Ca-3, Ca-6,

Pi-3 and Pi-4) l o c a t e d i n an extreme of t h e l i n e and t h e less

p o l l u t e d ones i n t h e o t h e r .

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HEAVY METALS 1N RIVER SEDIMENTS

t

(A)

--2 0 v 4-4

Ca6 2 Ca5 0 ~ a 3 0

Ca 2

0 OCa& . - ePi, Pi4

Pi 2

Ca 1 - 0

- 2 t i 3

-2 0 2

1731

Factor 1

L ,o 8 .c L .- d >

- 0

- 2

I -2 0 2

Vorifoctor 1

Figure 3 . - Location of the sediments a f t e r F A i n t h e plane of ( A ) first and second f a c t o r s , and ( B ) f i r s t and f i f t h v a r i - f a c t o r s .

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TABLE 4

PARD0 ET AL.

S p e c i a t i o n of t h e heavy metals

A ) C a r r i B n R ive r Percentage of metal

Spec ia t ion ---------__________------------------------ category Zn Cd Pb c u N i co

Adsorbed and exchangeable 2 .00 9.85 0.31 3.62 0 .98 1.10 Bound to

Bound t o r e d u c i b l e ph. 56.69 28.83 44.87 1 . 6 9 25 .34 23 .35 Bound t o O.M. and su lph ides 23 .81 6 2 . 0 1 21.95 85.40 48.49 44 .62

--------------------______________L_____-------------------

carbonates 9.39 0.03 16.76 3 .12 11.49 1 .75

Residual 7.75 4.28 16 .12 7 .40 1 3 . 7 1 32.07 ........................................................... B ) Pisuerga R ive r

Spec ia t ion Category

Adsorbed and exchangeable Bound t o carbonates Bound t o r educ ib le ph. Bound t o O.M. and sulphides

1.47 9 .68 0.19 3 .24 2 .90 1 . 7 9

8.15 0 .77 16 .70 2.27 14 .82 2.08

57.72 2 5 . 6 1 51 .36 0 .59 15 .90 41.40

24.78 55 .92 17 .85 80.72 61.37 35.19

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HEAVY METALS IN RIVER SEDIMENTS 1733

Spec ia t ion of heavy metals

Table 4 shows a summary of t h e s p e c i a t i o n resu l t s of t h e

s i x heavy metals expressed as percentages of metal found i n

each s p e c i a t i o n category. I n g e n e r a l , as po in ted o u t by

Salomons and For s tne r ', t h e ' r e d u c i b l e phase ' i s an

important r e s e r v o i r for a l l heavy metals, as we l l as t h e

' o rgan ic phase ' . The fo l lowing i n d i v i d u a l c o n s i d e r a t i o n s can

be a l s o drawn:

( a ) &. I t s d i s t r i b u t i o n amongst t h e s p e c i a t i o n

c a t e g o r i e s i s ve ry similar i n both r i v e r s , appearing mainly

i n t h e 'bound t o r e d u c i b l e phases ' and 'bound t o O.M. and

s u l p h i d e s ' f r a c t i o n s .

( b ) Cadmium. Both r ivers behave i n t h e same way: the

'bound t o O.M. and s u l p h i d e s ' f r a c t i o n has now t h e h ighe r

m e t a l percentage. The c o n t e n t i n t h e 'adsorbed and

exchangeable ' f r a c t i o n is r e l a t i v e l y high although the t o t a l

con ten t of metal i n t h e sediments is r a t h e r l o w , t h u s

d imin i sh ing i ts environmental impact.

( c ) Lead. E x h i b i t s a d i s t r i b u t i o n very s i m i l a r t o t h a t

found f o r Zn, b u t i t s corresponcting percentages i n t h e

' r e s i d u a l ' and 'bound t o ca rbona te ' f r a c t i o n s are higher .

( d ) Copper. Th i s metal a p p e a r s almost e x c l u s i v e l y i n t h e

'bound t o O.M. and s u l p h i d e s ' f r a c t i o n , and shows t h e more

marked tendency t o appear i n t h a t phase from a l l examined

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1734 P A R D 0 ET AL.

elements. Th i s behaviour is similar t o L\at found by Salomons

y For t sne r 7, i n t h e i r s t u d y on 18 d i f f e r e n t r i v e r systems.

The mean percentage i n t h e ' r e s i d u a l ' f r a c t i o n i n P i sue rga

River i s t w i c e t h a t corresponding t o Car r i6n R ive r ,

showing t h e e f f e c t o f t h e copper i n d u s t r y o n t h i s l a s t r i v e r .

( e ) Nickel. Although t h e metal appea r s mainly i n t h e

'bound t o r e d u c i b l e phases ' and 'bound t o O.M. and s u l p h i d e s '

c a t e g o r i e s , t h e mean r e l a t i v e pe rcen tages i n t h e two r i v e r s

a r e d i f f e r e n t i n t h e sense t h a t i n t h e C a r r i B n River t h e

g r e a t e r percentage i s found i n t h e more e a s i l y remobil ised

'bound t o r educ ib le phases ' f r a c t i o n , perhaps t h e e f f e c t of

e x t e r n a l p o l l u t i o n .

( f ) Cobalt . Th i s metal i s a l s o found i n a greater

extension i n t h e 'bound t o r e d u c i b l e phases ' and 'bound t o

O.M. and s u l p h i d e s ' f r a c t i o n s f o r P i sue rga , whereas f o r

Carr ion t h e predominant c a t e g o r y is t h e second one, w i t h a

g r e a t e s t percentage i n t h e ' r e s i d u a l ' c a t egory .

The eco - tox ico log ica l i m p l i c a t i o n s are d i f f e r e n t f o r

t h e f i v e c a t e g o r i e s acco rd ing t o t h e corresponding

r emob i l i za t ion c a p a c i t y of t h e metals towards t h e d i s s o l v e d

s ta te . I n t h i s way, t h e m e t a l s p r e s e n t i n t h e f i r s t t h r e e

f r a c t i o n s of t h e Tess i e r ' s scheme: 'adsorbed and

exchangeable ' , 'bound t o c a r b o n a t e s ' and 'bound t o r e d u c i b l e

phases ' are t h e more dangerous, because t h e y could be

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HEAVY METALS IN RIVER SEDIMENTS 173s

TABLE 5

Percentages of ' r e s i d u a l ' f r a c t i o n f o r s e v e r a l r i v e r systems

Elbe Rhin Meuse Scheldt Ems 1 jssel . Some Seine Gironde Garonne Ottawa Magdal ena Orinoco Chao-Phya Zaire Ruhaha C a r r i 6 n P i s u e r g a

0.00 17 .40

4 .40 4.40 9.70 9 .70

28.30 30 .40 43 .50 47 .80 87 .00 83 .90 87 .10 64 .50 54 .80 87 .10

7.75 7.89

17 .40 17 .40 23 .90 21.70 22.60

3.20 4.40

47 .80 34 .80 30 .40 69 .70 95 .50

100.00 2 2 . 6 0 19 .40

100.00 16 .12 13.67

0.00 23 .90 1 7 . 4 0 21 .70 43 .20 22.60 63 .00 47 .80 69 .60 69 .60 91 .30 74 .20 93 .50 51.60 51.60 63.20

7.40 13.39

39.10 17 .40 56 .50 39.10 31.00 52.90 26.10 60.90 78 .30 73.90 87.00 82 .60

100.00 74.20 71 .00 83.90 13 .71

5 . 0 1

remobilized by modi f ica t ions i n t h e pH ( ' adsorbed and

exchangeable ' and 'bound t o c a r b o n a t e s ' ) o r i n t h e red-ox

p o t e n t i a l ( 'bound t o reducible phases ' ) of t h e water column

o v e r l y i n g t h e sediments. Therefore,examining Table 5,

w e may conclude t h a t Zn and Pb a r e t h e more easy t o be

r e l e a s e d b e c a u s e t h e y a r e m a i n l y contained i n t h e f i r s t t h r e e

s p e c i a t i o n c a t e g o r i e s : 67.34 - 68.08 % f o r Zn and 61.94 - 68.25 % f o r Cd The o t h e r metals a r e present i n a g r e a t e r

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1736 PARD0 ET AL.

1

N L. 0 U 0 L

I

0

-1

t I

5 mrn! G a ron ne Z a i r e . OGironde

C h a0 - P b a

oljssel

.Ems

Scheldt .Seine Rhin .Meuse

eisuerqa

'W Elbe

Ottawa

0 r inoco

M a g d d e n a , 1 R u h a h a .

-1 0 1 1 Fat t or 1

Figure 4 . - Location of t h e r i v e r systems a f t e r FA of t h e i r ' r e s i d u a l ' f r a c t i o n percentages i n t h e p lane of t h e f i r s t and second f a c t o r s .

extension i n t h e l a s t two f r a c t i o n s , 'bound t o organic m a t t e r

and su lphides l and ' r e s i d u a l metals' , whose remobi l iza t ion

i s m o r e d i f i c u l t , s o t h e i r p o s s i b l e danger t o t h e environment

i s smaller .

Comparison of t h e p o l l u t i o n l e v e l s with o t h e r r i v e r systems

1 Salomons and Fors tner have devised a method t o

e v a l u a t e t h e p o l l u t i o n degree of a r i v e r , by examining t h e

percentage of heavy metals found i n t h e ' r e s i d u a l ' f r a c t i o n

of t h e Tessier 's scheme. This f r a c t i o n c o n t a i n s t h e metals

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HEAVY METALS IN RIVER SEDIMENTS 1731

i n c l u d e d i n t h e d e t r i t i c o r l a t t i c e m a t e r i a l o f t h e sediment,

and w e can suppose t h a t t h e metal pe rcen tages i n t h a t phase

w i l l be smaller i n p o l l u t e d than i n non-polluted r i v e r s . The

r eason ing behind t h i s i s t h a t t h e metals de r ived from

p o l l u t i o n , w i l l be inco rpora t ed i n t o t h e sediments i n t h e

more l a b i l e f r a c t i o n s of t h e s p e c i a t i o n scheme. Table 5

p r e s e n t s a summary of t h e d a t a given by t h e above a u t h o r s

' f o r Zn, Pb, Cu and N i (Cd and C o were not considered by

them) , a long t h e mean r e s u l t s found by u s f o r Pisuerga and

Carr iBn. A s t h e r e s u l t i n g d a t a se t i s d i f f i c u l t t o e v a l u a t e

a t a f i r s t g l ance , w e have a l s o c a r r i e d ou t a FA whose

r e s u l t s , not shown h e r e f o r t h e sake of s i m p l i c i t y ,

i n d i c a t e t h e existence of a s i n g l e s i g n i f i c a n t f a c t o r

( 8 4 . 1 5 % o f t h e v a r i a n c e ) composed of p o s i t i v e c o n t r i b u t i o n s

of t h e f o u r metals. A second f a c t o r ( 8 . 1 4 % of t h e v a r i a n c e ) ,

i s mainly made from Pb and Cu. Figure 4 is a p l o t of t h e

f a c t o r s c o r e s ( i n c o r p o r a t i n g a 9 2 . 2 9 % of Table 5 ) . W e can

observe t h a t Pisuerga and CarriBn are l o c a t e d amongst t h e

r i v e r s belonging t o western Europe and f a r away from r i v e r s

of l e s s - i n d u s t r i a l i z e d zones (mainly of t h e sou the rn

hemisphere) , showing t h a t t h e two examined Spanish r i v e r s

behave i n a s imilar way to r i v e r s of i n d u s t r i a l i z e d zones.

ACKNOWLEDGEMENTS

The a u t h o r s wish t o thank. D . G . I . C . Y . T . (PB87-0903) of t h e Spanish M i n i s t e r i o de EducaciBn y C ienc ia and t o J u n t a

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1738 PARD0 ET AL.

de Castilla y Leon (Consejeria de Cultura) for financial support.

REFERENCES

1.- Purves, D. , Trace-Element Contamination of the Environment (Elsevier, Amsterdam, 1985) , pp. 6-16.

2.-Leppard, G.G. (Ed.), TraceElement Speciationin Surface Waters (Plenum Press, New York, 1983), pp. 1-15.

3.- Nurnberg, H.W., Anal. Chim. Acta, 164, 1-21 (1984).

4 . - Smies, M. , in Trace Element Speciation in Surface Waters (Leppard, G . G . Ed.) (Plenum Press, New York, 1983), pp. 177- 191.

5.- Forstner, U., in Chemical Methods for Assessing Bio- available Metals in Sludges and Soils (Lechsber, R., Davis R.D. and L'Hermite, P. , Eds.) (Elsevier, London, 1985), pp. 1-30.

6.- Gibbs, R.J., Science, 180, 71-73 (1973).

7.- Salomons, W. and Forstner, U. , Envir. Technol. Let. , I., 506-517 (1980).

8.- Oakley, S.M., Nelson, P.O. and Williamson, K.J, Envir. Sci. Technol., 15, 475-480 (1981).

9.- Tessier, A . , Campbell, P.G.C. and Bisson, M. , Anal . Chem., 5 l , 844-851 (1979).

10.- Nurnberg, H.W., 2 . Anal. Chem., 316, 557-565 (1983).

11.- Pardo, R. , Barrado, E. , Arranz, A. , Perez, J.M. and Vega, M., Int. J. Envir. Anal. Chem., 37, 117-123 (1989).

12.- Pardo, R . , Barrado, E., Perez, L. and Vega, M., Wat. R e s . , 24, 373-379 (1990).

13.- Commission of the European Communities, Work-shop on Standardization of Analytical Methods €or Manure, Soils, Plants and Waters, Gent (1978).

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HEAVY METALS IN RIVER SEDIMENTS 1739

14.- Pa rdo , R. , Barrado, E . , Tascon, M.L. and Vazquez, M.D. , Quim. Anal., 8, 99-107 ( 1 9 8 9 ) .

15.- Knudson, E . J , Duewer, D . L . , C h r i s t i a n , G.D. a n d L a r s o n , T .V . , i n Chemornetrics: Theory and Appl ica t ion (Kowalski, B.R. E d . ) , (A.C.S. Symposium S e r i e s , Washington D . C . , 1 9 7 7 ) , pp. 80-116.

16.- Hopke, P.K., i n Analy t ica l Aspec ts of Environmental Chemis t ry (Natusch , D.F.S. and Hopke, P.K., Eds.), (Wiley, N e w Y o r k , 1983) , pp. 219-262.

Received Xovember 16, 1992 Accepted February 22, 1993

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