distribution of trace and major elements in sediment and

ELSIZVIER Marine Chemistry 53 (1996) 285-299

Distribution of trace and major elements in sediment and pore waters of the Lena Delta and Laptev Sea

Rob F. Nolting, Maarten van Dalen, Willem Helder

Netherlunds Institute for Sea Research, P.0. Box 59. 1790 AB Den Burg, Texel, The Netherlands

Received 25 May 1994: accepted 5 January 1995

Abstract

Sediment cores collected during the SPASIBA expedition in 1991 were analysed for their trace- and major element concentrations. Leachable (0.1 N HCI) as well as residual concentrations were determined. Fe and Mn were measured in the interstitial waters to characterize redox conditions. Lateral dis~bution patterns of solid phase Cu, Cd, Ni, Pb and Zn show a

small increase in concentration from the Lena Delta in seaward direction. In general concentrations of these metals are very low and similar to natural background values. With some exceptions, solid phase profiles with depth of all investigated elements do not show strong variations. No enrichment of Pb and Zn in surface layers was found. Remobilization processes

and transport of particles enriched in Mn are responsible for Mn accumulation in a particular area. Pore-water concentrations of dissolved Mn in the latter sediments are very high (> 700 FM) and suggest strong Mn reduction directly below the sediment-water interface. In contrast to Mn, the depth profiles of Cd show a surface layer with lower concentrations and an

increase deeper down the sediment. The C/N ratio in the sediment decreases from 13 in the Lena mouth to 9 in the more marine part of the Laptev Sea. Surface sediments in the Laptev Sea are very uniform and homogeneous and show only small

concentration gradients.

1. Introduction

While other large rivers and the adjacent coastal systems have been extensively studied for their geo-

chemistry and sedimentoiogy fe.g Mississippi: Trefry et al.. 1985; Wright and Coleman, 1974; Amazon: Eisma et al., 1991; Zaire River: Jansen and Van der Gaast, 1988; Yellow River: Wright, 1989) this is not the case for the River Lena. The Lena River belongs,

however. together with the Yenissei River to the two

largest rivers discharging into the Arctic Ocean and is the eighth largest in the world with a water

discharge of 525 km” yr- ’ . Its yearly solid discharge to, mainly the Laptev Sea, is estimated 17.6 X IO6

ton yr -I (Gordeev and Sidorov, 19931, with a large

monthly variation. The water discharge can be 60

times higher in June than in April (Letoile et al.,

1993). This scarcity of investigations on sediments of the

Lena River and adjacent estuary is mainly due to the rather harsh weather conditions and logistical diffi-

culties. Access to the Lena River and adjacent Laptev Sea is only possible in the months of August and September.

Due to the fact that the Lena River belongs to the largest river systems in the world and is situated in an almost pristine environment, it is interesting to compare this system with other anthropogenically influenced ones. In 1989 a first survey in the Lena delta and Laptev Sea was unde~aken in the frame-

0304-4203/96/$15.00 Q 1996 El. sevier Science B.V. All rights reserved

SSDI 0304-4203(95)00095-x

286 R. F. Nolting et cd. / Morinr Chemistyv 53 (1996l 285-299

work of the Scientific Programme on Arctic and

Siberian Aquatorium (SPASIBA), and part of this work was published before (Church and Windom, 1993). A second expedition was carried out in September 199 1. While the first expedition was lim-

ited to studies in the overlying water, the second one

was of a more ambitious type. Not only the water

column was investigated, but a large part of the research was focused on sediment studies.

The purpose of the investigations on sediments

and pore water was to study diagenetic behaviour of metals, to determine concentration levels and distribution patterns of trace metals and major elements, and to study the influence of suspended particulate

matter @PM) supplied by the Lena River to the adjacent Laptev Sea. To fulfil this goal the lateral

distribution as well as depth distribution patterns of

trace- and major elements are presented. A complete data set of this research is available

on request (Van Dalen and Nolting, 1992).

I .27 I

125 135

2. Sampling and analysis

Sediment samples were collected with a boxcorer

in the Laptev Sea (stations C20-C38) and with a small grab in the Lena River and estuary (stations l-27) in September 199 1. Station numbers and posi-

tions are given in Fig. 1. Station 1 is situated in the

upstream part of the Lena River. For the river and

estuarine survey the Ulkhon, a small tugboat, and for the Laptev Sea the R.V. Jacob Smirnitski, were

used. The boxcorer of Russian design was rectangu- lar (30 X 40 cm), about 2 m long, with two dis-

mountable panels at one side. Depending on the depth of penetration in the sediment, the upper or lower panel was opened. Due to this design, it was

not possible to sample overlying water and sometimes the uppermost sediment layer (1 cm) was

slightly disturbed. Depending on penetration depths of the corer three subsamples of maximum 14-cm

length were taken from the box by inserting transpar-

12E030’ 129O 129O30’

72’

Fig. 1. Map with station numbers and sampling positions in the Laptev Sea boxcore stations C20-C38 (A) and in the Lena estuary (grab samples) (B). The enlarged map of the Lena estuary is indicated as rectangle in chart A.

R. F. Noltin~ et crl. /Marine Chemists 53 (I 9%) 285-294, 287

ent pvc liners (6 cm diameter) into the sediment.

Sometimes it was not possible to collect cores of this length, but shorter ones (10 cm) were sampled. Subcores were closed with rubber stoppers. Directly after subsampling, the cores were divided into ten

slices which progressively increase from 0.5 cm at the top to 4 cm at the bottom of the core (Nolting

and Helder. 1991: Nolting and Van Hoogstraten, 1992). Slices from the same depth were combined in

clean Teflon squeezers (Reeburgh, 1967) and pore water was removed from the sediment by squeezing the sediment over a 0.2 pm cellulose-acetate filter

under nitrogen pressure (l-3.5 bar) and collected in small Teflon vials. The slicing procedure took only 5

min after which the samples were directly stored

under nitrogen gas. In our experience this procedure, in which the core slices are exposed to air during a

short period (max. 5 min), has only minor effects on pore-water profiles of Fe’+ and phosphate. There-

fore the profiles of Fe’+ (Fig. 5) should be inter- preted with some care (see also Discussion). After squeezing, pore waters were acidified to pH 2 with

HCI I2 N (Suprapur, Merck). Sediment slices were packed in plastic bags and stored in a refrigerator.

Additionally, suspended particulate matter @PM)

was collected by pumping water over a filter (Nucleopore 0.45 pm>.

Trace and major elements in the sediments were sequentially determined after leaching during I8 h

with 0.1 N HCI (Duinker and Nolting, 1976) and in the residual fraction after treatment with HF/Aqua

Regia (Rantala and Loring, 1977). The 0.1 N HCI leachate contains the “easy exchangeable” metal fraction. Duinker et al. (I 974). This method is regu- larly checked at our laboratory with reference sam-

ples. and a loss of approximately 6% was found by summing up the leachable and residual fraction com-

pared to the total destruction (Van Hoogstraten and Nolting. 199 I ; Happee and Nolting, 1994). In the

SPM only the total element concentrations were determined. Copper, cadmium, lead and nickel were determined by graphite-furnace atomic absorption

spectrometry (GFAAS; Perkin Elmer, 5100; Zee- man> with the stabilized temperature platform furnace (STPF) technique. All other elements were determined by flame AAS (Perkin Elmer 2380). The precision of the method was checked by analysing a representative sample five times, for the leachable as

Table I

Results of five-fold analyses of a representative sample. Presented

are mean concentrations and standard deviation from the leachable

and the residual fraction, Total. represents the summation of the

individual leachable and residual results of each sub-sample

Element Leachable Residual Total

(n=5) (n=5) (n=S)

Cd rig/g 1Ok8 41*s so+ I3

Cu pg/g 4.37 kO.40 4.62 10.24 8.99 f 0.63

Pb pg/g 5.3 I i 0.3 I 9.60 + 0.47 14.90+0.46

Ni Kg/g 2.35 i 0. I I 9.54 -+ 0.33 11.89~0.31

Mn I*g/g 34*3 14l*l2 175ill

Zn pg/g (n.d.)’ (n.d.) (n.d.)

Fe 8 0.35 + 0.01 1.63 f 0.05 I .98 + 0.06

Mg % 0.078 + 0.004 0.42 5 0.01 0.50 + 0.01

Al % 0.085 &O.OOl 5.2 I * 0.22 5.3OkO.22

Ca c7r 0.093 i 0.003 0.40 + 0.06 0.49 + 0.05

Si c?c (n.d.) 32.9 f I .6 32.9 & I .6

’ n.d. = not determined.

well as for the residual fraction. These results, and the standard deviation of all elements investigated in

the two fractions, are presented in Table 1. As a control for the accuracy of our procedure reference

sediments, supplied by the EC Bureau of References (BCR 320 and BCR 1421, were included during the whole analytical procedure. For all elements investi-

gated the measured and certified values were in good

Table 2

Concentration of trace elements and major elements as their

oxides in reference material BCR no. 320 (river sediment) and

BCR no. 142 (light sandy soil). Presented are the results deter-

mined with our method and those reported by the BCR (Brussels).

certified and 95% confidence interval. Concentrations between

brackets are reported but not certified by the BCR (Griepink and

Muntau, 1988)

BCR no. 320

Determined Certified

BCR no. 142

Determined Certified

Cd kg/g 0.441

cu pg/g 41.1

Pb cLg/g 38.4

Ni kg/g 70.8

Mn pg/g 803

Zn kg/g 154 FelO, c/r 6.56

MgO % 3.4s

Al,O, % IS.52

CaO % 2.54

SiO? % 62.13

0.533 + 0.026 0.25

44. I + I .o 24.9

42.3 k I .6 34.7

15.2 f I .4 30.6

(78216) 571

142k3 95.1

(6.41 *O.lO) 3.05

(3.24rtrO.05) 1.13

(15.72iO.47) 8.61

(2.35+O.l I) 4.67

(59.60* I .97) 69.01

0.25 f 0.09

27.5 1-0.6

37.81 I.9

29.2 * 2.5

(569 + 26)

92.414.4

(2.80) (1.09)

(9.48)

(4.94)

(68.22)

288 R.F. Nolring et al. /Marine Chemist? 53 f IYWI 285%2YY

40

35

30

g 25

iijm

15

10

5 Si (%) = 42.4 - 2.2 Al (%) R = 0.77

0 1 2 3 4 5 6 7 6 9 10

Al (W

Fig. 2. Relation between silicium and aluminium in all sediment

samples from the Laptev Sea.

agreement (Table 2). Blanks were for most elements negligible and, when appropriate, corrected for.

Zinc, iron and manganese in pore water were determined by flame AAS by directly aspirating the

solution into the flame. Concentrations were measured against standards and compared with standard

addition measurements.

Organic carbon and total nitrogen were determined with a Carlo-Erba NA 1500 CHNS analyser

according to Verardo et al. (1990). Total element concentrations of all sediment sam-

ples and Fe, Mn and Zn concentrations in pore waters are given in Appendix A.

3. Results and discussion

3.1. Stud?; site

The Laptev Sea is a shallow marginal sea with

water depths ranging from 10 m near the delta (Tiksi) to 60 m at 77”N (Fig. 11. Some shallow parts are present in the middle of the research area where the water depth is not more than 5-6 m. In a north-east direction water depth increases to > 30

m in the vicinity of Kotelny Island (stations C25.

C27 and C28). In the Laptev Sea high turbid surface waters, up

to more than 400 km from the river delta, are observable. Between 10 and 20 m turbidity is low and the most turbid water is found near the bottom

due to resuspension of bottom sediments, creating a three layer stratification (Burenkov, 1992, Cruise Report Spasiba Expedition). The influence of the

solid discharge by the Lena River has a maximal

spreading in eastern direction. Also the bottom salinity distribution (Cauwet and Sidorov, 1996-this is-

sue) suggests a bottom current direction in east-

north-east direction.

3.2. Distribution in sur$ace sediments

3.2. I. Major elements

The calcium carbonate content in sediments from

the Laptev Sea is around I%, so there was no need to express the trace metal concentrations on a calcium carbonate free basis. The mean major element

composition and variability (+ 1 s.d) expressed as their oxides and calcium carbonate (a) in the surface

sediments are, CaCO, 1.21 _t 0.73, MgO 1.83 _t

0.63, Fe,O, 5.34 + 1.97, Al,O, 12.41 & 1.75 and SiOz 60.54 & 6.28. It shows that the sediment is of

the siliceous type. The sum of the oxides. CaCO,, MgO, Fe,O,, Al,O, and SiO? is around 85% in the whole area. The correlation between Si and Al (Fig. 2) indicates that the sediment in the Lena estuary and Laptev Sea is a mixture of fine-grained clay minerals

and quartz. Fine-grained, carbonate free, sediments

have a Si/Al ratio of 2.4 (Krauskopf, 1965). deep sea clay of 2.9 and river particulate material 3.0 (Martin and Whitfield, 1983). In siliceous sediments

this ratio is 5 or higher. The Si/Al ratio in Lena and Laptev Sea sediments range from 3.3 to 14.0 with the highest ratios in the delta.

Sedimentation rate determinations from ““Pb profiles (J. Kalf and D. Eisma, personal communica- tion; Eisma et al., 19891 indicate very irregular ““Pb patterns, which did not allow to estimate sedimenta-

Fig. 3. Distribution pattern of Cu. Cd, Ni. Pb. Zn (kg g- ’ ) and C/N ratio in the upper surface (O-2 cm) layer of sediments from the Laptev

Sea.

R.F. Nolting et al./Marine Chemist? 53 11996) 285-299

1 Laotev Se0

I-- - 4

Laptev Sea

290 R.F. Nolting et al. /Marine Chemistrv 53 (1996) 285-299

13!Y

Loptev Sea

Fig. 4. Distribution pattern of Mn (kg g- ’ ) in the upper surface

(O-2 cm) layer of sediments from the Laptev Sea.

tion rates, but are indicative for considerable rework- ing and mixing.

3.2.2. Trace elements

The distribution in surface sediments of total Cu,

Ni, Cd, Pb and Zn (pg g-‘) and the C/N ratio in

the upper 2 cm of the sediment is given in Fig. 3. Concentration gradients for all elements are rather

small. For Cu lowest values are found in the river dominated area, with a gradual increase in seaward

direction. For all other metals river dominated sediments have relatively high concentrations. Further offshore a minimum concentration area can be detected for all metals, apart from Cu, while more

offshore concentrations increase again. A similar distribution pattern for those metals in SPM from the

Lena River was reported by Martin et al. (1993). These phenomena can be explained by a particle size effect, induced by mixing of coarse river material with marine derived organic material (Duinker and

Nolting, 1976; Nolting and Eisma, 1988; Nolting et al., 1990). Apart from this, bottom currents as indicated by the bottom salinity distribution (Cauwet and

Sidorov, 1996-this issue) and sediment transport (Burenkov, 1992, Cruise Report Spasiba Expedition),

can explain the observed distribution patterns of Cu,

Ni, Pb, Cd and Zn. The concentrations of trace metals and the ele-

ment/Al ratio in SPM, calculated with the data reported by Martin et al. (1993) and this study, are

almost similar to those in the sediment, Ni/Al (3-4 x 10p3), Pb/Al(2-3 x 10-4), Cd/Al (0.1-0.25 x lo-‘), Fe/Al (0.4-0.61, Cu/Al (0.5-2.5 X lo-‘)

and Zn/Al (5- 19 X lo-” 1. It indicates that SPM supplied to sediments in the Laptev Sea does not

change remarkably with respect to its trace metal content, or that trace metals are not released from the

suspended matter. The Fe/Al ratio (0.4-0.6) is in-

termediate between river SPM (0.4) and shore mud (0.8) (Martin and Whitfield, 1983) but similar to

those reported for fine-grained carbonate free bottom sediments (0.4) (Krauskopf, 1965).

Concentrations of all the investigated metals are similar to those reported for unpolluted continental soils and near shore mud (Chester, 1990), indicating

that trace metal levels in sediments supplied by the Lena River to the Laptev Sea are natural background

values. Based on the element/Al ratio, concentrations of Cu, Zn, Ni and Pb are for instance a factor

of 2-3 lower than those found in recent sediments in the Rh8ne delta. For Cd this factor is 10 (Nolting

and Van Hoogstraten, 1993). The distribution of Mn in surface sediment is

shown in Fig. 4. It shows a strong increase from

1000 CLg g ’ in the delta to more than 5000 pg g-I in east north-eastern direction. Although the distribution pattern of Mn can be explained in the same way

as for the other metals, a more detailed discussion will be given in the next chapter.

The C/N ratio (Fig. 31 shows a clear decrease from a value of 13 in the river mouth to 9 in the more northern part of the Laptev Sea. When the C/N ratio is used to discriminate the contribution of

Fig. 5. Depth profiles of residual n and total Fe 0 (7%) and Mn (p,g g- ’ ) and interstitial water concentration 0 (PM) at boxcore stations

C20, C21, C25 and C28.

292 R. F. No/ring et al. /Marine Chemisrq 53 (I 996128.5299

marine derived organic carbon fraction from the terrestrial one, using the following end-member com-

positions: terrestrial C/N = N 90 (Macdonald et al., 1991) and marine C/N = N 6.2, we calculate that 60% of the organic carbon in the sediment of the

river mouth is from terrestrial origin while in the

more marine part this fraction accounts for 35%. Cauwet and Sidorov (1996-this issue) measured particulate organic carbon (POC) concentrations in SPM

in the lower reaches of the Lena River, and found 3.1-4.3% organic C. These values are somewhat higher than the organic carbon concentrations found

in surface sediments of the Laptev Sea.

3.3. Depth distribution in sediment

3.3.1. Major elements

Vertical profiles of Ca, Mg, Al and Si do not

show much variation with depth, only occasionally some differences occur where sand layers are present (data in Appendix A). The lowest Ca concentrations are found in the deeper parts of the Laptev Sea. Based on the lateral and depth distribution of the

major elements, it can be concluded that the top sediment layer in the Laptev Sea is very uniform and homogeneous. This is probably a result of resuspen-

sion and mixing of sediment. During high discharge

(June-August) 96% of the yearly TSM is exported

to the Laptev Sea (LCtoile et al., 1993; Cauwet and Sidorov, 1996-this issue). During these periodic events a huge amount of TSM is spread out on the bottom of the Laptev Sea and mixes with the previ-

ously deposited sediments, a process repeated each year, preventing a regular sedimentation. Serova and Gorbunova (pers. commun.) state that the dominant physical weathering in the basin defines the input of

fresh material to the sea in which unchanged rock grains from the continent are abundant.

In contrast to the earlier described elements, Mn and Fe show a more interesting behaviour. As already described, the lateral distribution in surface sediment of solid Mn shows an increase from 1000

pg g ’ in the mouth of the river to > 5000 pg g- ’ in the eastern part of the Laptev Sea. By closer inspection of the depth profiles of total and residual solid Mn and interstitial water Mt-?+, we can try to explain these increases. In Fig. 5 some characteristic profiles of Mn and Fe are shown. As example the

stations C20 close to the river and C28 near Kotelny Island are discussed. At station C20 the Mn*+ con-

centration increases from 0 p,M at the sediment-

water interface to a concentration of 300 p,M at 9 cm depth. The solid phase Mn shows a strong increase

in the exchangeable fraction in the upper 2 cm due to

reoxidation of upward diffusing Mn’+. Down core the ratio between residual and total Mn stays constant (0.51). In contrast to this, the Mn2+ concentra-

tion at station C28 is already high (700 p_M) at the sediment-water interface and stays relatively constant down core. This high Mn*+ concentration indi-

cates strong reducing conditions and an exchange of Mn2+ to the overlying water column (slow oxidation

kinetics) where it can be oxidized again and deposited as Mn-ox. The high solid phase Mn concen-

tration at this station is mostly in the exchangeable fraction through the whole core and indicative for

Mn recycling processes and Mn accumulation. The

ratio between residual and total Mn in this core is 0.10, indicating that 90% of Mn in the sub-surface layer is in the exchangeable fraction compared to 50% at station C20. These observations are in accordance with a system in which Mn enriched particles are transported from the shallow coastal area to the

central part of the Laptev Sea. The bottom current direction and the existence of a nepheloid layer near

the bottom (Burenkov, 1992, Cruise Report Spasiba Expedition; LCtoile et al., 1993) support this observa-

tion and explains the existence of the area covered by stations C25, C27 and C28 where increased Mn concentrations are present.

Mn recycling processes are well described for other coastal sediments and representative for areas

with a high organic C input (Sundby et al., 1981; Sundby and Silverberg, 1985; Nolting and Eisma, 1988; Helder, 1989). Manganese fluxes from conti-

nental margin sediments were recently measured by Johnson et al. (1992). The highest fluxes they ob-

served were on the shallow continental shelf, in accordance with our observations.

Dissolved Fe profiles follow the normal pattern in

which dissolution of Fe-oxides takes place below that of Mn (Fig. 5). For station C20 this increase of Fe’+ starts at 2 cm, well below the zone where MnO, precipitates, and increases down the sediment to 300 p,M at 9 cm. Upward diffusion of dissolved Fe results in FeO, precipitation, indicated by a small

R. F. Ndting et al. /Marine Chemistryc 53 (1996) 285-299 293

band of higher leachable Fe content at around 2 cm.

This is well below the zone where MnO, precipitation is observed. At station C28 a strong dissolution of Fe starts at 2 cm to a maximum of 60 pM and stays rather constant deeper down the sediment.

3.3.2. Truce elements

In most sediment cores, concentration-depth profiles of Cu, Pb, Cd, Ni and Zn do not show much variation. They mostly reflect the concentrations given by the surface distribution pattern. For stations

C2 1, C28 and C36 depth profiles of Cu, Pb, Cd and Zn are shown in Fig. 6. The enrichment of Zn, Pb

and, in some cases, Cu to the surface layer as observed in many coastal areas around the world

(Bruland et al., 1974; Gobeil and Silverberg, 1989;

Macdonald et al., 1991; Nolting and Helder, 1991; Nolting and Van Hoogstraten, 1992; and many oth-

ers) is not observed here. Only Pb, Zn and Cd show in some profiles a small gradient and those cores are

described below. At stations C25, C27 (not shown) and C28 the

profiles of the residual Pb content show an increase to the surface of the sediment while the total concen-

tration remains constant (Fig. 6). These stations are

situated in the area where the high Mn concentrations are found. Indeed, the strong increase in the residual Pb fraction to the surface coincides with that of Mn. This suggests that Pb is subject to diagenetic changes and redox processes controlled by Mn. Gob- eil and Silverberg (1989) demonstrated that Pb is

subject to early diagenetic processes in Laurentian Trough sediments, redox-controlled by cycles of Fe diagenesis. Unfortunately we have no pore-water data for Pb, but the decrease of the leachable Pb fraction to the surface in core C28 is similar to the

decrease of extractable Pb observed by Gobeil and Silverberg (1989) in their profiles. The low and

constant Pb concentrations indicate that anthropogenic inputs are of minor importance, this in

contrast to other areas around the world. Only at station C27 zinc profiles (not shown)

show a small increase in concentration to the sediment surface, in the residual fraction as well as in the leachable one. This can be a particle size effect or accumulation by manganese (hydroxy-oxide) precipi-

tation. Although Cd concentrations are very low in the

Fig. 6. Depth profiles of residual Cu 0, Pb n and total Cu 0, Pb •1 (&g g-’ ) (A) and residual Zn n and total Zn 0 (&g g-’ ) and

residual Cd 0 and total Cd 0. (ng g-’ ) (B) at stations C21, C28 and C36.

294 R. F. Nolting et al. / Marine Chemistry 53 (1996) 285-299

sediments ( < 100 ng g - ’ 1, some trends can be observed. At most stations the Cd concentration increases with depth (Fig. 6). Both the leachable and residual fractions account for this increase, but the leachable fraction contributes most. Gobeil et al. (1987) described the relatively complex behaviour of

Cd during early diagenesis in Laurentian Trough sediments. The processes they describe can also explain the observed Cd distribution in Laptev Sea

sediments. Cadmium is released from the sediment in the oxygenated zone due to the degradation of

fresh organic matter and dissolves. Due to downward

diffusion dissolved Cd precipitates, probably as a sulfide phase (Gobeil et al., 1987) below the oxygenated zone, and total Cd content increases.

Station C36 close to the Lena mouth (Fig. 6) is an example of a depth profile where different sediment

layers are present. The strong minimum in trace metal concentrations at 7 cm depth is correlated with

an increase of silicate from 52% at the top to 60% at 7 cm. At the same depth the Al content decreases

from 7% to 5.5%. It indicates that we are dealing with a sub-surface sandy layer covered with a sedi-

ment layer characteristic for the whole area. The sandy layer seems to be specific for this part of the

Laptev Sea, because at station C38 close to station C36 no boxcore sample could be obtained due to the presence of a very hard sandy layer. Another indica- tion that this observation can be described by a

physical phenomenon and not by chemical processes is shown by the good correlation that exist between leachable Cu, Pb and total Al (Fig. 7). Higher con-

centrations of Cu and Pb are correlating with higher Al contents (more clay minerals) and, by dilution

4- 0

0

2-

0 5

l cu Lolglg)

C36 0 Pb L(w’~I)

I 1 6 7

Al T (%)

Fig. 7. Relation of leachable copper and lead (Fg g-‘) against

aluminium (9) in core C36.

with sand both concentrations decrease. This supports the well known relation of trace metals with

clay minerals.

3.4. Suspended particulate matter

Concentrations of all investigated elements in SPM collected in the estuarine part of the Lena river are given in Table 3. They are in good agreement

with the values given by Martin et al. (1993) for the same area and belong to the lowest concentrations reported for major world rivers. Martin et al. (1993) described the distribution of Cu, Ni, Pb and Zn in relation to Al and POC. Here we present the Cu, Zn,

Fe, Al and Mn concentrations in SPM in relation to

Table 3

Concentration of trace and major elements in suspended matter collected in the estuary of the Lena River (n.d.: not detected)

Station Depth Salinity Cu Cd Ni

(I*g/g) PcLhg/g) (kg/g) ol.g/g)

Zn Mn Ca Mg Fe Al Si

no. (m) (%0) (kg/g) &g/g) (BE) (%o) (%) (%I (%)

1 3 0 26 31 0.14 24 180 840 0.9 0.9 3.3 4.5 23 1 18 0 39 37 I .42 31 217 1234 0.8 1.4 4.9 6.3 34 9 3 0.25 56 45 1.3 80 216 1295 0.9 1.2 5.2 6.2 34

13 3 2.2 90 396 2.47 47 479 1034 0.8 I.1 4.8 5.7 39 15 6.5 3.7 117 239 6.17 24 1982 3183 0.9 0.8 5.6 4.1 63 16 3 0.06 48 59 1.29 25 156 526 0.7 1.4 6.2 7.2 45

23 3 0.8 40 31 0.66 44 156 966 1.2 1.4 4.6 6 32 25 3 2.26 219 29 0.24 17 72 0.5 0.9 3.3 4.8 44

R. F. Nolting rt al. /Marine Chemistp 53 f 1996) 285-299 295

2500 6

2000-

5 1500 D

s

iz IOOO-

i

00. I 0 1 2 3 4 0 1 2 3 4

salinity (% 0 ) salinity (% 0 )

250

200

150 G 3 2

100 :

50

0

Fig. 8. Correlation of Al 0 (81, Fe l (%) and Mn W (pg g-’ ) (left), and Cu 0 and Zn H (kg g-’ ) (right) in suspended matter (SPM)

with salinity in the estuarine part of the Lena River.

salinity (Fig. 8). Concentrations of Fe and Al are rather constant over the small salinity range. On the

other hand the Mn concentration seems to increase with higher salinity. This increase is not surprising,

taken into account the involvement of Mn in the earlier described redox processes that occur in the

sediment. Cu and Zn both show an increase in concentration

from the river to the sea. For Cu this pattern is comparable with that presented by Martin et al.

(1993). However, these authors did not find the high

Table 4

Annual supply of different elements in suspension by the Lena,

RhBne and Rhine rivers. (Rhine: Salomons and Eysink, 1981;

RhGne: Martin et al., 1989; Guieu et al., 1991)

Element

Solid discharge

CU

Pb

Cd

Ni Zn

Mn

Al

Fe

SUPP’Y SUPP’Y ton/year ton/year

Lena river Rhane

17.6~ 10” 4.6~ 10h

460 212

616 446

23 7

422 236

3,168 1,013

14,080 4,273

790,000 318,320

580,000 197,800

SUPPlY ton/year

Rhine river

3.4x IO6

884

1,547

120

391

4,845

Zn concentrations, but it supports their explanation

that Cu-poor river material mixes with Cu-rich marine organic material. However, our limited data set

does not allow to draw significant conclusions.

The annual solid phase discharge of Cu, Pb, Cd, Ni and Zn is low compared to rivers under more

human impact. In Table 4 a comparison with the anthropogenically influenced Rhine and Rh6ne rivers,

for these elements and for Mn, Al and Fe is given. It shows that the supply of trace elements by the Lena River with a high solid discharge is much lower

compared to the Rh6ne and Rhine River with a much lower solid phase discharge.

4. Conclusions

Trace metal concentrations in sediments from the

Laptev Sea are very low and resemble natural background concentrations. Distribution patterns of solid phase Cd, Ni, Cu, Pb and Zn in sediments from the

Laptev Sea, show small increases in concentration from the Lena Delta seaward due to their accumulation in fresh marine organic material. Although, the Cd concentrations are very low compared to other coastal environments, its increase is more pro- nounced than that of the other metals. Mn concentra-

296 R. F. Nolting et al. /Marine Chemistry 53 (I 996) 285-299

tions in the deeper part of the Laptev Sea are higher than those near the river mouth. Remobilization pro-

cesses of Mn and lateral transport of Mn enriched particles from the coastal zone can explain this.

Sediments in the Laptev Sea are of the siliceous

type with low CaCO, concentrations ( N 1%). C/N ratios show that 58% of the organic carbon

in sediment of the river mouth is terrestrial. In the more marine part this content decreases to 36%.

Profiles of solid Cu, Pb, Cd, Ni, Zn and the major elements in sediments from the Laptev Sea do not

show much variation with depth and are indicative

for a rather homogeneous surface sediment. The annual solid discharge of Cu, Pb, Cd, Ni and

Zn by the Lena River is low, compared to rivers

under anthropogenic influences.

Acknowledgements

The Netherlands Marine Research Foundation (SOZ) is acknowledged for the financial support. Rikus Kloosterhuis is thanked for the carbon and nitrogen determinations. The whole group from Rus-

sia, France, Finland, Norway, and the Netherlands is very much thanked for the exciting time we had together. Jean-Marie Martin, the initiator of this

expedition, and Julia Protkova and Artyom Zubkov

did a great job in logistics under very difficult

circumstances. Igor Sidorov is thanked for his support in Tiksi. Remarks by Geert-Jan Brummer im-

proved the manuscript. We are very grateful for the comments of three anonymous referees.

Appendix A. Trace- and major elements results (pg/g and %) in sediments and in pore-water (PM) from the Lena River and Laptev Sea

Boxcore Depth Cu Pb Cd Ni Zn Zn Mn Mn Fe Fe Al Si Mg Ca

(cm) pg/g kg/g rig/g pg/g I*g/g pM kg/g FM % p,M% % % %

c20 0.25 19 21 34 32 108 0.75 19 22 93 32 107 1.25 18 21 73 31 105 1.75 18 22 19 31 104 2.50 19 22 73 32 105 3.50 19 21 136 32 107 5.00 19 22 44 32 107 7.00 19 21 111 31 108 9.00 19 22 106 33 111

c21 0.25 18 16 34 30 100 0.75 18 17 44 31 101 1.25 18 17 110 30 99 1.75 18 17 24 30 102 2.50 18 17 38 30 101 3.50 19 17 58 31 101 5.00 19 17 58 31 106 7.00 19 17 93 31 106

C23 8 14 66 16 56 C24 10 12 53 18 69

c25 0.25 2.1 22 49 33 120 0.75 21 23 173 35 118 1.25 20 22 24 32 120

2.96 2766 0 4.74 3 7.62 27.1 1.37 0.36

7.30 2157 35 4.81 5 7.13 27.1 1.38 0.32 1.68 1373 52 4.84 3 7.37 27.2 1.37 0.35

3.81 873 119 4.90 5 7.22 27.2 1.37 0.38

2.37 752 129 4.92 6 7.28 27.5 1.36 0.33

1.55 618 154 4.70 24 7.28 26.8 1.89 631 174 4.70 50 7.37 26.8

0.79 622 227 4.68 82 7.38 27.0 1.20 596 283 4.65 290 7.33 27.2

1.07 870 74 4.22 4 6.63 26.6 1.68 1159 154 4.32 7 6.58 26.4

1.07 700 108 4.22 4 6.79 26.9 2.44 592 164 4.11 9 6.79 27.4 2.85 486 178 4.14 44 6.75 27.6 0.79 434 143 4.04 54 6.60 27.0 0.79 400 105 4.07 112 7.01 27.9

1

1

.37 0.29

.40 0.28

.36 0.28

.62 0.29

.43 0.98

.40 0.65

.42 0.87

.41 0.64

.41 0.61

.40 0.62

.45 0.51 0.86 411 101 4.03 94 6.82 27.1 1.43 0.63

187 1.92 5.04 32.6 0.54 0.31 272 2.43 5.69 31.8 0.65 0.19

0.58 4921 0 4.98 3 7.63 24.7 1.27 0.26 1.79 4232 6 5.21 3 7.58 25.2 1.32 0.26 0.31 2959 156 5.16 5 7.69 27.7 1.41 01.30

R. F. Nolting et al. /Marine Chemistry 53 (1996) 285-299 297

1.75 19 21 88 31 113 0.58 2960 253 4.91 3 6.85 26.1 1.28 0.36 2.50 20 23 29 33 116 0.51 3330 595 5.20 3 7.20 26.3 1.32 0.28 3.50 20 23 96 33 118 0.24 4154 813 5.20 3 6.99 26.4 1.32 0.25 5.00 19 21 85 30 109 0.04 2409 852 4.73 3 7.06 29.2 1.21 0.29 7.00 20 21 68 32 116 0.78 1923 892 4.97 3 7.18 26.7 1.33 0.34 9.00 20 21 57 32 117 0.44 2246 862 5.05 13 7.3 1 27.5 1.33 0.32

12.00 20 21 71 33 119 0.78 1483 813 4.87 8 7.15 27.4 1.39 0.39 3 4.67 3 6.96 25.3 1.30 0.20

16 4.26 2 6.69 28.3 1.19 0.25

33 4.49 3 6.91 27.5 1.15 0.24

C27 0.25 20 20 46 33 110 0.58 2388

0.75 18 19 38 31 100 0.38 2109

1.25 19 19 24 31 102 0.51 1471

1.75 7 18 33 29 88 0.24 945 83 4.03 14 6.55 28.2 1.03 0.31 2.50 6 17 52 26 82 0.24 493 100 3.58 4 6.41 28.3 0.97 0.54 3.50 5 16 42 26 76 0.11 572 110 3.44 12 6.22 31.4 0.95 0.53 5.00 7 18 38 29 88 0.85 582 153 3.91 44 6.58 29.1 1.06 0.42 7.00 8 17 29 29 95 0.24 575 190 4.05 109 6.54 28.9 1.10 0.43

9.00 7 17 52 28 91 0.71 486 166 3.90 174 6.60 27.5 1.06 0.49

12.00 17 17 33 32 91 0.71 518 170 3.79 104 6.56 27.2 1.00 0.15

C28 0.50 16 20 94 34 113 0.43 5398 674 4.80 6 7.63 26.1 1.37 0.31

1.50 16 19 128 34 113 0.57 3917 664 4.83 6 7.47 25.0 1.34 0.35

2.50 17 20 103 36 115 0.43 3398 654 5.03 20 7.82 26.1 1.41 0.36

3.50 16 20 89 34 108 1.04 2224 417 4.99 64 7.49 25.9 1.38 0.31

5.00 18 20 81 39 109 0.37 3486 486 4.54 58 7.59 23.0 1.23 0.17

7.00 16 19 132 34 111 0.37 3675 615 4.87 50 7.49 24.2 1.38 0.50 9.00 17 21 137 37 114 0.37 2887 615 5.14 13 7.60 26.1 1.43 0.42

12.00 17 20 138 35 111 0.43 1577 496 5.17 45 7.59 26.9 1.39 0.43

C32 0.25 14 16 63 27 96 0.70 1417 3 4.09 3 7.17 29.2 1.29 0.81

0.75 15 17 63 28 98 0.63 1162 53 4.30 3 7.01 28.2 1.36 0.69

1.25 14 16 24 27 97 0.57 622 126 4.08 10 6.93 28.9 1.36 0.65 1.75 16 17 58 28 100 0.90 509 146 4.13 130 7.07 27.5 1.35 0.59 2.50 18 19 38 30 108 0.50 517 160 4.43 301 7.44 26.9 1.45 0.54 3.50 17 18 43 29 106 1.11 525 146 4.39 433 7.27 28.3 1.43 0.62 5.00 14 15 135 26 93 0.30 469 170 3.92 348 6.90 29.9 1.30 0.70

7.00 16 17 53 28 105 0.30 471 183 4.22 106 7.09 28.4 1.42 0.57 9.00 14 15 76 24 91 0.30 435 146 3.82 173 6.76 30.4 1.25 0.64

12.00 16 17 33 29 104 1.24 408 150 3.96 8 7.02 28.9 1.32 0.56

c35 0.25 12 18 67 21 80 0.49 1749 8 3.76 4 6.61 29.1 1.19 0.96

0.75 12 17 29 20 74 1.10 1027 40 3.57 4 6.38 29.4 1.12 1.01 1.25 11 17 61 18 68 0.90 637 69 3.50 4 6.18 29.2 1.11 1.30

1.75 10 17 80 19 70 0.63 434 105 3.28 4 6.16 28.5 1.03 1.04

2.50 10 17 62 16 66 0.49 364 111 3.09 5 6.34 30.7 1.02 1.04 3.50 11 17 66 17 70 1.24 335 89 3.21 9 6.33 29.7 1.08 0.91

5.00 11 18 70 18 74 1.44 338 73 3.47 8 6.32 28.2 1.12 0.86

7.00 12 19 99 18 77 0.63 354 3.74 11 6.56 28.5 1.16 0.87

9.00 12 19 74 18 76 0.56 352 3.64 6 6.71 29.5 1.15 0.97 12.00 12 19 86 17 78 2.25 345 3.68 37 6.41 28.8 1.13 0.81

R.F. Ndting et d/Marine Chrmistrv 53 (1996) 285-299 298

C36 0.25 0.75 1.25 1.75

16 17 48 33 99 0.42 17 18 48 36 106 0.90

18 18 58 36 104 1.03

18 19 50 36 100 0.63

2.50 16 18 90 33 86 1.10

3.50 14 16 100 31 70 1.17

5.00 10 14 38 24 48 0.49 7.00 6 12 62 16 69 0.70

9.00 12 16 47 28 85 0.36

12.00 14 17 52 31 0.70

C38 4 11 33 8 25

01 2 11 122 16 41

02 16 18 65 33 127

03 11 11 68 24 80

04 4 10 34 17 60

05 1 10 19 8 14

09 5 9 63 14 45

13 3 10 54 14 50

15 15 16 128 29 105 16 5 13 59 16 51

23 13 12 142 24 104

25 4 12 73 17 55

27 surf. 16 19 59 30 126 27 > 1 cm 18 18 124 30 134

2128 12 4.36 4 6.90 24.3 1.43 0.62 1646 137 4.59 4 7.00 23.6 1.50 0.61

1240 202 4.64 4 7.03 24.0 1.51 0.63

952 244 4.57 5 6.91 23.8 1.49 0.72

778 206 4.42 4 6.88 24.1 1.47 0.79

510 163 3.94 7 6.75 26.2 1.34 0.92 387 108 3.22 14 6.38 28.6 1.12 1.01

238 56 2.11 47 5.45 27.5 0.77 0.97

324 43 3.48 18 6.49 26.6 1.26 0.85 346 30 3.81 3 6.81 26.4 1.32 0.71 461 1.18 4.95 32.6 0.38 0.40

388 2.15 4.38 31.4 0.56 0.35 905 5.14 6.99 25.9 1.38 0.26

695 2.99 5.56 26.6 0.98 0.57

353 2.18 5.31 31.5 0.75 0.97 41 0.63 2.53 35.3 0.10 0.05

217 1.93 4.43 34.8 0.57 0.32 309 2.09 5.36 30.6 0.67 0.47

481 4.00 6.53 27.5 1.33 0.43 674 1.74 4.67 30.1 0.47 0.43 450 3.24 6.30 30.2 1.25 0.71 603 2.38 4.13 37.0 0.46 0.1 1 602 4.72 7.04 26.6 1.39 0.29 461 4.18 7.13 27.2 1.37 0.24

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