Metal speciation in Jhanji River sediments

ELSEVIER

The Science

of the Total

Environment

193 (1996)

1.~ 12

Metal speciation in Jhanji River sediments N.K. Baruah”,

P. Kotoky”,*,

K.G. Bhattacharyyab,

G.C. Borah”

“Regional Research Lahorutor~~, Jorhar- 785006, Assam. In& “Gauhati Unicersitj,. Guwahafi- 781014. Assam, h&a Received

9 September

1996; accepted

I I September

1996

Abstract The chemical forms of Lead, Zinc, Chromium, Cobalt. Nickel and Copper have been determined using the fractionation scheme of Tessier et al. (1979) and Chao (1972) in the bed sediments of Jhanji River, Assam, India. Almost a similar trend throughout the stretch with no significant spatial variation has been observed in the present study. Significant association with the residual fraction (F5) and a scavenging action by the Fe-Mn oxide fraction (F3b) of the sediments were observed. Except copper, no significant association of other metals with the organic fraction (F4) was observed. Thus, they cannot be easily leached out and may pose less environmental risk. The sediment characteristics played a significant role in defining the chemical forms of the metals present in the sediments. Copyright 0 1996 Elsevier Science B.V. Ke,vwords:

Bioavailability: Heavy metal distribution; Jhanji sediments ; Speciation

1. Introduction

As a result of complex physical, chemical and biological processes a major fraction of trace metals (contributed naturally as well as through various anthropogenic activities) is found to be associated with river’s bottom sediments. The processes and factors that control the scavenging of trace metals by the sediments and their release to the overlying water column must be understood to asses their impact on the environment.

* Corresponding

author

004%9797/96/$15.00 PII SOO48-9697(96)05318-l

Copyright

Q 1996 Elsevier

Science

B.V.

The mobility of the heavy metals in sediments in relation to their chemical forms also controls the environmental impact. The degradation/damage to the natural habitat of the NE-region of India is a very recent attribute. In order to assess the impact, an attempt has been made to evaluate the trace metal distribution pattern with respect to time and space. Chemical speciation of Cr, Cu, Co, Ni, Pb and Zn have been attempted to evaluate its behaviour and remobilization processes. The Jhanji River, bear its origin in Naga Hills and forms a tributary to the Brahmaputra river system of Assam, India. The Jhanji River drains All rights

reserved

N.K. Baruah et al. 1 The Science of’ the Total Environment 193 (1996) l-12

Fig. 1. Locallon map of

tha study area with sampling pdnta

Fig. 1. Location map of the study area with sampling points.

an area of 1350 km2 including both hills and low lying alluvial plains. Out of the total catchment area, about 873 km2 is in the state of Nagaland and the rest 477 km2 is in Assam, India. The basin has a longitudinal extent ranging from 94”15’ E to 94”45’ E and a latitudinal extent of 26”20’ N to 27” N. The river constitutes a major water source for the people residing downstream. The environment of a once tranquil and quietly flowing river is now considered to be destabilised with the tempo of industrialisation and population growth. The river, from which public and industrial waters are abstracted, is also being utilized for the disposal of waste effluents. Apart from effluents of the 100 tonnes/day capacity Tuli Paper Mill commissioned in the year 1971 in Tuli, Nagaland, India, a large variety of agrochemicals and pesticides drained out from the large number of tea gardens around also aggravate the situation. The river Jhanji after flowing into the hilly stretch enters the plains beyond 15 kms of Tuli, Nagaland, a newly built industrial township without proper waste disposal facilities. The foothills part of the river is covered by four large tea gardens which utilises a wide variety of agrochemicals and pesticidies. All the waste goes directly or indirectly

into the river and thus the river is more or less becoming a reservoir of a variety of organic and inorganic chemicals. Such dumping of wastes into the river has been continuing for a long time, resulting in lesser water availability and increasingly expensive pure water supply. Therefore, in order to asses the situation a stretch of 35 km of the Jhanji River starting from Tuli, Nagaland, in a downward direction has been selected for the present study. Studies on heavy metal concentrations and its various chemical forms in a relatively virgin area will contribute to a significant understanding towards its potential for eutrophication and other consequences apart from baseline informations.

2. Experimental The present area of study is covered by the survey of India toposheet No 83 J/l0 (94”15’ E 94”45’ E Long: 26”20’ to 27” N Lat). Considering the accessibility and representativeness in sampling, twelve sites were selected for sediment samples covering a stretch of 35 km in downstream direction (Fig. 1).

N.K. Table I Variation Sample

of geochemical points

pH

Baruah

components Org.

et al. ! The Science

along

matter

Jhanli

river

Carb.

of the Total

basin,

cont.

Environment

193 (1996)

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Assam Pb

Zn

Cu

Ni

co

Cr

Al

Pre-monsoon Wl w2 w3 w4 w5 W6 W7 W8 w9 WlO WI1 w12 Monsoon WI W2 w3 w4 w5 W6 w7 W8 w9 WlO Wll WI2

(March-July) 4.23 4.19 4.66 5.52 4.45 6.33 5.76 4.36 4.84 5.12 4.99 5.32

0.45 0.50 0.27 2.24 2.63 1.96 1.49 1.38 I .27 1.56 1.40 1.38

0.35 0.38 0.35 0.32 0.36 0.28 0.24 0.38 0.41 0.29 0.32 0.36

13.8 13.4 13.2 12.2 12.2 12.7 il.8 11.7 12.1 12.1 13.1 11.6

288.1 155.4 140.7 58.2 52.5 64.2 88.2 90.5 56.0 66.4 36.8 34.4

45.7 45.1 44.3 36.6 36.6 34.2 44.2 34.1 53.3 33.3 52.6 48.0

101.5 98.8 98.0 59.3 59.3 61.1 56.5 57.2 56.0 55.0 50.2 48.4

54.3 52.1 50.5 35.2 35.3 34.3 24.5 25.5 24.2 24.3 22.1 22.1

287.2 62.0 65.6 99.2 55.8 56.7 96.8 56.8 56.5 70.0 55.4 33.6

8.8 8.5 10.4 13.6 11.2 8.2 8.6 8.8 9.5 9.8 8.7 7.5

(July-October) 6.12 6.26 6.15 6.68 6.61 6.45 6.43 6.52 6.32 6.54 6.46 6.50

2.25 2.22 2.48 3.33 3.29 3.22 3.20 3.12 3.09 3.88 3.88 3.80

1.08 1.05 1.07 1.02 1.02 1.01 1.06 1.06 1.08 0.92 0.95 0.84

14.9 16.2 15.4 21.6 19.6 19.9 31.4 30.5 28.9 27.6 21.7 21.4

242.5 247.9 222.3 109.0 121.0 114.0 186.0 184.0 68.1 66.6 88.1 82.2

45.2 45.5 46.6 69.5 68.4 66.6 55.6 54.2 50.2 50.1 55.0 55.5

22.3 20.4 21.5 24.3 24.3 23.4 22.4 22.5 17.5 18.2 22.1 21.6

90.2 90.8 87.5 144.9 89.9 76.6 97.1 82.2 72.2 71.5 78.2 74.4

336.5 338.8 348.2 342.8 333.3 322.6 399.2 392.2 513.8 466.5 259.2 248.2

0.1 0.1 0.1 2.9 2.9 2.9 2.9 2.2 2.2 2.2 2.6 2.5

(November-February) 3.84 0.35 3.81 0.32 3.78 0.18 3.76 1.85 3.80 1.65 3.98 1.22 4.81 1.09 4.63 1.oo 4.20 0.95 4.75 1.00 3.55 0.99 3.53 0.95

0.31 0.28 0.29 0.36 0.24 0.25 0.27 0.32 0.35 0.34 0.40 0.21

9.5 9.6 10.2 10.1 9.6 9.7 9.7 9.5 8.4 9.2 10.1 8.7

139.0 135.2 132.2 43.3 42.5 43.8 72.5 68.2 66.6 52.2 36.4 32.2

40.8 40.2 40.1 28.6 28.5 28.6 38.0 28.0 37.2 26.2 46.1 44.2

92.2 85.5 83.4 54.5 54.6 52.2 48.5 46.2 49.0 45.0 39.0 38.5

44.9 45.2 45.1 25.2 25.3 26.1 19.5 19.5 18.2 18.3 18.5 19.0

265.4 58.0 69.9 89.4 48.8 48.7 76.5 42.2 42.2 64.0 41.2 28.5

6.3 6.5 8.3 8.5 8.6 5.5 5.3 5.3 5.2 5.3 6.8 6.7

Post-monsoon WI W2 w3 w4 w5 W6 W7 W8 w9 WI0 Wll w12 All metals

are in pg/g.

except

Al, Organic

matter

and Carbonate

The samples were collected in pre-monsoon (March-June 1993), monsoon (July-October 1993) and post-monsoon (November 1993 to February 1994) periods. The sediment samples were collected just at the sediment-water interface using a plastic scoop and kept in polythene bags. The samples were air dried and subsequently kept

Content.

which

are expressed

in percentage.

for 1 h at 100°C for removal of water contents associated with the sediments. The dried samples were then ground with agate mortar to below 100 mesh size and were utilised for Teflon Bomb digestion for subsequent analysis following Sakata (1983). The carbonate content of the sediments were determined by the acid neutralisation

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et al. 1 The Science

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method (Jackson, 1958). The organic matter content was determined by the Walkley Black method (Faniran and Areola, 1978). The chemical speciation scheme as proposed by Tessier et al. (1979) and Chao (1972) for partitioning of trace metals into six different fractions was followed. High purity certified/Analar or its eqivalent grade reagents (obtained from Aldrich, Sigma or E Merck only), double distilled deionised water and borosil glasswares (A) were used throughout this work. HNO, and HCl used in this study were purified by a subboiling distillation unit (all quartz). Stock standard solutions of metals were prepared by dissolving ultrapure metals/compounds (99.99% pure) obtained from Aldrich only.

3. Instrumentation Metals (Total) were estimated by AAS with a Perkin Elmer Model-2380 instrument using Parkin-Elmer hollow cathode lamp as light source. Co, Ni, Pb and Cu were estimated by electrothermal atomisation (OF), while Cr and Zn were estimated by flame techniques (FAAS). Matrix matching, standard addition and background correction were used to overcome interferences. The pH of the bed sediments were determined with the help of a portable kit.

4. Results and discussion The sediments of the present study were acidic to about neutral in nature with the pH ranging from 3.5 to 6.7 (Table 1). The pH in post-monsoon and pre-monsoon periods were lower than the monsoon period. The increase in pH in monsoon period might be related with the admixture of a wide variety of sediments during flooding from the catchment area. The pH during premonsoon and postmonsoon periods might be related with the normal soil pH of the region. The carbonate content (Table 1) of the sediment was very low during pre and postmonsoon periods and varied between 0.21 and 0.41%. The low carbonate content of the sediment might be

Environment

193 (1996)

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related with the pH which only permitted the high temperature carbonate to be retained within the system. A minor increase in carbonate content (from 0.84 to 1.07%) during monsoon can be correlated with the higher rate of influx of sediments to the system as a washout added to the river. Almost a similar phenomenon was observed in case of organic matter content also (Table 1). Increase in organic matter content in monsoonal period (from 2.22 to 3.85%) and corresponding increase in downstream direction clearly indicates its influx during the washout from the surrounding areas. The mineralogical study of the sediments shows abundant presence of quartz followed by magnetite, zircon, garnet, tourmaline, epidote, biotite and hornblende (Baruah et al., 1995). No significant variation amongst the detrital bulk mineralogy of the sediment was observed throughout the course of the study. The X-ray diffraction study of the clay fraction ( < 0.39 pm) of the sediment shows the dominant presence of Kaolinite (7.18 A”) with minor amounts of chlorite (7.15 A) and illite (3.34 A). The t-test was applied to determine significant correlation co-efficients between between various pairs of elemental constituents of bed sediments at 5% level of significance (M.= 0.05). The results thus obtained are presented in Table 2. Good correlation between some elements indicate their common source and identical behaviour during transport. Metal/Al ratios which express the relative mobility of the elements can be represented in the following sequence: (1) Premonsoon: Zn > Cr > Ni > Co > Cu > Pb (2) Monsoon: Cr > Zn > Co > Cu > Ni > Pb (3) Postmonsoon: Zn > Cr > Ni > Co > Cu > Pb The graph representing the metalA ratios for the present study are shown in Fig. 2.

5. Speciation profile The geochemical behaviour of the trace metals can be very well evaluated with the speciation studies, which in turn indicate its bioavailability. The metals present in the exchangeable and car-

Mg Pb Zn cu Ni co Cr

Hg Na K Ca

Non-Monsoon Fe 1 Al Mn Cd

Monsoon Fe I Al Mn Cd Hg Na K Ca Mg Pb Zn cu Ni co Cr

Fe

Table 2 Correlation

-0.79 I

- 0.83 I

Al

coefficients

-0.90 0.67 I

-0.96 0.81 1

Mn

for different

-0.90 0.8 I 0.91 I

-0.89 0.81 0.91 1

Cd

heavy

-0.51 0.57 0.44 0.58

0.69 -0.49 -0.77 -0.80 -0.68

0.96 -0.81 ~ 0.96 -0.85 -0.73 1

Na

in bed Sediments

-0.60 0.35 0.72 0.64 1

Hg

metals

0.91 -0.71 -0.92 -0.89 -0.68 0.85 I

0.96 -0.89 -0.96 -0.91 -0.67 0.97

K

Jhanji,

0.36 -0.22 -0.32 -0.37 -0.79 0.71 0.58 1

0.01 0.18 0.15 0.31 -0.13 0.13 -0.03 1

Gil

of the river

0.93 -- 0.69 -0.91 -0.89 -0.68 0.83 0.95 0.54 1

0.99 -0.88 -0.96 -0.92 -0.59 0.96 0.98 -0.05 1

ML!

Assam

-0.61 0.34 0.58 0.35 -0.11 -0.17 -0.36 0.14 ~~ 0.47 1

-0.55 -0.89 -0.54 -0.52 -0.22 0.57 0.68 -0.10 0.63 1

Pb

-0.63 0.37 0.79 0.63 -0.12 -0.46 -0.67 -0.03 -0.54 0.44 1

-0.81 0.69 0.76 0.64 0.29 -0.79 -0.78 -0.11 -0.78 ~~ 0.42 1

Zn

0.17 -0.21 -0.15 -0.24 -0.56 0.22 0.31 0.37 0.03 0.26 0.10 1

0.27 -0.30 -0.12 -0.13 0.57 0.07 0.14 -0.10 0.26 0.10 ~~ 0.47 I

cu

-0.81 0.45 0.87 0.73 -0.03 m-o.51 -0.71 0.01 -0.69 0.70 0.87 0.12 I

0.17 0.16 0.24 0.19 0.58 -0.35 -0.31 -0.13 -0.16 -0.31 0.2 I 0.68 I

Ni

-0.93 0.60 0.91 0.80 0.21 --0.58 -0.83 -0.18 -0.82 0.70 0.81 ---0.23 0.96 1

-0.32 0.23 0.43 0.46 0.75 -0.45 ~ 0.49 0.21 -0.34 -0.15 0.19 0.45 0.55 I

co

-0.45 0.38 0.59 0.47 0.14 -0.33 -0.59 -0.14 -0.42 0.17 0.85 0.07 0.54 0.54 I

-0.09 -0.28 0.05 0.12 0.06 -0.02 0.09 -0.05 -0.05 0.60 -0.13 - 0.25 -0.69 -0.13 1

Cr

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193 (1996)

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-6

10 -I /

0

1

2

3

4

5

Sampling

6

7

8

m/u -aW” L

9101112

0

points

0

.

2

10

SaAplin~

I2

I

-

SaAplinFj

I

I.

I. 10

12

pokts

I 12

poLs

Fig. 2. Variation of metal/Al ratio in the bed sediments of the river Jhanji.

bonate fractions are considered to be weakly bound and may equilibrate with the aqueous phase thus becoming more bioavailable (Gambrel1 et al., 1976; Gibbs (1977); Young and Harvey, 1992)). On the other hand, the metal in the residual fraction is not easily released under normal conditions. The Fe-Mn oxide and organic matter have a scavenging effect and may provide a sink for heavy metals. The release of the metals from this matrix will most likely be affected by the redox potential and pH (Gambrel1 et al., 1976). 5.1. Lead

Distribution of lead throughout the course of study has not shown any significant variation both in time and space (Fig. 3). During premonsoon and postmonsoon periods a slight increase with the organic matter fraction is observed. This might be related with the acidic pH of the sedi-

ments which influences the sorption of lead by organic matter fraction (F4). The speciation scheme (Fig. 4) suggests that the major portion is bound to Fe-Mn oxide fractions [F3(a) and F3(b)]. The prominent presence with the residual fraction (F5) of the sediment with a minor amount of exchangeable (Fl) and carbonate fraction (F2) (in monsoon period) suggest their less bioavailability. Our findings are in good agreement with earlier studies (Tessier et al., 1980, 1985; Salomons and Forstner, 1980; Rauret et al., 1988; Jha et al., 1990 and Ranu Gadh et al., 1993). 5.2. Zinc

Zinc (total) in sediment shows decreasing tendency with space in a downstream direction. The total concentration varies from 32.2 to 288.9 pg (Table 1). Except a minor variation in monsoon it

N.K.

Baruuh

et al. : The Science

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has not shown any significant changes during the course (Fig. 3). The speciation scheme of the zinc (Fig. 5) shows its maximum association with the Mn-oxide fraction [F3(a)] of the sediment and then followed by the Fe-oxide fraction [F3(a)]. An increase in concentration with the organic fraction (F4) is also observed in the monsoon period. Association of a little fraction of zinc is observed with the carbonate (F2) and exchangeable fraction (Fl) of the sediments in monsoon period. An appreciable amount is also associated with the residual fraction (F5) of sediment. These results are in agreement with the known ability of Fee Mn oxides to scavenge zinc from solution and are

‘“-‘jz s

10

OlZJ456789

Sampling

11

12

Points

Pod-monsoon

0123456789

Fig. 3. Variation of heavy of the river Jhanji.

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7

in accordance with those reported by Tessier et al. (1980); Jordao and Hickless (1989); Pardo et al. ( 1990); Nriagu and Coker (1980) and Ranu Gadh et al. (1993).

The chromium content (total) within the sediment fraction varies from 287.2 to 28.5 ,Llg/g in postmonsoon and premonsoon periods (Table 1). However, an increase in total chromium content is observed in monsoon period (513.8 to 248.1 illgig). The chromium content of the present study decreases with distance (Fig. 3). This might be related with the lithogenic influx from the high mineralised belt (Ophiolite rock masses) at the higher reaches and subsequent dispersion/dilution mechanisms associated with the river (Baruah et al., 1995, 1996a,b). The associated higher concentrations during the monsoon period can be attributed as the additional influx from the surrounding areas in the form of washout during heavy flood. The speciation scheme (Fig. 6) of the present study indicates its dominant presence with the residual fraction of the sediment (F5). However, a smaller fraction is also associated with the Fe-oxide [F3(b)] fraction. Sedimentation of the detrital chromium complex via chromite and magnetite has contributed to the chromium content and thereby resulted in the enrichment of chromium in sediments. Fe-Mn oxide grain coatings transport nondetrital-chromium to bottom sediments which in turn also causes enrichment of chromium within them. 5.4. Cohlllt

to:j:: 7
Emironment

11

12

Points

contents

in the bed sediments

With a decreasing tendency in space the cobalt content in the sediment varies from 18.24 to 53.33 jig/g in premonsoon and post monsoon periods (Fig. 3). However, the monsoon period also attended an increasing concentration from 71.5 to 144.9 pg/g (Table 1). The chemical partitioning of cobalt (Fig. 7) indicates its association with the Fe-Mn oxide fraction but the residual (F5) fraction also contain a dominant fraction of cobalt content with it. A

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Fig. 4. Speciation of Pb.

very small fraction ( < 5%) is also associated with the organic matter content of the sediment. 5.5. Nickel

The nickel content in the sediment varies from 17.5 to 101.5 pg/g (Table 1). The nickel content of the sediment goes on decreasing with distance in a downstream direction. This may probably be related to the washout from the high nickel-cobalt bearing rock types in the higher reaches of the area. The partitioning of nickel (Fig. 8) indicates its affinity towards Fe-oxide fraction [F3(b)] of the sediment. A very small fraction is found to be associated with the exchangeable (Fl) and carbonate fraction (F2) of the monsoonal sediments. The dominant presence in the residual fraction (F5) of the sediment indicate its lesser bioavailability. 5.6. Copper

A fluctuating behaviour with an increasing tendency towards downstream in total copper concentration is observed in the present study (Fig. 3). The total copper content varies from 26.1 to 45.7 pg/g in premonsoon and postmonsoon periods.

However, an increasing tendency in monsoon period is observed and varies from 45.2 to 69.5 pg/g (Table 1). Relatively higher pH in the monsoon period may be responsible for this phenomenon helping in retention of higher content of metal in the sediments. Copper is sorbed rapidly to sediments, resulting in high residual level. Rate of sorption varies with the type of clay/sediment, pH, competing cations and the presence of ligands and Fe/Mn oxides. The bar chart (Fig. 9) of the copper speciation shows that it is mainly associated with the Fe-Mn oxide fractions of the sediments but a prominent fraction is associated with the organic matter content also. This is probably due to its high complexing tendency for organic matter, particularly in the monsoon period. The good correlation between the organic matter content and copper fraction associated with the organic matter also indicates its tendency to stay with the organic matter fraction. A major fraction of copper is also found to be associated with the residual fraction. The present study can be correlated with the study of the Jha et al. (1990) on the Yomuna river sediments which show preference for the Fe-Mn oxide fractions. However, the dominant presence

N.K.

Buruah

et al. ,I The Sciewe

of

rhe Totul

Enriromlent

Fig. 5. Speciation

of Zn.

Fig. 6. Speciation

of Cr.

with the residual fraction can be correlated with the study of Tessier et al. (1979) in St. Marcel and Pierrevilla sediments, Gibbs (1977) on Amazon and Yukon River sediment, where the contribution of copper bound to Fe-Mn oxides and or-

19.3 (1996)

l-1-7

9

ganic matter fraction is much lower. A differential behaviour of copper with time and space can be attributed from the present study being either present prominently in the residual (F5) or Fe-Mn oxide/organic fractions (F3(a), F3(B)/F4].

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Fig. 7. Speciaton of Co.

Fig. 8. Speciation of Ni.

6. Conclusion

The sediment characteristics (pH, carbonate content, organic matter and major elements) do not show any prominent variation within pre and

post monsoon periods. However, a change in characteristics are observed in the monsoonal period. This may be related with the washout and flooding of the river with higher amount of suspended sediments.

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Enrironment

IY3 (1996)

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Fig. 9. Speciation of Cu.

The present study of six heavy metals indicate their significant association with the residual fraction (F.5) of the sediments. The Fe-Mn oxide [F3(a)-F3(b)] fractions also scavenge a good portion of metals in them. Except copper, no significant association of other metals with the organic fraction (F4) of the sediment is observed. Probably the acidic nature of soil sediment controls the association of metals within the exchangeable and carbonate fractions. From this, it can be attributed that the different chemical forms of metal ions present within the sediment possess less environmental risk. The sediment characteristics played a significant role in defining the chemical forms of the metals present within the system. Significant correlations observed between the different metal fractions associated within the system help us to get a better understanding of their geochemical cycle and to make a realistic evaluation of their bioavailability. The present study will help to create a data base to implement a continuous geochemical monitoring for a virgin area like ‘The Jhanji River Basin’ Assam, India, considering it as the major source of water for the people

residing downstream and to ascertain its long term effect, which may have not yet been reached.

Acknowledgements

The authors are indebted to Dr. A.C. Ghosh, Director, Regional Research Laboratory, Jorhat, Assam for his kind permission to publish the paper. The author (PK.) thank the Ministry of Environment and Forest, Government of India for financial support (No. 19/91-92/RE) to carry out the study.

References Baruah. J.. P. Kotoky and J.N. Sarma, 1995. Zircons in Jhanji River sediments. Assam Bull. Pure Appl. Sci., 14 (F), 1-2: 35-40. Baruah. N.K., P. Kotoky, K.G. Bhattacharyya and G.C. Borah, 1995. Physico-chemical parameters of River Jhanji, Assam. Indian J. Environ. Prot., 6: 539-543. Baruah, N.K., P. Kotoky, K.G. Bhattacharyya and G.C. Borah, 1996a. Heavy metal distribution in Jhanji River, Assam. Indian J. Environ. Prot., 16, 4: 290-293.

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Baruah, N.K., P. Kotoky, K.G. Bhattacharyya and G.C. Borah, 1996b. Assesment of metal contaminant in sediments of River Jhanji, Assam. Indian. J. Geochem. (in press) Chao, T.T., 1972. Selective dissolution of manganese oxides from soils and sediments with acidified hydroxylamine hydrochloride. Proc. Soil Sci. Sot. Am., 36: 764-768. Faniran, A. and 0. Arcola, 1978. Essentials of Soil Study. Heinemann, London, pp. 273. Gambrell, R.P., R.A. Khalid and W.H. Patrick, 1976. Physicochemical parameters that regulate mobilization and immobilization of toxic heavy metals. In: P.A. Krenkel, J. Harrison and J.C. Burdick (Eds.). Proc. Speciality Conference on Dredging and its Environmental Effects. Am. Sot. Civil. Eng., New York, pp. 4188434. Gibbs, R.J., 1977. Transport phases of transition metals in the Amazon and Yukon rivers. Geol. Sot. Am. Bull., 88: 829-843. Jackson, M.L., 1958. Soil Chemical Analysis. Prentice Hall. Englewood Cliffs, N.J. Jha, P.K., V. Subramanian, R. Sitaswad and Van Grieken, R., 1990. Heavy metal in sediments of the Yamuna river (A tributary of Ganges), India. Sci. Total. Environ., 95: 7-27. Jordao, C.P. and G. Hickless, 1989. Chemical associations of Zn, Cd, Pb and Cu in soils and sediments determined by the sequential extraction technique. Environ. Tech. Let., 10: 7433752. Nriagu, J.O. and R.D. Coker, 1980. Trace metals in humic and fulvic acids from lake Ontario Sediments. Environ. Sci. Tech., 4: 4433446.

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