The elemental chemistry of sediments in the Krishna River basin, India

Chemical Geology, 74 (1989) 331-341

331

Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

[3]

THE ELEMENTAL CHEMISTRY OF SEDIMENTS IN THE KRISHNA RIVER BASIN, INDIA R. R A M E S H 1, V. S U B R A M A N I A N 2'.1, R. VAN G R I E K E N ~ and L. VAN 'T DACK :~ IDepartment of Geological Sciences, McGill University, Montreal, Que. H3A 2A 7 (Canada) ~School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067 (India) :~Chemistry Department, University o[ Antwerp (U.I.A.) B-2610 WiIrijk (Belgium) (Received October 20, 1987; revised and accepted September 6, 1988)

Abstract Ramesh, R., Subramanian, V., van Grieken, R. and Van 't Dack, L., 1989. The elemental chemistry of sediments in the Krishna River basin, India. Chem. Geol., 74: 331-341. Composition of bed, core and suspended sediments collected from Krishna River sediments were studied and the observations are discussed in the light of other Indian rivers, world's average river suspended particles, surficial rock and soils. The contents of V, Cr, Co, Ni, Cu and Zn in the suspended particles are higher in the Krishna River than in the world's average, indicating pollution inputs. Suspended sediments are enriched (5 to 10 times) in all the elements considered relative to bed sediments. Downstream profile and metal/Al ratios of the elements indicate that the mobility of elements within the basin is controlled by basin geology, size and mineralogical characteristics. Good correlations observed for a number of elements point out to their common sink in the clay fraction of the sediments. There is no systematic variation with depth for the major elements and most of the elements are considerably higher compared to estuarine or Bay of Bengal sediments.

1. I n t r o d u c t i o n Rivers supply the bulk of sediments to the world's oceans. Recent estimates indicate that the rivers carry annually 13.5.109 t .2 of sediments (Milliman and Meade, 1983) and 3.25.109 t of dissolved load (Meybeck, 1976). The solid material carried by the rivers to the ocean as a whole is approximately four times more than the dissolved transport. Nevertheless, the chemical composition of river sediments has received less attention in the past. ~lTo whom all correspondence should be sent. "-'1 t = 1 metric tonne-- 10:~kg.

0009-2541/89/$03.50

Martin and Meybeck (1979) estimated the average chemical composition of world rivers based on 20 major rivers. More recently Subramanian et al. (1985) made a first comprehensive attempt to estimate the average chemical composition of river sediments from the Indian sub-continent. On the other hand, the elemental chemistry of individual river basins in India has received less attention, despite some recent preliminary studies (Subramanian et al., 1987; Ramesh and Subramanian, 1987, 1988a,b). In the present paper an attempt has been made to determine the chemical composition of bed, core and suspended sediments in one of the major Indian peninsular rivers - - the Krishna.

© 1989 Elsevier Science Publishers B.V.

332

Knowledge on sediment chemistry on the one hand will help to improve the data base of the global estimates and, on the other hand, it is useful for a better understanding of elemental mobility and fluxes within the basin.

2. T h e K r i s h n a b a s i n

The Krishna basin (13°-19°30'N lat. and 73 ° 23'-80 ° 23' E long. ) covers a drainage area of 258,945 km 2 in the southern part of the Indian sub-continent. The river originates near Mahabaleshwar in the Western Ghats at an elevation of 1337 m above mean sea level and travels 1400 km before flowing into the Bay of Bengal. The basin area includes major geological formations such as Archaean and Younger crystalline rocks (78%), the Tertiary Deccan Traps (20%) and recent alluvial (2%) cover. The Tungabatra and Bhima are the major tributaries. The climate over the basin is primarily semi-arid with average annual rainfall of 500 mm of which 75% occurs during the Southwest Monsoon.

7;6 °

3. M e t h o d o l o g y Fourteen samples of freshly deposited bed sediments were collected along the river as well as tributaries. Due to practical difficulties, only five suspended sediment samples (collected from 5 1 of water with a 0.45-/~m Millipore ® filter) and five core samples have been collected. Fig. 1 shows the flow pattern and sample locations in the river basin. The bed and core sediments were analyzed for SiO~, AI~O:~ and P2()~, by preparing "Solution A", following the procedure of Shapiro and Burnock (1962). Rest of the major elements were determined in solution form by a Perkin Elmer ® atomic absorption spectrometer. To check the accuracy and precision of the measurements, various U.S.G.S. rock standards were analyzed. Repeated measurements for elemental abundances in SDC- I, MAG-1, SCO-1, AGV-1, QLO-1 and G-2 are in satisfactory agreement ('Fable I) _+3% with the reported values (Flanagan, 1976). Minor elements for the suspended and bed sediments were analyzed by X-ray fluorescence technique (XRF). The sediments were processed into thin film prior to analysis. Pow-

8]0 ~

Fig. 1, Locations of the bed-, suspended- and core-sediment sampling stations in the Krishna River basin.

333 TABLE I

Reproducibility of analyzed major elements (published values are from Flanagan, 1976 ) Sample code Mica schist

SDC-I SDC-1 SDC-1

Mean Published value Marine mud

MAG1 MAG1 MAG-

1 Mean Published value Cody shale

SCO-1 SCO-I SCO-I

Mean Published value

Si

Al

P

Sample

30.49 30.53 31.22 30.75 30.75

4.03 4.39 4.02 4.15 4.31

0.091 0.092 0.092 0.092 0.11

Andosite

19.02

4.16

0.098

Quartz

QLO-1

21.64

4.32

0.098

Latite

QLO-I

23.19

4.15

0.098

21.28 23.21

4.21 4.35

0.098 0.1

29.11 29.07 29.07 29.08 28.86

4.02 3.54 4.04 3.87 3.55

0.104 0.111 0.104 0.106 0.128

AGV-1 AGV-1 AGV-1

Mean Published value

Ca

Mg

Na

K

Fe

4.19 4.23 4.23 4.22 4.27

0.99 1.05 1.06 1.03 1.08

3.92 3.91 3.92 3.92 3.86

2.90 2.86 2.85 2.87 2.88

5.13 5.17 5.28 5.19 5.(~9

-

0.67

2.88

0.63

2.91 2.95

QLO-1

-

0.62

Mean

-

0.64 0.60

-

G-2 G-2 G-2

1.37 1.38 1.39 1.38 1.41

0.47 0.45

3.06 3.04 3.02 3.04 3.07

Published value Granite

Mean P u b l i s h e d value

0.46 0.47

2.91 2.98

Mean of triplicates or duplicates (for G - 2 - M g ) analysis. Concentration of elements in wt.%. TABLE II

Analyses (,ug g L) of I.A.E.A. soil-5 standard by XRF

gives observed and recommended values fbr the standard.

Element Average value"

Standard Standard Recommended deviation per deviation on value measurement average

4. R e s u l t s a n d d i s c u s s i o n

Ti V Cr Mn Fe Co Ni Cu Zn Sr Ba

200 15 6 47 2,200

4,810 195 28 908 43,600 30 10 88 379 428 542

1 5 19 12 53

90 7 2 21 980 0 2 9 6 24

4,700 151 28 + 3 852 _+37 44,500 _+1900 15 + 1 13 77 + 5 368 ± 8 330 561 ± 53

"Average of six measurements.

dered sediments were placed on a thin Mylar * foil which was glued on a Teflon ® ring fitting into the X R F sample holders. Details of the thin-film X R F technique have been reported earlier (Van Grieken et al., 1979; Van Dyck and Van Grieken, 1980). A reference soil sample (I.A.E.A. soil 5) was also analyzed and Table II

4. I. Variation in sediment chemistry Table III summarizes the range of values h)r the analyzed major and minor elements in bed, core and suspended samples. With the exception of Ca, Na and K, the ranges of major elements in bed sediments are comparable to those of core sediments. On the other hand, the minor elements of the bed sediments differ drastically from those of suspended sediments. The suspensions are enriched in all the elements considered relative to bed sediments. The suspended sediments are finer, richer in multiplehydroxide coatings, organic matter and tracemetal scavenging clays (FSstner and Wittman, 1981). In addition, the hydraulic conditions, which influence the movement of' bed and suspended material, are different. Hence, the concentrations of minor elements are well outside

334

T A B L E III Range of chemical composition (#g g - ' ) of K r i s h n a River sediments

Si A1 Mg Ca Na K P Fe Mn Ti V Cr Co Ni Cu Zn Sr Ba

Bed

Core

Particulate

186,200-403,900 9,100- 37,800 2,000- 15,900 12,600- 38,900 44,900- 67,000 31,400- 45,000 522- 1,273 5,400- 57,500 140- 2,330 510- 7,290 28375 13315 1583 5117 1127 372 87473 150670

188,000-397,600 9,500- 37,700 1,900- 15,600 3,400- 61,900 90,200-135,300 58,300- 81,700 392- 1,991 n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.

n.a. n.a. n.a. n.a. n.a. n.a. n.a. 92,810-107,284 2,035- 8,630 6,944- 28,300 302- 1,110 108690 180690 71595 69350 888- 2,190 n.a, n.a.

n.a, = not analyzed.

the ranges for the bed sediments. Similar observations have been made for several other major rivers such as the Ganges and Brahmaputra (Subramanian et al., 1987) in India, and the Mississippi in the U.S.A. (Trefry and Presley, 1976). Fig. 2 shows the downstream profile of some of the minor elements in the bed sediments of the Krishna basin. The variations are particularly significant at the confluence of tributaries for all elements considered. The Krishna receives its major tributaries, namely Ghataprabha, Malaprabha, Bhima and Tungabhadra (Fig. 1), at about 500, 535, 700 and 918 kin, respectively, from its source. The tributaries drain a wide variety of geological terrain; for example, the Bhima drains an area of the partially weathered Deccan Traps, a geological setting from which sediment particles can be easily released by physical weathering. One of the tributaries of the Bhima, the river Sina, which has

1,00,000

'~

10.000 Fe

T~

1000 c o

c o

1o0

~o

400

600

800 Distance

1000

1200

Ikm)

Fig. 2. Downstream variation of m i n o r elements in bed sediments of the K r i s h n a River basin.

1400

335

only < 0.1% of the Krishna discharge, contributes 10% of the Krishna total sediment load (Ramesh, 1985). Fig. 3 shows the variation of metal/A1 ratios of bed and suspended sediments in downstream direction. Again, it is seen that the relative mobility of different elements is due to the influence of tributaries. Both size and mineralogy control the elemental composition of riverborne sediments. Detritals such as quartz and feldspars normally are distributed in a wide grain-size spectrum, whereas sheet silicates are dominant in the finer size ranges. Fig. 4 shows an example of mineral variation with grain size in the bed and suspended sediments of the Krishna River.

100

: : ~----X

Bed ISM

1/

..~

,l

: a/AL ~ 4-

2

Fe/Al

Fe/hl

e

--~K-

. . . . . . . . . . . . . . . .

--

-

-~

Zr,/AI

o.011

0-001

0,0001

I

~,00

500

600

700

800

900

1000

1100

1200

1300

1400

Dist once [km )

Fig. 3. Downstream variation of metal/A1 ratios of bed and suspended sediments in the Krishna River basin.

Interelemental correlation was attempted for the observed elements. Fig. 5 illustrates the relationship of A1 with V, Zn, Mg and P for the bed and core sediments. The scatter plot shows positive correlation with A1 (r--0.74), indicating that P is perhaps derived from primary apatite occurring as common accessory in aluminosilicate rocks, or is carried on sorption sites of clays. Most of the major elements show good correlation with each other. For example, A1 correlates with Si ( - 0 . 6 7 ) and Mg (0.87) and Na with K (0.99). Ca, Sr and Ba show nearly similar geographical distributions and interelement associations. Their enrichment in the basin reflects the abundance of carbonate minerals. All transition elements from the entire basin show good interelemental correlations (e.g., Fe-V=0.96; Fe-Ni=0.93; FeZn = 0.99; V-Zn = 0.95; Co-Ni = 0.94). These elements are likely to be present together in the hydroxide coatings on sediment grains. 4.2. Fluxes

Tables IV and V give the annual flux of individual elements for the Krishna basin and its tributaries, together with erosion rates. The sediment fluxes at various stations were calculated using the mean of the 10-yr. annual discharge (Ramesh and Subramanian, 1987 ). The total sediment load of the Krishna River to the Bay of Bengal is estimated to be 4.11-10 ~t yr. - 1. (Ramesh and Subramanian, 1988a). The annual flux of different elements ranged from 8.7 t for Zn to 0.7"106 t for Si. The approximate contribution of different elements by Krishna River sediments to the Bay of Bengal are as follows: Si, 73%; A1, 4%; Na, 10%; K, 7%; Ca, 3%; and Fe, 2%. Rest of the elements contribute < 1% of the total flux. Within the basin the various fluxes and rates indicate a lack of uniformity, primarily due to different sub-basin geology, elevation and various degrees of human impact. The forms of bed sediment distribution, their composition and their physical characteristics

336

T A B L E IV

Average annual fluxes and erosion rates of individual elements in the Krishna River basin Sample

Si

A1

Fe

Mg

Ca

Na

K

Ti

P

No. "1 I "~ *:~

180 18.4

19 3.4

4 0.7

5 1

11 2.2

31 5.7

21 3.9

1 0.2

0.5 0.09

2

2,353 42.7

53 1.0

103 1.9

13 (}.2

96 1.8

326 5.9

225 4.1

23 0.4

3 0.()~

3

2,892 52.4

69 1.3

94 1.7

14 0.3

204 3.7

448 8.1

305 5.5

l0 0.2

4 0.08

4

8,772 27.6

334 2.5

854 6.3

114 0.9

578 4.2

967 7.1

651 4.8

108 0.8

12 0.09

5

3,586 17.0

600 2.9

91 0.4

238 1.1

592 2.8

930 4.4

641 3.0

9 0.l

17 0.08

6

3,897 18.9

289 1.4

92 0.5

55 0.3

225 1.1

612 3.0

420 2.0

14 0.1

14 0.07

7

661 2.6

36 0.1

22 0.1

4 0.02

23 0.1

93 0.4

64 0.3

4 0.02

1 0.0

8

807 3.2

47 0.2

18 0.1

5 0.02

26 0.1

117 0.5

80 0.3

2 0.01

1 0.0

9

183 16.0

8 0.7

48 4.2

2 0.2

22 1.9

51 4.4

34 3.0

1 0.07

1 0.04

10

990 29.8

185 5.6

162 4.9

85 2.6

147 4.4

264 8.0

184 5.5

34 1.01

5 0.16

1I

1,255 17.9

94 1.3

65 1.0

32 0.5

134 1.9

261 3.7

182 2.6

9 0.13

3 0.04

12

160 4.2

6 0.2

18 0.5

1 0.02

5 0.1

21 0.5

14 0.4

3 0.08

0.2 0.01

1,3

314 5.2

16 0.3

10 0.2

2 0.03

20 0.3

45 0.7

31 0.5

1 0.02

0.7 0.01

14

450 6.7

64 1.0

103 1.5

57 0.8

80 1.2

56 0.8

27 0.4

11 0.2

2 0.02

*~Numbers 1-14 correspond to sample locations in Fig. 1. "~Annual sediment flux (10 ~ kg y r . - ~). "~Rate of sediment erosion (t k m - 2 y r . - 1).

may all be used as indicators of the general transport of sediments within a river system. As seen earlier, there is no direct association between the characteristics of suspended and bed sediments for the elements considered. Perhaps, this quantitative sediment flux based on bed sediments can be further improved with

similar studies on suspended sediments throughout the basin. Table VI shows the average concentrations of major and minor elements in Krishna River bed and suspended sediments along with the composition of the major Indian peninsular rivers-the Godavari and Cauvery (Subramanian,

337

TABLE V

Average annual fluxes and erosion rates of individual elements in the Krishna River basin Sample

Mn

V

Cr

Co

Ni

Cu

Zn

Ba

Sr

No. *l 1-2 *:~

1,154 0.21

38 0.01

13 0

7 0

4 0

4 0

3 0

43 0.01

74 0.01

2

4,813 0.09

1,055 0.02

393 0.01

117 0

112 0

135 0

76 0

1,621 0.03

2,700 0.05

3

7,374 0.13

573 0.01

186 0

222 0

115 0

129 0

86 0

2,270 0.04

3,007 0.05

4

9,464 0.14

3,952 0.03

1,783 0.01

1,187 0.01

1,516 0.01

3,343 0.02

3,714 0.03

5

2,360 0.01

472 0

219 0

253 0

101 0

742 0

51 0

4,147 0.02

6,743 0.03

6

2,591 0.01

755 0

338 0

180 0

68 0

90 0

135 0

2,703 0.01

6,984 0.03

7

400 0

113 0

90 0

45 0

14 0

33 0

9 0

412 0

1,165 0

8

407 0

69 0

60 0

41 0

11 0

17 0

21 0

518 0

1,027 0

9

883 0.08

283 0.02

81 0.01

26 0

51 0

96 0.01

54 0

196 0.02

388 0.01

181 0.01

892 0.01

10

9,992 0.3

1,063 0.03

11

2,020 0.03

255 0

319 0

170 0

53 0

5 0

12

436 0.01

93 0

45 0

17 0

22 0

13

281 0

27 0

106 0

19 0

i4

2,811 0.04

149 0

537 0.01

564 0.01

170 0.01

287 0.01

966 0.01

191 0.01

264 0.02

2,115 0.06

3,455 0.1

53 0

1,090 0.02

2,870 0.04

22 0

17 0

82 0

109 0

15 0

3 0

7 0

113 0

255 0

210 0

47 0

115 0

847 0.01

1,039 0.02

*1Numbers 1 - 1 4 correspond to sample locations in Fig. 1. "~Sediment flux (t yr. -1). *:~Erosion rate (t km -2 y r . - 1).

1987 ). Also shown are the published values for the Indian sub-continent (Subramanian et al., 1985 ), sediments from the Bay of Bengal (Sarin et al., 1979) which is the main sink for sediments discharged from the Indian sub-continent; and world's average river sediments (Martin and Meybeck, 1979). In addition, the

average concentrations of Kirshna sediments are compared with the concentration in average surficial rocks (Martin and Meybeck, 1979 ) and soils (Bowen, 1979). The average concentrations of trace metals V, Cr, Co, Ni, Cu and Zn in the Krishna River suspended particles are far in excess of those in

338

TABLE VI

Comparative values of chemical composition of river-borne sediments, continental rocks and soils (elements Si through K in wt.%, all others in #gg 1) Source of sediments "1

Source "~ Si A1 Fe Mg Ca Na K Ti P Mn V Cr Co Ni Cu Zn Sr Ba

Kr-B (n=14) [11 30.43 2.25 2.51 0.65 2.41 5.56 3.82 3,158 774 906 141 82 32 32 35 26 253 439

Kr-p (n=5) [I]

9.83

15,106 5,419 680 336 365 326 155 1,518 -

Go (n-26) [2] 22.00 4.31 5.71 1.37 4.58 1.03 8,640 1,070 297 126 47 51 82 54 233 495

Ca (n=21) [2] 34.60 4.44 1.76 1.10 1.50 1.07 2,950 319 88 129 29 30 12 26 200 444

IA ( n = 128) [31 24.50 5.00 2.90 1.47 2.46 1.21 3,450 605 87 31 37 28 16 217 368

BB (n=12) [4]

7.60 3.90 1.43 1.98

529 84 64 26 120 330

WA (n=10) [5]

WSR

WAS

[51

[61

28.5 9.4 4.8 1.18 2.15 0.71 1.42 4,160 1,150 1,050 170 100 20 90 100 350 150 600

27.50 6.93 3.59 1.64 4.50 1.42 2.44 3,800 610 720 97 97 13 49 32 129 278 445

33.00 7.10 4.00 0.50 1.50 0.50 1.40 5,000 800 1,000 100 70 8 50 30 90 250 500

*lKr-b = Krishna bed sediments; Kr-p = Krishna particulate matter; Go = Godavari; Ca = Cauvery; IA = Indian average; BB = Bay of Bengal sediments; WA = world's average suspended sediments; WSR = world's surface rock; WAS ---world's average soils.

*:'-Sources: [1 ] = present study; [2 ] = Subramanian (1987); [3 ] = Subramanian et al. ( 1985 ); [4 ] = Sarin et al. ( 1979 t; [5] = M a r t i n and Meybeck (1979); [6] = B o w e n (1979).

the world's average river suspended particles. The implication is that the pollution input of these trace metals in the Krishna River is major as compared with natural inputs. Li (1981) discussed the high concentration of trace metals in world's average river suspended sediments being of pollution origin when compared to world's surficial rock and world's average soils. On the other hand, most of the trace metals in the Krishna (bed) and Cauvery and also the Indian average are much closer to those of the world's average soils than those of the world's average suspended particles. The average chemical composition of the Indian rivers

(Krishna, Godavari, Cauvery and Indian average ) in Table VI is based on values for bed sediments. Since analyses of suspended sediments from the Indian rivers are not yet available, the average was computed from chemical analyses of bed sediments only but using the suspended sediment discharge. Such an average does not represent the real situation as seen in the Krishna basin. These values have to be revised after compositions of suspended sediments from all the Indian rivers become available. Ca, Ba and Sr are abundant due to large carbonate concretions in Krishna and Godavari sediments. The Bay of Bengal samples are richer in

339

OetritaLs 100 Suspended sedFments 62~m T 16.~m II <2 ,urn

•

(~

o

~ \

•

50 i ~ •

,

,

,

,

~

~

"~

o 60 ,urn 40~um ~ 20.urn D ~0 .urn ® ,urn

T G ~'0o O: x

,

100 Corbonoles

I

SO

,

i

a

,

\

100 Clay

Fig. 4. Size-related mineralogical variations plotted in a triangular diagram for Krishna River sediments.

Fe and A1 since these sediments are dominated by finer-grained particles. Martin and Meybeck (1979) believe that the geographic variation in major-element concentrations in river suspended sediments can be explained by differences in climate and resultant weathering regimes between river basins. Based on data from 15 major rivers they have stated that Ca and Na concentrations are lower and A1 is higher in tropical river suspended sediments. The world's average was computed with a very limited number of samples. For example, they have considered only two samples from the large sediment load of Asian rivers and hence the suspended sediment chemistry is not matching with those of Indian rivers.

4.3. Composition of core sediments

Table VII summarizes the vertical distribution of different major elements obtained for core sediments. For comparison are shown also the published values for the clay fractions of the Godavari delta core (Kalesha et al., 1980), a core from the Bay of Bengal (Sarin et al., 1979), deep-sea clays (Chester, 1965; Chester and Aston, 1976) and from an Arabian Sea core (Borole et al., 1982 ). In all the cores considered, Ca and Mg show positive correlation to each other (r = 0.80 ) but negative correlation ( - 0.82 and -0.98, respectively) with Si. K and Na show positive correlation (r= 0.98) with each other.

340 TABLE VII Major-element concentrations of the five cores from the Krishna River basin (/lg g - 1)

Core (location)

Depth

Si

A1

Mg

Ca

Na

K

P

(cm) Krishna (Kolhar)

0-6 6-12 12-18 18-24 24-30

193,500 196,200 167,800 341,100 342,000

37,900 37,700 36,000 9,500 12,300

14,500 14,500 14,400 2,900 3,100

36,800 30,300 40,000 29,000 30,800

126,600 114,600 118,000 121,400 111,800

77,600 71,000 73,300 75,800 70,700

1,044 1,044 978 392 424

Krishna (Raichur)

0-6 6-12 12-18 18-24 24-30

188,000 229,200 270,500 300,800 290,700

30,700 27,600 26,500 27,100 26,800

15,600 12,000 9,100 6,800 6,400

47,400 61,900 39,100 35,400 42,200

101,600 109,400 113,900 135,300 118,100

64,500 69,100 73,500 81,700 73,400

424 457 620 685 1,371

Krishna (Vijayawada)

0-6 6-12 12-18 18-24 24-30

366,800 376,000 380,500 364,900 378,700

26,500 28,900 26,400 27,900 27,700

2,800 2,100 2,300 2,500 2,100

6,000 6,100 4,700 4,800 5,700

118,200 113,300 125,200 109,700 115,000

73,800 71,600 77,900 71,600 72,200

718 457 489 522 587

Krishna (Rapalle)

0-6 6-12 12-18 18-24 24-30

347,500 365,900 358,500 364,100 372,300

29,500 32,700 32,400 32,100 29,000

4,900 4,600 3,600 4,500 3,500

15,200 26,300 10,700 14,600 11,000

107,000 110,300 122,700 108,100 115,800

67,400 68,500 78,500 67,600 71,700

848 620 751 946 978

Tungabhadra (Hospet)

0-6 6-12 12-18 18-24 24-30

397,600 348,500 362,100 379,900 368,700

19,400 24,000 19,400 21,200 18,900

2,400 2,500 3,000 1,900 2,600

3,800 3,400 4,100 4,100 7,300

102,500 115,300 111,900 90,200 111,100

65,500 73,900 70,200 58,300 69,000

751 718 783 1,044 1,991

322,072 -

26,724 121,100 81,000 84,000 31,136

5,784 20,800 16,000 15,000 -

20,828 11,200 47,000 7,000 -

113,880 9,100 11,000

71,532 19,200

786

Mean Godavari delta core [1 ] Bay of Bengal core [2] Deep-sea clays [3] Arabian Sea core [4]

19,000

Re[erences: [1] =Kalesha et al. (1980); [2] =Sarin et al. (1979); [3] =Chester {1965) and Chester and Aston (1976); [4] =Borole et al. (1982).

The relationship between Ca and Mg on the one hand and Si on the other hand can be explained by the presence of a higher proportion of carbonates in the upper portions of the core relative to detrital-like quartz (Ramesh, 1985). Similarly, the increase in A1 concentration vertically in the upstream (core 1 ) and midstream (core 2) regions can be accounted for by a corresponding increase in clay minerals (Ramesh,

1985). The composition of most of the major elements considered in this study is high compared to the sediments from the Godavari delta, Bay of Bengal and deep-sea clays. In the Gulf of Combay, on the western region of India which has the same climatic regime as the Krishna basin, a similar high composition has been reported compared to deltaic and deep-sea clays (Borole et al., 1982).

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Fig. 5. Scatter diagram of the concentration of V, Zn, Mg and P vs. A1 in the Krishna River bed and core sediments.

References Borole, D.V., Sarin, M.M. and Somayajulu, M., 1982. Composition of Narmada and Tapti estuarine particles. Ind. J. Mar. Sci., 11: 51-62. Bowen, H.J.M., 1979. Environmental Chemistry of the Elements. Academic Press, London, 333 pp. Chester, R., 1965. Elemental geochemistry of deep sea sediments. In: J.P. Riley and G. Skirrow {Editors), Chemical Oceanography, 2. Academic Press, London, pp. 3480. Chester, R. and Aston, S.R., 1976. The geochemistry of deep sea sediments. In: J.P. Riley and R. Chester (Editors), Chemical Oceanography, 6. Academic Press, London, pp. 281-390. Flanagan, F.J., 1976. Description and analyses of eight new USGS rock standards. U.S. Geol. Surv., Prof. Pap., 840: 192-220. Fostner, U. and Wittmann, G.T.W., 1981. Metal Pollution in the Aquatic Environment. Springer, Berlin, 486 pp. Kalesha, M., Rao, K.S. and Somayajulu, B.L.K., 1980. Deposition rates in Godavari delta. Mar. Geol., 34: M57M66.

Li, Y.H., 1981. Geochemical cycles of elements and human perturbation. Geochim. Cosmochim. Acta, 46: 20732084. Martin, J.M. and Meybeck, M., 1979. Elemental mass-balance of material carried by major world rivers. Mar. Chem., 7: 173-206. Meybeck, M., 1976. Total dissolved transport by world major rivers. Hydrol. Sci. Bull., 21: 265-289. Meybeck, M., 1987. Global chemical weathering of surficial rocks estimated from river dissolved loads. Am. J. Sci., 287: 401-428. Milliman, J.D. and Meade, R.H., 1983. World-wide delivery of river sediment to the oceans. J. Geol., 9: 1-19. Ramesh, R., 1985. Geochemistry of Krishna river basin. Ph.D. Thesis, Jawaharlal Nehru University, New Delhi, 228 pp. Ramesh, R. and Subramanian, V., 1987, Heavy metal content in the sediments of major peninsular rivers of southern India. Proc. Int. Conf. on Heavy Metals in the Environment, New Orleans, La., Sept. 15-18, 1987. Ramesh, R. and Subramanian, V., 1988a. Temporal, spatial and size variation in the sediment transport in the Krishna river basin, India. J. Hydrol., 98: 53-65. Ramesh, R. and Subramanian, V., 1988b. Nature of the dissolved load of the Krishna river basin, India. J. Hydrol., 103: 139-155. Sarin, M.M., Borole, D.V. and Krishnaswamy, S., 1979. Geochemistry and geochronology of sediments from the Bay of Bengal and the equatorial Indian Ocean. Proc. Ind. Acad. Sci., 88: 131-154. Shapiro, L. and Burnock, W.W., 1962. Rapid analyses of silicate, carbonate and phosphate rocks. U.S. Geol. Surv., Bull. No. 1144, 56 pp. Subramanian, V., 1987. Environmental geochemistry of Indian River basins - - a review. J. Geol. Soc. India, 29: 205-220. Subramanian, V., Van 't Dack, L. and Van Grieken, R., 1985. Chemical composition of river sediments from the Indian subcontinent. Chem. Geol., 48: 271-279. Subramanian, V., Van Grieken, R. and Van 't Dack, L., 1987. Heavy metals distribution in the sediments of Ganges and Brahmaputra rivers. Environ. Geol. Water Sci., 9: 93-103. Trefry, J.H. and Presley, B.J., 1976. Heavy metal transport from the Mississippi river to the Gulf of Mexico. In: H.L. Windom and R.A. Duce (Editors), Marine Pollutant Transfer. Lexington Books, Lexington, Mass., pp. 39-76. Van Dyck, P. and Van Grieken, R., 1980. Absorption correction via scattered radiation in energy-dispersive Xray fluorescence analyses for samples of variable composition and thickness. Anal. Chem., 52: 1859-1864. Van Grieken, R., Van 't Dack, L., Coster Dantas, C. and da Silveria Dantas, H., 1979. Thin film and X-ray fluorescence technique. Anal. Chem. Acta, 108: 93-101.