13

CHAPTER - 2

STUDY AREA AND METHODOLOGY

Chapter-2

14

2.1. STUDY AREA

Swarna river basin which covers the western part of Western Ghats forms the area of

interest for this study (Fig. 2.1.a). The Swarna basin forms the wettest part of the Western

Ghats located in coastal Karnataka. In addition, a comparative study is carried out at

various stages with the adjacent basins of Madisal River (Fig. 2.1.a), Nethravati-Gurupur

rivers (Fig. 2.1.b), Seetha River (Fig. 2.1.c), Gangolli River (Fig. 2.1.d) and few places

along the western and eastern parts of the Western Ghats (Fig. 2.1.e). Swarna, Madisal,

Seetha and Gangolli rivers flow in the Udupi district and Nethravati and Gurupur rivers

flow in the Dakshina Kannada district of Karnataka, Southern India.

The Swarna River originates at Korankal Gudda in the Western Ghats at an altitude of

1100 m above mean sea level (msl). It flows north-westerly from the origin for about 80

km to join Madisal and Seetha rivers near the coast. These rivers finally discharge together

into the Arabian Sea at Kodi Bengre near Hangarkatte (Udupi), Karnataka. The Swarna

basin covers an area of 603 km2 experiencing high annual rainfall of about 5000 mm, and

has an average discharge of 55 m3 s-1 (June 2010 - May 2012; Central Water Commission).

The monthly rainfall, water temperature and discharge in the basin for the study period

between August 2010 and August 2012 are given in Fig. 2.2. The Swarna basin is

surrounded by Madisal-Seetha rivers in the north, Western Ghats (with Tunga-Bhadra

rivers) in the east, Gurupur river in the south-east, Udyavara river in the south and Arabian

Sea in the west. The major tributaries are Happanadka hole, Durga hole, Andar hole and

Kada hole. The basin is located on the southwestern part of the Western Dharwar Craton

underlain with metamorphic transition zone represented by green schist facies to granulite

facies rock types, such as greenstones, gneiss and granulites of Precambrian age and the

Tertiary to Quaternary laterites (Rogers et al. 1986).

Madisal River originates at an altitude of 720 m above msl near Durga Gudda in the

Western Ghats and flows south westerly for about 60 km to join Swarna River at

Kallianpur and finally discharge into Arabian Sea at Kodi-Bengre, Udupi. The basin has an

area of about 280 km2 and experiences annual rainfall of about 4500 mm. The major

tributaries are Mathebettu hole and Jarvattu hole. The lithology is covered by schist,

gneiss, granite and laterite.

Cha

pter

-2

15

F

igur

e 2.

1.a:

Bas

in m

ap o

f S

war

na R

iver

, Sou

thw

est c

oast

of

Indi

a sh

owin

g sa

mpl

ing

stat

ions

.

Chapter-2

16

Nethravati River originates in the Western Ghats at an altitude of about 1100 m above msl

at Gangamoola near Samse of Chickamagalore district. The Gurupur River flows for about

80 km and then joins the Nethravati River (147 km) to form a common estuary before

discharging into Arabian Sea at Mangalore. The Nethravati and Gurupur basins cover total

area of 3657 km2 and 824 km2 respectively, and form the major water source of domestic,

agricultural and industrial purposes of Dakshina Kannada district. The basin experiences

average annual rainfall of about 4000 mm. The major tributaries of Nethravati River are

Kumaradhara, Gundiya hole, Shishila hole, Neriya hole and Mundaje hole.

Figure 2.1.b: Basin map of the Nethravati-Gurupur River, Southwest coast of India

showing sampling stations.

Seetha River originates in the Western Ghats at an altitude of 980 m above msl at Kutrikal

Gudda. It flows southwesterly from the origin for about 82 km and then joins Swarna-

Madisal River near Hangarkatte and finally flow together into Arabian Sea at Kodi-

Bengre, Udupi. The basin receives higher rainfall of about 4500 mm annually. The major

tributaries of Seetha River are Goli hole, Honakal halla, Kollangar hole, Koodluthirtha

hole, Nemar hole and Achladi hole.

Chapter-2

17

Figure 2.1.c: Basin map of the Seetha River, Southwest coast of India showing sampling

stations.

Gangolli River originates at high altitudes of Western Ghats and flows into Arabian Sea at

Gangolli near Kundapur, Udupi. The Gangolli composite basin receives about 4000 mm of

annual rainfall with the area experiencing the average temperature of 32°C. The basin is

surrounded by Byndoor River in the north, Western Ghats in the east, Seetha-Swarna

rivers in the south and Arabian Sea in the west. The Gangolli river basin is a composite of

three major sub-watersheds of Halady, Chakra and Kollur rivers. The Halady, Chakra and

Souparnika (Kollur) rivers originate at an altitude of 760 m above msl at Kavari, 820 m

above msl near Kattinahole and 1100 m above msl at Kodachadri, Kollur respectively, in

Western Ghats. Halady River flows northwesterly from the origin for about 83 km,

whereas the Chakra and Kollur rivers flow southwesterly for about 68 km and 70 km

respectively to join together near Kundapur and finally flow as Gangolli River to discharge

into the Arabian Sea. The major tributaries of Haladi River are Varahi, Dasanakatte and

Kubja rivers. The tributaries of Chakra River include Savehaklu hole and Kattina hole

whereas Kollur River has Halkal hole, Jadkal hole and Souparnika hole as its major

tributaries.

Chapter-2

18

Figure 2.1.d: Basin map of the Gangolli River, Southwest coast of India showing sampling

stations.

Chapter-2

19

Figure 2.1.e: Base map showing sampling locations (stations for stable isotope study) in

the Western Ghats and its western and eastern parts along the Southern India.

Chapter-2

20

Au

g-1

0S

ep-1

0O

ct-1

0N

ov-

10D

ec-1

0Ja

n-1

1F

eb-1

1M

ar-

11A

pr-

11M

ay-

11Ju

n-1

1Ju

l-11

Au

g-1

1S

ep-1

1O

ct-1

1N

ov-

11D

ec-1

1Ja

n-1

2F

eb-1

2M

ar-

12A

pr-

12M

ay-

12Ju

n-1

2Ju

l-12

Au

g-1

2

Rai

nfa

ll (

mm

)

0

200

400

600

800

1000

1200

1400

1600

Dis

char

ge

(m3

s-1)

0

50

100

150

200

250T

emp

erat

ure

(°C

)

24

26

28

30

32

34Rainfall Discharge Temperature

Figure 2.2.a: Monthly rainfall, discharge and temperature in the Swarna basin for the study period.

Figure 2.2.b: Monthly rainfall in the Swarna basin at different gauging stations for the last five years from January 2009 to December 2013.

Chapter-2

21

Swarna estuary

The Swarna River joins the Arabian Sea at Kodi-Bengre near Hangarkatte, Udupi. It is the

region of confluence of three rivers - Swarna, Madisal and Seetha. The Swarna estuarine

region is shown in Fig. 2.3. The Swarna river channel in the estuarine region is shallow,

and is controlled both by freshwater and saline water depending largely on the season and

the tidal cycle. The tidal influence is observed till the downstream of Baje dam during the

pre-monsoon season. The saline water reaches the Santhekatte region during the

monsoonal season. The landforms in the Swarna estuary include the long barrier spit in the

west extending from Hude to Kodi-Bengre, lagoon in the north and small braided islands

in the estuarine channel. The estuarine region supports mangrove vegetation of various

species belonging to Rhizophora, Avicennia, Sonneratia and Acanthus (Radhakrishna and

Vaidyanadhan, 1997).

Figure 2.3: Base map of Swarna estuary, Southwest coast of India showing sampling

stations along the salinity gradient during the three sampling seasons.

2.1.1. General characteristics of study area

The study area shows the characteristic features of the Western Ghats. The densely

vegetated Western Ghats (1600 km) hosts a narrow tropical coastal zone, 40 to 75 km wide

Chapter-2

22

on the west. It forms a successive edge of the Deccan Plateau towards the north-east. The

Ghats escarpment (1300 to 1800 m) plays the role of an orographic barrier blocking bulk

of the southwest monsoon rainfall along the Sahyadri range. The second highest amount of

annual rainfall (7500 mm) has been recorded at Agumbe (645m above msl), Karnataka,

famous for its rainforest, a biodiversity hotspot. The annual rainfall decreases abruptly to

4500 mm and 4000 mm as it reaches the western coastal region of Udupi and Mangalore

respectively. There is a strong variability of rainfall in this region. Based on the rainfall

variability, the seasons are classified as monsoon (June to mid October), post-monsoon

(mid October to January) and pre-monsoon (February to May) seasons. During the period

between February to May, preceding the southwest monsoon, the region experiences dry

conditions and hot temperatures, with mean temperature over 30°C. Between March and

May, the potential evapo-transpiration gradually increases and can reach 240 mm/month

(James and Pradeepkumar, 1987). The presence of highly undulating terrains and heavy

rainfall have resulted in the origin of several short rivers with high surface runoff.

Contrary to the northern part of the Western Ghats like the Deccan traps, there is no

volcanic rock in the study area except for a small patch of land in the Arabian Sea (St

Mary’s Islands), with its famous polygonal columnar basalt formation. The geological

formations of the study area consist of Archean complex made up of Dharwar schists and

granitic gneisses. The Ghats mainly comprises of schist, whereas the gneiss, granites and

charnockite rocks cover the lower undulated landscapes with sandy alluvium along the

coast. The morpho-climatic settings explain the distribution of vegetation and soils. For

soils, a schematic toposequence includes plinthosols (IUSS working group, 2006) in the

coastal area, acrisols and lixisols associated with a few ferralsols on the humid slopes of

Western Ghats. Human activities, particularly agricultural practices, strongly depend on

these pedo-climatic conditions. In summary, the coastal area appears as a mosaic of highly

diverse and contrasting landscape units and thus covers the main vegetation types and

major soil–crop–climate complexes of Southern India (Seen et al. 2010).

On the slope of the Western Ghats, the tropical rain forests undergo strong seasonal

climate change, with long dry and cold period in winter. These severe conditions lead to

lesser diversity of the big trees. It is compensated by high nutrient soils (Swamy and

Proctor, 1994). The hilly tract of the Western Ghats in Karnataka is famous for its

arecanut, coffee and spice orchards from several centuries. The cultivators use intense

application of tree leaves as mulch, and of leaf-mold and dung as manure, materials that

Chapter-2

23

are obtained directly or indirectly from the forest surrounding the orchards (Lélé, 1993).

The other crops are rubber plantations, paddy (rice) cultivation in the valley, different

legumes and coconuts along the coast. The land use/ land cover change has led to the loss

of biodiversity, which lowers ecosystem's resilience to environmental stresses and

decreases their ability to remove carbon from the atmosphere. More directly, it often leads

to the release of carbon from terrestrial ecosystems into the atmosphere.

2.1.2. Geological aspects

The geological characteristics in Indian scenario are well defined on the basis of the

tectonic divisions of the Precambrian Shield into Archean cratons and Proterozoic mobile

belts following the South African geological divisions explained by Anhaeusser et al.

(1969). Depending on the differences in lithology, age, structure, metamorphism and

geochemistry, the Indian Shield is classified into five geological cratons namely Dharwar,

Bastar, Singhbhum, Bundelkhand and Aravalli which are surrounded by three prominent

mobile belts like Pandyan, Eastern Ghats and Satpura mobile belts (Fig. 2.4). Also, the

Himalayan orogenic belt which is a tertiary mountain belt of Proterozoic foundation covers

the Indian Shield in the north (Ramakrishnan and Vaidyanadhan, 2008). Apart from these

cratons and mobile belts, the Indian Shield includes the younger cover such as the

Proterozoic sedimentary basins (Purana basins), the Deccan trap (Deccan Volcanic

Province) which is a vast flood basalt province at the Cretaceous-Tertiary boundary (K-T

boundary) in western and central India with its outlier at Rajahmundry in southern India,

the Rajmahal trap in eastern India, the coal bearing Gondwana successions in Damodar,

Satpura, Mahanadi and Godavari rifts, the Cretaceous marine incursions in Narmada valley

and at Tiruchirapalli in the Cauvery delta, the coastal Gondwana, Tertiary and Quaternary

sediments with local volcanics, the Holocene (recent) sediments along major river valleys,

Tertiary and Quaternary sediments at the Himalayan foothills and in Indo-Gangetic and

Brahmaputra plains (including the Bengal fan) and the Phanerozoic successions in the

Himalaya (Ramakrishnan and Vaidyanadhan, 2008).

Chapter-2

24

Figure 2.4: Tectonic divisions of the Indian Shield (after Ramakrishnan and Vaidyanadhan, 2008).

2.1.2.1. Geology of Southern India

Southern India (Peninsular India) is mainly characterized by Archean Dharwar Craton and

the Pandyan mobile belt. The Pandyan mobile belt is also known as the Southern Granulite

Terrain; however the latter terminology was found to be ambiguous as it included both the

Archean and the Neoproterozoic granulites (Vemban et al. 1977; Drury et al. 1984).

Ramakrishnan (1988, 1993) redefined the Pandyan mobile belt as the granulite terrain

occurring to the south of Palghat-Cauvery Shear Zone (PCSZ) whereas the granulite

terrain situated to the north of the PCSZ belonged to the Dharwar Craton. The Archean

Dharwar Craton covers the major part (~0.45 million sq. km) of Peninsular India

consisting of greenstone/ schist belts, grey gneisses, charnockites and younger granites.

The classical greenstone-granite terrain of Dharwar carton was divided into two tectonic

blocks after Swaminath et al. 1976, namely Western block and Eastern block which was

later renamed as Western Dharwar Craton (WDC) and Eastern Dharwar Craton (EDC) by

Rogers, 1986. The two were separated by the Chitradurga Shear Zone which is located at

Chapter-2

25

the eastern margin of Chitradurga schist belt, and close to the western margin of Closepet

Granite of age 2513±5 Ma (Friend and Nutman, 1991). The WDC mainly comprises of the

grey gneiss which is well known as the Peninsular Gneiss (>3000 Ma) whereas the

dominant granitic terrain (2700-2500 Ma dated via SHRIMP U-Pb measurements; Friend

and Nutman, 1991) also known as Dharwar Batholith, after Chadwick et al. 2000, covered

the major part of EDC. The characteristic features of WDC include the large Dharwar

schist belts with volcanics and subordinates, the Peninsular Gneiss (>3 Ga) basement

having angular unconformity with the Dharwar marked by quartz-pebble-conglomerate

(QPC) – the basement gneiss inliers within schist belts, the three fold succession: (i) basal-

arenite-banded iron ore formation (BIF), (ii) shelf facies at the margin and homotaxial

pillowed basalt-BIF in deeper waters, (iii) greywackes-BIF-volcanics, the older sequence

(Sargur group) as narrow belts and enclaves, abundant in the south, the intermediate

pressure (kyanite-sillimanite type) metamorphism (Ramakrishnan and Vaidyanadhan,

2008). The EDC is characterized by the narrow Dharwar greenstone belts with dominant

pillowed basalts, the Dharwar Batholith (2.5-2.7 Ga) intrusive on all sides – common

diapiric gneiss domes, the three fold successions: (i) shelf sediments disrupted into screens

at the belt margins, (ii) pillowed volcanic, greywackes, BIF, (iii) felsic volcanics,

volcanogenic conglomerate (Champion Gneiss), the older sequence of Warangal group

mostly as enclaves in the northeast, and Salem group in the south, the low pressure

(andalusite-sillimanite type) metamorphism (Ramakrishnan and Vaidyanadhan, 2008).

2.1.2.2. Geology of study area

The study area lies on the southwestern part of Western Dharwar Craton comprising

mainly of Precambrian (Archean) Peninsular Gneiss, the Western Ghats Belt of

Bababudan group of Dharwar super group, Phanerozoic laterite and the more recent

alluvium. The regional stratigraphy of WDC is given in Table 2.1.

Peninsular Gneiss: The three crustal accretion events namely at 3.3-3.4 Ga, 3-3.1 Ga and

2.5-2.6 Ga explain the Peninsular Gneiss present in the WDC. The second event was more

pronounced and widespread whereas the first and the third were sporadic. Peninsular

gneiss consists of multiple migmatites of tonalite-trondhjemite-granodiorite (TTG)

composition and homophonous trondhjemite to granodiorite plutons intrusive into

migmatites. The lack of rounded zircons, low chromium content and no normative

Chapter-2

26

corundum show that the gneisses have very little sedimentary contribution. The TTG

gneiss depict the typical calc-alkaline differentiation trend which are believed to have

formed by the partial melting of a mafic source in the deep crust, together with melting of

pre-existing crust, accompanied by metasomatism of lithophile elements around 3 Ga. This

has resulted in the depletion of heat-producing elements in the crust, which caused the

sporadic incidence of granitic magmatism at 2.6 Ga (Radhakrishna and Vaidyanadhan,

1997; Ramakrishnan and Vaidyanadhan, 2008).

Western Ghats Belt: It is a large schist belt extending from Kudremukh in the south to Jog

Falls in the north through Agumbe and Kodachadri peaks covering a total area of about

2200 sq. km. The basal bed of oligomict quartz-pebble-conglomerate (Walkunji

Conglomerate) with associated cross-bedded quartzite (7 m thick) extending intermittently

along the western margin for about 130 km overlie unconformably the basement gneiss.

This conglomerate consists of marginal grade uranium. The conglomerate-quartzite bed is

overlain by a thick pile of amygdular metabasalts with rare agglomerates, interbeds of

quartzite, phyllites and minor BIF. Geochemically, the metabasalts are similar to

Bababudan lavas which show lower heavy rare earth elements (HREE) and moderate light

rare earth element (LREE) enrichment indicating the mantle source enriched in lithophile

elements. The ultramafic schist occurring within basalt, similar to that of Santaveri

formation of Bababudan group, forms the prominent horizon. A major unit of Algoma-

type BIF covers the Kudremukh and Kodachadri regions. The iron formation in the region

belongs to oxide and silicate facies, but rarely has carbonate facies. The iron formations

show enrichment of La, positive Eu anomalies and depleted REE suggesting the

hydrothermal contribution whereas the enrichment of K, Al, Zr and Rb in shaly BIF

suggests continental source. The major horizon of basalts, chloritic phyllites, felsic

volcanics and pyroclastics overlies the BIF and are typically exposed in the

Narasimhaparvatha which correspond to the Jaggar formation of Bababudan belt

(Radhakrishna and Vaidyanadhan, 1997; Ramakrishnan and Vaidyanadhan, 2008).

Cha

pter

-2

27

Tab

le 2

.1: R

egio

nal s

trat

igra

phy

of W

DC

(af

ter

Sw

amin

ath

and

Ram

kris

hnan

, 198

1; R

amak

rish

nan

and

Vai

dyan

adha

n, 2

008)

.

DH

AR

WA

R

SU

PE

RG

RO

UP

(3

.1-3

.3 G

a)

Pro

tero

zoic

maf

ic d

ykes

C

harn

ocki

tes

(250

0-26

00 M

a)

You

nger

gra

nite

s (2

600

Ma)

Chi

trad

urga

G

roup

Van

ivila

s S

ubgr

oup

Maf

ic-f

elsi

c vo

lcan

ic w

ith

BIF

, phy

llit

es (

basi

n ce

nter

) M

anga

nese

an

d ir

on

form

atio

ns,

stro

mat

oliti

c ca

rbon

ates

, bi

ogen

ic

cher

ts,

peli

tes,

qu

artz

ites

an

d po

lym

ict c

ongl

omer

ates

(ba

sin

mar

gin)

Ran

iben

nur

Sub

grou

p G

reyw

acke

s w

ith

BIF

, pol

ymic

t con

glom

erat

e, m

afic

-fel

sic

volc

anic

s

Tal

ya/

Kal

durg

a co

nglo

mer

ate

= M

etab

asal

ts a

nd s

ilice

ous

phyl

lites

of

Jaga

r va

lley

Dis

conf

orm

ity

Bab

abud

an

Gro

up

BIF

with

phy

llite

s an

d ra

re u

ltra

maf

ic-m

afic

sil

ls

Mul

laya

nagi

riF

orm

atio

n

Met

abas

alts

, fe

lsic

vol

cani

c (G

alip

uje

fels

ites

), u

ltra

maf

ic s

chis

ts,

laye

red

basi

c co

mpl

exes

, sil

iceo

us p

hyll

ites

, cro

ss-b

edde

d qu

artz

ite

(Kai

mar

a, T

anig

ebai

l)

San

tave

ri

For

mat

ion

Met

abas

alts

, ga

bbro

s,

ultr

amaf

ic

schi

sts,

lo

cal

BIF

, ph

ylli

tes,

cr

oss-

bedd

ed

quar

tzit

e (L

akya

) A

llam

pura

F

orm

atio

n

Met

abas

alts

, ga

bbro

s,

ultr

amaf

ic

schi

sts,

ph

ylli

tes,

qu

artz

ites

, ba

sal

quar

tz

pebb

le c

ongl

omer

ate

(Kar

tiker

e co

nglo

mer

ate)

K

alas

apur

a F

orm

atio

n

Def

orm

ed a

ngul

ar u

ncom

form

ity

Pen

insu

lar

Gne

iss

with

Tro

ndjh

emit

e-gr

anod

iori

te p

luto

ns (

>30

00 M

a)

SA

RG

UR

G

RO

UP

(3

.1-3

.3 G

a)

Gor

ur G

neis

s (3

.3-3

.4 M

a)

Ult

ram

afic

-maf

ic la

yere

d co

mpl

exes

, tho

leiit

ic a

mph

ibol

ites,

kom

atii

tes,

BIF

Qua

rtzi

tes,

pel

ites,

mar

bles

and

cal

c-si

lica

te r

ocks

Intr

usiv

e/ T

ecto

nic

Con

tact

Intr

usiv

e/ T

ecto

nic

Con

tact

Chapter-2

28

The rivers originating in the Western Ghats drain the schist belt of Dharwar super group at

their source and further flow downwards in the northwesterly or southwesterly direction

draining the larger part of the Precambrian Peninsular gneiss and the Phanerozoic lateritic

cover from the foot of the Ghats till the coastal tracts which are later covered by the more

recent alluvial plains along the shorelines. The geology map and the stratigraphic relations

of the coastal tracts and the adjacent Western Ghats covering the study area are given in

Fig. 2.5 and Table 2.2 respectively.

Table 2.2: Stratigraphy relations of the coastal tracts and the adjacent Western Ghats (after

Manjunatha and Harry, 1994)

Global

Stratigraphy

Coastal Tract Western Ghats Geochronometry

(Ma BP)

Cenozoic Recent to sub-recent

alluvium

Quaternary pebble beds

Tertiary laterites

Rhyodacite-Granophyree

St. Mary dacite

- 0.01

1.60

64.4-65

Proterozoic Sullia Syenite

Acid, basic and ultrabasic

dykes

-

540-570

Archean Kanara batholith Narasiparvata formation

Kodachadri formation

Kudremukh formation

Walkunje formations

Gneisses

Remnant metamorphites

Basement unknown

3000

Chapter-2

29

Figure 2.5: Geological map of study area covering Swarna-Madisal-Sita (Udupi),

Nethravati-Gurupur (Mangalore) and Gangolli (Kundapur) river basins, and Western

Ghats Belt region. (after Balasubramanyan, 1978; Geological Survey of India, 1981;

Ramakrishnan and Harinadhababu, 1981; Manjunatha and Harry, 1994; Radhakrishna and

Vaidyanadhan, 1997).

The geology of the study area is explained by the Precambrian rocks of older Sargur group

and younger Dharwar group and Phanerozoic formations (Swaminath and Ramkrishnan,

Chapter-2

30

1981). The details of classification are from Manjunatha and Harry, 1994 and the

references there in.

a) Precambrian rocks:

(i) Ancient Supracrustals (Sargur Group): The high grade metamorphic rocks of upper

amphibolites to lower granulite facies which occur within the gneiss and the granite

comprise the Sargur group (Swaminath and Ramkrishan, 1981; Radhakrishna, 1983). The

major rock types include pyroxene granulites, garnetiferous biotite gneisses, graphite

garnet-kyanite-sillimanite-corundum schists, garnetiferous corundum mica schists and

gneisses, quartzites, pyribolites, garnetifereous amphibolites in granitic gneisses, quartz

chlorite talc actinolite schist, serpentinites, metaultramafites, etc. The southern part of the

coastal tracts of study area, particularly Sullia, Puttur and Dharmasthala, exhibit wide

distribution of Sargur equivalents (Awasthi and Krishnamurthy, 1979; Ravindra and

Janardhan, 1981). The enclaves of Sargur equivalents are also reported in Kanara granites

of Mujimalai (Ramakrishnan and Harinadhababu, 1981). Several places of Udupi and

Karkala taluks exhibit enclaves of amphibolites in Kanara granite batholiths. The presence

of quartzites are reported in the Karkala taluk particularly in the northeast of Donikal;

sillimanite garnet schist around Viregulli, and sillimanite garnet biotite schist enclaves in

the Kanara granite near Nakrebalgudda (Ramakrishnan and Harinadhababu, 1981).

Peninsular gneiss consisting of migmatic grey gneiss which falls within TTG composition

covers the major part of the coastal tract (Swaminath and Ramkrishnan, 1981; Naqvi and

Rogers, 1983; Radhakrishna and Naqvi, 1986). The gneisses in the region are reported to

be of 3.2 Ga (Balasubramanyan, 1978). The Kanara batholith, of granitoid composition,

intrusive into the gneiss is dated to be of 2.6 Ga by Rb/Sr dating method

(Balasubrahmanyan, 1978).

Charnockite patches can be seen in the southernmost part of the study area particularly in

the Nethravati-Gurupur basin at Bantwal, Belthangadi, Mudbidri and south of Binduhole

(Ramakrishnan and Harinadhababu, 1981; Rammohan Rao, 1968; Iyengar, 1954). Few

patches of charnockites are observed in Kanara batholith of Karkala taluk, but restricted to

Belman region of Mulki river basin. No charnockite patches have been reported in the

Swarna-Madisal basin. This could be due to the low grade metamorphism in the north

compared to the south of the Dharwar craton (Pichamuthu, 1961; Radhakrishna, 1983).

(ii) Dharwar supergroup: The Peninsular Gneiss basement are unconformably overlaid by

the Dharwar supergroup rocks like metavolcanics, banded magnetite quartzites, and

Chapter-2

31

porphyritic lavas, tuffs and chlorite schist. Dharwar supergroup is classified into younger

(upper) Chitradurga group and older (lower) Bababudan group. The Bababudan group is

dominated by the rocks which have undergone amphibolite facies of metamorphism and is

known for its iron and manganese ore deposits. Bababudan group is further classified into

four formations in Western Karnataka (Ramakrishnan and Harinadhababu, 1981) which

include:

Walkunji formation - The formation well developed near Walkunji is composed of

oligomict conglomerate bed and often contains uranium and pyrite mineral occurrences

(Aurora, 1985). The rock types associated with this formation are quartzite, quartz sericite

schist, sub-greywacke arkose and quartz chlorite biotite schist.

Kudremukh formation – The thick sequence of metamorphosed basic volcanics with minor

intercalations of meta sediments, indicating that spurts of volcanic flows intervened with

periods of sedimentation form the characteristic feature of this formation (Ramakrishnan

and Harinadhababu, 1981). The metamorphosed volcanic rocks are composed of

amphibolite, actinolite chlorite schist, greenstones, metagabbro and ultramafics (Drury et

al. 1983). The interior part of the formation exhibit minerals of greenschist facies whereas

the amphibolites facies of rocks are found in the outer margin (Ramakrishnan and

Harinadhababu, 1981).

Kodachadri formation – The thick sequence of iron stone with alternative layers of quartz

chlorite sericite schist characterizes this formation. These rocks are well developed around

hill ranges of Aroli near Kudremukh and Kodachadri.

Narasiparvata formation: This formation is found outside the study area in the northeastern

part extending from Sringeri to Narasiparvata through Shitebhumi, Kalasa and Sulebail. It

is composed of acid igneous porphyrites, lavas and tuffs.

On the contrary, the Chitradurga group of rocks includes greywacke – argillite suite of

rocks with volcanic pyroclastic material, and limestone and dolomite suggestive of low

grade metamorphism. This group of rocks dominates the eastern part of Western Ghats of

Uttar Kannada rather than the study area.

Intrusives: Dykes of doleritic composition are found in the study area. These were found to

be emplaced into the Archean rocks around 2.2 Ga (Balasubrahmanyan, 1975).

b) Phanerozoic formations:

There is no formation of Palaeozoic and Mesozoic in the study area except the columnar

dacites of St. Mary Island (Naganna, 1966) dated at 93 Ma (Valsangkar et al. 1981). The

Chapter-2

32

laterites and bauxites covering the region from coastal tract to the foot of the Ghats are

found to be of Tertiary period (Vishwanathaiah et al. 1974; Devaraju and Khanadali,

1983). Quaternary formations are represented by boulder-pebble beds deposited in the

palaeo-channels of Nethravati-Gurupur rivers (Subrahmanya et al. 1991). Recent to sub-

recent sand and gravel deposits are found in the beaches, estuaries and rivers.

2.2. MATERIALS AND METHODOLOGY

The sample collection, sampling locations, sampling method and analytical methods

followed in this study are explained in detail in this section. Samples of river water,

groundwater, rainwater, estuarine water, and suspended particulate matter (SPM) and bed

sediment (both from river and estuary) were collected from the study area.

2.2.1. Samples and sampling techniques

The detailed description on the materials and methodology for sampling are as follows:

2.2.1.1 River sampling

Monthly water samples and seasonal sediment samples were collected from the study area

over a period of two years.

2.2.1.1.1. Water sampling from river

The water samples from Swarna River were collected on a monthly basis from eight fixed

locations (Fig. 2.1.a) for a period of two years from mid 2010 to mid 2012. The samples

were collected at four locations from the main river channel which includes each at

upstream Mudar and midstream Yennehole and two at downstream, Puthige and Manayi.

The samples from the four main tributaries include one sample each from Happanadka

hole at Kervashe, Durga hole at Durga, Andar hole at Hermunde and Kada hole at

Muniyal. In addition, samples were collected monthly from three fixed locations of

Madisal River flowing adjacent to Swarna River. The sampling stations for Swarna-

Madisal rivers are shown in Fig. 2.1.a. Few seasonal samples from the southern basins of

Nethravati-Gurupur rivers (Fig. 2.1.b) and northern basins of Seetha and Gangolli rivers

(Fig. 2.1.c and Fig. 2.1.d) were also collected for comparison. The water samples were

Chapter-2

33

collected from the centre of the river channel at the road bridge. Samples from the river

were collected using the polyethylene bucket tied with a nylon rope so as to avoid any

metal contamination. Onsite analysis of water samples at each sampling station were

conducted for measuring the physico-chemical parameters like temperature (T, °C), pH,

electrical conductivity (EC, µS cm-1), and dissolved oxygen (DO, mg L-1). These physico-

chemical parameters were measured using pre-calibrated Hach® make multi-parameter

apparatus by dipping the pH, conductivity and Luminescent Dissolved Oxygen (LDO)

probes in river water and thus, recording the onsite measurements. The samples were also

analyzed for alkalinity in the field using Merck Alkalinity test kit. The river water samples

were collected in pre-cleaned (rinsed with ultra-pure water before collection) one litre

polypropylene (PP) bottles after rinsing it several times with the river water to avoid any

dilution. The bottles were covered with polythene bags and carried to laboratory for further

processing. The one litre water samples collected at each station were filtered through 0.22

µm pore size and 47 mm diameter Nuclepore membrane filters, using a Sartorius filtration

apparatus operated through a Mityvac® make hand vacuum pump. Filtration was carried

out in a laminar flow bench placed in a clean laboratory on the same day within 4 to 6

hours of sample collection. The first 50 ml of filtered water samples were discarded, while

another 100 ml of filtered sample were used for rinsing the pre-cleaned PP bottles. The

next set of filtered water samples were stored in rinsed 125 ml of PP bottle for major ions,

silica and bicarbonate analyses and were preserved at 4°C until analysis. The last set of

filtered water samples were stored in acid cleaned (1N HNO3) 60 ml PP bottles, separately

for trace elements, rare earth elements (REEs), dissolved organic carbon (DOC) and

radiogenic strontium isotope (87Sr/86Sr) analyses. The samples were then acidified with

ultra-pure nitric acid (pH<2) and stored in a cool condition to arrest bacterial growth.

Maximum care was taken during sample collection, storage and analysis of water samples

to avoid any contamination during sample handling. The samples for major ions, trace

elements and REEs, DOC and radiogenic strontium isotope were analyzed using Ion

Chromatography (IC), Inductively Coupled Plasma Mass Spectrometry (ICPMS), TOC

analyzer and Thermal Ionization Mass Spectrometry (TIMS) respectively at Geosciences

Environnement Toulouse (GET), France.

Chapter-2

34

2.2.1.1.2. Sediment sampling from river

Suspended particulate matter (SPM): The suspended particulate matter was collected

from the main channel of the Swarna and Seetha rivers during the monsoonal season of

2011 and 2012. The river particulate samples were collected at Mudar, Yennehole and

Puthige of the Swarna River, and Someshwar and Kokkarne of the Seetha River for major

and trace element analyses. Water samples from the center of the river channel were

collected using the polyethylene bucket tied with a nylon rope so as to avoid any metal

contamination. Five litres of river water was collected in a pre-cleaned tightly capped

polythene container at each station and transported to the laboratory for further processing.

Samples were filtered in the laboratory through 0.47 µm pore size and 47 mm diameter

cellulose acetate filters (Sartorius® make) held in a Sartorius® polycarbonate filter holder

operated through a Mityvac® make hand vacuum pump. Filtration was carried out in a

laminar flow bench placed in a clean laboratory on the same day within few hours of

sample collection. The unfiltered residue left over the filter paper was then washed with

the filtered water of the same river, to a 50 ml centrifuge tube. The slurry was centrifuged

using REMI make centrifugator run at 4000 RPM. The centrifuge tubes were then dried at

60°C in a Hot Air Oven (REMI® make) until complete dryness of the particulates. The

weights of the centrifuge tube before addition of the residue and after drying were

measured. The final weight of the Suspended Particulate Matter (SPM) was then obtained

by weighing the dried samples. The suspended particulate matter was preserved in a clean,

dry laboratory space until analysis. The SPM samples were subjected to acid digestion and

were later analyzed for major elements and trace elements using ICPMS available at GET,

France. The details of particulate digestion and analysis are explained under the analytical

techniques section.

However, the SPM concentration in each sample of Swarna-Madisal rivers for the two

years sampling period was obtained by weighing the filters before and after filtration of

one litre of water samples collected for geochemical analysis and then calculating the final

weight of SPM.

River bed sediment: The sediment samples from the river bed were collected during the

low flow seasons. The bed sediment sampling in the Swarna-Madisal rivers were carried

out at eleven stations during December 2010, April 2011, December 2011 and April 2012.

Chapter-2

35

Two bed sediment samples were also collected from the Seetha River during December

2011 and April 2012. About 2-3 kg of bed sediment was collected either from the center of

the river channel (in most of the stations) or few meters away from the river bank. The

sediment samples were collected using polythene scoop and transferred to a polythene bag

and secured with a rubber band to avoid metal contamination. The samples were double-

bagged with zip-locked polythene bag to avoid contamination during transportation. In the

laboratory, the bed sediments were wet sieved using a 63µm (240 mesh size) nylon sieve

(supplied by Coleparmer®). The fine fraction (<63µm) of each sample was allowed to

settle in closed pre-cleaned teflon/polypropylene containers for a day and the supernatant

water was separated. The fine fractions are then dried at 60°C using hot air oven (REMI®

make) until complete dryness. The dried samples were finely powdered using an agate

mortar and pestle and stored in zip-locked polythene bags for further processing.

Maximum care was taken to avoid any contamination or metal contact during the sample

handling, particularly during sediment sieving and powdering. Sediment processing was

carried out in a clean laboratory. Although all the samples were processed and dried in the

laboratory, only few samples of April 2012 were subjected to acid digestion and analysis,

as per the availability of laboratory facilities.

2.2.1.2. Groundwater sampling

Seasonal samples of groundwater were collected from Swarna – Madisal basin for a period

of two years from December 2010 to August 2012. The groundwater samples include

eleven open wells and two bore wells (deep wells) for each sampling period (Fig. 2.1.a).

The samples from the open wells were collected using the polyethylene bucket tied with a

nylon rope whereas for the bore well samples, the initial water was discarded by hand

pumping for about ~5-10 minutes to minimize contamination from the pipelines and then

pump further to collect the water samples directly into the pre-cleaned PP bottles. The

sample bottles were rinsed thrice with water sample before collection. The sample bottles

were kept in a polythene bag and zip locked while transportation. About 10 ml of

unfiltered water sample for stable isotope measurement was filled in a glass bottle and

sealed with parafilm immediately after collection in the field. Onsite measurement,

processing and preservation of samples for geochemical analysis were carried out adopting

similar procedures as that of river water. The parameters measured in groundwater samples

Chapter-2

36

are physico-chemical characteristics, major ions, silica, DOC, trace elements and stable

isotopes of oxygen (δ18O) and hydrogen (δ2H). The analysis of trace elements and rare

earth elements was carried out only for one year seasonal samples of August 2011,

December 2011 and April 2012.

2.2.1.3. Rainwater sampling

The rainwater samples were collected at six different stations (Fig. 2.1.a) in the Swarna-

Madisal basin during the year 2012. The sample stations were selected as follows:

Santhekatte – considered as the reference for the coastal sample, Manipal – reference for

last downstream sampling, Yennehole – reference for midstream sampling, Mudar –

reference for upstream sampling, Karkala – reference for any possible anthropogenic

influence, Hebri – reference for Western Ghats effect. The rainwater samples were

subjected to analyses of major ions, radiogenic strontium isotope and stable isotopes of

oxygen and hydrogen.

2.2.1.4. Estuarine sampling

Water, SPM and bed sediment samples were collected seasonally from the Swarna estuary

for a period of one year. The estuarine sampling was carried out during January 2011

(post-monsoon season), May 2011 (pre-monsoon season) and early October 2011

(monsoon season). The sample locations at different periods of sampling along with

sample numbers are shown in the Fig. 2.3.

2.2.1.4.1. Water sampling from estuary

The water samples were collected seasonally from the Swarna estuary during the low tide

cycle. A wooden fishing boat was used to collect the water samples from the estuary and

the adjacent Arabian Sea. Samples were collected along the salinity gradient at different

intervals between 0 ‰ (freshwater end member) and 34.8 ‰ (towards marine end

member). The tidal influence reaches up to Santhekatte (station 425 in Fig. 2.3) during the

monsoonal (October 09, 2011) and Perampalli (station 405 in Fig. 2.3) during the post-

monsoonal (January 29, 2011) periods of sampling. The discharge of river water into the

sea was negligible during the pre-monsoonal season (May 13, 2011) as the river water was

Chapter-2

37

completely blocked by the Baje dam at Hiriyadka (about 20 km inland along the river

channel). As a result, the tidal influence reaches up to Baje dam. The salinity measured at

the downstream of this dam (within 500 m downstream) was 17.7 ‰ and further upstream

there was no water available for the mixing signatures during the pre-monsoonal season.

Physico-chemical parameters such as pH, electrical conductivity, salinity, dissolved

oxygen and alkalinity were measured onsite, similar to that of river water. The salinity

measurements were cross checked for few of the samples at laboratory using Elico salinity

meter. The estuarine water samples were collected at each station for a fixed salinity

interval (~5 ‰) in a pre-cleaned (rinsed with ultra-pure water before collection) one litre

PP bottle after rinsing it several times with the sample water to avoid any dilution. The

sample bottles were covered with polythene bags and carried to the laboratory for further

processing. The filtration and processing of estuarine water samples were carried out

similar to river water samples with utmost care so as to avoid any contamination during

sample handling. The processed water samples were analyzed for trace elements and

REEs, DOC and radiogenic strontium isotope using ICPMS, TOC analyzer and TIMS at

GET, France.

2.2.1.4.2. Sediment sampling from the estuary

The estuarine particulate (SPM) and bed sediment samples were collected seasonally from

the Swarna estuary for a period of one year during 2011. For SPM, five litres of water

samples were collected along the salinity gradient in pre-cleaned polythene containers to

separate the particulate matter. The suspended particulate matter was separated in the

laboratory following the similar procedure as adopted for riverine particulates.

The bed sediment samples were also collected from the Swarna estuary at different salinity

gradients from fresh water end member to marine water end member. The bed sediments

were collected using a Polyvinyl Chloride (PVC) core of 15 feet length and 15cm

diameter. The bed sediment cores were transferred to polythene bags and tied with rubber

band. The collected samples were further processed using similar protocol followed for the

river bed sediments.

Chapter-2

38

Although all estuarine SPM and bed sediment samples were processed and dried, only few

bed sediments and SPM (single sample) were subjected for acid digestion and analysis, as

per the availability of laboratory facilities.

2.2.1.5. Sample collection for stable isotope study

Water samples were collected during the monsoonal and post-monsoonal seasons at

different stations along the Swarna-Madisal rivers (2011-2012) and the Nethravati-

Gurupur rivers (2011; and previously published data of 2009-2010 are referred). Samples

of surface water, groundwater and rainwater were collected in 10 ml tight-capped glass

vials for 18O and 2H measurements and were kept at stable temperature until analysis.

River water samples were collected to measure the stable isotopes of oxygen (18O),

hydrogen (2H), carbon (13C) and carbon concentrations in both organic (DOC and POC)

and inorganic (HCO3) form. Additional samples of ground water were collected adjacent

to river water sampling locations for the measurement of water isotopes (18O and 2H) to

understand the seasonal buffering effect on the river water. The rainwater samples were

collected during 2012 at Santhekatte near Kallianpur (16 samples), Manipal (16 samples)

and Hebri (15 samples) in the Swarna-Madisal basin to determine the spatial variability of

isotopic composition in the moisture originating from the west coast and moving towards

inland and the local processes controlling their signatures. Also, the samples of surface

water, groundwater and rainwater were collected at different stations along the central

stretch of the Western Ghats, and its western and eastern parts covering Karnataka, Kerala

and Tamil Nadu during November 2013.

2.2.2. Analytical techniques

2.2.2.1. Physico-chemical parameters

The physico-chemical parameters of river water, groundwater and estuarine water were

measured soon after collection in the field at each sampling station. Water samples were

analyzed for temperature (T °C), pH, electrical conductivity (EC µS cm-1), dissolved

oxygen (DO mg L-1), total dissolved solids (TDS mg L-1) and salinity (‰) at each

sampling station. Each parameter was measured using its respective probe connected to

Hach make multi-parameter apparatus available at Environmental Research laboratory

Chapter-2

39

(ERL), Department of Civil Engineering, Manipal Institute of Technology (MIT),

Manipal. pH, EC and DO were measured using the respective probes which were

calibrated in the laboratory, prior to sampling. Salinity of water sample was measured

using EC probe whereas temperature was measured in each probe. The pH and EC probes

were calibrated using pH buffer solutions (pH = 4.01, 7.01, 10.02) and NaCl solution

(1000 µS cm-1) respectively. The accuracy of instrument measurement is ±0.3 °C for T,

0.01 units for pH, ±0.1 mg L-1 for DO, ±0.5 % of reading for EC and TDS, and ±0.1 ‰ for

salinity. The reading for each parameter was recorded only after attaining stabilization in

the instrument measurement. Onsite analysis of water samples for alkalinity was carried

out using Merck make alkalinity test kit.

2.2.2.2. Major ions

The filtered water samples were analyzed for major ions using DIONEX-1100 Ion-

chromatography (IC) fitted with Autosampler available at MIT under the Central

Instrumentation Facility (CIF) of Manipal University, Manipal. The details of analysis are

as follows. Sample aliquot of 5 ml was taken in a poly vial fitted with a filter cap. It is

placed in the autosampler connected to IC, ready for analysis. Major cations like Na+, K+,

Ca+2, Mg+2 and NH4+ and anions like F-, Cl-, NO3

-, PO4- and SO4

2- were analyzed

simultaneously using cation and anion systems of Ion Chromatography, having separate

columns and suppressors for each system. The instrument was calibrated before the sample

analysis using Merck cation and anion standards. The concentration of eluants prepared

were of mixture of 8mM NaCO3 and 1 mM NaHCO3 for anions and 20 mM of Methane

sulphonic acid (MSA) for cations. The analytical accuracy was checked using the certified

reference material ION-915 obtained from National Water Research Institute (NWRI),

Canada. The measured values for ION-915 were within ±5% of the certified values (Table

2.3). The analytical precision was obtained by repeated analysis of samples as well as the

certified material and the results were within ±5% error limits. Also, the results were

verified by analyzing several samples at GET, Toulouse, France and were found to be of

highly precise (within ±5 % error). The procedural blanks were run before, during and

after the analyses and were found to be below the detection limits for all cations and

anions.

Chapter-2

40

Table 2.3: Analysis of certified reference standard (ION-915) to test the accuracy and

precision of measurements.

Elements Certified value (mg L-1) Measured values (mg L-1) Error in accuracy

(%) I II Mean Na 1.35 1.39 1.34 1.37±0.04 1.1

K 0.49 0.5 0.51 0.505±0.007 3.1 Ca 13.4 13.48 13.25 13.37±0.16 -0.3 Mg 2.8 2.91 2.74 2.83±0.12 0.9 F 0.048 0.05 0.04 0.045±0.007 -6.3 Cl 1.39 1.45 1.35 1.4±0.07 0.7 SO4 3.4 3.48 3.2 3.34±0.2 -1.8

The filtered water samples were measured for bicarbonate concentration by acid titration

(0.02N Hydrochloric acid) using automated titration method (Metrohm tiamo 888) fitted

with Ecotrode plus (pH) electrode. The analysis was carried using an autotitrator available

at ERL, Manipal. A gran evaluation method was followed to measure the alkalinity. The

precision of the analysis were within ±3% of error limits.

2.2.2.3. Silica

Water samples of river and groundwater were measured for dissolved silica through

spectrophotometer by silicon molybdate method explained by Eaton et al. 2005. Acid

reagent powder, citric acid powder and molybdate reagent powder pillows for high range

silica supplied by Hach® were used to measure silica in water samples. For each sample

measurement, about 10 ml of water was taken separately in two clean glassy cuvettes. One

10 ml sample cuvette is kept aside as blank sample for measuring concentration which is

used as reference for that particular sample. For the other 10 ml sample cuvette, the

powder of silica molybdate and acid reagent were added. The reaction time was set for 10

minutes. The citric acid powder was added to the same cuvette containing 10 ml sample

and mixture of silica molybdate and acid reagent. The reaction time was set for 2 minutes.

The total reaction time of 12 minutes is required for prior preparation of sample for

analysis. The silica measurement was carried out using UV spectrophotometer (Hach DR

5000) at a wavelength of 452 nm available at ERL, Manipal. The silica concentration in

the sample is obtained by comparing the light intensity absorbed by the sample mixture

with that of the blank sample. The precision for the measurements were within ±1% of

error limits.

Chapter-2

41

2.2.2.4. Dissolved organic carbon

The acidified water samples were measured for dissolved organic carbon (DOC) using

Total Organic Carbon analyzer (TOC analyzer; Shimadzu make) available at GET, France.

The high temperature (680°C) catalytic oxidation combustion technique was used for DOC

analysis in water samples. The total combustion of sample is achieved by heating it to

680°C in an oxygen-rich atmosphere inside the combustion tubes containing the platinum

catalyst. The carbon-dioxide generated by oxidation is detected and the concentration is

measured using an infrared gas analyzer (non-dispersive infrared detector, NDIR). The

analytical measurements were highly precise, within ±5% error limits.

2.2.2.5. Trace elements and REEs

Part – 1 (Trace element analysis of 2010-2011 samples):

The water samples for trace elements were measured using Thermo Scientific –

Quadrupole Inductively Coupled Plasma Mass Spectrometry (Thermo ICP-MS X-Series 2)

available at Mangalore Refinery and Petrochemicals Limited (MRPL), Mangalore. The

ICPMS performance testing was carried out by checking the count rate using

AccuStandard multi-element tuning solution, before sample analysis. The count rates of Li

> 40000 counts, In > 200000 counts and U > 400000 counts were obtained during the

instrument testing. The instrument uses the collision reaction cell technology to overcome

the matrix interferences. The interferences were controlled by using reactive gas mixtures

of 1% ammonia in helium, 7% hydrogen in helium and 100% hydrogen. The conventional

external calibrations were carried out using standard solutions of trace elements prepared

from mono- and multi-element standard solutions (AccuStandard, USA). The

concentrations of twenty six trace elements were measured in river water samples and

were subsequently deducted from the procedural blank. The procedural blank

concentrations for selected trace elements are shown in Table 2.4.a. The water samples

were directly analyzed for trace elements using ICP-MS without any internal standard

addition to the samples. The data were cross-checked for accuracy and precision with

SLRS-5 (certified river water reference material obtained from National Research Council,

Canada) and triplicate analysis of each sample. The measured values of SLRS-5 were

found to be in good agreement with the certified values of SLRS-5 as shown in Table

2.4.a. The accuracy for the measured values of SLRS-5 was found to be within the

Chapter-2

42

acceptable error limits, (±3%) for most metals and slightly higher (±8%) for Mn, except

for Cd which showed a relatively higher value (±20%). However, Cd was found to be in

lower concentration (< ng L-1) in Swarna river water. The precision for all the samples

analyzed were found to be within the acceptable error limits (±5%).

Additional details: The data on average rainfall for the entire river basin for the study

period (2010-2011) and the average discharge data for Swarna River used in the statistical

analysis were collected from NASA website

(http://disc2.nascom.nasa.gov/Giovanni/tovas/) and Central Water Commission (CWC),

Government of India respectively. The temporal and spatial studies on physico-chemical

parameters and trace elements were carried out using Statistical Package for Social Science

version 12 (SPSS 12.0v). The inter-variability relationship between trace elements and

physico-chemical parameters, DOC and total dissolved solids (TDS = sum of major

cations, major anions and silica) were found using comparative analysis of Pearson

correlation technique and Centroid clustering method of cluster analysis technique

respectively, supported by SPSS-12.0v. The results of the work are based on the data

obtained for all the four stations during September 2010 (monsoon), November 2010

(post-monsoon) and March 2011 (pre-monsoon) representing the seasonality of Indian

sub-continent. Additional samples of August 2010, February 2011 and May 2011 for

downstream station (Puthige) were analyzed to represent overall trace element status in the

basin for the study period.

Table 2.4.a: Analysis of certified reference river water standard, SLRS -5 obtained through

National Research Council, Canada for testing of accuracy and precision, along with

procedural blank concentrations.

Trace elements SLRS-5 Recommended concentration ± Standard deviation (µg L-1)

SLRS-5 Measured concentration ± Standard deviation (µg L-1)

Blank ± Standard deviation (µg L-1)

Mn 4.33 ± 0.18 4.033 ± 0.041 -0.065 ± 0.001

Cu 17.4 ± 1.3 16.92 ± 0.098 -0.052 ± 0.001

Zn 0.845 ± 0.095 0.866 ± 0.049 -0.247 ± 0.016

As 0.413 ± 0.039 0.4 ± 0.015 0.145 ± 0.002

Sr 53.6 ± 1.3 54.32 ± 1.012 0.04 ± 0

Cd 0.006 ± 0.0014 0.007 ± 0.001 0.003 ± 0.001

Ba 14 ± 0.5 13.56 ± 0.104 -0.172 ± 0.001

Chapter-2

43

Part – 2 (Trace elements and REEs analysis of 2011-2012 samples):

The trace element and rare earth element concentrations in water samples were measured

using a quadrupole ICP-MS 7500ce (Agilent Technologies) available at GET, France. The

analytical drift was controlled and calibrated using an internal In-Re standard

(concentration of 0.4033 ppm; Solution No. 63). The corrections for oxide and hydroxide

isobaric interferences were made for the REE (Aries et al. 2000). The analytical accuracy

and precision were checked by repeated analysis of certified international reference water

(SLRS-5) and were found to be within the permissible error limits. The certified and

measured values of SLRS-5 are given in Table 2.4.b. The recommended concentrations of

REEs are not certified for the SLRS-5 standard. However, the REE measurements in

SLRS-5 are in good agreement with the values proposed by Heimburger et al. 2013. The

reference values and measured values for REEs in SLRS-5 are given in Table 2.4.c.

Table 2.4.b: The certified and measured values for the reference material (SLRS-5) used

during trace element analysis.

Elements Certified value (µg L-1)Measured values (µg L-1) Error in

accuracy (%) I II Mean

Al 49.5 ± 5 49.98 49.2 49.59±0.55 0.2

Sb 0.3 0.2966 0.2879 0.2923±0.01 -2.6

As 0.413 ± 0.039 0.3944 0.3875 0.391±0.005 -5.3

Ba 14.0 ± 0.5 14.35 14.25 14.3±0.07 2.1

Cd 0.006 ± 0.0014 0.008 0.0068 0.0074±0.001 23.3

Cr 0.208 ± 0.023 0.2075 0.1943 0.201±0.01 -3.4

Co 0.05 0.058 0.0577 0.0579±0.0002 15.7

Cu 17.4 ± 1.3 18.72 18.33 18.53±0.28 6.5

Fe 91.2 ± 5.8 92.69 91.74 92.22±0.67 1.1

Mn 4.33 ± 0.18 4.351 4.331 4.34±0.01 0.3

Mo 0.27 ± 0.04 0.2543 0.2504 0.2524±0.003 -6.5

Ni 0.476 ± 0.064 0.4641 0.4647 0.4644±0.0004 -2.4

Sr 53.6 ± 1.3 53.28 53.01 53.15±0.19 -0.8

U 0.093 ± 0.006 0.090 0.089 0.0895±0.0005 -3.7

V 0.317 ± 0.033 0.302 0.298 0.3±0.003 -5.4

Zn 0.845 ± 0.095 0.848 0.841 0.844±0.005 -0.1

Chapter-2

44

Table 2.4.c: Comparison of measured values of REEs in SLRS-5 with that of the literature

reported values (Heimburger et al. 2013).

Elements Reported Value (ng L-1) Measured values (ng L-1) Error in Accuracy

(%) I II Mean

La 196.0±11 176.4 176 176.2±0.28 -10.1

Ce 236.0±16 243.8 247.4 245.6±2.55 4.1

Pr 46.9±2.5 51.6 52.4 52±0.57 10.9

Nd 185.0±20 194 192.6 193.3±0.99 4.5

Sm 32.4±3.3 34.76 34.42 34.6±0.24 6.8

Eu 5.6±1.4 5.38 5.36 5.37±0.01 -4.1

Gd 24.9±3.0 24.3 24.06 24.18±0.17 -2.9

Dy 18.2±2.5 20.4 19.8 20.1±0.42 10.4

Ho 3.6±0.5 4.36 4.14 4.25±0.16 18.1

Er 10.5±1.0 10.7 10.4 10.55±0.21 0.5

Yb 9.3±0.7 9.5 8.9 9.2±0.42 -1.1

2.2.2.6. Radiogenic Strontium Isotope

The radiogenic isotopic composition of strontium in water samples were measured using

TIMS available at GET, France. Strontium (Sr) was separated from the matrix following

the procedure described in Violette et al. (2010) and adapted from Deniel and Pin (2001).

A known volume of water sample, corresponding to about 500 ng of Sr, was evaporated in

a pre-cleaned teflon vial at 70°C. The evaporated sample was dissolved using 0.5 ml to

1ml of 1N double distilled HNO3 of known volume. The vial containing the mixture was

sonicated for 15-20 minutes to improve the dissolution of evaporates in 1N double distilled

HNO3. The pre-cleaned chromatographic columns for Sr separation were first loaded with

150 µL of ‘Sr-Spec 50-100 µm’ resin. The columns were then placed in the automate -

chromatographic separation hood. The samples were loaded on the column. Strontium was

eluted using 0.05N HNO3 solution and evaporated at 70°C. Procedural blank was lower

than 20pg, which is negligible compared to the 500ng of Sr loaded on the column. Isotopic

composition of Sr was analyzed with a TIMS Mat Finnigan 261 at GET. Dried Sr fraction

was dissolved in 5µL of 1N HNO3. About 2µl of 0.05 M phosphoric acid was loaded on

the filament (single filament) prior to strontium. The deposit was dried at 1 ampere and

later slowly heated to 2 amperes for 10 seconds. The isotopic analysis was carried out by

simultaneous multi-collection on Faraday cups. The heating temperature of the filament

during analysis was about 3.1 amperes. The isobaric interference of 87Rb on 87Sr, if any,

Chapter-2

45

was corrected through the interfering element correction methodology of the software. The 87Sr/86Sr isotopic ratio was corrected for Rayleigh fractionation using 88Sr/86Sr = 8.3786 as

normalizing ratio. The Sr isotopic data was acquired in 5 blocks of 12 cycles each with the

integration time of 10 sec for each cycle. Usual accuracy of analysis is about 0.00001 (2).

Validity of data was checked using the international standard NBS 987. The values

obtained during this study (mean = 0.71021 ± 0.000048) were in agreement with the

certified value (Table 2.5).

Table 2.5: Comparison of certified and measured values of 87Sr/86Sr in the standard

reference material (NBS-987) and the values are found to be in good agreement.

NBS-987 Certified value Measured values

87Sr/86Sr 0.710248

1 0.710204 ± 0.000049 2 0.71021 ± 0.000044 3 0.710188 ± 0.000052 4 0.710218 ± 0.000046 5 0.710241 ± 0.000055 6 0.710198 ± 0.000044 Mean 0.71021 ± 0.000048

2.2.2.7. Stable isotopes

Stable isotopes of oxygen and hydrogen:

Samples of surface water, groundwater and rainwater collected in 10 ml tight-capped glass

vials were kept at stable temperature until analysis. In the laboratory, 0.3 ml aliquots of the

water were taken in capped 3.7 ml Exetainer vials (Labco Ltd., High Wycombe, UK). To

measure the 18O values of the water samples, the samples and the internal standards were

flushed offline with a gas mixture of 5% CO2 in He. The Exetainer vials were then left to

equilibrate at 40 °C for about 8 h. The analytical precision of the measurements was ± 0.25

per mil (‰). To measure the 2H values of the samples, Hokko beads were added to the

Exetainer vials containing the water samples and the internal standards before the vials

were flushed offline with a gas mixture of 5% H2 in He. The Exetainer vials were left to

equilibrate at 40 °C for about 8 h. The analytical precision of the measurements was ± 2.5

‰.

Chapter-2

46

The spectrometer was calibrated by using four working standards that are traceable to the

primary reference standards V-SMOW2 (Vienna-Standard Mean Ocean Water) and V-

SLAP2 (Vienna-Standard Light Antarctic Precipitation) distributed by the IAEA

(International Atomic Energy Agency), Vienna, Austria. The results are expressed in per

mil on the V-SMOW/SLAP scale, for oxygen:

18O V-SMOW2 (‰) = (((18O / 16O)sample / (18O / 16O)standard)1) x 1000

For deuterium:

2H V-SMOW2 (‰) = (((2H / 1H)sample / (2H / 1H) standard)1) x 1000

For the calculation of the deuterium excess (d-excess), the equation for the Global

Meteoric Water Line defined by Craig, 1961 which was later redefined as given in the

following equation by Dansgaard, 1964 for the meteoric water lines, was used.

d-excess (‰) = 2H – (8 x 18O)

Stable isotopes of carbon:

To study the carbon isotopes, water samples were collected during the average water flow

season of November 2011 at six different stations of the Swarna and Nethravati rivers. At

each station, one litre of river water was filtered in the field through a 0.45 m ashed GF/F

glass fibre filter (Millipore, Billerica, USA). For DOC, 125 ml of filtered water was

collected in polypropylene bottle and acidified with concentrated HCl to avoid any

bacterial activity. For dissolved inorganic carbon (DIC), 125 ml of filtered water was

collected in a similar bottle. All the bottles were carefully sealed, taking care to ensure that

no trapped air remain in contact with the sample, and were stored at 4 °C. The filters were

placed in small plastic bags (zip locked) to determine the amounts of POC.

To extract DIC, the sample aliquot of about 0.3 ml was acidified inside the 3.7 ml

Exetainer vials with concentrated phosphoric acid, and kept at 70°C for 8 hours. The

evolved CO2 was then purified and analyzed using IRMS. The resulting analytical

precision of the measurements was ± 0.2‰.

Chapter-2

47

The results are reported as values with reference to the Vienna Pee Dee Belemnite

(VPDB; Craig, 1957):

13C VPDB (‰) = (((13C / 12C)sample / (13C / 12C)standard)1) x 1000

For the POC, the filters were dried and weighed, and a part of the filter was placed in a tin

cup for carbon elemental analysis. The carbon isotopic composition (13C) was measured

through an isotope ratio mass spectrometer (IRMS) coupled to an elemental analyzer.

Other related chemical analysis:

The Specific UV Absorbance (SUVA) was measured at 245 µm on an absorption

spectrophotometer Secoman (UV Light XT5). The concentrations of DIC in water samples

were measured using an Autotitrator Metrohm (Titrino 716 DMS). DOC and Total

Organic Carbon (TOC) were determined with a Shimadzu TOC 5000 A. The major anions

(sulphate, chloride, nitrate and phosphate) were analyzed using ion chromatography

(Dionex DX-120, eluted with KOH on a column KOH AS11-HC).

The analysis of the samples for stable isotopes were carried out at the Shiva Isotopic

Platform, ENSAT in Toulouse (France) on a continuous flow IRMS (Elementar Isoprime

100 coupled with a Geo-Multiflow for the water–gas equilibration, and a Microcube

Elemental analyzer, Hanau, Germany). The elemental analyses of C and N were used to

calculate the C/N ratios. The analysis of samples for SUVA, organic and inorganic carbon

and major ions were carried out at ECOLAB, University Paul Sabatier, Toulouse, France.

2.2.2.8. Sediment sample digestion and analysis

Sediment digestion and dilution: The sediment dissolution with acid was carried out in a

clean room using the microwave digestion system (CEM make) available at GET, France.

The acid reagents used for sediment digestion and subsequent dilution were ultrapure (HF,

HCl) and double distilled (HNO3) grade. About 50-100 mg of finely powdered bed

sediment/suspended sediment samples were weighed using 0.1 mg accuracy chemical

balance (Sartorius make) and were taken in the liners (Teflon) of microwave digester.

About 5ml of HNO3, 3ml of HCl and 2ml of HF were added to each liner containing the

sediment samples under the acid extraction hood. The liners containing the acid mixtures

Chapter-2

48

along with samples were digested in a Microwave digesting system for 30 minutes at

180°C temperature and at a pressure of 200 psi, until complete digestion. The liners were

allowed to cool inside the microwave digester for 15 minutes and later the acid mixtures

were transferred to pre-cleaned and dried Savillex tubes. The solution was dried by placing

the Savillex tube in the hotplate for about 24 hours at a temperature of 70°C. The dried

samples were dissolved using 2 ml of double distilled nitric acid (trace metal grade). The

solution was diluted by 3000-5000 times using MilliQ water so as to reduce the

concentration of elements to the detection range of ICP-MS. The procedural blank and

international reference geo-standard were digested along with the samples in each batch to

check for any contamination during sediment digestion, dilution and analysis.

Geochemical and radiogenic isotope analyses of sediments: The concentrations of

major elements, trace elements and REEs in SPM and bed sediment samples collected both

from river and estuary were measured using a quadrupole ICP-MS 7500ce (Agilent

Technologies). The analytical drift was controlled and calibrated using the internal Re-In

standard (Solution No. 63; concentration of In and Re = 0.4033ppm). The international

certified reference sediments like LKSD-3 (lake sediment samples obtained from NRC,

Canada) for river sediments and SRM 1646a (Standard Reference Material 1646a) for

estuarine sediments were used for testing the quality of the methods employed throughout

the analysis. The accuracy of measurements for the certified reference material was within

±10% of error limits for most elements as given in Table 2.6.a and Table 2.6.b. The

precision of analysis were checked through repeated analysis of certified reference water

SLRS-5 and were found to be within ±5% of error limits. The strontium isotopes in the

SPM and bed sediment samples were measured along with other water samples using

TIMS available at GET, France. The same analytical protocol as explained for that of

water samples was followed to analyze the radiogenic strontium isotope in sediment

samples.

Chapter-2

49

Table 2.6.a: The certified and measured values (units in mg kg-1 unless mentioned) of

standard reference sediment (LKSD-3) used during river sediment digestion and analysis.

Elements Certified LKSD-3 Measured LKSD-3 Error in accuracy (%)

Na (%) 1.71 1.69 -1.2

Mg (%) 1.21 1.11 -8.3

Al (%) 6.62 5.90 -10.9

P (%) 0.0873 0.0934 7.0

K (%) 1.83 1.76 -3.8

Ca (%) 1.64 1.27 -22.6

Ti (%) 0.2997 0.2879 -3.9

Mn (%) 0.1549 0.1548 -0.1

Fe (%) 3.99 3.42 -14.2

V 82 78.74 -4.0

Cr 87 79.15 -9.0

Co 30 30.16 0.5

Ni 47 53.46 13.7

Cu 35 33.68 -3.8

Zn 152 139.65 -8.1

As 27 25.50 -5.5

Rb 78 75.78 -2.8

Sr 240 247.95 3.3

Nb 8 9.85 23.1

Ag 2.7 2.87 6.1

Sb 1.3 1.20 -7.4

Cs 2.3 2.43 5.6

Ba 680 624.14 -8.2

La 52 47.30 -9.0

Ce 90 84.19 -6.5

Nd 44 40.61 -7.7

Sm 8 7.81 -2.4

Eu 1.5 1.60 6.5

Dy 4.9 4.93 0.7

Yb 2.7 2.53 -6.4

Lu 0.4 0.4147 3.7

Hf 4.8 3.73 -22.3

Ta 0.7 0.6091 -13.0

Pb 29 29.19 0.6

Th 11.4 10.60 -7.0

U 4.6 4.18 -9.1

Chapter-2

50

Table 2.6.b: The certified and measured values of standard reference sediment (SRM

1646a) used during estuarine sediment digestion and analysis.

Elements Certified SRM-1646a Measured SRM-1646a Error in accuracy (%)

Na (%) 0.741 ± 0.017 0.7000 -5.5

Mg (%) 0.388 ± 0.009 0.3692 -4.8

Al (%) 2.297 ± 0.018 2.0796 -9.5

P (%) 0.027 ± 0.001 0.0249 -7.6

K (%) 0.864 ± 0.016 0.8293 -4.0

Ca (%) 0.519 ± 0.02 0.4524 -12.8

Ti (%) 0.456 ± 0.021 0.4440 -2.6

Fe (%) 2.008 ± 0.039 1.98 -1.5

V 44.84 ± 0.76 42.00 -6.3

Cr 40.9 ± 1.9 33.70 -17.6

Mn 234.5 ± 2.8 231.53 -1.3

Cu 10.01 ± 0.34 9.82 -1.9

Zn 48.9 ± 1.6 45.56 -6.8

As 6.23 ± 0.21 6.41 2.9

Cd 0.148 ± 0.007 0.125 -15.5

Pb 11.7 ± 1.2 9.55 -18.4

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