Multivariate statistical evaluation of heavy metals in the surface water sources of Jia Bharali river basin, North Brahmaputra plain, India
Multivariate statistical evaluation of heavy metals in the surface water sources of Jia Bharali river basin, North Brahmaputra plain, India
Nayan J. Khound 0 1
Krishna G. Bhattacharyya 0 1
0 Department of Chemistry, Gauhati University , Guwahati , India
1 & Nayan J. Khound
The aim of this study was to assess the quality of surfacewater sources in the Jia Bharali river basin and adjoining areas of the Himalayan foothills with respect to heavy elements viz. (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) by hydrochemical and multivariate statistical techniques, such as cluster analysis (CA) and principal component analysis (PCA). This study presents the first ever systematic analysis on toxic elements of water samples collected from 35 different surface water sources in both the dry and wet seasons for a duration of 2 hydrological years (2009-2011). Varimax factors extracted by principal component analysis indicates anthropogenic (domestic and agricultural run-off) and geogenic influences on the trace elements. Hierarchical cluster analysis grouped 35 surfacewater sources into three statistically significant clusters based on the similarity of water quality characteristics. This study illustrates the usefulness of multivariate statistical techniques for analysis and interpretation of complex data sets, and in water quality assessment, identification of pollution sources/factors and understanding temporal/spatial variations in water quality for effective surfacewater quality management.
Heavy metals; Principal component; Hierarchical cluster; Brahmaputra plain; Surfacewater source; Jia Bharali river basin
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Department of Chemistry, Digboi College, Tinsukia, India
Introduction
Trace metals attributing as common pollutants are found to
be widely distributed in the river catchments originating
from natural sources and processes as chemical weathering,
soil erosion, fallout of aerosols from marine, volcanic or arid
soil sources. However, as a result of human inputs and
activities
(Merian 1991)
the level of these metals in the
environment has increased tremendously. Due to simplicity
the univariate statistical analysis has been generally used to
treat trace element data in groundwater
(Helena et al. 2000)
.
However, multivariate analysis such as principle component
analysis (PCA) and cluster analysis is widely used to explain
the correlation amongst a large number of variables in terms
of a small number of underlying factors without losing much
information
(Meglen 1992; Ogwoeleka 2015; Pazand 2016;
Qian et al. 2016)
. This method can also help in measuring
natural associations between samples and/or variables
(Wenning and Erickson 1994) and thus highlight the
information which is not available at first glance.
For this study, lower Jia Bharali catchment and
adjoining areas in central part of North Brahmaputra Plain (NBP)
was selected which is characterized by more than 800 m
thick older and younger Alluvium deposited by the west
flowing Brahmaputra river and the south flowing trans
Himalayan rivers
(Khound Nayan et al. 2013)
. The river
regime is highly dynamic with frequent channel changes
and copious sand deposition. Average sediment load
carried by these rivers are coarse, facilitating easy percolation
and recharge of groundwater regime. Published reports
(Chakrapani 2005; Singh et al. 2005; Jameel and Hussain
2007)
reveal that most of the Indian rivers are carriers of
untreated sewage, industrial effluent and runoff from
agricultural and urban land to the surface water bodies
present in their basins. Due to the absence of industrial
zone and large scale irrigation projects the surface and
ground water regime of the study area are expected to be
free from such condition and bear a pristine signature of the
natural environment. The people in the Jia Bharali river
basin seldom use the surface water for drinking as well as
for various household purposes including irrigation of
crops, rearing of poultry and fish, etc. The population of the
basin mainly consists of farmers and fishermen who depend
on the surface water sources for their livelihood. In this
context, the major objectives of this study were to (1)
determine natural associations between surfacewater
samples and metallic variables; (2) investigate the spatial and
temporal variation of trace metal composition of the
surfacewater sources and, (3) demonstrate the usefulness of
the statistical analysis to interpret the trace element
composition of the surfacewater sources of Jia Bharali river
basin.
Materials and methods
Study area
The Jia Bharali catchment is bounded by longitudes
92o00/-93o25/E and latitudes 26o39/-28o00/N. The
drainage system of north Brahmaputra plain, N E India is made
up of a large number of river systems flowing from
Arunachal Himalaya in the north and debouching into the
Brahmaputra in the south. It is an actively subsiding
foreland basin with river regime bearing neotectonic
changes and catchment area tectonics
(Phukon (...truncated)