International Journal of Agriculture, Environment & Biotechnology
Citation: IJAEB: 7(4): 787-795 December 2014
DOI Number: 10.5958/2230-732X.2014.01388.6
©2014 New Delhi Publishers. All rights reserved
SOIL SCIENCE
Soil risk assessment of heavy metal contamination near Oil
Refinery area, Northeastern India
S.K. Reza*, Utpal Baruah 1 and S.K. Singh 2
National Bureau of Soil Survey and Land Use Planning, Sector-II, DK-Block, Salt Lake, Kolkata, West Bengal, India
1 National Bureau of Soil Survey and Land Use Planning, Jamuguri Road, Jorhat, Assam, India
2 National Bureau of Soil Survey and Land Use Planning, Nagpur, Maharashtra, India
*Corresponding author: reza_ssac@yahoo.co.in
Paper No. 269
Received: 15 September, 2014
Accepted: 18 October, 2014
Published: 20 December, 2014
Abstract
The present paper aims to maps Cr, Cd, Ni and Pb concentration and assess the hazard in the soils
of surrounding agricultural fields affected by oil refinery drainage of Digboi refinery of Tinsukia
district, Assam using statistics, geostatistics and GIS techniques. The amounts of Cr, Cd, Ni and Pb
were determined from 97 samples collected within the contaminated area. Among the heavy metals
studied, the mean concentration of Pb was high. The greatest and the smallest standard deviation were
observed in the Ni (44.1) and pH (0.47), respectively. Analysis of the isotropic variogram indicated that
the Cr and Cd semivariograms were well described with the circular model, with the distance of spatial
dependence being 1240 and 1022 m, respectively, while the Pb and Ni were well describe with Gaussain
model, with the distance of spatial dependence being 1930 and 2321 m, respectively. The ordinary
kriging maps of Cr, Cd, Ni and Pb showed that high concentrations of heavy metals were located in the
low lying area. Indicator kriged probability maps of soil Cr, Cd, Ni and Pb were prepared based on the
concentrations to exceed the respective Food and Agriculture Organization maximum permissible limit
(MPL) value of 100, 3, 30 and 50 mg kg −1 , respectively. It was seen that whole studied area had a higher
than 0.99% probability to exceed the MPL value of Pb. About 10% area of the study site was having
higher concentration than MPL value of Cd and Ni concentrated at the centre and north-west corner of
the study area, respectively.
Highlights
  • Apart from transport and municipal services, industrial plants constitute the main source of heavy
    • metals released to environment .
  • A good variogram structure of heavy metals was observed, showing that there are clear spatial
    • patterns of heavy metals on the distribution map and also that the current sampling density is
    sufficient to indicate such spatial patterns.
  • The kriging interpolated map showed areas with high values of heavy metal concentrations. The
    • probability map produced based on indicator kriging provided useful information for hazard
    assessment.
    Keywords: Heavy metals, geostatistics, spatial variability, accuracy assessment, risk assessment
    Apart from transport and municipal services,
    most frequently within urbanized areas (Singh and
    industrial plants constitute the main source of heavy
    Kumar, 2006) and around industrial facilities (Li et
    metals released to environment (Hjortenkrans et
    al., 2006; Shukurov et al., 2006). The petrochemical
    al., 2006). A higher metal content in soils occurs
    and refinery sector is counted among significant