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Enrichment, risk assessment, and statistical apportionment of heavy metals in tannery-affected areas
Ali, Z.; Malik, R.N.; Shinwari, Z.K. & Qadir, A.
Abstract
Tannery-affected surface soils from 72 sampling
sites from industrial area of Sialkot district, Pakistan, were
collected and analyzed for nine physicochemical parameters,
nine heavy metals, and four macro-nutrients. Most of the soils
were poor in organic matter (0.11–2.98 %), basic in nature
with pH(7.1–10.6) and electrical conductivity (1.2–17.9 mS/
cm). Mean concentration of total dissolved solids, Cl1-,
alkalinity, NO⅓-N, salinity, and PO43- was 3,093 mg/L,
6,587, 3,929, 301.3, 10.3, and 1.7 mg/kg. The results showed
that concentration of macro-nutrients was in the order:
Na>Mg>K>Ca whereas heavy metals followed the order:
Cr>Fe>Ni>Mn>Cu>Zn>Co>Pb>Cd. Factor analysis
based on principal component analysis, cluster analysis, and
correlation analysis identified contribution of metals from
tannery effluents, agrochemicals, automobiles exhaust, and
natural weathering processes. Tannery-affected soils were
enriched withCd followed by Cr, Pb, Ni, Cu, Co, Zn, and Mn.
Geo-accumulation index (Igeo) classified the soil samples in
unpolluted tomoderately polluted categories. Metal pollution
index provided better estimation of heavy metal pollution as
compared to pollution load index. Ecological risk index
showed high potential ecological risk associated with Cd and
Cr withmean concentrations above respective average shale/
background values. The results are useful for heavy metals
source identification, enrichment, risk assessment, and
management of tannery-affected soils and can contribute to
monitoring programs at regional levels.
Keywords
Cluster analysis; Ecological risk index; Enrichment indices; Factor analysis; Geo-accumulation
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