Environmental Engineering Reference
In-Depth Information
1 Introduction
The major sources of heavy metal contamination are industrial effluents, burning,
transport, power generation and organic wastes (Lone et al.
2008
). Particularly, in
Pakistan, industrial sewage water, unprocessed city effluents, and domestic wastes
are major sources to pollute the environment, which eventually enters in the food
chain thereby negatively affecting the environmental health (Qadir and Ghafoor
1998
; Stagnitti
1999
).
Metals are among the hazardous environmental pollutants which severely affect
growth and development of plants, in addition to causing toxic effects in plants and
animals (More et al.
2003
). In plants, tolerance mechanism of metal toxicity has
been reviewed largely (Clemens
2006
; Hossain et al.
2012
). It is vital to investigate
the relationships between plants and heavy metals for the safety of our environment
(Benavides et al.
2005
).
The occurrence of heavy metals like Ni, Cd, Cu, Pb and Zn is widespread these
days (Yadav
2010
). In higher plants, most widely studied metals are cadmium and
nickel, which tend to be commonly occurring toxic soil pollutants (Sanitá di Toppi
and Gabrielli
1999
; Madejón et al.
2003
). Many metals are proved to be toxic at el-
evated levels, which have been studied in several plant species, e.g.,
Salix acmophylla
(Ali et al.
2003
),
Pisum sativum
(Belimov et al.
2003
),
Azolla
sp. (Anju et al.
2004
),
Chlorella
(Rehman and Shakoori
2004
),
Corchorus olitorius
(Mazen
2004
),
Brassica
juncea
(Sridhar et al.
2005
),
Hordeum vulgare
(Sridhar et al.
2007
) and
Medicago
sativa
(Jadia and Fulekar
2009
). However, specific metals pose specific effects on
different species. The metals can cause alterations in a variety of physio-biochemicals
and structural attributes. Thus, the present chapter discusses how far metals can alter
various physio-anatomical features in different plant species and how these altered
attributes could help plants to survive under metal-enriched environment.
2
Soils Impregnated with Heavy Metals
Industrial effluents consistently degrading water resources and agricultural lands in
Pakistan. Ineffective industrial pollution control policies in addition to lack of im-
plementation of such activities are the major reasons. Only about 1 % industries in
the Pakistan are equipped with operating wastewater treatment plants (Bhatti
1996
),
while the other are causing a major threat to the environments by disposing off un-
treated solid as well as liquid wastes to soil and water resources (Shah
1987
). These
effluents enter in the irrigation water systems and ultimately pollute our agricultural
lands. A huge amount of contaminated waste-water is discharged daily from the
industries and in the absence of proper treatment plants, pollutes the water-bodies
(Saleemi
1993
). Toxic metals from industrial effluents ultimately accumulate in the
soil, causing toxicity in plants, and hence affecting the productivity. Crop plants can
uptake heavy metals entering into the food chain and as a result of utilization they
cause metal toxicity to humans and livestock (Albering et al.
1999
; Jarup
2003
).
