Plant Uptake/Bioavailability of Heavy Metals
from the Contaminated Soil after Treatment
with Humus Soil and Hydroxyapatite
Virendra Misra & Pranav Kumar Chaturvedi
Received: 6 June 2006 /Accepted: 30 October 2006 / Published online: 8 February 2007
# Springer Science + Business Media B.V. 2007
Abstract Uptake /bioavailability study using the
Indian mustard plant (Brassica juncea) was under-
taken at the interval of 7, 14 and 21 days to test the
immobilization of heavy metals from contaminated
soil that were amended with humus soil and/or
hydroxyapatite. For this, four sets consisting of non-
humus soil + metals (Cd, Cr, Ni and Pb), humus soil
+ metals, non-humus and humus soil in the ratio of
1:3 + metals and non-humus soil: humus soil in the
ratio of 1:3 + metals + 1% hydroxyapatite were
prepared. The bioavailability of Pb, Cd, Cr and Ni in
non-humus soil system was 58%, 67%, 65% and
63%, respectively in 7 days, more than 80% in
14 days and more than 90% in 21 days. Use of non-
humus, humus soil in the ratio of 1:3 and addition of
1% hydroxyapatite decreased the bioavailability of
lead around 21 to 22.5%, Cd 35 to 36%, Cr 25.5 to
26.9%, Ni 34 to 39% in 7, 14 and 21 days. Apart
from this increase in the fresh weight of the plant
was also noticed during the experiment. The data
showed that addition of 1% hydroxyapatite in the
non-humus-humus soil system caused the increase in
the fresh weight around 90% in 7, 14 and 21 days as
compared to plant grown in non-humus and metal
soil system.
Keywords Contaminated soil/sites . Humus soil .
Immobilization . Bioavailability . Remediation .
Heavymetals . Hydroxyapatite
1 Introduction
Release of heavy metals in soil as a result of industrial
and anthropogenic activities are known to have
potential impact on environmental quality and on
human health via ground water and surface water
(Rulkens et al. 1998). Non-ferrous metallurgical
industries and pyrometallurgical processes are the
main source for causing severe contamination of soils
(Adriano 2001). Moreover, concentrations of heavy
metals in soil may render them nonproductive
because of phytotoxicity and may cause bioaccumu-
lation of heavy metals in animals and human
exposure (Abdel-Sahab et al. 1994).
A contaminated site may be relatively stable but
there is always risk of mobilizing the contaminants by
volatilization or flushing (Romantschuk et al. 2000).
The technological solutions for treatment of contam-
inated sites are usually costly, ecologically unsafe and
many a times not practically feasible, especially in
developing countries. Among the various methods
employed earlier, the technique of in situ immobili-
zation is one of the key techniques for the remediation
Environ Monit Assess (2007) 133:169–176
DOI 10.1007/s10661-006-9570-5
V. Misra (*) : P. K. Chaturvedi
Ecotoxicology Section,
Industrial Toxicology Research Centre,
Post Box No. 80, M.G. Marg,
Lucknow, Uttar Pradesh 226 001, India
e-mail: virendra_misra2001@yahoo.co.in

of polluted soils. It reduces the risk of worker’s
exposure during remediation and is less expensive
and much less disruptive to ecosystem than conven-
tional ex-situ methods involving excavation and
treatment followed by disposal (Chen et al. 2000).
Immobilization limits the solubility of contami-
nants contained in the soil and blocks the pollutants
within the soil by process of precipitation, adsorption
or complexing metals (Mench et al. 1994). Plants are
important components of ecosystem as they transfer
elements from abiotic into biotic environments. The
bioavailability of elements to plants is controlled by
many factors associated with soil and climatic con-
ditions, plants genotype and agronomic management,
active/passive transfer processes, sequestration and
speciation, redox states, type of plant root system and
the response of plants to elements in relation to
seasonal cycles (Kabata-Pendias and Pendias 1992).
Mench et al. (2000); Mench et al. (2006) and
Vangronsveld et al. (1995) studied the effect of
several soil amendments on the growth of some crops.
Humic substances are the major organic fraction
in humus soils. Among the humic substances, humic
acids are natural organic macromolecules with
multiple properties and high structural complexity
and behave as supramolecules and form supramo-
lecular ensembles with other compounds (Steed and
Atwood 2000). Cheng and Hseu (2002) used differ-
ent soil amendments, including zeolite, bentonite,
Penghu soil, manganese oxide and silicate slag to
immobilize Cd and Pb in two contaminated soil.
The idea of treating the heavy metal contaminated
soils with phosphate has recently shown good
promise and has been proposed an alternative to
soil removal (Berti and Cunningham 1997; Ma et al.
1995). Apatite minerals such as hydroxyapatite
[Ca10(PO4)6(OH)2], are known to react with many
transition and heavy metals and metalloids to
rapidly form secondary phosphate precipitates that
are stable over a wide range of geochemical
conditions (Zhang and Ryan 1999). Hydroxyapatite,
as a metal immobilizing agent has been tested and
different indicator plant grown on amended soils
(Boisson et al. 1999). Several studies have shown
that treatment of synthetic hydroxyapatite phosphate
rock or phosphoric acid to contaminated waters and
soil effectively reduced lead contamination in
aqueous and soil solutions and resulted in formation
of pyromorphite, a compound characterized by very
low solubility (Ma et al. 1994; Seaman et al. 2001).
In the present study, the plant of Indian mustard
(B. juncea), which has the capacity to tolerate high
levels of heavy metals in soil, was used to investigate
the uptake/bioavailability of metals from the contam-
inated heavy metal soils that were amended with
humus soil and hydroxyapatite.
2 Materials and Methods
2.1 Chemicals
Hydroxyapatite [Ca10 (PO4) 6(OH) 2] obtained from
Aldrich Chemical Company Inc., Milwaukee, USA
was used as a metal immobilizing additive. Solid
metal salts CdCl2.H2O, (CH3COO) 2 Pb.3H2O,
NiSO4.7H2O, CrCl3.6H2O and other chemicals used
in the study were from E. Merck and AnalaR grade.
2.2 Collection of soil samples
In the present study, humus and non-humus soils
collected from orchard and non-orchard areas of
Gheru campus of ITRC were used for the preparation
of soil matrix. The soil samples were air-dried ground
and sieved through 60 mesh sieve pores to remove
unwanted material if any.
2.3 Preparation of soil samples and soil analysis
The soil samples were prepared by mixing non-humus
soil with humus soil in the ratio of 1:3 to obtain
optimal results for immobilization (Misra and Pandey
2004). The background levels of the metals in non-
humus/humus soils were Cd (0.09/0.15), Cr (1.9/
1.98), Ni (2.1/2.5), Pb (2.0/3.1) μg/g of soil respec-
tively. The cation exchange capacity of non-humus
and humus soil determined by the method of Hesse
(1971) was 14.72 and 44.32 meq/100 g soil, respec-
tively. The pH of the various soil combinations
ranged from 7.04 to 7.40.
2.4 Immobilization studies
For immobilization four sets consisting of (a) non-
humus soil + 100 ppm metals (Cd, Cr, Ni and Pb), (b)
humus soil+ metals, (c) non humus and humus soil in
the ratio of 1:3 + metals and (d) non-humus soil: humus
170 Environ Monit Assess (2007) 133:169–176