Download 4. HEAVY METAL ANALYSIS

4. HEAVY METAL ANALYSIS
4.1 INTRODUCTION
Heavy metals are important environmental pollutants and many of them are
toxic even at very low concentrations. Pollutants of the biosphere with toxic metal
has accelerated dramatically since the beginning of the industrial revolution
(Nriogo, 1979). The primary sources of the pollution are the burning of fossil fuels,
mining and smelting of metalliferous ores, municipal waste, fertilizers, pesticides and
sewage (Rao et al., 2006). According to Forstner and Prosi (1979) the harmful effects
of heavy metal as pollutant resulted from incomplete biological degradation.
Therefore these metals tend to accumulate in the aquatic environment. Since heavy
metals are non degradable they can be bioaccumulated by biological organisms, either
directly from the surrounding water or by the uptake of nutrients (Kumar and Mathur,
1991).
The metallic elements with atomic weight of more than 100 and those with a
relative density greater than 5 grams are considered as heavy metals. Of these Fe+,
Mn+, Cu+, Zn+ and Mo+ are considered as essential elements required in low
concentrations and Ag, Cd, Hg and Pb even at low concentrations are considered as
toxic heavy metals. They have permissible limit above which they are toxic
(Young, 2005 and Sreedhar et al., 2006). The toxicity of the metallic elements is
closely related with their position in the periodic table.
Heavy metal contamination of the environment is a worldwide phenomenon
and they cannot be estimated from the water body but they remain in the sediment,
released in the water, enter into the aquatic organisms including algae and
hydrophytes (Rai et al., 1981; Lovettdoust et al., 1994; Chowdhury and Blust, 2002).
The structure and potentiality of the aquatic ecosystem is modified by heavy metal
and
once added to the environment they are not easily converted into something
harmless but accumulated in the tissues especially in the food chain of the organism
Weis et al., 2001 and Mohamad, 2005). The severity depends upon the concentration,
accumulation and also the bioavailable forms (Madu et al., 2007).
Much work has been carried out in India regarding the occurrence of
heavy metals in lentic water bodies causing a sharp increase in pollution,
(Kaushik et al., 1999; Sivakumar et al., 2000; Deora and Suhalka, 2006). Aquatic
animals, algae and hydrophytic weeds absorb heavymetals through their roots, shoots,
leaves or through their body and function as a carrier (Jackson, 1998). As the
macrophytes die and decayed the accumulated metals sink in the bottom sediment and
increases the concentration of metal (Ravera, 2001).
The aquatic environment with its water quality is considered as the main factor
controlling the status of health and disease in both man and animal Nowadays the
increasing use of waste chemicals and agricultural drainage systems represent the
most dangerous chemical pollution The most important heavy metals deposited in the
sediments are zinc, copper, lead, cadmium, mercury, nickel and chromium. The main
sources are natural, industrial, domestic wastes, agricultural, surface mining process,
runoff and atmospheric pollution (Pergent and Martin, 1999).
Aquatic macrophytes are unchangeable biological filters that accumulates
heavy metals in their tissues and act as an efficient accumulator of heavy metals.
Among the plant parts root system shows higher concentration of heavy metals like
Ca, Fe, Al,Cr,Cu,Ba,Ti, Co and Pb. Heavy metals like Mn,Zn, and Mg were deposited
in the stem. Calcium showed maximum accumulation in leaves and less in flowers
(Kara et al., 2000; and Khan et al., 2000).
Several aquatic plants grow luxuriously with the rich supply of nutrients
(HO, 1998). Many of the submerged, emergent and free floating aquatic plants
were reported to accumulate heavy metals and function as potential scavengers
(Gulati et al.,1979). It was proved that aquatic plants can play a significant role in
transportation of metals from the surroundings upto the shoot systems. They are of
almost ecological and economical importance and they contribute significantly the
productivity of an aquatic ecosystem and mobilize the mineral elements from the
bottom sediment. Most of them become a nuisance when growing profusely and they
are termed as “Weeds” (Misra and Tripathi, 2000). In general, they are known to
remove metals by surface absorption and incorporate them into their own system or
stored in a bound form. It depends on the kind of metal and the species of plant
(Cymermaon and Kempors, 1996).
Aquatic plants provide a valuable alternative source for metal remediation
(Jackson, et al., 1994). Ali and Soltan (1999) used the free floating Eichhornia
crassipes, non-rooted submerged Ceratophyllum demersum and rooted submerged
Potomogeton crispes for assessing heavy metals. Aquatic plants from world wide had
received extensive interest as biomarkers of water pollution with metals (Gupta et al.,
1994). They serve as a primary source for metal accumulation (Mouvet et al., 1993).
Revera et al. (2003) and Ramdon (2003) has reported the trace metal
concentration in several freshwater macrophytes. Bioaccumulation of macro and
micro elements in Typha angustiana and Phragmites australis were assessed by
Baldantoni et al. (2005). Nickel content in Lemna was reported by Kara et al. (2003).
Salvinia sp. were used by Khosravi et al. (2005) for removing heavy metals. High
levels of heavy metals such as Al, Fe, Si, Mn were found in Vallisneria spiralis,
Hydrilla verticillata and Azolla pinnata.
Phytoaccumulation of heavy metals by
selected freshwater macrophytes were also studied to assess the phytoremediation of
six heavy metals in Narsarovar Bird sanctuary (Kumar et al., 2006).
Algae like Chlorella absorb heavy metals from the aquatic environment and
involved in metal stress Cho et al. (1994). Prakash and Balasingh (2007) have studied
the accumulation of lead and chromium by the filamentous algae Oedogonium.
Shin et al. (2002) has reported that algae as a good source of absorbent for Arsenite
compounds. Kitturmath et al. (2007) has reported the bio-accumulation of Fe, Cr, Cu,
Zn and Pb by Riccia fluitans. Cadmium toxicity was removed from the waste water
using Cladophora sp. (Sternberg and Dorn, 2002).
Kara et al. (2003) has proved that wetland plants possess higher capacities in
accumulating trace elements like Cu, Ni, Zn, Pb etc. Lemna minor, Eichhornia
crassipes were found as good accumulators of Cd, Si and Cu. Laboratory studies on
E. crassipes proved the potentiality of removing metals from polluted water and have
shown that metal concentration of the plant and the water columns are correlated
(Sharshar and Haroon, 2009).
Physiological responses on Hydrilla sp, Nasturtium
officinale, E. crassipes and Lemna major act as good accumulators of Pb, Cu, Fe and
Cd (Yu et al., 2008). Baldantoni et al., (2004,) has pointed out the micronutrient
deposition in Typha angustata and Phragmites australis in relation to the spathial
gradients of lake. Metals like Cd, Zn, Hg and Cr removed by Azolla corolinianata, A.
filiculoides and A. pinnata (Roy et al., 1992, Zhao, 1998 and 1999; Roy, 2003 and
Benicelli, 2004).
Several diseases including brain damage to human beings are caused by the
low concentrations of heavy metals which enter through the food chain mainly
inhibition of enzymes, metabolic disorders, genetic damage, cancer and even
hypertention (Brajesh and Mascred, et al., 2007). Studies on biomonitoring
distribution and concentration of heavy metals in vegetables collected in and around
Gujarat was carried out by Kumar et al. (2004).
From aquatic and terrestrial
ecosystems high levels of Cd, Cu, Pb, and Fe were observed as ecological toxins
(Guillizzoni, 1991 and Kumar, 1997).
Many industrial and mining processes cause heavy metal pollution which can
contaminate natural water systems and become a hazard to the health of animals,
plants and humans. Therefore, growth of aquatic macrophytes in freshwater system,
with heavy metal and their transportations are important. In view of luxurious growth
of aquatic weeds in Kanyakumari district the present investigation was planned to find
out the efficiency in bioaccumulation of heavy metals by the sediments, water and
selected aquatic weeds were undertaken.
4.2 Materials and Methods
Water and sediment sampling
Surface water and composite sediment samples were collected from the
experimental ponds (P1 – P8) during April 2009. Soon after collection, the water
samples were filtered through 0.45 µm Millipore filter paper and preserved in plastic
bottles by the addition of a few drops of nitric acid. Sediment samples were preserved
in air dry plastic bags neatly labeled and brought to the laboratory for further analysis.
Plant sampling
Eight dominant aquatic macrophytes (Trapa natans, Hygrophila auriculata,
Utricularia gibba, Jussiaea repens, Azolla pinnata, Salvinia molesta, Ceratopteris
thalictroides and Marsilea minuta) from the experimental ponds were selected for
estimating the toxicity status of heavy metals like Zn, Cu, Cr, Pb and Cd. They were
washed well with water to remove all the periphyton and sediment. They were
labeled and brought to the laboratory. Plant species were identified according to Shah
(1978a, 1978 b).
Laboratory work
Chemical analysis of water, sediment and plant samples
The air dried sediment samples were sieved through 2mm governorate sieve
and kept for analysis 50 gm of each fresh aquatic sample was dried at 800 in a hot
oven for 48 hours.
The sample of water, sediment and plants were chemically
analyzed for the detection of heavy metals (Zn, Cu, Cr, Pb and Cd). Accurately 0.5
gm of dry powder of each sample was weighed and digested with conc. HNO3,
H2SO4 and H2O2 (2:6:6) as prescribed by Saison et al. (2004). Towards the end of
digestion 20 ml of deionized water was added and cooled. The final volume was
made into 50 ml. The chemical analysis was carried out in a Perker Flame 2380.
Atomic Absorption Spectrophotometer.
Analyses were done in triplicates and
calculated in ppm.
Statistical analysis by two way ANOVA was used to find out the significant
influence of heavy metals between sediments, water and plants respectively
(Zar, 1974).
Description of the selected aquatic weeds
Class
:
Dicotyledons
Order
:
Lythrales
Family :
Trapaceae
Genus
Trapa
:
Species :
natans L. Var. bispinosa Roxb.
It is a free floating hydrophyte with rosette leaves having rhombic blades with
serrate margins. Upper surface is glossy and the lower is pubescent. The petiole
provides a spongy aerenchymatous swelling near its apex. The leaves are transversely
heliotropic. The flowers are white and open above the surface of water. Flowers are
hermaphrodite, axillary and solitary. Fruit is a large one seeded spiny nut with four
angles and non-endospermic. Seeds angular, cordate and endosperm with unequal
cotyledons. It is commonly called as “water chestnut”. During February – April the
plants occupied in most of the ponds as a dominant weed (Plate 3).
Class
:
Dicotyledons
Order
:
Personales
Family :
Acanthaceae
Genus
Hygrophila
:
Species :
auriculata (K. Schumacher) Heine
It is a perennial semi aquatic herb with thick stems bear long, sharp, axillary
thorns on the nodes. Leaves narrow, simple in spurious whorls of six thorns and eight
leaves, the outer most leaves longer lanceolate to linear – lanceolate, 5 – 10 cm long
and 1.5 – 2.5 cm wide, tips acute, thorns upto 3 cm long. Flowers are axillary whorls,
usually surrounded by spines. Bracts and bracteoles are present. Sepal tube 4 lobed,
petals blue, purple or pink, glabrous upto 2.5 cm long. Stamens are 2 pairs, one pair
is short and the other pair is long (10 mm long). Anthers are unequal. Seeds 4 – 8
orbicular. The entire plant is used for urinary problems and for dropsy. This plant
occupied along the margins of the pond and collected throughout the study period
(Plate 3).
Class
:
Dicotyledons
Order
:
Personales
Family :
Lentibulariaceae
Genus
:
Utricularia
Species :
gibba Linn
It is submerged or floating hydrophyte, rootless and insectivorous. The leaves
are often dimorphic with submerged leaves finely divided and bearing insectivorous
bladders. The bladders are thus metamorphosed in ultimate leaf segments meant for
catching the aquatic small insects. Capitate glands are found on the surface of leaf.
Flowers are bractiate, bisexual, zygomerphic and hypogynous. Sepals five and
gamosepalous.
Corolla consists of 5 petals, gamopetalous, united in bilabiate.
Stamens two arising from the extreme base of corolla tube, anthers are monothecous.
Gynoecium consists of 2 carpels, syncarpous with superior ovary. Fruit is a capsule.
Seeds are small and ex-endospermic. It was collected from P4 and P6 as a dominant
weed gives shelter to several protozoans (Plate 4).
Class
:
Dicotyledons
Order
:
Lythrales
Family :
Onagraceae
Genus
Jussiaea
:
Species :
repens Linn. (Ludwigia adscendens (L.) Hara).
The plants are aquatic herbs, creeping on the surface of water and floating by
means of white spongy, aerenchymatous, breathing roots formed in whorls at the
nodes of the main stem. Leaves are alternate, simple and exstipulate. Flowers are
white, axillary and solitary, pedicels with 2 bracteoles. Calyx tube is narrow and
persistent. Petals 4, epigynous, alternate with the calyx lobes. Stamens are four and
inserted with them. Carpels 4, ovary inferior, ovules anatropous, style simple and
short. Stigma usually capitate. Fruits linear with numerous seeds. It is a common
weed found throughout the study period in all the experimental ponds (Plate 4).
Class
:
Leptosporangiopsida
Order
:
Salviniales
Family :
Azollaceae
Genus
Azolla
:
Species :
pinnata R.Brown
Azolla pinnata is a heterosporous fern widely distributed in all the
experimental ponds as a free floating hydrophyte. The sporophytes are small in size
with branched stem covered by small leaves which are divided into two equal lobes.
They are dark green and thick.
The ventral lobe is thin almost colourless and
submerged. Roots are adventitious. Small sporocarps are borne on fertile branch. It
grows luxuriously during November – April months and produce sporocarps during
summer months. It is a bio-fertilizer, a weed controller and a good phytoremediator
(Plate 5).
Class
:
Leptosporangiopsida
Order
:
Salviniales
Family :
Salviniaceae
Genus
Salvinia
:
Species :
molesta Mitchell
It is a perennial free floating aquatic heterosporous pteridophyte.
The
sporophyte has a herbaceous, branched, horizontal and floating rhizome. The stem
bears numerous multicellular hair and “sharp pointed terminal cells”. The leaves arise
in clusters of three. Two leaves of the cluster are above the surface of water and the
third one is submerged. The floating and submerged leaves differ in morphology, the
farmer being green and hemispherical in shape. Their upper surface is papillose and
covered with stiff hairs that save it from being wetted. The lower surface is brownish
and also covered with hair of the same colour. The submerged leaves are long and
filiform. They appear like roots and most probably act as balancers. Bean shaped
sporocarps are borne at the tip of the segment. The sporocarps are sympodially
arranged (Plate 5).
Class
:
Leptosporangiopsida
Order
:
Filicales
Family :
Parkeriaceae
Genus
Ceratopteris
:
Species :
thalictroides Linn. Brongniart:
It is an aquatic homosporous fern rooted in the marshy mud. The sporophytes
are branched, dissected, pale green to dark green in colour. The rhizome is sparingly
branched and covered with scales. Stem slender and fleshy with a crown of leaves on
its upper surface.
dimorphic.
Petioles are long slender and broad at the base.
Sterile leaves are submerged, floating or emergent.
2 – 4 times pinnate. The ultimate segments are elongated (Plate 6).
Class
:
Leptosporangiopsida
Order
:
Marsileales
Family :
Marsileaceae
Genus
Marsilea
:
Species :
minuta Linn
Leaves are
Fertile leaves
It is an amphibious heterosporous fern. The sporophyte looks with four leaved
clefted plant. It is differentiated into roots, stem and leaves. The stem is long, slender
and runner. It creeps either on the surface with stolon. Roots are adventitious. The
stem is divisible into distinct nodes and internodes and is branched. The branches
arise at the bases of leaves and are extra axillary in position. The branching is
monopodial. The leaves arise from the upper side of the stem which is divided into
four leaflets of same size. Marsilea reproduces vegetatively by fragmentations as
well as by means of sporocarps. They are edible because of their nutritious value and
the entire plant was used as good, tastier vegetable. In P1 and P2, it almost occupied
the entire margin of the pond (Plate 6).
4.3 Results
The accumulation of zinc, copper, cadmium, chromium and lead from the
sediments, water and selected aquatic weeds were studied and their results are given
below.
Zinc (Zn)
The concentration of the elements in the sediment was higher than water.
Among the samples analyzed zinc was the most abundant element observed from the
eight experimental ponds.
From the sediment, water and selected aquatic weeds the deposition of zinc
content was analyzed and the results are provided in Fig. 4:1-4. The maximum
amount of zinc concentration (6.66 ± 0.23ppm) was recorded in the sediment of P1
and minimum of 0.19 ± 0.05ppm was observed in P7. Water analysis indicated higher
and lower concentration of 6.10 ± 0.52ppm and 0.07± 0.02ppm in P1 and P7
respectively. Analysis of zinc from the aquatic weed Salvinia molesta and Jussiaea
repens accumulated 6.24 ±0.61ppm and 0.78± 0.26ppm as maximum and minimum
concentrations. The ratio between zinc concentration in the sediments and water was
lower 1.175 pm (Fig.4:1-4).
Copper (Cu)
The results on copper content detected from the sediment, water and
macrophytes are shown in Fig. 4: 1-4. The sediments collected from P3 showed
5.75 ± 0.68 ppm of copper content as highest value against the lowest of
1.14 ± 0.19 ppm in P8. Water analysis indicated maximum of 2.98 ± 0.95ppm of
copper in P3. The ratio of copper in the sediment and water samples showed lower
values of 1.780 ppm. The minimum concentration of (0.25 ± 0.1 ppm) was reported
from P8. The entire Marsilea minuta and Hygrophila auriculata have showed the
highest and lowest concentrations of 2.32 ± 0.58 ppm and 1.21 ± 0.17 ppm of copper
respectively.
Chromium (Cr)
Among the eight ponds the maximum accumulation of chromium reported was
from the sediment of P1 with 5.90 ± 0.89 ppm and minimum of 1.62 ± 0.05ppm from
P4 (Fig. 4:1-3). The highest and lowest amount of chromium was found in the water
of P5 with 2.99 ± 0.97ppm and 0.86 ± 0.06ppm in P4 respectively. The ratio of
(Fig.4:1-4) chromium concentration between sediment and water was higher than the
other heavy metals (2.324 ppm).
The quantity of chromium accumulated in
Ceratopteris thalictroides was found to be the highest of 1.70±0.60ppm whereas
lowest of 0.02±0.01ppm was observed in Azolla pinnata.
Lead (Pb)
The results obtained on lead content deposited from sediment, water and
aquatic macrophytes during the study period is displayed in Fig. 4:1-4. The
concentration of lead recorded in the sediment was maximum of 5.40 ± 0.31ppm in P1
and minimum of 1.79 ± 0.21ppm in Pond 4. The highest quantity of 2.92 ± 0.40ppm
of lead was noticed in the water of P1 against the lowest of 0.47 ± 0.06ppm in P3.
The ratio between the element concentration of lead in the sediment and water was
2.300 ppm (Fig. 4:1-4). The maximum of 0.76 ± 0.11ppm of lead contents were
observed by Marsilea minuta and the minimum concentration of 0.02 ± 0.01ppm was
noticed in Jussiaea repens and Azolla pinnata.
Cadmium (Cd)
The highest amount of cadmium detected in the sediment sample was
0.04±7.21ppm in pond 7 and the lowest amount of 0.01 ± 7.15 ppm was recorded in
P1. The cadmium concentration obtained from the water reached higher level
(0.03 ± 0.01ppm) in P8 against the low level of 0.01 ± 0.01ppm in pond 5. The ratio
of cadimium between sediment and water was 1.375 (Fig.4:1-4).
The order of
distribution was decreasing according to the sequence Cr > Pb > Cu > Zn > Cd.
Utricularia gibba and Azolla pinnata showed the highest and lowest concentrations of
0.02 ± 1.66 ppm and 0.01 ± 1.48ppm respectively (Fig. 4:1 - 4).
Among the five heavy metals Zinc accumulation was highest (6.24 ppm) by
Salvinia molesta Copper was more abserved by Marsilea minuta, whereas chromium
was more deposited (1.70 ppm) in the plant body of the aquatic fern Ceratopteris
thalictroides. However lead and cadmium were less accumulated by the tissues of
Marsilea minuta (0.78 + 0.02 ppm).
The accumulation of heavy metals by the selected aquatic weeds showed a
decreasing trend as follows.
Zn – S. molesta > T. natans > A. pinnata > H. auriculata > C. thalictroides >
M. minuta > U. gibba > J. repens.
Cu – M. minuta > S. molesta > T. natans > U. gibba > A. pinnata > C. thalictroides
> H. auriculata > J. repens.
Cr – C. thalictroides > M. minuta > H. auriculata . T. natans > U. gibba > S. molesta
> J. repens > A. pinnata.
The heavy metal lead and cadmium was accumulated less than 1 ppm by the
experimental plants.
Statistical analysis (Table 5) on two way ANOVA on sediment revealed a
significant influence between ponds (F = 2.5582; P < 0.05) and between heavy metals
(F = 9.442; P < 0.05). Analysis of water showed a non-significant deviation of
(Table 5.1) between ponds and a significant influence between heavy metals
(F = 3.749; P < 0.05). Two way analysis of variance (Table 5.3) tests reported a
significant influence of aquatic weeds in the accumulation of heavy metals. (F =
18.8573; P < 0.05).
4.4 Discussion
Aquatic macrophytes are used to carry out purification of water bodies by
accumulating dissolved metals and toxins in their tissues. They play a significant role
in removing the different metals from the ambient environments and reducing their
effect of higher concentration of heavy metals. Hence they are known as ‘carriers’
and helps in phytoremedaiation in saving the aquatic environment from pollution
(Nidemele, 2003; Nidemele and Jimoh, 2010 and Nidemele et al., 2011). The
accumulation of zinc, copper, chromium, lead and cadmium were analysed from
sediment, water samples and selected aquatic weeds of the experimental ponds which
showed the descending order as Zn > Cu > Cr > Pb > Cd. The deposition of zinc was
more and cadmium was less in all the samples.
Heavy metals produce undesirable effects even if they are present in extremely
minute quantities on human and animal life.
Several studies have shown that
constructed wetlands are very effective in removing heavy metals from polluted waste
waters (Win et al., 2002). Different wetland species differ however in their abilities to
take up and accumulate various heavy metals. Members like Lemna minor, Eichhornia
crassipes and Nasturtium officinale were reported as excellent accumulators of Pd, Cu,
Cd and Ni (Zhu et al., 1999; Kara et al., 2003; 2004 and Kara, 2005).
In general,
sediment and aquatic macrophytes provide the information of heavy metal
concentrations in the aquatic environment (Demirezen, 2004). Among the heavy
metals studied zinc is one of the essential micronutrients required for plant
metabolism but when it exceeds the limit, it become extremely toxic (Bruins et al.,
2010). It is a ‘masculine’ element that balances copper in the body and essential for
male reproductive activity and serves as a co-factor for dehydrogenating enzymes
particularly in metabolic cycles (Holum, 1983 and Abbasi, et al., 1996). Texture of
sediment plays a key role in the zinc content (Koshy and Nagar, 2002). Shailaja and
Johnson (2006) observed that the most common zinc mineral is Sphalerite (ZnS)
which is often associated with the sulfides of other metallic elements. Zinc occurs
naturally in air, water and soil due to the industrial activities such as coal mining,
waste combustion and steel processing. Zinc can enter the aquatic environment from
a number of sources including sewage effluents, run off from the nearby coconut,
rubber, agricultural fields and detergents (Boxall et al., 2000; Madu et al., 2007).
The extents of accumulation vary with pH, additives like sodium chloride, cell age
and concentration of metal (Jasmine and Sasikumar, 2006).
In the present study zinc content of the sediment varied from 0.19 ± 0.05 ppm
(P7) to 6.66 ± 0.23ppm (P1) which is similar to the result obtained by Kumar
et al. (2008) in the freshwater ecosystems. Egila and Nimyel (2002) observed
maximum of 9.2 mg/l of zinc concentration in their studies. A decrease in
its concentration was reported from the sediment (pond 7) and water (0.07 ± 0.02
in P7) as the pond is not surrounding by agriculture fields. Moreover the pond with
luxurious growth of Eichhornia crassipes which possess a unique capacity to absorb
large amount of zinc as reported by several workers. (Sridevi et al., 2003). A higher
concentration reported from the water samples of P1 was 6.10 ± 0.52ppm and this
may be due to the entrance of zinc based fertilizers from the near by paddy and
banana fields. In the present investigation Trapa natans, Hygrophila auriculata,
Utricularia gibba, Jussiaea repens, Azolla pinnata, Salvinia molesta, Ceratopteris
thalictroides and Marsilea minuta were reported for the accumulation of heavy metals
like zinc, copper, chromium, lead and cadmium. Among the aquatic plants the free
floating Salvinia molesta was found with heavy accumulation of zinc (6.24 ppm) and
Jussiaea repens with least bio accumulation. Lemna minor (Jafari and Akhavan,
2011) and Eichhornia crassipes (Kumar, 2007) the two free floating macrophytas
were noticed with high level of zinc deposition. Srivastava and Jain (1998) has
reported that the mobility of zinc was faster than other heavy metals in Ceratophyllum
demersum. Similar to Jussiaea repens of the present report Lemna minor and Riccia
fluitans accumulate lesser concentrations of zinc (Cecal et al., 2002). Potamogeton
natans and Elodea canadensis were observed with the heavy metals of Zn, Cu, Pb and
Cd in their tissues and in the sediments of aquatic ecosystem (Nwajei and Gagophien,
2000).
In general, zn deficiency causes anaemia and retardation of growth in animals.
In excess it can cause system dysfunctions that result in impairment of growth, birth
defeats and reproduction (Mccluggage, 1991). The clinical sign of zinc toxicities have
been reported as vomiting, diarrhea, liver and, kidney failure in human beings
(Fosmire, 1990).
In general zinc occurs in nature as Zinc blend, Zinc sulphide, silicate, Zinc
span, Zincite etc. It plays a key role in the metabolic cycles and a structural element
in a variety of enzymes.
Copper is an essential trace element for both plants and animals
(Forstener and Williams, 1981). It is a key component for the synthesis of
haemoglobin in vertebrates and haemocyanin of invertebrates .In plants, it is element
essential for photosynthesis, respiration, seed production, disease resistance,
regulation of water, carbohydrate and nitrogen balance. Copper normally occurs in
drinking water from copper pipes, and utensils, Copper sulphate is a common
fungicide. It serves as a cofactor of enzyme systems for most living organisms
(Obasohan, 2008). It reduces photosynthesis rates and respiration of aquatic moss
Hyophila involuta (Deora and Suhalka, 2006). Bioaccumulation of Cu is related with
toxicity and pH of water and it is a determinant factor. (Carvalho, 2004). Binning
and Baird (2001) reported higher values of Cu from the aquatic system of industrial
areas.
In the present observation presence of copper was less accumulated
(1.14 ± 0.19 ppm at P8) in the sediment and similar findings were reported by several
workers
(Kaushik et al., 1999. Khellaf and Zerdaouri (2009), Tharadevi and
Santhakumari, 2005). Sewage contains large quantities of dissolved organic matter,
which promote the mobility of copper. The maximum amount of copper detected was
5.75 ± 0.68ppm in the sediment of P3 which was mainly by the leaching process from
the near by agriculture fields. Similar findings were observed by Shrivastava and Jain
(1998), Baligar and Chavadi (2005) in their studies on Cu in the sediment from
aquatic environments.
In water low concentrations of Cu was found as 0.25 ± 0.01ppm (P8), which
was due to the bioaccumulation by Eichhornia crassipes as pointed out by Kannan
and Ramasamy(1993), Nagaraju et al.(2003), Sridevi et al. (2003) and Ida (2005)
Present study also revealed the accumulation of copper in higher quantities of
2.98 ± 0.95 ppm in the water samples of P3 which was due to the surface run off
which coincides with the observations made by Gray and Becker (2002). Mohan Raj
(2001) observed much higher values in his study which was due to the pollution
of few heavy metals and other chemical constituents. Kumar et al., (2008) noticed
the accumulation of heavy metal in the sediment was in the descending order as
Zn > Cu > Pb > Ni > Co > Cd. Copper occurs in nature in several oxides, carbonates,
sulphides, sulphates and other compounds. It also occurs in association with organic
matter, oxides of iron and manganese, silicate, clays and other minerals. (Taylor an
Crowder, 1983).
In the present observation, the concentration of Cu was low in Hygrophila
auriculata (1.21 ± 0.17ppm) and high (2.32 ± 0.58ppm) in Marsilea minuta. Lemna
minor (Pillai, 2010) and Azolla pinnata (Rai and Tripathi, 2009) were reported with
minimum quantities. Kara (2005) reported Ceratophyllum demersum accumulated
high amount of Cu which was mainly due to the mixing of agricultural run off and
sewage disposal. It was also noticed by Jain et al. (1989) and Gupta et al. (1994) that
heavy metals were accumulated more by Lemna minor and Bacopa from the waste
water. Shobha and Noorjahan (2010) noticed that sewage waste water ecosystem
with Eichhornia sp. accumulated large quantities of copper in their leaves Begum and
Harikrishnan (2010) have grown Hydrilla verticillata, Elodea canadensis and Salvinia
sp. with 5mg/l solution and they have resulted 95% of copper was removed by
Hydrilla and Elodea from water. In several ways most of the plants suck copper as
maximum. The ratio between sediment and water in the present observation was 1.78
(Fig.4:1-4 ). When compared with other heavy metals, copper was found with more
toxic effects on the growth and development of plants (Sharma and Gaur, 1994).
Copper affects the oxidizing system of cell and enzymes (Vardanyan et al., 2008).
Cardwell et al. (2002) and Nunez et al. (2011) reported the highest Cu concentration
was in the leaves of emergent plants (34 µg. g-1) and less by the roots (1,571 µg. g -1).
Pip (1990); Lewis, (1995); Saygideger, (2004) and Kumar, (2007) has studied the
accumulation of trace elements in the sediments, water and species like Eichhornia
crassipes, Echinochloa colonum, Hydrilla verticillata, Ipomea aquatica, Nelumbo,
nucifera, Typha angustrata and Vallisneria spiralis and other macrophytic weeds.
Based on their toxicity and concentration status observed in the vegetation, the metals
were in the descending order as Zn > Cu > Ni > Cd > Co > Pb. In the present
investigation also zinc and copper deposition was more in the sediment, water,
Salvinia molesta and Marsilea minuta.
Chromium occurs naturally as a insoluble heavy metal, however weathering,
oxidation and bacterial action can convert it into a soluble form. Municipal waste
water including gas, oil and coal combustion as well as metal industries releases
considerable amount of chromium into the environment (Raj, 2009) Chormium is
non toxic to humans (Shailaja and Johnson, 2006).
Gopalasamy et al. (2006)
observed that the absorption of Cr in the biomass is mainly due to the ionic attraction
between biomass and metal ions. Anthropogenic sources of Cr has become very
significant in recent decades and their contributions exceed those of natural sources.
In the present investigation chromium content in the sediment varied from
1.62 ± 0.50 ppm (P4) to 5.90 ± 0.89ppm (P1) which is similar to the results obtained
by Baligar and Chavadi (2005) in the freshwater ecosystems. The high amount of
Cr was mainly from the automobiles and pharmaceuticals industries (Srinivas, 1998;
Sudha and Backyavathy, 2006). In the present study, low concentration of Cr was
found in water (0.86 ±0.06ppm in P4) which was due to its low solubility, which is in
line with the finding of Pandey et al. (1995). Earlier studies of Shrivastava et al.
(2003) have reported the enrichment of chromium in particulate matter which may be
due to the mixing of domestic and industrial waste inputs. This in turn results low
dissolved oxygen content with H2S formation by bacterial activity. Maximum
concentration (2.99 ± 0.97ppm at P5) of Cr found in water was similar to the earlier
reports of Espinoza–Quinones et al. (2005).
Among the macrophytes studied chromium accumulation was low
(0.02 ± 0.01ppm) in Azolla pinnata and high (1.70 ± 0.60ppm) in Ceratopteris
thalictroides. Moreover marshy plants are known to absorb and accumulate more
heavy metals from contaminated water and sediment (Burke et al., 2000). In P5
Ceratopteris thalictroides flourish well as the pond receives heavy contaminated
water from the nearby hotels, agricultural and banana fields. The non-living Azolla
filiculoides was shown to be the effective adsorbant of chromium, zinc and nickal
(Zhao et al., 1998, 1999). Azolla caroliniana remove chromium, from the municipal
waste water. (Bennicelli et al., 2004). Wilson and Moore (1997) reported low
concentration of Cr in Ceratophyllum demersum and high content of Cr in
Elodea densa. This was mainly due to the metal availability factors, age of the
plants used, interference of other metals or differences in tolerance between
populations. Chromium’s effects on algae, duckweed, water hyacinth and water
lettuce
have also been studied (Satyakala and Jamil, 1992)
Spirogyra
sp.,
Oedogonium, Oscillatoria suncta and Lyngnbya were reported with chromium in the
river system of Thambraparani (Prakash and Balasingh, 2007). Excess of Cr leads to
occupational renal failure, dermatitis and pulmonary cancer whereas its deficiency
leads to impaired glucose tolerance, peripheral neuropathy and confusion (Dalvi et al.,
2007) Diseases like chrome hold ulcer, nasal perforation, gastrointestinal disorders
and respiratory ailments among chromate and tannery industrial workers have
reported (Backyavathy, 1986; Backyavathy and Nandakumar, 1992).
Lead is a toxic heavy metal accumulated in plant and animal tissues through
ingestion by food, water and inhalation. (Ferner, 2001) Lead sulphide or galena (PbS)
is the common form of lead. The main source of lead in the sediment is from lead
pipes, mixing of gun power, waste batteries, etc. into the aquatic systems, which
causes lead deposition. In the present observation, lead deposition was maximum of
5.40 ± 0.31ppm in the sediment of P1 and exceeds the permissible limit. According to
Gupta (2006) the limit of lead concentration is 0.01ppm. The high concentration of
lead coincides with the result of Vieschuver (1999) and Ida (2004) in the different
lentic systems. The concentration in water also remains high (2.92 ± 0.40 ppm in P1).
The main source of lead in water may be from contaminated wastes and also from the
corrosions of lead pipes. The influence of lead accumulation in plant tissues showed
maximum concentration in the root system of aquatic macrophytics and reported as
ecological toxins. Baldantoni et al. (2004) reported that the shoots of Najas marina
shows higher concentrations of lead. Saygideger et al. (2004) reported that the lowest
lead values were found at pH 5.0. The minimum Pb concentrations were determined
in Typha latifolia leaves, whereas Ceratophyllum demesum was observed
with
higher concentrations of lead at pH 7.0. Eichhornia crassipes and sediments of lakes
are indicated with higher concentration of lead
(Dixit and Tiwari, 2007). Lead
accumulation in the present study was low (0.02 ± 0.01 ppm) in Azolla pinnata and
Babovic et al. (2010) observed the
leaves of Phragmites
communis
was
accumulated with less concentration of lead. In the present observation, Marsilea
minuta accumulated maximum concentration of lead (0.76 ± 0.11ppm). Pillai (2010)
observed maximum concentration of lead in Lemna minor. Aquatic plants like algae,
mosses, and sediment of lakes were observed with lower concentrations of lead and
the present study coincides with the observation of Verschuver (1999). Lenntech
(2004) reported that lead affects brain growth, and poor intelligence. Acute and
chronic effects of lead result in psychosis. It also affect cardiovascular system,
synthesis of haemoglobin, kidney failure and central nervous systems. (Ogwuegbu
and Muhangu, 2005)
Cadmium is considered as one of the most ecotoxic metal that exhibits adverse
effects in all biological processes of humans, animals, plants and has an adverse effect
in the environment. In the present study, cadmium content in the sediment varied
from 0.01 ± 0.88 ppm to 0.04ppm which is similar to the result obtained by Baligar
and Chavadi (2005) and Kumar et al. (2008) in the freshwater ecosystems. Moreover
low concentration of Cd was observed in water (0.01 ± 0.01) of P5 as the pond does
not have any anthropogenic activities and similar observations were made by Jain and
Salmon (1995). Stoltz and Greger (2002) observed that cadmium act as a water
pollutant which will be given more weightage since it causes several adverse
damaging effects on human body through its accumulation. In the present study
analysis of cadmium accumulation by hydrophytes indicated that the low and high
content was observed by Azolla pinnata (0.01ppm) and Utricularia gibba (0.02 ppm).
Kumar et al. (2006) reported low concentration of cadmium in Ipomea aquatica and
maximum concentration in Vallisneria spiralis. Babovic et al. (2010) reported that the
tissues of Hydrocharis morsusranae contain highest concentrations of cadmium. He
also found that concentration of cadmium was high in the stalk of Typha latifolia,
while a lowest concentration of cadmium was found in the leaves of Nuphar lutea.
Whereas its concentrations were equal in roots and in the shoots of Najas marina
(Markert, 1992). Saumayata et al. (2007) reported that the adsorption potential of
dried biomass of E. crassipes was excellent for the removal of cadmium and
chromium. Even in low levels it is toxic to humans affecting the function of whole
body dysfunction. High exposure produces chest pain, cough with foamy and bloody
sputum and death of the lung tissues because of excessive accumulation of watery
fluids. Like other terrestrial plants aquatic weeds were also involved in the
bioaccumulation of heavy metals.