An investigation of arsenic contamination in Peninsular Malaysia based on Centella asiatica and soil samples

Abstract

The first objective of this study was to provide
data of arsenic (As) levels in Peninsular Malaysia based
on soil samples and accumulation of As in Centella
asiatica collected from 12 sampling sites in Peninsular
Malaysia. The second objective was to assess the accumulation
of As in transplanted C. asiatica between control
and semi-polluted or polluted sites. Four sites were
selected which were UPM (clean site), Balakong (semipolluted
site), Seri Kembangan (semi-polluted site) and
Juru (polluted site). The As concentrations of plant and
soil samples were determined by Instrumental Neutron
Activation Analysis. The As levels ranged from 9.38 to
57.05 μg/g dw in soils, 0.21 to 4.33 μg/g dw in leaves,
0.18 to 1.83 μg/g dw in stems and 1.32–20.76 μg/g dwin
roots. All sampling sites had As levels exceeding the
CCME guideline (12 μg/g dw) except for Kelantan, P.
Pauh, and Senawang with P. Klang having the highest As
in soil (57.05 μg/g dw). In C. asiatica, As accumulation
was highest in roots followed by leaves and stems.When
the As level in soils were higher, the uptake of As in
plants would also be increased. After the transplantation
of plants to semi-polluted and polluted sites for 3 weeks,
all concentration factors were greater than 50 % of the
initial As level. The elimination factor was around 39 %
when the plants were transplanted back to the clean sites
for 3 weeks. The findings of the present study indicated
that the leaves, stems and roots of C. asiatica are ideal
biomonitors of As contamination. The present data
results the most comprehensive data obtained on As
levels in Malaysia.

Full text

1 23
Environmental Monitoring and
Assessment
An International Journal Devoted to
Progress in the Use of Monitoring Data
in Assessing Environmental Risks to
Man and the Environment
ISSN 0167-6369
Environ Monit Assess
DOI 10.1007/s10661-012-2787-6
An investigation of arsenic contamination
in Peninsular Malaysia based on Centella
asiatica and soil samples
G.H.Ong, C.K.Yap, M.Maziah,
H.Suhaimi & S.G.Tan

1 23
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An investigation of arsenic contamination in Peninsular
Malaysia based on Centella asiatica and soil samples
G. H. Ong &C. K. Yap &M. Maziah &H. Suhaimi &
S. G. Tan
Received: 17 March 2012 /Accepted: 5 July 2012
#Springer Science+Business Media B.V. 2012
Abstract The first objective of this study was to provide
data of arsenic (As) levels in Peninsular Malaysia based
on soil samples and accumulation of As in Centella
asiatica collected from 12 sampling sites in Peninsular
Malaysia. The second objective was to assess the accu-
mulation of As in transplanted C. asiatica between con-
trol and semi-polluted or polluted sites. Four sites were
selected which were UPM (clean site), Balakong (semi-
polluted site), Seri Kembangan (semi-polluted site) and
Juru (polluted site). The As concentrations of plant and
soil samples were determined by Instrumental Neutron
Activation Analysis. The As levels ranged from 9.38 to
57.05 μg/g dw in soils, 0.21 to 4.33 μg/g dw in leaves,
0.18 to 1.83 μg/gdwinstemsand1.32–20.76 μg/g dw in
roots. All sampling sites had As levels exceeding the
CCME guideline (12 μg/g dw) except for Kelantan, P.
Pauh, and Senawang with P. Klang having the highest As
in soil (57.05 μg/g dw). In C. asiatica, As accumulation
was highest in roots followed by leaves and stems. When
the As level in soils were higher, the uptake of As in
plants would also be increased. After the transplantation
of plants to semi-polluted and polluted sites for 3 weeks,
all concentration factors were greater than 50 % of the
initial As level. The elimination factor was around 39 %
when the plants were transplanted back to the clean sites
for 3 weeks. The findings of the present study indicated
that the leaves, stems and roots of C. asiatica are ideal
biomonitors of As contamination. The present data
results the most comprehensive data obtained on As
levels in Malaysia.
Keywords Arsenic .Centella asiatica .Peninsular
Malaysia .Neutron activation analysis
Introduction
Arsenic (As) occurs naturally in the environment as a
result of the weathering of parent rocks even though
rarely in its elemental form (O’Neil 1995; CCME
2001). Historically, As compounds (calcium arsenate,
Environ Monit Assess
DOI 10.1007/s10661-012-2787-6
G. H. Ong :C. K. Yap (*)
Department of Biology, Faculty of Science,
Universiti Putra Malaysia UPM,
43400 Serdang, Selangor, Malaysia
e-mail: yapckong@hotmail.com
G. H. Ong
e-mail: mao_ong@hotmail.com
M. Maziah
Department of Biochemistry, Faculty of Biotechnology and
Biomolecular Sciences, Universiti Putra Malaysia UPM,
43400 Serdang, Selangor, Malaysia
H. Suhaimi
Pusat Nuklear Negara,
Bangi,
4300 Kajang, Selangor, Malaysia
S. G. Tan
Department of Cell and Molecular Biology,
Faculty of Biotechnology and Biomolecular Sciences,
Universiti Putra Malaysia UPM,
43400 Serdang, Selangor, Malaysia
Author's personal copy

lead arsenate, and sodium arsenite) have been used as
pesticides and fertilizers (ATSDR 2007). As has
also been used as a decolorizer in the manufacture
of glass, in various metallurgical processes such as
the production of alloys, veterinary and human
medicines, and lead-acid batteries (CCME 2001;
IPCS 2001;ATSDR2007; Kabata-Pendias and
Mukherjee 2007). Hence, a more efficient and prac-
tical approach for assessing As pollution is needed.
Inorganic compounds of As are extremely toxic and
may cause gastrointestinal symptoms, cardiovascular,
and nervous system function disturbances and eventually
death (IPCS 2001).
In this study, we used Instrumental Neutron Activa-
tion Analysis because it is accepted as an important
technique for the analysis of different elements in the
local environment. In fact, the application of this tech-
nique was initiated by national needs (Hassan 2008).
NAA is a well-known reference method being widely
used for the determination of the concentrations of many
trace elements in environmental materials (Parry 1991).
Besides, this method can be used to detect total element
content because a neutron has no charge and can pass
through most materials without difficulty. NAA is free
from laboratory and reagent contamination and it is non-
destructive, thus the samples will not be permanently
damaged and can be reanalyzed at any time (IAEA-
TECDOC-1215 2001). This will reduce human error
since no digestion is needed. Hence, high accuracy
and precision data can be obtained through NAA.
Centella asiatica (family: Umbelliferae) is the only
plant extract from this genus to be found in commer-
cial drugs today (Zainol et al. 2003). Currently, the
World Health Organization (WHO) has acknowledged
C. asiatica as one of the most important medicinal
plant species to be conserved. The major route for
entering of toxic elements into living organisms is
via the food chain which is also considered very
serious for the biology and health of man and animals
(Kassem et al. 2004). According to Lee et al. (1991),
none of the local vegetable samples showed levels
greater than 2.00 μg/g dw of As in Malaysia. The As
contamination in Malaysia did not reach the level of
concern to the public at that time. However, the con-
centration levels of As of 19 % of well water samples
from Sabah in 2010 showed levels exceeding those in
the WHO health-based guidelines (Kato et al. 2010).
This indicates that the As level in Malaysia had in-
creased throughout the years due to human activities.
Therefore, more attention should be placed on the
levels of As in Malaysian plants.
In Malaysia, currently, no comprehensive soil ref-
erence values are available to establish levels of po-
tentially toxic As for different land uses such as
agricultural, residential, industrial, and recreational
land (Yap and Pang 2011). Therefore, this study can
help in the better assessment of the As contamination
of natural soil resources which has emerged as an
important issue due to the extension of urbanization
and industrialization in Peninsular Malaysia. So far, in
the literature review, there is no reported As contam-
ination in C. asiatica in Malaysia. The aim of this
study was to assess the degree of anthropogenic influ-
ence in soils and in the accumulation of As in C.
asiatica. The second objective was to assess the accu-
mulation of As by transplanted C. asiatica between
control and semi-polluted or polluted sites.
Methodology
Sampling
Plant and soil samples were collected from 12
different locations in Peninsular Malaysia (Fig. 1)
in 2011. Whole plants (2–4 months maturity) were
collected from the sampling sites and put into
plastic bags. The plants were separated by hand
with clean gloves into three different parts namely
leaves, stems and roots. At the same time, surface soil
(top 3–5 cm) were also collected by using a plastic
scoop after the litter had been removed. The soils
were stored in clean plastic bags for transport to the
laboratory.
Transplantation study
In the transplantation experiment, the C. asiatica was
obtained from Taman Pertanian Universiti (TPU),
Universiti Putra Malaysia and planted for 2 months
to achieve maturity stage. The plants were acclima-
tized for 1 week before being transferred to the study
sites. Four sites were selected, namely UPM’s TPU
(clean and control site), Balakong (semi-polluted site),
Seri Kembangan (SK) (semi-polluted site), and Juru
(polluted site) for experimental study.
TPU is selected as the control site because it is an
agricultural area whereas Balakong, SK, and Juru
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were known as industrial area. Prior to transplantation,
soils were collected from UPM, SK, Balakong, and
Juru and the soils were determined for As levels. The
results showed As in soils were 68.23 μg/g dw for
Juru, 53.89 μg/g dw for SK, 48.48 μg/g dw for Bala-
kong and 28.54 μg/g dw for UPM at week 0. Based on
the As levels, UPM soil was categorized as clean, SK,
and Balakong as semi-polluted sites and Juru as a
polluted site. The transplantation studies were carried
out under both laboratory and field conditions.
For the experimental field condition, the plants were
transferred from UPM (control) to semi-polluted sites
No Sampling sites Site Description GPS
.aeragnisuohraeNnatnaleK.1 4° 57' 14.9" N, 101° 50' 15.9" E
.aeraerutlucirgaraeNsilreP,uarA.2 6° 28' 24.9" N, 100° 15' 0.8" E
3. Universiti Putra Malaysia (UPM),
Selangor
Near agriculture area. 3° 0' 25.5" N, 101° 43' 22.6" E
4. Butterworth, Penang Near an industrial area
and highway.
5° 25' 41.8" N, 100° 23' 13.2" E
5. Karangan, Kedah Near an oil palm
plantation.
5° 30' 15.8" N, 100° 37' 45.7" E
6. Permatang Pauh (P. Pauh), Penang Near a housing area
and highway.
5° 24' 18.0" N, 100° 24' 50.8" E
7. Pontian, Johore Near a plant agriculture
area.
1° 29' 12.5" N, 103° 23' 55.8" E
8. Kempas, Johore Near housing area. 1° 32' 41.3" N, 103° 41' 41.9" E
9. Kepala Batas (K. Batas), Penang Near housing and
agriculture area.
5° 31' 15.6" N, 100° 26' 12.5" E
10 Seremban, Sembilan Near shop lots and road
sides.
2° 43' 26.3" N, 101° 56' 51.5" E
11 Senawang, Sembilan Near an industrial area. 2° 42' 55.6" N, 102° 0' 4.7" E
12 Port Klang, Selangor Near port and industrial
area.
3° 0' 15.0" N, 101° 24' 48.1" E
Fig. 1 Map showing the
sampling sites in Peninsular
Malaysia
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(Balakong, SK) and polluted site (Juru) from week 0 to
week 3. For the control, soil was obtained from the top
soil in TPU. Afterwards, the plants were back-
transplanted from the semi-polluted and the polluted
sitestothecontrolsiteatweek3andexposedfor
another 3 weeks (until week 6).
For the experimental laboratory conditions, soils
from UPM, Balakong, SK, and Juru were collected
and placed onto trays. At week 0 to week 3, plants
from the control trays were transferred to trays con-
taining soils collected from the semi-polluted sites
namely Balakong, SK, and polluted site namely Juru.
From week 3 to week 6, the plants from the semi-
polluted and the polluted trays were back-transplanted
to the control trays.
Three replicates were done for each site (three traps
of 75×75 cm for field study and three trays of 60 ×
35×10 cm for laboratory study). The plants were
transplanted every 3 weeks because transplantation
work normally can have an obvious effect after
2 weeks (U.S.EPA 1996). The plants were harvested
at every 3 weeks. Soils samples were also collected at
week 0 and week 6.
Neutron Activation Analysis (NAA) (U.S.EPA, 2001;
IAEA-TECDOC-1360 2003)
The plant and soil samples were dried in an oven at
65 °C for around 5 days until constant dry weights.
The dried samples were ground by using an electronic
agate homogenizer to obtain homogenous powder of
about 2-mm mesh size to ensure the elements within
each sample were uniformly distributed. Then, the
samples were stored in polyethylene bottles for future
analysis. For all samples, the homogenous powder
samples were shaken manually and had a weight rang-
ing 0.15–0.20 g transferred into a polyethylene vial
and heat-sealed. Certified reference material (CRM)
IAEA-SOIL-7 was prepared under identical condi-
tions and used as quality control for each batch. The
recovery of As based on CRM was 89.25 % and the
relative (%) standard deviation was 18 % (CRM cer-
tified value, 13.40± 0.67 μ/g dw; measured value,
11.96± 2.16 μ/g dw). The limit of detection of As by
NAA was 0.001 mg/g. Therefore, it was highly sensi-
tive, precise, and accurate.
The irradiations were performed in the TRIGA MARK
II reactor at the Agensi Nuklear Malaysia (NUKLEAR
MALAYSIA), Bangi, Selangor (Malaysia). As is a long-
lived radioisotope which has 26.40 h half life.
Hence, long irradiation with neutron flux of 4–5×
10
12
n/cm
2
was used for long-lived isotopes such as
As.Afterirradiationbythermalneutronfluxinthe
TRIGA MARK II research reactor, the radioactivity
measurements of the samples were carried out after
a proper cooling time by using various close-end
coaxial high purity germanium detectors (Model
GC3018 CANBERRA Inc and Model GMX
20180, EG4G ORTEC Nuclear Instrument) and
their associated electronics. The cooling time for
the counting varied between 3–6 days. The live
time for the counting of As was 3,600 s.
Geochemical index
Enrichment factor (EF) was utilized to differentiate
between metals originating from human activities
and those from natural sources. In addition it can also
assess the degree of anthropogenic influence. The
value of the EF was calculated by a modified formula
suggested by Buat-Menard and Chesselet (1979):
EF ¼CnsampleðÞCref sampleðÞ
=
BnbaselineðÞBref baselineðÞ
=

C
n
(sample) was the con-
centration of the examined metal, C
ref
(sample) was the
concentration of the reference metal, B
n
(baseline) was
the content of the examined metal, B
ref
(baseline) was
the content of the reference metal.
Titanium (Ti), aluminum (Al), and iron (Fe) were
selected for normalizing As concentrations in the sam-
ples due to it being a conservative element which is
known to be derived mainly from crustal weathering
(Schütz and Rahn 1982). The baseline values were
selected from the element’s concentrations in the con-
tinental crust (As—1.7 ppm, Al—79,600 ppm, Ti—
4010 ppm and Fe—43,200 ppm by Wedepohl 1995)
(As—1.8 ppm, Al—83,200 ppm, Ti—3800 ppm and
Fe—83,200 ppm by Taylor 1964; Matini et al. 2001)
since Malaysia does not have these baseline values
and the reference values are based on the global aver-
age values. The level EF was categorized in Table 3
according to Han et al. 2006.
According to Nael et al. (2009), the lithogenic
element concentration of a given soil location was
estimated from the Ti concentration (in micro-
grams per gram) of soils for particular location
and the C
n
(sample)/Ti
ref
(baseline) ratio of the
baseline as
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Cn lithogenic ¼Ti Cn
Tiref baselineðÞ

The difference between the measured concentration
and the estimated lithogenic concentration of C
n
(sample)
was used to estimate depletion in the soil of interest, i.e.
CnsampleðÞ
measured <CnsampleðÞ
lithogenic lithogenicðÞ
CnsampleðÞ
measured <CnsampleðÞ
lithogenic enrichmentðÞ
The geoaccumulation index (Igeo) can be calculated
by the following equation (Yap and Pang 2011):
Igeo ¼Log2 Cn
1:5Bn

C
n
was the concentration of the examined metal, B
n
was
the content of the reference metal. Factor 1.5 is the
background matrix correction factor due to lithogenic
effects. Because we did not have the background values
of the metals of interest, just as we did in the EF calcu-
lation, we adopt the earth crust values (Wedepohl 1995;
Tay lor 1964; Matini et al. 2001) in the Igeo calculation.
The concentration factor can be used to determine
the uptake of As by plants for transplantation studies.
It was calculated according to Yap et al. (2003).
Concentration factor ¼Asend of metal accumulation
Asinitial
The rate of As accumulation was calculated accord-
ing to a formula (Yap et al. 2003) as follows
Rate of As accumulation ¼Asexposed Asinitial
DayðsÞof As exposure
Note: weeks 0–3 was accumulation
The elimination factor used to determine the elim-
ination of As by plants for the transplantation studies
was calculated according to Yap et al. (2003).
Elimination factor ¼Asend of metal elimination
Asinitial
The rate of As elimination was calculated according
to the following formula (Yap et al. 2003):
Rate of As elimination ¼Asexposed Asinitial
DayðsÞof As elimination
Note: weeks 3–6 was elimination
Results
Based on the levels of As in soils from the 12 sam-
pling sites, the range of As concentration in Peninsular
Malaysia was from 9.38 to 57.05 μg/g dw. The As
level in soils from P. Klang was significantly (P<0.05)
highest (57.05 μg/g dw) (Fig. 2) compared to the other
sampling sites. According to the data presented in
Table 1, all the EF values were greater than 1 with
EF from P. Klang being highest and the least was from
Kelantan. In Fig. 2, all the sampling sites showed
enrichment since all the measured levels of As were
higher than the calculated levels. For all the sampling
sites, the roots showed the highest As accumulation
followed by leaves and stems (Fig. 3). Based on
Fig. 3, P. Klang, K. Batas, and Kelantan showed the
highest As accumulations in stems and roots. In leaves,
K. Batas, Kelantan, Arau, and P. Klang were highest in
As levels.
In Fig. 4, the accumulation of As increased for all
parts when transplanted from control to semi-
polluted and polluted sites under field condition
(week0toweek3).Inroots,theincreaseswere
highest for Juru followed by SK and Balakong.
For leaves and stems, the increase of As accumu-
lations showed the same trend as in roots. How-
ever, the accumulation decreased (weeks 3 to 6)
after transplantation from the semi-polluted and
polluted sites back to the control sites. The accu-
mulation was still highest in Juru followed by SK
and Balakong. For the transplantation study under
0 102030405060
P.Klang
Senawang
Seremban
K.Batas
Kempas
Pontian
P.Pauh
Kalangan
Butterworth
UPM
Arau
Kelantan
Meas u red
Calculated
Fig. 2 Measured total and calculated enrichment concentrations
(mean ± SD, in micrograms per gram dry weight) of As in soils
collected from 12 sampling sites from Peninsular Malaysia
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laboratory conditions, the trend was exactly similar
to the transplantation study under field conditions
but with lower concentrations of As accumulated
(Fig. 4). In Table 2, the overall values for the con-
centration factor and the rate of accumulation were
highest for Juru under field and laboratory condi-
tions. The elimination factor was highest for Bala-
kong and the rate of elimination was fastest for Juru
(Table 2).
Discussion
As in soil samples
Based on Fig. 2, As contamination in all sampling sites
ranged from 9.38 to 57.05 μg/g dw in soils. The soils
from all sites contained less than 40 μg/g dw of As
except for P. Klang (57.05 μg/g dw). Typical As con-
centrations reported in uncontaminated soils ranged
from 1 to 40 μg/g (ATSDR 2007). Therefore, all sam-
pling sites were considered below the threshold soil
guideline values (micrograms per gram dry weight) for
As for residential (32), allotment (43), and commercial
(640) land use (Environment Agency 2009). The levels
of As in Seremban, K. Batas and UPM were within the
range for residential guideline while P. Klang was within
the range for allotment (allocated for certain uses). The
other sampling sites were below the residential values.
However, all samplings from Peninsular Malaysia were
below the commercial guideline. According to CCME
(2001), the guideline for As is 12 μg/g dw. All sampling
sites exceed the guideline values except for Kelantan, P.
Pauh, and Senawang. This indicated that As levels in
Peninsular Malaysia were enriched with As. Therefore,
more concern about As contamination should be shown
by the public in Malaysia especially for agricultural
purpose.
Around 39.8 μg/gdwofAsinurbansoilswas
reported at XuZhou, China (Xue et al. 2005). In Pen-
insular Malaysia, an average of 24.96 μg/g dw of As
in soils was found indicating that As contamination in
Peninsular Malaysia could still be considered low on
the average. Chen et al. (1999) reported that As con-
centrations in soils ranged from 0.01 to 50.6 μg/g dw
in Florida surface soils. The range of As in soils was
Table 1 Levels of enrichment factor of U from12 sampling sites in Peninsular Malaysia
Sites EF
a
EF
b
EF
c
EF
d
EF
e
EF
f
Igeo
g
Igeo
h
1. P. Klang 36.58 32.74 32.64 40.17 31.56 31.16 2.76 3.43
2. Senawang 6.71 6.00 10.88 13.39 7.79 7.69 3.00 3.67
3. Seremban 21.92 19.62 32.64 40.18 18.46 18.23 3.60 4.27
4. K. Batas 25.34 22.68 28.48 35.06 15.08 14.88 3.08 3.75
5. Kempas 14.06 12.58 17.87 21.99 12.02 11.86 2.89 3.55
6. Pontian 10.55 9.45 23.20 28.56 10.90 10.76 3.35 4.02
7. P. Pauh 12.88 11.53 16.44 20.23 7.37 7.28 1.16 1.83
8. Kalangan 14.95 13.38 25.09 30.89 36.85 36.37 3.31 3.98
9. Butterworth 18.11 16.21 15.69 19.31 11.57 11.43 3.16 3.83
10. UPM 18.73 16.76 14.34 17.65 17.73 17.50 1.69 2.36
11. Arau 9.72 8.70 27.27 33.57 7.00 6.91 2.96 3.62
12. Kelantan 4.48 4.01 7.67 9.44 5.04 4.98 1.73 2.39
a
(with Ti) Wedepohl (1995)
b
(with Ti) Taylor (1964) and (Matini et al. 2001)
c
(with Fe) Wedepohl (1995)
d
(with Fe) Taylor (1964) and (Matini et al. 2001)
e
(with Al) Wedepohl (1995)
f
(with Al) Taylor (1964) and (Matini et al. 2001)
g
Wedepohl (1995)
h
Taylor (1964)
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wide and this could be due to anthropogenic activities
causing high As contamination on certain sites. How-
ever, 8.7 μg/g dw of As in soils worldwide (guideline
values) was reported by Pendias and Pendias (1985).
This shows that the As level worldwide has increased
day by day due to human activities. Therefore, more
attention is required to control the amount of As being
released into the environment.
The EF values of soils for all sampling sites were
greater than 1 based on both references (Table 1)
which indicated that As contamination originated from
human activities (Nael et al. 2009). Based on Table 3,
all the soil samples showed either significant enrich-
ment or very high enrichment. According to Table 4,
three sites showed Igeo class 4 (strongly polluted),
four sites showed Igeo class 5 (strongly to very strongly
polluted) and five sites showed Igeo class 6 (very
strongly polluted). Most natural soils contain low levels
of As, but industrial wastes and pesticide applications
may increase the concentrations (IPCS 2001). P. Klang
was highest in enrichment due to its location as one of
the largest and busiest ports in the country and nearby
industrial activities. In Fig. 2, the measured concentrations
of As were higher than the calculated levels indicating that
the concentrations of As in Peninsular Malaysia were
enriched with As. EF of soils ranging from 0.6 to 31.2
had been reported in the Orontes River basin of Syria
(Kassem et al. 2004). The trend was similar with Penin-
sular Malaysia in that different nearby activities affected
the level of enrichment.
As in plant samples
Based on Fig. 3, As accumulation was highest in roots
followed by leaves and stems because plants developed
certain mechanisms that could immobilize certain met-
als when they were bound to their cell walls. Therefore,
the metal uptake by roots was reduced and metal trans-
location to the shoot could be inhibited. Our results were
supported by those of Soares et al. (2001); Singh and
Sinha (2005) and Tang et al. (2009). The general toler-
ance level of As is considered to be around 2 mg/kg in
plant tissues. Excessive uptake of As will disrupt en-
zyme function and impair phosphate flow in the plant
system (Kabata-Pendias and Mukherjee 2007). Hence,
As might be accumulated in the roots and be unable to
012345
P.Klang
Senawang
Seremban
K.Batas
Kempas
Pontian
P.Pauh
Kalangan
Butterworth
UPM
Arau
Kelantan
Leav es
00.511.52
P.Klang
Senawang
Seremban
K.Batas
Kempas
Pontian
P.Pauh
Kalangan
Butterworth
UPM
Arau
Kelantan
Stems
0 5 10 15 20 25
P.Klang
Senawang
Seremban
K.Batas
Kempas
Pontian
P.Pauh
Kalangan
Butterworth
UPM
Arau
Kelantan
Roots
Fig. 3 As concentrations (mean ± SD, in micrograms per gram dry weight) in leaves, stems and roots of Centella asiatica collected
from 12 sampling sites in Peninsular Malaysia
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yrotarobaL ydutS dleiF
0
2
4
6
8
10
12
14
16
-1012 34567
Juru
leav es
stems
roots
week
1
2
3
4
5
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Fig. 4 Concentrations (mean
± SD, in micrograms per gram
dry weight) of As in leaves,
stems and roots of Centella
asiatica from transplantation
studies under field and
laboratory conditions
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enter the plant by being kept in the root cells where they
would be detoxified by forming complexes or seques-
tered into vacuoles (Hall 2002). This action greatly
restricted the translocation of metals to the above-
ground organs. Moreover, it could protect the leaf tis-
sues and the metabolically active photosynthetic cells
from heavy metal damage (Navari-Izzo et al. 2003;
Sgherri et al. 2003).
As expected, As concentrations were highest in
C. asiatica from P. Klang for leaves, stems and roots.
Burning of coal and the smelting of non-ferrous metals
including copper will release As to the environment
(O’Neil 1995). The plants from K. Batas and Kelantan
also showed high As in all parts due to their being
located nearby agricultural sites. Soil on agricultural
land treated with arsenical pesticides may retain
substantial amounts of As (Kabata-Pendias and
Mukherjee 2007). Mean total As concentrations of 50–
60 μg/g dw had been recorded for agricultural soils
treated with arsenical pesticides (Sanok et al. 1995).
Hence, higher level of As can be taken up by plants.
TheAslevelsinArauwerehigherinleavesmostly
due to the attachment of dust or fly ash on the leaves
since the soil content of As was not significantly (P<
0.05) high. As is volatile and can be generated in com-
bustion. Fly ash contains environmental toxins in sig-
nificant amounts including As (43.4 μg/g dw) (U.S.EPA
2007). Ingestion of As from soil and dust may not be a
significant source of As intake for adults but it may
be significant for children, particularly in locations
Table 4 Geoaccumulation index (Igeo) in relation to pollution
extent according to Müller (1981)
Igeo values Igeo class Pollution intensity
>5 6 Very strongly polluted
4–5 5 Strongly to very strongly polluted
3–4 4 Strongly polluted
2–3 3 Moderately to strongly polluted
1–2 2 Moderately polluted
0–1 1 Unpolluted to moderately polluted
<0 0 Unpolluted
Table 2 Concentration factor,
rates of accumulation (μg/g per
day), elimination factor, rates of
elimination (μg/g per day) of
As in transplantation study
under field and laboratory
conditions
Sites Field condition Laboratory condition
Leaves Stems Roots Leaves Stems Roots
Concentration factor
Juru 4.69 3.66 2.48 2.98 2.88 1.23
Balakong 1.59 2.64 1.56 1.50 1.98 1.57
SK 2.28 2.97 2.24 2.20 1.80 1.66
Rate of accumulation
Juru 0.35 0.15 0.45 0.19 0.10 0.07
Balakong 0.06 0.09 0.17 0.05 0.05 0.17
SK 0.12 0.11 0.38 0.11 0.04 0.20
Elimination factor
Juru 0.57 0.48 0.54 0.56 0.65 0.57
Balakong 0.55 0.50 0.80 0.92 0.62 0.79
SK 0.44 0.47 0.54 0.39 0.58 0.62
Rate of elimination
Juru 0.19 0.11 0.34 0.12 0.06 0.16
Balakong 0.07 0.07 0.09 0.01 0.04 0.10
SK 0.12 0.09 0.31 0.13 0.04 0.19
Table 3 Contamination categories based on enrichment factor
(EF) (Han et al. 2006)
Enrichment factor (EF) Degree of contaminations
<2 Deficiency to minimal enrichment
2–5 Moderate enrichment
5–20 Significant enrichment
20–40 Very high enrichment
>40 Extremely high enrichment
Environ Monit Assess
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near industrial and hazardous waste sites (IPCS
2001). Several countries currently use a 1 μg/g
limit for As in food and this is cited as the safety
level (Duxbury and Zavala 2005). Therefore, we should
be aware of the As levels in the plants that we eat.
As in transplantation studies
In Fig. 4, all the samples showed a similar trend as for all
the wild samples from the 12 sampling sites (Fig. 3), the
roots had the highest As accumulation followed by
leaves and stems. This is because the roots are the first
organ to be in contact with metals and roots adhere to the
soil all the time. In Fig. 4, the accumulation of As
increased for all parts when transplanted from control
to semi-polluted and polluted sites in field conditions
(weeks 0 to 3). Based on Table 2, the concentration
factor was highest for Juru mostly due to it being
more contaminated with As. The As there originated
from the repair and maintenance operations in the ship-
yard located further up the estuary in Juru (Din and
Jamaliah 1994;Ramachandran1997).
All concentration factors were higher than 1, indi-
cating that the plants were able to uptake high As. In
3 weeks’time, the plants were able to uptake at least
50 % higher than the initial value. The rate of accu-
mulation was high ranging 0.04–0.45 μg/g dw per
day. Therefore, the plants can reflect the As contami-
nation by their accumulation levels. C. asiatica can be
chosen as an ideal biomonitor due to its tolerance to
exposure to environmental variations in physico-
chemical parameters. The most important of all is its
capability as net accumulators of the metal with a
simple correlation between metal concentrations in
tissues and average ambient bioavailable metal con-
centrations over a short time period (Rainbow and
Phillips 1993; Wittig 1993).
However, the accumulation decreased (weeks 3 to 6)
after transplantation back to the control site even though
the accumulation was higher than at the control site. For
the transplantation under laboratory conditions, the
trend was exactly the same as the transplantation under
field conditions with lower concentration of As accu-
mulated (Fig. 4). As was found in most plants, its
biochemical role is unclear (Farago et al. 2003;
Kabata-Pendias and Mukherjee 2007).
Based on Table 2, the elimination factor for field
and laboratory conditions were at least 39 % for all
parts. This indicated that As could be eliminated from
plants when transplanted to sites less contaminated by
As. As does not play an important role in normal
metabolic activities. Hence, the plant will try to
eliminate excess As from it to prevent phytotoxicity
caused by high As levels. Studies on As toxicity have
shown that plants will suffer considerable stress upon
exposure, with symptoms ranging from inhibition of
root growth through to death (Macnair and Cumbes
1987; Meharg and Macnair 1991; Paliouris and
Hutchinson 1991;Barrachinaetal.1995). Besides,
on exposure to As species, reactive oxygen species will
be generated in response to metal stress (Hartley-
Whitaker et al. 2001).
By comparing the accumulation and the depuration
of As as shown in Fig. 4for weeks 0, 3, and 6, the
accumulation in the laboratory was lower than those in
transplanted under field conditions especially for Juru
even though the soils were obtained from the same
sites. This was due to the continuous supply of As
contamination from nearby activities in Juru. There-
fore, the accumulation was higher than under labora-
tory conditions where the As level in the soil
decreased with time during the experiment. However,
the levels of As in plants were not significantly differ-
ent (P<0.05) between the experimental field and lab-
oratory studies for Balakong and SK. This might be
due to As not being significantly added from the
source into soils for Balakong and SK.
When comparing between week 0 and week 6, higher
As was found in the back-transplanted plant in week 6
than in week 0 in that they were far from reaching the
initial As concentration (week 0). This could be
due to the accumulation being dependent on the
transplantation period (Hedouin et al. 2011). This
indicated that the eliminations of As was not com-
plete during the 3 weeks of transplantation for C.
asiatica. The elimination rate was slower com-
pared to the accumulation rate. Therefore, a longer
time is required for the elimination of As in plants.
Conclusion
As levels ranged from 9.38 to 57.05 μg/g dw for soils
from 12 sampling sites in Peninsular Malaysia. All
sites were considered not contaminated except for P.
Klang (57.05 μg/g dw). As accumulation was highest
in roots followed by leaves and stems in C. asiatica.
For the transplantation study, all concentration factors
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were greater than 50 % and the rate of accumulation
ranged from 0.04 to 0.45 μg/g dw per day. The elim-
ination factor was around 39 % and the elimination
rate ranged from 0.01 to 0.34 μg/g dw per day. The
elimination rate was slower when compared to the
accumulation rate. Therefore, a longer time was re-
quired to eliminate As from plants. The findings of
this study indicated that the leaves, stems, and roots of
C. asiatica are potential biomonitors of As concentra-
tions. However, further studies on the genetic structure
on this species are needed in the future in order to
confirm it being an ideal biomonitor.
Acknowledgments The authors wish to acknowledge the
financial support provided through the Research University
Grant Scheme (RUGS) [vote no. 9322400] by Universiti Putra
Malaysia.
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