Assessment of Heavy Metals in Soils and Tuber Crops on Ex-Mining Land of Southern Perak, Malaysia
Large areas of ex-mining lands in Southern Perak, Malaysia, are used for the cultivation of vegetables, fruits and tuber crops due to the shortage of land for agricultural productions. These areas have been cultivated for more than 20 years. Recent studies have reported that ex-mining land used f...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2004
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| Online Access: | http://psasir.upm.edu.my/id/eprint/6142/1/FP_2004_26.pdf |
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| Summary: | Large areas of ex-mining lands in Southern Perak, Malaysia, are used for the
cultivation of vegetables, fruits and tuber crops due to the shortage of land for
agricultural productions. These areas have been cultivated for more than 20
years. Recent studies have reported that ex-mining land used for the cultivation
of tuber crops and some fruits were found to be contaminated by heavy metals.
Heavy metals concentrations may be high due to the use of high amounts of
organic fertilizers (chicken dung) and agrochemicals (fertilizers, pesticides).
There is a growing concern and awareness amongst consumers that long term
addition of fertilizers may accumulate heavy metals in soil and taken up by
tuber crops grown in the ex-mining lands. Heavy metals are known to cause
detrimental health effects to human. Thus, a study concerning heavy metals
contamination on tuber crops cultivated on ex-mining lands had been
conducted.
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Four major cultivation areas were selected for this study namely; Kg. Baharu
Bikam, Tapah Road, Pekan Pasir and Kg. Baru Cold Stream. The farms in
these areas were found to be the largest tuber crops production in southern
Perak. In the cultivated areas, sampling sites were chosen where the tuber crops
were ready for harvest. Each sampling site, 3 soil samples and tuber crops were
sampled. The three soil samples from each point were combined to form a
composite sample. The soils were collected by using a stainless steel auger. An
hundred eighty soil samples were collected from the cultivated soils which is 60
soil samples for each 3 depths (0-20 cm, 20-40 cm and 40-60 cm). While only
60 soil samples were collected on topsoil (0-20 cm) from the uncultivated exmining
lands. The uncultivated soils were collected for the determination of
heavy metals and used as background values (control). An overall total of 240
soil samples were taken from the cultivated and uncultivated soils. The crops
selected were tuber crops such as tapioca, yam bean, sweet potatoes and
Chinese radish. For each sampling site, geographic coordinates were recorded
using global positioning system (GPS). The soils were air-dried, crushed,
sieved to pass 2 mm sieve and analysed for the texture, mineralogy, pH, total
organic carbon (OC), cation exchangeable capacity (CEC), total heavy metals
content (Pb, Ni, Zn, Cd and Cu) and available heavy metals extracted with three
different extractants i.e. 0.1 N HCI, EDTA and DTPA. While heavy metals in
tuber crops were extracted using dry-ashing method. The heavy metals (Pb, Ni,
Zn, Cd and Cu) were determined by Atomic Absorption Spectrophotometer
(AAS).
From this study, it was found that, the uncultivated soils in the study areas can
be categorized according to their texture i.e sand, sandy clay loam and sandy
loam. Sand texture consists of 89.5 to 91.5% sand and very low clay content (7-
10%). Sandy clay loam texture consists of 15.5 to 1 8.4 % sand and very high in
clay content which is 41.8 to 42 %. Sandy loam consists of 12 to 19.5 % clay,
70 to 75.5% of sand and 15.5 to 18 % of silt.
The pH of topsoils in the cultivated ex-mining soils of southern Perak had a
mean value of 6.08. The mean cation exchange capacity of the cultivated exmining
soils was 0.77 cmo1,kg-' soil. The soils have a mean organic carbon
content of 0.66 %. On the other hand, soils in the uncultivated lands have pH,
CEC, OC, with the values of 4.56, 0.35 cmolJcg-' and 0.31 %, respectively.
Generally, there is a significant increase at p5 0.05 of pH, OC and CEC in the
cultivated soils.
Mean concentration of Zn in the cultivated soil was the highest followed by Pb,
Cu, Ni and Cd, with values of 15.84 mgkg-', 10.43 rngkg-', 4.20 mgkg-', 3.07
me', and 0.84 mgkg-', respectively. In the uncultivated soil, a similar trend
in heavy metal concentrations was observed for Zn, Pb, Cu, Ni and Cd with
mean values of 8.09 mgkg-', 5.78 mgkg-', 1 .I9 mgkg-', 1 .OO rngkg-' and
0.69 mgkg-', respectively. T-test analysis showed that metal concentrations in
cultivated soils are significantly higher at p10.05 level than in uncultivated soil
except for Cd. However, both levels are still below the critical heavy metal
concentrations limits in agricultural soils of Peninsular Malaysia and the
concentration ranges (using the 95th percentile), except for Cd.
Total Pb and Cd concentration in soil were significantly positive correlated with
available Pb using 0.1N HCl extractant (r = 0.41*, n= 60) available Cd using
DTPA (r= 0.23*, n=60). On the other hand, total Ni in soil was significantly
negative correlated with available Ni using DTPA (I=-0.38, n=60). Regardless
of the extraction methods used (O.1N HCl, EDTA or DTPA), no significant
correlation was found between total Cu and Zn in soil and available Cu and Zn.
Correlation analysis between heavy metals in tuber crops with available heavy
metals indicates that, there was no relationship between total heavy metals in
the tuber crops and available heavy metals in soil using different extraction
methods except for Zn and Cu, which have a negative correlation using 0.1 N
HCI (r = -0.25*, n= 60) and DTPA (I-=-0.22*, n=60), respectively.
Amongst all of the crops studied, Chinese radish, tapioca and sweet potato
contains the highest concentration of 15.33 mgkg-' Zn, 0.85 mgkg-' Pb and
0.12 mgkg-I Cd, respectively. On the other hand, yam bean showed that the
lowest concentration of Zn, Cd, Cu and Ni with values of 2.41 mgkg-', 0.07
mgkg-', 0.63 mgkg-' and 0.56 mgkg-I, respectively.
Lead is significant higher at pi0.05 in yam bean than in sweet potato and
Chinese radish. There is no significant difference in the concentrations of Cd in
all tuber crops studied. Copper show significant higher in tapioca than in sweet
potato followed by Chinese radish and yam bean. Zinc concentration is
significantly higher in Chinese radish than in tapioca, sweet potato and yam
bean, while Ni is significantly higher in Chinese radish than in yam bean.
Results from this study show an increased concentration of heavy metals in
Chinese radish followed by tapioca, sweet potato and yam bean, but the heavy
metals levels of all the tuber crops studied were still below the Maximum
Permissible Concentration (MPC) as stated in the Malaysia Food Act (1983)
and Food Regulation (1 985).
Spatial distribution map is usefkl to detect the spatial area, which are low,
optimum or high in heavy metal concentration. Tapah Road areas have the
highest concentration of heavy metals in all elements studied with Zn value of
17.41 mgkg-', followed by Pb, Cu, Ni and Cd. On the other hand, Kg. Baharu
Bikam has the lowest concentration for all elements. Statistical analyses
indicate that there is no significant difference at p10.05 of heavy metals content
in soil among those areas.
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