HEAVY METALS IN SOIL AND VEGETABLES AND THEIR EFFECT ON HEALTH Jitender Pal*1, Mukal Bishnoi2, Mandeep Kaur3 *1, 2, 3 Department of Environmental
Science and Engineering,Guru
Jambheshwar, University of Science and Technology,
Hisar (Haryana) 125001, India DOI: https://doi.org/10.29121/IJOEST.v2.i1.2017.03 ABSTRACT The present study was carried out to assess heavy metals Cadmium (Cd), Lead (Pb), copper (Cu), zinc (Zn), Chromium (Cr) and Nickel (Ni) levels in vegetables like Cauliflower (Brassica oleracea var. botrytis), Cabbage (Brassica oleracea), Carrot (Daucus carota), Brinjal (Solanum melongena), Spinach (Spinacia oleracea) and Radish (Raphanus sativus) irrigated with domestic wastewater. The vegetable samples were randomly collected from the farmlands irrigated with domestic wastewater around the Hisar district. Spinach, cabbage, brinjal and carrot accumulated higher Cd (1.30±0.31 mg kg-1), Pb (4.23±0.32 mg kg-1), Cu (1.42±0.25 mg kg-1), Zn (3.4±0.28 mg kg-1), Cr (1.16±0.11 mg kg-1) and Ni (2.45±0.86 mg kg-1) respectively. Transfer Factor (TF) of Cd, Pb, Cu, Zn, Cr and Ni are more in spinach (0.0306), cabbage (0.4448), spinach (0.2642), cauliflower (0.2494), carrot (0.0764) and spinach (0.7469) respectively. The health risk assessment has been calculated followed by Estimated Daily Intake Metal (EDIM) and Estimated Health Risk Index (EHRI). The present study highlights that both adults and children consuming vegetables grown in wastewater irrigated soils accumulate significant amount of these metals. However, the values of these metals were lesser than recommended maximum tolerable levels proposed by the FAO/WHO (1999). Keywords: Daily Intake; Heavy Metals; Plant Uptake; Risk Assessment; Reference Dose; EDIM; EHRI. Cite This Article: Jitender Pal, Mukal Bishnoi, and Mandeep Kaur. (2017). HEAVY METALS IN SOIL AND VEGETABLES AND THEIR EFFECT ON HEALTH. International Journal of Engineering Science Technologies, 2(1), 17-27. doi: 10.29121/IJOEST.v2.i1.2017.03 1. INTRODUCTION Indian economy is based on agriculture and having second largest population in the world. Most of its states are depends on the monsoon. There are two main sources for irrigation. First one is canal and second is ground water but the quality of ground water is so poor for long sustainability of agriculture system. This water is not adequate to fulfill the crop water requirement and needs additional extra water for agricultural purposes. To cater the need of the present demand for irrigation, use of municipal domestic wastewater, is becoming a common practice in urban areas of Haryana, India. This causes serious problems of salinity and ultimately reduction in agriculture production [1]. The large amounts of untreated industrial and domestic wastewater are used for year round irrigation of vegetables. Such waste water usually contains heavy metals which accumulate in the soil. The use of such untreated wastewater has been reported to cause contaminations of the food chain [2-3]. Some trace amount of heavy metals such as Zn and Cu are
essential for the growth of organisms while others such as Cd and Pb are toxic [4-5]. Dietary uptake
pathway could be through crops irrigated with contaminated wastewater and have
been reported to contain large amount of toxic heavy metals which may lead to
health disorders in humans depending on the uptake of these metals into plant
and consumed by animals or humans [6-9]. Consumption of metal contaminated
vegetables may lead to a weakened immune system, intra-uterine growth
retardation, impaired psycho-social behavior, high prevalence of upper
gastrointestinal cancer and other disorders typically associated with
malnutrition [10]. Potential health risk to human being from consumption of
vegetables may be due to heavy metal uptake from contaminated soils via plant
roots as well as direct deposition of contaminants from the atmosphere onto
plant surfaces [11]. A number of previous studies from developing countries
have reported heavy metal contamination in wastewater and wastewater irrigated
soil [5, 12-15]. Dietary intake is the
main route of exposure of heavy metals for most people [16]. The information
about heavy metal concentration in different types of vegetables and their dietary
intake is very important for assessing their risk to human health. Heavy metals
in the nutrient cycle have seriously threatened health and environmental
integrity, therefore, problem of heavy metal contamination in vegetables
requires detailed study so as to develop central strategies. The objective of
present study was bioaccumulation of heavy metals in vegetables irrigated by
domestic wastewater and assessment of health rick due to these heavy metals. 2. MATERIALS AND METHODS 2.1. Study Area and Sampling All the samples of vegetables such as Cauliflower (Brassica oleracea var. botrytis), Cabbage (Brassica oleracea), Carrot (Daucus
carota), Brinjal (Solanum melongena), Spinach (Spinacia oleracea) and Radish (Raphanus sativus); and soils were randomly collected from the farmlands
irrigated with domestic wastewater around the three different locations such as
Rishi Nager (L1), New
Police Line (L2) and Ludass village (L3)
of Hisar district of Haryana, India. Soil
samples were collected at the surface depth of 10 cm using stainless steel
spade sampling tools and plastic buckets to avoid any contamination of samples
with traces of elements from the tools. At each sampling site, scrape away
surface debris and remove a core sample to the appropriate depth. Soil samples
were air dried, ground, passed through a 2 mm sieve and stored in plastic bags
for further analysis. Five ground Water and seven wastewater samples
were also collected from each location. All samples were collected,
stored and kept at 4oC for further analysis in polythene bags/canes
according to their type and brought to the laboratory for metal
quantification. 2.2. Sample Preparation All the collected Vegetables were washed with double
distilled water to remove airborne particles. The edible parts of the samples
were weighed and soil samples were air-dried at room temperature, to reduce
water content. All the samples were then oven-dried in a hot air oven at 70±5 oC for 24 h. Dried samples were powdered using a
pestle and mortar and sieved through muslin cloth. 2.3. Digestion of the Vegetable and Soil Samples For each vegetable, three powdered samples from source
irrigated by domestic wastewater (1.0 g each) were accurately weighed and
placed in crucibles, three replicates for each sample. The soil and vegetable
ash samples were digested with per chloric acid and nitric acid (1:4) solution.
The samples were cooled and contents were filtered through Whattman filter paper
No. 40. Each sample solution was made up to a final volume of 50 ml with
distilled water. Concentration of each heavy metal was analyzed by atomic
absorption spectrophotometer (ASS: model AA6300, Shimadzu). Five samples of each vegetable were assayed and analysed individually in triplicate. Data were
reported as mean ± SD. One way analysis of variance (ANOVA) by Scheffe test was used to determine significant difference
between groups by using SPSS INS Version 16.0 statistical software. 2.4. Risk
Assessment 2.4.1. Transfer
Factor (TF) The transfer factor (TF) of Cadmium (Cd), Lead (Pb), copper
(Cu), zinc (Zn), Chromium (Cr) and Nickel (Ni) from the soil to vegetables was
calculated using equation 1 [17-18]: (1) 2.4.2. Estimated Daily Intake of Metal (EDIM) The Estimated daily oral intake of metals from soil through
vegetables in mg was calculated by equation 2: (2) Where, Cm is heavy metal concentration in
vegetable plants (mg/kg), CF is conversion factor, DI is
daily intake of vegetables (kg/ person/day) and BAw
is average body weight (kg). The conversion factor used to convert fresh
green vegetable weight to dry weight was 0.085 [10]. The average daily
vegetable intake for adults and children were considered to be 0.250 and 0.150
kg/ person/day, respectively, while average body weights were taken as 55 and
25 kg of the age of 35 and 16 years, respectively, for adult and child. 2.4.3. Estimated
Health Risk Index (EHRI) Estimated health risk index (EHRI) is the ratio of estimated daily
intake of metal (EDIM) to the reference dose (RD) is defined as the
maximum tolerable daily intake of a specific metal that does not result in any
harmful health effects. If the value of EHRI is less than one, the exposed
population is said to be safe and if greater than one indicating that there is
a potential risk associated with that metal was calculated by equation 3 [19]: (3) 3. RESULTS AND DISCUSSIONS 3.1. Metal
Concentration Level in Water and Soil The quality of domestic wastewater and ground water (tube
well) was assessed for irrigation with respect to their pH, EC, OC and some of
the heavy metals. The pH of the sewage water in the range of 6.8-7.3 was lower
than the ground water as collected from the nearby area in the range of 7.2–
7.9) while its salt content (EC) was in the range of 175.8-195.3 mS/m
considerably higher than those of ground water (148.9-158.6 mS/m). The
concentration for heavy metal contents in domestic wastewater and in ground water
samples shows that Cd, Pb, Cu, Zn, Cr and Ni are well within the permissible
limit shown in figure 1. In general, concentration of heavy metals were on
higher side in domestic wastewater than in the ground water (tube well) which
could be toxic to some crops and human health. In the studied area, the
concentration of all the heavy metals in water and domestic wastewater were
found to be higher except Zn from the permissible limits of Indian standards
and WHO/FAO [20-22]. The total concentrations of heavy metals (Cd, Pb, Cu, Zn,
Cr and Ni) in soil sampled at three different sites are shown in figure 2. The
average pH at the location-I (7.04±011), location-II (7.02±0.19) and
location-III (7.0±0.03) are almost nearly neutral. The electrical conductivity
(EC) was 190.2-273.6 mS/m for location-I, 202.8-247.2 mS/m for location –II and
170-271.3 mS/m for location-III. The percent organic carbon content in soil was
higher due to constant domestic wastewater irrigation and range from 3.48-5.2%
for location-I, 3.85-5.54% for location-II and 3-69-5.6% for location-III. As
the sub soils were clayey, the organic carbon was found to be in high percent.
Soil organic carbon is the most important indicator of soil quality and in
addition to acting as a store-house of the plant nutrients plays a major role
in nutrient cycling [23]. Figure 1: Heavy metal concentration in water and
wastewater Figure 2: Heavy metal concentrations in soil
at different locations Across the study area, wide ranges of heavy metal concentration
in soil were observed and are shown in figure 3. The observed concentration of heavy metal range between 37.76-73.5 mg kg-1 for Cd, 2.74-22.44 mg kg-1 for Pb,
0.54-24.16 mg kg-1 for
Cu, 0.96-12.44 mg kg-1 for Zn, 3.21-72.85 mg kg-1 for Cr,
1.37-6.47 mg kg-1 for Ni, and 249.3-773.4 mg kg-1 for Fe
for location-I. For location-II, heavy
metals range between 23.7-103.7 mg kg-1 for Cd, 5.67-30.99 mg kg-1
for Pb, 3.04-16.47 mg kg-1 for Cu, 3.16-9.16 mg kg-1 for
Zn, 3.19-41.35 mg kg-1 for Cr and 4.68-13.77 mg kg-1 for
Ni; 6.31-66.61 mg kg-1 for Cd, 3.20-19.60 mg kg-1 for
Pb, 1.35-11.81 mg kg-1 for
Cu, 4.47-15.55 mg kg-1 for Zn, 1.38-3.54-46.64 mg kg-1
for Cr and 1.38-9.99 mg kg-1 for Ni for location-III. The heavy
metal (Cd, Pb, Cu and Cr) concentration was not significantly different in all
the three locations and concentration of Zn in location-I is significantly
different from location-III at (P<0.05)
and location-III is significantly different from location-II at (P<0.05) level. For Ni, the
concentration of Ni in location-I is significantly different from location-II
at (P<0.05) and location-III is is significantly different from location-I at (P<0.05) level. The results clearly
indicate higher concentration of metals in soils which had prolonged irrigation
by sewage wastewater. If the same trend continues the concentration of metals
will accumulate in the soil. Relatively higher amounts of these heavy metal
which attributes to the reduction in soil pH to moderately acidic conditions as
well increase in organic carbon due to the continuous use of sewage effluents.
This may be a cause of prime concern in near future. Long-term application of
domestic wastewater will result in increase in organic carbon and decrease in pH. Figure 3: Concentration of heavy metal in
different vegetables 3.2. Heavy Metal Accumulation in Vegetables The concentration of heavy metals in edible part of
vegetables was investigated in vegetables which are commonly grown. The
bioaccumulation of heavy metals concentration in all the vegetables are
different, so no similar trend have been observed for heavy metal
concentration. The heavy metal bioaccumulation in cauliflower was Zn > Pb
> Cu > Ni > Cd > Cr, for cabbage was Pb > Zn > Cd > Cr
> Cu > Ni, for carrot was Zn > Pb > Ni > Cu > Cr > Cd, for
brinjal Zn > Pb > Cd > Ni > Cr > Cu, for spinach was Zn > Ni
> Pb > Cd > Cu > Cr , a similar trend have also been observed for
radish Zn > Ni > Pb > Cr > Cu > Cd [24]. The concentrations of heavy metals (Cd, Pb, Cu, Zn, Cr and
Ni) in vegetable samples are quite variable and shown in figure 3. The spinach
exhibited higher concentration levels of Cd (1.30 mg kg-1) and Ni
(2.45 mg kg-1) than other vegetables. In contrast, cabbage (4.23 mg
kg-1) contained the highest levels of Pb, while carrot (1.42 mg kg-1)
contained the highest Cu concentration. Furthermore, the concentration of Cr
was higher in radish (1.16 mg kg-1), whereas cauliflower (4.26 mg kg-1)
revealed greater amount of Zn than other vegetables. The concentration of Cd
(1.30 mg kg-1) in spinach is significantly different from the
cauliflower, radish at (p<0.05) and (p<0.001) level,
respectively and for carrot (p<0.05) level. The results of the
present analysis showed that the concentration of Pb (4.23 mg kg-1)
in cabbage is significantly different from cauliflower, brinjal and radish, from the vicinity of three
locations at (p<0.05) and (p<0.001) level. The amounts of
Cu (1.42 mg kg-1) in carrot is significantly different from cabbage
and brinjal at (p<0.05) level. The amount of Zn in all vegetables
i.e., cauliflower, carrot, brinjal,
cabbage, spinach, and radish were found to be not significantly different (p>0.05)
level. Concentration of Cr (1.16 mg kg-1) in carrot is more
significantly different from the cauliflower at (p<0.05) and (p<0.001)
level and concentration of Cr in
radish is significantly different from cauliflower at (p<0.05)
level. Concentration of Ni (1.42 mg kg-1)
in spinach is significantly different from the cauliflower and cabbage at (p<0.05)
level. The range of Cd concentration in brinjal (0.50-1.10 mg kg-1)
recorded in this study was lower than the range (1.10-9.20 mg kg-1)
[25]. Vegetables (spinach and cabbage), range of Ni concentration was highest
in spinach (0.01-3.80 mg kg-1). These values were lower than the
range (5.55 - 15.00 mg kg-1) in spinach from Dinapur
area as well as the range (0.2 - 3.0 mg kg-1) in spinach from waste
water irrigated areas of Hyderabad [25-26]. In cabbage concentration of Pb, Cu,
Zn, Cr, Ni were lower during the present study. The present concentration (mg
kg-1) of 0.30±0.03 for Cd, 0.94±0.10 for Pb, 0.83±0.18 for Cu and
0.94±0.09 for Cr in radish were lower than the values obtained for radish [27].
The higher concentration of Cd, Pb, Cu, Cr and Ni and in radish plants grown at
waste water irrigated areas than the clean water irrigated ones [28]. Among all
the heavy metals, Zn concentration (4.26±0.06) was higher and Cr (0.09±0.07)
was lower in cauliflower. Radwan and Salama have also found highest
concentration of Zn in vegetables collected from Egyptian markets [29]. The
bioaccumulation of Cd in spinach is higher than all the tested vegetable
samples and similar result have also observed by Zhuang and his coworker [30].
The bioaccumulation of Pb, Cu, Zn, Cr and Ni were found higher in cabbage,
carrot, cauliflower, carrot and radish respectively. 3.3. Heavy Metal Transfer Factor Due to industrialization and urbanization, the heavy metal
concentration of soil has increased worldwide. Soil-to- plant transfer of heavy
metal is major pathway of human exposure to soil contamination [17]. The high transfer factor from soil to
plants indicates a strong accumulation of the particular metal by vegetable
crops [28]. The results
indicated that TF values were lower for Cd, Pb, Cu and Cr, and higher TF for Zn
and Ni at all locations. The transfer factor values in soil to plant of
studied metals such as Cd, Pb, Cu, Zn, Cr and Ni for various vegetables varied
between vegetable plants and locations and are shown in table 2. The results
revealed that there is a large variation in transfer factor of Cd, than other
metals in all three locations. The spinach (0.0306) had very high transfer
factor for Cd and followed by brinjal (0.0207), cabbage (0.0165), carrot
(0.0108), radish (0.0071) and cauliflower (0.0049). Similarly, The cabbage
(0.4448), had very high transfer factor for Pb and followed by carrot (0.2376),
spinach (0.2187), brinjal (0.0207), cauliflower (0.1672) and radish (0.0988);
The carrot (0.2977), had very high transfer factor for Cu and followed by
spinach (0.2642), cauliflower (0.2537), radish (0.1740), cabbage (0.0881) and
brinjal (0.0818); The carrot (0.0764) had very high transfer factor for Cr and
followed by radish (0.0619), spinach (0.0527), cabbage (0.0454), brinjal
(0.0408) and cauliflower (0.0054) for
location-III; The cauliflower (0.2494) had very high transfer factor for Zn and
followed by carrot (0.1991), brinjal (0.1909), cabbage (0.1862), spinach
(0.1739) and radish (0.0984) for location-II; The spinach (0.7469) had very
high transfer factor for Ni and followed by carrot (0.4451), radish (0.4542),
brinjal (0.2348), cauliflower (0.0732) and cabbage (0.0335) for location-I. The transfer factor of Cd,
Pb, Cu and Cr is more in Location III, similarly, Zn in location II and Ni in location-I. Therefore, vegetable
crops growing on polluted site can accumulate high concentration of trace
elements to cause serious health risk to consumers. 3.4. Risk Assessment In order to check the health risk of any toxicity from
wastewater, it is necessary to estimate the level of exposure of heavy metals
through food chain. In this study, six vegetables were selected and calculate
the health risk assessment in terms of estimated daily intake of metal (EDIM)
and estimated health risk index (EHRI) by
considering the intake of metal through vegetables by the human being. 3.4.1. Estimated
Daily Intake of Metal (EDIM) The daily intake of heavy metals was estimated on basis of
the average consumption and concentration of metal in particular vegetable
spices. The average concentration of Cd, Pb, Cu, Zn, Cr, Ni and Fe are shown in
figure 3. Based on the above, the estimated daily intake of metal (EDIM) for
adults and children through food chain were calculated and is shown in Table 1.
The highest daily intake of metal such as Pb, Zn, Ni, Cu, Cd and Cr were from
spinach, cabbage, cauliflower, spinach, carrot, spinach and Carrot respectively
grown in domestic wastewater for both adults and children. The results of the
study revealed that EDIM suggest that the consumption of vegetables grown in
domestic wastewater polluted location is high but is free from any risk as the dietary intake of Cd,
Pb, Cu, Zn, Cr and Ni in adults is below
than the permissible limits [31]. 3.4.2. Estimated Health Risk Index (EHRI) In order to investigate the
estimated health risk index (EHRI) associated with domestic wastewater
irrigated soil, it is essential to estimate the level of exposure by
quantifying the route of exposure of a heavy metal to the target person. The
results indicate that the EHRI (table 2) values were less than one for Cd,
Pb, Cu, Zn, Cr and Ni in all tested vegetables consumption. Therefore, the health risk of heavy metals
such Cd, Pb, Cu, Zn, Cr and Ni exposure
through vegetables was of no consequence and generally assumed to be safe. All
the estimated dietary intake of Cd, Pb, Cu, Zn, Cr and Ni were far below
the tolerable limits. The oral reference dose (RD) for Cd, Pb, Cu,
Zn, Cr and Ni are 1.0E-03, 3.5E-03, 4.0E-02, 3.0E-01, 1.5E-00 and 2.0E-02 mg kg
-1 day -1, respectively given by US-EPA [32]. The results
of the study showed that EDIM and EHRI suggest that consumption of vegetables
grown in polluted soil irrigated with domestic wastewater is nearly free of
risk. But there are other sources of metal exposure such as dust inhalation,
vehicular exhaust which were not included in this study. Table 1: Transfer factor (TF) of heavy metals
from contaminated soil to vegetable plant
Table 2: Estimated Daily Intake (EDIM) and Estimated Health Risk Index (EHRI) of
heavy metals in vegetables
4.
CONCLUSIONS &
RECOMMENDATIONS The prolonged
irrigation by domestic wastewater increases heavy metal accumulation in the
soil which leads to contamination of food crops. This study reveals that edible
vegetables shows significant bioaccumulation of heavy metals in vegetables
grown by sewage wastewater irrigation. These vegetables are supplied to local
markets and there is possibility of associated health hazard with consumption
of these contaminated vegetables over a long period of time. The concentration of all heavy metals in
domestic wastewater was found to be higher except Zn from the permissible
limits of national and international standards. The results indicated higher
concentration of metals in soils contributed by prolonged irrigation with
sewage wastewater. If it is continued, the concentration of metals will
accumulate in the soil. The higher amount of these heavy metals which
attributes to reduction in soil pH to moderately acidic conditions and as well
as increase in organic carbon due to the continuous use of domestic wastewater.
The transfer factor of Cd, Pb, Cu and Cr is more in Location III, of Zn in
location II and Ni in location-I. Therefore, vegetable crops growing on
polluted site can bio-accumulate high concentration of trace elements to cause
serious health risk to consumers. The highest daily intake of metal such as Pb,
Zn, Ni, Cu, Cd and Cr were from consumption of the spinach, cabbage,
cauliflower, spinach, carrot, spinach and Carrot, respectively, grown in
domestic wastewater for both adults and children. The results of study also
revealed that EDIM and EHRI
suggest that the consumption of vegetables grown with domestic wastewater in
polluted location is high but is free from any risk. Therefore, the health risks from the heavy metals such Cd, Pb, Cu,
Zn, Cr and Ni exposure through
vegetables was of no consequence and it is generally assumed to be safe.
Therefore, in order to reduce risk, plants with lower accumulative nature
should be grown. In this scenario, the present study indicates that there is
need of proper treatment and disposal of domestic wastewater with less cost and
worldwide acceptable technology. ACKNOWLEDGEMENTS The author would like to thank the department of
Environmental Science & Engineering, GJUS&T, Hisar and Technical
Education Quality Improvement Programme (TEQIP-II) World Bank Project for
providing me the necessary laboratory facilities and financial support. REFERENCES
[1]
Singh, A.,
Sharma, R. K., Agrawal, M., Marshall, M. L., 2010. Risk assessment of heavy
metal toxicity through contaminated vegetables from waste water irrigated area
of Varanasi, India, Tropical Ecology, 51(2S), and 375-387.
[2]
Wang, X.P., Shan,
X.Q., Zhang, S.Z. and Wen, B. 2004. A model for evaluation of the phytoavailability of trace elements to vegetables under
field conditions. Chemosphere, 55, 811–822.
[3]
Mapanda, F., Mangwayana, E. N., Nyamangara, J., Giller, K. E.,
2005. The effect of long-term irrigation using wastewater on heavy metal
contents of soils under vegetables in Harare, Zimbabwe. Agric. Ecosyst. Environ. 107, 151–165.
[4]
McBride, M. B.,
1994. Environmental Chemistry of Soil. Oxford University Press, Inc, New York.
[5]
Mohamed, A. E., Rashed, M. N., Mofty, A.,
2003. Assessment of essential and toxic
elements in some kinds of vegetables, Ecotoxicology and Environmental Safety, 55(3), 251-260.
[6]
Bosso, S.T. and Enzweiler, J.,
2008. Bioaccessible lead in soils, slag and mine
wastes from an abandoned mining district in Brazil. Environmental Geochemistry
and Health, 30, 219-229.
[7]
Fu, G., Zhou, Q.,
Liu, J., Liu, W., Wang, T., Zhang, Q. and Jiang, G., 2008. High levels of heavy
metals in rice (Oryza sativa L.) from a typical E-waste recycling area in
southeast China and its potential risk to human health. Chemosphere, 71,
1269-1275.
[8]
Lim, H.S., Lee,
J.S., Chon, H.T., and Sager, M., 2008. Heavy metal contamination and risk
assessment in the vicinity of the abandoned Songcheon
Au-Ag mine in Korea. Journal of Geochemical Exploration, 96, 223-230.
[9]
Agbenin, J.O., Danko. M. and Welp,
G., 2009. Soil and vegetable compositional relationships of eight potentially
toxic metals in urban garden fields from northern Nigeria. Journal of Science
Food and Agriculture, 89, 49-54.
[10]
Arora, M., Kiran,
B., Rani, S., Rani, A., Kaur, B. and Mittal, N., 2008. Heavy metal accumulation
in vegetables irrigated with water from different sources. Food Chemistry, 111,
811–815.
[11]
McBride M. B.,
2003. Toxic metals in sewage sludge-amended soils: has promotion of beneficial
use discounted the risks? Adv Environ Res., (8), 5-19.
[12]
Cao, Z. H., Hu,
Z. Y., 2000. Copper contamination in paddy soils irrigated with wastewater.
Chemosphere, 41 (1–2), 3–6.
[13]
Nyamangara, J., Mzezewa, J., 1999. The
effects of long-term sewage sludge application on Zn, Cu, Ni and Pb levels in
clay loam soil under pasture grass in Zimbabwe. Agric. Ecosyst.
Environ. 73, 199–204.
[14]
Singh, K. P.,
Mohon, D., Sinha, S., Dalwani, R., 2004. Impact
assessment of treated/untreated wastewater toxicants discharge by sewage
treatment plants on health, agricultural, and environmental quality in
wastewater disposal area. Chemosphere, 55, 227–255.
[15]
Nan, Z., Li, J.,
Zhang, Cheng, G., 2002. Cadmium and zinc interaction and their transfer in
soil–crop system under actual field conditions. Sci. Total Environment, 285,
187–195.
[16]
Tripathi R. M,
Raghunath R, Krishnamoorthy T. M., 1997. Dietary intake of heavy metals in
Bombay city, India. Sci Total Environment, 208, 149–59.
[17]
Cui, Y. L., Zhu,
R. H. Zhi, Chen, D. Y., Huang, Y. Z. And Qiu, Y., 2004.
Transfer of metals from soils to vegetables in an area near a smelter in
Nanning, China, Environ. Intl., 30, 785-791.
[18]
Gupta, S., Satpati, S., Nayek, S., Garai, D. 2010. Effect of wastewater irrigation on vegetavles in relation to bioaccumulation of heavy metals
and biochemical changes, Environ. Monit. Assess. 165,
169-177.
[19]
IRIS, 2003.
Integrated Risk Information System- database, US Envrion.
Protec. Agency.
[20]
Joint FAO/WHO
Expert Committee on Food Additives (1999). Summary and conclusions. In 53rd
Meeting, Rome, June 1–10.
[21]
Prevention of
Food Adulteration (PFA), 2000. Act no 37 of 1954. Central and State Rules as
Amended for 1999, Ashoka Law House, New Delhi.
[22]
Rattan, R. K.,
Datta, S. P., Chhonkar, P. K., Suribabu,
K., & Singh, A. K., 2005. Longterm impact of
irrigation with sewage effluents on heavy metal contents in soils, crops and
ground water – a case study. Agriculture, Ecosystem and Environment, 109,
310–322.
[23]
Pandey, J. Pandey, U., 2009. Accumulation of heavy
metals in dietary vegetables and cultivated soil horizon in organic farming
system in relation to atmospheric deposition in a seasonally dry tropical
region of India, Environ Monit Assess 148, 61–74.
[24]
Sharma, R.K.,
Agrawal, M., Marshall, F.M., 2006. Heavy metals contamination in vegetables
grown in waste water irrigated areas of Varanasi, India. Bulletin of
Environmental Contamination and Toxicology, 77, 311-318.
[25]
Sridhara Chary, N., Kamala C T, Samuel Suman Raj D., 2008.
Assessing risk of heavy metals from consuming food grown on sewage irrigated
soils and food chain transfer. Ecotoxicology and Environmental Safety, 69,
513–524.
[26]
Liu, W.X., Li,
H.H., Li, S.R., Wang, Y.W., 2006. Heavy metal accumulation of edible vegetable
cultivated in agricultural soil in the suburb of Zhengzhou city, People’s
Republic of China. Bulletin of Environmental Contamination and Toxicology, 76,
163-170.
[27]
Khan, S., Cao,
Q., Huang Y. M. and Zhu Y. G., 2008. Health risks of heavy metals in
contaminated soils and food crops irrigated with wastewater in Beijing, China.
Environ. Poll. 125(3), 686-692.
[28]
Radwan, M.A.
& A.K. Salama. 2006. Market based survey for some heavy metals in Egyptian
fruits and vegetables. Food and Chemical Toxicology, 44: 1273-1278.
[29]
Zhuang, P.,
McBride, M. B., Xia, H., Li, N., Li., Z., 2009. Health risk from heavy metals
via consumption of food crops in the vicinity of Dabaoshan
mine, South China, Sci Total Environ, 407, 1551–1561.
[30]
World Health
Organization (WHO). (1996). Health criteria other supporting information. In
Guidelines for Drinking water Quality, Vol. 2 (2nd Ed.). Geneva, (pp. 31–388).
[31] US-EPA, 2002. United States, Environmental Protection
Agency, Integrated Risk Information System. http://www.epa.gov/iris/subst
This work is licensed under a: Creative Commons Attribution 4.0 International License © IJOEST 2016-2020. All Rights Reserved. |