Open Journal of Metal, 2013, 3, 77-88
http://dx.doi.org/10.4236/ojmetal.2013.32A1010 Published Online July 2013 (http://www.scirp.org/journal/ojmetal)
Heavy Metal Contaminated Food Crops Irrigated with
Wastewater in Peri Urban Areas, Zambia
Evaristo Mwaba Kapungwe
Geography Department, University of Zambia, Lusaka, Zambia
Received February 28, 2013; revised April 3, 2013; accepted April 14, 2013
Copyright © 2013 Evaristo Mwaba Kapungwe. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Studies on peri urban farming in Zambia have not adequately tackled the issues pertaining to heavy metal contaminated
wastewater irrigation farming. The study investigated heavy metal contamination of water, soils and crops at two peri
urban areas in Zambia. Two study sites were New Farm Extension in Mufulira Town in the Copperbelt Province and
Chilumba Gardens in Kafue Town in Lusaka Province. The heavy metals investigated were lead, copper, cobalt, nickel
and chromium. These heavy metals were found to be higher than acceptable limits in wastewater used to irrigate crops
and there are potential human health risks associated with consumption of heavy metal contaminated food crops which
have implications on the livelihoods of people. Samples of water, soil and crops were collected and analysed for lead
(Pb), copper (Cu), chromium (Cr), cobalt (Co) and nickel (Ni) using the Atomic Absorption Spectrometer (AAS). The
data on heavy metals was analysed using mean, standard error and T-test. The results indicated that the levels of heavy
metals in wastewater, soil and food crops were above acceptable limits at two study sites. It can be concluded that there
was heavy metal contamination of wastewater, soil and food crops at the two peri-urban areas in Zambia. The study
highlighted the actual levels of heavy metal contaminant uptake in food crops consumed by the peri urban population.
The information from this study can be used by the relevant authorities to develop appropriate measures for monitoring
and control of heavy metal contamination in wastewater irrigation farming systems in peri urban areas in Zambia.
Keywords: Heavy Metal Contamination; Wastewater; Soils; Food Crops; Irrigation Farming; Peri Urban Areas;
Zambia
1. Introduction
Studies on wastewater irrigation crop farming in peri-
urban area in developing countries [1-5] identified chal-
lenges which include inadequate information on the tem-
poral changes in the levels of heavy metal in wastewater,
soils and crops [6]. Despite the challenges associated with
wastewater irrigation farming, it is a source of livelihood
for a large number of the urban poor in towns in devel-
oping countries. Although previous studies identified
benefits, risks, drivers and characteristics of wastewater
use in agriculture in developing countries, the wastewater
irrigation farming is either under-reported or underesti-
mated in some sub Sahara Africa countries [7-10].
Research on urban and peri urban agriculture con-
ducted in Zambia [11-17], Mulenga [18], Mulenga [19-
25] inadequately tackled the issues pertaining to heavy
metal contamination in wastewater irrigation farming
[26]. In Zambia, some of the urban crop cultivators use
wastewater from domestic sewage and industrial efflux-
ents to irrigate crops in their gardens [26]. Although the
wastewater might have potential value to peri-urban ag-
riculture through the provision of water and nutrients to
crops, there are potential health risks associated with
heavy metal contamination of wastewater. The sources of
heavy metals in wastewater include mining, smelting and
industrial activities in towns of Zambia [26]. There are
gaps in knowledge of the true extent of the heavy metal
contaminated wastewater use in crop farming in Zambia.
The study investigated heavy metal contamination of
water, soils and crops in wastewater irrigation farming at
two peri urban areas in Mufulira and Kafue towns of
Zambia. The heavy metals investigated were lead, copper,
cobalt, nickel and chromium. These heavy metals were
found to be higher than acceptable limits in wastewater
used to irrigate crops and there are potential human
health risks associated with consumption of heavy metal
contaminated food crops which have implications on the
livelihoods of people. It was hypothesised that there was
C
opyright © 2013 SciRes. OJMetal

E. M. KAPUNGWE
78
no significant difference in levels of heavy metal con-
tamination of water, soils and food crops in different sea-
sons at the two study sites. The information from this
study can be used by the relevant authorities to develop
appropriate measures for monitoring and control of
heavy metal contamination in wastewater irrigation farm-
ing systems in order to ensure food safety for urban and
peri-urban poor in Zambia.
2. Study Methods
2.1. Location of Study Areas
The two study sites were New Farm Extension in Mufu-
lira town in the Copperbelt Province and Chilumba Gar-
dens in Kafue town in Lusaka Province (Figure 1). Two
sampling plots were selected from the two study sites as
case studies for purpose of sampling of heavy metal con-
tamination in water, soil and crops in areas which used
wastewater to irrigate crops. One field plot was located
under the Copperbelt Energy Company power line at
New Farm Extension study site in Mufulira at latitude
12˚33.542' South and longitude 28˚12.950' East at the
elevation of approximately 1255 meters above sea level
(Figure 2). Another field plot was located adjacent to the
Zambia Electricity Supply Corporation (ZESCO) sub
station along Kasenje River at Chilumba Gardens study
site in Kafue at latitude 15˚45.251' South and longitude
28˚09.649' East at the elevation of approximately 989
meters above sea level (Figure 3).
2.2. Characteristics of Study Areas
The two study sites experienced tropical savanna climate
characterised by three typical seasons namely hot wet
(November to March); cool dry (April to July) and hot
dry (August to October) with 900 - 1000 mm per year of
rainfall [26]. The domestic sewage wastewater was use to
irrigate the crops at the sampling plot at New Farm in
Mufulira whilst the untreated effluents were use to irri-
gated crops at the sampling plot at Chilumba Gardens in
Kafue. There was a likelihood of heavy metal contami-
nation of crops produced using heavy metal contami-
nated wastewater. The sources of wastewater pollution at
New Farm in Mufulira include the domestic sewage dis-
charged into Kantanshi Stabilisation Pond was contami-
nated with higher levels of heavy metals because the
main source of raw water for domestic water supply was
from underground mining dewatering process. The sources
of wastewater pollution at Chilumba Gardens in Kafue
include discharges from industries located in Kafue In-
dustrial Area. The discharge from the Lee Yeast Factory
is mixed with untreated effluent from Kafue Chemicals
which manufactures industrial chemicals such as sodium
silicate and hydrochloric acid. The characteristics of
sampling plots at two study sites are summarised in Ta-
ble 1.
2.3. Sampling of Water, Soils and Crops
The water, soils, and crops were sampled from the two
sampling plots located at two study sites with the consent
of crop cultivators. Samples of wastewater, soils and
crops were collected on monthly basis from August 2004
to August, 2006. A total of thirty two water samples,
twenty two composite soil samples and forty five crop
samples were collected from the field plot at New Farm.
Table 1. Summarised characteristics of heavy metal sam-
pling plots at two study sites.
Province Copperbelt Lusaka
Town Mufulira Kafue
Study sites New Farm Extension Chilumba Gardens
Area of study
site and
control area
98.44 hectares 141.76 hectares
Location of
heavy metal
sampling plots
Latitude 12˚33.542'
South and Longitude
28˚12.950' East
Latitude 15˚45.251'
South and Longitude
28˚09.649' East
Elevation 1255 meters above
sea level 989 meters above sea level
Size of
sampling plot300 m2 (0.03 ha.) 1,325 m2 (0.1325 ha.)
Sources of
irrigation water
Kantanshi
Stabilisation Ponds
Kafue Chemicals and Lee
Yeast Factory
Type of
irrigation water
Primary treated
domestic sewage
Untreated industrial
effluents
Sources of
water pollutionMining activities Industrial processes
Transportation
of irrigation
water
Irrigation furrows and
was gravity aided
Kasenje River and was
gravity aided
Type of
irrigation
methods
Furrows in dry
and wet seasons
Buckets and plastic
containers during the dry
season whilst the field plots
experience flooding during
the wet season
Type of soilsClay loam,
reddish brown Clay, greyish brown
Land
management
Ridges and furrows,
raised beds, flat tillage,
mulching, sunken
beds and burning
Pot holing, mulching,
sunken beds and flat tillage
Types of
crops
Chinese cabbage,
tomatoes, Swiss chard,
pumpkin, beans,
okra and sugarcane
Chinese cabbage, tomatoes,
Swiss chard, pumpkin,
sweet potatoes, rape, maize
and sugarcane
Cropping
systems Mixed cropping system Mixed cropping system
Cropping
patterns
Sugarcane-vegetable
cropping
Sugarcane-maize-vegetable
cropping
Source: Field survey, 2004-2006 [26].

E. M. KAPUNGWE
79
Lake
Bangweulu
Lake
Mweru
Lake
Kariba
Itezhi tezhi
Dam
Chipata
Kasama Isoka
Mporokoso
Nchelenge
Mbala
Tunduma
Chama
Mpika
Serenje
Mkushi
Kapiri Mposhi
Ndola
Luanshya
Mufulira
Chilil abomb we
Kitwe
Solwezi
Mansa
Samfya
Kabwe
Petauke
LUSAKA Luangwa
Kafue
Namwala
Monze Siavonga
Livingstone
Senanga
Sesheke
Mongu
Kalabo
Lukulu
Mwinilunga
Zambezi Kasempa
Kabompo
Kaoma Mumbwa
International Boundary
Major Road
Railway
Study Towns
Other Tow ns
LEGEND
9 S
15 S
12 S
28
18 S
East 22
15 S
9
25
31
Capital City
Lake
Tanganyika
010020 0 km
28 22 E
12 S
RELATIVE LOCATION OF ZAMBIA IN SOUTHERN AFRICA
ZAMBIA
ZIMBABWE
BOTSWANA
ANGOLA
CONGO
D. R.
NAMIBIA
SOUTH
AFRICA LESOTHO
SWAZILAND
TANZANIA
KENYA
UGANDA
RUANDA
BURUNDI
CAMERON N
34
Figure 1. Location of Mufulira and Kafue study towns in Zambia [26].
The soil auger was used to obtain soil sub samples
from the depth of 0 - 20 cm from five places located ran-
domly in each sampling plot and the sub samples were
mixed in order to form a composite sample. The depth of
20 cm was chosen because the roots of crops penetrate to
such depth of subsoil to extract the necessary nutrients
and other elements needed for plant growth.
Furthermore a total of forty four water samples, twenty
seven composite soil samples and forty two crop samples
were collected from the another field plot at Chilumba
Gardens. The water, soils and crops samples were taken
to the laboratory for preparation of extract and determi-
nation of levels of heavy metals.
The water, soils and crops samples were collected us-
ing standard sampling methods [27,28]. Samples of wa-
ter were collected from stream channels and irrigation
furrows in the cultivated fields where the crop cultivators
drew water for irrigation of crops. The metal ions in the
water samples were mobilised through addition of diluted
nitric acid.
The samples of edible parts of food crops that were
collected from the two sampling plots at the two study
sites comprised sugarcane stalk, okra fruits, tomato fruits,
sweet potato leaves, Chinese cabbage leaves, Swiss chard
leaves, pumpkin leaves, bean leaves and rape leaves. The
eaves or fruits were collected randomly from the same l

E. M. KAPUNGWE
80
28 10’E
28 10’E
12 35’S12 35’S
0750 1500 metres
Planne d Settlements
Un-planned Settlements
Small Holding
Scattered Cultivation
Waste Water Irrigated Area
Commercial Farm
Sewer Pond
Water Bodies/Major River
Floodplain
Irrigation Channe l
Stream
Main Road
Other Ro a d
Footpath/Track
Power Line
Waste Water Channel
Slope
S t udy Site Boundary
Water Pollution Sources
Heavy Metal Sampling Plot
Domestic Sewage Water Flow
Mining Waste Water Flow
KAWAMA
WEST
KANKOYO
Kafue
CEC
Sub-
station
Data Source: Aerial photographs of Mufulira datedJuly/August 1993, Field Survey, 2006.
NEW
FARM
TAILING
TAILING
DAM
DAM
N
Figure 2. Location of Mufulira and Kafue study towns in Zambia [26].
plot where the soil samples were collected.
2.4. Preparation of Water, Soils and Crops
Extracts
Three standard preparation methods were used to prepare
extracts of water, soils and crops. The water and soil sam-
ples were prepared for analysis of bio-available heavy
metals whilst the crop plant materials were prepared for
analysis of total heavy metals [29].
The standard preparation method for preparation of
extracts of water included:
1) Decanting of water into beaker: A total amount of
100 ml of water was decanted in a 100 ml beaker after
water sample bottles were first shaken mechanically.
2) Filtration of water: The water was filtered using
Double Ring No. 102 filter papers in order to remove
fine particles and suspended materials which would have
affected the reading of heavy metals by the Atomic Ab-
sorption Spectrometer (AAS). The water filtrate was col-
lected for determination of bio-available heavy metals in
wastewater.
The standard methods of preparation of soils com-
prised of several stages ([29] which included):
1) Air drying and sieving of soil samples: The soil
samples were dried by placing them on shallow mela-
mine plastic trays in ambient air. The dried soils were
crushed gently and sieved through a 2 mm mesh size
steel sieve. The roots, gravel, stones, gravel and other
materials that remained on the sieve were discarded.
2) Addition of extraction solution to soil: A total of
forty milligrams (40 ml) of the Diethylene triamine pen-
toacetic acid (DTPA) extracting solution was mixed with
twenty grams (25 g) of dry soils sub-sample.

E. M. KAPUNGWE 81
0120
240 metres
18060
Data S ource: Aerial Photogr aphs of Kafu e dated July/August 1993. Field Survey, 2006
Planned Settlement
Un-planned Settlement
Small Holding
Scattered Cultivation
Waste Water Irrigated Area
Commercial Farm
Industrial Waste Water Ponds
Industrial Area
Study Site Boundary
Heavy Metal Sampling Plot
Main Road
Other Road
Footpath/Track
W as t e Wa te r Channel
Irrigation Channel
Power Line
Stream
Water Pollution Sources
Industrial Waste Water Flow
Industrial & Domest ic Sewage Flow
Naboye
High
School
Stadium
Kafue
Fire
Brigade
Lee
Yeast
King Quality
Tannery
Central
Body
Builders
Steel Plant
Motor
Workshop
ZESCO
S O L O B O N I
14 45’S 1445’S
28 09’E
28 09’E
African
Textiles
NCZ
Nitrogen
Chemicals
of
Zambia
Chem i c al Supp l y
and
Engineering
Kafue
Chemicals
KAFUE
ESTATES KAFUE
ESTATES
ZAMBIA
COMPOUND
C H I L U M B A
S I T E
N
Figure 3. Heavy metal sampling plot at Chilumba Gardens study site in Kafue [26].
3) Filtration of mixture: The mixture was filtered
through Double Ring No. 102 filter papers in order to
remove fine particles and suspended matters after me-
chanically shaking the mixture for two hours. The filtrate
was collected for determination of bio-available heavy
metals in soils.
The conventional wet destructive mixed acid digestion
method was used to prepare plant material extracts [30-
33] comprising:
1) Washing and oven drying of plant materials: The
plant samples were oven dried at temperatures around
60˚C for 24 hours after the plant samples were washed in
distilled water in order to remove the dirty.
2) Grounding and sieving of plant materials: The dried
plant materials that were not hard were ground in porce-
lain mortar with a pestle whilst the dried plant materials
that were very hard were ground in a motorised mill. A
sub sample of 1.0 g of ground plant material which was
sieved through a 1.0 mm mesh size was placed in a 100
ml beaker.
3) Addition of nitric acid to plant material: A total of
25 ml of concentrated Nitric acid (HNO3) was added to
plant sample in the beaker. The mixture was boiled in the
beaker covered with a glass lid. The digestion of acid
plant mixture was allowed to go on until all the organic
matter had been dissolved. The solution was cooled.
4) Addition of Perchloric acid to plant material solu-
tion: A total of 10 ml of distilled water, followed by 10
ml of Perchloric acid (HClO3) was added to the cooled
solution. A glass lid was placed on the beaker and solu-

E. M. KAPUNGWE
82
tion was boiled on a hot plate until the solution was clear
or when white fumes were seen coming from the solution
which indicated that the digestion had been completed.
The digested solution was cooled.
5) Addition of distilled water to digested solution: A
total of twenty five (25) ml of distilled water was added
to the cooled digested solution and the mixture boiled on
a hot plate. The digested solution was again cooled.
6) Digested solution filtered: The cooled digested so-
lution was filtered through the Double Ring No. 102 fil-
ter papers into a 100 ml volumetric flask and made up to
100 ml with distilled water. The plant filtrate was trans-
ferred into a 100 ml plastic container for the analysis of
heavy metals in crop plant materials using the AAS ma-
chine.
2.5. Determination of Heavy Metals in Water,
Soils and Crops
The water, soils and crops filtrates were taken to the
Atomic Absorption Spectrometer (AAS) Perkin Elmer A
Analyst 400 machine for reading of heavy metals [34].
The heavy metals analysed by the AAS included chro-
mium, nickel, copper, lead and cobalt. The AAS proce-
dures used to analyse heavy metals in the laboratory in-
clude:
1) Calibration of ASS using standards for each ele-
ment: The AAS was calibrated using standards for each
element. The AAS was calibrated using standards for
each element that are made in distilled water for water
samples. The AAS was calibrated using standards for
each element that are made in DTPA for soil samples.
The AAS was calibrated using standards for each ele-
ment made in 5% nitric acid for crop samples.
2) Reading of heavy metals in filtrates using the AAS
machine: Each element was read using specific lamps
depending on the elements (Table 2). For samples read-
ing higher than the highest standard, a dilution was done
and was used to bring to volume. A blank sample was
also read and the value of the blank was used in correct-
ing the readings of the samples. The machine was recali-
brated after reading 20 samples. After the concentrations
of the samples have been read on AAS, calculations were
then made for the elements in the original sample. The
details of AAS machine reading of levels of heavy metals
in filtrates are explained in Table 2.
2.6. Control the Quality of Laboratory Analysis
The quality of laboratory analysis of samples of soils,
wastewater and edible crops was occasionally checked.
Every 10th sample was a blank of distilled water but the
technician did not know it was a blank. Furthermore, soil
and hay reference samples were consistently place among
the sample extracts from soil and crops.
Table 2. Parameters set on the perkin elmer a analyst 400
atomic absorption spectrometer.
Lamp specification
Elements Band width
(nm)
Wavelength
(nm)
Lamp
current (mɅ)
Detection
limits
(mg/l)
Flame
type
Copper 0.7 324.8 15 - 25 0.001 Air
Lead 0.7 283.3 10 - 25 0.01 Air
Cobalt 0.2 240.7 15 - 25 0.006 Air
Chromium0.7 357.9 15 - 25 0.002 Air
Nickel 0.2 232.0 30 - 35 0.004 Air
2.7. Analysis of Data
The data analysis included:
1) Statistical analysis of data: The means and standard
errors were calculated for levels of heavy metals in
wastewater, soils and food crops which were presented in
tables. The hypothesis was tested using T-test values at
significance level of 0.05, two tailed [35,36].
2) Acceptable limits for water, soils and crops: The
levels of heavy metals in wastewater were compared
with Food and Agriculture Organisation (FAO) irrigation
water acceptable limits [37]. The levels of heavy metals
in soils were compared to European Union/United King-
dom legislative limits [38-40]. The levels of copper, lead
in the food crops at the two sites were compared to ac-
ceptable limits as set by Zambian legislative limits [41],
FAO/WHO guidelines [42], EC Standards [43], and UK
guidelines [44] and whilst chromium and nickel present
in crops were compared to acceptable limits as outlined
in the study on chemical speciation of heavy metals in
sewage sludge and related matrice [45]. The Ministry of
Environment Ontario Canada standards for cobalt in
crops were used as acceptable limits [46].
3. Results and Discussions
3.1. Heavy Metal Contamination of Wastewater
The results on the levels of heavy metals in wastewater
used to irrigate crops at the two study sites are shown in
Table 3.
The results indicated that levels of copper and chro-
mium in wastewater at New Farm were above the ac-
ceptable limits in the hot dry season (Tab le 3) whilst the
levels of copper, cobalt, chromium and nickel in waste-
water at Chilumba Gardens were above the acceptable
limits in the cool dry and hot dry seasons (Table 3). In
other words, there was heavy metal contamination of
wastewater at the New Farm in Mufulira and Chilumba
Gardens in Kafue.
The levels of cobalt in water indicated that there were
significant differences between New Farm and Chilumba
Gardens (T test = −3.55, df = 69, P < 0.05). The levels of

E. M. KAPUNGWE
83
cobalt in water were relatively higher at Chilumba Gar-
dens than New Farm because of the presences of the Ka-
fue Chemical Factory in the Kafue Industrial Area which
discharged the untreated effluents into the environment.
The levels of chromium water were significantly differ-
ent between New Farm and Chilumba Gardens (T test =
−2.27, df = 69, P < 0.05). The levels of chromium in
water were relatively higher at Chilumba Gardens than
New Farm because of the presences of the leather tan-
nery in the Kafue Industrial Area which discharged the
effluents of chromate salts into the environment.
The probable reason for heavy metal contamination of
wastewater in the hot dry season at New Farm in Mufu-
lira was that the domestic wastewater was laden with
heavy metals from copper processing at Mopani Copper
Mines in Mufulira. The probable reason for heavy metal
contamination of wastewater at the Chilumba Gardens
was that the main source of irrigation wastewater was
untreated effluent from Lee Yeast Factory and Kafue
Chemicals in Kafue Estate Industrial Area operated
throughout the year. The relatively high levels of heavy
metals in irrigation water at New Farm in Mufulira, Chi-
lumba Gardens in Kafue indicated heavy metal contami-
nation of water which was similar to the results from the
study at Firle Farm in Harare, Zimbabwe where vegeta-
bles were irrigated with admixtures of sewage and sew-
age sludge contaminated with heavy metals [47]. Fur-
thermore, the results from this study were similar to
findings from study on the Mwambashi catchment area
in the Copperbelt Province, Zambia which indicated that
mining activities have negative affected the water quality
along the Mwambashi River and its tributaries in both the
dry and wet seasons [48].
3.2. Heavy Metal Contamination of Soil
The results on the levels of heavy metals in soils at the
two study sites are shown in Table 4.
The results indicated that levels of copper in soils at
New Farm were above the acceptable limits whilst the
levels of heavy metals in soils at Chilumba Gardens were
within acceptable limits (Table 4). The levels of copper
Table 3. Heavy metals (mg/l) in water at New Farm and Chilumba Gardens study sites.
Seasons No. of samples Copper (Cu) Lead (Pb) Cobalt (Co) Chromium (Cr) Nickel (Ni)
New Farm Extension study site in Mufulira
Hot wet: Nov-Mar 13 0.08 ± 0.02 0.02 ± 0.01 ND ND 0.03 ± 0.01
Cool dry: Apr-Jul 7 0.04 ± 0.02 0.36 ± 0.25 0.03 ± 0.01 0.05 ± 0.02 ND
Hot dry: Aug-Oct 12 0.53 ± 0.17* 0.02 ± 0.01 ND 0.18 ± 0.07* 0.01 ± 0.00
Chilumba Gardens study site in Kafue
Hot wet: Nov-Mar 12 0.01 ± 0.02 0.03 ± 0.01 0.03 ± 0.02 ND 0.06 ± 0.01
Cool dry: Apr-Jul 19 0.06 ± 0.01 0.71 ± 0.33 0.09 ± 0.02* 0.21 ± 0.05 0.37 ± 0.17*
Hot dry: Aug-Oct 13 0.23 ± 0.04* 0.08 ± 0.04 ND 0.33 ± 0.09* 0.12 ± 0.02
aAO Heavy metal acceptable limits 0.2 5.0 0.05 0.1 0.2
ND = not detected; *Heavy metals above acceptable limits; Source of data: Field data, 2004-2005.
Table 4. Heavy metals (mg/kg) in soils at New Farm and Chilumba Gardens study sites.
No. of samples Copper (Cu) Lead (Pb) Cobalt (Co) Chromium (Cr) Nickel (Ni)
New Farm Extension study site in Mufulira
Hot wet: Nov-Mar 8 219 ± 25.34* 0.06 ± 0.44 0.14 ± 0.03 0.34 ± 0.01 12.8 ± 8.14
Cool dry: Apr-Jul 6 31.72 ± 8.70 0.50 ± 0.31 0.32 ± 0.08 0.21 ± 0.14 1.37 ± 0.70
Hot dry: Aug-Oct 8 58.62 ± 9.97 0.13 ± 0.07 0.22 ± 0.09 0.11 ± 0.06 0.22 ± 0.07
Chilumba Gardens study site in Kafue
Hot wet: Nov-Mar 10 6.48 ± 0.57 0.54 ± 0.94 0.38 ± 0.98 0.21 ± 0.00 0.52 ± 0.05
Cool dry: Apr-Jul 9 8.95 ± 1.67 2.08 ± 0.87 1.20 ± 0.18 0.11 ± 0.07 2.94 ± 1.23
Hot dry: Aug-Oct 8 6.15 ± 0.82 0.55 ± 0.20 0.23 ± 0.09 0.08 ± 0.06 0.35 ± 0.12
Heavy metal acceptable limits 130 - 140 450 - 300 240 130 - 150 50 - 75
ND = not detected; *Heavy metals above acceptable limits; Source of data: Field data, 2004-2005.

E. M. KAPUNGWE
84
were significantly different between New Farm and Chi-
lumba Gardens (T test = 4.95, df = 45, P < 0.05). The
relatively high levels of copper in soils at New Farm in
Mufulira can be attributed to the use of heavy metal con-
taminated wastewater in the irrigation of crops at the plot
and the relatively higher natural background levels of
copper in the soils which can contribute to high levels of
copper in the soils at New Farm because the New Farm
study site was located in copper ore mining areas in
Mufulira. The relatively high levels of copper in the soil
at New Farm can be compared to the average natural
background levels of copper ranged from 141 to 150
mg/kg in the Copperbelt region where mining activities
took place [49,50]. Generally, it can be argued that the
levels of copper in soil at New Farm in Mufulira were
greater than average background levels of copper in the
Copperbelt region.
The heavy metal contamination of soil at New Farm in
Mufulira was similar to findings from the study on heavy
metals in contaminated soils and food crops irrigated
with wastewater in Beijing, China indicated a substantial
build-up of heavy metals in wastewater irrigated soils
[51].
3.3. Heavy Metal Contamination of Crops
The results on the levels of heavy metals in crops at the
two study sites are shown in Table 5. The results indi-
cated that the levels of copper, lead, chromium and
nickel in the food crops exceeded acceptable limits. The
levels of cobalt in the food crops did not exceeded ac-
ceptable limits. It can be argued that there was heavy
metal contamination of food crops at the two study sites.
The highest levels of heavy metals in food crops were
recorded during the wet season. Some crops were con-
taminated by heavy metals whilst other crops were not
contaminated with heavy metals at the two study sites
(Table 5). The results from this study indicated that
some crops are less sensitive and can grow where the
metal loading rates are higher which confirmed that dif-
ferent plant species have different capacity and capability
to accumulate the heavy metals [52-54].
The levels of copper in sugarcane were significantly
different at New Farm and Chilumba (T test = 5.64, df =
22, P < 0.05). The relatively high levels of copper in
sugarcane stalk stem at New Farm in Mufulira can be
attributed to domestic wastewater laden with copper from
copper processing [55,56] and higher natural copper back-
ground levels in the soils.
The findings from this study indicated that there was
heavy metal contamination of food crops at the two study
sites were similar to the results from other studies in de-
veloping countries. The study on wastewater irrigation
farming in Varanasi, India which indicated that there
were seasonal differences in the heavy metal concentra-
tions in the edible portion of Beta vulgaris [57]. The re-
sults from this study confirmed the findings from the
study on heavy metals uptake by vegetable crops from
metal contamination in Tehran, Iran [58]. It can be ar-
gued that there are potential health risks for the urban
population who consume these vegetables and other food
crops which have high levels of heavy metals that above
the maximum recommended values by relevant authori-
ties.
4. Conclusion
It can be concluded that there was heavy metal contami-
nation of wastewater, soil and food crops at the two peri-
urban areas in Zambia. The implications for the heavy
metal contaminated of irrigation wastewater, soils and
food crops are four fold. Firstly, the treated domestic sew-
age wastewater and untreated industrial effluents were
not suitable for crop irrigation. Secondly, there is the like-
lihood of soil toxicity through accumulation of bio-
available forms of heavy metals and fate of organics in
soils; transfer of heavy metal contaminations to crops.
Thirdly, the crops which recorded heavy metal contami-
nation can be used as key indicators of heavy metal con-
tamination in the cropping systems. Fourthly, there are
potential health risks associated with consumption of
heavy metal contaminated food crops grown in waste-
water irrigation farming systems in peri-urban areas in
Zambia. Despite the inherent dangers and the potential
health risks associated with consumption of heavy metal
contaminated food crops, it is a source of livelihood for a
large number of the urban poor in towns of Copperbelt
and Lusaka Provinces, Zambia. There were significant
differences between New Farm and Chilumba Gardens in
the levels of heavy metal contamination of wastewater,
soil and crops in different seasons which implies that
there were temporal and spatial variations in the levels of
heavy metal contamination of water, soils and vegetables
at the two study sites. Previous studies indicated that
heavy metal contamination usually occurred mostly in
the Copperbelt province, Zambia whilst this study inden-
tified that heavy metal contamination took place in the
Lusaka and Copperbelt provinces in Zambia .The results
from this study confirmed the findings from other studies
in developing countries. The information from this study
can be used in the planning and development of safe
wastewater irrigation farming systems in peri urban areas
in Zambia.
5. Acknowledgements
The DFID UK project R8160 provided the funds to fa-
cilitate data collection. The Staff Development Office in
the University of Zambia granted the study leave which

E. M. KAPUNGWE 85
Table 5. Heavy metals (mg/kg) in food crops at New Farm and Chilumba Gardens study site.
No. of samples Copper (Cu) Lead (Pb) Cobalt (Co)Chromium (Cr) Nickel (Ni)
New Farm Extension study site in Mufulira
Chinese cabbage leaves (Brassica oleracea var. chinensis: Cruciferae family)
Cool dry: Apr-Jul 2 0.54 ± 0.54 0.75 ± 0.05* 4.71 ± 4.69ND 0.44 ± 0.20
Hot dry: Aug-Oct 4 ND ND ND 0.31 ± 0.18 0.01 ± 0.01
Tomato fruits (Lycopersium esculentum: Solanaceae family)
Hot wet: Nov-Mar 1 91.0* 17.8* 10.00 153.4* 31.1*
Cool dry: Apr-Jul 1 0.552 0.4* ND ND 0.72
Hot dry: Aug-Oct 4 3.57 ± 1.41 ND ND 0.18 ± 0.14 0.02 ± 0.02
Swiss chard leaves (Beta vulgaris subsp. Cicla: Cruciferae family)
Hot wet: Nov-Mar 4 6.08 ± 2.27 0.105 ± 0.09 ND 0.29 ± 0.15 ND
Cool dry: Apr-Jul 3 0.9 ± 0.92 0.67 ± 0. 03* 3.83 ± 3.77ND 0.29 ± 0.17
Hot dry: Aug-Oct 1 525.2* 17* 12 104.6* 20.6*
Pumpkin leaves (Cucurbita moscheta/curcurbita maxi ma: Cucurbitaceae family)
Hot wet: Nov-Mar 1 789* 24.5* 20.0 159.9* 31.6*
Hot dry: Aug-Oct 2 11.12 ± 4.17 0.31 ± 0.31* ND 0.12 ± 0.12 0.06 ± 0.06
Bean leaves (Phaseolus vulgaris, Legumiosoe family)
Hot dry: Aug-Oct 1 12.2 ND ND 0.24 ND
Okra fruits (Abelmoschus esculentus/Clemson spineless Malvaceae family)
Hot wet: Nov-Mar 3 71.02 ± 55.00* 5.5 ± 4.50* 2.05 ± 1.6236.46 ± 27.73* 10.82 ± 8.73*
Sugarcane stem (Saccharum officinarum: Graminae family)
Cool dry: Apr-Jul 15 29.45 ± 2.03* 12.09 ± 1.27* 1.91 ± 0.514.21 ± 1.20* 6.19 ± 1.42*
Hot dry: Aug-Oct 3 22.46 ± 1.33* 36.1 ± 3.42* 1.67 ± 0.4213.87 ± 0.78* ND
Chilumba Gardens study site in Kafue
Chinese cabbage leaves (Brassica oleracea var. chinensis: Crucifarae family)
Cool dry: Apr-Jul 1 0.54 0.54 0.02 ND 12.91*
Hot dry: Aug-Oct 1 ND ND ND 1.12 ND
Tomato fruits (Lycopersium esculentum: Solonacae family)
Cool dry: Apr-Jul 1 ND 0.68 0.04 ND 0.3
Hot dry: Aug-Oct 3 5.58 ± 4.17 ND ND 0.60 ± 0.27 ND
Swiss chard leaves (Beta vulgaris subsp. Cicla: Crucifarae family)
Cool dry: Apr-Jul 1 0.202 ND 0.06 ND ND
Pumpkin leaves (Cucurbita moscheta/maxima: Cucurbitae family)
Hot wet: Nov-Mar 3 77.56 ± 74.19* 4.07 ± 4.07* 6.38 ± 6.3151.58 ± 49.69* 12.87 ± 12.76*
Cool dry: Apr-Jul 3 1.02 ± 0.54 0.34 ± 0.17 0.07 ± 0.040.69 ± 0.69 6.09 ± 3.50*
Hot dry: Aug-Oct 3 3.17 ± 1.33 0.21 ± 0.21 ND 0.85 ± 0.55 ND
Sweet potato leaves (Ipomoea batata: Libiatae family)
Hot wet: Nov-Mar 4 2.46 ± 1.35 0.12 ± 0.12 ND 0.48 ± 0.27 ND
Cool dry: Apr-Jul 4 0.89 ± 0.45 0.46 ± 0.23 0.06 ± 0.030.38 ± 0.19 3.72 ± 1.86*

E. M. KAPUNGWE
86
Continued
Hot dry: Aug-Oct 5 62.98 ± 61.76* 10.02 ± 10.20* 1.83 ± 1.7942.94 ± 36.90* 6.34 ± 6.22*
Rape leaves (B rassica napus: Cruciferae family)
Hot wet: Nov-Mar 3 1.64 ± 1.50 ND ND 0.82 ± 0.41 0.03 ± 0.02
Cool dry: Apr-Jul 4 0.71 ± 0.60 0.40 ± 0.16 0.06 ± 0.030.32 ± 0.32 1.95 ± 0.75
Sugarcane stem (Saccharum officinarum: Graminae family)
Cool dry: Apr-Jul 3 3.97 ± 1.58 9.07 ± 5.68* ND ND ND
Hot dry: Aug-Oct 3 12.77 ± 1.78 35. 57 ± 1.24* 1.27 ± 0.6611.43 ± 1.45* ND
Heavy metal acceptable limits 20 - 50.0 0.3 - 2.0 50 1.0 2.0
ND = not detected; *Heavy metals above acceptable limits; Source of data: Field data, 2004-2006.
facilitated the author to conduct research. The Chief Car-
tographer Mr. J. Chilila and Assistant cartographer Ms A.
Nguluwe assisted in the drawing the maps. The Techni-
cians in the Department of Soil Science laboratory in the
School of Agricultural Sciences at the University of
Zambia assisted in the analysis of heavy metals in waste-
water, soil and crops.
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