assessment of heavy metals concentration in a waste

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Assessment of heavy metals concentration in a

waste dumpsite at Onitsha, Nigeria

Emmanuel I Iwuchukwu1, Anthony C Ekeleme2, Ogedi H Ibearugbulem3, Jude

Ugwuegbulam3, Okechukwu P Ibe3

1. Department of Agricultural and Bio-Environmental Engineering, Federal Polytechnic, Nekede, Owerri Imo State, Nigeria

2. Department of Civil Engineering, University of Nigeria, Nsukka, Enugu State, Nigeria

3. Department of Civil Engineering Federal Polytechnic Nekede Owerri, Imo State Nigeria

Corresponding author:

Anthony Chibuzo Ekeleme

Department of Civil Engineering, University of Nigeria, Nsukka, Enugu State, Nigeria,

GSM Number: +234 703 874 0504,

Email address: [email protected]

Article History

Received: 07 June 2018

Accepted: 30 July 2018

Published: August 2018

Citation

Emmanuel I Iwuchukwu, Anthony C Ekeleme, Ogedi H Ibearugbulem, Jude Ugwuegbulam, Okechukwu P Ibe. Assessment of heavy

metals concentration in a waste dumpsite at Onitsha, Nigeria. Discovery Science, 2018, 14, 41-49

Publication License

This work is licensed under a Creative Commons Attribution 4.0 International License.

General Note

Article is recommended to print as color version in recycled paper. Save Trees, Save Nature.

ABSTRACT

The soil quality of a municipal solid waste dumpsite in Onitsha-Owerri road, Onitsha southeastern Nigeria was investigated for

possible pollution impacts. Soil samples were collected from three sampling points each located within the dumpsite and a control

away from the dumpsite at 0–15, 15–30 and 30–45cm depth profiles. Toxic metals were analyzed with the Atomic Absorption

Spectrophotometer. Mean Ni, Fe, Pb, Mn, Zn, Cr and Cd concentrations were 2.04 ± 0.53, 287.14 ± 69.76, 16.12 ± 4.16, 90 ± 18.12,

91.11±19.88, 16.52 ± 4.01 and 9.54± 1.49 mg/kg. The one-way analysis of variance (ANOVA) test revealed that the levels of the

ANALYSIS Vol. 14, 2018

Science ISSN 2278–5485

EISSN 2278–5477

DISCOVERY


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edaphic parameters differed significantly across the soil depths [F(11.24) >Fcrit(3.97)] at P<0.05. A post-hoc means plots that utilized

the middle soil profile (30-45cm soil depth ) as predictor variable revealed that at the top (0-15cm depth) and bottom (30-45cm

depth) soil profiles, Mn (160.20mg/kg), Zn (191.00mg/kg) and Fe (600.20mg/kg) contributed mostly to the observed differences. The

edaphic variables measured in this study revealed very significant interactions. All the variables correlated significant with the heavy

metals at P<0.01. The wastes at the dumpsite impacted on the overlying soil pedons as well as the high porous sand compositions

and high toxic metal levels could make groundwater aquifer of the area vulnerable to pollution from surface point source.

Key Words: Heavy Metal, Solid Waste, Toxic, Soil, Absorption, Pollution.

1. INTRODUCTION

Increase in population and rapid increase in industrial processes particularly in major cities have resulted in negative environmental

consequences. Industrial pollution gave birth to environmental pollution and the greater volume of industrial chemical discharges

has added to the growing pack of untreated domestic waste which contains heavy metals. The discarding of domestic, commercial

and industrial wastes which may contain toxic materials such as Pb, Cu, Cd, Hg, Mn, Zn from battery, insecticides, nail polish cleaners,

polyvinyl chloride made containers, pesticides and other various products in the world is a problem that continues to grow with

human development. Research has shown that most forms of waste disposal techniques have side effect on the environment, public

health, and local economies. Municipal solid wastes refer to non-liquid wastes emanating from residential, recreational, treatment

plant sites and commercial activities [1]. Numerous hazardous heavy metals are inhaled by humans and animals almost every day.

The major concern with heavy metals is their ability to accumulate in the environment, thereby passing up the food chain.

Heavy metals are very harmful because of their non-biodegradable nature, long biological half-lives and their potential to

accumulate in different body parts. Most of the heavy metals are extremely toxic because of their solubility in water. Even low

concentrations of heavy metals have damaging effects to man and animals because of limited mechanism for their elimination from

the body. Nowadays heavy metals are ubiquitous because of their excessive use in industrial applications [2]. Wastewater contains

substantial amounts of toxic heavy metals and these which create problems. Vegetables take up heavy metals and accumulate them

in their edible and inedible parts in quantities high enough to cause clinical problems both in animals and human beings [3].Shute

and Macfie [4] studied cadmium and zinc accumulation in soybeans and their findings reinforce the need to monitor concentrations

of toxic metals in food crops.

The indiscriminate refuse dump in Onitsha, Anambra State posed a great health risk to the environment and residents. This is

more so because the heavy metals infiltrates the aquifer. This study thus aimed at assessing the concentration of heavy metals in a

waste dumpsite located in Onitsha, Nigeria. This study will provide baseline data for planning and executing proper waste

management. It will also serve as a veritable reference material in sensitizing the public on how to dispose waste materials.

2. MATERIAL AND METHODS

2.1. Study Area and Sampling

Onitsha municipal solid waste dumpsite is located at Latitudes 60 10’N and Longitudes 60047’E respectively. This dumpsite has been

in use for about 20years. The dumpsite is surrounded by some industrial factories, gasoline stations, motor parks, automobile spare

parts market, hospital and electrical parts markets. Generally, the wastes are mainly of domestic, industrial, medical and agricultural

origin. Three sampling points were randomly established at the major waste dumpsite with the use of a stainless hand-held soil

auger. Soil samples were collected at 0-15, 15-30 and 30-45 cm depths. Soil samples were then transferred into well labeled

polyethene bags and taken to the laboratory for various analyses.

2.2. Global Positioning System (GPS)

With the use of a GARMIN 76CS GPS meter, the GPS coordinates, including elevation of the sampling points were measured.

Table 1 GPS coordinates of sampling locations within the waste dumpsite in Onitsha

Sampling points

1 2 3 Control

Northing 480 23’ 01” 480 23’ 18” 480 24’ 37 500 42’ 71”

Easting 230 28’ 13” 230 27’ 41” 230 27’ 17” 150 28’ 24”


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Figure 1A section of the dumpsite in Onitsha, Anambra State

2.3. Laboratory analysis

The laboratory analysis of heavy metals and other soil properties was carried out in Transcontinental Protech Nigeria Limited,

Portharcourt. Standard practices as specified under DPR Guidelines and standards, as well as international analytical procedures

according to APHA [5] were observed.

Soils were dried at ambient temperature (25°C), crushed in porcelain mortar and sieved through a 2 mm (10 mesh) stainless

sieve. Air dried (<2 mm) samples were stored in polyethene bags for subsequent analysis. The <2 mm fraction was used for the

determination of selected soil physicochemical properties. One gram of the sample was introduced into a digesting tube following

the addition of 10ml concentrated HNO3. The samples were placed in the digester for 8hrs at 96 ºC with intermittent stirring. Upon

complete digestion, the samples were filtered into 100 mL volumetric flask using Whatman No. 42 filter paper. Samples were made

up to 100 mL mark in the volumetric flask using distilled deionized water. The concentrations of Pb, Cd, Zn, Cr, Ni, Mn and Fe in the

supernatant solution were determined using Varian Spectra AA 600 atomic absorption spectrophotometer (AAS), with air acetylene

flame connected to it. The soil pH was measured in 1.25 slurry of soil in water using Corning pH meter model 7 [5]. The pH was

determined by dipping the electrode into the 1:25 soil water suspension that had been stirred and allowed to equilibrate for about

1hour.

Soil moisture content was determined by using an oven dry method in which samples were dried to constant weight and the

difference in mass of wet and dry samples recorded and expressed in percentage.

In doing this, about 20 g of wet soil sample placed in a container was weighed and its mass, M recorded. The soil sample was

then dried in an oven at 105-110 0C for about 24h when it becomes perfectly dry. It’s dry mass, Md was then determined and the

water content calculated from the relation:

W =Ww

Wd∗ 100% (1)

MC =Ww − M

Wd − M∗ 100% (2)


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Moisture Content =Ww − M

Wd − M∗ 100% (3)

Where mass of the empty container = M

Mass of wet soil + empty container = Ww

Mass of oven dry soil + empty container =Wm

Bulk density was determine by the core method as modified by Evans et al. [6].

Particles Size Distribution was carried out by the Bouyoucous hydrometer method as modified by Day [7]. The soil sample was

dispersed with solution of sodium hexametaphosphate (Calgon 44g/L) and sodium carbonate (8 g/L). The pH of the solution was

maintained at about 8.3. The textural class was determined using the textural triangular diagram.

3. RESULTS AND DISCUSSION

This study revealed that the range heavy metal concentrations at the Onitsha dumpsite for Fe, Mn, and Zn were 0.02- 610.20, 1.26 –

169.84 and 2.15-190.15 mg/kg respectively. Such high values suggest that the waste deposits had conferred higher moisture

contents and bulkier densities to the underlying soil pedons thereby aiding moistures the dissolution of more toxic metals from the

waste streams. The concentration of metals in uncontaminated soils of this study may be, for the most part associated with the

geology of the parent substance from which the soil was formed [8], [9], [10], [11], [12] and so does not necessarily imply pollution.

Obviously, significantly higher metal levels were recorded in the less acidic than the more acidic (control) locations in this study. The

order of abundance of the metals in the impacted site was Fe>Zn>Mn>Cr>Pb>Cd>Ni. Decreasing concentrations with depth,

especially of Cd, Cr, Zn and Pb was observed, and this can be attributed to direct contacts with waste sources at the dumpsite,

leading to the concentration of pollutants in the topsoil. The high concentration of Fe at the site most probably was due to the large

number of steel and iron fabrication industries in Onitsha. Other possible sources could be the paper and magazine production

industries which [13] had observed could contribute to high Fe in waste dumpsites. Fe is the most widely used of all metals;

including 95% of metal tonnage are produced worldwide and excessive exposure to it may cause conjunctivitis, and retinitis in the

tissue [14]. Even as Chronic inhalation of excessive concentrations of Fe or its dust may also result in pneumoconiosis [15].

Figure 2 Spatial variations in Ni, Cd and Cr ions concentrations in the waste dumpsite.

The disposal of waste material containing discarded Zn roofing materials and the combustion of waste materials are probably

the major sources of Zn whose concentration was also high at the dumpsite. [16] observed that high Zn concentrations could also

come from the decomposition of electrical materials, roofing sheets, cooking utensils, alloys, electroplating and chemical effluents.

Zinc may increase the acidity of waters and some fish can accumulate it in their bodies when they live in Zn-contaminated

0

5

10

15

20

25

30

35

40

45

SP 1(0-15) SP 1(16-30) SP 1(31-45) SP 2(0-15) SP 2(16-30) SP 2(31-45) SP 3(0-15) SP 3(16-30) SP 3(31-45)

He

avy

me

tal

con

cen

trat

ion

(m

g/kg

)

Sampling points(depths in cm)

pH Ni Cd Cr


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waterways. When Zn enters the bodies of these fish, it is able to bioaccumulate and biomagnify up the food chain. Water–soluble

zinc that is located in soils can even contaminate groundwater. Plants often have a Zn uptake that their systems cannot handle due

to its accumulation in soils. Zn has been noted to also interrupt the activity of microorganisms and earthworms in soil, thus retarding

organic decompositions [17].

Figure 3 Spatial variations in Fe, Mn, Zn and Pb ions concentrations in the waste dumpsite

Figure 4 Spatial variations in sand, silt, clay and moisture contents of soils in the waste dumpsite

0

100

200

300

400

500

600

700


He

avy

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tals

Co

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ntr

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(mg/

kg)

Sampling points(Depths in cm)

Fe Mn Zn Pb

0

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30

40

50

60

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80


Co

mp

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con

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)

Sampling points(Depths in cm)

Sand Silt Clay M. content


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Figure 5 Means plot in edaphic parameters between the middle (15-30cmdepth) and top (30-45cmdepth) soil profiles

Figure 6 Means plot in edaphic parameters between the middle (0-15cm depth) and bottom (30-45 cm depth) soil profiles

According to [18] and [19], the major man-made sources of environmental manganese include municipal wastewater discharge,

sewage sludge, emissions generated during alloy, steel and iron production and to a lesser extent emissions from the combustion of

fuel additives. Land disposal of Mn–containing waste is the principal source of manganese release to soil [20] and it is an essential


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trace element for microorganisms, plants and animals. The uptake of manganese by humans mainly takes place through food and its

effects occur mainly in the respiratory tract and brain. Symptoms of Mn poisoning are hallucinations, forgetfulness and nerve

damage. Manganese can also cause Parkinson, lung embolism and bronchitis. When men are exposed to manganese for a longer

period of time, they may become impotent. A syndrome that is caused by manganese has symptoms such as schizophrenia,

dullness, weak muscles, headaches and insomnia [15].

Major sources of Cr contamination include releases from electroplating processes and the disposal of Cr containing wastes [21],

which are the activities that are prominent in Onitsha. Chromium has been associated with allergic dermatitis in humans [22].

The high Pb concentrations recorded may have been contributed by Pb containing waste materials like batteries, discarded

plumbing materials and solders which are commonly discarded from the Onitsha main market. High Pb concentration in soil, could

lead to uptake by plant and food crops and subsequent bioaccumulation and biomagnifications in the food chain. Inhalation and

ingestion are the two routes of exposure, and the effects from both are the same, especially when it accumulates in the body (brain,

nervous system, red blood cells, kidney) leading to poisoning (plumbism) or even death [23]. The gastrointestinal tract, kidneys, and

central nervous system are also affected; Children exposed to it are at risk of impaired development, lower IQ, shortened attention

span, hyperactivity, and mental deterioration [24]. Adults usually experience decreased reaction time, loss of memory, nausea,

insomnia, anorexia, and weakness of the joints when exposed to Pb [24].

It is known that the application of agricultural inputs such as fertilizers, pesticides, and bio-solids (sewage sludge), as well as the

disposal of industrial wastes or the deposition of atmospheric contaminants increases the total concentration of Cd in soils, and that

the bioavailability of this metal determines whether plant–Cd uptake occurs to a significant degree [25]. The high concentration of

cadmium at the impacted site may be due to the decay of abandoned electric batteries and other electronic components [26], which

are commonly disposed of in Onitsha. Cadmium in the body is known to affect several enzymes and it is believed that the renal

damage that results in proteinuria is the result of Cd adversely affecting enzymes responsible for re-absorption of proteins in kidney

tubules. The high counts recorded for the total coliforms reflect the disposal of human excreta at the waste dumpsite. This

unsanitary activity is common in such a congested city as Onitsha where adequate sewage systems are lacking.

Sand dominated the composition of soils of the waste dumpsite, and this agrees with the findings [27] regarding the geology

and hydrogeology of the area. Sandy formation is porous and permeable and this implies that leachate from dumpsites could

migrate easily into the unconfined shallow aquifer to contaminate the groundwater system. According to [28], the average linear

groundwater flow in the area is approximately 430 m/yr while leachate moves at about 6.5 km away from its source in every 12 years

interval. These findings suggest that soil contamination via dumpsites plume is inevitable on the long-run due to accumulation

effects. Although the contamination in this study appears localized at the topsoil, the subsoil also showed presence of certain heavy

metals (Cd, Zn and Pb) at elevated levels which may constitute pollution in future if the dumping of refuse persists at the site. This

again agrees especially with the findings of [29].

The relationships between pH and the metals collaborates observed reduced acidification conferred by the waste stream on

underlying soils. The slightly inverse relationship between clay and the metals, and the highly positive one between sand and the

metals indicate the respective inhibitory and enhancing roles of the soil textural classes to the migration of metal pollutants.

4. CONCLUSION

The levels of toxic metals, especially Pb, Cd and Zn, heterotrophs and coliform bacteria detected in the study were very high in soils

of the waste dumpsite in Onitsha. High microbial counts depict considerable levels of decomposition and biodegradation activities

at the dumpsite. Industrial, commercial and domestic activities were the major contributors of heavy metals whose concentrations

decreased with depth of soil. Soil composition at the dumpsite was dominated by sand. The soil quality of the waste dumpsite was

negatively impacted by the introduction of high levels of toxic metals from waste streams. The predominance of sand in the waste

dumpsite predisposes groundwater aquifer to localized contaminations with the persistent pollutants from surface point sources.

Therefore, federal and state regulatory agencies such as the Federal Ministry of Environment (FEPA), NESREA, Anambra State

Environmental Protection Agency etc. should enforce stiffer penalties to waste disposal regulation offenders which would discourage

individuals and corporate bodies from dumping wastes in unauthorized places.

Author Contributions

Emmanuel. I. Iwuchukwu (EII), Anthony. C. Ekeleme, (ACE), Ogedi .H. Ibearugbulem, (OHI), Jude Ugwuegbulam (JU), Okechukwu .P.

Ibe (OPI)

This study was carried out in collaboration amongst all authors. Authors EII, ACE and OHI designed the study, wrote the protocol

and edited the manuscript. Authors EII, JU, OPI managed the literature searches, statistical analyses of the study, wrote the first draft


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of the manuscript and editing of the manuscript. ACE managed the literature searches and the experimental process. All authors

read and approved the final manuscript

Conflict of interest

Declared none

Funding Source

None

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