African Journal of
Environmental Science and Technology

  • Abbreviation: Afr. J. Environ. Sci. Technol.
  • Language: English
  • ISSN: 1996-0786
  • DOI: 10.5897/AJEST
  • Start Year: 2007
  • Published Articles: 1038

Full Length Research Paper

Seasonal impact on phyto-accumulation potentials of selected edible vegetables grown in Ishiagu quarry mining effluent discharge soils

Osuocha K. U
  • Osuocha K. U
  • Department of Biochemistry, Abia State University Uturu, Abia State, Nigeria.
  • Google Scholar
Akubugwo E. I
  • Akubugwo E. I
  • Department of Biochemistry, Abia State University Uturu, Abia State, Nigeria.
  • Google Scholar
Chinyere G. C
  • Chinyere G. C
  • Department of Biochemistry, Abia State University Uturu, Abia State, Nigeria.
  • Google Scholar
Ugbogu A. E
  • Ugbogu A. E
  • Department of Biochemistry, Abia State University Uturu, Abia State, Nigeria.
  • Google Scholar

  •  Received: 28 August 2015
  •  Accepted: 18 September 2015
  •  Published: 31 January 2016


Seasonal impact on soil trace metals and phytoaccumulation potentials of Cucurbita pepo, Cucumis sativus and Taliferia occidentalis grown in Ishiagu quarry mining effluent discharge soils were investigated. Soil samples were collected 200 m (sample C), 100 m (sample B) away from discharge point (sample A) in wet and dry seasons. Trace metals were analysed using atomic absorption spectrophotometer. Results reveal a significant decrease in levels of trace metals distance away from discharge points in the order A>B>C. Findings from the study show significant increase in level of soil trace metals in dry season compared to wet season. Phyto-accumulation potentials of the vegetables showed significant increase in level of trace metals in roots and shoots in dry season compared to wet season. Level of these metals were significantly higher compared to control. This is indicative of the potential risk associated with consumption of vegetables grown in these sites especially in dry seasons. The rural dwellers should be discouraged from planting edible vegetables around Ishiagu quarry mining effluent discharge soils in order to reduce excessive build-up of these metals in the human food chain.


Key words: Phyto-accumulation, trace metals, quarry mining, discharge soils, seasonal impact.


Mining activities are well known for their deleterious effect on the environment due to deposition of large volume of waste on the soil. Adverse environmental consequences of open pit mining include land degradation arising from vegetation destruction, exposure of the soil to run-off water as well as dumps that have been confirmed as having harmful minerals and chemicals that contaminate the soil, plant, water and air quality (Osuocha et al., 2015). Mining activities generate a variety of wastes whose presence in soils have adverse effects on plant growth, such as low water infiltration rates, rough surfaces, poor aeration, high level of trace metals, low soil fertility, salinity and extremes of pH (Monty and Amiya, 2012). Ezeh (2007) and Nwaugo et al. (2009a) reported that mining activities are sources of environmental pollution and degradation through the introduction of chemicals above their threshold limit into the environment as wastes generated in the mining process are often discharged into the surrounding environment especially in developing countries. Environmental impacts of such mining operations are potentially long lasting due to destruction of vegetation, surface runoff of organic matter and the overall degradation of soil structure affecting plant and microbial growth.

According to Oluyemi et al. (2008), disruption of the existing balance in the soil usually leads to reduction in its productivity and quality of agricultural products as soil is a vital resource for sustaining two human needs of quality food supply and quality environment. The concentration of these trace elements in soils are associated with several factors such as biological and biogeochemical cycling, parent materials and mineralogy, soil age, organic matter, soil pH, redox concentration and microbial activities (Kabata-pendias, 2004; Obasi et al., 2013). Plants are one pathway for toxic metal mobiliza-tion into the human system. Elevated environmental concentration of these trace metals are a particular issue in mining areas because of their documented deleterious human health effect such as DNA, kidney and liver damage, skin and lung cancer caused by their mutagenic ability, neurotic effect and anaemia from lead poisoning, gingivitis as well as alteration of body metabolism (Duruibe et al., 2007). The determination of elemental status of cultivated land is necessary to identify yield limiting deficiencies of essential nutrients and level of polluted soils. This is important especially in Ishiagu because the inhabitants are essentially farmers and large quantities of crops and vegetables are produced not only for local consumption but also for food supplies to other parts of Nigeria.


Study area

This study was carried out with mining effluents contaminated soil samples from Ishiagu in Ivo local Government Area of Ebonyi State. The rural settlers are mainly peasant farmers with most farm products as cassava, vegetables, yam, cocoyam and rice. Quarry sites of leads and zinc are the major industrial activities in Ishiagu. These ever increasing quarry industries dispose their wastes into nearby farm lands and these farms are cultivated by the rural settlers (Figure 1).



Three (3) different mining effluent contaminated soils in Ishiagu, Ivo Local Government Area of Ebonyi State were used for this study. The quarry sites include:

(i) Crush rock industries in Ano community,

(ii) Eza west Africa limited in Eziato community and

(iii) Crush stone industries in Amita village.


Soil sample collection

Three (3) different locations were used for the analysis from each quarry mining site. The soil samples were thoroughly mixed before collection at a depth of 0-50 cm. Points of collection were 100 m (sample B) 200 m (sample C) away from discharge point (sample A) along the flow of the mining effluent using metal auger. Soil samples were transferred into labeled polythene bags and transported to Biochemistry laboratory, Abia State University, Uturu, stored in a refrigerator at 4°C while the control soil were collected about 7 km away from an unimpacted area devoid of mining activities.


Determination of trace metals in soil samples

Trace elements were determined by the perchloric acid digestion method described in APHA (1998). Exactly 1.0 g of air dried soil sample was weighed into a digestion tube and 3 ml of concentrated HNO3 was added. This was digested on electrically heated block for 1 h at 145°C. Then 4 ml of HCLO4 was added and heated to 240°C for further 1 h, cooled and filtered through whatman #42 filter paper and made to 50 ml volume. The filtrate was analyzed for heavy metals using atomic absorption spectrophotometer (AAS) (Tables 1 to 3).





Determination of trace metals in plant samples

Trace metal content of plant roots and shoots were determined by Atomic Absorption Spectrophotometer as described by (James, 1995). Following the ashing of samples, the resulting ash was dissolved in 10 ml of Hydrochloric Acid (HCL). It was filtered with Whatman #42 filter paper. The extract was used for the analysis using atomic absorption spectrophotometer (AAS) (Tables 4 to 15).














Statistical analysis

Data collected were subjected to statistical analysis using one way analysis of variance (ANOVA) and t-test statistic. Values are mean of triplicate determination ± standard deviation. The mean of the samples were compared to the control using ANOVA while mean of the two seasons were compared using student t-test. The individual mean difference was ascertained using Least Significant Difference (LSD) as described by Onuh and Igwemma, (2000). The student package for social sciences (SPSS) version 20 computer software was used for the analysis.


Trace metals can enter the food chain through a variety of sources. Elevated soil heavy metals have been reported to cause negative effects in soil such as reduction of soil microbial biomass level which are responsible for maintenance of soil fertility for optimum crop yield, affecting nitrogen- fixation and reduction in certain enzyme activities (Mathews et al., 2012). Soil trace metals content of mining effluent discharge soils as obtained from this study were significantly higher than the control. This may be attributed to mining activities in the area and indiscriminate discharge of mine water. The level of impaction decreased distance away from discharge points. Similar results have been reported by Akubugwo et al. (2013), Chinyere (2001), Nwaugo et al. (2004, 2009a, b, 2011), Onyeobi and Imeokparia (2014) and Smejkalova et al. (2003) that pollutants decrease distance away from discharge points or source of contamination. The high level of trace metals at the discharge points could be due to lower acidic pH at the discharge points as reported by Osuocha et al. (2015) as this has been shown to increase retention capacity and stabilization of trace metals in soils (Ogbonna et al., 2013). The results indicated that the sequence of impaction was A > B > C. This implicated site C as the least polluted site followed by site B and site A which could be attributed to distance of these sites from the source of contamination. Levels of soil trace metal obtained from the study in wet season were significantly lower compared to dry season. This could be due to leaching and runoff effects of rainfall that are capable of removing toxic metals from soil in wet season. Water evaporation from soil is more intense during dry season leading to soil solution being concentrated with little or no leaching of nutrient from the top soil. Similar findings have been reported by Syed et al. (2012) who assessed implication of seasonal variation in heavy metal contamination of agricultural soil. Findings from this work also agrees with Ideriah et al. (2013) who reported high level of trace metals in dry season in crude oil contaminated soils from Niger Delta, Nigeria. This high level of soil trace metals recorded from this study in dry season may be attributed to low acidic pH in the soil. Kabata-Pendis (2004) reported that low soil acidity is a stabilizing factor for toxic metals in soil and increases metal solubility in soil. Elevated level of metals in soil may render the soil unsuitable for plant growth and destroy biodiversity (Obute et al., 2010), leading to low productivity of ecosystem (Matthews et al., 2012). According to Jung, (2008) metals dispersed from mine waste are likely retained in the lower plains used for agricultural purposes. Observation from the present study showed that the impaction of the soil by trace metals decreased during the wet season and distance away from points of discharge in both seasons. This could be attributed to reduction in soil acidity and level of pollutants in soil. The correlation between soil physicochemical parameters reported by Osuocha et al. (2015) and the level of trace metals obtained from this study in wet and dry season is in line with this explanation. Munoz-Melendez et al. (2000) noted that heavy metal concentrations in soil solution are generally reduced at neutral or alkaline pH.

Metal accumulation and distribution in plant roots and shoots are influenced by plant species and inherent soil quality. This study generally showed that vegetables cultivated in the quarry effluent discharge soils had significantly higher metal concentrations in roots and shoots than their control counterparts. This could be attributed to high metal content in the quarry mining effluent discharge soil which was eventually taken up by these vegetables. This agrees with the findings of Oluyemi et al. (2008) who reported that plants grown on land polluted with industrial wastes can absorb high level of metals present in the soil solution through their root or through foliar absorption. Findings from the study showed that level of trace metals in roots and shoots of vegetables in dry season were generally higher compared to wet season. This could be attributed to increased amount of soil trace metals in dry season compared to wet season (Tables 1 to 3).

This also agrees with the findings of Ayari et al. (2010) that concentration of metals in plant is dependent on their concentration in soil. The relationship between toxic metals and soil pH has been reported to influence the absorbability of the element from the soil solution which consequently interfere with their translocation into plants parts (Liu et al., 2005). Low acidic pH as observed from the study in dry season could affect metal solubility in soil and hence increased phyto-availability of these metals in plants parts. Low acidic pH has been reported to influence the translocation of metals into plant tissues (Oluyemi et al., 2008; Sherene, 2012). This increase in phytoavailability of metals in low acidic pH has been reported to be due to the fact that protons have high affinity for negative charges present on colloids which come into competition with metal ions inducing ion exchange of metals ions in soil pore water (Tshibangu et al., 2014). The increase in metal concentration of vegetables in dry season could also be due to the fact that during dry season, dust particles generated due to blasting of rock are deposited on plants leaves which might get translocated into the plants system through foliar absorption and increase metal load of these vegetables. This process of foliar absorption may be more pronounced in dry season due to the persistence of these dust particles on plants leaves. This is however absent in wet season due to constant washing of the leaves by rainfall. Water evaporation from soil during dry season together with dehydration of plant leaves has been reported to increase metal concentration in plants root and leaves (Fatoki, 2000). Farm irrigation with metal contaminated water as observed from the study may also contribute to high metal concentration of these vegetables. This finding is in conformity with the reported of Sherene (2012) that farms irrigated with contaminated water are likely to absorb high level of metals. This study revealed that level of the studied trace metals in roots of these vegetables was higher than their level in shoots in wet and dry seasons (Tables 4 to 15). This demonstrate that the vegetables retained the studied metals in their roots but limits their mobility from roots to shoots once absorbed from the soil by the roots of the plants. This study in general showed that the vegetables grown in quarry mining sites accumulated high level of metals in plants parts than their counterparts in control sites. Similar findings were reported by Ebong et al. (2007, 2008) and Akubugwo et al. (2013) who undertook similar studies.


The study revealed that vegetables grown in mining effluent discharge soils accumulated high levels of trace metals compared to those from the control site. The level of accumulation was more in dry season than wet season. This indicates potential health risk associated with prolonged consumption of edible vegetables grown in these soils. Therefore planting of vegetables close to these mining sites should be discouraged.


The authors did not declare any conflict of interest.


Akubugwo EI, Osuocha KU, Nwaogu LA, Chinyere GC (2013). Studies on bioaccumulation of heavy metals and selected minerals from mining effluent contaminated soil treated with fertilizers into Cucurbita pepo vegetable. Advances in Appl. Sci. Res. 4(4):190-195.


Ayari F, Hamdi H, Jedidi N,Gharbi N, Kossai R (2010). Heavy metal distribution in soil and plant in municipal solid waste compost amended plots. Int. J. Environ. Sci. Technol. 7(3):465-472.


Chinyere GC (2001). Effect of effluents from cassava processing plants on soil cyanide levels. A case study of Okigwe in Imo State and Ovim Imenyi in Abia State, Nigeria J. Health Vision Sci. 3:88-92.


Duruibe JO, Ogwuegbu MOC, Egwurugwu JN (2007). Heavy metal pollution and human biotoxic effects. Int. J. Phys. Sci. 2(5):112-118.


Ebong GA, Akpan MM, Mkpenie VN (2008). Heavy metal contents of municipal and rural dumpsite soils and rate of accumulation by Carica papaya and Talinum triangulare in Uyo, Nigeria. E-J. Chem. 5(2):281-290.


Ebong GA, Etuk HS, Johnson AS (2007a). Heavy metals accumulation by Talinum triangulare grown on waste dumpsites in Uyo Metropolis, Akwa Ibom State, Nigeria. J. Appl. Sci. 7(10):1404-1409.


Fatoki OS (2000).Trace zinc and copper concentration in road side vegetation and surface soil: A measurement of local atmospheric pollution in Alice, South Africa. Int. J. Environ. Stud. 57: 501-513.


Ideriah TJK, Ikpe FN, Nwanjoku FN (2013). Distribution and speciation of heavy metals in crude oil contaminated soils from Niger Delta, Nigeria. World Environ. J. 3(1):18-28.


Jung MC (2008). Heavy metal contamination in soils and factors affecting metal uptake by plants in the vicinity of a Korean Cu-W mine, Sensors 8:2413-2423.


Kabata-Pendias A (2004). Soil-plant transfer of trace elements: an environmental issue. Geoderma 122:143-149.


Liu H, Probst A, Liao B (2005). Metal contamination of soils and crops affected by Chenzhou lead/zinc mine spill. Sci. Total Environ. 339:153-166.


Matthews A, Omono C, Kakulu S (2012). Impact of mining and agriculture on heavy metal levels in environment samples in Okehi Local Government Area of Kogi State. Int. J. Pure Appl. Sci. Technol. 12(2):66-77.


Monty K, Amiya KP (2012). Comparative Assessment of Microbial Biomass and Soil Enzyme Activities as Potential Indicators of Soil Quality in Different Mine Spoil, Odisha India. J. Environ 1(2): 64-74.


Munoz-Melendez G, Korre A, Parry SJ (2000). Influence of soil pH on the fractionation of Chromium, Copper and Zinc in solid phases from a landfill site. J. Environ. Pollut. 110:497-504.


Nwaugo VO,Onyeagba RA, Obinali M (2004). Effect of calcium carbid on soil nitrifying bacteria in Okigwe, Imo State. J. Appl. Sci. 7(5):4451-4458.


Nwaugo VO, Chima GN, Elekwa I, Inyang CU (2009a). Evaluation of surface water supply in Heavy metal mining area of Ishiagu, Southeastern Nigeria. J. Eng. Sci. Technol. 16(2):8187-8190.


Nwaugo VO, Chima GN, Elekwa I, Onwuchekwa IS (2009b). Comparative assessment of domestic water supply sources in Ishiagu, a heavy metal mining community in Ebonyi State, Nigeria. J. Appl. Sci. 12(2):8473-8486.


Nwaugo VO, Egbu AU, Odu NN, Ogbonna CE (2011). Impact of metal mining on domestic water quality in Ishiagu and its enivirons, Ebonyi State, Nigeria. ABSU J. Environ. Sci. Technol. 1(1):62-71.


Obasi NA, Akubugwo EI, Kalu KM, Ugbogu OC (2013). Speciation of heavy metals and phytoaccumulation potentials of selected plants on major dumpsites in Umuahia, Abia State, Nigeria. Int. J. Curr. Biochem. Res. 1(4):16-28.


Obute GC, Ndukwu BC, Eze E (2010). Changes in species diversity and physicochemical properties of plants in abandoned dumpsite in parts of PortHarcoult, Nigeria. Scientia Africana 9(1):181-193.


Ogbonna CE, Adinna EN, Ugbogu OC, Otitoju O (2013). Heavy metal concentration and Physicochemical properties of soil in the lead-zinc mining area of Ishiagu, Nigeria. J. Biodiver. Environ. Sci. 3(10):61-69.


Oluyemi EA, Feuyit G, Onekunle JAO, Ogunfowokan AO (2008). Seasonal variation in heavy metal concentration in soil and some selected crops at a landfill in Nigeria. Afr. J. Environ. Sci. Technol. 2(5):89-96.


Onuh MO, Igwemma AA (2000). Applied statistical techniques for business and basic sciences. Skill mark media Ltd, Owerri. P 176.


Onyeobi TUS, Imeokparia EG (2014). Heavy metal contamination and distribution in soils around Pb-Zn mines of Abakaliki District, South Eastern Nigeria. Frontiers in Geosciences 2(2):30-40.


Osuocha KU, Akubugwo EI, Chinyere GC, Ugbogu EA (2015). Seasonal impact on physicochemical characteristics and enzymatic activities of Ishiagu quarry mining effluent discharge soils. Int. J. Curr. Biochem. Res. 3(3):55-66.


Syed HF, Dilara K, Tanveer MA (2012). Assessment of heavy metal contamination of agricultural soil around Dhaka export processing zone, Bangladesh:Implication of seasonal variation and indices. J. Appl. Sci. 2:584-601.


Sherene T (2012). Mobility and transport of heavy metals in polluted soil environment. Int. J. Biol. Forum 2(2):112-121.


Tshibangu MI, Nsahlai VI, Kiatoko MH, Hornick JL (2014). Heavy metal concentration in Adenodolichos rhomboideus arms forage growing on mining tailings in south east of Democratic Republic of Congo: Influnce of washing, pH and soil concentration. Int. J. Curr. Res. Biosci. Plant Biol. 1(5):16-27.