ASSESSEMNT OF HEAVY METALS (PB, ZN, CD, & AS) CONCENTRATION IN LEAVES, STEMS, AND ROOTS OF SPINACH (AMARANTHACAE CAUDATUS) GROWN AROUND KUBANI RIVER, ZARIA

 

The quality of ecosystem becomes altered, when heavy metals find their way, somehow, into it through human and natural activities. These activities are one of the most pressing concerns of urbanization in developing countries like Nigeria, which result in the problem of solid, liquid and toxic waste management. Such waste may be toxic or radioactive (Onibokun and Kumuyi, 1996; UNDP, 2006). Such waste management problems include heaps of uncontrolled garbage, roadsides littered with refuse, streams blocked with rubbish, prevalence of automobile workshops and service stations, inappropriately disposed toxic waste and disposal sites that constitute a health hazard to residential areas (Adewole and Uchegbu, 2005; Rotich et al., 2006; Ebong et al., 2008). 

Soil is the most important component of the environment, but it is the most  undervalued, misused and abused one of the earth‟s resources (Gokulakrishnan and Balamurugan, 2010). Soil contamination has become a serious problem in all industrialized areas of the country. Soil is equally regarded as the ultimate sink for the pollutants discharged into the environment (Shokoohi et al., 2009). Most plants and animals depend on soil as a growth substrate for their sustained growth and development. In many instances the sustenance of life in the soil matrix is adversely affected by the presence of deleterious substances or contaminants. The entry of the organic and inorganic form of contaminants results from disposal of industrial effluents (Gowd et al., 2010). The source of the organic and inorganic elements of the soil of contaminated area was mainly from unmindful release of untreated effluent on the ground (Shetty and Rajkumar, 2009). The contamination of soils with heavy metals or micronutrients in phytotoxic concentrations generates adverse effects not only on plants but also poses risks to human health (Murugesan et al., 2008).

Environmental pollution was due to naturally occurring phenomenon such as volcanic eruption. Macro and trace elements play a significant role for maintain health in humans (Anon., 1996). However, non-essential trace elements like Pb, Cd, Cr and Ni, are non-biodegradable thus, persist everywhere in the environment. These metal elements have the ability to deposit in various body organs which poses a great threat to the human health (Singh et al., 2004; Chen et al., 2005). Agricultural Soils irrigated with waste water get severely contaminated with heavy metals. Crops grown on such soils can accumulate a significant amount of heavy metals in different issues (Khairiah et al., 2004; Chojnacha et al., 2005; Muchuweti et al., 2006).

Rapid industrialization and urbanization in the developing countries in the last decades have resulted in a significant increase in environmental pollution. The soils, the plants and the products made there of have been shown to be highly contaminated with heavy metals (Mazurek et al., 1995; Motylera & Sosmina, 1996; Hussain et al., 2003; Zahoor et al., 2003) and this concern has created a certain apprehension in the public regarding the safety of the food, they consume every day (Radwan & Salama, 2006).

Emission of heavy metals from the industries and vehicles may results in the deposition of such metals on the surface of the fruits and vegetables and contaminate (Geert et al., 1989; Ozores-Hampton et al., 1997; Jassir et al., 2005) by entering the food during industrial processing and packaging (Tsoumbaris & Tsoukali-Papadopoulou, 1994). Since, these heavy metals might seriously damage human health e.g. decrease in immunological defense, neurological disorders, intrauterine growth retardation, impair psycho-social behavior, disabilities associated with malnutrition and a high prevalence of upper gastrointestinal cancer (Arora et al., 2008) hence, regular survey and monitoring programs of heavy metal contamination in food stuff were mainly centered for decades in developed countries (Jorhem & Suinderstroem, 1993; Milacic & Kralj, 200; saracoglu et al., 2004) but no substantial research have been conducted to address this issue in the developing countries (Zahoor et al, 2003).

To ensure increase in productivity, different farming practices are usually adopted by farmers. One of such practices is the application of fertilizers and animal dung to the soils. Irrigation of the crops with all sorts of wastewater is another practice. There is the possibility of over application of such fertilizer or animal dung and wastewater. These may result in the accumulation of certain substances in soils and indeed the crops growing in such soils and may indeed affect the quality of the crops adversely (Anjana and Iqbal, 2006). These substances may have direct or indirect phytotoxic impacts on the corps leading to a decline in yields and threatening food. In addition, the plants may act as a vehicle for transferring these supplies substances into the food chain (Radojevic and Bashkin, 1999).

The use of polluted water in the immediate surroundings of big cities for growing of vegetables is a common practice in Nigeria. Although this water is considered a rich source of organic matter and plant nutrients, it also contains sufficient amounts of soluble salts and metals like Fe, Mn, Cu, Zn, Pb, Ni, Sn, Hg, Cr, As and Al. When such water is used for irrigation of crops for a long period, these heavy metals may accumulate in soil and may be toxic to the plants and also cause deterioration of soil. Various classes of vegetables are grown in many parts of Nigeria.

In Zaria, Kaduna State, North Central Region of Nigeria, Vegetables are heavy cultivated and consumed as food. In this area, vegetables are irrigated with dam water and all kinds of available wastewater. Similarly, to enhance the yield of these vegetables, and manures are occasionally added to the soil. There are therefore, the possibilities of over application of these fertilizers and manures. Hence, the uptake and storage of some heavy metal pollutants from these wastewater, fertilizers and manures by the vegetables are very likely since these heavy metals are soluble and mobile in ground water.

Zaria has abundant of vegetables which can be cultivated and exploited for this purpose. The determination of heavy metals in spinach (Amaranthuscaudatus) was carried out by analyzing spectrophotometrically the levels of the metals in the vegetables and soils samples.

The research work has the following aim and objectives;

The aim of the research is to determine the levels of heavy metals (Cd, Pb, As and Zn) in the soil, waste water and vegetable (spinach) grown around kubani river, zaria. With the following objectives: