Heavy Metal Uptake and Accumulation by Edible Leafy Vegetable (Amaranthus Hybridus L.) Grown on Urban Valley Bottom Soils in Southwestern Nigeria

Abstract

Heavy metals, such as cadmium (Cd), lead (Pb) and zinc (Zn), are important environmental pollutants, particularly in urban areas with high anthropogenic pressure. The uptake and accumulation of Cd, Pb and Zn in vegetables (Amaranthus hybridus L.) grown in the valley bottom soils of some cities in southwestern Nigeria were investigated. The concentration of heavy metals in vegetable leaves ranged from 0.4 to 2.0 for Pb (CV, 33), 0.38 to 1.20 for Cd (CV, 25) and 8.2 to 30.4 for Zn (CV, 33). In the vegetable stems, the concentration ranged from 0.8 to 2.6 for Pb (CV = 33), 0.6 to 2.5for Cd (CV, 22) and 11.4 to 18.9 for Zn (CV, 35). Concentration of metals in vegetable roots ranged from 2.2 to 5.1 for Pb (CV, 33), 1.4 to 4.9 for Cd (CV, 22) and 10.2 to 29.0 for Zn (CV, 35). Transfer factors (TF) were in the range of 0.22 and 3.00, with Cd having the highest TF of 3.00. Estimated intake vegetables in µg day −1 ranged from 72 to 82 for Cd, 69 to 120 for Pb and 105 to 200 for Zn. The intakes were above the recommended minimum risks levels. Potential risks, particularly for Cd and Pb intake, exceed the daily requirement for consumers of the leafy vegetable at all the sites. The apparent influence of anthropogenic inputs from the cities to these valleys was reflected by the higher concentrations than the reference location. Food quality assurance systems in vegetables grown in urban valley bottoms need to comply with the world standard on heavy metal concentration.

Bioaccumulation and associated dietary risks of Pb, Cd, and Zn in amaranth (Amaranthus cruentus) and jute mallow (Corchorus olitorius) grown on soil irrigated using polluted water from Asa River, Nigeria

“…This suggests that amaranth has relatively higher bioaccumulation capacity compared to jute mallow, which is consistent with the reports of Oluwatosin et al (2010).…”

“…Heavy metals such as Pb, Cd, and Zn can cause adverse human health impacts such as anemia, cardiovascular diseases, renal problem, and cancer (WHO 1996;Oluwatosin et al 2010). Humans are exposed to heavy metals through various pathways including dietary intake, inhalation, soil ingestion, and dermal contact (Islam et al 2007).…”

“…In this context, the presence of heavy metals in vegetables has received a significant research attention since vegetables are generally consumed in large quantities and have the ability to bioaccumulate heavy metals (Oluwatosin et al 2010). Furthermore, increased demand for vegetables in the urban and peri-urban areas of developing countries such as Nigeria has led to their cultivation in polluted soils and/or irrigation using polluted water sources (Fatoba et al 2012).…”

“…Humans are exposed to heavy metals through various pathways including dietary intake, inhalation, soil ingestion, and dermal contact (Islam et al 2007). Food consumption is considered to be a major source of heavy metals to human body (Oluwatosin et al 2010), and several studies have found that the concentration of heavy metals in food is high to an extent that they can pose a significant health risk to children and adults (Zheng et al 2007;Singh et al 2010;Gupta et al 2012).…”

Assessment of Heavy Metals Level in Soil and Vegetables Grown in Peri-Urban Farms around Osun State and the Associated Human Health Risk

“…Heavy metals accumulation in agricultural soil may not only result in contamination of soil but also in increased uptake by food crops which may affect its quality and safety (Muchuweti et al, 2006). Contamination of vegetables by heavy metals has recently received notable research attention because vegetables are consumed relatively in large amount and have the capacity to bioaccumulate heavy metals (Oluwatosin et al, 2010) consequently posing risk to human health. Quite a number of researches have been carried out on contamination of soil and vegetables by heavy metals (Liu et al, 2005;Mapanda et al, 2005;Rattan et al, 2005).…”