Abstract
Background.Consumption of plants such as Carica papaya grown around automobile workshops is common in big cities in Nigeria. However, little is known about the heavy metals contamination of these consumables due to the influence of automobile emissions during maintenance activities.Objectives.This study aimed to assess heavy metal concentrations in C. papaya and supporting soils around automobile workshops in Port Harcourt Metropolis, Rivers State, Nigeria.Methods.Seven automobile workshops were used for the present study. First, 20 m × 20 m quadrats were laid out for soil and C. papaya tissue sampling. One composite soil sample was collected from the topsoil (0–15 cm depth) around each of the automobile workshops. Three C. papaya stands at least 30 cm apart around each workshop were used for the study and from these stands, tissues (root, stem, leaf, fruit) of C. papaya were collected. Standard laboratory techniques were used to determine the pH, electrical conductivity (EC) and heavy metals (lead (Pb), mercury (Hg), cadmium (Cd), copper (Cu), and zinc (Zn)) in the soil samples and C. papaya tissues. Pairwise t-test was used to determine significant differences (p<0.05) in the heavy metal concentrations in soil and C. papaya tissues between the sample and control sites, while correlation statistics were used to determine the relationship of heavy metal concentrations between soil and C. papaya tissues.Results.C. papaya tissues and supporting soil had significantly higher levels of pH, EC and heavy metals in the sampled plots than the control plot. The heavy metal concentrations in C. papaya and soil occurred in the decreasing order of Pb>Cu>Hg>Zn>Cd. The fruit of C. papaya had the highest mean concentrations of Pb (51.4±14.1 mg/kg) and Zn (26.4±1.9 mg/kg), while the leaf had the highest mean concentration of Hg (32.0±2.3 mg/kg). The pH, Cu and Zn in the supporting soil were significantly correlated with the levels in the C. papaya tissues.Conclusion.Bio-accumulation of heavy metals by C. papaya is evident around automobile workshops, and Pb, Hg, Cd concentrations were found to be above the permissible limits for human consumption according to World Health Organization (WHO) standards. Consumption of food materials grown around automobile workshops could pose health risks.
Highlights
Automobile workshops are sources of auto wastes in cities and pose environmental hazards in developing countries
Effects of automobile workshops on heavy metals uptake in Carica papaya tissues Findings revealed that pH ranged between 5.0 and 6.1 in the root of C. papaya with mean pH of 5.67 around automobile workshops, while in the control site, pH ranged between 7.8 and 8.3 with a mean pH of 8.09
Bio-absorption of heavy metals (Pb, Cu, Hg, Cd, Zn) by the tissues of C. papaya is evident around mechanic workshops in Port Harcourt Metropolis, and their uptake is directly linked to the supporting soil
Summary
Automobile workshops are sources of auto wastes in cities and pose environmental hazards in developing countries. Auto wastes include used oil and fluids, dirty shop rags, waste from solvents used for cleaning parts, metallic particles from machinery wear, used batteries, asbestos from brake pads, oxidation products, and organic and inorganic chemicals used in oil additives and metals.[1,2] The release of automobile wastes is responsible for the accumulation of heavy metals in soils and vegetation around the automobile workshops.[3] Automobile workshops accumulate heavy metals concentrations in soil, creating environmental and health hazards.[4] The soils in the tropics are capable of supporting complete food production and modifying carbon cycling, but soil pollution from automobile waste has devastated the soil.[5] Automobiles in Nigeria mainly use petrol and the smoke releases Consumption of plants such as Carica papaya grown around automobile workshops is common in big cities in Nigeria. Accepted June 1, 2017 J Health Pollution 14: 48-61 (2017)
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