Accumulation of heavy metal pollutants in soil and cassava leaf and their effects on soil microbial population on roadsides in Ogbomoso, Nigeria

Acute toxicity of heavy metals is a rare phenomenon in nature but the intake of sub-­‐lethal doses over an extended period is of great concern. This research investigated the heavy metal concentrations in soil and cassava leaf and assessed the effects of the metals on microbial populations along Ogbomoso-­‐Oyo, high traffic density (HTD) (A) and Ogbomoso-­‐Ife Odan, low traffic density (LTD) (B) roads. The results show that the metals were statistically higher in concentration at A (Pb= 0.53, Cd= 0.57. Cr =0.19, and Zn= 4.67 mg/kg) than B (Pb= 0.36, Cd= 0.40, Cr= 0.12, and Zn= 2.70 mg/kg) road. The mean metal content of cassava leaf indicated that all the metals were higher in the leaf at high traffic density than at low traffic density road. Also, at A 20-­‐30 m recorded lowest heavy metal concentration in the leaf (except Zn = 3.87±0.35 mg/kg) than the distances closer to the road. The same trend was observed at B except that Zn was highest (2.90±0.20 mg/kg) at 10-­‐20 m than 0-­‐10 m and 20-­‐30 m from the road edge. The total microbial count was significantly higher at low traffic density (17.23 Cfug1(x105)) than high traffic density (11.58 Cfug1(x105)). Total microbial count and Total fungi count were found to be lowest at 20-­‐30 m away from the road compared with 0-­‐10 and 10-­‐20 m. The results of this research show that crop cultivation along the roads within 30 m from the roads constitutes a potential source of chronic heavy metal toxicity to the general populace who feed on the crops

Urban Gardening and Open Crown Trees: Insiduous Lethal Implications on Human and Animal Health

Urban agriculture is gradually gaining acceptability in most parts of the world. The act of urban gardening is food and vegetable production in urban setting. The environmental and social positive effects of open crown trees as well as vegetables of various varieties to urban dwellers cannot be trivialized. This is more importantly so considering the current threat of climate change to man and animals through microclimatic element reverses. The use to which these agricultural products so produced in urban areas are put is diverse. From their use as vegetables to their use as herbal products as well as to their use as chewing sticks. Urban arable crops are generally consumed whole while parts of open crown trees serve as chewing sticks and medicinal concoctions. Combined, vegetables and open crown trees regulate the amount of sunlight intensity that reaches man and animals residing in urban areas thereby regulating heat energy.In urbanization however, serious inherent danger is unconsciously being exposed to. Lethal bye –products are emitted through the use of both degradable and non-degradable materials. Since the ecosystem is a complex self-sustaining system, much of the lethal bye-products eventually find their ways back into living tissues via urban plants which are finally consumed by man and animals. In heavy traffic roads which are highly correlated with urban areas, the concentration of lead (Pb) for example which is a heavy metal and very lethal to man and animals ranges between 0.18 mg/kg and 0.38 mg/kg while the concentration of leaf acidity in polluted Azadirachta indica compared to unpolluted plant stands at a ratio of 1:10. Similarly, heavy metal concentration in soil and the population of microorganisms are generally inversely related. Whereas some microorganisms are needed for the crops well-being and for seed production, the alteration of environmental stability by heavy metals are rife.Conclusively, there is more work to be done in environmental microclimatic cleansing if urban gardening and open crown trees will serve the plus purpose for which they are preferred