Assessment Of The Environmental And Health Impactof Peri-Urban Vegetable Farming In Selected Areas Of Osun State, Nigeria
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Date
2017
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Abstract
This study identified various sources of water used for irrigation in selected peri-urban farms and assessed the agronomic practices associated with peri-urban farming in selected areas of Osun State, Nigeria. It also investigated chemical properties of the soil,heavy metals in soil and vegetable samples collected from the study areas as well as the soil pollution load. These were with a view to providing information on the potential health risk associated with human consumption of peri-urban vegetables.
Fifteen peri-urban farmers were purposively selectedwithin seven cities in Osun State and structured questionnaire administered through face-to-face interview. Additional information gathered during the field survey included farming practices adopted by the selected farmers and sources of farm input. Soil (30) and vegetable (60) samples were also collected from the selected peri-urban farms between January-April (a dry weather season, when irrigation was at its peak). A control experiment was set up at the greenhouse of Faculty of Agriculture, ObafemiAwolowo University, Ile-Ife. Chemical parameters (pH, Organic Carbon, Organic Matter and NO3-) and heavy metals (As, Cd, Cu, Pb, Zn) concentrations in the soil and edible portions of vegetables (Amaranthushybridus and Corchorusolitorius) were quantitatively determined using standard methods. Appropriate descriptive and inferential statistical methods were adopted for data analyses.
The results showed that 67% of the farmers irrigated their farms with nearby streams, 7% with shallow well, 13% with river tributaries and 13% with waste water. About 93% of the farmers carried out weeding by hand pulling while 7% applied herbicides. Sixty percent of the farmers maintained soil fertility by applying inorganic fertilizer, 13% applied both poultry manure and inorganic fertilizers while the remaining 27% depended on nature fertility.Nitrate ion concentration in soil and vegetable samples varied between 20.45-240.52 mg/kg and 214.15-1204.52 mg/kg respectively. Concentration of heavy metals in the soils ranged: 0.18-0.63, 2.40-56.17, 0.70-36.75 and 30-300 mg/kg for Cd, Cu, Pb and Zn, respectively. Heavy metals concentration in vegetable samples varied between 0.10-0.83, 0.85-10.45, 0.06-11.55 and 14.12-11.55 mg/kg for Cd, Cu, Pb and Zn, respectively. The pollution load indexfor Cd, Cu, Pb and Zn ranged: 1.51-5.25, 0.86-11.34, 0.15-8.02 and 0.44-6.49, respectively. The transfer factor of Cd, Cu, Pb and Zn ranged: 0.07-4.44, 0.06-0.41, 0.07-4.28 and 0.31-4.08 mg/kg, respectively for A.hybridus, and 0.11-2.11, 0.06-2.27, 0.06-3.86 and 0.13-2.63 mg/kg, respectively for C.olitorius. The estimated daily intake of Cd, Cu,Pb and Zn from consumption of A.hybridusranged between 0.0003-0.001, 0.00021-0.016, 0.002-0.014 and 0.053-0.159 mg/kg/day, respectively and 0.0002-0.0016, 0.004-0.016, 0.0017-0.0076 and 0.023-0.144 mg/kg/day, respectively for consumption of C. olitorius. Health risk index for Cd, Cu,Pb and Zn from consumption of A. hybridus ranged between 0.30-1.20, 0.03-0.38, 0.10-4.75 and 0.18-0.86, respectively and 0.20-0.90, 0.10-0.43, 0.35-1.68 and 0.08-0.48, respectively for consumption of C.olitorius.
The study concluded that vegetables from selected peri-urban farms werenot safe for consumption and might pose possible health hazard to humans due to the high heavy metals content.
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Keywords
water, agronomic, Osun State, Nigeria, farmers