Contamination and Possible Health Risks of Polycyclic Aromatic Hydrocarbons in Soil and Crops from Cultivated Floodplains of Some Rivers in Ekiti State, Southwest Nigeria

The demand for food in Nigeria has increased pressure on land use including floodplains despite possible contamination from the river catchments. The objective of this paper is to evaluate the contaminations and possible health risk of polycyclic aromatic hydrocarbons (PAHs) in soil from Irintan (Ogbese), Omi-Eye (Erio) and Egbigbu (Ayetoro) cultivated floodplains in Ekiti State, Nigeria using standard techniques. The soil samples were collected from 0-30cm depth at 5m, 25m and 45m perpendicular distances to the river course at lower, middle and upstream. The crop samples randomly collected on the floodplains were Talinum triangulare, Caspicum annum and Zea mays from each farm. Samples were appropriately treated and analyzed for polycyclic aromatic hydrocarbons and results used to estimate the possible health risk. PAHs concentration at each of the farm sites was found to be more than their corresponding controls.The ∑PAHs (µg/kg) in soil ranged 0.62-3.20, 0.38-2.33 and 0.09-1.75 at Irintan (Ogbese), Omi-Eye(Erio) and Egbigbu (Ayetoro) floodplains respectively and these values were categorized unpolluted. The ∑PAHs (µg/kg) was 1.24, 0.64 and 21.15 for T. triangulare, 2.62, 2.76 and 18.43 for C. annum and 0.70, 1.78 and 1.31 for Z. mays at Irintan, Omi-Eye and Egbigbu floodplain respectively. All the Benzo (a) pyrene equivalent concentration were less than the cancer screening value except in T. triangulare and C. annum at Egbigbu floodplain suggesting possible carcinogenic health concern in T. triangulare and C. annum at the floodplain. There could be a cause for concern for the consumption of these food crops by the exposed population

Biosorption of Cadmium (II) and Chromium (VI) from Aqueous Solution by Chemically Modified Tithonia Diversyfolia Biomass

Staff PublicationThe search for alternative and innovative treatment technologies for the effective removal of heavy metals from aqueous wastes has been a research of concerted effort due to the inherent limitations exhibited by the conventional methods such as less efficiency, sensitive operating conditions, energy requirements and generation of toxic sludge or other waste products. Biosorption, the passive uptake of heavy metals by biomaterials has been studied recently because of its high efficiency and cost effectiveness. Therefore, the biosorption capacity of Tithonia diversyfolia biomass chemically modified with sodium hydroxide for the removal of cadmium and chromium ions from aqueous solution was investigated. The effects of temperature, contact time, initial concentration of metal ions, adsorbent dosage and pH on the biosorption of Cd2+ and Cr6+ ions were assessed. Thermodynamic parameters such as free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) during the biosorption were evaluated. The results showed that the biosorption process of Cd2+ and Cr6+ by chemically modified Tithonia diversyfolia (CMTD) biomass was feasible and exothermic under the studied conditions. The equilibrium process was well described by the Langmuir isotherm model, with a maximum biosorption capacity of 46.75mg/g and 48.00mg/g for Cadmium and Chromium ions, respectively. Kinetic studies indicated that the biosorption of metal ions followed a pseudo-second order equation

Understanding Leaching Behaviour of Landfill Leachate in Benin-City, Edo State, Nigeria through Dumpsite Monitoring

Indiscriminate disposal of solid waste in unauthorized places has become an increasing problem for most cities in Nigeria, especially Benin-City, Edo state. Benin-City one of the largest city in Nigerian is experiencing the problem of solid waste management despite the best attempt of waste avoidance, reduction, reuse and recovery. Use of dumpsites is still the ultimate disposal method of domestic and industrial wastes in Benin-City. Three dumpsites in Benin-City and environs were selected randomly to evaluate their leachates characteristics. Leachate samples were collected from the dumpsites at three months interval and were assessed for their quality through physico-chemical and elemental examination using standard methods for examination of water and wastewater. Physico-chemical analysis result showed pH range of 6.76±0.08 –7.49±0.02, EC (55212.0±2028.43 – 64344.33±1131.22 μS/cm), Temperature (26.03±0.25 – 26.60±0.35OC), Cyanide (0.08±0.04 – 0.46±0.01 mg/L), Sulphide (12.30±1.21 – 14.90±2.26 mg/L), BOD5 (61.23±1.39 – 98.60±3.41mg/L), COD (92.11±2.14 – 140.00±4.19 mg/L), NO3-N 0.41±0.03 – 0.75±0.09 mg/L), NO2-N (0.09±0.01– 0.30±0.03mg/L), TOC (506.67±230.94 – 573.33±370.05 mg/L). Metals with consequential environmental significance determined in the leachate samples recorded concentration in mg/L as: Cd(0.02±0.01 – 0.240.31), Cr(0.04±0.00 – 0.06±0.01), Cu(0.49±0.07 - 0.61±0.05), Hg(0.03±0.01 – 0.06±0.01), Mn(0.27±0.07 - 0.38±0.03), Ni(0.05 ± 0.01- 0.07 ± 0.01), Pb(0.05±0.01 – 0.12±0.010) and Zn(0.37±0.04 - 0.65±0.03). The physiologic and metabolic roles of the elements detected in the leachate are discussed. The concentrations of the elements detected were below the toxicity limits recommended by Federal Environmental Protection Agency (FEPA) limits. On the overall, the physico-chemical and elemental characteristics of leachates obtained in this study revealed that the three waste dumpsites generated leachates that were not as contaminated as those reported in some other parts of the world