Concentrations, source identification and human health risk of heavy metals in the road dust collected from busy junctions in Osogbo Southwest, Nigeria

The study determined the concentrations of heavy metals in the road dust samples collected in some selected busy traffic junction in Osogbo, southwest, Nigeria. This was to identifying the sources of heavy as well as the evaluating the associated human health risks. The concentrations of Pb, Cu, Cd, Ni, Co, Cr, Zn, Mn, and Fe were determined by employing Atomic Absorption Spectrophotometer. The sources were identified using non-negative constraint Positive Matrix Factorization receptor model and the health implication were assessed using risk indices consist of average daily doses via: dermal, inhalation and ingestion; Hazard Quotient (HQ); hazard index (HI); and lifetime average daily dose (LADD). The total average concentrations of Fe, Mn, Cu, Zn, Cr, Cd, Pb, Ni, and Co were 5030.0, 80.52, 15.14, 49.0, 6.81, 2.80, 1.77, 1.31, 1.98 µg/g, respectively and they were few order higher than their values in the local background site. The inhalation appeared to be the major exposure pathway of heavy metals in the road dust to the adults and children followed by dermal contact and ingestion. The sequences of HQ values are Cd < Ni < Zn < C u < Pb < Cr and Cu < Cd < Pb < Cr < Ni < Zn for adults and children. The HI values for the adults and children are 0.2 and 0.5, showing that any of Cu, Zn, Cr, Cd, Pb and Ni will unlikely cause negative human health effect through multiple exposure routes. The cumulative value of LADD for Cu, Zn, Cr, Cd, Pb and Ni is 1.70 x 10−5 which falls within the acceptable limit value of 10−4 to 10−6. The four main sources resolved by PMF and their relative contributions were vehicular components wear (36 %), fuel and lubricating oil (30 %), tyre particles wear (23 %), and battery corrosion and leakage (11 %)

Sources and Sectoral Trend Analysis of CO2 Emissions Data in Nigeria Using a Modified Mann-Kendall and Change Point Detection Approaches

In Nigeria, the high dependence on fossil fuels for energy generation and utilization in various sectors of the economy has resulted in the emission of a large quantity of carbon dioxide (CO2), which is one of the criteria gaseous pollutants that is frequently encountered in the environment. The high quantity of CO2 has adverse implications on human health and serious damaging effects on the environment. In this study, multi-decade (1971–2014) CO2-emissions data for Nigeria were obtained from the World Development Indicator (WDI). The data were disaggregated into various emission sources: gaseous fuel consumption (GFC), liquid fuel consumption (LFC), solid fuel consumption (SFC), transport (TRA), electricity and heat production (EHP), residential buildings and commercial and public services (RSCPS), manufacturing industries and construction (MINC), and other sectors excluding residential buildings and commercial and public services (OSEC). The analysis was conducted for a sectorial trend using a rank-based non-parametric modified Mann–Kendall (MK) statistical approach and a change point detection method. The results showed that the CO2 emissions from TRA were significantly high, followed by LFC. The GFC, LFC, EHP, and OSEC had a positive Sen’s slope, while SFC, TRA, and MINC had a negative Sen’s slope. The trend analysis indicated multiple changes for TRA and OSEC, while other sources had a change point at a particular year. These results are useful for knowledge of CO2-emission sources in Nigeria and for future understanding of the trend of its emission for proper environmental planning. The severe effects of CO2 on the atmospheric environment of Nigeria may be worsened in the future due to some major sources such as transportation services and electricity generation that are inevitable for enviable standard of living in an urban setting

Contamination and Source Identification of the Elemental Contents of Soil Samples from Municipal and Medical Waste Dumpsites in Ile-Ife, Nigeria

Contamination in soil samples collected from municipal and medical waste sites was assessed by employing four indices: contamination factor (Cf ), degree of contamination (Cdeg), pollution load index (PLI), and index of geoaccumulation (Igeo).  The sources of soil contaminants were identified by using Positive Matrix Factorization (PMF). Iron had the highest average concentrations of 46.47 ± 14.03 and 39.42 ± 2.54 µg/g in the municipal and medical waste dumpsites. Cf values were above 6 for both dumpsites, classifying the dumpsite soil as very high contamination with respect to Cr, Fe, Ni, Cu, Zn, As, Cd, and Pb. The overall Cdeg and PLI values are 176.9 and 170.4 and > 5 for both dumpsite implying very high degrees of contamination and progressive deterioration, respectively. The average Igeo values for Zn, Cd, and Pb of the two dumpsites were >3, indicating that the soil samples at both study areas were classified as highly to moderately polluted. The three identified sources resolved by PMF and their respective percentage contributions were crustal (32 %), scrap metals wastes (40 %), and electronic wastes (28 %)