Equatorial M(3000)F2 estimation of F2-layer models peak heights during high solar activity

The validation of M(3000)F2 estimation of hmF2 based on four different formulatedmodels viz: (1). Shimazaki1, (2). Bradley and Dudeney2, (3).Dudeney3 and (4). Bilitza etal.4 at an Equatorial station in West Africa during high solaractivity period (1991) are carried to ensure its conformity with observed and InternationalReference Ionosphere (IRI) model. Fifteen (15) days local time data during the solsticesmonths (January and July) and equinoxes months (April and October) are selectedand analyzed. The results obtained show that the M(3000)F2 estimation of hmF2from the ionosonde-measured values using the Ionospheric Prediction Service(IPS-42) sounder compared to the observed values which were deduced using an algorithm from scaled virtual heightsof quiet day ionograms are highly correlated with Bilitza model. International ReferenceIonosphere (IRI-2012) model5 for the Equatorial region also agreeswith the formulation developed by Bilitza etal4 for the four different seasons of the year. hmF2 is highest (548 km) insummer (June solstice) season and lowest (471 km) in autumn (April equinox)season with daytimes peaks occurring at 1300LT during the solstices and at 1000 LTduring the equinoxes respectively. Also, the post-sunset peaks are highest (596km) at the winter season (Decembersolstice) and lowest (556 km) at the autumn season (October equinox)both occurring between 1800 – 2100 LT

Heavy metal contamination of selected mining fields in North-Central Nigeria

This study evaluates the causes, concentration and the associated health risks of selected heavy metals (HMs) in soil samples collected from beryllium and gold mining fields in Nigeria. The samples of soil were collected manually and analysed by means of Atomic Absorption Spec- trophotometry (AAS). Seventy-two (72) samples were analysed which presented varying degrees of concentration of the selected HMs. The analysed HMs are Chromium (Cr), Arsenic (As), Iron (Fe), Cadmium (Cd), Nickel (Ni), Manganese (Mn), Magnesium (Mg), Zinc (Zn), Copper (Cu) and Lead (Pb). Deterministic and stochastic approaches were explore to examine the human health risks. The evaluated Hazard Indices (HI) for the investigated mining locations are < 1, the rec- ommended threshold provided by United State Environmental Protection Agency (USEPA) for acceptable non-cancer risk. The estimated cancer risk levels for the mining locations exceeds the acceptable range of 1.00E-6 and 1.00E-4

Potentially toxic metals in irrigation water, soil, and vegetables and their health risks using Monte Carlo models

Food safety has become a serious global concern because of the accumulation of potentially toxic metals (PTMs) in crops cultivated on contaminated agricultural soils. Amongst these toxic elements, arsenic (As), cadmium (Cd), chromium (Cr), and lead (Pb) receive worldwide attention because of their ability to cause deleterious health effects. Thus, an assessment of these toxic metals in the soils, irrigation waters, and the most widely consumed vegetables in Nigeria; Spinach (Amaranthushybridus), and Cabbage (Brassica oleracea) was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The mean concentration (measured in mg kg− 1) of the PTMs in the soils was in the sequence Cr (81.77) > Pb(19.91) > As(13.23) > Cd(3.25), exceeding the WHO recommended values in all cases. This contamination was corroborated by the pollution evaluation indices. The concentrations (measured in mg l− 1) of the PTMs in the irrigation water followed a similar pattern i.e. Cr(1.87) > Pb(1.65) > As(0.85) > Cd(0.20). All the PTMs being studied, were found in the vegetables with Cr (5.37 and 5.88) having the highest concentration, followed by Pb (3.57 and 4.33), and As (1.09 and 1.67), while Cd (0.48 and 1.04) had the lowest concentration (all measured in mg kg− 1) for cabbage and spinach, respectively. The concentration of the toxic metals was higher in spinach than in cabbage, which may be due to the redistribution of the greater proportion of the metals above the ground tissue, caused by the bioavailability of metals in the aqueous phase. Expectedly, the hazard index (HI),and carcinogenic risk values of spinach were higher than that of cabbage. This implies that spinach poses potentially higher health risks. Similarly, the Monte Carlo simulation results reveal that the 5th percentile, 95th percentile, and 50th percentile of the cumulative probability of cancer risks due to the consumption of these vegetables exceeds the acceptable range of 1.00E−6 and 1.00E−4. Thus, the probable risk of a cancerous effect is high, and necessary remedial actions are recommended