The slaughtering of animals and processing of meats for human consumption generates enormous wastes which are not properly managed in most developing nations including Nigeria. Majority of people in Akwa Ibom state in southern Nigeria depend on meat as their major source of protein, and abattoir wastes are applied in farms as organic manure by some farmers. This study examined the role of abattoir-related waste products in the physicochemical properties, total metal, and metal speciation of the soil. The data obtained were also subjected to some treatments using some environmental models to establish the degree of contamination by the parameters determined, studied locations, and the associated human health problems. Samples were collected from 5 designated abattoirs in Akwa Ibom state. Thirty composite samples were used for the research. Results obtained showed higher levels of pH, electrical conductivity, organic matter, and cation exchange capacity in the abattoir waste–impacted soils than in the control plot. Levels of pseudo total heavy metals were also higher in the studied soils than in the control plot. The mean values of the metals are below 400, 85, 140, 36, 100, and 35 mg/kg of recommended limits for Fe, Pb, Zn, Cu, Cr, and Ni, respectively by the Federal Environmental Protection Agency (FEPA) in Nigerian soil. The results also revealed that Fe and Cr existed mainly in residual fraction. However, Zn, Cu, and Ni existed principally in the form bound to organic matter/sulfide. In addition, we detected that Pb existed mainly in the reducible fraction. Disparities were also observed in the speciation results of the metals between the studied soils and the control plot. Principal component analysis (PCA) indentified that both the geogenic and anthropogenic factors contributed to the accumulation of metals determined in the studied soils. Variable relationships were also observed for the heavy metals determined in the studied soils. Fe showed a high-risk potential, and children were more vulnerable due to its toxicity. We conclude this study was able to expose the consequences of indiscriminate dumping of abattoir wastes on the quality of soil and the associated human health problems.

Total concentration, speciation, sources and potential health problems of Pb, Cd, Cu, Fe and Ni in a dumpsite soil within Calabar Municipality were evaluated in this work. The influence of organic matter and pH of the studied dumpsite soil on metal availability was also assessed. Results obtained indicated that; mean concentration of all the metals were higher in studied dumpsite soil than in the Control and higher than their recommended limits for Nigerian soil as well. Metal speciation revealed that, Pb and Fe existed mainly in the reducible form; Cd occurred in acid extractable fraction, Cu in oxidisable form while Ni existed primarily in inert (residual) fraction. Pb and Cu originated primarily from anthropogenic source whereas, natural source contributed mostly to the existence other metals in studied soil. All the environmental models utilized confirmed that, the studied dumpsite soil has been highly contaminated by these metals. Principal Component analysis identified impact of wastes and industrial/agricultural wastes as the two major factors affecting the studied soil. Cluster analysis recognized the parameters with similar chemical properties and common source. Metals assessed exhibited variable correlations among themselves, while soil organic matter and pH displayed both significant positive and negative influence on metal availability. Results obtained identified Pb as the element with high risk potential in the studied soil and children as the highly vulnerable class.

Biochar utilization for environmental remediation applications has become very popular. We investigated the trace metal levels and soil nutrient characteristics of a biochar–humus sediment slurry treatment of a simulated crude oil-contaminated soil in the present work. The results revealed that biochar prepared at moderate pyrolysis temperature (500 °C) could still retain a significantly higher nutrient content than those prepared at high temperatures (700 and 900 °C). Despite the suitability for soil treatment, one-pot treatment studies seem not to be very effective for monitoring trace metal sorption to biochar because trace metals do not biodegrade and remain in the system.

The first three spills of rainfall in 2016 were harvested from areas impacted by gas flaring and exhaust emissions namely: Ibeno, Eket, Onna, Mkpat Enin and Uyo local government areas south-south of Nigeria. Control samples were harvested from Ibiono Ibom local government area where anthropogenic source of air contaminants is negligible. These samples and Control were treated and analysed using standard procedures for their pH, electrical conductivity, turbidity, nitrate, total suspended solids, total dissolved solids, Fe, Zn, Cu, Pb, Cd and Ni levels. Mean concentrations of all parameters assessed in studied rainwater were higher than their corresponding levels in the Control revealing anthropogenic inputs of these properties in the ambient air. Mean concentration of all properties determined except those of pH, Fe, Pb, Cd and Ni were within their acceptable limits. Consequently, rainwater harvested from studied areas should be treated before consumption to avoid health implications associated with acidity, Fe, Pb, Cd and Ni. This study has also shown that, human activities executed within studied areas impacted negatively on the quality of rainwater harvested. All the parameters examined exhibited strong association and common source in ambient air except pH with strong negative correlation with all the properties.

Physicochemical properties, total metals and metal species were investigated in surface soil samples from six urban dumpsites within Akwa Ibom State, Nigeria. Results obtained indicated that Pb, Cd and Cr levels were higher in the dry season than in wet season, whereas Ni levels were higher during the wet season. Soil pH, organic matter and cation-exchange capacity (CEC) showed higher values in wet season than in dry season, whereas sand and clay levels were higher in the dry season. Speciation analysis showed the principal fraction of the metals to be Pb (reducible), Cd (acid extractable) and Ni (residual), whereas Cr existed in the residual fraction during the dry season and in the acid-extractable fraction during the wet season. Soil pH was positively correlated at pNi>Cd>Cr, whereas their bioavailability followed the trend Cd>Pb>Cr>Ni.

The intensive application of manures for the improvement of plant yield is a global practice by farmers notwithstanding the associated negative effects. The probability of health risk, bioaccumulation, and speciation of arsenic (As), cadmium (Cd), nickel (Ni), and lead (Pb) in soils and vegetables (Talinum triangulare and Telfairia occidentalis) impacted by untreated wastes from animal farms and inorganic fertilizers used as manures in the oil producing section of Nigeria were investigated. The total metal was determined using spectrophotometric methods while its geochemical fractions were identified following the modified Community Bureau of Reference (BCR) procedures of sequential extraction. The results obtained indicated the following mean concentrations (mg kg-1): 1.64 ± 0.70, 3.17 ± 1.47, 62.22 ± 8.83, and 187 ± 29.73 for As, Cd, Ni, and Pb, respectively. The results revealed that the mean concentrations of all the metals in the studied locations, except As, were above their recommended limits by the Food and Agricultural Organization/World Health Organization (FAO/WHO). The mean values of As and Pb in T. triangulareand T. occidentalis were also above the acceptable limits. Relatively higher levels of the metals were recorded at the studied locations as compared to the control site. The transfer factors of metals determined were generally lower than one; hence, the human exposure rate to these metals may not be high. The sequential extractions of metal indicated that As and Pb existed in the reducible fraction, Cd in the acid extractable fraction, and Ni in the residual fraction. The contamination factor of the metals revealed that As and Ni belong to the low contamination class, while Cd and Pb fall within the very high contamination category. The study showed that all the studied locations were heavily contaminated, with Uyo being the most polluted site. The principal component analysis identified anthropogenic factor as the main contributor to the presence of these metals in the investigated area. Daily intake rates for these metals via vegetable consumption by both the elderly and young populations were generally lower than their recommended oral reference doses. The non-carcinogenic risks obtained for both populations were less than one. However, the consumers of T. triangulare and T. occidentalis from the studied locations were exposed to Pb toxicity, with children being more vulnerable. This study has shown that the application of untreated animal wastes and inorganic fertilizers as manures has the potential to affect human health, bioavailability of metals, and the geochemical fractions of metals in soil over time.