Operational speciation of lead, cadmium, and zinc in farmlands around a lead polluted goldmine in northern Nigeria

This study was undertaken to evaluate the geochemical fractions and risk potential of lead (Pb), cadmium (Cd) and zinc (Zn) in farmlands around a polluted goldmine in Dareta, northern Nigeria. The total heavy metal concentrations were obtained  through a mixed acid digestion. A modified sequential extraction procedure was  used in separating the total metal concentrations into five operationally defined  fractions. The results showed extremely high concentrations of total Pb (26 – 2,247 mg kg-1), and Cd (2 - 69 mg kg-1) in the soils. The fractionation results also showed very high concentrations of Pb and Cd held on the easily mobilized fractions.  However, in terms of proportions, the bulk of the metal concentrations were   partitioned to the residual fraction while the exchangeable fraction held the least.   The concentrations of Zn recorded were below the thresholds employed. Lead and   Cd, showed strong enrichment, with both elements recording enrichment factors of   32.8 and 83.0, and I-geo factors of 4.4 and 5.8, respectively. Although the bulk of  the metals were partitioned to the residual fractions, the concentration of metals   held onto the easily mobilized fractions such as the exchange, oxide and organically bound fractions may make the metals bioavailable on the long run with possible   pollution risk on this soil, especially when used for agricultural purposes.Keywords: Heavy metal contamination, Metal fractionation, Pollution inde

Phosphate-induced cadmium adsorption in a tropical savannah soil

The influence of phosphate (P) on cadmium (Cd) adsorption was examined in a savanna soil with long history of different fertilizer amendment. The soil was incubated with P at 0, 250 and 500 mg P kg-1 soil and left to equilibrate for 2 weeks. Cd was added to the P-incubated soil at concentrations ranging from 27, 49 and 83 mg Cd kg soil. Addition of phosphate as KH2PO4 increased Cd adsorption by the soil. The amount of Cd adsorbed at 250 mg P kg-1 treatment was more than the amount of Cd adsorbed at 500 mg P kg-1 at low equilibrium Cd concentration. The sorption maxima and the distribution coefficient also increased; but the distribution coefficient and binding energy at 250 mg P kg-1 were higher than those at 500 mg P kg-1. Fitting the experimental data to adsorption, isotherm indicated a shift from the L-curve to the H-curve isotherm with P-amendment indicating a possible precipitation of Cd-P compounds. The Langmuir sorption maxima increased from 61 to 99.3 with P addition while the distribution coefficient also increased from 13.9 to 29.4. Our results indicated that Cd in the presence of phosphate can act as a bridging element between phosphate and organic matter.Keywords: Cadmium, adsorption isotherms, phosphate.African Journal of Biotechnology Vol. 12(24), pp. 3822-382

Heavy Metals Source Apportionment and Human Health Risk Assessment of Contaminated Soils of Zamfara State, Nigeria

Progressive illegal artisanal mining activities threaten public health without functional law enforcement on pollution control and proper management practices. This is not an exception of Zamfara State, Nigeria, where a large portion of the populace participates in artisanal mining. The study was conducted to assess the level of health risk associated with heavy metals contaminated soils of Zamfara state, Nigeria. Soil samples were collected from five mining locations (Abare, Bagega, Dareta, Sunke, and Tungar Kudaku) and Anka-town (control site) with no record of mining activities. In each place, bulked soil samples were collected from three sites (mining site, processing site, and village), and the concentration of six heavy metals (Fe, Pb, Cd, Cr, Zn, and Ni) in all the samples were analyzed. The result of the principal component analysis and correlation analysis revealed that Pb, Zn, Cr, and Ni originated from the same source, i.e., anthropogenic/mining activities. While Fe and Cd originated from the geogenic processes because of their high abundance in the soil of the study area, as Anka-town (control site) also recorded high concentrations of Fe and Cd. Health risk assessments were carried out in two groups of population (adult and children) through three exposure pathways (i.e., ingestion, dermal contact, and inhalation). The results showed that ingestion dominated dermal contact and inhalation pathways, and Fe is the riskiest metal while Cd and Ni have the lowest risk of exposure for daily intakes. The non-cancer hazard quotient (HQ) values were all recorded below 1. For the total hazard index (THI), all the adult's exposure pathways were negligible, while for children, only Bagega has ingestion of heavy metals exceeding one (1.10), indicating that non-cancer health risks for children exist. The other four mining locations, Abare, Sunke, Tunga, and Dareta, have values approaching one (i.e., 0.71, 0.60, 0.50, and 0.74, respectively). While for Anka town, which is the control site, it has a value far less than one (0.16). These indicate that all the study locations have the potential for children's health risk through ingesting food produced from contaminated soils. Therefore, there is an urgent need to apply remediation measures immediately to combat complications raised due to heavy metal contaminations

Pedogeochemical assessment of wetland soils in Hadejia- Jama’are river basin in the Nigerian Sahel savanna

Understanding the pedo-geochemical assessment of wetland soils in the Hadejia/Jama`are river basin in the Sahel savannah of Nigeria is paramount for efficiently planning the long-term sustainable use of the wetlands and is paramount for reliably estimating soil contamination. Namely, five (5) different wetland sites were selected; Masama 1 and 2, Sinamu 1 and 2, and Tandanu while one from the Drylands of Tandanu. A pit was excavated to a depth of 1.5 m at each site, except where there is an elevated water table or impenetrable stratum, and soil samples were collected from three identifiable horizons (Bt2, Bt1, and Ap, respectively). The results of principal component and cluster analysis showed that total and labile Pb, total Zn, and labile Cr were considered the most influential heavy elements for identifying pedogenic and sedimentological processes in the wetlands of the study area. It also showed that Pb, Zn, and Cr came from the same source in all soils examined. Therefore, we concluded that the soils in all the wetlands studied are at high risk of toxic effects from Pb and Zn contamination. It is strongly recommended that heavy metals be decontaminated at all surveyed sites before further use for agricultural purposes

Prevalence and Determinants of Endothelial Dysfunction among Adults Living with HIV in Northwest Nigeria

Background: Endothelial dysfunction constitutes an early pathophysiological event in atherogenesis and cardiovascular disease. This study aimed to assess the prevalence, determinants, and degree of endothelial dysfunction in antiretroviral therapy (ART)–treated people living with HIV (PLWH) in northwestern Nigeria using brachial flow-mediated dilatation (FMD). Methods: This was a comparative, cross-sectional study. A total of 200 ART-treated adults living with HIV with no evidence of kidney disease were compared with 200 HIV-negative participants attending a tertiary hospital in Kano, Nigeria, between September 2020 and May 2021. Endothelial function was evaluated by measuring FMD with a high-resolution vascular ultrasound transducer. FMD was calculated as the ratio of the brachial artery diameter after reactive hyperemia to baseline diameter and expressed as a percentage of change. Blood and urine samples were obtained from participants in both arms. Urine albumin-to-creatinine ratio (uACR) was calculated using the 2021 CKD-EPI estimated glomerular filtration rate (eGFR) creatinine-cystatin C equation without the race variable, and low-density lipoprotein (LDL) cholesterol was measured using enzymatic method. Results: The overall mean age (± standard deviation) of the study participants was 42 ± 11 years. Participants in the comparison arm were younger than PLWH (38 ± 11 versus 46 ± 10 years, respectively). The median (interquartile range) uACR was 41.6 (23.2–162.9) mg/g for the ART-treated PLWH versus 14.5 (7.4–27.0) mg/g for healthy controls. PLWH had a significantly lower mean percent FMD when compared to HIV-negative participants (9.8% ± 5.4 versus 12.1% ± 9.2, respectively). Reduced FMD was independently associated with HIV infection (β = –2.83%, 95% CI, –4.44% to –1.21%, p = 0.001), estimated glomerular filtration rate (β = –0.04%, 95% CI, –0.07% to –0.01%, p = 0.004) and LDL cholesterol (β = –1.12%, 95% CI, –2.13% to –0.11%, p = 0.029). Conclusion: HIV-positive status, lower estimated GFR, and higher LDL cholesterol levels were independently associated with endothelial dysfunction. Future prospective studies with larger cohorts of persons living with HIV (and age- and sex-matched HIV-negative controls) are needed to gain further insight into these important findings. In the interim, aggressive management of modifiable risk factors is warranted

Adsorption-solubility equilibria and speciation of Pb, Cd, and Zn in a savanna soil

Emission of contaminants into the environment is a common feature of industrialization. The danger of these substances has generated interest in their solubility and speciation. In this study, the nature of adsorption, solubility and speciation of Pb, Cd and Zn under high levels of accumulation were evaluated through a model sorption-solubility experiment. Equilibrium concentrations of metals and other soil characteristics were used as input parameters in a metal speciation model. The solubility controls of metal activities were evaluated through the use of activity/stability diagrams. The solubility of Pb, Cd and Zn was enhanced between pH 4.8 and 6.6. Increased solubility at this pH range indicates higher bioavailability and toxicity. Speciation results showed a predominance of free metal species in the soil solution. The activity diagrams used to test the stability of possible mineral bearing compounds in the soils did not show any particular solid phase as possible control of the activities of Pb, Cd and Zn in solution. This suggests that solubility controls might be due to the formation of metastable minerals which are not well crystallized.A emissão para o ambiente de contaminantes é uma caraterística comum da industrialização. O perigo deste tipo de substâncias tem vindo a despertar interesse no que se refere à sua solubilidade e especiação. Neste estudo avaliou-se num ensaio recorrendo a um modelo sorção-solubilidade, a natureza da adsorção, solubilidade e especiação do Pb, Cd e Zn em condições de elevada acumulação. No modelo de especiação de metais utilizaram-se como parâmetros de entrada as concentrações de equilíbrio dos metais bem como outras carateristícas do solo. O controlo da solubilidade das atividades dos metais foram avaliadas recorrendo ao uso de diagramas atividade/estabilidade. A solubilidade do Pb, Cd e Zn aumentou para valores de pH entre 4,8 e 6,6. O aumento da solubilidade nesta gama de pH é indicativo de maior biodisponibilidade e toxicidade. Os resultados da especiação revelaram uma predominância de espécies de metais na forma livre na solução do solo. Os diagramas de atividade usados para testar a estabilidade de possíveis compostos minerais perigosos no solo não revelaram nenhuma fase sólida em particular suscetível de controlar as atividades do Pb, Cd e Zn em solução. Este facto sugere que o controlo da solubidade deve ser devida a minerais metastizados que não ese encontram ainda perfeitamente cristalizados.La emisión de contaminantes al medio ambiente es una práctica común como consecuencia del proceso de industrialización. El peligro que estas sustancias genera ha despertado el interés por el estudio de su solubilidad y especiación. En este trabajo se evalúa la naturaleza de la adsorción, solubilidad y especiación de Pb, Cd y Zn en condiciones de elevada acumulación a través de un modelo de sorción-solubilidad. Como parámetros de entrada del modelo se utilizaron las concentraciones en equilibrio de los metales y otras características del suelo. Los controles de solubilidad de las actividades de los metales se evaluaron mediante diagramas de actividad/estabilidad. Las solubilidades de Pb, Cd y Zn se potenciaron a pH entre 4,8 y 6,6. El incremento de la solubilidad dentro de este rango de pH indica una mayor biodisponibilidad y toxicidad. Los resultados de la especiación mostraron un predominio de las especies metálicas libres en la solución del suelo. Los diagramas de actividad utilizados para evaluar la estabilidad de posibles compuestos minerales en los suelos no mostraron ninguna fase sólida en particular como posible control de las actividades de Pb, Cd y Zn en solución. Esto sugiere que su solubilidad podría estar controlada por la formación de minerales metaestables mal cristalizados

KINETICS AND THERMODYNAMICS OF NITRATE ADSORPTION BY BIOCHAR

High concentration of nitrate in surface and ground water is a universal water pollution challenge for several. Four biochar samples were produced and subjected to batch sorption experiment. Data obtained were fitted into the linear forms of four adsorption isotherm and kinetics models. Least square regression analysis was used to test the best fitting isotherm and kinetic model using the coefficient of determination (R2). Results revealed that only maize cob biochar (MCB) and poultry litter biochar (PLB) had the ability to adsorb nitrate with maximum quantities of adsorbed nitrate (73.915 and 133.887 mgg-1). Similarly, adsorption kinetics indicated better fitting of the adsorption data onto the linear form of the pseudo second order kinetics (PSOK) model. Lower R2 values recorded by the intra particle diffusion and Elovich adsorption kinetic models suggest that the adsorption process was physical and intra- particle diffusion was not the rate controlling step. Similarly, 99% change in nitrate adsorption was accounted by the combined influence of biochar electrical conductivity (EC), zero point of charge (ZPC) and pH. Hence, modification of biochar EC, ZPC and pH are necessary for using biochar to successfully remove nitrate from polluted environments

Assessment of contamination sources of trace metals in wastewater irrigated vegetable garden soils of Kano, Northern Nigeria

Heavy metal pollution is on the increase especially in urban centers where there were proliferation of industrial estates, vehicular emissions and high wastewater reuse. The distribution and potential contamination sources of trace metals (Fe, Nb, Pb, Rb, Sr, Ti, Y and Zr) in long-term wastewater irrigated garden soils were investigated by using radioisotope excited X-ray fluorescence. The result indicates that the soils have elevated concentration of Fe, Pb, Ti and Y in comparison with mean concentration in soils worldwide. Principal component analysis (PCA) and cluster analysis (CA) were performed and all highlighted the origin of these metals as being from natural sources which we attributed to the weathering of the parent materials from which the soils originated from and also to atmospheric dust deposition. Enrichment factor (EF) calculated using Ti as a reference element revealed little to no anthropogenic influence, further confirming the source as mainly natural.Nigerian Journal of Technological Researc

Heavy Metals Source Apportionment and Human Health Risk Assessment of Contaminated Soils of Zamfara State, Nigeria

Progressive illegal artisanal mining activities threaten public health without functional law enforcement on pollution control and proper management practices. This is not an exception of Zamfara State, Nigeria, where a large portion of the populace participates in artisanal mining. The study was conducted to assess the level of health risk associated with heavy metals contaminated soils of Zamfara state, Nigeria. Soil samples were collected from five mining locations (Abare, Bagega, Dareta, Sunke, and Tungar Kudaku) and Anka-town (control site) with no record of mining activities. In each place, bulked soil samples were collected from three sites (mining site, processing site, and village), and the concentration of six heavy metals (Fe, Pb, Cd, Cr, Zn, and Ni) in all the samples were analyzed. The result of the principal component analysis and correlation analysis revealed that Pb, Zn, Cr, and Ni originated from the same source, i.e., anthropogenic/mining activities. While Fe and Cd originated from the geogenic processes because of their high abundance in the soil of the study area, as Anka-town (control site) also recorded high concentrations of Fe and Cd. Health risk assessments were carried out in two groups of population (adult and children) through three exposure pathways (i.e., ingestion, dermal contact, and inhalation). The results showed that ingestion dominated dermal contact and inhalation pathways, and Fe is the riskiest metal while Cd and Ni have the lowest risk of exposure for daily intakes. The non-cancer hazard quotient (HQ) values were all recorded below 1. For the total hazard index (THI), all the adult's exposure pathways were negligible, while for children, only Bagega has ingestion of heavy metals exceeding one (1.10), indicating that non-cancer health risks for children exist. The other four mining locations, Abare, Sunke, Tunga, and Dareta, have values approaching one (i.e., 0.71, 0.60, 0.50, and 0.74, respectively). While for Anka town, which is the control site, it has a value far less than one (0.16). These indicate that all the study locations have the potential for children's health risk through ingesting food produced from contaminated soils. Therefore, there is an urgent need to apply remediation measures immediately to combat complications raised due to heavy metal contaminations