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In this study an attempt was made to determine the source(s) and nature of Pb in environmental media of Ibadan, one of the largest cities in west Nigeria. Seventy-three samples comprising forty stream sediments, twenty-five soils and eight rocks samples were used for the study. Mineralogical compositions of the samples were determined by X-ray diffraction. The elemental constituents were determined using ICP-MS; while the Pb isotopes were determined using Sector-field ICP-MS. Sequential analysis of selected samples was carried out using a modified Tessier's five-step method. The dominant minerals identified were quartz, kaolinite, k-feldspar, and plagioclase. The concentrations (mg/kg) of Pb in soils, sediments, and rocks ranged from 13.00-470.00; 89.00-3288.00 and 2.90-20.30, respectively. The 204Pb, 206Pb, 207Pb, 208Pb ranged from 1.72-47.41; 30.69-779.68; 27.00-664.46 and 65.67-1642.27 in the soils and sediments, respectively, while they ranged from 0.02-0.07; 0.56-2.33; 0.38-1.56 and 1.19-4.13 in the rocks. Further evaluation of Pb concentration in the soils and sediments revealed high to extreme Pb pollution status, while the calculated Pb isotopic ratios (IRs) in the soil and sediments varied from that of the underlying bedrocks. The IRS in soils and sediments were characterized by low (1.161-1.172 and 1.127-1.200, and 2.281-2.444 and 2.276-2.474) 206/207 Pb and 208/207 Pb, while those of the rocks were high (1.456-1.753 and 2.647-3.149), indicating additional anthropogenic sourcing of Pb in the soils and sediments. The analyzed Pb revealed fractions more partitioned in the reactive geochemical phases with the Pb partitioned in the exchangeable (0.11-0.23%), carbonate (9.00-43.58%), reducible (8.32-13.53%) and organic/sulfides (42.78-82.45%) phases. This implies that there may be enhanced mobility of Pb in the environmental samples and ultimately bio-adsorption into living tissues in the environment.

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BACKGROUND: Metal recycling factories (MRFs) have developed rapidly in Nigeria as recycling policies have been increasingly embraced. These MRFs are point sources for introducing potentially toxic elements (PTEs) into environmental media. OBJECTIVES: The aim of this study was to determine the constituents (elemental and mineralogy) of the wastes (slag and particulate matter, (PM)) and soils around the MRFs and to determine the level of pollution within the area. METHODS: Sixty samples (30 slag samples, 15 soil samples and 15 PM samples) were collected for this study. The soils, slag and PM samples were analyzed for elemental constituents using inductively coupled plasma optical emission spectrometry. Mineralogy of the PM was determined using scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), and soil mineralogy was determined by an X-ray diffractometer (XRD). RESULTS: The results of the soil analyses revealed the following concentrations for the selected metals in mg/kg include lead (Pb) (21.0-2399.0), zinc (Zn) (56.0-4188.0), copper (Cu) (10.0-1470.0), nickel (Ni) (6.0-215.0), chromium (Cr) (921.0-1737.0) and cadmium (Cd) (below detectable limit (Bdl)-18.1). For the slags the results were Pb (68.0-.333.0), Zn (1364.0-3062), Cu (119.0-1470.0), Ni (12.0-675.0), Cr (297-1737) and Cd (Bdl-15.8). The results in µg/g for the metal analysis in PM were Pb (4.6-160.0), Zn (18.0-471.0), Cu (2.5-11.0), Ni (0.8-4.2), and Cr (2.5-11.0), while Cd was undetected. The slags are currently utilized for filling the foundations of buildings and roads, providing additional pathways for the introduction of PTEs into the environment from the suspended materials generated from mechanical breakdown of the slags. CONCLUSIONS: The MRFs were found to have impacted the quality of environmental media through the introduction of PTEs, impairing soil quality, in addition to PM, which can have detrimental health consequences. Further studies on the health implications of these pollutants and their impacts on human health are needed. COMPETING INTERESTS: The authors declare no competing financial interests.

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BACKGROUND: Increased growth of industrial activities, especially in urban centers, is one of the main sources of toxic substances in Nigeria. The level of these impacts is not well known. Soil and sediment samples from one such industrial area were examined for their mineralogical composition and heavy metals contents in order to assess the level of contamination and potential ecological risk status. METHODS: Mineralogical composition of the media and their heavy metals concentrations were determined using X-ray diffractometry and inductively coupled plasma-mass spectrometry methods, respectively. Ecological risk assessment was carried out using single (contamination factor, geo-accumulation index, enrichment factor) and multi-elemental (contamination degree, pollution index and modified pollution index) standard indices. RESULTS: The average heavy metal concentrations in soils and sediments followed the order magnesium (Mn) > chromium (Cr) > lead (Pb) > copper (Cu) > cadmium (Cd) > cobalt (Co) > nickel (Ni), with corresponding values for soils and sediments of 324.3, 79.9, 66.1, 40.7, 14.3, 9.1, 6.8 mg kg-1 and 266.8, 78.6, 40.6, 39.8, 12.9, 8.4, 4.6 mg kg-1, respectively. Principal component (PC) analysis of the results indicated three main sources of metals (industrial, vehicular activities and geogenic input). Evaluated contamination factor (Cf), enrichment factor (Ef) and geo-accumulation index (Igeo) revealed very high contamination for Pb, Cd and Cu in all of the samples, with calculated pollution index (PI) and modified pollution index (MPI) revealing that all the samples were severely polluted. Calculated potential ecological risk factor (ERi) within the industrial area demonstrated a strong potential ecological risk for Cd, Pb and Cu. CONCLUSIONS: Activities in the industrial area have affected the quality of the analyzed environmental media, with possible detrimental health consequences. Regular environmental monitoring of the industrial area and the formulation of appropriate policies that support reduction of contamination are strongly recommended. However, due to the limitations of comparing site samples with a single control sample in this work, further study is recommended to compliment this preliminary study. COMPETING INTERESTS: The authors declare no competing financial interests.

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BACKGROUND: Active cultivation of wetlands without consideration of the quality of the sediment is a common practice in the city of Lagos. Wetlands in several parts of the city have been cleared for growing vegetables and other crops. As a buffer for all surface run-off from the surrounding areas, wetlands are a depository for whatever contaminants are sourced from the catchments; hence the need to ascertain the quality of sediment on which edible crops are grown to determine suitability for agriculture. METHODS: Wetland water samples were tested for pH levels, electrical conductivity, and total dissolved solids. Randomly selected core samples from one of the cultivated wetland areas located in the city center were taken to up to 8 cm in depth, then dried, recovered from the barrel and divided into groups of the following depths: 0-2 cm, 2-4 cm, 4-6 cm, and 6-8 cm. The dried and divided samples were subsequently sieved and analyzed for metal content using inductively coupled plasma mass spectrometry. Results for copper (Cu), lead (Pb), zinc (Zn), nickel (Ni), chromium (Cr) and vanadium (V) were geochemically evaluated. RESULTS: The wetland water samples were found to be acidic, ranging from 5.9-6.4. The electrical conductivity was 430-500 µS/cm, and total dissolved solids, 280-320 mg/L. The metal content results (in mg/kg) for samples from 0-2, 2-4, 4-6 and 6-8 cm depths were: Cu (13-861, 12-752, 10-899 and 11-707); Pb (29-1646, 26-2660, 33-2400 and 25-1818); Zn (112-7237, 76-9908, 63-7517 and 47-6579); Ni (3-219, 3-178, 3-186 and 3-176); Cr (10-147, 9-157, 14-160 and 16-147); and V (14-72, 12-75, 17-77 and 19-77). The evaluated results showed that the selected metal concentrations exceeded various guideline values. Calculated geo-accumulation index, metal ratio, and enrichment factor showed marked enrichment of metals in the wetland sediment samples. DISCUSSION: For the majority of the metals observed, the correlation matrix revealed strong positive relationships. For Cu, Pb, Zn, Ni, and Cr, there was a correlation matrix >0.8. This indicates similar origin and sourcing of the sediments. Vanadium, however, displayed a negative correlation with all the other elements. CONCLUSIONS: The study revealed that most of the cultivated sediment samples contained elevated levels of potentially toxic elements in the form of Pb, Cu, and Zn. The acidic nature of the wetlands water in the sediment samples also make them unsuitable for cultivation as the possibility of metal dissolution in transpirated water and bio-accumulation of potentially toxic elements in the cultivated vegetables is high.

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The aim of this study was to assess the heavy metal content of the dust generated by the Sagamu cement factory and its attendant health hazards on the immediate environment, especially on the inhabitants of the area. A total of 25 samples were collected and analyzed using inductively coupled plasma-optical emission spectrometry. Records of medical ailments associated with heavy metal toxicity were also compiled from the Obafemi Awolowo Teaching Hospital situated in the town. The results for some of the selected heavy metals showed the following pattern: limestone: Cd (n.d.-1.7 ppm), Pb (42-48 ppm), Cu (3.0-11 ppm), Zn (7.0-53 ppm) and Ni (3.0-8.0 ppm); shale: Cd (0.3-1.1 ppm), Pb (17-22 ppm), Cu (2.0-11 ppm), Zn (17-147 ppm) and Ni (3.0-18 ppm); dusts: Cd (0.5-0.7 ppm), Pb (32-52 ppm), Cu (2-16 ppm), Zn (5-152 ppm) and Ni (2-17 ppm); soils: Cd (0.5-1.1 ppm), Pb (28-49 ppm), Cu (22-35 ppm), Zn (43-69 ppm) and Ni (13.0-17 ppm). High levels of heavy metals were found in the rocks and soils. We propose that the high levels of metals in the dust and soil were acquired from the raw materials used by the cement factory and from active industrial discharge from this same factory. Medical records and the current health situation of the local residents in the study area reveal that there have been increases in the prevalence of diseases linked to heavy metal toxicity in the environment, especially those related to dust generation.

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