This study assessed the distribution of heavy metals in soil and their subsequent accumulation in plants at a site at Umudike, Nigeria, that had been contaminated by agrochemicals. Soil and plant samples were analysed for zinc (Zn), chromium (Cr) and cadmium (Cd). The highest concentrations of Zn (251.50 mg/kg) and Cd (61.33 mg/kg) were obtained at a soil depth of 0-10 cm. The highest concentrations of Zn (16.52 mg/kg), Cd (27.12 mg/kg) and Cr (164.07 mg/kg) were accumulated by Baphia nitida. The levels of Cd, Cr and Zn in soil were 27. 97-61.33, 24.97-45.43 and 148.57-251.50 mg/kg, and their concentrations in B. nitida were 16.18-27.13, 97.99-164.07 and 0.10-16.52 mg/kg, respectively. There were significant correlations between Cd and Cr and Cd and Zn in soil, as well as between Cd and Cr in plants.The concentration of Cd in soil reflected a state of pollution relative to Dutch criteria for soil and the FAO/WHO Codex Alimentarius Commission.

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Farmers are constrained to farming on lands adjoined to sources of pollution without considering the health implications of consuming crops grown on such lands. The main route of entry of heavy metals in human body is via ingestion of food contaminated with heavy metals. Heavy metal toxicity has proven to be a major threat and there are several health risks associated with it. This, therefore, necessitated the determination of heavy metals in sawdust, distribution in soil and accumulation in plants at Ahiaeke timber market in Umuahia, Abia State. The study assessed metals (chromium [Cr], zinc [Zn], cadmium [Cd], and copper [Cu]) in sawdust particles, their distribution in soil and accumulation in plants. The highest concentration of Zn (51.00±1.84 mg/kg) and Cr (0.170±0.014 mg/kg) was observed at the sawdust dump 2, Cu (8.24±0.60 mg/kg) was highest at sawdust dump 1 while Cd (4.72±0.071 mg/kg) was highest at sawdust dump 3. The values of the highest concentration of Zn (119.7±7.02 mg/kg), Cu (75.85±4.80 mg/kg) and Cd (22.39±3.30 mg/kg) in soil were observed in 0-10 cm depth at the distance of 20 m. The values of Zn (119.7±7.02 mg/kg) and Cd (22.39±3.30 mg/kg) in soil is above the maximum permitted levels of 60 mg/kg (Zn) and 0.1 mg/kg (Cd) established by the Codex Alimentarius Commission. The highest concentration of Zn (34.70±7.05 mg/kg), Cu (5.34±0.11 mg/kg) and Cd (2.94±0.515) in plants was assimilated by Centrosema pubescence. The level of Cd in plants is well above the permissible limit (PL) 0.3 mg/kg set by FAO/WHO for vegetables and herbs. Consumption of such contaminated C. pubescence can be a route of entry of Cd in grazing animals’ vis-à-vis the people who depend on such herbivores for protein.

In a bid to diversify the sources of revenue generation in Nigeria, the Government of the Federation has initiated plans to resuscitate coal mining. This study, therefore, assessed the impact of previous mining activities on soil chemical characteristic of the abandoned site. A single factor experiment was conducted in a randomized complete block design (RCBD) with three replications to obtain information on soil status of Iva mined site. Soil samples were collected randomly from ten different sampling points at 0-10, 10-20, and 20-30 cm soil depth in four cardinal points at north (N), south (S), east (E), west (W), and at the centre (c) of crest, middle slope, and valley of Iva mined site. The samples were analysed for heavy metals, macronutrient, soil pH, and organic matter content. The organic matter values ranged from 0.00 ± 0.00 to 1.14 ± 0.02% in dry season and 0.00 ± 0.00 to 1.04 ± 0.06% in wet season, with higher levels of organic matter in the valley (OM ≤ 1.14 %). Soil pH values ranged from 3.98 to 6.00 in wet season and 3.82 to 5.34 in dry season, with higher levels of acidity in the middle slope (pH ≤ 4.37). The range of values of soil macronutrients (K, Mg, N and P) were higher in wet season than in dry season with higher levels of K, Mg, N and P, at middle slope. Similarly, the values of the concentration of heavy metals (Ni and Pb) in soil were higher in wet season than in dry season with higher levels of Ni and Pb at middle slope. The levels of Ni, Pb and Cd in this study are above their allowable limits in Austria, Germany, France, Netherlands, Sweden, and United Kingdom. The high concentrations of Cd and Ni in soils could be taken up in plants via the roots, thus, exposing both man and herbivores to serious health risks.

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Human health challenges resulting from consumption of food contaminated by heavy metals necessitated the investigation of soil and cassava plants around automobile waste dumpsite at Ohiya mechanic village, Abia State, Nigeria. Soil and cassava samples collected randomly at the site were analyzed for cadmium (Cd), copper (Cu), lead (Pb) and chromium (Cr). The values of highest concentration of Cu and Pb in soil was recorded in 0-10 cm, Cr was obtained in 21-30 cm while Cd was in 11-20 cm soil depth. The concentration of Cd (0.11±0.00 to 0.26±0.00 mg/kg) in soil exceed maximum permitted level of 0.1 mg/kg (Cd) by FAO/WHO. The concentration of Pb (0.01±0.001 to 3.24±0.00 mg/kg) and Cd (0.07±0.00 to 2.08±0.00 mg/kg) in cassava plants exceed the permissible limit of 0.3 mg/kg (Pb) and 0.2 mg/kg (Cd) set by FAO/WHO. The Pearson correlation analysis show very strong positive relationship between Cu and Cu (r=0.996) and Pb and Pb (r=0.986) while strong negative relationship exist between Cr and Cr (r= -0.686) and Cd and Cd (r= -0.981) in soil and plant. Based on our findings, the concentrations of Cd in soil vis-à-vis Pb and Cd in plants which exceed maximum permitted level set by Codex Alimentarius Commission FAO/WHO will expose man and animals that relied on soil and cassava plants for food to serious health risks. Consequently, Abia State government should prevent farmers’ access to the site by fencing round the automobile waste dumpsite.

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This study determined the views of respondents in Akwuke and Iva mine communities concerning the impact of coal mining activities on animal and plant species, pattern of settlement, pollution effect and health of people living in these two mined areas in Enugu, Nigeria. Data were generated through sample survey using a well-structured questionnaire and personal observation in the field. Khaya ivorensis (mahogany) was the major tree species that had gone extinct (72% of respondents), and Geochelone sulcata (tortoise) was the major animal species that has gone extinct (80% of respondents) in the two mined areas. Sixty-five percent of the respondents said that water pollution was most severe environmental impact of mining in Akwuke. The major health hazard caused by mining in Akwuke (55% of respondents) and Iva (65% of respondents) was blindness. Indeed, 82.5% of respondents indicated that mining affected the pattern of settlement in the two mined areas. Emphatically, coal mining affected negatively some of the socio-economic activities of the inhabitants of the mined area through removal of vegetation to access coal deposit vis-à-vis blasting, quarrying and crushing of coal.