Abstract
Bottom sediment qualities in Ihetutu minefield were assessed to ascertain the impact of Pb-Zn mining activities on the sediments from streams, rivers and ponds in the area. Levels of Cu, Zn, Fe, Ni, Mn, Pb, Cd and Cr and some physico-chemical parameters were measured in bottom sediments taken from four sampling stations (streams/mine pits) within Ihetutu minefield of Ishiagu which receives discharges from mining and human activities, and a control sampling station in Uturu (about 12 km away from study area). The study was conducted in four seasons (Rainy, Late Rainy, Dry, and Late Dry Seasons). Sample digestion was done with a temperature adjustable block digester. Heavy metal analysis was carried out with Flame atomic absorption spectrophotometer (FAAS) while other physico-chemical parameters were determined with standard field and laboratory procedures. Ranges of mean values of results obtained were; pH = 5.81 - 6.44, EC = 269.00 - 1545.00 μS/cm, Cl− = 43.30 - 112.33 mg/kg, alkalinity = 0.70 - 1.25 mg/kg, NO3- = 5.90 - 7.90 mg/kg, TOC = 0.81 - 1.75 mg/kg, TOM = 1.40 - 3.02 mg/kg, Cu = 4.74 - 50.93 mg/kg, Zn = 26.78 - 57.07 mg/kg, Fe = 1066.19 - 1764.05 mg/kg, Mn = 36.66 - 42.96 mg/kg, Ni = 4.02 - 17.19 mg/kg, Pb = 38.01 - 162.23 mg/kg, Cd = 1.01 - 25.90 mg/kg, and Cr = 1.23 - 1.62 mg/kg. Assessment of heavy metals pollution, using pollution indices revealed that Contamination factor ranged from moderate to very high degree of contamination while Pollution load index also showed a deterioration of bottom sediment qualities. Geoaccummulation index indicated moderate to very high pollution, especially with Cu, Zn, Pb, and Cd in the mine pit, while Enrichment factor indicated high enrichments and inputs from anthropogenic sources especially, the Pb-Zn mining activities. Pollution of the area by heavy metals was in the order of Fe > Pb > Zn > Mn > Cu > Ni > Cd > Cr. Highest positive correlation (r = 0.992) was between Pb and Cu while the highest negative correlation (r = 𕒴.789) was between Ni and Mn. Analysis of variance (ANOVA) at significance level, α = 0.05, showed no statistically significant differences in the sampling stations (p > 0.05). Compared to background (control), DPR and other standard guidelines/values, bottom sediments from Ihetutu minefield were highly polluted with Pb, Zn and Cu especially at the mine site. The overall results from the study revealed that toxic substances released from the prolonged Pb-Zn mining activities in the study area have impacted negatively on the bottom sediments, thereby also possibly deteriorating the quality of lives of the bottom sediments dwelling organisms in the streams, rivers, and pits/ponds in the area.
Highlights
Mining is a huge economic resource at Ihetutu, Ishiagu, Nigeria
The objective of this paper is to evaluate the qualities of the bottom sediments from streams, rivers, and ponds in Ihetutu mining areas of Ishiagu, by assessing the levels of contamination by toxic substances including heavy metals and other physico-chemical species released to the environment from the Pb-Zn mining operations, Data obtained from the study will be compared with control and standard guideline values including Department of Petroleum Resources (DPR), and other international standards
The evaluation carried out on bottom sediments in Ihetutu minefield, using pollution indices/models to estimate the levels of heavy metal contaminations/enrichment confirmed that the bottom sediments of the pits/streams in the study area were all contaminated to various degrees by heavy metals through point and non-point anthropogenic sources
Summary
Mining is a huge economic resource at Ihetutu, Ishiagu, Nigeria. Despite the huge benefits accruing from the mining business to the government, individuals, and corporate bodies engaged in it, its activities constitute the most important source of heavy metals in the environment. It is a business that seriously destroys the environment, with the large volumes of wastewater, drainage wastes and tailings, generated through its activities; and spoils the landscape and the surrounding environment with inorganic pollutants, heavy metals. According to Zhang et al (2011), lead/zinc mining and smelting activities are some of the primary sources of heavy metals pollution in the environment. Intensification of heavy metal pollution, occurs when mining is carried out in a crude manner and associated wastes are untreated and improperly dumped or discharged (Nwaugo et al, 2007). Heavy metals have serious ecological effect as a result of their toxicity and their accumulation in both sediment and biota because they are not biodegradable and undergo a global ecological cycle (Ahmadipour et al, 2014)
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