An Assessment Of Environmental Impact Of Mine Blasting In New Abirem And Its Environs In The Eastern Region Of Ghana

Abstract

Blasting can lead to morbidity and mortality of human as well as damage of properties when not monitored and managed properly. Mine Blasting activities generate seismic effects including vibrations, air overpressure, flyrock, fumes and dusts. The environment can be polluted by blasting residues of rocks like hexogen, trinitrotoluene and octogen which have caused a lot of biodegradation and hazardous effects on ecosystem survival in a mine vicinity. The seismic effects also result in leaching of chemicals to pollute both surface and underground waters in New Abirem and its environs which lead to reduction of terrestrial plant biomass and fertility of earthworm. In view of this, the study was conducted to assess the ecological impact of mine blasting residues, ground vibration, air blast and heavy metals on the ecosystems around Newmont by collecting and analyzing water samples in three communities (New Abirem, Afosu and Adausena) as well as measured seismic effects. The noise and vibrations were determined by using the Seismograph from twenty (20) blast shot at the mine pit from October, 2020 to March, 2021. Focus group discussions and household interviews techniques were utilized to assess community perceptions of mine blasting effects on the mine environment. Physicochemical parameters including temperature, dissolved oxygen, pH, electrical conductivity, ammonia and nitrate, were determined. Heavy metal concentrations in 108 water samples collected from five different locations, made up of two sites along one of the tributaries of Birim River, one site each from two streams, and the Newmont pit were determined using the technique of Milestone Acid Digestion Microwave ETHOS 900 followed by the atomic absorption spectrophotometry (AAS). The data was examined with a one-way analysis of variance and significant differences of p < 0.05 were adopted as well as Tukey’s HSD to separate means. The average blast vibration measured at the compliance locations AF-BMP (Afosu), NABBMP (New Abirem) and AD-BMP (Adausena) were compared with 2mm/s [Explosives Regulations, 2012 (L.I. 2177), Section 199]. The average blast air overpressure measured at AF-BMP (Afosu), NAB-BMP (New Abirem) and AD-BMP (Adausena) were also compared with 117 dBL [Explosives Regulations, 2012 (L.I. 2177), Section 199]. The mean, minimum and maximum blast on air overpressure and ground vibration for each monitoring point respectively were measured and the results were found to be within mining explosives limits. The physicochemical parameters mean level were ranged 24.93 – 27.53 0C (water temperature), 4.66 - 5.36 mg/L (Dissolved Oxygen), 109.79 – 125.98 μS/cm (EC), 7.51 – 7.88 (pH), 0.01 – 0.53 mg/L (NH3) and 0.22 – 0.42 mg/L (NO3). The results revealed significant difference in all the physicochemical parameters (p < 0.05). The Dissolved Oxygen concentrations at all the five sampling sites were below 5 mg/L which indicated that the water was polluted and adversely affected aquatic life. The pH measurements in the site of Holy Child and Afosu have slightly acidic pH. The minimum and maximum concentration levels of Cu, Fe, Zn, Cr and Mn in the water were (0.01- 0.02) mgL-1, (0.02 – 0.33) mgL-1, (0.08 – 0.93) mgL-1, (0.01) mgL-1 and (0.02 – 0.10) mgL-1 respectively and there were significant differences between the various sites (p < 0.05) compared with the control. The mean levels of Cu, Fe, Zn, Cr and Mn were recorded to be within the permissible limits. The degree of contamination levels identified in a location are categorized as follows: unpolluted (Cd < 1), moderately polluted (Cd =1 - 3) and strongly polluted (Cd > 3). The calculated degree of contamination index, Cd values for Holy Child, Aboabo and Adenkyensu locations were greater than 3 mgL-1, the criteria limit for drinking, therefore sites were strongly contaminated. In addition, the pollution index of heavy metals in the water samples from all locations used were greater than the critical value for drinking water, 100 mgL-1 except Newmont site which recorded 93.91 mgL-1. Generally, the blasting operation at Newmont, Akyem mine is within the Explosives Regulations, 2012 (L.I. 2177), Section 199 as well as the international Standard quoted AS 2187.2 – 1993. It is recommended that water used for drinking, domestic chores, agricultural (irrigation) or industrial use by communities along the tributaries of the Birim River must be treated before use. There is also a need for research and academic institutions to support nongovernmental organizations (NGOs) in their efforts to protect and manage water resources through research for long-term sustainable management.