Heavy Metals Accumulation by Indigenous Plants Growing in Contaminated Soil in a Gold Mining Area in Ghana

Phytoremediation is an environmentally friendly, low cost biotechnological process that is fast gaining prominence in the cleaning of contaminated soils in the tropics. The accumulative potential of indigenous or native plants for heavy metals in mine tailings at the Storage Facility of the Chirano Gold Mine Limited, Ghana was investigated. Plant species were sampled in five plots, each 32 m2. Samples of plants were harvested and separated into roots and shoots and the corresponding rhizospheric soil samples collected. They were analysed for the total concentrations of heavy metals; Arsenic (As), Cadmium (Cd) and Zinc (Zn) using Atomic Absorption Spectrophotometer. Bioavailable fractions of studied metals in the soil samples were determined with the formation of metal complex with Ethylenediaminetetraacetic acid and ammonium acetate reagents. The hyper-accumulation potential and mobility of heavy metals within the plants were determined from the bioaccumulation and translocation factors. Differences in mean concentrations of heavy metals in the plants (shoot, root and whole) were separated using Tukey B Analysis of Variance, SPSS version 20, at significant level of p < 0.05. The mean concentrations of total and bioavailable As, Cd, and Zn in the soil samples varied with Zinc being most predominant (13.20 mg/kg). However, As was the most available with 39% bioavailability. The soil elemental concentrations of As (3.0 mg/kg), Cd (0.29 mg/kg) and Zn (13.20 mg/kg) were below the WHO recommended standards of 12 mg/kg, 1.4 mg/kg and 200 mg/kg for As, Cd and Zn respectively. The concentrations of all metals in the plant organs varied between species. In all plant species Zinc was the most accumulated heavy metal, recording the highest level of accumulation (135.76 mg/kg) in the root of Euphorbia heterophylla. Bioaccumulation factor as expressed by total and bioavailable metal concentrations in soil indicate that all the plant species demonstrate good hyperaccumulation and phytostabilisation potential for Zn and Cd whilst 13 and 8 plant species demonstrate good phytoextraction potential for As. The translocation factor indicate that 8 plant species are good phytostabilisers for Zn, 7 plant species for Cd and 10 plant species for As. The accumulative and phytostabilisation potential of these plant species provide useful information about their selective exploitation for effective phytoremediation of the tailings dam at Chirano Gold Mine. Keywords: phytoremediation, heavy metal, hyperaccumulation, phytostabilisation, indigenous plants, bioavailable

Biodegradation of Crude Oil Polluted Soil by Co-Composting with Agricultural Wastes and Inorganic Fertilizer

Pollution of the environment by petroleum products is inevitable due to oil production,   transportation and distribution activities.   The present study is aimed at examining the extent of bioremediation that can be achieved in crude oil polluted soil after supplementing with organic manure (poultry droppings and goat dung); inorganic fertilizer (NPK 15:15:15) and saw dust respectively. A bioremediation study was carried out on soil experimentally polluted with Bonny Light crude oil by supplementation with organic and inorganic nutrients (poultry manure, goat dung, saw dust and NPK fertilizer). The efficacy of the treatments was monitored for 112days by the measurement of total hydrocarbon utilizing bacteria load and some physico-chemical parameters. The polluted soil (Control) sample had mean bacterial counts of 8.8x104, 9.0x104, 9.2´104, 9.9x104 and 7.6x104 cfu/g respectively. Sample treated with NPK fertilizer had mean bacterial counts of 4.4x104, 4.6x104, 4.7x104, 4.9x104 and 5.2x104 cfu/g on days 0,28,56,84 and 112 respectively; sample treated with poultry manure had mean bacterial counts of 1.6x104, 1.8x104, 2.0x104, 2.4x104 and 2.7x104 cfu/g on days 0, 28,56,84 and 112 respectively; the saw dust treated sample had mean bacterial counts of 2.0x104, 2.3x104, 2.7x104, 2.9x104 and 3.0x104 cfu/g on days 0,28,56,84 and 112 respectively while that treated with goat dung had mean bacterial counts of 9.3x104, 9.5x104, 9.6x104, 9.8x104and 9.9x104 cfu/g on days 0,28,56,84 and 112 respectively.  There were differences in the physico-chemical analyses from the diverse samples. After statistical analysis (P£0.05) there was a significant difference between the different treated samples from the control. The results suggest that nutrient supplementation would be effective in the remediation of crude oil polluted soils. The potentials of various treatment options for the bioremediation of crude oil polluted soils seems to hold the most immediate solution especially for use in areas that would be adversely affected by physical or other removal methods. In this study, the reduction of oil in the treated samples is evident, polluted samples supplemented with fertilizer and poultry manure respectively proved to be the best options during the 112 days study period. This study shows that those organic supplements containing nitrogen and phosphorus have great potentials for the remediation of soils contaminated with petroleum hydrocarbon within a reasonable time. Keywords: Bioremediation, Crude Oil Polluted Soil, Organic Manure (poultry droppings and goat dung); Inorganic fertilizer (NPK 15:15:15), Saw dust

Levels of heavy metals and contamination status of a decommissioned tailings dam in Ghana

Heavy metal pollution from tailings has become a major global concern due to its toxicity, persistence and accumulative potential with its detrimental effects on public health and environmental receptors. In a bid to determine the contamination status of a decommissioned Tailings Storage Facility (TSF 2) from Chirano Gold Mine limited (CGML), scoop of mine tailings were collected down to a depth of 20 cm from nine sampling sites within a 8100 m2 grid. Concentrations of As (0.7 to 3.3), Pb (1.3 to 2.2), Cr (0.9 to 1.9), Cd (2.0 to 2.6), Cu (5.5 to 6.5), Zn (2.4 to 3.6) and Fe (4.5 to 12) mg/kg were below FAO/WHO permissible limits. Concentration of heavy metals statistically varied between sampling sites (p < 0.05). The geoaccumulation index and contamination factor revealed that, TSF 2 is uncontaminated with As, Pb, Cr, Cu, Zn and Fe. However, mine tailings were significantly enriched with Cd, and thus likely to pose ecological risk to the surrounding environment. In general, the tailings dam is not progressively deteriorating in accordance to pollution load index. Findings of this study would contribute to the environmental database of gold mine tailings at CGML to assist future remediation of the Tailings Storage Facility.

Repellent and larvicidal properties of selected indigenous plants in the control of Anopheles mosquitoes

Background & objectives: Widespread pyrethroid resistance and plastic-feeding behaviour of most malaria vectors across Africa threaten the efficacy of current insecticide-based vector control interventions like Insecticide-Treated Nets (ITNs) and Indoor Residual Spraying (IRS). This study examined the larvicidal activity ofMorinda citrifolia against Anopheles gambiae larvae and the repellent properties of Morinda citrifolia (Noni), Moringa oleifera (Moringa), and Ocimum basilicum (Basil) as complementary vector control tools against Anopheles gambiae sensu lato (s.l.). Methods: Noni, Basil, and Moringa oil extracts were obtained with the extraction techniques; Soxhlet, steam distillation and maceration respectively, using hexane and ethanol. The effectiveness of the extracts was assessed using the WHO standard larval susceptibility bioassay and guidelines for repellent efficacy. Following bioassays, effective doses (ED) and lethal concentrations (LC) were determined. Gas Chromatography-Mass Spectroscopy analysis was performed to identify the bioactive chemical components of the extracts of Moringa oleifera and Ocimum basilicum. Results: Emulsified Morinda citrifolia seed oil had LC50=68.3, LC90=130.9 and LC99.9=222.5, and ED99. 9=308.3%v/v, the ethanolic extract of Moringa oleifera leaves had ED99.9= 1.25g/ml, and essential oil of Ocimum basilicum leaves had ED99.9=0.28g/ml against Anopheles gambiae. Interpretation & conclusion: The results obtained indicated that seed oil of Morinda citrifolia, essential oil of Ocimum basilicum, and crude extract of Moringa oleifera have repellent activity against An. gambiae s.l. The complete protection time (CPT) of Morinda citrifolia, Moringa oleifera, and Ocimum basilicum was 120 min, 72 min and 84 min at ED99.9 respectively. Morinda citrifolia oil exhibited larvicidal effects against the larvae of An. gambiae s.l. The results provide valuable information for the use of the plants as biocides