Abstract
This research was carried out to investigate effect of ethylenediaminetetraacetic acid and ammonium oxalate on the prevalence of microorganisms and removal of aluminum in soil by bitter leaf plant (Vernonia amygdalina). The test plant was sown in aluminium-polluted soil (conc. = 150mg Al kg-1 soil). One gram of each chelating agent was dissolved in 1.5 litres of water and applied at different time intervals; application on a day prior to sowing of test plant in metal-polluted soil, application on the day of planting, application at one week after planting; at one month after planting. For the control soils, chelating agent were not added, although aluminium-contaminated. In the control, aluminium concentrations in leaf tissues were 16.20mg/kg compared to a staggering 9.20mg/kg in EW1 and 5.24mg/kg in OD1. However, heavy metal concentration of the leaves of Vernonia amygdalina in the control, EW1, EM1, OD-1 and OW1 were significantly similar (P>0.05). Concentration of aluminium in the stem tissues were also similar in ED1, EM1, OD-1, OD1 and OW1 (P>0.05) were concentration ranged from 5.42mg/kg to 7.98mg/kg. Compared to the control, aluminium concentration in stem tissues was 4.95mg/kg comparable with 3.42mg/kg in OM1. In the plant root, OD1 had the highest accumulation of aluminium in the root (16.92mg/kg); however concentrations of aluminium in the roots were also statically similar in OW1 (15.08mg/kg), OM1 (13.84mg/kg), OD-1 (14.72mg/kg), EM1 (15.12mg/kg) and in the control (13.52mg/kg). Results of the following also showed concentrations of residual aluminium in the soil ranging from 68.25mg/kg in the control to 109.85mg/kg in ED1 soil. After three months of planting, results show that the total bacteria count for ED1 (5.3 × 104 cfu/g) had the highest while OM1 (3.9 × 103 cfu/g) had the lowest. For fungi isolates, the highest was control (8.2 × 103 cfu/g) whereas the lowest were OD–1 (6.8 × 102 cfu/g). The most prevalent microorganisms in the spiked soil with heavy metal are Bacillus subtilis represented in all the samples for bacteria while Aspergillus niger representing fungi. The perseverance of the test plant in the aluminium spiked soil is an indication of adaptation to the stress imposed by the concentration of aluminium in soil. In spite of the metal composition within the soil, it was observed that a number of microorganisms existed. This may therefore suggest a favourable environment for the microorganisms within the soil rhizospheric region of Vernonia amygdalina.Keywords: EDTA, oxalate, aluminium, pollution, remediation, Vernonia amygdalina
Highlights
Microorganisms and plants are usually used for the removal of heavy metals
The aim of this research is to evaluate the effects of collaboration of the chelating agent and the indigenous microorganisms in assistance to the remediation of aluminium spiked soil
The most prevalent microorganisms in soil that are spiked with heavy metal are Bacillus subtilis represented in all the samples for bacteria while Aspergillus niger representing fungi in all samples (Omoregbee et al, 2015)
Summary
Microorganisms and plants are usually used for the removal of heavy metals. Bioremediation which is a natural process and its importance to biodiversity (above or below the ground) is increasingly considered for clean-up of metal contaminated and polluted ecosystem (Akshata et al, 2012). All the metals are toxic, but some of these are useful in low concentration. These metal toxicity cause serious morbidity and mortality (Surajana et al, 2009). The isolation of heavy metal resistant microorganisms and the understanding of the mechanisms they use in order to remove this kind of pollutants may contribute to the development of improved bioremediation processes (Akshata et al, 2012).
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