Biomonitoring of Heavy Metals Level in Wetland Plants of Lagos Lagoon, Nigeria

The purpose of this research was to monitor the distribution of Cd, Cr, Cu, Ni, Pb and Zn in plants of Lagos lagoon wetlands in Nigeria. Water, soil and dominant plants were collected from 46 sampling points for a period of 1 year and analysed using ICP-AES. The order of heavy metals presence in soil samples was as follow: Zn>Cr>Cu>Pb>Cd>Ni. The Zn concentration was the highest whereas the lowest concentration was Ni. All water samples showed varying degrees of contamination across all the sampling points in these wetlands. A greater percentage of all metals concentration for Pb, Cd, Cr and Ni were higher than the permissible limit set by World Health Organisation. Pb ranged from 0.01±0.00 to 0.91±0.04 mg/L, Cd from 0.01±0.00 to 0.31±0.02 mg/L, Cr from 0.05±0.00 to 1.15±0.01 mg/L, Ni from 0.01±0.00 to 0.52±0.03, Cu from 0.21±0.01 to 1.11±0.01 mg/L and Zn ranged from 0.15±0.00 to 10.28±0.02 mg/L. The median values of each metal that the shoots and roots of individual plants accumulated metals in the order: Zn>Cu>Pb>Cr>Ni>Cd. Ipomea aquatica had the highest concentration of Pb in its shoot (1.12 mg/kg) while Ludwigia adscendens had the least (1.12 mg/kg) in its shoot. Pb level in the roots was highest in Eichonia crassipes (5.69 mg/kg). The highest level of Cr in shoot (2.23 mg/kg) and root (5.41 mg/kg) was observed in Commelina benghalensis while Cr concentration is lowest in the shoot (0.04 mg/kg) and root (0.18 mg/kg) of Althernathera philoxerrides. Ludwigia adscendens had the lowest concentration of Ni in its root (0.01 mg/kg). The highest shoot concentration of Cu (4.21 mg/kg) was observed in Eichonia crassipes while Ipomea aquatica had the lowest concentration in its shoot (0.23 mg/kg). Paspalum vaginatum’s root had the highest Cu concentration (12.32 mg/kg) while lowest concentration of Cu was observed in the root of Sagittaria sagittifolia (0.69 mg/kg). Transfer factors for most of the plants species were less than 1, indicating that metals accumulated by these plants were largely retained in the roots. A. philoxerrides had translocation factor greater than one for Ni (10.30), while for Cr was 1.25 and 1.40. This present findings indicate that, despite ecological similarities, the different plant species tend to respond differently to exposure to heavy metals and also in their ability to accumulate the various metals. Thus, heavy metals sequestration from the soil to these plants characterized them as metals pollution indicators.Keywords: wetland plants, heavy metals, biomonitoring, bioaccumulation capacity, translocation facto

Mycoremediation of petroleum hydrocarbon polluted soil by Pleurotus pulmonarius

Mycoremediation of petroleum hydrocarbon polluted soil was investigated using Pleurotus pulmonarius for a period of 62 days. Hydrocarbon (Petrol + diesel + spent petrol engine oil + spent diesel engine oil in ratio 1:1:1:1) polluted soil in 2.5%, 5%, 10% and 20% concentration were inoculated and incubated with pure culture of P. pulmonarius obtained from commercial mushroom laboratory of Federal Institute of Industrial Research Oshodi (F.I.I.R.O.) Lagos Nigeria. Inoculation was done by adding 20 g of vigorously growing spawn of P. pulmonarius. A set of control treatment was used where different concentrations of the petroleum hydrocarbon were added to all soils but no inoculation with the fungus. The results showed that the initial organic matter content of the soil increased with increase in the concentration of petroleum mixture added to the soil.  The highest impact of P. pulmonarius on the organic matter content of the soil was noticed in soil with 10% concentration treatment (68.34%) and the least was in soil with 2.5% treatment concentration (22.12%). The initial nitrogen, potassium and phosphorus contents of the soils samples decreased with increase in the petroleum concentration. The difference was significant at 2.5%, 5%, 10% and 20% concentration of contamination for organic matter, nitrogen, potassium and phosphorus (p<0.05). A significant (p<0.05) reduction in concentration of the heavy metals (manganese, copper, and zinc) after 62 days of incubation with P. pulmonarius suggested that the mushroom is a good agent for heavy metal remediation. The highest reduction of Mn was at 10% concentration (24.00±0.04 to 1.73±0.10), Cu at 10% concentration (37.24± 0.02 to 0.00), and Zn was at 10% concentration (63.03±0.02 to 5.75±0.14). The percentage loss of the TPH due the growth of P. pulmonarius decreased with increase in the concentration of petroleum added to the soil. The percentage loss for 2.5%, 5%, 10% and 20% concentration are 52.60%, 38.71%, 27.20% and 8.31% respectively. Heptane, toluene, octane, M-p xylene, Alpha xylene, nonane, propylbenzene, decane, tridecane, tetradecane, anthracene and pentadecane had high reduction; however, the reduction is more significant (p<0.05) in soil inoculated with P. pulmonarius. Our results suggest that P. pulmonarius can be used to clean soils polluted with moderate level of petroleum products mixtureKey Word: Mycoremediation, petrol, diesel, spent engine oil, P. Pulmonarius, TP