SOURCE:

Faculty: Physical Sciences
Department: Pure And Industrial Chemistry

CONTRIBUTORS:

Okafor, U. W
Okoye, P.A.C

ABSTRACT:

Lead polluted soils have been assessed and remediated by the use of eight(8) different non edible flowering plants such as Hibiscus rosasinensis, Ixora coccinea, Euphobia milivarspendens, Ficus benjamina, Ageratum houstonianum, Gaillardiax grandiflora, Aloe barbadensis and Duranta erecta. Then one hundred and sixty (160) soil samples were collected from different directions around the manufacturing site at depths of top soil, 5 cm, 10 cm, 15 cm and 20 cm. This was done twice in both rainy and dry seasons. The soil samples were collected at intervals of 5meters. The soil samples collected were digested and analysed in triplicates for lead using Atomic Absorption Spectrophotometer (Buck scientific, AA220FS). The same triplicates analyses were made with pH meter (Searchtech, PHS- 7010) to check the level of acidity of the soil. The control sample was collected from a distance of about 500 m away from the industrial location. Eight most common non-edible flowering plants were planted on these polluted soil samples to monitor the level / degree of absorption of the lead by these plants. After a period of 3 months, these plants were harvested; air dried, digested and analyzed using AAS for the residual heavy metal concentration. Analysis of Variance (ANOVA) was used to interpret the data obtained. The results indicated an average range of lead concentration (in mg/kg soil sample) of 1.281±0.76 to 0.703±0.87 from June to September and 0.945±0.54 to 1.141±0.44 from February to April. The results of the pH determination showed that the soil was slightly acidic with a pH range of 5.5-5.7. The results of lead uptake by flowering plants indicated that Gaillardiax grandiflora and Aloe barbadensis died after 3 weeks of planting attributable to lead poisoning. Hibiscus rosasinensis and Ageratum houstonianum absorbed higher quantity of lead in the root (0.148mg/kg and 0.102mg/kg respectively) than the leaves (0.04mg/kg and 0.03 mg/kg). Ixora coccinea absorbed more lead in the leaves (0.09mg/kg) than in the root (0.03mg/kg), nonetheless in negligible amounts. Euphorbia milivarspendens, Ficus benjamina and Duranta erecta absorbed quantities of lead (0.98mg/kg, 0.2mg/kg, and 0.28mg/kg) respectively in the leaves than in the root (0.2mg/kg, 0.08mg/kg and 0.062mg/kg).The order of phytoremediation by the non-edible plants studied was established thus: E. milivarspendens > D. erecta > F. Benjamina > I. coccinea > H. rosasinensis > A. houstonianum > G. grandiflora and A. Barbadensis. This study has shown that the soils around the battery site were polluted with lead. Also the plants, F. benjamina, D. erecta and E. milivarspendens absorbed more than 60% of lead pollutants in the soil while I. coccinea absorbed less than 10% of lead. H. rosasinensis and A. houstonianum absorbed more lead pollutants in the root than in the leaves; hence they are not good for phytoremediation. Consequently, F. benjamina, D. erecta and E. milivarspendens could be used to remediate lead polluted soils. They also reduced the lead concentration below the Environmental Protection Agency (EPA) limit of 0.4mg/kg.