Effect of detergent and sawdust addition on hydrocarbon reduction and growth of Abelmoschus esculentus L (Okra) in a petroleum-contaminated soil

A study to investigate the effect of sawdust and detergent on hydrocarbon reduction and the growth of okra (Abelmoschus esculentus L.) in petroleum polluted soil was carried out. The study was conducted at the Centre for Ecological Studies, University of Port Harcourt. Bonny light crude (300 ml) was used to pollute 10 kg soil. Detergent (20 g), sawdust (200 g) and sawdust: detergent (200 g: 20 g) were used as the amendment materials alongside a control (pollution but un-remediated) arranged in a completely randomized design of 12 replications. After 30 days post-amendment, 3 seeds of okra (var: V35-45 days) were grown in each treatment pot for 6 weeks. Soil Total Hydrocarbon Content (THC) and okra growth performance (shoot length, leaf number, root length, total fresh weight, dry weight, leaf area and leaf area ratio) were analyzed. Results showed significant (p=0.05) reductions in THC of 44.23%, 26.5%, 70.80% and 10.79%, in detergent (20 g), sawdust (200 g), sawdust (200 g) + detergent (20 g) and control, respectively. Improved growth performances of okra were observed in the amended soil as compared to the control. Okra growth performance was in the order of: 200 g sawdust + 20 g detergent combination > 200 g sawdust > 20 g detergent. This implies that these two materials are good bio-stimulation materials especially when used in combined form for THC reduction and growth of okra.Keywords: Abelmoschus esculentus L., contamination, crude oil, sawdust, total hydrocarbon conten

Evaluation of Heavy Metal Levels and the Distribution of Rhizophora racemosa and Nypa fruticans in the Niger Delta Mangrove Forest, Nigeria

Plants react differently to pollutant levels in their substratum, and pollutant levels either positively or negatively influence their distribution. In this study, soil levels of Cr, Ni, Cd, Pb and Zn on the distribution of Rhizophora racemosa and Nypa fruticans was investigated. Soil samples were collected randomly closer to the roots at growth sites and the non-growth sites of the study plants at four selected stations in the study area and analyzed using standard laboratory methods. Findings showed that N. fruticans grew well in soils with high levels of soil Cr, Pb and Zn over R. racemosa whose growth was associated with soils with lower levels of the referenced metals and the above metals influence their distribution. The above observation was attributed to the high tolerance level of N. fruticans to Cr, Pb and Zn toxicity above R. racemosa. It is thus concluded that R. racemosa and N. fruticans distribution are influenced by the levels of soil heavy metals. Keywords: Pollutant levels, Distribution, Mangrove

Evaluation of the efficacy of soil flushing remediation method on crude oil-spilled mangrove sediment at Bodo Creek, Gokana, Nigeria

The efficacy of soil flushing remediation method of a crude oil spilled mangrove sediment at Bodo creek, Bodo, Nigeria was evaluated. Field observation revealed that after soil flushing remediation operation of the Bodo crude oil-spilled site in 2018 by Shell Petroleum Development Company of Nigeria, no post-remediation assessment was carried out to determine the effectiveness of the technique as a remediation strategy. This study was carried out to ascertain the effectiveness of soil flushing remediation method for decontamination of hydrocarbon-spilled mangrove environment. Sediment samples were collected from 3 stations within the creek which were non-remediated crude oil-polluted station, soil flushing remediated station and non-polluted station, at depths of 0 – 15 cm and analysed for sediment temperature, pH, conductivity, Total Petroleum Hydrocarbon (TPH), Total Hydrocarbon Content (THC) and microbial properties. Results showed significant decrease in TPH and THC (1241.71 mg/kg and 1755.45 mg/kg, respectively) in the soil flushing remediated station when compared with non-remediated polluted station (1792.93 mg/kg and 28261.5 mg/kg, respectively). Despite the significant decrease in THC and TPH in the soil flushing station, the values were still above environmentally permissible limits. This implies that other remediation techniques should be adopted after the soil flushing approach