Determining the tolerance level of Zea mays (maize) to a crude oil polluted agricultural soil

This research sought to investigate the tolerance level of Zea mays (maize) on a crude oil contaminated soil using indices of plant performance such as plant height, leaf area and fresh cob yield. In theexperiments described, conditions of a major spill were simulated by pouring different amounts of crude oil on experimental pots containing agricultural soil. Maize seeds were then grown amidst adequate fertilizer application and irrigation. The results of the study revealed that maize can survive soil contamination of about 21% (similar to 177 000 mg/kg) and still produce fresh cob yield of about 60% than on normal soil. There was a stimulated increase in fresh cob yield, than that obtained on normal soil at 12.5% soil contamination (similar to 112240 mg/kg). Hence, contaminant concentrations of 112 240 mg/kg and 177 000 mg/kg are identified as the ‘optimum yield limit’ and ‘lethal threshold’ respectively for maize growing on crude oil polluted soils. These results highlight the fact that, while concerted efforts should be made to remedy petroleum-contaminated agricultural soils, certain crops like maize can still produce beneficial yield in the presence of good soil management practices

Enhanced remediation of an oily sludge with saline water

This study investigates the potentials of saline (that is, brackish) water to enhance the remediation of an oily sludge, which was part of the waste stream from the improvement project of the Tank Farm at the Bonny Island in the Niger Delta region of Nigeria. Twice weekly, five separate laboratory-scale reactors (labeled A, B, C, D and O), each containing 2.0 × 10<sup>-2</sup> m<sup>3</sup> of the diluted sludge samples, received 170 g of liquid 20:10:10-NPK-fertilizer (corresponding to an application rate of approximately 4.3 kg-Nm<sup>-3</sup>, 2.1 kg-P-m<sup>-3</sup> and 2.1 kg-K-m<sup>-3</sup> of diluted sludge). On a weekly basis, control reactors A and B received 5.0 × 10-4 and 1.5 × 10<sup>-3</sup> m<sup>3</sup> of fresh water respectively while ‘treatment’ reactors C and D received 5.0 × 10<sup>-4</sup> and 1.5 × 10<sup>-3</sup> m<sup>3</sup> of saline water (containing 4.54 g/L of NaCl) respectively. Reactor O, which served as a counterfactual, was only rain-fed. Equal oxygen exposure levels, through regularly scheduled tilling, was maintained in all five reactors. After 12 weeks of treatment (that is, from May to August, 2007), sludge physicochemical characteristics showed distinct variations. The saline water treated-reactor D, had a 7-fold increment in bacterial population while the fresh water treated-reactor B, had an approximately 3-fold increment in bacterial population. The drop in the hydrocarbon content of the saline water-treated reactors ranged from 41.7 to 55.9% whereas in the fresh water-treated reactors, the hydrocarbon losses ranged from 17.3 to 25.0%. These results showed the possibility of enhanced biodegradation of oily sludge by hydrocarbon utilizing bacteria (Bacillus subtilis) at salinity (NaCl concentration) of 4.54 g/L.Key words: Bioremediation, biostimulation, oily sludge, saline water, Bacillus subtilis

Mycoremediation of polycyclic aromatic hydrocarbons (PAH)-contaminated oil-based drill-cuttings

Spent white-rot fungi (Pleurotus ostreatus) substrate has been used to biotreat Nigerian oil-based drill cuttings containing polycyclic aromatic hydrocarbons (PAHs) under laboratory conditions. The Latin square (LS) experimental design was adopted in which four options of different treatment levels were tested in 10 L plastic reactors containing fixed masses of the drill cuttings and fresh top-soil inoculated with varying masses of the spent P. ostreatus substrate. Each option was replicated three times and watered every 3 days under ambient conditions for a period of 56 days. Microcosm analysis with a series II model 5890 AGILENT Hp® GC-FID showed that, the PAHs in the drill cuttings were mainly composed of 2 to 5 fused rings with molecular-mass ranging from 128 to 278 g/mol, while the total initial PAHs concentration of the drill cuttings was 806.31 mg/kg. After 56 days of composting, the total amount of residual PAHs in the drill cuttings decreased to between 19.75 and 7.62%, while the overall degradation of PAHs increased to between 80.25 and 92.38% with increasing substrate addition. Individual PAH degradation ranged from 97.98% in acenaphthene to 100% in fluorene, phenanthrene and anthracene. Statistical analysis, using the 2-factor analysis of variance (ANOVA), showed that there were no significant differences (p < 0.05) in the biodegradation of the PAHs due to the substrate levels applied and remediation period, as well as a nonsignificant (p < 0.05) interaction between substrate levels applied and remediation period. These results showed that spent white-rot fungi (P. ostreatus) substrate may be suitable for biotreating PAH-contaminated Nigerian oil-based drill cuttings.Key words: Drill-cuttings, polycyclic aromatic hydrocarbons Pleurotus ostreatus, mycoremediation, compostin

Response of maize and cucumber intercrop to soil moisture control through irrigation and mulching during the dry season in Nigeria

Replicate field plots were used in experiments aimed at evaluating the yield potentials of maize and cucumber intercrop resulting from the control of soil moisture through irrigation and mulching, for aperiod of eleven weeks. Three irrigation depths, 2.5, 3.5 and 4.5 mm; and two mulch levels, zero mulch and 10 ton/ha of oil palm bunch refuse as mulch material were employed, while the third option involved the combination of the different levels of irrigation and mulching. These were used alongside fertilizer application. The pertinent growth and yield parameters were then determined. Results of the analysis indicated that there were no significant differences in growth parameters such as plantheight, vine length and days to 50% flowering across the treatment variants. Yield components such as total grain yield, total fresh cob yield and total fruit yield differed greatly across the treatmentoptions and also indicated significance at the 1% probability level. It was observed that cucumber total fruit yield was greater in the plots that received only mulching than the other plots. The results ofthe study highlight the position that the best crop yields would be obtained for maize and cucumber intercrop during the dry season, if farmers resort to optimum application levels while using thesynergy of irrigation and mulching to achieve a crop favorable soil moisture regime