Petroleum Hydrocarbons Contamination of Sediments and Accumulation in Tympanotonus fuscatus var. radula from the Qua Iboe Mangrove Ecosystem, Nigeria

The pollution of coastal ecosystems as a result of petroleum-related activities is increasing, and the literature on occurrence, levels and seasonal dynamics of petroleum hydrocarbons in sediments and biota from the impacted areas of the Niger Delta, Nigeria, is practically scanty. This study was set out to provide information on the status of contamination by petroleum hydrocarbons in Tympanotonus fuscatus var. radula and sediments from Qua Iboe Estuary, Nigeria. Analyses for total petroleum hydrocarbons (TPHs) were performed on Tympanotonus fuscatus var. radula and sediment extracts using gas chromatograph with flame ionization detector (GC-FID). Seventy-two samples each of mangrove epipellic (intertidal) and benthic (subtidal) sediments, and T. fuscatus var. radula were analysed monthly between June 2003 and February 2004, covering peak periods of the wet and dry seasons. Results revealed that the TPHs level in sediments and T. fuscatus were highly variable. It ranged between 18.01 ± 0.04 and 210.23 ± 1.18 μg g–1 dry wt of epipellic sediment, 5.00 ± 0.82 and 232.00 ± 3.23 μg g–1 dry wt of benthic sediment and 9.40 ± 1.0 and 23.27 ± 1.0 μg g–1 dry wt of T. fuscatus. Summary continuous descriptives and correlation analyses revealed that TPH levels of the epipellic and benthic sediments showed a significant relation (r = 0.54, CI = 0.18–0.78), and correlated with levels in T. fuscatus. The overall levels of TPHs in the Qua Iboe Estuary when compared to similar ecosystems with substantial industrial and domestic coastal activities worldwide, revealed a moderate to high level of mineral hydrocarbon pollutio

Mercury accumulation in fishes from tropical aquatic ecosystems in the Niger Delta, Nigeria

Fishes are important biomarkers of trace elements in aquatic ecosystems, and are used to evaluate the status of water pollution by mercury in tropical aquatic ecosystems in Nigeria. Common fishes, Chrysichthys nigrodigitatus,Brycinus nurse, Hemichromis fasciatus, Lutianus ava, Oreochromis nilotica, Pomadasys jubelini, Stellifer stellifer and Tilapia guineensis were analysed for Hg accumulation using the cold vapour atomic absorption spectrophotometry technique. The results showed that Hg concentration in P. jubelini was relatively the highest, with a mean concentration of 0.063 ± 0.03 mg kg–1. Other concentration values were 0.044 ± 0.031 mg kg–1 for O. nilotica, 0.026 ± 0.013 mg kg–1 for B. nurse, 0.034 ± 0.034 mg kg–1 for H. fasciatus, 0.023 ± 0.020 mg kg–1 for C. nigrodigitatus and 0.33 ± 0.016 mg kg–1 for L. ava. Concentrations of Hg accumulated by the fishes were low and within internationally accepted limit, not likely to cause mercury poisoning. Because of the high Hg accumulating potential of P. jubelini, it is recommended as a biomarker for assessment of Hg toxicity in a tropical aquatic environment

Microbial population dynamics as a function of sediment salinity gradients in the Qua Iboe Estuary mangrove swamp (Nigeria).

In this investigation the extent to which sediment salinity gradients can be used to predict the sensitivity of microbial populations in mangrove ecosystem was investigated. The microbial groups monitored were heterotrophic bacteria, coliform bacteria, actinomycetes, fungi and yeasts. Pearson's Product-Moment Correlation (r) analyses were done on Log10-transformed estimates of population densities. The values obtained from the intertidal (epipellic) and subtidal (benthic) sediments were less than the critical value of 0.707 (n=8, p=0.05). This indicates that salinity was less closely related to the microbial population densities. A positive but insignificant relationship was found for fungi (r=0.03) in intertidal sediment. The total heterotrophic bacteria (r=-0.69), coliforms (r=-0.54), actinomycetes (r=-0.43) and yeasts (r=-0.56) were negatively affected by salinity in epipellic sediment. But in the benthic sediment, total heterotrophic bacteria (r=0.55) and unexpectedly, the fungi (r=0.58) and actinomycetes (r=0.29) exhibited positive but insignificant correlations while coliform and yeast counts in the benthic sediments were negatively influenced by salinity. However the coefficient of determinations (R2) revealed that total heterotrophic bacteria (48.06%) and yeasts (31.18%) were more extensively distributed in the intertidal sediments than coliforms. (29.38%,actinomycetes (18.68%) and fungi (0.09%). In contrast, the fungi (33.48%) demonstrated a wider distribution in benthic sediment. This may be ascribed to their existence, mostly as dormant, but culturable spores in the anoxic bottom sediment. The weak relationship exhibited by coliforms further confirms their usefulness as indicator of faecal contamination in estuarine ecosystem

Application of correlation analysis in assessment of relationships between mineral hydrocarbon levels and hydrocarbonoclastic bacteria count in tropical mangrove estuarine sediments

Pearson’s Product-Moment correlation analysis of the relationships between total hydrocarbon content (THC) and hydrocarbon utilizing bacteria population (HUB) in mangrove sediments and overlying water of the Qua Iboe Estuary, Nigeria was carried out. The results show that there was in general a close relationship between the two variables, but also a large amount of variation not explained by the analysis. The strongest positive relationships (p = 0.05) were found for THC in epipellic (intertidal) sediment and water (r = 0.65) while the relationship between THC in benthic (subtidal) sediment and water (r = 0.028) was weak, and positively insignificant (p = 0.05). A correlation of HUB densities on THC in benthic sediment was strong and positive (r = 0.91) but characterized by high HUB/HET ratios. That is, the strength of the relationship with respect to the oil degrading potentials of the bacterial was fairly low. In contrast, the relationships between the two variables in epipellic sediment (r = 0.66) was positively significant (p = 0.05) but with a substantial presence of heterotrophic bacteria. This implies that a quick-analysis of hydrocarbon content in epipellic sediment in relation to hydrocarbon utilizing bacteria densities following an oil spill is reliable. However, such analysis on benthic sediment may not be reliable in estuarine environment with chronic exposure to crude oil pollution. This is despite the wide distribution of HUB (82.4% in benthic sediment, 43.1% in epipellic sediment, and 33.3% in surface water) in the ecosystem as revealed by the coefficient of determinations (R2) values

Petroleum hydrocarbons and limiting nutrients in Macura reptantia, Procambarus clarkii and benthic sediment from Qua Iboe Estuary, Nigeria

The levels of total petroleum hydrocarbons in two commonly consumed benthopelagic shellfishes, Macura reptantia and Procambarus clarkii, harvested from benthic sediment of Qua Iboe Estuary were determined using a gas chromatography with flame-ionization detector. Seventy-two (72) samples each of benthic sediment and the shellfishes were collected monthly between June 2003 and February 2004 covering the peak periods of the wet and dry seasons. Concentrations of hydrocarbons were highly variable and ranged between 5.00 and 232.00 μg/g dry weight of benthic sediment, 3.05 and 11.30 μg/g dry weight of M. reptantia, 1.62 and 9.00 μg/g dry weight of P. clarkii. Pearson’s correlation analysis of total hydrocarbon concentrations in subtidal sediments with levels in the fauna species yielded positive significant (P < 0.05) correlations in M. reptantia (r = 0.737) and P. clarkii (r = 0.924). This is indicative of a long term and chronic accumulation of hydrocarbons in the estuarine ecosystem, reflecting the potential for exposure of the resident biota and the risk to human health

Petroleum Hydrocarbons Accumulation Potential of Shellfishes from Littoral Waters of the Bight of Bonny, Niger Delta, Nigeria.

Total hydrocarbons concentration in four commercially available shellfishes (Ocypoda africanus, Macura reptantia, Procambarus clarkii and Penaeus notialis) from coastal waters of the Niger Delta region of Nigeria were investigated between June 2003 and February 2004 using standard methods. Levels of total hydrocarbons varied significantly depending on biota species, feeding habit and season. The seasonal mean concentrations reported were: 3.98±0.69, 7.95±1.18, 2.24±0.39 and 5.85±0.57 μg g -1 dry weight for M. reptantia, O. africanus, P. clarkii and P. notialis respectively during the wet season. Enhanced concentrations recorded during the dry season were 7.81±2.32, 11.59±2.63, 6.16±2.12 and 9.69±1.90 μg g-1 dry weight for M. reptantia, O. africanus, P. clarkii and P. notialis, respectively. The results obtained indicated seasonal variations which might have been associated with an incidental crude oil spill recorded during the investigation. In general, O. africanus showed higher levels of total hydrocarbons than other species investigated. However, biota species demonstrated hydrocarbon bioaccumulation potential. Regression between the monthly concentrations of total hydrocarbons in each of the biospecimens with the levels in the surface water and sediments indicated statistically significant (p&lt;0.05) relationships. Moreover, comparison of the seasonal mean concentrations using paired sample t-test at 95% confidence level indicated that the concentrations between the dry and wet seasons were statistically significant

Distribution and risk assessment of trace metals in Leptodius exarata, surface water and sediments from Douglas Creek, Qua Iboe estuary

Five trace metals in Leptodius exarata, epipellic sediments and surface water from an intertidal ecosystem in Niger Delta (Nigeria) were investigated to evaluate their spatial distribution, degree of contamination, ecological and health risks. Results show Cd (cadmium), Cr (chromium), Ni (nickel), Pb (lead) and Zn (zinc) concentrations in sediment ranged between 0.550 – 1.142, 9.57 – 15.95, 9.15 – 13.96, 2.00 – 8.90 and 91.5 – 121.6 mg/kg dw, respectively; while L. exarata tissue metal content vary from 0.162 – 0.931, 3.81 – 8.62, 4.45 – 17.15, 1.90 – 7.35, and 125.55 – 269.75 mg/kg, dw, respectively. The bioconcentration factor ranking for trace metals followed the sequence Zn>Ni>Pb >Cr>Cd. High biota to sediment accumulation factor (BSAF) in L. exarata reveals a sentinel metal bioindicator. Sediments from most sites were uncontaminated to moderately contaminated (geoaccumulation, Igeo > 0) with Cd and Zn associated with anthropogenic intrusions. Low mean-ERM (effect range-median) and mean-PEL (probable effect level) quotients of sediments are observed, indicating low–medium degree of contamination with 30% and 21% probability of being toxic. The multi-metal potential ecological risk index (RI) for the intertidal ecosystem indicates low–moderate risk. Health risks associated with crabs (L. exarata) consumption are significant in children than adults

Microalgae biodiversity and biomass status in Qua Iboe Estuary mangrove swamp, Nigeria

Microalgae composition,abundance,diversity and biomass of the Qua Iboe Estuary mangrove swamp were studied. The results revealed the rich assemblage of the brackish ecosystem. Six major taxanomic classes were encountered. These were the Bacillariophyceae, Cyanophyceae, Chlorophyceae, Chrysophyceae, Euglenophyceae and Phaeophyceae. Their composition, abundance and diversity exhibits strong seasonal variation. Variations between pelagic and sedimentary habitats were also noticed. The diatoms (Bacillariophyceae) dominated the habitats. Actinoptychus undalatus, Navicula radiosa and Amphora ovalis co-dominated the pelagic water column; while the epipellic (intertidal) and benthic (subtidal) sediments were co-dominated by A. ovalis and Actinoptychus undulatus. Analyses of the Shannon’s index of general diversity (H1), McArthur-Terborgh species equitability index (E) and Simpson’s index of dominance (D) of the microalgae communities revealed that A. ovalis with a mean H 1 -value of 0.25, E-value of 0.08 and D-value of 0.05 was the most prevalent genus in the mangrove ecosystem despite its uneven distribution. The densities of the microalgae communities corresponded with their biomass statuses and were seriously impacted by oil spillage. This forms the basis of concern because the estuary is associated with a high probability of major oil pollution with serious consequences for ecological stability and fisheries

Prediction and Performance Investigation of Polyurethane Foam as Thermal Insulation Material for Roofing Sheet Using Artificial Neural Network

The prediction and application of Polyurethane Foam in developing roofing sheets cannot be over-emphasized when considering the environmental changes caused by thermal radiation. This paper presents an artificial neural network (ANN) application to model and predict the indoor temperature resistance of polyurethane (PU) roofing in residential buildings. The study employed a data logger to measure the indoor and outdoor temperatures for three simulation environments (i.e., morning, afternoon, and evening) for two hours each. Furthermore, the authors employed the Levenberg- Marquardt algorithm to transform and predict the indoor temperature obtained in the residential building's polyurethane roofing house. The result shows that the PU roofing system could absorb the heat and reduce the house model's temperature with 6.9% in the morning, afternoon 15.8%, and 6.8% in the evening compared with the temperature outdoor environment. The ANN was also able to train, test, and validate the experimental temperature results with 92.86%, 93.92%, and 95%, respectively. The mean square error and a testing error occurs at 0.1707 and 0.1689. Therefore, this study concluded that the ANN's application in predicting the thermal insulation material such as the PU roofing system is highly efficient. And will increase the manufacturer's performance evaluation. It has also created significant awareness of the community in employing the PU roofing system for residential buildings, which will reduce the rate of energy consumption in buildings

Occurrence and distribution of polycyclic aromatic hydrocarbons in surface microlayer and subsurface seawater of Lagos Lagoon, Nigeria

Polycyclic aromatic hydrocarbons (PAHs) in surface microlayer (SML) and subsurface water (SSW) of Lagos Lagoon were investigated using gas chromatography-electron capture detector (GC-ECD) technique to ascertain their occurrence and spatial distribution, origin, enrichment, and carcinogenicity. Total PAH (ΣPAH) concentrations ranged from 9.10 to 16.20 μg L−1 in the SML and 8.90 to 13.30 μg L−1 in the SSW. ΣPAH concentrations were relatively higher in the SML than the underlying SSW samples. The enrichment factors (EFs) of ΣPAHs ranged from 0.76 to 1.74 while the EFs of the individual PAHs varied from 0.50 to 2.09. In general, the EFs values calculated in this study were consistent or slightly less than the EFs reported for similar coastal seawater ecosystems. A correlation between the EFs of fluoranthene and pyrene indicated a positive significant value (R = 0.9828, p < 0.0001, n = 6). Source analyses using the phenanthrene/anthracene and fluoranthene/pyrene ratios indicated the dominance of petrogenic-derived PAHs. Furthermore, enhanced concentrations of BaP (strong carcinogenicity) in SML and SSW samples, which resulted in higher EFs, could pose serious ecological and human health risk