Chlorinated organic compounds, such as polychlorinated biphenyls (PCBs), are a threat to both humans and the environment because of their toxicity, persistence, and capacity for long-range ...atmospheric transport. The concentrations of 28 PCB congeners, including 12 dioxin-like and seven indicator PCBs, were investigated in soils, and indoor and outdoor dusts from Port Harcourt city, Nigeria, in order to evaluate the characteristic distribution patterns in these media, their sources, and possible risk. The PCB concentrations varied from 4.59 to 116 ng g−1 for soils, and from 1.80 to 23.0 ng g−1 and 2.73 to 57.4 ng g−1 for indoor and outdoor dusts respectively. The sequence of PCB concentrations in these matrices was soil > outdoor dust > indoor dust. The composition of PCBs in these matrices indicated the prevalence of lower chlorinated PCBs in indoor and outdoor dusts, while the higher chlorinated congeners were dominant in soils. Di-PCBs were the predominant homologues in indoor dusts, while deca-PCBs were the most prevalent homologues in outdoor dusts and soils. The TEQ values of dioxin-like PCBs in 60 % of the soils, 100 % of the indoor dust, and 30 % of the outdoor dust were above the indicative value of 4 pg TEQ g−1 established by the Canadian authority. The hazard index (HI) values for exposure of adults and children to PCBs in these media were mostly greater than one, while the total cancer risk (TCR) values exceeded the acceptable risk value of 10−6, which indicate probable non-carcinogenic and carcinogenic risks resulting from exposure to PCBs in these media. Source analysis for PCBs in these matrices shows that they originated from diverse sources.
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•PCB-contaminated dusts and soils from Port Harcourt city were investigated.•PCB concentrations in soils were higher than those of outdoor and indoor dusts.•Tri-, penta-, and deca-PCBs were the dominant homologues in these matrices.•Exposure to PCBs in these matrices poses a risk to the ecosystem and humans.•PCBs in these matrices originated from diverse sources.
The concentrations, sources, and risk of twenty organochlorine pesticides (OCPs) in soils and dusts from a typical urban setting in the Niger Delta of Nigeria were examined. The Σ20 OCP ...concentrations (ng g−1) varied from 4.49 to 150 with an average value of 32.6 for soil, 4.67 to 21.5 with an average of 11.7 for indoor dust, and 1.6 to 96.7 with an average value of 23.5 for outdoor dust. The Σ20 OCP concentrations in these media were in the order: soil > outdoor dust > indoor dust, which was in contrast with the order of the detection frequency, i.e., indoor dust (95 to 100 %) > soil (60 to 90 %) > outdoor dust (30 to 80 %). The concentrations of the different OCP classes in these media followed the order: aldrin + dieldrin + endrin and its isomers (Drins) > chlordanes > dichlorodiphenyltrichloroethane (DDTs) > hexachlorocyclohexane (HCHs) > endosulfans for outdoor dust and soil, while that of the indoor dust followed the order: Drins > chlordanes > endosulfans > DDTs > HCHs. The cancer risk values for human exposure to OCPs in these sites exceeded 10−6 which indicates possible carcinogenic risks. The sources of OCPs in these media reflected both past use and recent inputs.
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•OCPs in dust and soils from Port Harcourt city were investigated.•OCP concentrations in soils were higher than those of outdoor and indoor dusts.•Drins and chlordanes were the dominant OCPs in these media.•Exposure to OCPs in these media pose a risk to humans.•OCPs in these media originated from predominantly aged used sources.
Polycyclic aromatic hydrocarbons (PAHs) are a group of semi-volatile and persistent organic compounds considered priority pollutants because of their pervasive nature and high toxicity to the ...ecosystem and humans. Therefore, this study aimed to evaluate the PAH concentrations in dust and soils around informal trade sites (ITS) in Nigeria to determine the level of risk, sources, and significance of these activities to the PAH load of the environment. The 16 US EPA PAHs in dust and soils from ITS were determined by gas chromatography-mass spectrometry (GC-MS). The PAH concentrations in dust from these informal trade sites varied from 120 to 8790, 56 to 4780, and 102–1090 μg kg−1 for automobile mechanic workshops (AMW), car dismantling (CDS), and material recovery sites (MRS), respectively, whereas those of soils ranged from 3000 to 95,500, 554 to 14,700, and 966–25,200 μg kg−1 for AMW, CDS, and MRS respectively. The PAH profiles indicated that 3- to 5-ring PAHs were prominent in dust and soils around the ITS. The concentrations of the US EPA 16 PAHs in dust and soils from these ITS showed no correlation with organic matter, while the concentrations of PAH homologues in soils of these ITS showed no correlation with those of dust. Incremental lifetime cancer risk (ILCR) values in the magnitude of 10−4 to 101 were obtained for adult and childhood exposure to PAHs in dust and soils from these ITS. Exposure to PAHs in dust from these ITS gives rise to less risk than for soils. The results indicated that automobile mechanic workshops contribute more PAHs to the environment than car dismantling and material recovery activities. The source analysis showed that the PAH contamination of these sites arises from burning of biomass, plastic materials, and oils, and emissions from vehicles.
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•Dust and soils around informal trade sites (ITS) are contaminated with PAHs.•Activities of these ITS are potent contributors of PAHs to the environment.•3- to 5-ring PAHs were the dominant species in soils and dust from the ITS.•PAHs in these matrices are of potential risk to the ecosystem and human health.•PAH profiles in these matrices reflect dominance of pyrogenic sources.
In this study, we evaluated the concentrations, composition, sources, and potential risks of polycyclic aromatic hydrocarbons (PAHs) in soils, and indoor and outdoor dust from Port Harcourt city in ...Nigeria. Gas chromatography-mass spectrometry (GC-MS) was used for the detection and quantification of PAH species in the samples. The concentrations of the US EPA 16 PAHs plus 2-methyl-naphthalene (∑17 PAHs) in soils, and indoor and outdoor dust from Port Harcourt city ranged from 240 to 38 400, 276 to 9130 and 44 to 13 200 μg kg
−1
(dry weight, d.w.) respectively. The PAH concentrations in these matrices followed the sequence: soil > indoor dust > outdoor dust. The composition of PAHs in soils and dust (indoor and outdoor) showed remarkable differences with prominence of 3- and 5-ring PAHs. The estimated carcinogenic risk to the residents arising from exposure to these concentrations of PAHs in soils, and indoor and outdoor dust from Port Harcourt was above the acceptable target cancer risk value of 10
−6
. We concluded that these sites require clean-up, remedial actions and implementation of stringent pollution control measures with the intention of reducing the undesirable impacts of PAHs on both the ecosystem and humans.
This study evaluated the concentrations, composition, sources, and potential risks of polycyclic aromatic hydrocarbons (PAHs) in soils, and indoor and outdoor dust from Port Harcourt city in Nigeria.
For effective and efficient performance of wind turbines, components and systems should perform at a low risk with minimal downtime. To establish the impacts of wind turbine components maintenance on ...downtime and failure risks, a six state Markov model was developed using the failure rates and downtimes information. The transition and maintenance rates at the lifecycle phases (introduction, maturity, ageing and terminal) together with those at maintenance and failure phases were determined using a calibrated survivability index whilst the transition rate probabilities were used in modelling the performance and failure risks probabilities at different maintenance intervals. The model was tested using failure rates and downtime information of wind turbine components obtained from literature and the results indicates that the model has practical applications for managing wind turbines.
•Established the effects of maintenance on wind turbine components.•Used six state transition matrix to estimate the risk at components lifecycle phases.•Determined failure risk at different lifecycle phases of wind turbine components.•Downtime variability of different wind turbine components were estimated.
•Fatigue stress starts at corroded points and grow due to cyclic loading.•Heat affected zones on pipelines are susceptible to hydrogen induced cracking.•Hydrodynamic characteristics of flow in a ...pipeline enhances corrosion process.•Pipelines are more susceptible to stress corrosion cracking at low potentials.
Pipeline corrosion is a major challenge facing many oil and gas industries today because of the enormous downtime associated with corrosion related failures. Fatigue stress initiation in pipelines has been attributed to corrosion defects whose growth is enhanced by cyclic loading caused by the operating pressure of the transported fluids. This work reviews the concept of oil and gas transmission pipeline failures in corrosive environment by highlighting the corrosion mechanisms, dominant stress corrosion cracking trends, hydrogen induced cracking and predominant models for burst pressure estimation. Fatigue stress failure trends of corroding pipelines were also explained whilst describing some pipeline manufacturing processes that increases the susceptibility to fatigue stress failure. Optimization framework for pipeline integrity assurance against corrosion fatigue failures was also shown to incorporate different steps that includes – strategic policy initiation, policy implementation, information analysis and reviews and implementation actions.
For effective integrity management, the reliabilities at times of exposure of pipelines to corrosive environment need to be understood. This paper described the procedure for using Markov modelling ...and Monte Carlo simulation to determine the reliabilities of internally corroded pipelines. The corrosion wastage of the pipeline was classified with Pipeline Corrosivity Indexes (PCIs), which were expressed as functions of retained pipe-wall thickness at exposure times. The model was tested on X52 grade pipeline that was monitored by Magnetic Flux Leakage (MFL) In-Line-Inspection (ILI) technique and the failure probabilities were determined for different failure scenarios such as small leakage, bursting and rupture. It was observed that, as the time of exposure of the pipeline to corrosive condition increased, there was a slight variation of the reliability of the pipeline that failed by bursting and rupture. The result also indicated a very high likelihood of small leakage of the pipeline than bursting and rupture. Since the failure probability of the corroded pipeline increases with increased time of exposure, it is expected that this model will be viability for the integrity management of internally corroded pipelines.
•Modelled internal pipeline corrosion using Markov and Monte Carlo•Estimated corrosion wastage rate using Weibull probability function•Used Pipeline Corrosivity Index to describe pipe-wall loss with time•Reliability was determined with limit state function•Failure probability increased with increased time of pipeline exposure
To estimate the internal pit depth growth and reliability of aged oil and gas pipelines, a Monte Carlo simulation approach was adopted. The average maximum pit depths of corroded pipelines were ...correlated with the operating parameters-temperature, CO sub( 2) partial pressure, pH, flow rate, sulfate ion concentration, chloride ion concentration, water cut, and wall shear stress via a multivariate regression analysis. Poisson square wave model was used to predict the time lapse of the pit depth growth using the statistical best fit of the maximum pit depth and operating parameters as boundary conditions. Weibull probability function was used to determine the failure intensity and survivability of the pipelines for different distribution types, whereas inspection data from a magnetic flux leakage in-line inspected transmission pipeline were used to test the application of the model. The future pit depth distribution, survivability, and failure rate of this transmission pipeline were also determined, with the result showing that the model is vital for future internal pit depth growth and reliability estimation from single field inspection data.
This paper develops a framework for sustainable asset integrity management (AIM) with regards to renewable energy generation plants. The authors conclude that increased downtime, low energy output, ...high cost of maintenance and repair operations, which are attributable to poor assets integrity management, can be mitigated with sustainable AIM. The enhancement of economic and efficient energy generation in renewable energy plants, therefore, involves a structured procedure that combines socio-economic and environmental demands in decision supports for facilities management. This can be achieved utilizing a function interfaced organizational model and techniques that include mitigation, prevention and regulatory programmes. Environmental conscious planning, review and task execution in AIM are vital to health, safety and environmental conservation whilst improved asset lifecycle performance can be reached through competence, compliance, control, communication and co-operation of management and personnel. In conclusion, proper coordination of AIM through an accurate understanding of the stakeholder demands results in efficient renewable energy generation.
To enhance the performance of any facility, reduce cost and failure probability involves proper inspection and repair decisions. To be able to establish the cost of repair and inspection of corroded ...pipelines at different stages of the corrosion defect depth growth, Markov modelling technique was adopted. This model formulated an inspection and repair technique, which has the potentials of aiding policy makers in maintenance management of internally corroded pipelines. The transition states were determined using the Remaining Useful Life (RUL) of the pipelines whilst Weibull distribution was used for calculating the corrosion wastage rates at the lifecycle transition phases. Monte Carlo simulation and degradation models were applied for determining future corrosion defect depth growth, in a bid to establish periodic inspection and repair procedures and their costs. Data from an onshore pipeline inspected with Magnetic Flux Leakage (MFL) in-Line-Inspection (ILI) technique was used to test the validity of the model. The results obtained indicate that the model has practical applications for inspection and repairs of aged-internally corroded pipelines.
•Modelled inspection and repair of corroded pipeline using Markov process•Expressed the transition states as a function of retained pipe-wall thickness•Inspection and repair on the pipeline depended on the corroded depth.•Monte Carlo simulation was used to predict the time of corrosion wastage.
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