Search results

The purpose of this work is to provide theoretical guidance and experimental analysis for optimized cathodic protection (CP) design of low alloy steel in deep water environments.

In the present study, the CP criteria of 10Ni5CrMoV low alloy steel were investigated in a simulated deep water environment (350 m) regarding the theoretical protection potential and measured protection potential. The influences of hydrostatic pressure (HP) and temperature were also discussed in detail. The theoretical protection potential was analyzed with the Nernst equation, and the measured minimum protection potential was derived by extrapolating the Tafel portion of anodic polarization curves.

The results indicate that the minimum protection potential of low alloy steel shifts to a positive value in a deep-ocean environment. This can be attributed to the combined effects of HP and the temperature. Moreover, the temperature has a stronger influence compared with HP. The results suggest that the CP potential criteria used in shallow water are still applicable in the deep ocean, which is further confirmed through the SEM and x-ray diffraction analysis of the corrosion products resulted from the potentiostatic cathodic polarization experiments at −0.85 V_CSE.

In recent decades, successful applications of CP for long-term corrosion protection of the steel components applied at a subsea level have enabled the offshore industry to develop reliable and optimized CP systems for shallow water. However, differences in the seawater environment at greater depths have raised concerns regarding the applicability of the existing CP design for deeper water environments. Hence, this research focuses on the CP criteria of low alloy steel in simulated deep water environment concerning the theoretical protection potential and measured protection potential. The influences of HP and temperature were also discussed.

The purpose of this paper is to examine the presence of geogenic contaminants in groundwater from shallow aquifers of the crystalline basement complex rocks of Ibadan south-western, Nigeria.

A total of 30 drinking water samples, (six samples each from the five major lithologic formations of the study area) were collected from hand dug wells during the rainy season. Atomic absorption spectrophotometry was used to determine concentrations of arsenic, iron and fluoride in drinking water samples and also concentrations of other chemical parameters that could affect the concentrations of the geogenic contaminants including pH, Ca, Mg, Na and SO₄2−. Descriptive statistics, multiple correlation and analysis of variance were used to examine the relationship between the geogenic contaminants and concentration of other chemical parameters while inverse distance weighting was used to produce risk maps.

The results showed Arsenic concentration exceeding the WHO recommended concentration for drinking water in all the samples within the area. Samples from 16.6 per cent of the wells exceeded the recommended limit for fluoride while iron was present in most of the samples within acceptable limits. The study also revealed no significant difference in concentration of contaminants between the geologic formations.

Geogenic contamination has been scarcely studied in Nigeria. This research, therefore, is a paradigm shift in the study of groundwater contamination which had been mainly focused on anthropogenic contaminants. The outcome of this research will engender policy makers and researchers to pay more attention to geogenic contamination than anthropogenic contaminants in Nigeria.

This paper aims to study the Gramian solutions and solitonic interactions of a (2 + 1)-dimensional Broer–Kaup–Kupershmidt (BKK) system, which models the nonlinear and dispersive long gravity waves traveling along two horizontal directions in the shallow water of uniform depth.

Pfaffian technique is used to construct the Gramian solutions of the (2 + 1)-dimensional BKK system. Asymptotic analysis is applied on the two-soliton solutions to study the interaction properties.

N-soliton solutions in the Gramian with a real function ζ(y) of the (2 + 1)-dimensional BKK system are constructed and proved, where N is a positive integer and y is the scaled space variable. Conditions of elastic and inelastic interactions between the two solitons are revealed asymptotically. For the three and four solitons, elastic, inelastic interactions and soliton resonances are discussed graphically. Effect of the wave numbers, initial phases and ζ(y) on the solitonic interactions is also studied.

Shallow water waves are studied for the applications in environmental engineering and hydraulic engineering. This paper studies the shallow water waves through the Gramian solutions of a (2 + 1)-dimensional BKK system and provides some phenomena that have not been studied.

Seasonal studies of water quality in partially protected shallow wells in Akure, Nigeria were carried out. The well waters were of high chemical quality, but higher values of parameters in the early rainy season than in the dry season indicate runoff water inflitration. Consequently, the waters show slight turbidity for one to two hours after rainfall due to settleable solids, a factor which renders the wells liable to chemical and bacterial contamination from surface sources. There is therefore a need for a design of drinking water wells in Akure to include making the wells deeper, at least 6 metres deep, and incorporating watertight lining of the upper part.

A semi‐implicit semi‐Lagrangian mixed finite‐difference finite‐volume model for the shallow water equations on a rotating sphere is considered. The main features of the model are the finite‐volume approach for the continuity equation and the vectorial treatment of the momentum equation. Pressure and Coriolis terms in the momentum equation and velocity in the continuity equation are treated semi‐implicitly. Discretization of this model led to the introducion, in a previous paper, of a splitting technique which highly reduces the computational effort for the numerical solution. In this paper we solve the full set of equations, without splitting, introducing an ad hoc algorithm. A von Neumann stability analysis of this scheme is performed to establish the unconditional stability of the new proposed method. Finally, we compare the efficiency of the two approaches by numerical experiments on a standard test problem. Results show that, due to the devised algorithm, the solution of the full system of equations is much more accurate while slightly increasing the computational cost.

The contamination of groundwater by natural arsenic is currently a worldwide epidemic. Arsenic-contaminated groundwater has been reported in Argentina, Chile, Mexico, China, Hungary, West Bengal in India, Bangladesh, and Vietnam. Of these regions, Bangladesh and West Bengal are the most seriously affected in terms of the size of the population at risk and magnitude of health problems. Hence, chronic exposure to arsenic >50′′μg/L in drinking water can result in serious health problems. Common symptoms of arsenic-related ailments are skin, cardiovascular, renal, hematological, and respiratory disorders. Therefore, this chapter focuses on nature, origin, and extent of groundwater arsenic contamination, probable causes, and its impacts on food, drinking water, and social coverage. It further discloses mitigation approaches proposed and practiced by the different research groups to combat this problem and finally concludes.

The offshore supply vessel (OSV) industry is critical to offshore oil and gas operations around the world and contributes to the economic and ecological impacts experienced by the local communities supporting the offshore oil and gas industries. The OSV industry has not been studied significantly and the economic and ecological impacts to local communities is generally unknown. This paper aims to address these issues.

In this paper, the authors review the activities and logistical requirements involved in offshore exploration and development with special attention paid to workflows and the manner in which service vessels are utilized in the Gulf of Mexico. The authors estimate the OSV needs per stage of activity for offshore operations based on data collected from company planning documents, fleet utilization data from oil and gas companies and service providers, interviews and surveys. The statistical data is synthesized and reconciled and despite large variances the data sources are in reasonable agreement. Empirical data on circuit factors are also provided. The applications and limitations of the analyses are discussed.

In the US GOM, a large variety of marine vessels transport goods and provide services to exploration, development and production activity. OSVs provide a vital link between offshore E&P activities and shore‐based facilities. Offshore oil and gas operations cannot function without them and their utilization and spatial distribution provide a way of understanding the impacts of the offshore oil and gas industry on coastal communities.

This is the first empirical analysis of any offshore service vessel industry. The data presented here can be used to predict the environmental, economic, public health, and infrastructural consequences of alternative offshore development policies.

The elevated level of nitrate in groundwater is a serious problem in Texas aquifers. To control and manage groundwater quality, the characterization of groundwater contamination and identification of the factors affecting the nitrate concentration of groundwater are significant. The purpose of this paper is to determine factors which have significant impacts on the elevated groundwater nitrate concentrations of the Southern High-Plains and the Edwards-Trinity aquifers.

The characterization of groundwater nitrate contamination was undertaken by analyzing the hydrochemical data of groundwater within a statistical framework. The multivariate statistical analysis (ordinary least square) and geographically weighted regression (GWR) models were used to study the relationship between groundwater nitrate contamination and land use of the study areas.

Results show groundwater nitrate contamination is typically due to an overapplication of N fertilizers to cotton in the Southern High-Plains aquifer and to grassland in the Edwards-Trinity aquifer. Adjusted R² (0.45) explains variations of nitrate concentration by well-depth, cotton production, shrubland and grassland in the Edwards-Trinity aquifer. The results of an analysis of variations in N concentration with well depth for all 192 wells indicate that nitrate concentrations in water from wells in the Southern High-Plains and Edwards-Trinity aquifers tend to decrease with increasing well-depth.

In this study, the GWR model was built to identify nitrate concentration within a geographic framework to ensure sustainable use of groundwater, which is important for local management purposes. The analysis should include local spatial variations of elements such as hydrologic characteristics and the land use activities if groundwater nitrate contamination causes adverse effects on human and ecosystem health.

Pesticides have been detected in groundwater in many areas of the State of Washington over recent years. Laws and regulations of federal and state environmental protection and argicultural agencies have developed in response to concern over the public health risk to pesticide exposure. Prevalent views about health risk from pesticide exposure tend to emphasize either the economics and food availability, while downplaying risk of pesticide exposure, or the risk to people, while downplaying economic and food availability issues. The Aquifer Vulnerability Project of the Washington State Department of Ecology is using the Environmental Agency’s PATRIOT model to screen the State of Washington for susceptibility to pesticide leaching to groundwater. PATRIOT models the pesticide loading at the top of the water table when the user selects parameters to run in the model, including the crop and the pesticide.

We are growing accustomed to shock tactics of the US Administration in dealing with toxic residues in food or additives which are a hazard to man, as well as the daily press infusing sensation, even melodrama, into them, but the recent action of the FDA in calling in from the food market several million cans of tuna and other deep sea fish because of the presence of mercury has had the worthwhile effect of drawing world attention to the growing menace of environmental pollution. The level of mercury in the fish is immaterial; it should never have been there at all, but it stresses the importance of the food chain in the danger to man and animal life generally, including fish beneath the sea. Without underestimating risks of pollution in the atmosphere from nuclear fission products, from particulate matter carried in the air by inhalation or even skin absorption, food and drink, which includes aqua naturale would seem to be the greatest danger to life. What these recent events illustrate in a dramatic manner, however, is the extent of pollution.