Dredging operations entail the removal of bed materials and associated vegetation from a river channel. It is an underwater excavation to re-establish a channel so as to improve navigation or for commercial activities [1]. The dredged materials may be deposited in uniform layers over wet land vegetation or open bay bottom [2]. In Nigeria, manual dredging by natives has been in operation since the early part of the 19th century. This according to Aroh [3] was to get sharp sand (for construction purposes) and prevent sinking of boats. Sand erosion is a gradual change that is difficult to determine from environmental agents e.g. rainfall, runoff, streams and wind solely but coupled with dredging activity, sand erosion is determinable. Sand erosion is generally a three-step process of sand particles detachment, particles transportation or particles displacement and finally deposition at a different or new location [4]. Sand itself is a material with lesser degree of cohesion and therefore is vulnerable. The susceptibility of sand surface to the vagaries of erosion defines sand erodibility.Sand physical properties, namely particle size distribution (soil texture), structure, organic matter content and permeability govern erodibility [5]. Texture is the mix proportion of sand, silt and clay.Erodibility is high for sandy soil. Sandy soils with small amounts of fine, medium or coarse particles (2.00mm and 0.02mm) are found to have high erodibility. Sand structure is the aggregation of identifiable shape and bad aggregation which enables the sand to be eroded by the detachment force of a dredger. Also, sand organic matter (SOM) being highly discouraged due to heat in sand does not bind sand particles together into sticker aggregates, thereby offering no resistance to erosion. Permeability is the measure of the rate at which water percolates through sand under a head of water and is a function of sand structure, texture and bulk density, hence a function of sand particles [4]. Because of the high percolation feature of a sandy soil, erodibility is high hence erodibility can be defined by soil partcles size distribution. Particles size distribution is very important in soil conservation, engineering and management
IntroductionThe environmental degradation resulting from hydrocarbon exploration and production activities has diverse health and socioeconomic implications on ecosystem functionality and a major concern to all stakeholders globally and the Niger Delta in particular [1]. Major part of soil in the territory of oil and gas fields is characterized by suppression of biological activity. Petroleum hydrocarbons are technogenic wastes, in which the processes of natural self-purification capacity substantially weakened [2]. In uncontaminated soils, microbiological processes intensity varies depending on their physicochemical properties. In the soils characterized by natural moisture, microbiological processes proceed more intense compared to those, in which geothermal factor is less favorable. Various studies of complete suppression of microbiological degradation of hydrocarbons in highly contaminated areas is explained by hard saturation of soils with heavy oil fractions -asphaltenes and tars that prevent the diffusion of atmospheric oxygen and also by the absence of nitrogen, phosphorus and other biogenic elements that are necessary for microbial activity [3,4]. The anthropogenic influences, stemming from increased industrialization, oil exploration activities, sabotage and illegal refining of petroleum in oil-rich regions, on biogeochemical cycles could impede on soil quality evaluation [5]. Effective determination of contaminated sites can only be achieved with adequate knowledge of the interplay of site specific factors such as geology, nature of the contaminant, pathway receptors linkages, toxicity levels and deployment of appropriate contamination AbstractThis study evaluates the soil and microbiological properties of Olo Flowstation and Rumuekpe Metering Station. Standard sampling and analytical methods were adopted. Results of the soil microbiological composite samples from the random samples showed that the percent Hydrocarbon Utilizing Bacteria (HUB) was 40.0% and 27.27% for the top and subsoil, respectively. Though these values were high, they were below expected values in view of the high level of petroleum hydrocarbon spilled on the soils collected. The moderately high amount of hydrocarbon
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