Abstract
Sediments are complex environments, with varying physicochemical characteristics, such as composition and type of organic matter, particle size distribution, and pH. Contaminated sediment is a significant environmental problem affecting many marine, estuarine and freshwater environments throughout the world. Most assessments of water quality have historically focused on water-soluble compounds, with relatively little attention paid to sediment. The aim of this research is to assess the physical and chemical parameters of sediments from Nwaja Creek, Niger Delta, Nigeria. Monitoring of this sediment quality is an important part of preserving and restoring the biological integrity of water bodies as well as protecting aquatic life, wild life and human health. Sediment samples from Nwaja Creek were sampled from seven sampling stations along the creek for over three months May to July, 2015, rainfall peak period, for assessment of their physical and chemical characteristics, such as grain size, organic carbon, pH, conductivity, nitrate and phosphate. These parameters are known to influence the interactions and dynamics of pollutants within sediment matrix. Sediment particle size distribution indicates that they have higher proportion of clay (clay > silt > sand), the mean percentage composition of clay, silt and sand ranged between 64.28% ± 22.04% - 72.36% ± 14.00%, 18.71% ± 12.03% - 27.32% ± 22.17% and 8.40% ± 6.28% - 9.76% ± 4.59% respectively. TOC in the study area is generally above 1% across all stations during the study period with a range between 0.98% and 4.58%. Minimal monthly and spatial variations are observed in particle distribution, pH (3.9 - 8.5) and phosphate (5.5 - 15.5 kg/mg) while significant variations are observed in conductivity (23.0 - 567.0 uS/cm), total organic carbon (0.98% - 4.58%) and nitrate (0.45 - 11.9 mg/kg) concentration. It is concluded that physicochemical characteristics of the sediments from Nwaja Creek are influenced by anthropogenic sources rather than natural as shown by the elevated phosphate and nitrate levels because the Niger Delta geology is not essentially rich in nitrate and its excess in surface or groundwater is considered as pollutant.
Highlights
In Nigeria’s Niger Delta, the challenges of water and sediment pollution have been of concern to all stakeholders because of the rate and extent of impairment of the environment and aquatic bodies by human activities, from industrial and domestic sources
High variations were observed in stations and months for the mean conductivity values of the sediments
This study presents the results of the physicochemical quality of the bottom sediment of Nwaja Creek in Niger Delta, Nigeria
Summary
In Nigeria’s Niger Delta, the challenges of water (surface and ground) and sediment pollution have been of concern to all stakeholders because of the rate and extent of impairment of the environment and aquatic bodies by human activities, from industrial and domestic sources. Sediment strata serve as an important habitat for the benthic macro invertebrates whose metabolic activities contribute to aquatic productivity [5]. Sediment is the major site for organic matter decomposition which is largely carried out by bacteria. Important macro-nutrients such as nitrogen and phosphorous are continuously being interchanged between sediment and overlying water [5]. Benthic organisms show habitat preference for specific types of sediment [8]. Sediment serves as reservoir for pollutants and a potential source of pollutants to the water column, organisms, and human consumers of those organisms. Contaminated sediment can cause lethal and sub-lethal effect in benthic and other sediment associated organisms [10]
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