Metal Pollution Assessment of Surface Sediments Along a New Gas Pipeline in the Niger Delta (Nigeria)

Abstract

Chromium, nickel, copper, zinc and cadmium were determined in sediments of the Niger Delta (Nigeria) in order to discriminate between natural metal sources and anthropogenic ones. Surface sediments were collected at seven sites along a new gas pipeline near Port Harcourt, between the New Calabar River and the Bonny River towards Bonny town. Chemical characterisation is obtained by hydrofluoric-nitric acid digestion procedure, providing the 'total' ('residual') metal contents. Information about the anthropogenic metal fraction was obtained by cold diluted hydrochloric acid extraction procedure. This 'labile' acid soluble fraction of metals, perhaps due to relatively recent inputs in the sediments, constitutes the fraction more likely to be available to marine organisms, and furnishes a first evaluation of the possible toxicity of sediments of this sensitive ecosystem. Zinc appears to be the most available of all the heavy metals: its 'labile' fraction attains 40-50% of the 'total' zinc in sediment. Sites near Port Harcourt city are the most contaminated. All the examined metals are one order of magnitude below the respective values proposed as a limit for toxicity and are comparable with those observed by other authors in similar Niger Delta areas. Some anomalous data found near Port Harcourt city suggest that zinc and cadmium are the metals that require further monitoring. Their anthropogenic source could be derived from urban and industrial sewage.

Assessing the Performance of a Sewage Treatment Plant in Habbak, Srinagar: A Physicochemical Analysis

“…Against the total sewage generation of 195 MLD, Srinagar has four sewage treatment plants with a total capacity of 32.2 MLD (Farhat, 2006). Studies have shown that sewage treatment processes might also affect the Physicochemical parameters of the final effluent such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), electrical conductivity, total hardness, alkalinity, dissolved oxygen, some metals, and non-metal ions (Rawat et al,1998;Adami et al, 2007). In addition, purification processes remove pathogenic microorganisms (Reasoner, 1982;Wang et al, 1966).…”

Determination of zinc in marine/lacustrine sediments by graphite furnace atomic absorption spectrometry using Pd/Mg chemical modifier and slurry sampling

“…Several studies determining the concentration of zinc in sediment samples have been reported; these have used sample solutions prepared mainly by acid digestion [8][9][10]. However, the preparation of sample solutions is time consuming and has a multistep procedure, which makes it difficult to analyse large numbers of sediment samples; e.g.…”