Neutron Activation Analysis as a tool to Determine Concentration of Selected Metals in Table Salt Mined from Benya Lagoon, Ghana

Abstract

This project was funded by The Directorate of Research, Innovation and Consultancy (DRIC) and the Management of the University of Cape Coast. It was sponsored as a Group-led Research involving researchers from the Department of Physics during the third call for proposals for Research Support Grants (RSGs) in 2018

Abstract

Table salt is essential for life and if it contains metal impurities, it can affect the people that consume it. The Komenda Edina Eguafo Abrem municipality makes salt by evaporating brine from the Benya Lagoon. Benya lagoon is a lagoon known to be polluted due to various anthropogenic activities within its environs. The concentration of eight metals, Arsenic (As), Cadmium (Cd), Manganese (Mn) Lead (Pb), Aluminium (Al), Copper (Cu), Magnesium (Mg), and Vanadium (V) have been determined in salt mined using water from the Benya lagoon. Salt samples were selected from five fixed-sampling stations and the concentrations of the metals determined using Neutron Activation Analysis. The ranges of the measured concentrations in the salts are as follows: 161.04-632.63 mg/kg for Al, 0.001-0.004 mg/kg for As, 1.50-2.70 mg/kg for Mg, 49.14-3883.00 mg/kg for Mg, 17.24-110.96 mg/kg for Mn, and 2.85-7.10 mg/kg for V. An assessment according to the metal concentration marked Mg as the most abundant, whiles Cd and Pb the least being 0.001 mg/kg at all the five stations. Principal Component Analysis also established Mg to be the most abundant metal, and used to identify two major clusters; Group 1 (stations 4 and 5) and Group 2 (stations 1, 2 and 3). Group 2 recorded higher intensities of Mg. Using Pearson's correlation coefficient, significant correlations were drawn between Al and Mg (r = - 0.862), Mg and Mn (r = 0.863) and Mn and V (r = 0.735), indicating the same or similar source inputs for each pair. Comparison with Codex Standard for Food Grade Salt showed that concentration values recorded for Al, Mg and Mn were above recommended limits. The contamination factor (C_F) and degree of contamination (C_D) confirmed this level of contamination for Al, Mg and Mn for all the five Stations, with Station 2 recording the highest Degree of Contamination. the least and corroborated salt from station 2 as most contaminated considering the combined toxicity at each station. Using an average daily salt intake of 6,000 mg, the mean daily intake of the elements when one consumes salt mined from the Benya lagoon was found to be above each element’s Upper Tolerable Limit of its Recommended Dietary Allowable for the various Life Stage Groups. The associated Hazard Index suggests the probability of adverse effects when consumed. High standard deviation values for Al and Mn indicated the non-uniform spatial distribution of the individual metal contaminates at the various stations.

Keywords: Benya Lagoon; salt; heavy metal; contamination factor; degree of contamination, neutron activation analysis; recommended daily allowance, GHARR-1

DOI: 10.7176/CMR/11-8-06

Publication date:October 31^st 2019