Determination Of Elemental Concentrations In Edible Seaweeds From The Kenyan Coast Using X-Ray Fluorescent Technique

The environment and human health are intertwined in that human beings rely on natural resources as well as the artificial resource in the environment for survival. Therefore, what is found in the food and subsequently the bodies reflects what is in the environment.  The substances in the environment get into human bodies through: ingestion, inhalation and absorption via skin. In this study, the former is emphasized with regard to marine resources of the Kenyan coast.  Since ancient times, seaweeds have been used as a human food, animal feed, fertilizers, salt extractors and pharmaceuticals in Orient countries, particularly in China, the Korean Peninsula and Japan. The practice has spread across many countries of the world making seaweed industry one of the world’s big economic contributors approximated at US$ 6 billions annual income. The consumption in developing countries is not to any great extent especially in African countries. However, with the world’s growing demand for carrageenan, Kenya’s potential to produce edible seaweed especially the Eucheumoids and Gracilaroids used for agar and carrageenan hydrocolloids production in food industries is greatly enhanced. Though, the consumption of seaweeds is steadily growing in Kenya, no study has been done to examine its health implications in terms of trace element contamination associated with marine pollution at the Kenyan coast. This study sought to establish the total and bioavailability concentration levels of trace metals in the edible seaweed using X-Ray Fluorescence (XRF) technique to address the safety of seaweeds as food material as well as their use as biological indicators of marine pollution. The obtained concentrations(ppm) were: Ca [474.8±2.07 - 1.192.77±19.37; 152.948 ±1.5 - 379.4 ± 8.64], Cr [0.180±0.06 - 1.920±0.396; 0.011±0.05 - 0.175±0.036], Mn [3.58±0.16 - 9.67±0.86; 0.76± 0.04 - 3.72±0.36], Fe [15.42±0.21 - 123.89±2.85; 2.18±0.06 - 9.22 ± 0.26], Co [0.56±0.1 - 3.39±0.51; 0.11- 0.76±0.16], Cu [0.43±0.07 - 4.51±0.34; 0.102±0.010 - 0.618±0.12], Zn [1.94±0.090 -7.21±0.90; 0.38±0.02 -1.54±0.12], As [1.19±0.05 - 4.44±0.25; 0.12±0.02 - 0.88±0.08] and Pb [<0.06 – 0.62±0.2;  <0.06 – 0.14±0.06] for total and bioavailability contents respectively. In sediment and seawater, concentrations obtained were: Ca [98.55±13.29 - 2,433.33±182.56; 57.69±0.36 - 166.94±2.4], Mn[<0.09 - 3.07±0.8 ; <0.02 - 0.07±0.24], Fe[ 6.55±0.66 -122.5±8.15;  0.178±0.01 - 1.4±0.04], Cu[<0.1  -  0.49±0.22; <0.006  -  0.12±0.015], Zn[<0.11 - 0.97; <0.04 - 0.17±0.01], Hg [<0.11 - 0.378; <0.1] and Pb[0.14±0.04 - 0.83±0.11; <0.1] in ppm respectively. From the findings, concentrations of essential elements are higher compared to the toxic elements such as As and Pb which are not to any alarming levels according to EPA/WHO regulations. Therefore, the direct consumption of edible seaweeds as food should be encouraged. On the other hand, there are a lot of fluctuations in trace elements concentrations in sediments and seawater making seaweeds the best option as pollution indicators in marine environment.


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