An analysis of heavy metal content in sediments from valleys around Gozo

Abstract

Through this work, it was found that valleys around Gozo are not seriously contaminated with heavy metals; however minor traces of metals were detected in several locations. Gozo is a small island next to Malta, which has a lot of agricultural land that is intensively worked by local farmers, a low industrial activity and a small population of around forty thousand people. Given such a scenario it was interesting to see if some of the valleys which receive water from various parts of the island and lead to the sea are contaminated with heavy metals. Three valleys were chosen; one from Victoria to Marsalforn, another one which leads to Xlendi bay from Victoria/Kercem area, and lastly Mgarr ix-Xini valley. These three valleys were chosen as they are among the valleys which receive large amounts of run off water and also because they are the most prone to contamination. In fact the sites selected for sampling of the sediment were chosen on the basis that these areas received runoff water from particular regions and which were most susceptible to contamination. After identifying the sites and collecting the samples, analysis in the lab followed two processes. Initially water soluble metals were extracted from the refined sediments and the pseudo total digestible metals were extracted by following a digestion process. Subsequently the samples in liquid form were run through a microwave plasma atomic emission spectrophotometer. Samples were analyzed for Copper, Barium, Manganese, Cadmium, Zinc, Iron and Potassium. In the water soluble analysis, metals such as Iron and Potassium were more prominent in almost all areas, while other metals such as Barium and Copper recorded minor traces. Cadmium was hardly evident anywhere throughout the valleys. The pseudo total digestible metals analysis resulted in much higher values than for the water soluble for all metals except Cadmium which was not found anywhere. Mgarr ix-Xini valley was characterized by higher heavy metal levels for both the water soluble and the pseudo total digestible metals, which most probably is synonymous to the agricultural and livestock units and the scrap yard in the vicinity of the valley. The upper part of Xlendi valley recorded some high values of metals which are attributable to urban runoff, while Marsalforn valley had lower values of heavy metal contamination, except for some certain areas and metals.