Heavy metals in soil, sediments, and water from Lake Ohrid catchment (Albania)

Lake Ohrid is located in the Balkan Peninsula in South East Europe and it is shared between Albania and Macedonia. Formed in the tertiary period between 3.5 and 4 million years ago, Lake Ohrid is considered as one of the oldest lakes in the world, with numerous freshwater native and endemic organisms. Heavy metals enter in the lake through several pathways, mainly due to the pedo-geological processes of ultramafic soils and mining activities around the lake. This study aims to quantify the origin, the spatial distribution and the level of pollution caused by heavy metals in the soil, sediments and water of Lake Ohrid catchment. The soil, water and sediments samples were collected in November 2020. They were taken in six selected sites around lake. The results showed that the concentration of Fe, Cr, Ni, Co and Mn in soils samples that have ultramafic origin or are near dump sites was high, typical for ultramafic soil. The lake surface water was found to have low levels of heavy metals, except for nickel concentrations being higher in Memelisht, Hudenisht and Pojske, that are ultramafic areas. Sediments contained very high levels, mostly near ultramafic sites, and mineral dump areas with concentrations ranging 414-1333 mg/kg for Ni, 175-416 mg/kg for Cr, 101-163 mg/kg for Co, 233-600 mg/kg for Mn. and 13-40 g/kg for Fe. Sequential extraction of metals demonstrates that Nickel concentration in the sediments varies from 10 to 15 mg/kg in sampling stations near ultramafic areas and mineral dump areas. Thus, the ultramafic substrate and mining activities presented a potential toxic risk in Lake Ohrid catchment.