hrvatski

Preliminary investigations of sediments and water of Lake Ohrid, Macedonia

The aim of the present work was to perform preliminary measurements of trace metals, nutrients, ions and mineral oils in water and sediment samples from Lake Ohrid, Macedonia and nearby springs. Lake Ohrid is situated in the mountainous region between southwestern Macedonia and eastern Albania. It is the deepest lake of the Balkan, with a maximum depth of 288 m and a mean depth of 155 m, covering an area of 358 km² and containing an estimated 55.4 km³ of water. The lake is 30.4 km long and 14.8 km wide at its maximum extent with a shoreline length of 87.53 km, shared between Macedonia (56.02 km) and Albania (31.51 km). It is one of deepest and oldest lakes in Europe, preserving a unique aquatic ecosystem with more than 200 endemic species of worldwide importance. It was formed from a geotectonic depression during the Pliocene epoch up to five million years ago. The lake was declared a World Heritage site by UNESCO in 1979, due to its extreme importance and natural beauty. Therefore, it is very important to establish regular scientific investigations and monitoring of the lake water and sediments, with the aim to keep the lake clean for the future generations. The Lake Ohrid has a drainage basin of about 2600 km² and is fed primarily by underground springs on the eastern shore (about 50% of total inflow), with roughly 25% shares from rivers and direct precipitation. Over 20% of the lake's water comes from nearby Lake Prespa through underground watercourses in karst, about 10 km to the southeast and at 150 m higher altitude than Lake Ohrid. The water leaves Lake Ohrid by evaporation (~40%) and through its only outlet, the Black Drim River, which flows in a northerly direction into Albania and thus to the Adriatic Sea. Therefore it is extremely important also to investigate quality of water and sediments of most important springs feeding the lake. So, besides samples from lake, samples from important springs around the lake have been investigated. Piper diagram was applied to define type of water according to main ions. According to it, water type was defined as: Ca2+Na+HCO3Cl-. All 5 studied water samples belong to this type, but lake water samples differ from spring water samples, as they have higher amount of Ca, Na, and Cl. Concentrations of measured nutrients are lower than maximal allowed values for lake and drinking water respectively. But, anthropogenic influence is obvious, as at Sv. Naum in the southern part of Lake Ohrid, near Albanian border concentrations are much higher, due to sewage pollution on Albanian side. It is especially interesting that nutrient concentrations are higher in all studied springs than in the lake water. Elevated concentrations at Drim spring (nitrates 1.07 N/L) could be due to the fact that water is arriving to this spring from Prespa Lake by underground connections, which is known to have eutrophication problem. Concentrations of all studied metals in filtered water samples are lower than maximal allowed values for lake and drinking water respectively. In non-filtered water samples from Lake Ohrid concentrations of Cu (6.50 µg/L) and Zn (0.719 µg/L) are somehow elevated at Sv. Naum and concentrations of Cd (0.161 µg/L), Cr (5.65 µg/L) and Ni (3.75 µg/L) are elevated at the beach in Donje Konjsko near Metropol Hotel. Sediments taken from four sampling locations (one from lake and three from springs) are very clean in respect to toxic metals. Only on Drim spring concentrations of Cr (46.5 µg/g) and Ni (41.8 µg/g) are slightly above the values which might cause minimal toxic effects. Mineral oils in sediments were above detection limit only at Biljana’s spring (32.8 µg/g), what is the value not likely to cause any toxic effects.

Lake Ohrid; Macedonia; water; sediment; trace elements; nutrients; mineral oils; anthropogenic influence

nije evidentirano

engleski

Preliminary investigations of sediments and water of Lake Ohrid, Macedonia

The aim of the present work was to perform preliminary measurements of trace metals, nutrients, ions and mineral oils in water and sediment samples from Lake Ohrid, Macedonia and nearby springs. Lake Ohrid is situated in the mountainous region between southwestern Macedonia and eastern Albania. It is the deepest lake of the Balkan, with a maximum depth of 288 m and a mean depth of 155 m, covering an area of 358 km² and containing an estimated 55.4 km³ of water. The lake is 30.4 km long and 14.8 km wide at its maximum extent with a shoreline length of 87.53 km, shared between Macedonia (56.02 km) and Albania (31.51 km). It is one of deepest and oldest lakes in Europe, preserving a unique aquatic ecosystem with more than 200 endemic species of worldwide importance. It was formed from a geotectonic depression during the Pliocene epoch up to five million years ago. The lake was declared a World Heritage site by UNESCO in 1979, due to its extreme importance and natural beauty. Therefore, it is very important to establish regular scientific investigations and monitoring of the lake water and sediments, with the aim to keep the lake clean for the future generations. The Lake Ohrid has a drainage basin of about 2600 km² and is fed primarily by underground springs on the eastern shore (about 50% of total inflow), with roughly 25% shares from rivers and direct precipitation. Over 20% of the lake's water comes from nearby Lake Prespa through underground watercourses in karst, about 10 km to the southeast and at 150 m higher altitude than Lake Ohrid. The water leaves Lake Ohrid by evaporation (~40%) and through its only outlet, the Black Drim River, which flows in a northerly direction into Albania and thus to the Adriatic Sea. Therefore it is extremely important also to investigate quality of water and sediments of most important springs feeding the lake. So, besides samples from lake, samples from important springs around the lake have been investigated. Piper diagram was applied to define type of water according to main ions. According to it, water type was defined as: Ca2+Na+HCO3Cl-. All 5 studied water samples belong to this type, but lake water samples differ from spring water samples, as they have higher amount of Ca, Na, and Cl. Concentrations of measured nutrients are lower than maximal allowed values for lake and drinking water respectively. But, anthropogenic influence is obvious, as at Sv. Naum in the southern part of Lake Ohrid, near Albanian border concentrations are much higher, due to sewage pollution on Albanian side. It is especially interesting that nutrient concentrations are higher in all studied springs than in the lake water. Elevated concentrations at Drim spring (nitrates 1.07 N/L) could be due to the fact that water is arriving to this spring from Prespa Lake by underground connections, which is known to have eutrophication problem. Concentrations of all studied metals in filtered water samples are lower than maximal allowed values for lake and drinking water respectively. In non-filtered water samples from Lake Ohrid concentrations of Cu (6.50 µg/L) and Zn (0.719 µg/L) are somehow elevated at Sv. Naum and concentrations of Cd (0.161 µg/L), Cr (5.65 µg/L) and Ni (3.75 µg/L) are elevated at the beach in Donje Konjsko near Metropol Hotel. Sediments taken from four sampling locations (one from lake and three from springs) are very clean in respect to toxic metals. Only on Drim spring concentrations of Cr (46.5 µg/g) and Ni (41.8 µg/g) are slightly above the values which might cause minimal toxic effects. Mineral oils in sediments were above detection limit only at Biljana’s spring (32.8 µg/g), what is the value not likely to cause any toxic effects.

Lake Ohrid; Macedonia; water; sediment; trace elements; nutrients; mineral oils; anthropogenic influence

nije evidentirano