Determination of black carbon in lacustrine and coastal marine sediments by thermal oxidation

A thermal oxidation method was used to determine black carbon (BC) distribution in recent lacustrine sediments in four remote alpine lakes, i.e. Lake Krisko Sup., Lake Ledvica, Lake Krn and Lake Planina, in subalpine Lake Bled and in the coastal marine sediment in the Gulf of Trieste (northern Adriatic). Additionally, total carbon, organic carbon (OC) and total sulphur were also analysed. Sedimentation rates were determined by measuring Pb-210 activity. The lowest BC/OC ratios were noted in remote mountain lakes, ranging between 5-8% and depending upon precipitation amount. In Lake Bled, the BC/OC ratio increased to 10%, but the highest BC/OC ration was determined in the Gulf of Trieste, reaching 17%. A difference between atmospheric deposition input of BC into sediments in remote, clean areas and surface runoff and riverine input of BC in urbanised, polluted areas is clearly seen.