Source diagnostic assessment of dissolved black carbon in selected lacustrine systems of northern Pakistan

Context Incomplete pyrolysis of biomass and fossil fuel generates black carbon (BC), which is deposited and stored in glaciers and soils for long residence times. BC is mobilised from its terrestrial pools because of physicochemical events and transported to lacustrine systems as dissolved black carbon (DBC). Aims Present study investigates status, chemical signatures and source-regions of DBC in Sheosar Lake and Upper Kachura Lake located in Skardu, Pakistan. Methods Benzenepolycarboxylic acid (BPCA) method was used to analyse DBC concentrations and polycondensation. Principal source contribution factor (PSCF) analysis was used to establish source regions of aeolian BC. Key results DBC concentrations in both lakes were consistent with Antarctic glacial lakes and much higher than in alpine lakes. Degree of DBC polycondensation in both lakes was in agreement with the aeolian BC fingerprint of the study area. Conclusions Local as well as transboundary emissions originating in South-east Asian, Middle Eastern and eastern European countries might be the main contributors of DBC in Sheosar and Upper Kachura lakes. Implications In light of increasing global BC emissions, constraining DBC dynamics in lacustrine systems could provide valuable insights into subsequent anthropogenic perturbations of global carbon cycle.