A review on the analytical methods, chemical structures, distribution characteristics, sources, and biogeochemical processes of dissolved black carbon

Incomplete combustion of biomass and fossil fuels yields a variety of chemically distinct pyrolysis residues collectively referred to as black carbon (BC). Among these residues, dissolved black carbon (DBC) constitutes the water-soluble fraction, making it a significant component of the global dissolved organic carbon (DOC) pool. Consequently, it exerts an impact on the aquatic carbon cycle and global climate change. Owing to its unique molecular structure, DBC exhibits reduced reactivity in aquatic environments, thereby influencing the toxicity and environmental geochemical behavior of organic pollutants and heavy metals. While recent years have seen a surge in studies on DBC, yielding valuable insights, significant knowledge gaps persist regarding the fate and cycling of DBC. This review consolidates the advancements in analytical and determination methods for DBC and offers a critical assessment of the advantages and limitations associated with various analytical techniques. Furthermore, it comprehensively surveys our current understanding of DBC, encompassing its molecular composition, spatial distribution, sources, and biogeochemical processes. The review also underscores prevailing challenges related to quantitative and qualitative methods and underscores research gaps concerning the physio-chemical transformation of DBC. The overarching aim is to advance our comprehension of the biogeochemical cycle of DBC.