Relationships between dissolved black carbon and dissolved organic matter in streams

Area of Science:

• Environmental Chemistry
• Soil Science
• Hydrology

Background:

• Black carbon (BC) originates from incomplete combustion, with landscape fires being a major source.
• Atmospheric deposition of soot is a significant input of BC to soils, particularly in fire-unaffected areas.
• Dissolved black carbon (DBC) transport from soil to streams is a key BC loss pathway, though mechanisms are unclear.

Purpose of the Study:

• To investigate the sources and transport mechanisms of dissolved black carbon (DBC) in streams.
• To quantify DBC and bulk dissolved organic matter (DOM) in unburned watersheds.
• To determine the relationship between DBC and DOM characteristics.

Main Methods:

• Measurement of DBC quantity and quality using the benzenepolycarboxylic acid method.
• Analysis of quantitative and qualitative parameters of bulk dissolved organic matter (DOM).
• Sampling in Hokkaido, Japan, from catchments with no landscape fires for at least 110 years.

Main Results:

• DBC was present in streams, exhibiting low polycondensation, suggesting atmospheric soot as a primary source.
• DBC concentration showed a linear relationship with dissolved organic carbon (DOC) concentration across different conditions.
• The polycondensation of DBC correlated with qualitative DOM parameters, indicating linked transport mechanisms.

Conclusions:

• Atmospheric deposition of soot is a significant source of stream DBC in watersheds without recent fires.
• The transfer of soot-derived DBC to streams is associated with the transport of higher plant-derived, high-molecular-weight aromatic DOM.
• Understanding DBC-DOM relationships is crucial for elucidating BC cycling in aquatic ecosystems.