Transport pathways of black carbon to a high mountain Himalayan lake during late Holocene: Inferences from nitrogen isotopes of black carbon

Historically, forest fires have played a significant role in the production and distribution of black carbon (BC), including its deposition in water bodies. BC can reach to water bodies through two main pathways: (i) wet and dry atmospheric deposition and (ii) transportation of soil BC via surface runoff. Identifying the transport pathways of BC after fire has proven to be a challenging endeavour. This study aimed to decipher the pathway of BC transportation to a lake (Wular Lake, Kashmir Valley, India) by utilizing nitrogen isotopic composition of BC (δ¹⁵N<inf>BC</inf>) from a sediment core spanning 3744 years. The δ¹⁵N<inf>BC</inf> record demonstrate that terrestrial N dynamics in the Kashmir Valley were predominantly influenced by shifts in climate condition during the late Holocene. The observed variations indicated lower δ¹⁵N<inf>BC</inf>, indicative of dominance of atmospheric transportation of BC to the lake, during relatively drier periods with higher forest fire activity. In contrast, higher δ¹⁵N<inf>BC</inf>, suggesting a dominance of soil BC transportation via runoff, aligned with relative wetter periods of low forest fire activity.