Carbonaceous aerosols play an important role in radiative forcing in the remote and climate-sensitive Tibetan Plateau (TP). However, the sources of carbonaceous aerosols to the TP remain poorly defined, in part due to the lack of regionally relevant data about the sources of carbonaceous aerosols. To address this knowledge gap, we present the first comprehensive analysis of the delta C-13 signatures of carbonaceous aerosol endmembers local to the TP, encompassing total carbon, water-insoluble particle carbon, and elemental carbon originating from fossil fuel combustion, biomass combustion, and topsoil. The delta C-13 signatures of these local carbonaceous endmembers differ from components collected in other regions of the world. For instance, fossil fuel-derived aerosols from the TP were C-13-depleted relative to fossil fuel-derived aerosols reported in other regions, while biomass fuel-derived aerosols from the TP were C-13-enriched relative to biomass fuel-derived aerosols reported in other regions. The delta C-13 values of fine-particle topsoil in the TP were related to regional variations in vegetation type. These findings enhance our understanding of the unique features of carbonaceous aerosols in the TP and aid in accurate source apportionment and environmental assessments of carbonaceous aerosols in this climate-sensitive region.

Carbonaceous aerosols play an important role in radiative forcing in the remote and climate-sensitive Tibetan Plateau (TP). However, the sources of carbonaceous aerosols to the TP remain poorly defined, in part due to the lack of regionally relevant data about the sources of carbonaceous aerosols. To address this knowledge gap, we present the first comprehensive analysis of the delta C-13 signatures of carbonaceous aerosol endmembers local to the TP, encompassing total carbon, water-insoluble particle carbon, and elemental carbon originating from fossil fuel combustion, biomass combustion, and topsoil. The delta C-13 signatures of these local carbonaceous endmembers differ from components collected in other regions of the world. For instance, fossil fuel-derived aerosols from the TP were C-13-depleted relative to fossil fuel-derived aerosols reported in other regions, while biomass fuel-derived aerosols from the TP were C-13-enriched relative to biomass fuel-derived aerosols reported in other regions. The delta C-13 values of fine-particle topsoil in the TP were related to regional variations in vegetation type. These findings enhance our understanding of the unique features of carbonaceous aerosols in the TP and aid in accurate source apportionment and environmental assessments of carbonaceous aerosols in this climate-sensitive region.

Arctic rivers provide an integrated signature of the changing landscape and transmit signals of change to the ocean. Here, we use a decade of particulate organic matter (POM) compositional data to deconvolute multiple allochthonous and autochthonous pan-Arctic and watershed-specific sources. Constraints from carbon-to-nitrogen ratios (C:N), delta C-13, and Delta C-14 signatures reveal a large, hitherto overlooked contribution from aquatic biomass. Separation in Delta C-14 age is enhanced by splitting soil sources into shallow and deep pools (mean +/- SD: -228 +/- 211 vs. - 492 +/- 173%) rather than traditional active layer and permafrost pools (-300 +/- 236 vs. -441 +/- 215%) that do not represent permafrost-free Arctic regions. We estimate that 39 to 60% (5 to 95% credible interval) of the annual pan-Arctic POM flux (averaging 4,391 Gg/y particulate organic carbon from 2012 to 2019) comes from aquatic biomass. The remainder is sourced from yedoma, deep soils, shallow soils, petrogenic inputs, and fresh terrestrial production. Climate change-induced warming and increasing CO2 concentrations may enhance both soil destabilization and Arctic river aquatic biomass production, increasing fluxes of POM to the ocean. Younger, autochthonous, and older soil-derived POM likely have different destinies (preferential microbial uptake and processing vs. significant sediment burial, respectively). A small (similar to 7%) increase in aquatic biomass POM flux with warming would be equivalent to a similar to 30% increase in deep soil POM flux. There is a clear need to better quantify how the balance of endmember fluxes may shift with different ramifications for different endmembers and how this will impact the Arctic system.