Anthropogenic-Driven Alterations in Black Carbon Sequestration and the Structure in a Deep Plateau Lake

Abstract

The continuous flux of organic carbon (OC) from terrestrial ecosystems into inland water is an important component of the global carbon cycle. The buried OC pool in inland water sediments is considerable, and black carbon (BC) is a significant contributor to this OC pool because of the continuous growth in BC emissions. Therefore, determining the effect of BC on total OC burial and variations in the structure of BC during the burial process will contribute significantly to our understanding of lacustrine carbon cycling. This study investigated BC burial and its structural variations in response to anthropogenic drivers using four dated sedimentary cores from a deep plateau lake in China. The BC burial rate rose from 0.96 ± 0.64 g•m −2 •y −1 (mean of sedimentary cores pre-1960s) to 4.83 ± 1.25 g•m −2 •y −1 (after 2000), which is a 5.48 ± 2.12-fold rise. The increase of char was similar to those of BC. The growth rate of soot was 7.20 ± 4.30 times, which is higher than that of BC and char, increasing from 0.12 ± 0.08 to 0.64 ± 0.23 g•m −2 •y −1 . There was a decreasing trend in the ratio of char and soot at a mean rate of 62.8 ± 6.46% (excluding core 3) in relation to increased fossil fuel consumption. The contribution of BC to OC burial showed a significant increasing trend from the past to the present, particularly in cores 3 and 4, and the mean contribution of the four cores was 11.78 ± 2.84%. Source tracer results from positive matrix factorization confirmed that the substantial use of fossil fuels has promoted BC burial and altered the BC structure. This has resulted in BC with a higher aromatic content in the lake sediment, which exhibits reduced reactivity and increased stability. The strong correlation between BC and allochthonous total OC indicates that the input pathways of the buried BC in this plateau lake sediment were terrestrial surface processes and not atmospheric deposition.

Comment on “Anthropogenic-drive alterations in black carbon sequestration and the structure in a deep plateau lake”

“…Based on the discussion above, the reported chronologies of these cores and the calculated fluxes of BC and PAHs to the sediments in the article of Huang et al need to be re-examined.…”

“…The equation used for the constant rate of 210 Pb supply (CRS) model in the Supporting Information (SI; eq ) is wrong, it should be Where A (0) is the residual of unsupported 210 Pb in the entire record (from the sediment surface to the equilibrium depth of total 210 Pb with supported 210 Pb), or the 210 Pb inventory, A is the residual of unsupported 210 Pb in the sediments of age t or greater, and λ is the 210 Pb decay constant. As all the cores do not reach their equilibrium depths, the A (0) should not be only “the total content of 210 Pb in the sediment core” . If a core does not reach the equilibrium depth, our practice in the UCL Environmental Radiometric Facility is to estimate the equilibrium depth in the sediments by following the 210 Pb exponential decay trend in the bottom of the core, and then derive the missed unsupported 210 Pb beyond the core base for the residual calculations.…”

“…In the article of Huang et al, eq in the SI for calculating accumulation rate of BC and polycyclic aromatic hydrocarbons (PAHs) gives BC and PAHs units in g cm –2 yr –2 . This is incorrect.…”

“…Huang et al reported changes in the incorporation of black carbon (BC) in the sediments from a deep lake on the Yunggui Plateau in China. Burial processes and the relations with anthropogenic drivers were considered using four 210 Pb dated sediment cores.…”

“…Otherwise, the foundation of the research may be compromised. In the article of Huang et al, some points related to sediment dating need clarification.…”