Environmental Controls on the Riverine Export of Dissolved Black Carbon

Jones, Matthew W.; Aragão, Luiz E. O. C.; Dittmar, Thorsten; Rezende, Carlos Eduardo de; Almeida, Marcelo Gomes de; Johnson, Ben; Marques, Jomar S. J.; Niggemann, Jutta; Rangel, Thiago Pessanha; Quine, Timothy A.

doi:10.1029/2018gb006140

Cited by 18 publications

(26 citation statements)

References 171 publications

(446 reference statements)

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“…Nonetheless, most studies have failed to identify significant seasonality in the DBC content of DOC, including in major high-latitude rivers 48 , tropical rivers and temperate catchments 51,56 . Soil moisture, a proxy for seasonal hydrology, was also not found to be a significant driver of variability in the DBC content of DOC in tropical Brazilian rivers 42 . We verified that the differences in the DBC content of DOC across latitudes and biomes are not due to bias in the timing of sample collection.…”

Section: Resultsmentioning

confidence: 79%

“…Riverine dissolved black carbon (DBC) is chiefly a by-product of the decomposition of soil BC stocks, which are maintained by landscape fires and by small aerosol fluxes to the land surface 41,42 ( Fig. 1).…”

mentioning

confidence: 99%

“…Like OC more generally, the rate at which soil BC degrades is moderated by environmental factors, such as temperature, hydrology, soil characteristics (e.g. clay content, mineralogy and pH) and land use 33,[42][43][44][45] . Nonetheless, the disproportionate effect of these factors on rates of soil BC decomposition relative to bulk soil OC decomposition has been shown to drive variation in the DBC content of riverine DOC at regional scales 42,45 .…”

mentioning

confidence: 99%

“…Here, using an extended global data set of 409 DBC and DOC concentration measurements (Supplementary Dataset) 26,42,43,[45][46][47][48][49][50][51][52][53][54][55][56] , we evaluate global-scale variability in the DBC content of riverine DOC across latitudes and biome boundaries and extrapolate these spatial patterns to estimate global riverine DBC export. Our data set incorporates 409 coupled measurements of DOC and DBC concentration in total, including 195 from 34 major rivers and 214 from 44 minor channels (Supplementary Table 1).…”

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confidence: 99%

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Fires prime terrestrial organic carbon for riverine export to the global oceans

et al. 2020

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Black carbon (BC) is a recalcitrant form of organic carbon (OC) produced by landscape fires. BC is an important component of the global carbon cycle because, compared to unburned biogenic OC, it is selectively conserved in terrestrial and oceanic pools. Here we show that the dissolved BC (DBC) content of dissolved OC (DOC) is twice greater in major (sub) tropical and high-latitude rivers than in major temperate rivers, with further significant differences between biomes. We estimate that rivers export 18 ± 4 Tg DBC year −1 globally and that, including particulate BC fluxes, total riverine export amounts to 43 ± 15 Tg BC year −1 (12 ± 5% of the OC flux). While rivers export~1% of the OC sequestered by terrestrial vegetation, our estimates suggest that 34 ± 26% of the BC produced by landscape fires has an oceanic fate. Biogeochemical models require modification to account for the unique dynamics of BC and to predict the response of recalcitrant OC export to changing environmental conditions.

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Section: Resultsmentioning

confidence: 79%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Fires prime terrestrial organic carbon for riverine export to the global oceans

et al. 2020

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“…lack carbon (BC), a common residue of incomplete combustion of biomass and fossil fuel, is widely dispersed in soils and marine sediments 1,2 . Defined as a group of condensed byproduct chemicals, BC is thought to be chemically stable and hardly biodegradable 3,4 , thus representing a refractory fraction of organic carbon (OC), and its role in the global carbon cycle and its environmental impacts have received considerable attention 2,[5][6][7][8] . In recent years, several studies have reported that dissolved BC (DBC) could represent a significant fraction of BC mobilized and transported by rivers into the ocean [9][10][11][12] .…”

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Dissolved black carbon is not likely a significant refractory organic carbon pool in rivers and oceans

Tian

et al. 2020

Nat Commun

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Rivers are the major carriers of dissolved black carbon (DBC) from land to ocean; the sources of DBC during its continuous transformation and cycling in the ocean, however, are not well characterized. Here, we present new carbon isotope data for DBC in four large and two small mountainous rivers, the Yangtze and Yellow river estuaries, the East China Sea and the North Pacific Ocean. We found that the carbon isotope signatures of DBC are relatively homogeneous, and the DBC 14C ages in rivers are predominantly young and increase during continuous transport and cycling in the ocean. The results of charcoal leaching experiments indicate that DBC is released from charcoal and degraded by bacteria. Our study suggests that riverine DBC is labile and respired during transport and mixing into the ocean and that residual DBC is cycled and aged on the same time scales as bulk DOC in the ocean.

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Deciphering sources and processing of dissolved black carbon in coastal seas

Bao,

Niggemann,

et al. 2023

Limnology & Oceanography

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Dissolved black carbon (DBC) is the largest known slow‐cycling organic carbon pool in the ocean; yet, its sources and processing in the coastal seas remain poorly understood. To address this knowledge gap, we conducted a study in the East China Sea and South Yellow Sea to quantify and molecularly characterize DBC using benzene polycarboxylic acids (DBCBPCA) and ultra‐high resolution mass spectrometry (DBCFT), respectively. The concentration of DBCBPCA was 0.70–1.9 μmol C L−1 and exhibited a significant negative correlation with salinity. Significant correlations were also observed between salinity and molecular characters (oxygen‐to‐carbon ratio; double bond equivalent; molecular weight) of DBCFT. These findings collectively suggest that mixing processes primarily control the concentration and composition of DBC. A two‐end‐member mixing model revealed that riverine input and offshore water contributed ~ 22% and 63%, respectively, to the DBCBPCA in the study region. Additionally, atmospheric deposition and potentially other unidentified sources contributed at least ~ 15% DBCBPCA, assuming no removal. Furthermore, ~ 70% of DBCFT in the coastal seawater could be found in the river water, and aerosols, which was in line with the information from DBCBPCA. Our study provides the first comprehensive assessment of both the sources and influential processes of DBC in coastal seas, highlighting the importance of additional sources, such as atmospheric deposition, and emphasizing the need to identify previously unknown sources of DBC.

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Environmental Controls on the Riverine Export of Dissolved Black Carbon

Cited by 18 publications

References 171 publications

Fires prime terrestrial organic carbon for riverine export to the global oceans

Fires prime terrestrial organic carbon for riverine export to the global oceans

Dissolved black carbon is not likely a significant refractory organic carbon pool in rivers and oceans

Deciphering sources and processing of dissolved black carbon in coastal seas

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