Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 55, Issue 15, Pages 10852-10861Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c02742
Keywords
terrestrial organic carbon; compound-specific radiocarbon analysis; organic carbon degradation and aging; Pearl River estuary; estuarine environment
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Funding
- National Key Research and Development Program of China [2016YFA0601403]
- National Natural Science Foundation of China [U1706219]
- Swiss National Science Foundation [200020_163162, 200020_184865]
- 111 Project [B13030]
- China Scholarship Council [201806330030]
- Swiss National Science Foundation (SNF) [200020_163162, 200020_184865] Funding Source: Swiss National Science Foundation (SNF)
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Estuaries are crucial for organic carbon degradation and aging, which impact the export and burial of terrestrial organic carbon in marginal seas. This study found that fatty acid C-14 ages increased along the Pearl River estuary, indicating selective degradation of labile and younger organic carbon leading to apparent aging.
Estuaries are action zones for organic carbon (OC) degradation and aging. These processes influence the nature of terrestrial OC (OCterr) export and the magnitude of OCterr burial in marginal seas, with important environmental implications such as CO2 release and hypoxia. In this study, we determined the contents and carbon isotopic compositions (C-13 and C-14) of bulk OC and fatty acids (FAs) as well as the sedimentological characteristics of suspended particulate matter (SPM) samples collected from two sites over four seasons and of surface sediment samples from three sites in the Pearl River estuary (PRE) to evaluate processes controlling OCterr degradation and aging along an estuarine gradient. We found that the abundance-weighted average C(24-32)FA C-14 ages increased by an average of similar to 1170 years for SPM and by an average of similar to 3440 years in PR/PRE sediments, along the similar to 60 km PRE transect. These increases in the FA age coincided with an 86% decrease in the corresponding mineral surface area-normalized FA loading along the sediment transport pathway, implying that selective degradation of labile and younger OC resulted in apparent OC aging. These measurements reveal an important shift in the nature of OC, with implications for biogeochemical cycling within estuaries and for regional environmental changes.
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