Distribution and controlling factors of dissolved inorganic carbon in urban rivers of a North China megacity: Insights from δ 13 C DIC .

Transportation and transformation of the dissolved inorganic carbon (DIC) play a critical role in the regional carbon cycle. To clarify the natural and anthropogenic impacts on DIC, the concentration and isotopic composition of DIC (δ ¹³ C _DIC ) in two typical urban rivers in northern China (Yongding River, YDR, and Chaobai River, CBR) were measured. Mass-balanced calculations were employed to quantify the impacts of different weathering processes. The results indicated that carbonate weathering under the influence of mixed weathering agents was the primary weathering process in the YDR and CBR. Carbonate dissolution by carbonic acid was an important source of DIC in both the YDR and the CBR. According to the end-member calculations of δ ¹³ C _DIC , soil-respiration CO ₂ was a key factor controlling the carbonate weathering by carbonic acid. A high contribution of sulfuric and nitric acids to carbonate weathering was found in the YDR, especially in downstream areas with high-level anthropogenic activities. This indicated that anthropogenic activities can profoundly impact the weathering processes in watersheds. This study provides insights into the complex interactions between human activities and natural processes in shaping the carbon dynamics of urban rivers, highlighting the importance of natural and anthropogenic factors on carbon dynamics in urban rivers and providing insights essential for predicting carbon flux changes amidst urbanization and climate change.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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