# Spatiotemporal variations in dissolved organic carbon in China’s major river basins and their associations with climate change and human activities

## TL;DR

This study analyzes how dissolved organic carbon in China's major rivers changes over time and space, and how it is affected by climate and human activity.

## Contribution

The study provides a comprehensive analysis of spatiotemporal DOC patterns and their drivers in four major Chinese river basins.

## Key findings

- DOC concentration shows a 'north high, south low' spatial pattern, while DOC flux shows the opposite.
- DOC concentration in all four basins increased significantly over time, averaging 0.04 mg L⁻¹ yr⁻¹.
- DOC flux into the sea increased in the Yangtze and Yellow River Basins by 0.05 Tg yr⁻¹ annually.

## Abstract

Riverine dissolved organic carbon (DOC) is a vital element of regional carbon cycling, yet its magnitude and influencing factors remain poorly quantified. Existing large uncertainties in the distribution, trends, and drivers of DOC compromise the accuracy of terrestrial carbon budget estimations. This study compiled 1922 DOC data points from literature on four major Chinese river basins (i.e., the Songhua River Basin, Yellow River Basin, Yangtze River Basin, and Pearl River Basin) for the period 1997–2023. The spatiotemporal patterns and driving mechanisms of DOC in these basins were quantified and systematically analyzed. Key results are as follows: [1] Spatially, DOC concentration (CDOC) exhibited a distinct “north high, south low” pattern nationally, while DOC flux (FDOC) displayed an inverted “south high, north low” distribution. Temporally, CDOC in the four basins all showed a statistically significant increasing trend, with an average annual rise of 0.04 mg L⁻¹ yr⁻¹. Meanwhile, the FDOC into the sea in the Yangtze River Basin and Yellow River Basin also exhibited a statistically significant increase, with an average annual growth of 0.05 Tg yr⁻¹ [3]. Attribution analysis indicated that the spatiotemporal distribution of CDOC was influenced by both climatic factors and human activities, whereas that of FDOC was controlled primarily by streamflow. The findings of this study reflect the national distribution and dynamics of DOC in major Chinese rivers, and provide a valuable framework together with details of key parameters to support future research into global riverine carbon cycle models.

The online version contains supplementary material available at 10.1186/s13021-025-00387-0.