Dissolved organic carbon concentration in four major river basins in China (Songhua River, Yellow River, Yangtze River, Pearl River)

Dissolved organic carbon concentration data were obtained through a systematic literature review of Chinese and English publications between 1997 and 2023 on the CNKI and Web of Science. Criteria for inclusion were as follows: (1) field-sampled data with clear coordinates and sampling times; (2) use of filter membranes with a pore size of 0.22–0.7 μm; (3) DOC content convertible to concentration units (mg L⁻¹, carbon basis); and (4) sampling of surface or mixed water to exclude stratification effects. Data were extracted from the main text, figures, tables, and supplementary materials of eligible studies. For papers without original data, digitization of graphs was performed to extract the required data.