Connecting the alkaline ‘sink’ to the atmospheric carbon ‘source’ in eutrophic water treatment

ABSTRACT Water eutrophication and climate change are global challenges. Addressing the imbalance of carbon, nitrogen, and phosphorus is crucial for mitigating eutrophication. Utilizing atmospheric CO2 offers an eco-friendly and economic approach to restore aquatic ecosystems and combine climate change. This study investigated the effect of pH on dissolved inorganic carbon (DIC) concentrations in ultrapure, lake, and river water. pH levels (3.5–12.0) were adjusted using H2SO4 and NaOH in 0.5 ± 0.03 intervals and maintained at 25 ± 1 °C in a static water bath for 3 days. Results showed that alkaline conditions (pH ≥ 7.5) effectively enhanced CO2 absorption, significantly increasing DIC content (P < 0.05). Compared to pH 7.0, the average DIC content over 3 days in ultrapure, lake, and river water at pH 9.0 increased by 36.89%, 44.24%, and 45.25%, respectively. A field test in a 1.5 km eutrophic river confirmed that pH had positive correlations with C/N (P < 0.05) and C/P (P> 0.05). These findings suggest that creating alkaline conditions could help mitigate atmospheric CO2. However, these conclusions are based on our experiments, demonstrating potential benefits but requiring caution in their applicability. Further research is necessary to validate their ecological impacts and broader applicability.