Fluvial silicon (Si) plays a critical role in controlling primary productivity and ecosystem health in freshwater, estuarine, and marine ecosystems. We evaluated how concentrations and flux of dissolved Si (DSi) of Yellow River changed over the last several decades of rapid climate warming and strong human interference using long-term data sets. We used the chemical weathering model to quantify the chemical weathering flux of silicates. The results showed that the DSi concentration and flux of the Yellow River has decreased since 1986, which was related to the decrease of silicate chemical weathering yield caused by the decrease of precipitation. Since the 21st century, the interference of human activities (irrigation consumption, damming, landuse change) has increased river Si losses, reduced sediment load. The increasing forest and aquatic biomass have enhanced the biogeochemical retention of DSi, which may counteract the enhanced silicate weathering due to climate change. As a result, the DSi concentration and flux did not increase significantly since 2000. The significant seasonal variation of DSi concentration and flux also demonstrated an important role in the long-term variation of DSi. Our results have implications for the timing and magnitude of silica processing in rivers and its delivery to global oceans.


 

Yellow River, dissolved silicates, silicate weathering, human interference, long-term changes