The researchers studied pollution in the Yellow River's Tongguan section by analyzing water and sediment data from 1950 to 2005. They found that non-point source pollution is a major issue during the flood season, with dissolved pollution being the main concern for nitrate and ammonia nitrogen, while adsorbed pollution is more significant for total nitrogen and total phosphorus. In wet years, nitrate nitrogen accounts for over 60% of the pollution load, while in dry years, it drops to around 25%. In 2006, nitrate nitrogen, ammonia nitrogen, total nitrogen, and total phosphorus made up 17%, 14%, 15%, and 41% of the total pollution load, respectively.