Species of iron in the sediments of the Yellow River and its effects on release of phosphorus.

Species of Fe in the sediments from 21 sections of the Yellow River have been analyzed utilizing the so-called sequential extraction approach. The correlation between iron and phosphorus was analyzed, and the risk of release phosphorus was predicted. The results show that the content of residual iron (Fe) in the sediments is the highest, accounting for more than 92.55% of total iron (∑Fe) (the sum of the iron contents in each form is the total iron). Ca-bound phosphorous (P) is equal to the sum of authigenic calcium and phosphorus (P) and detritus calcium phosphorus (P), accounting for more than 73.01% of ∑P, in which P accounts for more than 90.91% of P, which is the main component of P and the main component of ∑P; Fe in sediments is closely related to P, and Fe is closely related to P and P, which is an important factor to control the release of endogenous phosphorus. The extremely significant positive correlation between Fe and P and P in sediments is that they are affected by complex geological conditions in the Yellow River Basin. Judging by the ratio of ∑Fe/∑P combined with the influence of human factors, the release of phosphorus in sediments of most reaches of the Yellow River is controlled by iron, while the release of phosphorus is inhibited. Sediments in Xigu section H4, Zhongwei section H5, Haibowan section H7, three Sanshenggong section H8, Liulin section H13, and Tongguan section H16 of the Yellow River have certain phosphorus release risks, because phosphorus release is not only controlled by iron but also influenced by human factors, such as industrial and agricultural production level and artificial dam construction.