The Speciation Of Phosphorus In Sediments Of The Yellow River And Its Main Inflow Sands

As one of the important essential elements for living beings, phosphorus could affect the primary productivity of sea, and further to affect CO₂ flux at the air-sea interface and global climatologic change. The phosphorus in sea is partially from sands and river inputs. The phosphorus conveyer belt comprised of the deserts in western Inner Mongolia, the sandstorm, the Yellow River and its estuary, the Yellow Sea, and the north maritime space in China is part of the global phosphorus cycle. In this study, an improved Ruttenberg analytical method was used to study the speciation of phosphorus in surface sediments from the mainstream of the Yellow River and the speciation in its main inflow sands. The bio-available species of phosphorus in the Sands and the sediments are calculated. Furthermore, the possible impacts of phosphorus from the sands and the sediments on the river and marine ecosystem are also discussed.We reached the conclusion as follows:1. The contents of total phosphorus in sands with natural grain size of the deserts in western China are 390.38-779.28μg/g. The proportions of Ca-bound phosphorus which is the dominant species are 41.6-73.6%; the proportions of residual phosphorus are in the second place, which are 16.1-44.5%; whereas the sum of other three species accounts for 15%. The contents of exchangeable phosphorus and Fe-bound phosphorus are higher at the Kubuqi desert and the Wulanbuhe desert, which are lower at the Tengeli desert, Badanjilin desert and the Heifengkou. However, the opposite condition is found for Ca-bound, residual and organic-bound phosphorus that their contents are higher at the Tengeli desert, Badanjilin desert and the Heifengkou, which are lower at the Kubuqi desert and the Wulanbuhe desert. 2. The experiments about the speciation of phosphorus in sands with different grain sizes in the deserts indicate that the contents of total, residual and organic-bound phosphorus are higher in the sands with smaller grain size; whereas the Fe-bound phosphorus present higher contents in sands with Iarger grain size.3. The contents of total phosphorus in the mainstream of the Yellow River are 221.95-1643.92μg/g. The residual and Ca-bound species are dominant species. The average content of Ca-bound phosphorus in the sediment is 605.6μg/g; the average content of residual phosphorus is 287.7μg/g; and their sum accounts for 71.1%-96.9% of the total phosphorus. Even though the contents of bioavailable species (exchangeable, Fe-bound and organic-bound species) only account for 9.12% of the total phosphorus, it is not negligible. The Yellow River transports 8.68 hundred million ton sands annually into the Bohai. Once the bioavailable phosphorus in particulates enters into the marine ecosystem, it must have serious impacts on the eco-environment of the Bohai.4. The content variation of bioavailable phosphorus in surface sediments along the Yellow River is presented. The higher phosphorus contents appear at the sections (such as Linhe, Tongguan, and Huayuankou) polluted seriously from artificial activity. However, the lower reaches where the Yellow River is aboveground hence the pollution from artificial activity is lower are characterized by relatively lower contents of bioavailable phosphorus.5. Comparing the speciation of phosphorus between surface sediments of the Yellow River and sands of the deserts, we found that the sand from the deserts in western Inner Mongolia functions as a phosphorus source hence transports large amounts of phosphorus into the Yellow River. The Wulanbuhe desert transports 11 thousand ton phosphorus into the Yellow River annually, and the content of exchangeable phosphorus is 492 ton. However, the Kubuqi desert transports 9200 ton phosphorus into the Yellow River annually, and the content of exchangeable phosphorus is 688 ton.