Characteristics Of Phosphorus Fractions Based On Lake Ecoregions Differences

Phosphorus in sediments plays an important role in the phosphorus cycle of aquatic ecosystems,and its geochemical fractions are important parameters to control the availability of phosphorus in sediments.In this work,Lake Wuliangsuhai,Lake Hulunhu,Lake Daihai,Lake Bosten and Dalong Pond in Inner Mongolia-Xinjiang Plateau and Lake Poyang,Lake Taihu and Wuhan city lakes in East Plain were selected Based on the simultaneously extracted fractions of phosphorus and Fe,Al,and Ca,the spatial and temporal distribution characteristics of phosphorus in lake sediments were summarized in different lakes.Using palaeoenvironmental proxies,we experimentally explored the response relationship between phosphorus and environmental changes in lake basins according to the geochemical information archived in the sediment profiles,providing basic information to explain the geochemical cycling mechanism of phosphorus in lake sediments and the occurrence mechanism of eutrophication in different lakes.The main results were as follows:1.Phosphorus in different lakes showed significant spatial variation,ranking as Wuhan city lakes > Inner Mogolia-Xinjiang Plateau Lakes(Lake Hulun > Lake Daihai >Dalong Pond > Lake Wuliangsuhai > Lake Bosten)> East Plain lakes(Lake Taihu >Lake Poyang)for total phosphorus.The sediment quality assessment criteria indicated the East Plain lakes belonged to safe level,while Wuhan city lakes and Inner MongoliaXinjiang Plateau Lakes belonged to moderate pollution level.2.The compared results indicated that the predominant phosphorus fraction was Ca-IP with the sequence of Ca-IP > OP,Re-IP > Fe-IP,Al-IP > Ex-IP in sediments from Inner Mogolia-Xinjiang Plateau.For lakes from East Plain,the predomiant were FeIP and Al-IP with the sequence of Fe-IP,Al-IP > Ca-IP,Re-IP > OP > Ex-IP.The average proportion of active phosphorus in the two lakes was 18.7 % and 61.3 %,respectively.3.The correlation study suggested that there was a transformation from organic phosphorus to inorganic phosphorus in the process of sediment mineralization,as well as the interconversion between inorganic phosphorus fractions.The direction and degree of phosphorus migration and transformation depended on different depositional environments.4.The difference of dominant phosphorus fractions between Inner MongoliaXinjiang Plateau and East Plain indicated the effects of lake sediment heterogeneity and watershed environmental conditions on redistribution of phosphorus fractionation.The consistency of Fe-IP levels and eutrophication index indicated that Fe-IP,as the most sensitive phosphorus fraction,could reflect the phosphorus release potential from lake sediments.5.According to the value of NaOH-Al/BD-Fe and active phosphorus levels,it indicated that the phosphorus release risk was limited by Ca in sediments from Lake Hulun,not Fe and Al.The phosphorus release potential in other lakes was ranked as city lakes in Wuhan > Lake Taihu > Lake Poyang > Lake Bosten > Lake Daihai >Dalong Pond > Lake Wuliang Suhai.6.It was showed that the distribution of phosphorus in lakes was affected by both climate change and human activities in lake basin according to the record of the climate change process and the profile distribution of phosphorus archived in the cores.Further,the responding fraction of phosphorus to climate evolution was discrepant in different lakes.