| Dianchi Lake is one of the most famous highland shallow lakes, which has urban water supply, aquaculture, aquatic shipping, sightseeing, adjusting the climate, flood control storage functions. It has a very important position in economic and social development for Kunming and Yunnan Province. As the social and economic development in Dianchi Lake watershed, pollution load into the lake gradually increased, water eutrophication level escalated, aquatic ecosystems being destroyed, management of Dianchi Lake pollution has become the most urgent task for all republic people and the government.This study investigated the concentrations of total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP) in three layers of different depths in water body, the interstitial water of surface sediments and the total phosphorus and six phosphorus fractions, eg, exchangeable P (Exch-P), aluminum bound P (Al-P), iron bound P (Fe-P), calcium bound P (Ca-P), Occluded Al-P (Oc Al-P) and occluded Fe-P (Oc Fe-P) in surface sediment through analysis of samples collected from 37 sites around Dianchi Lake in spring when it was under low flow monsoon period to obtain a better understanding of the lake feature, to identify the major factors influencing the phosphorus cycle in aquatic environment, to estimate the dominant potential phosphorus sources. The results indicated as follows:1) The contents of TP, TDP, and SRP in Caohai were higher than Waihai, the highest in northern Caohai. The horizontal distributions of TP in three layers were reduced from northeast to southwest and the regularities of TDP and SRP were decreased firstly from north to middle then increased from middle to south, the distribution pattern in interstitial water was more complex.2) In Waihai section, the average contents of TP in surface water and middle water were 72.7%,77.1% of that in overlying water, respectively. The average contents of TDP in surface water and middle water were both 94.3%. In Caohai section, the average contents of TP in surface water and middle water were 72.7%, 76.1% of that in overlying water, respectively, almost the same in Waihai. The contents of TDP and SRP in two upper layers basically at the same level. Vertical analysis suggested that the contents of phosphorus pools in water body were increased with depth.3) In Caohai section, the average contents of TP, TDP, SRP in interstitial water 3.45,5.61,4.97 times higher than that in overlying water, the mean relative contribution of TDP to TP, SRP to TP in interstitial water were 84.9%,64.3%, both higher than that in overlying water of 51.8%,44.7% which revealed a strong evidence of potential releasing trend from the interstitial water to the water body in hyper-eutropacation Caohai section. In Waihai section, the average TP content in the interstitial water was 1.46 times higher than that in overlying water, the mean relative contribution of TDP to TP, SRP to TP in interstitial water was 10.6%,3.5% also lower than 25.8%,11.3% in overlying water which was opposing to that in Caohai which revealed less potential releasing process generally.4) The contents of TP in Waihai were ranged from 1465.27-3650.12 mg·kg-1 with an average content of 1901.92 mg·kg-1, and the average content in Caohai was 3349.29 mg·kg-1. Two sections in Dianchi Lake were both in severely eutrophication status.5) In Waihai section, the rank order of phosphorus fractions was Fe-P>Oc Fe-P>Ca-P>Exch-P>Al-P>Oc Al-P, the contents of Fe-P, Ca-P, Oc Fe-P were at the same magnitudes, the contents of Exch-P, Al-P, Oc Al-P were two magnitudes lower than the former three. In Caohai section, the rank order of phosphorus fractions was Oc Fe-P> Fe-P>Ca-P>Al-P>Exch-P>Oc Al-P, and the contents of each phosphorus fractions was lower than that in the Caohai as the content of TP. |
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