Short-term Effect Of Exotic Sulfate On Phosphorus In The Sediment Of Lake Donghu In Wuhan

Acidification and eutrophication of watershed are the great environmental problems of lakes. The material exchange between overlying water and sediment, which are the two most important parts of lake processes, is a very important factor to eutrophication. At present the phosphorus input is in control, so the release of phosphorus from sediment is becoming more and more significant. In addition, the sulfate levels in lakes keep on rising with the continued expansion of industrialization. It is very necessary to clarify the relationship between sulfate and phosphorus. In this research, Lake Donghu was selected as the sampling field under indoor simulating condition to investigate the effect of sulfate reduction to sediments on the circulation of phosphorus of eutrophic lake. From the results obtained, the following conclusions can be drawn:(1) Sulfate input changed the salinity of overlying water firstly, and had an impact on the pH and Eh which affect the phosphorus release from sediments. In the process of sulfate reduction pH of sediments became lower significantly, and at the third week pH got most reduction compared with the control. There was a negative correlation between pH and Eh. After sulfate input the content of organic matter and active organic matter in sediments illustrated the same trend, which indicated that active organic matter was the main part of the mineralized organic matter.(2) Sulfur valence experienced variation during simulating experiment of six weeks. After the experiment, the concentration of sulfate in overlying water has increased, which has decreased in interstitial water. The content of single sulfide in upper sediment fell down, while contents of double sulfide and elemental sulfur increased. Neither single sulfide nor double sulfide showed obvious change.(3) Exogenous sulfate caused the phosphorus diffused to overlying water and interstitial water from upper sediment, and it would probably cause the transformation of phosphorus between the upper and lower sediment. The organic phosphorus content encountered a significant change between the third week and the forth week. Sulfate reducing bacteria (SRB) lowered the content of the labile organic phosphorus in upper sediment, but as the reducing action weakened the content of the labile organic phosphorus the other way round. The content of labile organic phosphorus in sediments remained on upward trend in general, and directly microbial mineralization was the most important mechanism of organic phosphorus consumption.(4) Phosphate monoester was the main form of organic phosphorus in the sampling sediment by the determination of31P nuclear magnetic resonance (31P-NMR). Exogenous sulfate accelerated the activity of phosphomonoesterase and phosphodiesterase, which led the phosphotriester to phosphate monoester. The process of sulfate reduction could improve the phosphate ester enzyme activity, followed by the decrease of phosphate ester enzyme activity along with the weakening of reduction and the increase of sulfur oxidation process.