Study On The Existing Form And Release Rule Of Rock Phosphorus In Eastern Section Of The North Shore Of Chaohu Lake Area

Chaohu is located in the geological phosphorus-rich areas.The contribution of the surrounding rock phosphorus migration caused by natural weathering or artificial development process to the lake eutrophication can not be ignored. The Existing form and Release rule of phosphorus in rocks of chaohu lake basin(i.e.rock phosphorus) were investigated basis on the national water pollution control and management of science and technology projects in this paper.Existing form of rock phosphorus were investigated by sequential extraction method. Organic phosphorus accounted for 60.75% of the total phosphorus. Inorganic phosphorus exists mainly in the form of Ca-P ,rarely in Ex-P. The distribution percentages of phosphorus forms in rock samples are basically similar except Oc-P. In weathered samples Or-P> Ca-P> De-P> Fe-P> Al-P> Oc-P> Ex-P, but in non-weathered samples Or-P> Ca-P> De-P> Oc-P> Fe-P> Al-P> Ex-P. The weathering Ocgree of rock can be clearly showed by the ratio of Oc–P. There is significant correlation between various forms transformation of phosphorus.The release kinetics characteristics of rock P were investigated using continuous extraction with 0.5 mol·L-1 NaHCO3 in this study. And the application of statistical principles established in the chemical kinetics model to study the mechanism of rock source phosphorus release process. Also, the zero-order,first-order,second-order,simple Elovich, power function, and parabolic diffusion kinetics model were chose for analytical process ,then fitting the main chemical process of the release mechanism of rock phosphorus.The results show that the amount of the released phosphorus increased with the time, while the rate of phosphorus released declined with time. Several dynamic models, including the first-order, simple Elovich, power function, and parabolic diffusion kinetics models, were found to fit the data and described the rock P release kinetics well. The first-order model had the best fit. The data indicate that the release mechanism of rock phosphorus is a simple first-order kinetic reaction that mainly involves diffusion.At the same time,This study compared the phosphorus release of four kinds of common low molecular weight organic acids (oxalic acid, tartaric acid, citric acid, malic acid) on the rock phosphorus in Eastern section of the North Shore of Chaohu phosphorus-rich rocks, and analysis the existing form of part residue after extraction. The results show that the P release by citric acid is the largest when the organic acid concentration is less than 5mmol·L-1;When the concentration is more than 5mmol·L-1, there were linear correlation between P release and Organic acid concentrations.The P release by Oxalic acid and tartaric acid are the larget.Increasing trend of P release at this moment is much larger than the organic acid concentration is less than 5mmol·L-1.And increasing trend of P release by oxalic acid and tartaric acid is much larger than citric acid and malic acid. There were linear correlation between P release and organic acids termination pH while pH≤4.Transformation of each existing form of phosphorus by oxalic acid is the largest.