Experimenal Study On Phosphate-rich Rocks Weathering By Phosphate-solubilizing Microorganisms In Chaohu Area

Some rock strata in Chaohu are rich in phosphorus.The weathering of rocks occurred and released phosphorus under the influence of various natural and human factors.The phosphorus moves to lakes and groundwater with storm runoff.In nature,there are microorganisms that can dissolve phosphorus and transform hardly-soluble rock phosphorus into bio-usable phosphorus,and the phosphorus migration rate and activity are improved.However,there is a lack of relevant research on the effect of weathering of phosphate-solubilizing microorganisms on rock phosphate release under current research.In this study,seven kinds of phosphorus-bearing minerals were collected from the mountainous area in the northeastern of Chaohu Lake.Ca-P was found to be the main component of the rock through grading phosphorus extraction.The study found that the distribution of P content was different in the depth of weathering degree,and the concentration of active phosphorus decreases with the depth in the vertical direction of Gufeng group.The pH value reduced with the rock phosphorus released by the weathering of microorganisms in the solution.Phosphorus released obviously with the concentration of dissolved oxygen(DO),there is a negtive relationship between the pH and the phosphorus concentration.In this experiment,optimization of culture conditions for phosphate-solubilizing by microbial flora were performed by single-factor and Box–Behnken design(BBD)experiments based on the culture conditions(particle size,rotational speed,carbon source and initial pH).The results showed that these factors have significant influence on the phosphorus concentration.The effect levels of these factors successively were particle size,carbon source,pH and rotational speed.The optimal phosphorus concentration were obtained at the particle size of 0.17 mm,the rotational speed of155.55r/min,the amount of carbon source 14.1g and pH 6.71 using response surface methodology.Under these conditions,the maximum phosphorus concentration was8.215mg/L.During the release of phosphorus in three soil columns,it can be found that the microbial weathering of the rock occurred mainly at the water-rock interface in the vertical range of 0 to 10 cm,and little or no weathering in the deep section,and thesamples from Fentou group have less change than Gufeng group.In the process of weathering,the released phosphorus showed increasing trend,which are Ex-P,Al-P,Fe-P and Or-P,however,De-P,Ca-P and Oc-P decreased.During the weathering of rock in Gufeng group,the physico-chemical parameters in the solution changed by the microorganisms,phosphorus was released into water and the concentration of active phosphorus increased.The organic acid is mainly oxalic acid released by microorganisms under the test condition.