Potential Retention and Release Capacity of Phosphorus in the Newly Formed Wetland Soils from the Yellow River Delta, China

There are few researches on the characteristics of phosphorus (P) in the newly born wetland soils from Yellow River Delta of China. Meanwhile, whether the wetland soils can protect the aquatic ecosystem from excessive P input or not and the risk of P release from the soils to the water quality have generated considerable interests. Through isothermal batch static equilibrium sorption experiments followed by six subsequent extraction steps, the present study assessed the variations in P sorption and desorption properties of the newly born wetland soils in Yellow River Delta. It is found that the P sorption isotherms were nonlinear and the amount of P sorption reached a steady state as P initial concentration added increased in the studied soils. Though the capacity of P retention differed strongly among the studied zone, the soils can protect the aquatic ecosystem from excessive P input to a certain extent degree. From the desorption experiments, it is found that the newly sorbed P was easily desorbed in higher initial added concentration and the desorption P significantly decreased with successive extraction in all samples. The release of P from soil proposed a significant contribution to the water quality and eutrophication of coastal zone. Correlation and regression analyses showed that the amorphous and free Fe/Al oxides, correlated with clay content in the studied soils, were the crucial chemical factors ascribed to the soil P retention and release capacity. Desorption experiments showed that newly sorbed P was easily desorbed in higher initial added concentration and the desorption P significantly decreased with successive extraction in all samples. Correlation and regression analyses revealed that amorphous and free Fe/Al oxides correlated with clay content in the studied soils.