Phosphorus distribution and sorption-release characteristics of the soil from newly submerged areas in the Danjiangkou reservoir, China

The phosphorus (P) distribution and sorption-release characteristics of the surface soil in new submerged areas from the Danjiangkou Reservoir were investigated, and assessed the potential risk of P released from the soils. The results indicated that the TP (total phosphorus) contents in the soils varied from 161.01 mg/kg to 1150.94 mg/kg, and the mean content value of TP was the highest in arable land (732.91 mg/kg), especially distributed in arable land above 160 m elevation; Calcium bound phosphorus (HCl-P) was the major fraction of TP, the proportion was ranged from 60.77% to 83.38% for different land using types; the highest proportion of OP (organic phosphorus) was 32.07% in grass land soils. For all the samples, the rank order P-fractions was HCl-P > OP > NaOH-P (Phosphorus bound to Al and Fe oxides). Besides, the contents of TP correlated significantly with the HCl-P contents, (r = 0.936, P < 0.01), NaOH-P contents (r = 0.661, P < 0.01), OP contents (r = 0.762, P < 0.01), and IP contents (r = 0.970, P < 0.01), but OP contents was no significantly correlated with HCl-P, NaOH-P contents. The sorption capacity of soil ranged from 578.79 to 1457.44 mg/kg, and the amount of P released from the soils were ranged from 0.635 to 5.957 mg/kg; however, due to the concentration of P in the overlying water, about 80% of the newly submerged area would act as sink of P.