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

Abstract

a b s t r a c tThe 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.

Distribution Characteristics and Source Analysis of Nitrogen and Phosphorus in Different Rivers in Two Water Period: A Case Study of Pi River and Shiting River in the Upper Reaches of Tuo River in China

“…(3) PC3 (16.9%) was closely related to EN-NO 3 − -N, STN and Ex-P. According to the literature [50], Ex-P is associated with animal excrement in the breeding industry, and the decomposition of livestock excrement and animal and plant residues are one of the main sources of STN and EN-NO 3 − -N. Therefore, it was speculated that the third principal component was related to the decomposition of animal and plant residues. (4) PC4 (14.6%) showed a high correlation with OP, DIP, and EN-NH 4 − -N. EN-NH 4 − -N is ammonia nitrogen which is easily released from surface sediments and is related to agricultural production processes.…”

“…The sum of Ex-P, BD-P, and NaOH-P in surface sediments can be used to estimate the amount of bioavailable phosphorus (BAP) [53], i.e., that which can be directly absorbed and utilized by organisms, having a great effect on eutrophication of rivers. In the dry and wet seasons, the proportion of BAP in the surface sediments of the Pi river was higher, and the average proportion of BAP to STP was 20.9% and 20.6%, respectively, showing a higher phosphorus release risk and bioavailability and a greater effect on algal OP was found to be an important component of phosphorus in surface sediments, and its biochemical cycle played a key role in eutrophication [50]. In both the dry and wet seasons, the OP content in surface sediments in the Pi river was relatively high, accounting for 33.6% and 16.7% of STP, respectively, while that in the Shiting river was 13.4% and 12.9%, respectively.…”

“…As shown, the trends for HCl-P and OP were similar to that for STP, and the trends of Ex-P, BD-P, and NaOH-P were comparable. OP was found to be an important component of phosphorus in surface sediments, and its biochemical cycle played a key role in eutrophication [50]. In both the dry and wet seasons, the OP content in surface sediments in the Pi river was relatively high, accounting for 33.6% and 16.7% of STP, respectively, while that in the Shiting river was 13.4% and 12.9%, respectively.…”