Lateral and longitudinal variation in phosphorus fractions in surface sediment and adjacent riparian soil in the Three Gorges Reservoir, China

Abstract

Hydrological regimes have been significantly altered since the Three Gorges Dam (TGD) raised the water level of the reservoir to the maximum design level of 175 m in October 2010. This change might greatly influence the forms of phosphorus (P) in the sediment and the adjacent riparian soil. The purpose of this study was to reveal the lateral (sediment, water-level-fluctuation zone soil, and upland soil) and longitudinal (from the end of backwater area to the TGD) trends in P factions. Samples from 11 sites located along the main stem and ten sites located along eight tributaries were collected in June 2017. The P fractions were determined using the Standards, Measurements, and Testing (SMT) protocol. The results showed that the order of increase for average pH values was sediment (7.58 ± 0.62), WLFZ soil (7.44 ± 0.29), and adjacent upland soil (7.20 ± 0.68). The total organic carbon in the sediment was also highest with an average of 9.15 ± 2.97 mg·g. The average concentrated HCl-extractable P (total P), organic P (OP), inorganic P (IP), HCl-extractable P (HCl-P), and NaOH-extractable P (NaOH-P) were 630.02 ± 212.24, 161.89 ± 90.77, 468.13 ± 194.92, 335.65 ± 159.88, and 51.40 ± 36.20 mg·kg, respectively. The concentration of both total P and NaOH-P in the sediment of the main stem exhibited an increasing trend from the backwater area to the TGD. The average concentration of P species in the sediment was higher than those in the upland soil and the water-level-fluctuation zone (WLFZ) soil. For all the sediment and soil samples, the rank order of P species concentrations was HCl-P > OP > NaOH-P. Both IP and HCl-P were highly positively correlated with total P in the upland soil, the WLFZ soil and the sediment. However, only in the sediment, NaOH-P was positively correlated with total P and OP. All P species in the upland soil demonstrated greater spatial heterogeneity than those in the WLFZ soil and the sediment. Redundancy analysis revealed that the main variables explaining the variance in P species concentrations were Al in the upland soil and pH in the sediment.

Optimizing Phosphorus Fertilizer Use on the Loess Plateau: Impact on Soil Properties and Crop Production Efficiency

“…and biotic (microorganisms, phosphatase, etc.) [16][17][18]. In addition, land use patterns and fertilization can also greatly affect the changes in P fractions.…”

New Insight into Phosphorus Release of Rhizosphere Soil in the Water Level Fluctuation Zone

“…Previous studies of soil phosphorus form in the WLFZ have mainly focused on the determination of inorganic phosphorus, organic phosphorus, and total phosphorus using standard SMT extraction methods [17,18] and on the soil available phosphorus using the Olsen extraction method [19,20]. However, in this study different forms of both organic and inorganic phosphorus are determined using separate tests after each extraction step in the Hedley continuous extraction method [21], providing an in-depth analysis of soil phosphorus form distribution and transformation in the WLFZ.…”

Different tolerance of three typical riparian plants (Cynodon dactylon, Alternanthera philoxeroides, and Acorus calamus) to different depths of waterlogging caused variations in soil nutrient release and microbial diversity

“…In addition, Shen et al (2022) studied the changes in soil physical-chemical properties in the WLFZ of TGR from 2008 to 2013, finding that periodic changes in the water level significantly reduced the content of soil available phosphorus (P) and nitrogen (N). In particular, the periodic wet-dry cycle of WLFZ could cause a shift from large pores (.100 μm) to medium and small pores (,100 μm) in soil aggregates (Zhang et al 2018). With decreasing water table elevation, the microstructure of these aggregates also altered from loose and porous to compact and less porous, thus reducing the ability of soil to store nutrients (Zhang et al 2018).…”

“…In particular, the periodic wet-dry cycle of WLFZ could cause a shift from large pores (.100 μm) to medium and small pores (,100 μm) in soil aggregates (Zhang et al 2018). With decreasing water table elevation, the microstructure of these aggregates also altered from loose and porous to compact and less porous, thus reducing the ability of soil to store nutrients (Zhang et al 2018).…”