Spatial Distribution Characteristics of Phosphorus Fractions and Release Risk in Sediments of Honghu International Importance Wetland

Abstract

According to a spatial distribution analysis of phosphorus in sediments from Honghu Wetland, it was found that TP content in sediments at the mouth of Honghu Lake was 781.31-1955.84 mg·kg-1 and the average value was(1287.21±437.28)mg·kg-1. TP content in sediments in the open water area was 438.33-1554.04 mg·kg-1, with an average value of(718.10±238.15)mg·kg-1. The TP content of sediments in lake inlet was significantly higher than that of sediments in the open water area(P<0.05), and that in the enclosed aquaculture was higher than in the open water area, although no significant difference was observed (P>0.05). The TP content of sediments to the northwest and northeast of Honghu Lake was higher than that to the southwest of Honghu Lake, and the TP content of sediments in The Four-lake main canal was significantly higher than that of Luoshan main canal(P<0.05). The phosphorus input in the Four-lake main canal may be the main source of phosphorus in Honghu Lake sediments. The phosphorus fraction composition in sediments from different sampling sites were significantly different. Fe/Al-P and Ca-P were the main forms of phosphorus in sediments from the lake inlet, while OP and Ca-P were the main forms of phosphorus in sediments from the open water area. The variation in spatial phosphorus form composition was related to the influence of human activity and the distribution of aquatic plants. Fe/Al-P and OP contents were used to estimate the content of biological available phosphorus (BAP) in evaluated sediments, and the proportion of BAP in TP was used to estimate the risk of phosphorus release in Honghu sediments. BAP/TP was 39.8%-69%, with an average of(56.5±7.23)%, indicating a high risk of phosphorus release. OP and BAP were significantly correlated with TP in overlying water(P<0.01), and the correlation between BAP and phosphate in the overlying water was the highest. The results showed that phosphorus concentration in the overlying water may be related to the release of Fe/Al-P and OP into water bodies.