洪湖国际重要湿地沉积物磷空间分布特征及释放风险

洪湖国际重要湿地沉积物磷不同空间分布研究发现，洪湖入湖口沉积物TP含量范围为781.31~1955.84 mg·kg^-1，平均值为（1287.21±437.28）mg·kg^-1；湖区沉积物TP含量范围为438.33~1554.04 mg·kg^-1，平均值（718.10±238.15）mg·kg^-1.入湖口沉积物TP含量显著高于湖区沉积物（P<0.05），养殖围垸沉积物TP含量高于湖面沉积物，但无显著差异（P>0.05）.湖区西北和东北区域沉积物TP含量高于西南区域，四湖总干渠入湖口沉积物TP显著高于螺山干渠入湖口（P<0.05），四湖总干渠磷输入可能是洪湖沉积物磷主要来源.洪湖不同类型采样点的沉积物磷形态组成存在显著差异，入湖口沉积物磷形态以Fe/Al-P和Ca-P为主，而湖面沉积物以OP和Ca-P为主，空间磷形态组成变化与人类活动影响和水生植物分布有关.通过沉积物Fe/Al-P和OP估算沉积物生物有效磷（BAP）含量，以BAP占TP比例来估算洪湖沉积物磷释放风险，BAP/TP为39.8%~69%，均值为（56.5±7.23）%，存在较高的磷释放风险.OP和BAP与上覆水TP显著相关（P<0.01），BAP与上覆水正磷酸盐相关性最高，表明上覆水磷浓度可能与沉积物Fe/Al-P和OP向上覆水释放有关.

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

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.