Overview of Reservoir Sediment Contamination

The concentration of inorganic phosphorus (IP) in the surface sediment of each of the studied reservoirs ranged from 208.8 to 636.7 mg/kg. The concentration of Fe/Al-P in the surface sediment in the four reservoirs ranged from 82.1 to 216.7 mg/kg, and the average value was 129.6 mg/kg, accounting for 11.54–18.1 % of the sediment total phosphorus (STP) content. The highest proportion of IP is observed in Yuqiao Reservoir, and Jinpen Reservoir had the lowest proportion. In addition, the results indicated that the Ca–P concentrations of the four reservoir sediments are in the range 180.7–303.4 mg/kg, with an average value of 247.1 mg/kg, accounting for 22.33–37.1 % of the STP. The content of organic phosphorus (OP) in the reservoir surface sediment is in the range 64.2–201.8 mg/kg, accounting for 9.85–18.52 % of STP content. The ion exchange nitrogen (IE-N) content (mg/kg) in reservoirs is significantly different. The IE-N content of Shibianyu Reservoir is much higher than that of other reservoirs, accounting for 18.35 % of the total nitrogen (TN). The IE-N in the studied reservoirs accounted for 15.33–18.35 % of the TN. IE-N exists in three different speciations: the concentration of ammonia is much higher than that of nitrate and nitrite, and the concentration of nitrite is the lowest. The cloning and sequencing results showed that microorganisms were made up of ten major categories, including shaped bacillus, Chloroflexi, Verrucomicrobia, Bacteroides, Acidobacteria, thick wall bacteria, actinomycetes, Gemmatimonadetes, Nitrospirae, and Planctomycetes, in the Jinpen Reservoir sediments.