An Experimental Study On Microbial Effects Of Nutrient Salts Release From Aquatic Sediments

As an important parameter that control the release processes of nutrition salt from sediment, Microorganism and various environmental parameters take actions together. Microbial effects on phosphorus and nitrogen release especially the connection of P releasing and phosphatase was studied through the simulated experiment, using sediments of municipal source water of Tianjin, Heihe reservoir and Fenhe reservoir as the research objects.Through simulating of sediment-water interface, the release characteristic of phosphate, change of the organic phosphorus fractionations and the trend of phosphatase were studied under microbial effect. The results show that: the influence of Microorganism in the course of P release from sediment is prominent. Under aerobic condition, phosphorus didn't release from the sediment when overlying water is neutral and acidic. The release of phosphorus occurred under sterilized and non-sterilized conditions when pH=9.1. Under anaerobic condition, microorganisms are able to use Fe (III) as electron acceptor and induce the release of phosphate. The release of Fe-P was not found under sterilized condition. The activity of alkaline phosphatase can be used to indicate mineralization and the release of organic phosphorus from sediment. Under anaerobic condition, microorganisms play an important role in the mineralization of Moderately Labile OP. Under aerobic condition, the mineralization efficiency of Labile OP is higher than the other kinds of OP fractionations by the effect of microorganisms.Through inspecting various environmental parameters that influent the activity of phosphatase in Heihe reservoir sediment and measure the activity of phosphatase and microbial biomass, the results show that: phosphatase in sediment of Heihe reservoir can be classified as alkaline phosphatase, showing higher activity at high temperature. The alkaline phosphatase and microbial biomass decrease in vertical profile. Sediment surface is the place where phosphorus cycling occurs frequently. As a crucial parameter, the effect of microorganisms is prominence. The relationship of stable release rate and the activity of alkaline phosphatase show negative correlation.The characteristic of nitrogen is resembled between Heihe reservoir and Fenhe reservoir. Microorganism is the dominated factor which influences ammonia release. When DO<2mg/L, ammonia happened to release. When DO=0-0.5mg/L, the ammonia release intensity which got to 50.18 mg/(d·m²) in Heihe reservoir was higher than that in Fenhe reservoir. Under sterilized condition, when DO=0-0.5mg/L, the release intensity of Fe²⁺ was weak, and the highest release quantity of phosphorus was 0.015mg/L. In the experiment adopting original water and original sediment, the release intensity of iron from sediment was as weak as 1.04 mg/(d·m²). When DO=0-0.5mg/L, Mn²⁺ was oxidated and deposited into the sediment of Heihe reservoir with the change of pH. Mn⁴⁺ was reduced and released to the overlying water in the experiment adopting original water and original sediment.