| Denitrification is the main way to remove excess nitrogen in wetland，by whichnitrate or nitrite is converted to N2or N2O. Shuangtaizi estuary wetland has kinds ofvegetations and abundant biological resources. With the changes of naturalenvironment and human interference, water pollution and vegetation degradationwere more and more serious. Therefore, the research of denitrification characteristicsand influence factors in different types of wetlands had great significance forprotecting and utilizing Shuangtaizi estuary wetland.With the methods of field investigation and on-site simulation training,denitrifying bacteria and denitrification of reed and Suaeda salsa wetland inShuangtaizi estuary wetland were analyzed, and the effects of vegetation degradationon denitrification were also studied. In addition, the influences of denitrifying bacteriaand denitrification from the Organic pollutants pentachlorophenol (pentachlorophenol,PCP) were compared in different wetlands. All the work in the paper was able toprovide the theoretical basis for restoring vegetation and improving removalefficiency of nitrogen in Shuangtaizi estuary wetland, and to offer technical supportfor the removal of nitroge in the PCP-contaminated area. Specific contents and resultswere showed in the following three aspects.Distribution of denitrifying bacteria, denitrification rate (Potential denitrificationrate PDR), denitrification product N2O/(N2O+N2) and N2O release rate (potential N2Oproductionrate pN2O) were researched in reed and Suaeda salsa wetland, duringsummer and autumn,2013, which located at Shuangtaizi estuary wetland and havegood vegetation growth. The results showed that denitrifying bacteria in reed andSuaeda salsa were12.87cti3and17.70lyi3g-1respectively.soil. In reed wetland, the abundance of denitrifying bacteria had a significant positive correlation with moisturecontent, as well as had significantly negatively correlated with nitrite and salinity;while in Suaeda salsa wetland it had significantly negatively correlated with nitrite.Besides, TOC of sediment was also a influence factor of denitrifying bacteria. In reedand Suaeda salsa wetland, PDR were34.32,29.38mgN kg-1soil d-1respectively；N2O/(N2O+N2) was less than50%, and the reed wetland had a higher N2Oconversion; pN2O were7.03,8.54mgN kg-1soil d-1mgN kg-1soil d-1respectively.The main factors of denitrification were temperature and redox potential.Distribution of denitrifying bacteria，PDR，denitrification product N2O/(N2O+N2) and pN2O were researched in vegetation degradation, located in Shuangtaiziestuary wetland. The results showed that the degradation of vegetation had reducedthe number of denitrifying bacteria in wetland, the main limiting factor was TOC.PDR and pN2O significantly reduced; N2O/(N2O+N2) was similar with that in reedwetland, less than that in Suaeda wetland. It was speculated that changes ofdenitrification were based on the changs of number and type of TOC.The effects of PCP on denitrifying bacteria and denitrification were studied by ain-site modeling method in reed, Suaeda salsa and vegetation degradation wetland.The results showed that in the three wetlands, PCP had promoted the denitrifyingbacteria growth in short time. As time goes on, promoter action had decreased and60days later promoter action disappeared. PCP aslo had a promotion on PDR and pN2Oin short time, which were diffterent with concentration of PCP and types of wetland.And the promotion disappeared60days later. The effects of PCP on N2O/(N2O+N2)ratio in three wetlands were different. N2O/(N2O+N2) in reed wetland had littlechange; N2O/(N2O+N2) in suaeda salsa wetland reduced in a short time, but hadincreased60days later; in vegetation degradation wetland, PCP promoted theconversion rate of N2O and N2O/(N2O+N2) had reduced. |
PDF Full Text Request