| Wetlands are widely distributed around the world and are known as "the kidney of the earth".Wetlands are the most eco-diverse and ecologically functional ecosystems in nature.Wetland provides many resources for human production,life and entertainment,is the most important human survival environment,is also one of the most important environmental capital of mankind.Wetlands play a pivotal role in defense and regulation of floods,the control of pollution and the degradation of pollutants.Wetlands are also the habitat of many wildlife,especially birds.Constructed wetlands are a sewage treatment technology,developed in recent years.It organically combined waste water treatment and environmental ecological,while treating sewage efficient it can also beautify the environment.Constructed wetlands can create ecological landscape,but also can bring environmental benefits and economic benefits.With the development of artificial wetland,it has been widely used in the treatment of domestic wastewater,industrial wastewater,oil extraction wastewater and so on.Due to the direct discharge of domestic wastewater to the rivers and lakes,the problem of eutrophication of water has become a serious water environment problem in today's society.At present,there are many ways to deal with domestic wastewater.Among them,constructed wetlands are paid more and more attention because of their low running cost,good purifying effect and ornamental.Removal of nitrogen from domestic wastewater can effectively reduce the occurrence of eutrophication of water,constructed wetlands remove nitrogen in wastewater by adsorption,sedimentation and transformation.It is important to study the removal mechanism of nitrogen in urban domestic wastewater by constructed wetlands,which provided theoretical support for improving the efficiency of denitrification in constructed wetland.In this paper,through the investigation of the artificial wet area of Panhe in Tai'an City,this paper further studies the different wetlands of plants,and the following conclusions can be drawn from the experiment:(1)The concentration of pollutants in autumn wetlands is basically lower than that in winter.The removal rate of pollutants in autumn was higher than that in winter.The highestremoval rate of total nitrogen(TN)was Acorus calarmus L.wetland,the removal rate was 49%in autumn and 37%in winter.The removal rate of winter Typha orientalis Presl.wetland was the worst,16%and the other was between 20%and 30%.The removal rate of ammonia nitrogen(NH4+-N)in Typha orientalis Presl.wetland was better than others in winter,and the removal rate was 22%.The removal rate of ammonia(NH3-N)in Thalia dealbata Link wetland and Scirpustabernae,montani wetland in autumn was better than other plant wetlands.the removal rate was 34.4%and 32.6%.The removal rate of nitrate(NO3--N)in Iris pseudacorus/L.?SpikedLoosestrlfe wetland in autumn was better than other plant wetlands.was 76.7%and 73.3%,respectively.The removal rate of other wetlands was between 19%and 37%.The removal rate of nitrate-nitrogen(NO3--N)in Scirpustabernaermontani wetland in winter was better than other plant wetlands,was 26.3%,and the removal efficiency of nitrate-nitrogen(NO3--N)in winter was basically the same.In this paper,NO2--N was detected in the system,but the content was lower,the concentration was below 0.1mg/L,the variation range was very small.(2)The number of microbes was determined by the traditional culture method.The relationship among the three kinds of microbes was ammoniated bacteria>denitrifying bacteria>nitrosated bacteria,and the number of nitrifying bacteria,nitrifying bacteria and denitrifying bacteria were higher than those of winter wetland system.The number of ammoniated bacteria in Scirpustabernaemontani?Acorus calamus L.?Zizania latifolia(Griseb.)Stapf?SpikedLoosestrlfe wetland system was significantly higher than that in the winter,and the number of ammoniated bacteria in Typha orientalis Presl.wetland system was slightly higher than that in the autumn,and the number of ammoniated bacteria in Iris pseudacorus L.?Thalia dealbata Link wetland in autumn and winter is basically the same.In addition to Typha orientalis Presl.wetland,the number of nitrifying bacteria in autumn in other wetland systems was significantly higher than that in winter.In winter,the number of nitrifying bacteria was the highest in Typha orientalis Presl.wetland system.In autumn,the number of nitrifying bacteria was the highest in Thalia dealbata Link wetland system.In addition to Acorus calamus L.?Thalia dealbata Link wetland system,the number of denitrifying bacteria in autumn in other wetland systems was higher than that in winter.In autumn,the number of denitrifying bacteria was the highest in Iris pseudacorus L.wetland system.In winter,the number of denitrifying bacteria was the highest in Scirpustabernaemontani wetland system.There was a good correlation between the number of nitrosated bacteria in each plant wetland and the removal rate of ammonia nitrogen(NH4 +-N)(R = 0.955 in autumn and R = 0.991 in winter).There was a good correlation between the number of denitrifying bacteria and the removal rate of nitrate-nitrogen(NO3--N).(3)ACE and Chaol indices were different in 14 samples,but the difference was not significant.The maximum ACE and Chao1 indices in autumn were in the Zizania latifolia(Griseb.)Stapf wetland,The maximum value of the index is in the Acorus calamus L.wetland in winter,which is consistent with the trend of the number of OTU.The main bacterial community structure of soils in different vegetation communities was different,but the difference was not significant.The main lines of the obtained sequences include Proteobacteria,Chloroflexi,Acidobacteria,Bacteroidetes,Actinobacteria,Planctomycetes,Gyanomacteria,Gemmatirmonadetes and Verrucomicrobia,38.2%,17.1%,11.2%,7.4%,5.5%,5.3%,4.3%,3.3%,1.4%respectively,of the total bacterial count.At the genus level,we also found that many dominant flora,such as Ramlibacter 0.3%?1.9%(0.8%),nitrospira 0.2%?1.8%(0.9%),Arthrobacter 0.1%to 2.9%(0.8%),Planctomyces 0.3%?1.3%(0.7%)and 0.2?2.0%(0.7%)of Rhodoplanes.The main nitrifying bacteria in this experiment mainly include nitrobacteria and nitrobacteria,which are relatively abundant in this experiment,and most of the wetland units in this experiment are in the autumn,The abundance of NOB in different samples was higher than that of AOB,and the performance of NOB was more obvious in autumn.The main denitrifying bacteria in this experiment mainly include Pseudormonas,Thiobacillus,Hypho,microbium,Rhodobacter,Desulfovibrio,and the like.The proportion of denitrifying fungi in the wetland was higher than that in winter.This is consistent with the trend of denitrifying bacteria measured by traditional culture methods. |
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