Chloromethane Emission Characteristics Of Methanogenesis Environment In Salt Marsh Of Northern Jiangsu

Volatile chloroalkanes are important chlorine source compounds in the atmosphere,which affect the global carbon chlorine cycle process and have very important environmental significance.Coastal salt marsh is a transitional zone between ocean and land,in recent years,it has become a key zone of chloromethane.In this paper,coastal salt marshes of Northern Jiangsu Province are selected as the research area to investigate and study the emission characteristics of chloromethane in the methanogenic environment.The conclusion is as follows:Firstly,coastal salt marshes in the northern Jiangsu have the ability of methane production,and have significant spatial and temporal differences.The tidal transport and the invasion of Spartina alterniflora significantly promote the methane emission of coastal salt marshes.The methane flux in tidal channel is higher than that in near tidal channel and far tidal channel.The difference of methane flux between growing season and non growing season is significant,especially the contribution of above-biomass of higher plants to methane flux in growing season is greater than that in non growing season.Secondly,along the salt marsh gradient of the combined action of tide and vegetation,the above-ground biomass of higher plants has different effects on soil nutrients,types and quantities of methanogens,types of methanogenic substrates,which will have certain impact on the potential and efficiency of methanogenesis.In particular,the invasion of Spartina alterniflora significantly changed the types and contents of substrates related to methane production capacity,as well as the types and abundance of corresponding methanogens.The change of methyl methanogenic substrate with trimethylamine as main component in coastal salt marshes promoted the change of methanogenic pathway from hydrotrophy to methylotrophy.Thirdly,in the environment of methanogenesis,the land-gas exchange characteristics of chloromethane in salt marsh ecosystem are special.On the one hand,the salt marsh ecosystem as a whole is a sink of chloromethane,which has a certain removal effect and ecological restoration ability to chloromethane of atmospheric environment.The formation and intensity of the sink of chloromethane in the coastal zone is related to the high initial concentration of chloroalkanes caused by the combustion of local biomass,as well as the difference of methane production and its environment;on the other hand,the above-ground biomass of the salt marsh higher plants in the coastal zone is the main source of chloromethane,which has a certain contribution to the atmospheric chloromethane.Finally,the characteristics of methane emission from salt marshes and chloromethane in the coastal zone of Northern Jiangsu Province are related to each other,with obvious temporal and spatial variation characteristics.The removal of above-ground biomass higher plants has a certain degree of influence on the flux of methane and chloromethane.The periodic effect of tidal water causes the change of soil physical and chemical properties and the transport capacity of plant root gas.