Studies On The Effects Of Spartina Alterniflora Invasion And Aquaculture Contamination On Volatile Gases Emissions From Mangrove Wetland Soil And Their Regulating Factors

Mangroves are important components of coastal wetland ecosystems with high primary productivity,high soil carbon(C),nitrogen(N),and sulfer(S)reserves.The soils are under anaerobic conditions for a long time and are potential sources of volatile gas emissions which may play an important role in global climate change.Mangrove ecosystems are fragile habitats.In recent years,the ecological consequences of Spartina alterniflora invasion and human aquaculture pollution on mangrove ecosystems have caused widespread concerns.Among them,greenhouse gas flux and its relationship with environmental factors are the main focus in the current mangrove ecosystem research.However,emissions of volatile gases including volatile sulfur gases and volatile benzenes from mangrove wetlands have not been reported except for their emissions from terrestrial or marine ecosystems.Therefore,in this study,mangroves were selected as research objects to investigate the release of volatile sulfur gases and benzenes from mangrove soils and their relationship with influencing factors including biotic and abiotic factors under the interference of alien invasive species S.alterniflora invasion and human aquaculture pollution.In this study,the physicochemical properties of different soil layers of 0-100 cm and their effects on the release of volatile sulfide and benzene in mangrove soil were investigated.The main results obtained are as follows:1.Under the invasion of S.alterniflora,mangrove soil became the release source of MT,which had significant effect on COS and DMS,and the release amount increased by about 1.26 times and 5.15 times respectively.S.alterniflora invasion significantly reduced the sulfate content in soil pore water and the total sulfur in any soil layer at 0-100 cm depth.2.Under the invasion of S.alterniflora,the emission fluxes benzene,toluene,ethylbenzene,styrene and o-xylene have significantly incresaed.S.alterniflora invasion significantly increased the electron conductivity of any soil layer from 0-100 cm depth.3.Under the disturbance of aquaculture contamination,the emissions of volatile sulfur gases COS,H2S,CS2 and MT from mangrove soils increased significantly.In addition,the sulfate content in the soil pore water increased by about 50%compared to the control location.The total sulfur,total carbon,total nitrogen and CN ratio of any soil layer with a depth of 0-100 cm were significantly increased.4.Under the disturbance of human aqaculture pollution,the emission of volatile benzene compounds from mangrove soils increased significantly.In addition,the contents of ammonium ions and silicates are significantly increased.5.The volatile sulfur gases of mangroves are mutually transformed,and the release of H2S is small,and the content of sulfate is very high.This is likely to be the main metabolic pathway by sulfate-reducing bacteria-mediated sulphate oxidative reduction,or it may be due to the oxidation of H2S in the air.