Spatio-temporal Dynamics Of Dissolved Concentrations Of N₂O And CH₄ And Their Emission Flux In Weihe River Of Xinxiang

N₂O and CH₄ are the most insignificant greenhouse gas except CO₂.For the great warming potential of N₂O and CH₄,extensive researches have been conducted to make a global N₂O and CH₄source-converge list.This study took Weihe river in Xinxiang city area as research object,by monitoring the seasonal variation of N₂O and CH₄ dissolved concentration,and diurnal fluxes variation of N₂O and CH₄ between water-gas interface in summer and winter,to study the interactons between N₂O and CH₄ dissolved concentrations and environmental factors.We still carried out simulation research to illustrate how different types and amounts of added available nitrogen influence N₂O and CH₄ emissions of the river.（1）Water quality of Weihe river is worse in spring than in other seasons,but water qualities varied much between river sections because of land use and human activity intensity.Municipal sewage,industrial and agricultural waste water flowed into river would cause anoxia state at some points.Annually dissovled concentration of N₂O and CH₄ in Weihe river range respectively in0.03⁰.09μmol·L^-1 and 1.2³.3μmol·L^-1,with saturation range in 300⁹00% and 26000²40000%respectively,and overall it is in saturated and high supersatura tionstate,and supposed to be important potential source of atmospheric N₂O and CH₄.In spring dissovled N₂O and CH₄ concentrations of the river were significantly higher than those in other seasons（p<0.01）,while N₂O and CH₄ concentrations had no significant difference between the other seasons.The highest N₂O and CH₄ concentrations and saturation values is at sites S5,S11 and S12,suggesting that city sewage,industrial and agricultural waste water is the main factors that cause N₂O and CH₄ concentrated in river.Correlationanalysisshowed that N₂O concentration is significantly possitively correlated with nitrate nitrogen（NO₃^--N）,and ammounium nitrogen（NH₄⁺-N）and DOC,and temperature were found to have significantly negative correlation.Meantime,dissolved CH₄ concentration are significantly positively correlated to NH₄⁺-N,DIC and DOC,but are negtively correlated to DO and p H.（2）Research on diurnal fluxes variation of N₂O and CH₄ showed that the sellected 2 study sites,Jiansheqiao and Muye lake,display as source of the gases in the whole day time.Water quality in Muye lake is better than Jianshe bridge,and its’ N₂O and CH₄ emission rates were significantly lower than Jiansheqiao（p<0.01）.Compared fluxes in day and night,we can found that CH₄ emission are higher in night,but N₂O emission are not the same.N₂O emission rate were higher in day than night except in Muye lake in summer.In summer CH₄ and N₂O emissions in Jiansheqiao were influenced by air temperature,water temperature and DO,whileas in winter influenced by available N concentration.But there is no visible correlation between CH₄ and N₂O fluxes of Muye lake and environmental factors.Comprehensive analysis shows that,NH₄⁺-N is the primary factor that affects diurnal dynamic of CH₄ fluxes,and available N concentation and environmental factors woke together on the N₂O fluxes.（3）By adding available N of different types at different amount levels into water and sediment system,we simulated and monitored CH₄ and N₂O emissions under various N input condition.The result showed that N input have certain inhibition effect on the aquatic N₂O formation.Both High amount level of NH₄⁺-N(5¹0mg·L^-1)and low level of NO₃^--N(1⁵mg·L^-1)inputs would inhibit N₂O emision.When NO₃^--N and NH₄⁺-N were exist in the same time,concentration below 5mg·L^-1could inhibit N₂O release,but concentration more than 10mg·L^-1 can significantly promote the N₂O emissions.Exogenous NO₃^--N concentrations as 10 mg·L^-1 and 5 mg·L^-1can cause a strong stimulation on N₂O emissions fluxes and significantly greater than an other 2 kinds of N input conditions（p<0.01）,ammonium nitrogen（NH₄⁺-N）can cause weaker stimulation on N₂O emissions fluxe than an other 2 kinds of N（p<0.01）.In this study different amount levels and types of N input had similar stimulation effects on CH₄ emissions fluxe,there is no significant different between various treatment（p>0.05）.