| Nitrous oxide?N2O?is a greenhouse gas with a high warming potential and is destructive to the atmospheric ozone layer.With the pollution of rivers,the nitrogen content in rivers continues to increase,and N2O in rivers has become one of the important sources of N2O in the atmosphere.This study mainly selects domestic typical rivers,studies and analyzes the variation of N2O concentration and release flux in different regions,different seasons and different types of polluted rivers,and determines the N2O emission coefficient.The research work is of great significance to reduce N2O emissions in rivers and reduce the damage of N2O to the ozone layer.Taking a number of rivers in Liaoning,Anhui,Hebei,Shandong,Hainan and Guizhou as research objects,based on the measured and collected data,the temporal and spatial variation of N2O concentration and release flux in rivers were studied.The emission coefficient of N2O in the river was calculated by three methods,and the calculation method of emission coefficient was selected by comparing with the IPCC recommended value of 0.0025.The variation of N2O concentration and release flux of three rivers contaminated by ammonium nitrogen pollution,nitrate nitrogen pollution and low concentration ammonium nitrogen and low concentration nitrate nitrogen were analyzed.The N2O concentration and release flux of different rivers in different regions are different.The N2O concentrations in some northern provinces such as Hebei and Liaoning provinces are 40.21?75360.1 and 7.03?9028.6nmol·L-1,respectively,and the release fluxes are 0.23?67918.99,17.21?15655.3?gN2O-N·?m2·h?-1.The concentration of N2O in rivers in some provinces in southern China,such as Hainan Province and Guizhou Province,was 7.8?67.94 and 8?75360.16nmo·L-1,respectively.The release fluxes were 0.311?11.167,7.92?368.64?gN2O-N·?m2·h?-1.The season has a certain influence on the N2O concentration and release flux in the river,and the winter is significantly higher than other seasons.The N2O concentrations in the rivers of spring,summer,autumn and winter were 12.56?325.56,8.12?1424.12,10.74?9028.6,13.6?75360.17nmol·L-1,and the release fluxes were 1.7?1074.46,0.64?552.5 respectively3.45?15655.3,0.56?67918.99?gN2O-N·?m2·h?-1,respectively.Different types of nitrogen pollution,N2O concentration and release flux in rivers are different.Ammonium-nitrogen-contaminated rivers are higher than nitrate-nitrogen and nitrogen-restricted pollution types.The concentrations of N2O in ammonium,nitrate and mixed-contaminated rivers were 20.14?75349.89,9.8?193.15,20.47?61.67nmol·L-1,respectively.The release fluxes were 8.36?67918.99,3.554?528.56,24.74?97.84?g·?m2·h?-1 respectively.The N2O emission coefficient?EF5-r?of the river was calculated by three methods.The average value of the calculation result of[N2O/NO3-]as the emission coefficient was 0.079,which was significantly higher than the IPCC recommended value of 0.0025;[N2O/NH4+The average of the calculation results as the emission factor is 0.00056,which is significantly lower than the IPCC recommended value.The average value of[N2O/DIN]as the emission factor is 0.0036,which is closer to the IPCC recommended value.In the area where the river is located,the seasonal variation of one year and the type of nitrogen pollution have an effect on the N2O concentration and release flux in the river.The N2O concentration and emission flux in the northern river are generally higher than that in the southern river;the N2O concentration in the winter river,Emission flux is higher than other seasons;ammonium-nitrogen-contaminated rivers are higher than nitrate-nitrogen and mixed-contaminated rivers. |
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