关键词: 土壤, 氧化亚氮排放, 影响因素

Abstract: The globalchange isvery im portantto the change ofenvironm entofhum an be- ings. The increasing ofcarbon dioxide, m ethane, nitrousoxide and othergreenhousegas- es in atm osphereisoneofthem ain inducem entto theglobalclim atechange. Thestudy on greenhouse gaseshas alw ays been the topicofgeneralinterest. Am ong greenhousegases, interestin the increasing ofatm ospheric nitrous oxide (N₂O) has been stim ulated by the understanding that this gas plays an im portant role in the chem istry ofthe stratosphere and the ozonelayerdestruction, itslong lifetim ein theatm osphereand asignificantinflu- ence on the earth therm albalance by the absorption oflong w ave infrared radiation (the greenhouse effect). Itisim portantto understand the sourcesand sinks, production m ech- anism s and m itigation m easuresofthe greenhouse gases. In this paper, we w illgenerally discuss aboutthe relevantstudy progressofN₂O em ission in the recentyears. The scholars ofChina and othercountries have done num erous field experim ents and laboratory sim ulation studieson globaldistribution ofN₂Osourcesand sinks, theseresults illustrated thatthe N₂Om ainly com esfrom soil, w aterbody, biom ass burning, fossilfu- els com bustion and som e industrialprocesses etc., and the sink of N₂O generally is thephotochem icalreaction in the stratosphere. Itism ore clearthatthenitrification and denitrification in soilare them ain N₂Oem is- sion m echanism s. Thefactorsthatinfluencetheem ission ofN₂Oin soilare sum m arized as follow s: (1) The application ofnitrogen fertilizer. The studiesshowed thatthe soiltreat- ed w ith the enduring effectfertilizerw illem ission less N₂Othan those treated w ith the or- dinary effectfertilizer, and the application ofenduring effectfertilizercan also increasethe yield ofthe crop. (2) Soilm oisture. The m axim alem ission ofN₂Oappears when the soil m oisture is 90% ～100% field capacity or 77% ～86% w ater-filled pore space. When the soilm oisture is below the saturation m oisture content, the nitrification is the m ain N₂O production m echanism . When the soilm oisture is above the saturation m oisture content, the denification isthem ain N₂Oproduction m echanism . Thesoilwillproducem ore N₂Oin the transition from w etto dry. Thediffusion coefficientofgreenhouse gases in unsaturat- ed soilis2～4 orderofm agnitudebiggerthan thatin the saturated soil. (3) Soiltem pera- ture. 15～35℃is the favorable tem perature range forthe m icrobe activities ofthe nitrifi- cation, 5～75℃is favorable tem perature range for the m icrobe activity ofthe denitrifica- tion, the em ission flux ofN₂O is norm aldistribution varying with the 5 cm daily average soiltem perature. (4) soilpH . The optim alpH is 7.0～8.0 forthedenification rate. (5) The contentofsoilorganic m atter. The m ineralization ofthe soilorganic m attercan pro- vide nitrogen (N) to soil. The favorable C/N ofsoilis 25～30∶1 to form N₂O. (6) Soil porosity. When the soilporosity islow, such as betw een 10% and 12%, the denification willenhance, there are m arked increasing oftheconcentrations ofN₂Oin the soilairafter their being com pacted by a tractor, but the flux of N₂O from soilto air is lower in the com pacted soilthan thatin theuncom pacted soilbecauseofthe hindrance during the em is- sion process. (7) Plants them selves. The root grow th ofplant and the secretion of the rootcan change the soilcondition (chem icaland physicalcondition), som e crops such as soybean, m aize and rice them selves can also em ission N₂O. w hat m ore, the illum inance and the cultivation ofthe fields etc. can also affectthe em ission ofthe N₂O.

Key words: soil, nitrous oxide em issions, influence factors