氨排放对华北典型地区冬季二次无机盐生成的影响

为研究氨排放对冬季PM_(2.5)中二次无机盐的影响,设置不同排放情景,应用CMAQ模式对华北地区典型城市——保定冬季无机盐进行了模拟研究。结果表明:将氨气在模式中排放置零的情景下,无机盐质量浓度降低了67.08%;氨排放削减与二次无机盐生成呈非线性关系,大气呈"氨限制"状态;氨排放削减能够有效抑制二次无机盐的生成,当削减幅度为50%时无机盐总体降幅达29.89%,其中硝酸盐、铵盐和硫酸盐降幅分别为53.78%、27.87%和5.64%;氨排放对重污染时段二次无机盐的生成贡献较高,当氨削减幅度为50%时无机盐总体降低40.58%;在当前大气环境下,氨排放削减是保定市冬季控制二次无机盐污染的重要途径。

Impact of ammonia emission on the formation of the secondary inorganic aerosol in winter in a typical area in North China

The paper is to report its trace study results on the impact of ammonia emission on the accumulation of the secondary inorganic aerosol in winter season in Baoding,a very typical area in North China by using a community multiscale air quality (CMAQ) model for simulating the secondary inorganic aerosols during the period between Nov.25 to Dec.20,2013.For the said research purpose,we have established different scenarios for the aforementioned purpose.The sensitivity testing results indicate that the inorganic aerosols decreased by 67.08％ on the condition that the ammonia emissions were set to zero for the data of the model inputs.We have also found that ammonia serves as a great contributor to the formation of the secondary inorganic aerosols during the winter period of the year in the area.For example,the nitrate and ammonium contribution decreased to zero while the sulfate decreased by 9.58％ among all of the inorganic aerosols,which proves that the sensitivity of nitrate turns to be higher than the sulfate to the same change of ammonia emission during the winter months therein.What is more,we have also noticed that the nonlinear response of secondary inorganic aerosols content concentrations to the emission change of ammonia can be worked out by comparing the different scenarios of the emission.For instance,the atmosphere in the winter was in a state of "ammonia-limited",with the total available ammonium content being insufficient to keep the difference between the charge-balance of the remaining anions and cations.The formation of the nitrate and ammonium can be remarkably suppressed by abating the ammonia emission.For example,50％ decrease of ammonia emission can be found by cutting the total emission of the inorganic aerosols,nitrate and ammonium by 29.89％,53.78％ and 27.87％,respectively.However,the sulfate may not reveal the same sensitivity,for example,a decrease merely by 5.64％.However,in contrast to the general pollution period,the inorganic aerosols tend to decrease more dramatically during the heavy pollution period,while 50％ cut of ammonia emission may cause a 40.58％ reduction of the total inorganic aerosols.Thus,the ammonia emission can be found to be an important contributor to the formation of the inorganic aerosols,especially,in the heavy pollution period.In the scenario of simultaneously reducing sulfur dioxides,nitrogen oxides and ammonia by 8％,10％ and 50％,respectively,the formation of secondary inorganic aerosols showed no more significant decrease than the scenario of 50％ ammonia emission cut alone.Therefore,the study results of this paper can help to conclude that the reduction of ammonia emission can be made to serve as an effective measure for controlling the secondary inorganic aerosols.