大气中丙烷光氧化臭氧生成活性的烟雾箱模拟

利用自制光化学烟雾箱模拟了丙烷和NOx大气光化学反应,研究了相对湿度以及丙烷与NOx初始浓度比值对臭氧生成的影响.实验表明,臭氧最大值及丙烷的臭氧生成活性最大值(IRmax)都随相对湿度的增大而减小.低相对湿度时,臭氧最大值大约出现在反应的22 h,IRmax变化范围为0.023 1～0.039 1;而高相对湿度时,臭氧最大值大约出现在反应的16 h,IRmax变化范围为0.017 2～0.032 0.在反应的20 h内,前12 h内相对湿度对丙酮的生成量影响不大,12 h后低相对湿度时丙酮生成量更大.在实验的4～20 h内,相对湿度为17%时,丙酮浓度为153×10-9～364×10-9;而相对湿度为62%时,丙酮浓度为167×10-9～302×10-9.臭氧最大值随着丙烷与NOx初始浓度比值增加而减少,在低相对湿度时线性负相关性更好.另外,还利用了MCM丙烷子机制对反应进行了数值模拟,并与实验结果进行比较,发现两者还存在较大的偏差.

Smog Chamber Simulation of Ozone Formation from Atmospheric Photooxidation of Propane

Atmospheric photochemical reactions of propane and NO_x were simulated with a self-made smog chamber. The effects of relative humidity (RH) and C₃H₈]₀/NO_x]₀ ratio on ozone formation were studied. The results showed that both the maximum ozone concentration and the maximum value of incremental reactivity (IR_max) of propane decreased linearly with increasing RH. Under lower RH conditions, the occurrence time of peak ozone concentration was about 22 h after the beginning of reaction, and IR_max varied from 0.0231 to 0.0391, while under higher RH conditions the occurrence time of peak ozone concentration was 16 h, and IR_max ranged from 0.0172 to 0.0320. During the 20 h of reaction, within the first 12 h RH did not significantly affect the yield of acetone, whereas after 12 h the lower RH condition could lead to relatively greater amount of acetone. During the first 4-20 h of experiments, acetone concentrations ranged from 153×10^-9 to 364×10^-9 at 17% RH and from 167×10^-9 to 302×10^-9 at 62% RH, respectively. Maximum ozone concentrations decreased with increasing C₃H₈]₀/NO_x]₀ ratio and a better negative linear relationship between them was obtained under the lower RH conditions. The smog chamber data and the results from simulation of the C₃H₈-NO_x reactions using the sub-mechanism of MCM were compared, and a significant deviation was found between these two results.