珠江三角洲新垦大气核化速率研究

Atmospheric Nucleation Rate at Xinken Site in the Pearl River Delta of China

计算了珠江三角洲新垦地区的大气核化速率,对核化机制及核化速率计算的影响因素进行了分析.基于PRIDE-PRD2004观测实验期间新垦站点的气溶胶数浓度谱分布观测数据,计算出3 nm粒子的表观形成速率.根据表观形成速率与核化速率之间的关系式,分析了1 nm粒径临界核的大气核化速率.结果表明,新粒子事件期间3 nm粒子的表观形成速率为7.2～9.4 cm-3.s-1,1 nm临界核的大气核化速率为7.65×102～1.14×105 cm-3,与前体物硫酸蒸气浓度比较一致,气态硫酸应是主要的核化前体物.新垦地区背景气溶胶中积聚模态对碰并汇贡献较大,事件期间气溶胶数浓度变化对核化速率计算结果影响不大.本研究获取了新垦核化速率信息,有助于进一步了解核化机制.由于成核临界粒径的不确定性对核化速率计算结果影响很大,确定成核临界粒径对核化速率计算十分重要.

The atmospheric nucleation rates are calculated,the nucleation mechanism and factors affecting the calculation are investigated at Xinken Site in the Pearl River Delta of China.Based on particle size distribution data from Xinken site during PRIDE-PRD2004,the apparent formation rates of 3 nm particles are obtained.Nucleation rates for critical nuclei of 1 nm size are analyzed from particle flux equation of different size in the diameter axis.The results show the 3 nm apparent formation rates during the new particle formation events are 7.2-9.4 cm-3.s-1,the atmospheric nucleation rate for 1 nm critical nuclei are 7.65 × 102-1.14 × 105 cm-3.The derived nucleation rates are consistent with the concentrations of precursor vapor sulphuric acid,which are supposed to participate nucleation in most cases.With higher contribution of accumulation mode background aerosol to coagulation sink,the variation in particle number during event period imposes neglectable influence on the calculated nucleation rates.Information on nucleation rates provide further insight into the nucleation mechanism.Since variation in critical nuclei size may lead large uncertainty to nucleation rates,identification of the exact critical nuclei size is important for nucleation rate study.