舟山本岛大气污染输送过程的数值模拟分析

利用HYSPLIT-4后向轨迹模式和NCEP(美国国家环境预报中心)的2012年GDAS(全球资料同化系统)气象数据,结合NO₂、PM_2.5、PM₁₀和SO₂等常规大气污染物的质量浓度数据,对舟山本岛2012年4月、7月、10月和12月的大气污染输送过程进行了模拟,并通过聚类分析和潜在源区分析〔包括PSCF(潜在源贡献)和CWT(浓度权重轨迹)计算〕,确定大气污染传输路径及影响源区. 结果表明:舟山本岛气流后向轨迹呈明显的季节变化特征,4月主要受来自黄海海面气流轨迹的影响,其占总轨迹数的36.7%,ρ(PM₁₀)为(53.24±24.33)μg/m3；7月以途经琉球群岛和东海气流轨迹为主,占总轨迹数的48.4%,对ρ(NO₂)、ρ(PM_2.5)、ρ(PM₁₀)和ρ(SO₂)贡献分别为(24.63±6.33)、(28.60±4.83)、(52.89±18.76)和(8.67±3.11)μg/m3；10月气流轨迹主要来自于东海海面,占总轨迹数的49.2%；12月气流则主要来自辽宁南部和黄海,占总轨迹数的66.1%,对ρ(NO₂)、ρ(PM_2.5)、ρ(PM₁₀)和ρ(SO₂)贡献分别为(28.48±15.14)、(58.71±14.10)、(69.83±38.94)和(20.83±13.28)μg/m3. 舟山本岛PM_2.5的潜在源主要为毗邻城市间局地污染,集中于浙江沿海城市及杭州湾、上海等地. 

Numerical Simulation of Air Pollution Transport in Zhoushan Island, China

The HYSPLIT-4 backward trajectory model was used to simulate the atmospheric transport of air pollutants in Zhoushan Island, combining Global Data Assimilation System (GDAS) meteorological data from the National Centers for Environmental Prediction (NCEP) and concentrations of NO₂, PM_2.5, PM₁₀ and SO₂ in April, July, October and December 2012. In addition, the transport pathways and regional sources of atmospheric pollution were identified using cluster analysis. Meanwhile, the potential source contribution function and concentration weighted trajectory combined with weight factors were utilized to calculate regional sources for atmospheric pollution of PM_2.5 preliminarily. The results showed that the backward trajectory distributions of air mass flow in Zhoushan Island varied with seasons. The airflow from the Yellow Sea dominated the prevailing wind direction in April, occupying 36.7% of the total trajectories. The mass concentration of PM_2.5 was (53.24±24.33) μg/m3. In July, the airflows through the Ryukyu Islands and the East Sea surface were the main transport pathways, accounting for 48.4%. The values of NO₂, PM_2.5, PM₁₀ and SO₂ were (24.63±6.33), (28.60±4.83), (52.89±18.76) and (8.67±3.11) μg/m3, respectively. In October, the prevailing wind direction was dominated by the airflow from the East Sea surface, occupying 49.2%. In December, it was dominated by the airflow from the south of Liaoning Province and the Yellow Sea, accounting for 66.1%. The concentrations of the four pollutants were (28.48±15.14), (58.71±14.10), (69.83±38.94) and (20.83±13.28) μg/m3, respectively. The potential sources of PM_2.5 were mainly due to local emissions among the nearby cities, mostly concentrated in Hangzhou Bay, Shanghai and the coastal areas of Zhejiang Province.