Fu Xiaoxin, Wang Xinming, Hu Qihou, Li Guanghui, Ding Xiang, Zhang Yanli, He Quanfu, Liu Tengyu, Zhang Zhou, Yu Qingqing, Shen Ruqing, Bi Xinhui
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
J Environ Sci (China). 2016 Feb;40:10-9. doi: 10.1016/j.jes.2015.12.001. Epub 2015 Dec 17.
In fall-winter, 2007-2013, visibility and light scattering coefficients (bsp) were measured along with PM2.5 mass concentrations and chemical compositions at a background site in the Pearl River Delta (PRD) region. The daily average visibility increased significantly (p<0.01) at a rate of 1.1 km/year, yet its median stabilized at ~13 km. No haze days occurred when the 24-hr mean PM2.5 mass concentration was below 75 μg/m(3). By multiple linear regression on the chemical budget of particle scattering coefficient (bsp), we obtained site-specific mass scattering efficiency (MSE) values of 6.5 ± 0.2, 2.6 ± 0.3, 2.4 ± 0.7 and 7.3 ± 1.2m(2)/g, respectively, for organic matter (OM), ammonium sulfate (AS), ammonium nitrate (AN) and sea salt (SS). The reconstructed light extinction coefficient (bext) based on the Interagency Monitoring of Protected Visual Environments (IMPROVE) algorithm with our site-specific MSE revealed that OM, AS, AN, SS and light-absorbing carbon (LAC) on average contributed 45.9% ± 1.6%, 25.6% ± 1.2%, 12.0% ± 0.7%, 11.2% ± 0.9% and 5.4% ± 0.3% to light extinction, respectively. Averaged bext displayed a significant reduction rate of 14.1/Mm·year (p<0.05); this rate would be 82% higher if it were not counteracted by increasing relative humidity (RH) and hygroscopic growth factor (f(RH)) at rates of 2.5% and 0.16/year(-1) (p<0.01), respectively, during the fall-winter, 2007-2013. This growth of RH and f(RH) partly offsets the positive effects of lowered AS in improving visibility, and aggravated the negative effects of increasing AN to impair visibility.
在2007 - 2013年秋冬季节，在珠江三角洲（PRD）地区的一个背景站点，对能见度、光散射系数（bsp）以及PM2.5质量浓度和化学成分进行了测量。日平均能见度以每年1.1千米的速率显著增加（p<0.01），但其中位数稳定在约13千米。当24小时平均PM2.5质量浓度低于75微克/立方米时，没有出现霾天。通过对颗粒物散射系数（bsp）的化学收支进行多元线性回归，我们分别得到了针对有机物（OM）、硫酸铵（AS）、硝酸铵（AN）和海盐（SS）的特定站点质量散射效率（MSE）值，分别为6.5±0.2、2.6±0.3、2.4±0.7和7.3±1.2平方米/克。基于机构间保护视觉环境监测（IMPROVE）算法并结合我们特定站点的MSE重建的光消光系数（bext）表明，OM、AS、AN、SS和吸光碳（LAC）对光消光的平均贡献率分别为45.9%±1.6%、25.6%±1.2%、12.0%±0.7%、11.2%±0.9%和5.4%±0.3%。平均bext显示出显著的降低速率，为每年14.1/Mm（p<0.05）；如果在2007 - 2013年秋冬季节期间，相对湿度（RH）和吸湿增长因子（f(RH)）分别以每年2.5%和0.16/年⁻¹的速率增加（p<0.01），而没有与之抵消的话，这个速率将会高出82%。RH和f(RH)的这种增长部分抵消了AS降低对改善能见度的积极影响，并加剧了AN增加对降低能见度的负面影响。
