School of Resource & Environmental Engineering, East China University of Science & Technology, Shanghai, 200237, China.
State Environmental Protection Key Laboratory of Cause and Prevention of Urban Air Pollution Complex, Shanghai Academy of Environmental Sciences, Shanghai, 200233, China.
Chemosphere. 2020 Aug;253:126613. doi: 10.1016/j.chemosphere.2020.126613. Epub 2020 Mar 30.
The absorption and scattering of aerosols are critical factors that influence in global climate and visibility degradation. From January 2013 to December 2015, aerosol scattering coefficients, PM, and meteorological parameters were continuously measured at a monitoring site in Shanghai, China. The annual means of scattering coefficients were 312.3, 232.1, and 261.9 Mm for the years 2013, 2014, and 2015, respectively. The corresponding values for PM were 61.6, 51.6, and 52.9 μg/m. Compared with the average scattering coefficient of the year 2013, those of 2014 and 2015decreased by 26% and 16%, respectively. Furthermore, the annual average PM decreased by 16% and 14% in 2014 and 2015, respectively. Although this study concluded that PM was generally correlated with scattering coefficients during the entire measurement period, the decrease in the former was much less than the latter. On this basis, ultrafine particles may decrease significantly because they cause aerosol scattering. This finding should be investigated further in the future. The inter-annual meteorological changes affected PM and scattering coefficient inter-annual variations. In the northwest and southwest direction, the seasonal and diurnal variations of aerosol scattering coefficients showed larger values when the wind speeds were about 3-5 m/s. The serious pollution in the northwest direction were mainly due to long-distance transport of pollutants during winter, whereas those in the southwest direction were attributed to local emission. The westerly wind frequency is the crucial factor influencing local pollution transport significantly. Backward trajectory analysis indicated that the air pollution in Shanghai in 2013-2015 is attributed to long-distance transport and primarily affected by the air mass from northwest direction. Observations on long-term aerosol optical properties on the basis of in-situ measurements can help thoroughly understand the radiative forcing characteristics of aerosol.
从 2013 年 1 月至 2015 年 12 月，在中国上海的一个监测点连续测量了气溶胶散射系数、PM 和气象参数。2013 年、2014 年和 2015 年的散射系数年平均值分别为 312.3、232.1 和 261.9Mm；相应的 PM 值分别为 61.6、51.6 和 52.9μg/m。与 2013 年的平均散射系数相比，2014 年和 2015 年分别下降了 26%和 16%。此外，2014 年和 2015 年的年平均 PM 分别下降了 16%和 14%。尽管本研究得出结论，在整个测量期间，PM 通常与散射系数相关，但前者的下降幅度远小于后者。在此基础上，由于超细颗粒会显著降低气溶胶散射，因此其含量可能会大幅减少。这一发现有待在未来进一步研究。年际气象变化影响了 PM 和散射系数的年际变化。在西北和西南方向，当风速约为 3-5m/s 时，气溶胶散射系数的季节和日变化呈现较大值。西北方向的严重污染主要是由于冬季污染物的长距离输送，而西南方向的污染则归因于当地排放。西风频率是显著影响当地污染输送的关键因素。后向轨迹分析表明，2013-2015 年上海的空气污染是由长距离传输引起的，主要受来自西北方向的气团影响。基于现场测量的气溶胶光学特性的长期观测可以帮助彻底了解气溶胶的辐射强迫特征。
