| dc.description.abstract | Light scattering from aerosol water-soluble inorganic ions (WSIIs) directly influences solar radiation budget of the Earth. In addition, aerosol WSIIs may indirectly affect light scattering and precipitation of cloud droplets when they act as cloud condensation nuclei. As biomass burning (BB) occurs commonly around the glBBe, short-interval variations of WSIIs from the long-range transported BB smoke are thus interesting to investigate. This work monitored short-interval values of PM2.5 WSIIs and accompanied with the related measuring items at the Lulin Atmospheric Background Station (2,862 m a.s.l.) for analysis in autumn 2016 and spring 2017.
The campaign in autumn 2016 showed that PM10 mass concentration was averaged at 4.6 ± 2.1 ug m-3 excluding the influence of mountain-valley wind. Among various PM2.5 WSIIs, SO42- was the sole ion exceeding detection limit with an average of 0.8 ± 0.6 ug m-3. Light-scattering coefficients of PM10 and PM1 were averaged at 14.8 ± 13.5 and 9.6 ± 0.8 M m-1, respectively. In contrast, PM10 and PM1 light-absorption coefficients were 1.4 ± 0.9 M m-1 and 1.1 ± 0.8 M m-1, respectively. These aerosol properties characterized background air of a high-elevation site in East Asia in autumn 2016. Note that the levels of WSIIs such as SO42-, NO3-, and NH4+ increased greatly when mountain-valley wind occurred.
In the field study of spring 2017, however, PM2.5 mass concentration, PM10 and PM1 optical coefficients, and PM2.5 WSIIs all exceeded the corresponding values in autumn 2016 when excluding the influences of BB and mountain-valley wind. Similarly, all measurements in spring 2017 exceeded that in autumn 2016 under the influence of mountain-valley wind, which was prBBably due to higher background values. During the BB events in spring 2017, levels of PM2.5 mass increased to 22.0 ± 8.3 ug m-3 and K+, a BB tracer, also increased greatly to 0.3 ± 0.1 μg m-3. The mean levels of other three major WSIIs, namely, SO42-, NO3-, and NH4+, were 4.3 ± 1.9, 1.1 ± 1.0, and 1.7 ± 0.8 ug m-3, respectively. Moreover, PM10 and PM1 light-scattering coefficients increased to 164.4 ± 46.4 and 108.2 ± 30.3 M m-1, respectively. The light-absorption coefficients were 21.8 ± 7.7 and 16.8 ± 6.3 M m-1, respectively. For the possible associated compound forms of WSIIs, the ISORROPIAⅡ model simulation came up with ammonium sulfate, ammonium bisulfate, potassium sulfate, ammonium nitrate, and potassium nitrate. Finally, the investigation of aerosol WSIIs on atmospheric radiation degradation showed that WSIIs influenced aerosol optical depth greatly.
| en_US |