Browsing by Author "Gautam, Sneha"

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A review on recent progress in observations, sources, classification and regulations of PM2.5 in Asian environments
(2016-11)
Gautam, Sneha
;
Yadav, Ankit
;
Tsai, Chuen-Jinn
;
Kumar, Prashant
;
環境工程研究所
Natural and human activities generate a significant amount of PM2.5 (particles aecurrency sign2.5 mu m in aerodynamic diameter) into the surrounding atmospheric environments. Because of their small size, they can remain suspended for a relatively longer time in the air than coarse particles and thus can travel long distances in the atmosphere. PM2.5 is one of the key indicators of pollution and known to cause numerous types of respiratory and lung-related diseases. Due to poor implementation of regulations and a time lag in introducing the vehicle technology, levels of PM2.5 in most Asian cities are much worse than those in European environments. Dedicated reviews on understanding the characteristics of PM2.5 in Asian urban environments are currently missing but much needed. In order to fill the existing gaps in the literature, the aim of this review article is to describe dominating sources and their classification, followed by current status and health impact of PM2.5, in Asian countries. Further objectives include a critical synthesis of the topics such as secondary and tertiary aerosol formation, chemical composition, monitoring and modelling methods, source apportionment, emissions and exposure impacts. The review concludes with the synthesis of regulatory guidelines and future perspectives for PM2.5 in Asian countries. A critical synthesis of literature suggests a lack of exposure and monitoring studies to inform personal exposure in the household and rural areas of Asian environments.
Development of an Automated System (PPWD/PILS) for Studying PM2.5 Water-Soluble Ions and Precursor Gases: Field Measurements in Two Cities, Taiwan
(2017-02-01)
Li, Ziyi
;
Liu, Yingshu
;
Lin, Yujie
;
Gautam, Sneha
;
Kuo, Hui-Chuan
An automated system consisting of a particle-into-liquid sampler (PILS) and a parallel plate wet denuder (PPWD) coupled with an ion chromatography was used for simultaneous measurement of ambient water-soluble ions in PM2.5 and precursor gases. The performance of the PPWD/PILS was validated by comparing it with the PDS (porous metal denuder sampler) for precursor gases (NH3, HONO, HNO3 and SO2) and PM2.5 ionic species (NH4+, NO3-, SO42-, Na+, Cl- and K+) measured in Taipei and Hsinchu Cities of Taiwan. Good correlations were demonstrated with linear regression slopes ranging from 0.92 to 1.04 and 0.84 to 0.97 as well as R-2 ranging from 0.76 to 0.83 and 0.89 to 0.94, for precursor gases and PM2.5 ions, respectively. The accuracy of the current system for precursor gases outperforms the other commercial systems. Field continuous data showed that NH3 was the most abundant precursor gas with the diurnal pattern peaking at low nocturnal boundary heights and during rush hours with local traffic emissions in Taipei, and with the pattern peaking only at mid-day associated with regional sources in Hsinchu. A reverse diurnal pattern for HONO in Taipei reflected the daytime photolysis and its nocturnal heterogeneous reaction, while its concentration was relatively constant at very low level in Hsinchu. SO42-, NH4+ and NO3- exhibited very similar diurnal patterns with the mean concentrations of 4.56 +/- 3.14, 1.55 +/- 1.16 and 0.52 +/- 0.5 mu g m(-3) in Taipei, and 7.95 +/- 5.52, 2.41 +/- 1.95 and 0.96 +/- 1.10 mu g m(-3) in Hsinchu, respectively. Correspondingly high concentrations of major ions to precursor gases were associated with the photochemical secondary aerosol formations and heavy traffic in Taipei. Based on an ammonia-rich atmosphere and high SOR values, (NH4)(2)SO4 and NH4NO3 were inferred to be the dominant inorganic salts in PM2.5 at both sites, which were also verified by the ion balance analysis.