Comparative Analyses for Air Quality Indexes
|關鍵字:||空氣品質指標;比較分析;永續環境系統分析;air quality index;comparative analyses;sustainable environmental systems analysis|
The current air quality index, PSI, is frequently questioned for its effectiveness in providing air quality warnings. Although our EPA adopt the PM2.5 sub-index of UK DAQI, both PSI and DAQI-PM2.5 do not give consistent warnings and may confuse the general public. Therefore, this study was initiated to compare PSI and various foreign indexes and evaluate their differences and applicability for replacing PSI. Monitoring data for 2011-2013 were collected. Twenty-nine stations from seven airsheds were selected for the following analyses. Data monitored during the periods with significant foreign dust or sandstorm attacks were excluded. Since the concentration level of the USA AQI PM2.5 at the sub-index value equal to 100 is quite close to our air quality standard, its PM2.5 sub-index is thus applicable for us to use. The remaining sub-indexes of AQI are similar to those of PSI, and thus AQI can be a good candidate for replacing our PSI. Although the PM2.5 sub-index of DAQI is our current interim index, its PM10 and O3 sub-indexes are determined according to WHO Air Quality Guidelines (AQGs), that are quite stringent and are currently difficult to achieve. The DAQI is thus not currently recommended. Two indexes, TAQI-S and TAQI-B, were proposed. The concentration levels of TAQI-S=100 and TAQI-B=3 are determined by our short-term air quality standards, with the only exception for NO2 that is based on the WHO AQG. The TAQI-S system is similar to PSI and AQI. Although TAQI-B has the same six sub-indexes as for TAQI-S, it is a ranking system that is similar to DAQI. Since the index values of TAQI-S rarely exceed 150, and thus the upper ceiling concentration level of the highest rank of each TAQI-B sub-index is thus determined by that for TAQI-S=150. According to the comparative analysis with AQI, both proposed indexes are also acceptable. Therefore, the three indexes are all recommended as proper candidates for replacing PSI.