与Instant Cast地面臭氧AQI更新

Posted on May 18th 2015
Share: aqicn.org/faq/2015-05-18/ground-ozone-air-quality-index-update-with-instant-cast/cn


(Attribution: Houston Clean Air Network )

The ground Ozone Air Quality Index calculation has just been updated to follow the Instant Cast concept, i.e. to report the pollution right now instead of the pollution from the previous hours. For more information about the Instant Cast, please refer to this article.

The calculation for the Ozone Index is now using the hourly reading, instead of the previous 8 hours average, but still applying the same 8 hours AQI breakpoints formula for AQI below 100. The previous procedure for calculating the 8-hour average concentrations is not used any more for Instant reporting. Above AQI 100, the normal 1 hour Ozone breakpoints are used (while before, the AQI above 100 was defined as the maximum of the 1 hour and 8 hours readings).

The graph on the right is summarizing the breakpoints in use. The green line is the one corresponding the "Ozone Instant Cast" breakpoints in use on the World Air Quality Index project

Index Values
Color coding
AQI Category1-hour
breakpoints
(ppm)
8-hours
breakpoints
(ppm)
8-hours breakpoints
proposed new
standard from US EPA
0 - 50
Good-0 - 600 - 50
51 - 100
Moderate-60 - 7550 - 65
101 – 150
Unhealthy
for Sensitive Groups
125 - 16575 – 9565 - 85
151 – 200
Unhealthy165 - 20595 – 11585 - 105
201 – 300
Very Unhealthy205 - 405115 – 375105 - 200
301 – 500
Hazardous405 - 505--

The US EPA EPA is proposing to strengthen the National Ambient Air Quality Standards (NAAQS) for ground-level ozone, based on extensive scientific evidence about ozone's effects (more information). This new standard (plotted in grey in the above graph) is only for 8 hours average breakpoints, and since it is not yet approved - it is not used for the "Ozone Instant Cast" breakpoints.
oOo

For those interested in understanding how this scale compares with the scale used by other countries, the first important point to pay attention to is that the the concentration unit used for the scales can vary: For the US EPA, the Ozone concentrations are expressed in ppm (particles per million) while for many other countries, including India and China, it is expressed in µg/m3;

Therefore, the first step for comparing the scales is to use a primary concentration unit. In this case, ppm is kept as the primary unit. The conversion from µg/m3; is somewhat straightforward and consists in multiplying the number of particles by the molecular mass of the ozone times the density of air.

The density of air is dependent on the ambient temperature and atmospheric pressure, but, in order to simplify, a common assumption of a 25 degrees Celsius ambient temperature and 1 atmospheric pressure is used. Under those conditions, the following formula is used for the conversion:
Ozone Concentration (ppb) = 2.1414 x Ozone Concentration (µg/m3)
The scales can now be compared on the same ppm scale, and the two graphs below shows the respective scales for 8 hour and 1 hour. So, once again, as it has been seen many times before, the scales used outside of US are actually much more safe than the one in US!




Click here to see all the FAQ entries
  • Nitrogen Dioxyde (NO2) in our atmosphere
  • Ozone AQI Scale update
  • Kriging Interpolation




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    关于空气质量与空气污染指数

    本网站采用的污染指数和颜色与EPA是完全相同的。 EPA的指数可以从 AirNow上查到

    空气质量指数空气质量指数级别(状况)及表示颜色对健康影响情况建议采取的措施
    0 - 50一级(优)空气质量令人满意,基本无空气污染各类人群可正常活动
    51 -100二级(良)空气质量可接受,但某些污染物可能对极少数异常敏感人群健康有较弱影响极少数异常敏感人群应减少户外活动
    101-150三级(轻度污染)易感人群症状有轻度加剧,健康人群出现刺激症状儿童、老年人及心脏病、呼吸系统疾病患者应减少长时间、高强度的户外锻炼
    151-200四级(中度污染)进一步加剧易感人群症状,可能对健康人群心脏、呼吸系统有影响儿童、老年人及心脏病、呼吸系统疾病患者避免长时间、高强度的户外锻炼,一般人群适量减少户外运动
    201-300五级(重度污染)心脏病和肺病患者症状显著加剧,运动耐受力降低,健康人群普遍出现症状儿童、老年人及心脏病、肺病患者应停留在室内,停止户外运动,一般人群减少户外运动
    300+六级(严重污染)健康人群运动耐受力降低,有明显强烈症状,提前出现某些疾病儿童、老年人和病人应停留在室内,避免体力消耗,一般人群避免户外活动
    (参考详见http://zh.wikipedia.org/wiki/空气质量指数)

    如果你想了解更多有关空气质量与污染,详见维基百科或者 AirNow

    有关健康建议详见北京的Richard Saint Cyr MD医生的博客:www.myhealthbeijing.com


    Usage Notice: All the Air Quality data are unvalidated at the time of publication, and due to quality assurance these data may be amended, without notice, at any time. The World Air Quality Index project has exercised all reasonable skill and care in compiling the contents of this information and under no circumstances will the World Air Quality Index project team or its agents be liable in contract, tort or otherwise for any loss, injury or damage arising directly or indirectly from the supply of this data.



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