Richards L Willard
a Sonoma Technology, Inc. , Petaluma , California , USA.
J Air Waste Manag Assoc. 1999 Oct;49(10):1230-1237. doi: 10.1080/10473289.1999.10463911.
The U.S. Environmental Protection Agency (EPA) Notice of Proposed Rulemaking (NPR) for regional haze uses the deciview haze index (dv) as the indicator for visibility impairment and proposes a change of 1 dv as "a small but noticeable change in haziness under most circumstances." All previous visibility rules have specified human perception as the indicator for visibility impairment. This article examines the technical basis cited in the NPR for this new indicator for visibility impairment and for the perception threshold of approximately 1 dv. Derivations based on the assumptions and approximations cited in the NPR show that the deciview haze index does not have the correct functional form to relate changes in haze within federal Class I areas to the visual perception of those changes. The just-noticeable change in light extinction is, in most cases, inversely proportional to the sight path length instead of proportional to the light-extinction coefficient. These derivations also indicate that a 1-dv change in haziness is typically too small to be perceived in most Class I areas.
美国环境保护局（EPA）发布的关于区域雾霾的拟议规则制定通知（NPR）使用分贝视程雾霾指数（dv）作为能见度受损的指标，并提出将1 dv的变化定义为“在大多数情况下，雾霾程度有细微但明显的变化”。以往所有关于能见度的规定都将人类感知作为能见度受损的指标。本文审视了NPR中为这一新的能见度受损指标以及约1 dv的感知阈值所引用的技术依据。基于NPR中所引用的假设和近似值进行的推导表明，分贝视程雾霾指数并不具有将联邦一类区域内雾霾变化与这些变化的视觉感知联系起来的正确函数形式。在大多数情况下，刚能察觉到的光消光变化与视线路径长度成反比，而非与光消光系数成正比。这些推导还表明，在大多数一类区域中，雾霾程度1 dv的变化通常太小而无法被察觉。
