Environmental diffusion

当一种可能是恶臭的、易燃的或有毒的气体被释放到大气边界层时，人们想知道在不同地点和时间遇到的可能的浓缩值。这些浓度值很难预测或测量。环境处于动荡状态，现场(以及实验室)测量的非常不规则的浓度值通常表现出极大的浓度漂移，是标称平均水平的数倍。通常用于定量化浓度值的描述符是概率密度函数，然而这在环境背景下是不切实际的。新的衡量标准--预期质量分数函数--具有显著的优势，一方面是因为支配其演变的方程相对简单，另一方面是因为编制这一统计数据所需的测量浓度数据相对较少。因此，建议使用预期质量分数函数从实验和理论上研究污染物浓度值的行为。

When a gas, which may be malodorous, flammable or toxic, is released into the atmospheric boundary-layer one would like to know the probable concentration values encountered at various locations and times. These concentration values are very difficult to predict or to measure.The environment is in a turbulent state and the very irregular values of concentration recorded in field (and also in laboratory) measurements commonly exhibit extreme excursions of concentration that are many times the nominal average level. The usual descriptor used for the quantification of concentration values is the probability density function however this is impractical in the environmental context.  A new measure for quantifying concentration values has been proposed. The new measure-The Expected Mass Fraction Function-has significant advantages both in terms of the relative simplicity of the equations that govern its evolution and in the relatively small amount of measured concentration data required to compile this statistic.  The proposal is to experimentally and theoretically investigate the behaviour of contaminant concentration values using the Expected Mass Fraction Function.