环境空气 滤膜介质上颗粒物质量测量 β射线吸收法

[中文适用范围]： 本国际标准描述了一种测量环境空气中参与物质质量的方法，该方法基于颗粒物质对 β 射线的吸收。 本方法适用于城市、农村或工业区大气中每立方米几微克至每立方米几毫克浓度的测定。 该方法的质量检测下限通常为过滤器每平方厘米表面积 S 15 μg 至 30 μg 的沉积质量。 这意味着，对于采样时间 t 为 3 h、流量 q 为 1 m/h，浓度检测限范围在 5 μg/m 至 10 μg/m 之间，计算如下： 浓度 (μg/cm)·S (cm)/q(m/h)·1/t(h) 取样技术不包括在本国际标准范围内。 注：颗粒物的浓度是通过将沉积在滤带或单个过滤器上的质量除以已知的空气采样量来计算的。 然而，浓度取决于所使用的采样技术，例如采样入口的设计。 通常，对于环境空气颗粒采样，大颗粒通过尺寸选择性入口（例如级联冲击器或旋风过滤器）过滤掉。 颗粒尺寸限制由采样头的特性决定。 [外文原描述]： This International Standard describes a method for the measurement of the mass of particulate matter in ambient air and is based on the absorption of beta rays by the particulate matter. This method applies to the determination of concentrations ranging from a few micrograms per cubic metre to a few milligrams per cubic metre contained in the atmospheres of urban, rural or industrial areas. The lower mass detection limit of the method is usually 15 μg to 30 μg of deposited mass per square centimetre of surface area, S , of the filter. This means, for a sampling time t of 3 h and a flowrate q of 1 m3/h, that the concentration detection limit ranges between 5 μg/m3 and 10 μg/m3, computed as follows: Sampling techniques are not included in the scope of this International Standard. NOTE The concentration of particulate matter is calculated by dividing the mass deposited on a filter tape or individual filter, by the known volume of air sampled. However, concentration is dependent on the sampling technique used, for example, the design of the sampling inlet. Normally, for ambient-air particle sampling, large particles are filtered out by means of a sizeselective inlet (for example cascade impactor or cyclone filtration). The particle size limit is defined by the characteristics of the sampling head.