Which of the following methods is commonly used for measuring air quality?

The choice of collection and weighing refers to a method often used in air quality measurement, specifically for particulate matter. This method involves collecting air samples onto filters and subsequently weighing the filters before and after sampling to determine the mass of particulate matter captured. This process allows for the quantification of the concentration of particulates in the air, which is vital for assessing air quality and the potential impact on public health and the environment.

Other methods listed, while relevant to air quality measurement, serve different purposes or are less commonly used for specific air quality assessments. For instance, gas chromatography is primarily used for separating and analyzing compounds in gaseous samples, while spectrophotometry is typically employed for measuring the intensity of light absorption within a sample to detect specific pollutants. Flame ionization is a technique used mainly for detecting volatile organic compounds in gaseous samples, but it is less utilized for general air quality measurement than the collection and weighing method.