18.3 What Are the PM2.5 Measurement versus Model Concentration Issues?

Ambient measurements are needed to perform a model evaluation. Historically, ozone

model evaluations have used routinely measured ambient data (e.g. ozone) collected on a

continuous basis. The measurements tend to be of high frequency and quality. Conversely, PM2.5

and PM2.5 component measurements are (mostly) filter based measurements which have relatively

long sampling times (usually 24 hours) and aren't collected every day (usually once every three or

42 For predicted/observed comparisons, organic carbon is preferred over organic carbon

mass to allow for transparency between model predictions and observed measurements. Organic

carbon mass may include hydrogen, oxygen, and other components.

43 Other inorganic particulate matter can contribute up to 10% of PM2.5 mass in certain

locations. Unspeciated inorganic PM (sometimes referred to as “other PM”) is often used

interchangeably with “crustal” or “soil” PM. The term “soil” usually refers to the specific

definition of soil from the IMPROVE program. “Other primary (inorganic) PM” includes heavy

metals and other inorganic species in addition to those commonly found in soil.

six days). Speciated data play an especially important role, as the deterministic models predict

exact chemical components which can be compared to some of the corresponding measured

analytes. In addition, there are known positive and negative sampling artifacts as well as analysis

artifacts associated with FRM and speciation monitors. For example, FRM monitors do not

measure all of the PM2.5 in the air, and the speciation samplers don't measure PM2.5 in the same

way as the FRM monitors (Frank, 2006). Due to the complex nature of the measurements, a basic

understanding of the various PM2.5 and speciation monitoring technology and measurements are

needed before undertaking a model evaluation. This section attempts to address the range of

measurements and measurement issues associated with PM2.5 and its components.

Table 18.1 summarizes many of the PM2.5 species measurements and networks and lists

sampling time and measurement issues. This data will commonly be used as part of an

operational evaluation.


n851 - n852 - n853 - n854 - n855 - n856 - n857 - n858 - n859 - n860 - n861 - n862 - n863 - n864 - n865 - n866 - n867 - n868 - n869 - n870 - n871 - n872 - n873 - n874 - n875 - n876 - n877 - n878 - n879 - n880 - n881 - n882 - n883 - n884 - n885 - n886 - n887 - n888 - n889 - n890 - n891 - n892 - n893 - n894 - n895 - n896 - n897 - n898 - n899 - n900


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