Ca  2+ Cl  - HNO3 HNO3- K  + Mg  2+ Na  + NH3 NH4+ NO3- NOx NOy O3 PM2.5 SO2 SO42-

Figure 2-a 2015 Quality Control Check Summary

Figure 2-a Download Figure

Figure 2-3 Trends in Fourth Highest DM8A O3 Concentrations

Western Reference Sites

Figure 2-3 Western Download Image

Eastern Reference Sites

Figure 2-3 Eastern Download Image

Note:
  1 The NAAQS was revised from 0.075 ppm to 0.070 ppm on October 15, 2015.
  2 To attain this standard, the 3-year average of the fourth highest DM8A O3 concentrations measured at each monitor within a specified area must not exceed 0.070 ppm or 70 parts per billion (ppb) in practice (effective December 28, 2015). Ozone concentrations are commonly presented in units of ppb.