Ca  2+ Cl  - HNO3 //HNO3- K  + Mg  2+ Na  + NH3 NH4+ NHx NO3- NOx NOy NOz O3 PM2.5 PM10 SO2 SO42- SOx µg/m  3 ha  -1 yr  -1

Figure 1 CASTNET and AMoN Sites Operational during 2021

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Figure 9 Trends in Annual Mean NH+ 4 Concentrations

Western Reference Sites

Figure 9 Western Download Image

Eastern Reference Sites

Figure 9 Eastern Download Image
Blackwater, MD (BWR139)

Blackwater, MD (BWR139)

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  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.

Figure 2-1 Three-year Averages of Fourth Highest DM8A O3 Concentrations for 2015–2017

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Figure 2-3 Trends in Fourth Highest DM8A O3 Concentrations

Eastern Reference Sites

Figure 2-3 Eastern Download Image

Western Reference Sites

Figure 2-3 Western Download Image