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Table 1.

Seasonal change rates of O3 levels at GC, BJ, SJZ, and CNEMC NCP sites during 2013–2019

SitesRates (ppb yr–1)AnnualSpringSummerAutumnWinter
BD GC –1.0 0.5 –1.7 –2.1a 0.6a 
Urban 1.3 2.7 2.8 0.4 –0.5 
BJ North suburban 0.8 0.8 0.9 0.5 0.3 
Urban 0.8 0.8 1.1 0.7 0.3 
West suburban 0.4 0.3 0.4 0.4 0.3 
SJZ Suburban 0.9 1.3 1.9 0.5 0.1 
Urban 1.9 2.3 3.7 1.0 0.4 
Rural (mountain site) –0.7 –0.2 –1.1 –0.0 –1.0 
NCP P < 0.05 2.4 (0.5–5.6)b 2.4 (0.8–5.4)b 3.5 (1.3–7.3)b 2.1 (0.9–4.1)b 1.4 (0.6–2.8)b 
P > 0.05 upward 0.0–2.9b 0.1–3.2b 0.1–4.2b 0.0–2.0b 0.1–1.9b 
downward –2.3 to 0.0b –0.4 to –0.1b –1.1 to –0.1b –3.3 to –0.1b –2.8 to 0.0b 
NDown/NAllc 5/128 4/73 2/73 18/124 11/129 
SitesRates (ppb yr–1)AnnualSpringSummerAutumnWinter
BD GC –1.0 0.5 –1.7 –2.1a 0.6a 
Urban 1.3 2.7 2.8 0.4 –0.5 
BJ North suburban 0.8 0.8 0.9 0.5 0.3 
Urban 0.8 0.8 1.1 0.7 0.3 
West suburban 0.4 0.3 0.4 0.4 0.3 
SJZ Suburban 0.9 1.3 1.9 0.5 0.1 
Urban 1.9 2.3 3.7 1.0 0.4 
Rural (mountain site) –0.7 –0.2 –1.1 –0.0 –1.0 
NCP P < 0.05 2.4 (0.5–5.6)b 2.4 (0.8–5.4)b 3.5 (1.3–7.3)b 2.1 (0.9–4.1)b 1.4 (0.6–2.8)b 
P > 0.05 upward 0.0–2.9b 0.1–3.2b 0.1–4.2b 0.0–2.0b 0.1–1.9b 
downward –2.3 to 0.0b –0.4 to –0.1b –1.1 to –0.1b –3.3 to –0.1b –2.8 to 0.0b 
NDown/NAllc 5/128 4/73 2/73 18/124 11/129 

Bold numbers are rates that passed the 95% significant test.

arepresents change rates calculated for 2013–2018.

bvariation range of the O3 change rates observed at distinct sites in the NCP.

cNDown represents the number of sites with downward O3, while NAll is the total number of sites selected.

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