A quantitative understanding of total OH reactivity and ozone production in a coastal industrial area during the Yokohama air quality study (AQUAS) campaign of summer 2019

Field measurements performed in the Keihin coastal industrial area during summer 2019 were used to characterize the air quality and ozone production potential. The total hydroxyl radical (OH) reactivity was found to be moderate, peaking with a 2-h average of 29.0 s(-1), corresponding to an OH lifetime of similar to 34 ms. The average hourly total OH reactivity was 11.4 +/- 5.2 s(-1) (average +/- standard deviation), and the measured OH sinks (from over 90 trace species) accounted for 92.3% of the total OH reactivity. Compared with a previous series of campaigns in urban/suburban Japan, this field work investigated an area often overlooked for atmospheric observations and found the smallest missing OH reactivity (on average, 0.88 s(-1)). The near-zero missing OH reactivity indicated that photochemical procedures were less important to the Yokohama air quality study (AQUAS-Yokohama) than the ubiquitous substantial secondary products in other areas. This study also demonstrated that oceanic air masses may quickly flush coastal industrial areas and that a limited activity of photochemistry due to elevated NOx effectively terminates OH radical recycling. A comparison with other campaigns in Japan exhibited a positive correlation with oxidants (ozone and formaldehyde), indicating secondary products have a critical role in explaining missing OH reactivity. The ozone production potential was corresponding to a volatile organic compound (VOC)-limited regime, while the missing OH reactivity led to an similar to 8% increase in ozone formation. Finally, a positive correlation was found between the ozone production rate and the reactivity ratio between VOCs and NOx, in both the current study and various other field campaigns in urban areas.

Automated summary

Field measurements in the Keihin coastal industrial area during summer 2019 characterized air quality and ozone production potential with moderate OH reactivity and minimal missing OH reactivity compared to other campaigns. Oceanic air masses may influence coastal industrial areas, while ozone production rate shows a positive correlation with the reactivity ratio between VOCs and NOx.