Updated ozone absorption cross section will reduce air quality compliance

TY - JOUR

T1 - Updated ozone absorption cross section will reduce air quality compliance

AU - Sofen, E. D.

AU - Evans, M. J.

AU - Lewis, A. C.

N1 - © Authors 2015. This content is made available by the publisher under a Creative Commons CC BY Licence

PY - 2015/12/10

Y1 - 2015/12/10

N2 - Photometric ozone measurements rely upon an accurate value of the ozone absorption cross section at 253.65 nm. This has recently been reevaluated by Viallon et al. (2015) as 1.8 % smaller than the accepted value (Hearn, 1961) used for the preceding fifty years. Thus, ozone measurements that applied the older cross section systematically underestimate the amount of ozone in air. We correct the reported historical surface data from North America and Europe and find that this modest change in cross section has a significant impact on the number of locations that are out of compliance with air quality regulations if the air quality standards remain the same. We find 18, 23, and 20 % increases in the number of sites that are out of compliance with current US, Canadian, and European ozone air quality health standards for the year 2012. Should the new cross section value be applied, it would impact attainment of air quality standards and compliance with relevant clean air acts, unless the air quality target values themselves were also changed proportionately. We draw attention to how a small change in gas metrology has a global impact on attainment and compliance with legal air quality standards. We suggest that further laboratory work to evaluate the new cross section is needed and suggest three possible technical and policy responses should the new cross section be adopted.

AB - Photometric ozone measurements rely upon an accurate value of the ozone absorption cross section at 253.65 nm. This has recently been reevaluated by Viallon et al. (2015) as 1.8 % smaller than the accepted value (Hearn, 1961) used for the preceding fifty years. Thus, ozone measurements that applied the older cross section systematically underestimate the amount of ozone in air. We correct the reported historical surface data from North America and Europe and find that this modest change in cross section has a significant impact on the number of locations that are out of compliance with air quality regulations if the air quality standards remain the same. We find 18, 23, and 20 % increases in the number of sites that are out of compliance with current US, Canadian, and European ozone air quality health standards for the year 2012. Should the new cross section value be applied, it would impact attainment of air quality standards and compliance with relevant clean air acts, unless the air quality target values themselves were also changed proportionately. We draw attention to how a small change in gas metrology has a global impact on attainment and compliance with legal air quality standards. We suggest that further laboratory work to evaluate the new cross section is needed and suggest three possible technical and policy responses should the new cross section be adopted.

UR - http://www.scopus.com/inward/record.url?scp=85042581749&partnerID=8YFLogxK

U2 - 10.5194/acp-15-13627-2015

DO - 10.5194/acp-15-13627-2015

M3 - Article

AN - SCOPUS:84949781615

SN - 1680-7316

VL - 15

SP - 19537

EP - 19551

JO - Atmospheric Chemistry and Physics

JF - Atmospheric Chemistry and Physics

IS - 14

ER -