posted on 2021-02-12, 15:03authored byTong Sha, Xiaoyan Ma, Huanxin Zhang, Nathan Janechek, Yanyu Wang, Yi Wang, Lorena Castro García, G. Darrel Jenerette, Jun Wang
Nitrogen oxides (NOx) are a key precursor
in O3 formation. Although stringent anthropogenic NOx emission controls have been implemented
since the early 2000s in the United States, several rural regions
of California still suffer from O3 pollution. Previous
findings suggest that soils are a dominant source of NOx emissions in California; however, a statewide assessment
of the impacts of soil NOx emission (SNOx) on air quality is still lacking. Here we
quantified the contribution of SNOx to
the NOx budget and the effects of SNOx on surface O3 in California during
summer by using WRF-Chem with an updated SNOx scheme, the Berkeley Dalhousie Iowa Soil NO Parameterization
(BDISNP). The model with BDISNP shows a better agreement with TROPOMI
NO2 columns, giving confidence in the SNOx estimates. We estimate that 40.1% of the state’s total
NOx emissions in July 2018 are from soils,
and SNOx could exceed anthropogenic sources
over croplands, which accounts for 50.7% of NOx emissions. Such considerable amounts of SNOx enhance the monthly mean NO2 columns by 34.7% (53.3%)
and surface NO2 concentrations by 176.5% (114.0%), leading
to an additional 23.0% (23.2%) of surface O3 concentration
in California (cropland). Our results highlight the cobenefits of
limiting SNOx to help improve air quality
and human health in rural California.