Generally speaking, the precursors of ozone (O 3 ), nitrogen oxides and volatile organic compounds are very low in desert areas due to the lack of anthropogenic emissions and natural emissions, and thus O 3 concentrations are relatively low. However, high summer background concentrations of about 100 pg/m 3 or 60 ppb were found in the Alxa Desert in the highland of northwest China based on continuous summer observations from 2019 to 2021, which was higher than the most of natural background areas or clean areas in world for summer O 3 background concentrations. The high O 3 background concentrations were related to surface features and altitude. Heavy -intensity anthropogenic activity areas in desert areas can cause increased O 3 concentrations or pollution, but also generated O 3 depleting substances such as nitrous oxide, which eventually reduced the regional O 3 baseline values. Nitrogen dioxide (NO 2 ) also had a dual effect on O 3 generation, showing promotion at low concentrations and inhibition at high concentrations. In addition, sand -dust weather reduced O 3 clearly, but O 3 eventually stabilized around the background concentration values and did not vary with sand -dust particulate matter. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.