Impact of agricultural straw open-field burning on concentrations of six criteria air pollutants in China.

Agricultural straw open-field burning (ASOB) is a major source of fine particles and carbonaceous aerosols, particularly in China, India, and Southeast Asia. However, the exposure-lag-response relationship between straw burning and urban air pollution in China remains insufficiently investigated. This study compiled satellite-based ASOB data along with daily meteorological and air pollution monitoring data for 156 Chinese cities from 2015 to 2020. The ASOB points detected by the Moderate Resolution Imaging Spectroradiometer (MODIS) were identified as exposure events, and their exposure-lag-response relationships with daily pollutant levels were elucidated using distributed lag nonlinear models. The nation-level estimate of the impact of ASOB points on urban air quality was obtained by a meta-analysis. The results revealed significant short-term elevation in the daily concentrations of six pollutants. Each increase of 10 straw burning points is associated with an increase of 8.89, 8.52, 8.17, 2.43, and 0.84 μg/m3 in PM10, O3, PM2.5, NO2, and SO2, respectively, and an increase of 0.048 mg/m3 in CO with a lag of 0-3 days. Regional and seasonal ASOB variations and their effects were observed, revealing a pronounced effect in East China, particularly from October to December. ASOB contributed 4.54 % of O3 and 2.72 % of PM2.5 concentrations in air pollution waves in the high-intensity ASOB burning seasons. This study highlights the adverse impact of open-field straw burning on air quality, even under China's strict ASOB ban, providing scientific evidence for future assessments of the cost-effectiveness of straw-burning bans and policy refinements.