TY - JOUR A1 - Liu, X. A1 - Ran, L. A1 - Lin, W. A1 - Xu, X. A1 - Ma, Z. A1 - Dong, F. A1 - He, D. A1 - Zhou, L. A1 - Shi, Q. A1 - Wang, Y. T1 - Measurement report: Variations in surface SO2 and NOx mixing ratios from 2004 to 2016 at a background site in the North China Plain JO - Atmos. Chem. Phys. J1 - ACP VL - 22 IS - 10 SP - 7071 EP - 7085 Y1 - 2022/06/01 PB - Copernicus Publications SN - 1680-7324 UR - https://acp.copernicus.org/articles/22/7071/2022/ L1 - https://acp.copernicus.org/articles/22/7071/2022/acp-22-7071-2022.pdf DO - 10.5194/acp-22-7071-2022 ER -