Non-agricultural source dominates the ammonium aerosol in the largest city of South China based on the vertical δ15N measurements

Zixi Chen, Chenglei Pei, Junwen Liu, Xiangyun Zhang, Ping Ding, Lan Dang, Zheng Zong, Fan Jiang, Lili Wu, Xi Sun, Shengzhen Zhou, Yanlin Zhang, Zhisheng Zhang, Junyu Zheng, Chongguo Tian, Jun Li, Gan Zhang