High-resolution observation per 1.5 h revealed prominent time-dependent daily contamination variations of p-phenylenediamine (PPD) antioxidants and their quinone derivatives PPDQs in PM2.5 from central China

p-Phenylenediamine (PPD) antioxidants and their quinone derivatives (PPDQs), as hot-spot novel contaminants in recent years, have been detected in air fine particulate matters (PM_2.5) in multiple regions. However, current research all discussed the pollution of PPDs and PPDQs based on the collected PM_2.5 samples at least in one day (23.5 h). In this work, an innovative study was conducted to investigate their precise daily pollution characteristics and health risks based on high-resolution collected PM_2.5 samples every 1.5 hours in one week in Zhengzhou, a megacity continuously suffers from serious air contamination in central China. The composition patterns and sources of PPDs and PPDQs were discovered and more serious contamination of them were both found at the day-time (07:00-19:00). Almost all daily time intervals with relatively high pollution levels of PPDs and PPDQs were commuting time for majority of workers, which was possibly because of increased rubber tire abrasion induced by huge traffic volume. The highest daily adults' inhalation risks were also found in 11:30-13:00 and 16:00-17:30 for PPDs and PPDQs in PM_2.5, respectively. Current study builds the relationship between pollution status of such novel pollutants and human activities, and possibly guides people in central China to take precautions to protect themselves from environmental toxicants at special daily time.