Online observation of PM2.5 during a persistent haze in the Yangtze River Delta: chemical components, health effect and light extinction

Abstract

Haze impacts visibility and health. To understand the effects of haze chemical components on health risks and atmospheric optics, PM_2.5 chemical components during a haze event in Jiaxing (Dec 15, 2023–Jan 8, 2024) were analyzed. NO₃⁻ was the main component of water-soluble ions (WSIs) (45.07 %–58.20 %). Primary organic carbon (POC) was the main component of total carbon (TC) (55.12 %–78.21 %). In the clean and developing stages, Fe was the main component of metal. K was the main component in the maintenance and dissipating stages. In the developing stage, NO₃⁻ and secondary organic carbon (SOC) concentrations increased sharply, 3.86 and 18.75 times that of the previous stage. Among them, the increase of NO₃⁻ played an essential role in light extinction. In the maintenance stage, SO₄²⁻ played a more critical role. Its contribution to PM_2.5 was 1.68 times that of the previous stage, and the contribution of sulfate (Sul) to light extinction was 1.98 times that of the previous stage. The decrease in NO₃⁻ concentration mainly caused haze dissipating, but the contribution of Nitrate (Nit) to light extinction increased (62.30 %). From clean to maintenance stage, the contribution of WSIs to PM_2.5 increased, while that of TC decreased. At the same time, the enrichment factors (EF) of heavy metals such as Fe, Ca, and Zn, as well as the non-carcinogenic and carcinogenic risk for kids, decreased but increased in the dissipating stage. The non-carcinogenic and carcinogenic risk for adults increased in the developing stage. Kids were more sensitive to PM_2.5 than adults.