Health risk assessment of trace elements of ambient PM_2.5 under monsoon patterns

In order to identify the contribution to health risk derived from various emission sources, this study investigated monsoon variations in PM_2.5 mass and concentrations of the associated trace elements in a region with complex pollution sources in central Taiwan. This study applied the Chemical Mass Balance model to analyze the source contribution of PM_2.5. The source apportionment to obtain the risk contribution of different sources were conducted for different monsoon periods according to the monsoon patterns. In this way, the contributions of individual sources and chemicals to health risk under different monsoon types can be understood to support development of effective control strategies. Among the top contributors of PM_2.5 during the north-east monsoon were Secondary Aerosol 28.93% >Coal Boiler 19.82% >Crustal Dust 15.99%; in south-west monsoon were Coal Boiler 37.29% >Traffic Emission 21.19% >Secondary Aerosol 17.84%. The total risk of cancer was above the acceptable risk (3.07 × 10^-6), while the non-carcinogenic risk was within the acceptable range (0.262). The variation in the concentration and composition of PM_2.5 was related to the change of monsoon type. During the north-east monsoon, the air mass had a long transmission distance and the PM_2.5 concentration was relatively high. During the south-west monsoon, the air mass had a short transmission distance and the composition was mainly influenced by nearby emission sources, which resulted in higher risk due to chemical characteristics. To provide sound air quality management, attention should be paid to the composition of PM_2.5 in addition to its concentration.