ABSTRACT
In this study, the levels of fine particulate matter (PM2.5), polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) in PM2.5 samples were determined from 2020 to 2021 in Singapore. For analysis convenience, the sampling period was classified according to two monsoon periods and the inter-monsoon period. Considering Singapore's typically tropical monsoon climate, the four seasons were divided into the northeast monsoon season (NE), southwest monsoon season (SW), presouthwest monsoon season (PSW) and prenortheast monsoon season (PNE)). The PM2.5 concentration reached 17.1 +/- 8.38 mu g/m(3), which was slightly higher than that in 2015, and the average PAH concentration continuously declined during the sampling period compared to that reported in previous studies in 2006 and 2015. This is the first report of NPAHs in Singapore indicating a concentration of 13.1 +/- 10.7 pg/m(3). The seasonal variation in the PAH and NPAH concentrations in PM2.5 did not obviously differ owing to the unique geographical location and almost uniform climate changes in Singapore. Diagnostic ratios revealed that PAHs and NPAHs mainly originated from local vehicle emissions during all seasons. 2-Nitropyrene (2-NP) and 2-nitrofluoranthene (2-NFR) in Singapore were mainly formed under the daytime OH-initiated reaction pathway. Combined with airmass backward trajectory analysis, the Indonesia air mass could have influenced Singapore's air pollution levels in PSW. However, these survey results showed that no effect was found on the concentrations of PAHs and NPAHs in PM2.5 in Indonesia during SW because of Indonesia's efforts in the environment. It is worth noting that air masses from southern China could impact the PAH and NPAH concentrations according to long-range transportation during the NE. The results of the total incremental lifetime cancer risk (ILCR) via three exposure routes (ingestion, inhalation and dermal absorption) for males and females during the four seasons indicated a low long-term potential carcinogenic risk, with values ranging from 10(-10) to 10(-7). This study systematically explains the latest pollution conditions, sources, and potential health risks in Singapore, and comprehensively analyses the impact of the tropical monsoon system on air pollution in Singapore, providing a new perspective on the transmission mechanism of global air pollution.
ABSTRACT
Between 2018 and 2022, a total of 231 PM2.5 samples were collected in Nantong, China, and analyzed online for 16 US EPA PAHs utilizing a variety of analytical methodologies, including high-performance liquid chromatography data analysis, principal component analysis, and characteristic ratio analysis. The seasonal variation and pollution characteristics of 16 PAHs in PM2.5 over a long period in Nantong, China, were analyzed, and correlations and traceability changes with a variety of emission sources were established. Additionally, health assessment models for BaP equivalent concentration, daily exposure dose, lifetime excess risk of cancer, and life expectancy loss were constructed for various ages and genders. The results indicated that the total number of days with BaP concentrations less than the national limit standard of 1.0 ng/m(3) was 60.17% (139/231), with rates of 25.40%, 35.71%, and 94.05% from 2019 to 2021, respectively;the total concentration range of 16 PAHs demonstrated a downward trend, but pollution was relatively severe in winter. The seasonal variation showed winter > autumn > spring > summer. The detection rates of 4 and 5 rings were generally high and fluctuated between dropping and increasing. Principal factor analysis and characteristic ratio traceability analysis indicated that PAH pollution is primarily caused by local coal-fired sources and traffic emissions, with a new trend of biomass combustion. Furthermore, BaP remains the primary contributor to carcinogenic factors, and the health risk is higher in females than in males, and in adults than in children. A low level of PAHs in the air may have health benefits. Traffic control and flow restrictions, as well as production restrictions, are all part of Nantong's COVID-19 pandemic prevention and control policies. These policies contributed to PAH risk prevention and control, as well as pollution reduction.