Atmospheric particulate-bound mercury (PBM10) in a Southeast Asia megacity: Sources and health risk assessment

Total gaseous mercury in Kathmandu, a South Asian metropolis: Temporal variations, sources apportionment and health risk assessment

South Asia is a global hotspot of air pollution gaining attention due to its severe implications, in which atmospheric mercury (Hg) could cause detrimental health effects in metropolitan areas. In this study, first-time year-round (January - December 2019) mean total gaseous mercury (TGM) concentration at Kathmandu, Nepal - a sub-tropical city in South Asia was reported at 9.9 ± 10.0 ng m-3. Seasonal TGM variation at Kathmandu showed highest concentration in winter (16.8 ± 16.9 ng m-3) and lowest in summer (2.9 ± 2.1 ng m-3). Generally higher daytime TGM concentration as opposed to night-time TGM indicated Hg build-up within atmospheric boundary layer due to low wind speed and high humidity. Events with high wind speed (> 30 m s-1) induced regional pollutant transport from nearby brick kilns and cement factories. Principal component analysis associated a major part of TGM with PM2.5 and CO and indicated the remarkable influence of fuel combustion and vehicular emissions. Backward trajectory and potential source contribution factor analysis further indicate the impact of regional Hg emissions and transboundary emissions from India towards Nepal, which expands beyond the Himalayas and the Tibetan Plateau. Prominent low-grade coal burning and kilning activities in winter spiked up TGM concentrations, resulting in the highest health quotient (HQ = 0.24) value, which could significantly impact public health. Our study presented the most comprehensive set of continuous annual atmospheric Hg monitoring data from Nepal in the South Asian region. The results serve as a baseline for regional atmospheric Hg levels and offer a critical reference for assessing and addressing air pollution concerns in Nepal as well as throughout South Asia.

Planetary boundaries transgressions: A review on the implications to public health

This literature review systematically examines the impacts of violating planetary boundaries from 2009 to 2023, emphasizing the implications for human health. Planetary boundaries define safe operational limits for Earth's systems, and their transgression poses significant threats to environmental stability and public health. This paper reviews extensive research on the health effects of breaches in these boundaries, including climate change, biodiversity loss, freshwater use, and aerosol loading. The review integrates findings from numerous studies, providing a critical overview of health impacts across various global regions. The analysis underscores the intricate links between planetary boundaries breaching impacts, highlighting urgent policy and governance challenges. The study's outcomes aim to inform policymakers, businesses, and communities, promoting sustainable development and resilience in the face of escalating global challenges.

Distribution and bioavailability of mercury in size-fractioned atmospheric particles around an ultra-low emission power plant in Southwest China

Ultra-low emission (ULE) technology retrofits significantly impact the particulate-bound mercury (Hg) emissions from coal-fired power plants (CFPPs); however, the distribution and bioavailability of Hg in size-fractioned particulate matter (PM) around the ULE-retrofitted CFPPs are less understood. Here, total Hg and its chemical speciation in TSP (total suspended particles), PM10 (aerodynamic particle diameter ≤ 10 µm) and PM2.5 (aerodynamic particle diameter ≤ 2.5 µm) around a ULE-retrofitted CFPP in Guizhou Province were quantified. Atmospheric PM2.5 concentration was higher around this ULE-retrofitted CFPP than that in the intra-regional urban cities, and it had higher mass Hg concentration than other size-fractioned PM. Total Hg concentrations in PM had multifarious sources including CFPP, vehicle exhaust and biomass combustion, while they were significantly higher in autumn and winter than those in other seasons (P < 0.05). Regardless of particulate size, atmospheric PM-bound Hg had lower residual fractions (< 21%) while higher HCl-soluble fractions (> 40%). Mass concentrations of exchangeable, HCl-soluble, elemental, and residual Hg in PM2.5 were higher than those in other size-fractioned PM, and were markedly elevated in autumn and winter (P < 0.05). In PM2.5, HCl-soluble Hg presented a significantly positive relationship with elemental Hg (P < 0.05), while residual Hg showed the significantly positive relationships with HCl-soluble Hg and elemental Hg (P < 0.01). Overall, these results suggested that atmospheric PM-bound Hg around the ULE-retrofitted CFPP tends to accumulate in finer PM, and has higher bioavailable fractions, while has potential transformation between chemical speciation.

Spatiotemporal variation and inter-transport of atmospheric speciated mercury between Kaohsiung Harbor and neighboring urban areas

This study investigated the spatiotemporal variation, gas-particle partition, and source resolution of atmospheric speciation mercury (ASM) in Kaohsiung Harbor and neighboring Metro Kaohsiung. Four sampling sites were selected to determine the pollution characteristics and inter-transport of ASM between the port and urban areas. The yearly average GEM, GOM, and PBM concentrations were 7.13 ± 2.2 ng/m3, 331 ± 190 pg/m3, and 532 ± 301 pg/m3, respectively. Notably, GEM emerged as the predominant ASM species (85-94%), primarily originating from anthropogenic emissions from the harbor area and nearby industrial complex. The study revealed a distinct seasonal variation in ASM concentrations in the Kaohsiung Area in the following order: winter > fall > spring > summer. Concerning spatial distribution, ASM concentrations in the port areas were generally higher than those in the urban areas. This disparity was chiefly attributed to the influence of the prevailing winds, local sources, and atmospheric dispersion. Backward trajectory simulation revealed that polluted air masses blown from the northeast in winter and spring, moving along the western in-land part of Taiwan Island, were likely influenced by local sources and long-range transport (LRT). In summer, air pollutants originating from the south were likely transported from the coastal industrial sources. During fall, air masses blown from the western offshore waters transported air pollutants from Kaohsiung Harbor to neighboring Metro Kaohsiung. The results obtained from principle component analysis (PCA) indicated that primary sources in the port areas included ship emissions, vehicular exhausts, and nearby industrial complex, which align with the primary source factors identified by positive matrix factorization (PMF), which were mobile sources and coal-fired industrial boilers. Meanwhile, mobile sources and sulfur-containing fuel/waste combustion were identified as the primary sources in the urban areas.

Long-Range Atmospheric Mercury Transport from Across East Asia to a Suburban Coastal Area in Southern Vietnam

Exports of atmospheric mercury (Hg) from continental East Asia, a major Hg emitter in the globe, have been reported by several studies in neighboring countries such as Japan and Korea. Nonetheless, studies concerning this topic in Southeast Asia (SEA) countries are still limited. Accordingly, gaseous elemental mercury (GEM) has been measured from Can Thanh High School (CTHS), a suburban coastal site in southern Vietnam to study its characterization and discover the evidence of Hg trans-boundary transport from regional sources (e.g., East Asia). Data collected in July, August, and October 2022 were used in this study, and the overall GEM concentration was 1.61 ± 0.32 ng m-3. The GEM levels were higher in October than in July and August, potentially due to the discrepancy in air mass transport patterns induced by tropical monsoon and source origins of Hg. MERRA-2, backward trajectories, and CALIPSO images revealed the trans-boundary air pollution from continental East Asia to southern Vietnam, evidenced by significantly elevated (> 30%) atmospheric Hg concentrations as well as other air pollutants when the plume arrived at CTHS. Furthermore, our results also imply that atmospheric Hg exported from East Asia could influence large areas in SEA, suggesting the need for more studies in various SEA countries in the upcoming future. This study illustrated the influence of regional Hg emissions on local atmospheric Hg pollution and provided data to improve knowledge of the Hg biogeochemical cycle in SEA.