Enhanced impacts evaluation of Typhoon Sinlaku (2020) on atmospheric microplastics in South China Sea during the East Asian Summer Monsoon.

Atmospheric transport is an important pathway through which microplastics (MPs) are widely exchanged between marine and terrestrial environments. However, the impacts of frequent extreme weather events, such as typhoons, on atmospheric MPs is poorly understood. To address this issue, we collected suspended atmospheric MPs (SAMPs) and rainfall samples in the South China Sea during Typhoon Sinlaku (2020). Our results revealed a higher abundance of suspended MPs (1.05 ± 0.55 n/100 m3) during the typhoon than in the pre-typhoon period (0.59 ± 0.48 n/100 m3). Nine polymer types were identified by micro-FTIR, among which the dominant were polyethylene terephthalate (PET, 62.82%) and polypropylene (PP, 19.23%). Moreover, rainfall appeared more inclined to remove larger sizes, more colors and more polymer types of MPs from the atmosphere. The trajectory source-receptor plot indicated that the typhoon significantly changed the pathway of MP transport in the atmosphere, including the direction and distance. To our knowledge, this is the first study to elucidate the impact of typhoons on atmospheric MP transportation. Our results indicate that airborne MPs may pose unexpected ecological risks to marine and coastal ecosystems due to their increased abundance from more distant sources, resulting from typhoon events.

Occurrence, potential sources and risks of organophosphate esters in the high-elevation region, Tibet, China.

Organophosphate esters (OPEs) are widely used flame retardants that are frequently released into the environment, causing potential harm to humans and ecosystems. Tibet is located on the Tibetan Plateau, known as the "roof of the world", but the occurrence of OPEs in Tibet remains unclear. This is the first report of the occurrence, potential sources and risks of 12 OPEs in water, soil, sediment and snow from Xainza, a typical town at high-elevation in Tibet (average elevation = 4700 m). Ten OPEs were observed, with ∑OPE concentrations of 46.45-1744.73 ng/L in surface water, 29.74-73.85 ng/g in soil, and 13.30-32.23 ng/g in sediment. Moreover, the mean ∑OPE concentration in snow was 413.90 ng/L. Tris (2-chloroethyl) phosphate (TCEP) and tris (2-chloroisopropyl) phosphate (TCPP) were the main OPEs in surface water and snow, while 2-ethylhexyl diphenyl phosphate (EHDPP) was dominant in soil and sediment. Local human activities and long-distance atmospheric transport may be the main sources of OPEs in Xainza. The assessment of ecological risk indicated that EHDPP in soil poses potential risk. The occurrence of OPEs in Xainza showed that more attention should be paid to persistent organic pollutants in high-elevation regions.

Coastal meteorology on the dispersion of air particles at the Bachok GAW Station.

Meteorology over coastal region is a driving factor to the concentration of air particles and reactive gases. This study aims to conduct a research to determine the level of year-round air particles and the interaction of the meteorological driving factors with the particle number and mass in 2018, which is moderately influenced by Southeast Asian haze. We obtained the measurement data for particle number count (PNC), mass, reactive gases, and meteorological factors from a Global Atmospheric Watch (GAW) station located at Bachok Marine Research Center, Bachok, Kelantan, Malaysia. For various timeseries and correlation analyses, a 60-second resolution of the data has been averaged hourly and daily and visualized further. Our results showed the slight difference in particle behavior that is either measured by unit mass or number count at the study area. Diurnal variations showed that particles were generally high during morning and night periods. Spike was observed in August for PM2.5/PNC2.5 and PM10/PNC10 and in November for PMCoarse/PNCCoarse. From a polar plot, the particles came from two distinct sources (e.g., seaside and roadside) at the local scale. Regional wind vector shows two distinct wind-blown directions from northeast and southwest. The air mases were transported from northeast (e.g., Philippines, mainland China, and Taiwan) or southwest (e.g., Sumatra) region. Correlation analysis shows that relative humidity, wind direction, and pressure influence the increase in particles, whereas negative correlation with temperature is observed, and wind speed may have a potential role on the decline of particle concentration. The particles at the study area was highly influenced by the changes in regional wind direction and speed.

Potential sources, scavenging processes, and source regions of mercury in the wet deposition of South Korea.

In this study, the potential sources, scavenging processes, and emission regions for Hg in wet deposition were investigated in rural (Jeju), suburban (Gwangju), and urban sites (Incheon and Seoul) of South Korea. The annual volume-weighted mean concentrations of Hg in wet deposition were four to five times higher in Incheon (16.6 ng L-1) and Seoul (22.5 ng L-1) than in Jeju (4.0 ng L-1) and Gwangju (4.1 ng L-1). The variations in the Hg concentrations in wet deposition of Jeju and Gwangju were related to Cl-, Na+, Mg2+, and K+ originating from marine and crustal sources, and those in Incheon and Seoul were related to SO42-, NO3-, and NH4+ emitted from anthropogenic sources. The below-cloud scavenging was considered a major inclusion process of Hg in Jeju and Gwangju, while the within-cloud scavenging was suggested in Incheon and Seoul, based on the results of correlation analysis with Hg and major ions in wet deposition, and meteorological data. The cluster analysis of backward trajectories demonstrated that the Hg concentration in wet deposition was highest in the cluster transported from Hebei and Shandong of China in Gwangju, but in Seoul, the Hg concentrations of each cluster were comparable. This suggests that regional transport is the major source of Hg in the wet deposition of Gwangju while local transport provides substantial amount of Hg in the wet deposition of Seoul. This was further supported by the results of concentration-weighted trajectories: the most probable source region was east China for Gwangju, and the mid-west of South Korea and east China for Seoul. It is noted that the peak methylmercury concentrations were found every spring with simultaneous increases in atmospheric Al, Ca, Mg, and Fe concentrations, indicating a concurrence with Asian dust. The formation process of methylmercury in Asian dust should be confirmed in future studies.

[Fluorescence Characteristics and Source Analysis of DOM in Snowfall of Xi'an].

Fluorescence characteristics and sources of dissolved organic matter (DOM) in snowfall in Xi'an were studied by three-dimensional fluorescence spectroscopy, parallel factor analysis, and backward trajectory model, which provided a data basis for the analysis of the chemical composition and source of atmospheric organic pollutants. Results show that the DOC content of DOM was 0.88-10.92 mg·L-1. DOM mainly contained humus-like, fulvic acid-like, tryptophan-like, and tyrosine-like substances. The fluorescence intensity and the summed intensities of these substances exhibited significant positive correlations with the DOC and UV254 (P<0.01). The fluorescence index (FI), biological source index (BIX), and humic index (HIX) values of DOM during snowfall were 1.50-1.75, 0.87-1.25, and 1.11-1.97, respectively. FI was positively correlated with BIX and negatively correlated with HIX (P<0.05). During snowfall, the air mass transmission trajectories included the local transmission, long-distance transmission starting from Xinjiang (through Gansu and Ningxia), and medium-distance transmissions starting from Inner Mongolia (through Ningxia) and Shandong (via Henan), accounting for 38.78%, 24.04%, 19.87%, and 17.31% of the total, respectively. This indicates that the content or relative content of the DOM contained in the precipitation can be characterized by fluorescence intensities and their sums of the humic-like, fulvic acid-like, tryptophan-like, and tyrosine-like tyrosine. The DOM in snowfall had both biological and terrestrial characteristics, and belonged to a self-generated source with the newly produced organic matter or matter with stronger self-source characteristics. Local transmission had the most significant contribution to the source of snowfall DOM.

[Spectral Characteristics and Source Analysis of WSOC of PM2.5 in Winter of Xi'an].

The spectral characteristics and sources of water-soluble organic compounds (WSOC) in PM2.5 in winter were studied by using UV-vis absorption spectroscopy, three-dimensional fluorescence spectroscopy, parallel factor analysis, and backward trajectory model. The results showed that the concentration of WSOC in PM2.5 was 4.66-14.75 µg ·m-3. The values of E2/E3, E3/E4, S275-295, SUVA254, AAE, and MAE365 of WSOC were, respectively, in the range of 2.85-4.32, 2.21-3.56, 0.0099-0.0127 nm-1, 2.35-3.89 m2 ·g-1, 2.66-4.60, and 1.51-2.60 m2 ·g-1. The E2/E3, E3/E4, S275-295, and AAE values of WSOC at the sampling site in the southern suburb of Xi'an, China (Xi'an University of Architecture and Technology) were higher than those at the sampling site in the northern suburb (sports park), while the values of SUVA254 and MAE365 were lower. There were four fluorescent components in WSOC identified by the EEMs-PARAFAC model: C1 and C2 were fulvic acid-like and protein-like, respectively, and C3 and C4 were humus-like components. The fluorescence intensities and the sum of the fluorescent components were positively correlated with the concentrations of PM2.5, OC, WSOC, and A254 value (P<0.01). The fluorescence index (FI), biological source index (BIX), and humic index (HIX) values of WSOC were 1.75-2.12, 1.14-1.46, and 1.18-2.06, respectively. During the monitoring period, the air mass transmission trajectory was dominated by the local southwest of short-distance transmission, and its trajectory accounted for more than 50%. The pollutant emissions from Xinjiang, Inner Mongolia, and Gansu also made significant contributions to the air pollution levels in Xi'an in winter. There was a small difference in the carbon component content of PM2.5 in the northern and southern suburbs of Xi'an. The molecular weight, humification degree, and light absorption capacity of WSOC at the southern suburb sampling site were lower than those in the northern suburb where the wavelength dependence of light absorption intensity was relatively stronger. The WSOC mainly originated from biological sources or both from biological and terrestrial sources. Local transmission had the most significant contribution to PM2.5 and WSOC in winter.

[Analysis of Different Particle Sizes, Pollution Characteristics, and Sources of Atmospheric Aerosols During the Spring Dust Period in Beijing].

To understand the evolution of the physical and chemical properties of dust aerosols in the atmosphere, the concentrations and chemical compositions of differently sized particles were continuously observed and analyzed using an ion chromatograph and carbonaceous analyzer during the outbreak of dust in May 2017 in Beijing. The concentrations of total suspended particulate (TSP), water-soluble organic carbon (WSOC), elemental carbon (EC), OC, and water-soluble inorganic ions were (2237.59±681.49), (29.90±18.05), (1.46±3.05), (67.35±29.07), and (136.75±46.38) µg·m-3 during the dust period, respectively, and significantly exceeded that of the non-dust period, except for EC. The Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3-, SO42-, and WSOC concentrations during the dust storm period were 11.55, 3.00, 14.88, 14.89, 9.40, 4.60, 2.40, 3.91, and 1.83 times higher than that during the non-dust period. The growth of crustal ions, such as Ca2+ and K+, was notably the largest and NH4+ and NO3- were minimal. The size distribution indicates that crustal ions primarily occur in the coarse mode during the whole sampling campaign. The SO42- and NO3- ions are slightly bimodal during the dust storm, with a dominant peak in the coarse mode at 4.7-5.8 µm and a very minor peak in the fine mode with a size range of 0.43-0.65 µm. During the non-dust period, SO42- is the dominant mode in the fine mode, while NO3- changes little compared with that during the dust period, which indicates that heterogeneous reaction with crustal ions is the main formation mechanism of NO3- in the coarse mode. A significant positive correlation was observed between SO42- and the sum of crustal ions during the dust period, indicating that the source of SO42- during the dust period is remote transmission of the dust storm. During the non-dust period, the positive correlation of SO42- with NH4+ indicates that secondary formation is the main source of SO42-. Based on correlation analysis of NO3- with crustal ions and NH4+, both remote transmission and secondary formation are the sources of NO3- during the dust storm and heterogeneous reactions are predominant during the non-dust period.

GIS-based multielement source analysis of dustfall in Beijing: A study of 40 major and trace elements.

Dust, as an important carrier of inorganic and organic pollutants, daily exposes to human without any protection. It affects our health adversely, especially its chemical elements and ions. In this research, we investigated the chemical characteristics of dustfall in Beijing, specifically in terms of 40 major and trace elements, and presented semi-quantitative evaluations of the relative local and remote contributions. In total, 58 samples were collected in Beijing and nearby cities during 2013-2014 "the winter heating period". Using multiple statistical methods and GIS techniques, we obtained the relative similarities among certain elements and identified their pollution sources (from local or nearby cities). And more interestingly, the relative contributions of nearby cities can be calculated by the Hysplit4 backward-trajectory model. In addition, the correlation analysis for the 40 elements in dust and soil indicated that traffic restricted interchange between them; the city center, with the heaviest traffic, had the most significant influence. Finally, the resulting source apportionment was examined and modified using land use data and terrain information. We hope it can provide a strong basis for the environmental protection and risk assessment.