Surfactants in atmospheric aerosols and rainwater around lake ecosystem

Measuring the Surface Tension of Atmospheric Particles and Relevant Mixtures to Better Understand Key Atmospheric Processes

Aerosol and aqueous particles are ubiquitous in Earth's atmosphere and play key roles in geochemical processes such as natural chemical cycles, cloud and fog formation, air pollution, visibility, climate forcing, etc. The surface tension of atmospheric particles can affect their size distribution, condensational growth, evaporation, and exchange of chemicals with the atmosphere, which, in turn, are important in the above-mentioned geochemical processes. However, because measuring this quantity is challenging, its role in atmospheric processes was dismissed for decades. Over the last 15 years, this field of research has seen some tremendous developments and is rapidly evolving. This review presents the state-of-the-art of this subject focusing on the experimental approaches. It also presents a unique inventory of experimental adsorption isotherms for over 130 mixtures of organic compounds in water of relevance for model development and validation. Potential future areas of research seeking to better determine the surface tension of atmospheric particles, better constrain laboratory investigations, or better understand the role of surface tension in various atmospheric processes, are discussed. We hope that this review appeals not only to atmospheric scientists but also to researchers from other fields, who could help identify new approaches and solutions to the current challenges.

Mechanistic Influence of Chemical Agglomeration Agents on Removal of Inhalable Particles from Coal Combustion

Particle pollution has been a research topic attracting the attention of the researchers around the world because inhalable particles are hazardous to humans and the environment. The major resource of particle pollution is the combustion of coal and biomass. Dust collectors, electrostatic precipitators, and bag filters are required to remove particles from flue. Because of the large specific surface areas of inhalable particles, they easily agglomerate to form larger aggregates; therefore, improving the capture efficiency of dust collectors is of importance. Herein, chemical agglomeration agents were sprayed into a turbulent agglomeration chamber to improve the removal efficiency of inhalable particles. The results showed that the total removal efficiency of inhalable particles was 59.2% for the three-composition agglomeration agents of kappa carrageenans/Tween-80/NH₄Cl (KC/TW/NH₄Cl). The mean particle diameter increased from 2.8 μm before agglomeration to above 10.0 μm after agglomeration. In the agglomeration process, nonionic TW accelerates the wetting properties, in which the polymer, KC, or anion polyacrylamide, promotes prolongation of the contact time between droplets and particles. Two different removal mechanisms are proposed to explain the effect of chemical agglomeration agents. Immersion agglomeration described the agglomeration process of only fine particles, and distribution agglomeration supported the capture of large particles for fine ones in polydispersed aerosols.

Fine particles at a background site in Central France: Chemical compositions, seasonal variations and pollution events

To expand our knowledge of regional fine particles in Central France (Centre-Val de Loire region), a field observation study of PM_2.5 was carried out at Verneuil site (46.81467N, 2.61012E, 180m.a.s.l.) from 2011 to 2014. The mass concentrations of water-soluble inorganic ions (WSIIs), organic carbon (OC), elemental carbon (EC) and biomass burning tracer (Levoglucosan) in PM_2.5 were measured. Annual average PM_2.5 mass concentrations were 11.8, 9.5, 12.6 and 10.2μg·m^-3 in 2011, 2012, 2013 and 2014, respectively, three of four higher than the WHO guideline of 10μg·m^-3. Secondary inorganic aerosol (SIA) and organic matter (OM) appeared to be the major components in PM_2.5 in Verneuil, contributing 30.1-41.8% and 36.9-46.3%, respectively. Main chemical species were observed in the following order: winter≥spring>autumn>summer. Backward atmospheric trajectories were performed using Hysplit model and suggested that the PM_2.5 pollutants caused by atmospheric transport were mainly originated from European inland, mainly east to north-east areas. During the observation period, five pollution events were reported and indicated that not only the polluted air masses from central Europe but also the biomass burning from East Europe significantly influenced the air quality in Verneuil site.

Characterization of rainwater chemical composition after a Southeast Asia haze event: insight of transboundary pollutant transport during the northeast monsoon

Open biomass burning in Peninsula Malaysia, Sumatra, and parts of the Indochinese region is a major source of transboundary haze pollution in the Southeast Asia. To study the influence of haze on rainwater chemistry, a short-term investigation was carried out during the occurrence of a severe haze episode from March to April 2014. Rainwater samples were collected after a prolonged drought and analyzed for heavy metals and major ion concentrations using inductively coupled plasma mass spectroscopy (ICP-MS) and ion chromatography (IC), respectively. The chemical composition and morphology of the solid particulates suspended in rainwater were examined using a scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). The dataset was further interpreted using enrichment factors (EF), statistical analysis, and a back trajectory (BT) model to find the possible sources of the particulates and pollutants. The results show a drop in rainwater pH from near neutral (pH 6.54) to acidic (<pH 4.00) during the haze to non-haze transitional period, suggesting that the deposition rate of sulfate and nitrate in the atmosphere via the precipitation process was relatively lower compared to the mineral components. Zinc, nitrate, and calcium, which were the predominant elements in the first rainwater samples. Besides, the results of the SEM-EDS indicated that the zinc was possibly originated from anthropogenic activities which are consistent with the results obtained from EF. The BT model showed that pollutants transported from the mainland of Indo-China and the marine region in the South China Sea were responsible for the high pollution event in the study area. These findings can be useful in identifying contributions of pollutants from single or multiple sources in rainwater samples during haze episodes.