The importance of organic compounds in the oxidative capacity of the atmosphere, and as cloud condensation and ice-forming nuclei, has been recognized for several decades. Organic compounds comprise a significant fraction of the suspended matter mass, leading to local (e.g. toxicity, health hazards) and global (e.g. climate change) impacts. The state of knowledge of the physical chemistry of organic aerosols has increased during the last few decades. However, due to their complex chemistry and the multifaceted processes in which they are involved, the importance of organic aerosols, particularly bioaerosols, in driving physical and chemical atmospheric processes is still very uncertain and poorly understood. Factors such as solubility, surface tension, chemical impurities, volatility, morphology, contact angle, deliquescence, wettability, and the oxidation process are pivotal in the understanding of the activation processes of cloud droplets, and their chemical structures, solubilities and even the molecular configuration of the microbial outer membrane, all impact ice and cloud nucleation processes in the atmosphere. The aim of this review paper is to assess the current state of knowledge regarding chemical and physical characterization of bioaerosols with a focus on those properties important in nucleation processes. We herein discuss the potential importance (or lack thereof) of physical and chemical properties of bioaerosols and illustrate how the knowledge of these properties can be employed to study nucleation processes using a modeling exercise. We also outline a list of major uncertainties due to a lack of understanding of the processes involved or lack of available data. We will also discuss key issues of atmospheric significance deserving future physical chemistry research in the fields of bioaerosol characterization and microphysics, as well as bioaerosol modeling. These fundamental questions are to be addressed prior to any definite conclusions on the potential significance of the role of bioaerosols on physico-chemical atmospheric processes and that of climate.

A theoretical study was performed involving the reactions of a series of atmospherically significant Criegee intermediates (CIs), including parent, mono- and dimethyl - substituted CIs, with water and the water dimer at the CCSD(T)//B3LYP/6-311+G(2d,2p) level. We investigated two reaction routes leading to α-hydroxyalkyl hydroperoxide (HAHP). According to our calculations, the most favorable route is the formation of HAHP as the result of reactions of CIs with the water dimer. The rate constants for both pathways were calculated and the dependence of overall rate constant on temperature and relative humidity was also evaluated. The implication of our results to the chemistry of the troposphere is herein discussed.

Air pollution of anthropogenic origin is largely from the combustion of biomass (e.g., wood), fossil fuels (e.g., cars and trucks), incinerators, landfills, agricultural activities and tobacco smoke. Air pollution is a complex mixture that varies in space and time, and contains hundreds of compounds including volatile organic compounds (e.g., benzene), metals, sulphur and nitrogen oxides, ozone and particulate matter (PM). PM_0.1 (ultrafine particles (UFP)), those particles with a diameter less than 100 nm (includes nanoparticles (NP)) are considered especially dangerous to human health and may contribute significantly to the development of numerous respiratory and cardiovascular diseases such as chronic obstructive pulmonary disease (COPD) and atherosclerosis. Some of the pathogenic mechanisms through which PM_0.1 may contribute to chronic disease is their ability to induce inflammation, oxidative stress and cell death by molecular mechanisms that include transcription factors such as nuclear factor κB (NF-κB) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Epigenetic mechanisms including non-coding RNA (ncRNA) may also contribute towards the development of chronic disease associated with exposure to PM_0.1. This paper highlights emerging molecular concepts associated with inhalational exposure to PM_0.1 and their ability to contribute to chronic respiratory and systemic disease.

Kinetics of O₃ initiated oxidation reaction of Hg⁰ was performed in N₂ and over the temperature range of 283–323 K at pressure of 750 ± 1 Torr, in order to provide further understanding of geochemical mercury cycling. Kinetic studies were carried out using relative and absolute techniques by gas chromatography with mass spectroscopy (GC-MS). The room temperature reaction rate constant was determined to be (7.5 ± 0.9) × 10⁻¹⁹ cm³ molecule⁻¹ s⁻¹. The calculated activation energy (E_A ) and pre-exponential factor (A) were 11.7 ± 0.27 kJ mol⁻¹ and 8.43 × 10⁻¹⁷ cm³ molecule⁻¹ s⁻¹, respectively. For the first time, products of O₃-initiated oxidation of elemental mercury have been studied in the gas-phase, from the suspended aerosols, and from the wall of the reactor, using chemical ionization mass spectrometry (CI-MS), GC-MS, and inductively coupled plasma mass spectrometry (ICP-MS). Under our experimental conditions, the dominant identified product was HgO, which was mainly adsorbed on the reaction walls, and there was less than 1% of the reaction product collected on the micron filters (0.5 μ) from the suspended aerosols. The implications of our kinetics and product studies to the chemistry of the atmosphere are herein discussed.

Rapid urbanization, advancements in science and technology, and the increase in tech-savviness of consumers have led to an exponential production of a variety of electronic equipment. The global annual growth rate of e-waste volume exceeds the growth rate of the human population. Electronic waste has now become a point of concern globally (53.6 million metric tons, 2019). However, merely 17.4% of all global e-waste is properly collected and recycled. China is the largest contributor to the global production of e-waste (~19%), the second being the United States. Indeed, only 14 countries generated over 65% of global e-waste production in 2019. E-wastes contain a wide range of organic, and inorganic compounds including various metals. Emerging contaminants like plastics are amongst the fastest growing constituents of electronic waste. The current challenges include the lack of reliable data, inadequate identification and quantification of new emerging materials, limited effectiveness of current recycling technologies, need for cutting-edge detection and recycling technologies, and the lack of e-waste management policies and international collaboration. In this review, we strive to integrate the existing data on production rates at different spatial scales, composition, as well as health, economical, and environmental challenges, existing recycling technologies; explore tangible solutions; and encourage further sustainable technology and regulatory policies.

Mercury is a persistent, toxic and bio-accumulative pollutant of global interest. Its main mass in the troposphere is in the form of elemental gas-phase mercury. Rapid, near-complete depletion of m...