Arsenic speciation in freshwater fish: challenges and research needs.

Food and water are the main sources of human exposure to arsenic. It is important to determine arsenic species in food because the toxicities of arsenic vary greatly with its chemical speciation. Extensive research has focused on high concentrations of arsenic species in marine organisms. The concentrations of arsenic species in freshwater fish are much lower, and their determination presents analytical challenges. In this review, we summarize the current state of knowledge on arsenic speciation in freshwater fish and discuss challenges and research needs. Fish samples are typically homogenized, and arsenic species are extracted using water/methanol with the assistance of sonication and enzyme treatment. Arsenic species in the extracts are commonly separated using high-performance liquid chromatography (HPLC) and detected using inductively coupled plasma mass spectrometry (ICPMS). Electrospray ionization tandem mass spectrometry, used in combination with HPLC and ICPMS, provides complementary information for the identification and characterization of arsenic species. The methods and perspectives discussed in this review, covering sample preparation, chromatography separation, and mass spectrometry detection, are directed to arsenic speciation in freshwater fish and applicable to studies of other food items. Despite progress made in arsenic speciation analysis, a large fraction of the total arsenic in freshwater fish remains unidentified. It is challenging to identify and quantify arsenic species present in complex sample matrices at very low concentrations. Further research is needed to improve the extraction efficiency, chromatographic resolution, detection sensitivity, and characterization capability.

Impact of glycol-based solvents on indoor air quality-Artificial fog and exposure pathways of formaldehyde and various carbonyls.

Artificial fog is commonly employed in the entertainment industry and indoor household celebrations. The fog is generated from glycol-based solvents, which can also be found in e-cigarettes and personal care products. Although potential health impacts of glycol inhalation are frequently cited by studies of e-cigarette smoking, the dynamics and the chemical composition of glycol-based aerosols have never been studied systematically. The objective of this work is to investigate the impact of glycol-based aerosol on indoor air quality. Specifically, we targeted artificial fogs generated with common glycols, including propylene glycol (PG) and triethylene glycol (TEG). With the aid of a novel aerosol collecting and monitoring instrument setup, we obtained time-resolved aerosol profiles and their chemical compositions in an experimental room. Artificial fog has given rise to a significant amount of ultra-fine particulate matter, demonstrating its negative impact on indoor air quality. Additionally, we found a high concentration (9.75 mM) of formaldehyde and other carbonyls in fog machine fluids stored for months. These compounds are introduced to the indoor air upon artificial fog application. We propose that carbonyls have accumulated from the oxidative decomposition of glycols, initiated by OH radicals and singlet oxygens (1 O2 ) and likely sustained by autooxidation. Oxidation of glycols by indoor oxidants has never been reported previously. Such chemical processes can represent an unrecognized source of toxic carbonyl compounds which is also applicable to other glycol-based solvents.

Particulate matter emitted from ultrasonic humidifiers-Chemical composition and implication to indoor air.

Household humidification is widely practiced to combat dry indoor air. While the benefits of household humidification are widely perceived, its implications to the indoor air have not been critically appraised. In particular, ultrasonic humidifiers are known to generate fine particulate matter (PM). In this study, we first conducted laboratory experiments to investigate the size, quantity, and chemical composition of PM generated by an ultrasonic humidifier. The mass of PM generated showed a correlation with the total alkalinity of charge water, suggesting that CaCO3 is likely making a major contribution to PM. Ion chromatography analysis revealed a large amount of SO42- in PM, representing a previously unrecognized indoor source. Preliminary results of organic compounds being present in humidifier PM are also presented. A whole-house experiment was further conducted at an actual residential house, with five low-cost sensors (AirBeam) monitoring PM in real time. Operation of a single ultrasonic humidifier resulted in PM2.5 concentrations up to hundreds of µg m-3 , and its influence extended across the entire household. The transport and loss of PM2.5 depended on the rate of air circulation and ventilation. This study emphasizes the need to further investigate the impact of humidifier operation, both on human health and on the indoor atmospheric chemistry, for example, partitioning of acidic and basic compounds.

pH Dependence of the OH Reactivity of Organic Acids in the Aqueous Phase.

Photochemical processing taking place in atmospheric aqueous phases serves as both a source and a sink of organic compounds. In aqueous environments, acid-base chemistry and, by extension, aqueous-phase pH, are an important yet often neglected factors to consider when investigating the kinetics of organic compounds. We have investigated the aqueous-phase OH-oxidation of pinic acid, cis-pinonic acid, limononic acid, and formic acid (FA) as a function of pH. We have also extended our studies to other organic acids (OAs) present in the water-soluble fraction of secondary organic aerosol (SOA) arising from the ozonolysis of α-pinene. Although all the OAs exhibited larger OH reactivities at pH 10, the pH dependence was dramatically different between FA, the smallest OA, and those that contained more than eight carbons. A kinetic box model was also employed to characterize our photoreactor and to provide confidence to our results. Our finding shows that the atmospheric lifetimes of small OAs (e.g., FA) are highly sensitive to cloud water pH. However, those of larger OAs and many other OAs in α-pinene SOA are affected to a much less extent. These results are of great importance for the simplification of cloud water chemistry models.