Formation of metal-organic ligand complexes affects solubility of metals in airborne particles at an urban site in the Po valley.

Metals in atmospheric aerosols play potentially an important role in human health and ocean primary productivity. However, the lack of knowledge about solubility and speciation of metal ions in the particles or after solubilisation in aqueous media (sea or surface waters, cloud or rain droplets, biological fluids) limits our understanding of the underlying physico-chemical processes. In this work, a wide range of metals, their soluble fractions, and inorganic/organic compounds contained in urban particulate matter (PM) from Padua (Italy) were determined. Metal solubility tests have been performed by dissolving the PM in water and in solutions simulating rain droplet composition. The water-soluble fractions of the metal ions and of the organic compounds having ligand properties have been subjected to a multivariate statistical procedure, in order to elucidate associations among the aqueous concentrations of these PM components in simulated rain droplets. In parallel, a multi-dimensional speciation calculation has been performed to identify the stoichiometry and the amount of metal-ligand complexes theoretically expected in aqueous solutions. Both approaches showed that the solubility and the aqueous speciation of metal ions were differently affected by the presence of inorganic and organic ligands in the PM. The solubility of Al, Cr, and Fe was strongly correlated to the concentrations of oxalic acid, as their oxalate complexes represented the expected dominant species in aqueous solutions. Oxalates of Al represented ∼98% of soluble Al, while oxalates of Cu represented 34-75% of the soluble Cu, and oxalates of Fe represented 76% of soluble Fe. The oxidation state of Fe can strongly impact the speciation picture. If Fe is present as Fe(II) rather than Fe(III), the amount of Cr and Cu complexed with diacids can increase from 75% to 94%, and from 32% to 53%, respectively. For other metals, the solubility depended on the formation of soluble aquo-complexes, hence with a scarce effect of the organic ligands. An iron-oxalate complex was also directly detected in aerosol sample extracts.

Twitter analysis of the orthodontic patient experience with braces vs Invisalign.

OBJECTIVE: To examine the orthodontic patient experience having braces compared with Invisalign by means of a large-scale Twitter sentiment analysis. MATERIALS AND METHODS: A custom data collection program was created that collected tweets containing the words "braces" or "Invisalign" for a period of 5 months. A hierarchal Naïve Bayes sentiment analysis classifier was developed to sort the tweets into five categories: positive, negative, neutral, advertisement, or not applicable. Each category was then analyzed for specific content. RESULTS: A total of 419,363 tweets applicable to orthodontics were collected. Users posted significantly more positive tweets (61%) than they did negative tweets (39%; P ≤ .0001). There was no significant difference in the distribution of positive and negative sentiment between braces and Invisalign tweets (P = .4189). Positive orthodontics-related tweets often highlighted gratitude for a great smile accompanied with selfies. Negative orthodontic tweets frequently focused on pain. CONCLUSION: Twitter users expressed more positive than negative sentiment about orthodontic treatment with no significant difference in sentiment between braces and Invisalign tweets.

Enhanced Volatile Organic Compounds emissions and organic aerosol mass increase the oligomer content of atmospheric aerosols.

Secondary organic aerosol (SOA) accounts for a dominant fraction of the submicron atmospheric particle mass, but knowledge of the formation, composition and climate effects of SOA is incomplete and limits our understanding of overall aerosol effects in the atmosphere. Organic oligomers were discovered as dominant components in SOA over a decade ago in laboratory experiments and have since been proposed to play a dominant role in many aerosol processes. However, it remains unclear whether oligomers are relevant under ambient atmospheric conditions because they are often not clearly observed in field samples. Here we resolve this long-standing discrepancy by showing that elevated SOA mass is one of the key drivers of oligomer formation in the ambient atmosphere and laboratory experiments. We show for the first time that a specific organic compound class in aerosols, oligomers, is strongly correlated with cloud condensation nuclei (CCN) activities of SOA particles. These findings might have important implications for future climate scenarios where increased temperatures cause higher biogenic volatile organic compound (VOC) emissions, which in turn lead to higher SOA mass formation and significant changes in SOA composition. Such processes would need to be considered in climate models for a realistic representation of future aerosol-climate-biosphere feedbacks.