Contribution of Carbonyl Chromophores in Secondary Brown Carbon from Nighttime Oxidation of Unsaturated Heterocyclic Volatile Organic Compounds

The light absorption properties of brown carbon (BrC), which are linked to molecular chromophores, may play a significant role in the Earth's energy budget. While nitroaromatic compounds have been identified as strong chromophores in wildfire-driven BrC, other types of chromophores remain to be investigated. Given the electron-withdrawing nature of carbonyls ubiquitous in the atmosphere, we characterized carbonyl chromophores in BrC samples from the nighttime oxidation of furan and pyrrole derivatives, which are important but understudied precursors of secondary organic aerosols primarily found in wildfire emissions. Various carbonyl chromophores were characterized and quantified in BrC samples, and their ultraviolet-visible spectra were simulated by using time-dependent density functional theory. Our findings suggest that chromophores with carbonyls bonded to nitrogen (i.e., imides and amides) derived from N-containing heterocyclic precursors substantially contribute to BrC light absorption. The quantified N-containing carbonyl chromophores contributed to over 40% of the total light absorption at wavelengths below 350 nm and above 430 nm in pyrrole BrC. The contributions of chromophores to total light absorption differed significantly by wavelength, highlighting their divergent importance in different wavelength ranges. Overall, our findings highlight the significance of carbonyl chromophores in secondary BrC and underscore the need for further investigation.

Remediation of Thirdhand Tobacco Smoke with Ozone: Probing Deep Reservoirs in Carpets

We assessed the efficacy of ozonation as an indoor remediation strategy by evaluating how a carpet serves as a sink and long-term source of thirdhand tobacco smoke (THS) while protecting contaminants absorbed in deep reservoirs by scavenging ozone. Specimens from unused carpet that was exposed to smoke in the lab ("fresh THS") and contaminated carpets retrieved from smokers' homes ("aged THS") were treated with 1000 ppb ozone in bench-scale tests. Nicotine was partially removed from fresh THS specimens by volatilization and oxidation, but it was not significantly eliminated from aged THS samples. By contrast, most of the 24 polycyclic aromatic hydrocarbons detected in both samples were partially removed by ozone. One of the home-aged carpets was installed in an 18 m³ room-sized chamber, where its nicotine emission rate was 950 ng day^-1 m^-2. In a typical home, such daily emissions could amount to a non-negligible fraction of the nicotine released by smoking one cigarette. The operation of a commercial ozone generator for a total duration of 156 min, reaching concentrations up to 10,000 ppb, did not significantly reduce the carpet nicotine loading (26-122 mg m^-2). Ozone reacted primarily with carpet fibers, rather than with THS, leading to short-term emissions of aldehydes and aerosol particles. Hence, by being absorbed deeply into carpet fibers, THS constituents can be partially shielded from ozonation.

Peroxy Radical Autoxidation and Sequential Oxidation in Organic Nitrate Formation during Limonene Nighttime Oxidation

Limonene is an abundant monoterpene released into the atmosphere via biogenic emissions and biomass burning. However, the atmospheric oxidation and secondary organic aerosol (SOA) formation mechanisms of limonene, especially during nighttime, remain largely understudied. In this work, limonene was oxidized synergistically by ozone (O₃) and nitrate radicals (NO₃) in a flow tube reactor and a continuous flow stirred tank reactor. Upon oxidation, many highly oxidized organic nitrates and nitrooxy peroxy radicals (RO₂) were observed in the gas phase within 1 min. Combining quantum chemical calculations with kinetic simulations, we found that the primary nitrooxy RO₂ (C₁₀H₁₆NO₅) through NO₃ addition at the more substituted endocyclic double bond and at the exocyclic double bond (previously considered as minor pathways) can undergo autoxidation with rate constants of around 0.02 and 20 s^-1 at 298 K, respectively. These pathways could explain a major portion of the observed highly oxidized organic nitrates. In the SOA, highly oxidized mono- and dinitrates (e.g., C₁₀H₁₇NO_7-8 and C₁₀H₁₆,₁₈N₂O_8-10) make up a significant contribution, highlighting nitrooxy RO₂ autoxidation and sequential NO₃ oxidation of limonene. The same organic nitrates are also observed in ambient aerosol during biomass burning and nighttime in the southeastern United States. Therefore, the present work provides new insights into the nighttime oxidation of limonene and SOA formation in the atmosphere.

Chemical Structure Regulates the Formation of Secondary Organic Aerosol and Brown Carbon in Nitrate Radical Oxidation of Pyrroles and Methylpyrroles

Nitrogen-containing heterocyclic volatile organic compounds (VOCs) are important components of wildfire emissions that are readily reactive toward nitrate radicals (NO₃) during nighttime, but the oxidation mechanism and the potential formation of secondary organic aerosol (SOA) and brown carbon (BrC) are unclear. Here, NO₃ oxidation of three nitrogen-containing heterocyclic VOCs, pyrrole, 1-methylyrrole (1-MP), and 2-methylpyrrole (2-MP), was investigated in chamber experiments to determine the effect of precursor structures on SOA and BrC formation. The SOA chemical compositions and the optical properties were analyzed using a suite of online and offline instrumentation. Dinitro- and trinitro-products were found to be the dominant SOA constituents from pyrrole and 2-MP, but not observed from 1-MP. Furthermore, the SOA from 2-MP and pyrrole showed strong light absorption, while that from 1-MP were mostly scattering. From these results, we propose that NO₃-initiated hydrogen abstraction from the 1-position in pyrrole and 2-MP followed by radical shift and NO₂ addition leads to light-absorbing nitroaromatic products. In the absence of a 1-position hydrogen, NO₃ addition likely dominates the 1-MP chemistry. We also estimate that the total SOA mass and light absorption from pyrrole and 2-MP are comparable to those from phenolic VOCs and toluene in biomass burning, underscoring the importance of considering nighttime oxidation of pyrrole and methylpyrroles in air quality and climate models.

Sequence variants in the sulfonylurea receptor (SUR) gene are associated with NIDDM in Caucasians

NIDDM is a common heterogeneous disorder, the genetic basis of which has yet to be determined. The sulfonylurea receptor (SUR) gene, now known to encode an integral component of the pancreatic beta-cell ATP-sensitive potassium channel, IKATP, was investigated as a logical candidate for this disorder. The two nucleotide-binding fold (NBF) regions of SUR are known to be critical for normal glucose regulation of insulin secretion. Thus, single-strand conformational polymorphism analysis was used to find sequence changes in the two NBF regions of the SUR gene in 35 NIDDM patients. Eight variants were found; and three were evaluated in two Northern European white populations (Utah and the U.K.): 1) a missense mutation in exon 7 (S1370A) was found with equal frequency in patients (n = 223) and control subjects (n = 322); 2) an ACC-->ACT silent variant in exon 22 (T761T) was more common in patients than in control subjects (allele frequencies 0.07 vs. 0.02, P = 0.0008, odds ratio (OR) 3.01, 95% CI 1.54-5.87); and 3) an intronic t-->c change located at position -3 of the exon 24 splice acceptor site was also more common in patients than in control subjects (0.62 vs. 0.46, P < 0.0001, OR 1.91, 95% Cl 1.50-2.44). The combined genotypes of exon 22 C/T or T/T and intron 24 -3c/-3c occurred in 8.9% of patients and 0.5% of control subjects (P < 0.0001, OR 21.5, 95% CI 2.91-159.6). These results suggest that defects at the SUR locus may be a major contributor to the inherited basis of NIDDM in Northern European Caucasians.

[Precocious puberty associated with Von Recklinghausen's disease. Developmental follow-up under cyproterone acetate treatment]

Authors describe a case of a boy aged 8-10/12 years with precocious puberty associated with Von Recklinghausen's disease. He was treated with cyproterone acetate (100 mg/m2/24 h oral doses) and controlled for a period of two years. He shows very few effects of puberal physical signs and improvement of his sexual behavioral area. They have evaluated growth evolution by different parameters and couldn't appreciate any improvement because of the advanced bone age (13-6/12 years) when treatment was started.

[An endemic area of sporotrichosis in Guatemala]

An endemic area of sporotrichosis is described in the Lake of Ayarza District, South Guatemala, where 53 patients have been observed within 3 years. In 45.3% of the cases, the infection appeared after handling fish. The disease was more frequently observed in man (83%) and in patients less than 30 years of age. The most frequent clinical type was the ascending lymphocutaneous sporotrichosis of the limbs. Some cases of ulcerative or verrucous lesions were seen. Almost all the patients cured rapidly either by potassium iodide (46 patients) or spontaneously, or after application of local heat (4 patients). Intradermal tests were performed in healthy population in the endemic area and, for comparison, in Guatemala City. Whole yeast cell antigens of Sporothrix schenckii and Ceratocystis stenoceras were used in these tests. Skin tests to both antigens were more frequently positive in the endemic area; the highest frequency was obtained with the antigen of C. stenoceras. A serological study was performed in 26 patients. The fluorescent antibody staining technique was more sensitive than yeast cell and latex particles agglutinations. C. stenoceras was isolated from bark of some trees, especially Eucalyptus, in the environment, but not S. schenckii.