Effect of relative humidity and the presence of aerosol particles on the α-pinene ozonolysis

The pinene scaffold: its occurrence, chemistry, synthetic utility, and pharmacological importance

Plant-based secondary metabolites have been a major source of drug discovery and inspiration for new generations of drugs. Plants offer a wide variety of compound classes, including alkaloids, terpenes, flavonoids, and glycosides, with different molecular architectures (fused bridgehead, bi- and polycyclic, spirocyclic, polycyclic, and acyclic). The diversity, abundance, and accessibility of plant metabolites make plants an attractive source of human and animal medicine. Even though the pinene scaffold is abundant in nature and has historical use in traditional medicine, pinene and pinene-derived compounds have not been comprehensively studied for medicinal applications. This review provides insight into the utility of the pinene scaffold as a crucial building block of important natural and synthetic products and as a chiral reagent in the asymmetric synthesis of important compounds.

Characterization of enoxacin (ENO) during ClO2 disinfection in water distribution system: Kinetics, byproducts, toxicity evaluation and halogenated disinfection byproducts (DBPs) formation potential

Enoxacin (ENO) is widespread in water because it is commonly used as a human and veterinary antibiotic. However, little effort has been dedicated to revealing the transformation mechanisms of ENO destruction using ClO₂, especially within a water distribution system (WDS). To address this knowledge gap, the kinetics, byproducts, toxicity, and formation potential of halogenated disinfection byproducts (DBPs) associated with ENO destruction using ClO₂ in a pilot-scale PE pipe was explored for the first time. Statistical analyses showed that the destruction efficiency of ENO in the pilot-scale PE pipe was lower than that in deionized water (DI water), and the reactions in DI water followed the second-order kinetic model. Furthermore, pH has a significant effect on the destruction of ENO, and the removal ratio increased at a higher pH. Additionally, increasing the flow rate elevated the ENO removal efficiency; however, the influence of flow velocity was limited to ENO destruction. The ENO removal rates within the diverse pipes exhibited the following order: stainless steel pipe < PE pipe < ductile iron pipe. Nine possible intermediates were identified, and those that were formed by piperazine group cleavage represented the major primary byproducts of the entire destruction process. Additionally, the ENO destruction in a pilot-scale PE pipe had minimal influence on halogenated DBPs and chlorite formation. Finally, the toxicity evaluation illustrated that the presence of ENO increased the potential risk of water quality safety when treated with ClO₂.

Effect of relative humidity on SOA formation from aromatic hydrocarbons: Implications from the evolution of gas- and particle-phase species

Relative humidity (RH) plays a significant role in secondary organic aerosol (SOA) formation, but the mechanisms remain uncertain. Using a 30 m³ indoor smog chamber, the influences of RH on SOA formation from two conventional anthropogenic aromatics (toluene and m-xylene) were investigated from the perspective of both the gas- and particle- phases based on the analysis of multi-generation gas-phase products and the chemical composition of SOA, which clearly distinguishes from many previous works mainly focused on the particle-phase. Compared to experiments with RH of 2.0%, SOA yields increased by 11.1%-133.4% and 4.0%-64.5% with higher RH (30.0%-90.0%) for toluene and m-xylene, respectively. The maximum SOA concentration always appeared at 50.0% RH, which is consistent with the change trend of SOA concentration with RH in the summertime field observation. The most plausible reason is that the highest gas-phase OH concentration was observed at 50.0% RH, when the increases in gas-phase OH formation and OH uptake to aerosols and chamber walls with increasing RH reached a balance. The maximum OH concentration was accompanied by a notable decay of second-generation products and formation of third-generation products at 50.0% RH. With further increasing RH, more second-generation products with insufficient oxidation degree will be partitioned into the aerosol phase, and the aqueous-phase oxidation process will also be promoted due to the enhanced uptake of OH. These processes concurrently caused the O/C and oxidation state of carbon (OSc) to first increase and then slightly decrease. This work revealed the complex influence of RH on SOA formation from aromatic VOCs through affecting the OH concentration, partitioning of advanced gas-phase oxidation products as well as aqueous-phase oxidation processes. Quantitative studies to elucidate the role of RH in the partitioning of oxidation products should be conducted to further clarify the mechanism of the influence of RH on SOA formation.

Occurrence of antibiotics in rural drinking water and related human health risk assessment

Antibiotic residues in drinking water can have a negative impact on both human and environmental health. However, drinking water purification processes employed in rural areas are often less complicated than those used in urban areas. The occurrence of antibiotic residues in rural drinking water and their potential effects on residents' health remains to be established. In this study, we measured antibiotic levels in rural drinking water using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and evaluated the associated health risks based on Chinese population exposure parameters. Twenty-three antibiotics were detected in drinking water samples, of which fluoroquinolones and macrolides were the most common. The type and concentration of antibiotics in drinking water were affected both by the quality of the water source and by the water purification process used. The health risks associated with antibiotics in drinking water were within acceptable levels and likely to have little impact on human health. Of the antibiotics detected, salinomycin presented the greatest risk to human health. These findings can help to play a role in devising strategies to ensure drinking water safety.

Profiling of intracellular and extracellular antibiotic resistance genes in tap water

Antibiotic resistance genes (ARGs) have gained global attention due to their public health threat. Extracelluar ARGs (eARGs) can result in the dissemination of antibiotic resistance via free-living ARGs in natural environments, where they promote ARB transmission in drinking water distribution systems. However, eARG pollution in tap water has not been well researched. In this study, concentrations of eARGs and intracellular ARGs (iARGs) in tap water, sampled at Tianjin, China, were investigated for one year. Fourteen eARG types were found at the highest concentration of 1.3 × 10⁵ gene copies (GC)/L. TetC was detected in 66.7% of samples, followed by sul1, sul2, and qnrA with the same detection frequency of 41.7%. Fifteen iARGs (including tetA, tetB, tetM, tetQ, tetX, sul1, sul2, sul3, ermB, blaTEM, and qnrA) were continuously detected in all collected tap water samples with sul1 and sul2 the most abundant. Additionally, both eARG and iARG concentrations in tap water presented a seasonal pattern with most abundant prevalence in summer. The concentration of observed intracellular sulfonamide resistance genes showed a significantly positive correlation with total nitrogen concentrations. This study suggested that eARG and iARG pollution of drinking water systems pose a potential risk to human public health.