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Parabens are widely employed in toothpaste, cosmetics, textiles, beverages, and preservatives, causing a serious environmental concern because they are endocrine-disrupting compounds (EDCs). As one of the highly reactive oxidants, ozone has a great effect on EDC removal. To understand the degradation and transformation of parabens in the aquatic environment and their toxicity to aquatic organisms, the degradation reaction of parabens initiated by O3 was studied meticulously using quantum chemical calculations. The degradation process includes multiple initial reaction channels and consequent degradation pathways of the Criegee intermediates. Through thermodynamic data, the rate constants were computed using the transition state theory (TST). At a temperature of 298 K and a pressure of 1 atm, the calculated rate constants were 3.92 and 3.94 M-1 s-1 for methylparaben (MPB) and ethylparaben (EPB), respectively. The rate constants increased as the temperature increased or as the length of the alkyl chain on the benzene ring increased. Through the ecotoxicity assessment procedure, the ecotoxicity of parabens and the products in the degradation process can be assessed. Most degradation byproducts are either less toxic or nontoxic. Some byproducts are still harmful, such as oxalaldehyde (P2) and ethyl 2,3-dioxopropanoate (P10). Furthermore, the ecological toxicity of parabens increased with augmentation of the alkyl chain on the benzene ring. The effect of the alkyl chain length on the benzene ring in the compound cannot be ignored.

As one of the main components of combustion of tobacco products occurs (CARB), crotonaldehyde has an acute toxicity and widely exists in the atmosphere, which is harmful to human health. The removal efficiency of VOCs by ozonation can reach 80–90%. Based on the theory of quantum chemistry, the degradation mechanism, kinetics and toxicity of crotonaldehyde by ozonation in gas phase and heterogeneous phase were studied. Ozone was added to the olefins unsaturated double bond to form a five-membered ring primary ozonide, which was further fractured due to its unstable structure to form a Criegee intermediate and an aldehyde compound. The reaction rate constant of crotonaldehyde with ozone was 1.24 × 10−17 cm3 molecule−1 s−1 at 298 K and 1 atm, which was an order of magnitude higher than the experimental value. From toxicity assessment, it was found that the ozonation of crotonaldehyde is beneficial to the removal of toxicity. Mineral dust aerosol exists in the atmosphere in large quantities, and SiO2 is the most abundant component. VOCs are transformed into particle state on their surface through homogeneous nucleation and heterogeneous nucleation. Referring to the crystal structure of SiO2, five hydroxylated silica oligomer cluster structures were simulated and the adsorption configurations of crotonaldehyde on their surface were simulated. The adsorption of crotonaldehyde on the surface of the clusters was achieved by forming hydrogen bonds and had good adsorption effects. The adsorption of hydroxylated silica oligomer clusters didn't change the ozonation mechanism of crotonldehyde, but had a certain effect on the reaction rate.

Pesticides occur in the environment as mixtures, yet the joint toxicity of pesticide mixtures remains largely under-explored and is usually overlooked in ecological risk assessment. In the current study, joint toxicity of a neonicotinoid insecticide (imidacloprid, IMI) and a strobilurin fungicide (azoxystrobin, AZO) was investigated with Chironomus dilutus over a wide range of concentrations and at different effect levels (organism, cell, and gene levels). The two pesticides, both individually and in combination, were found to induce oxidative stress and cause lethality in C. dilutus. Median lethal concentrations for IMI and AZO were 3.98 ± 1.17 and 52.9 ± 1.1 μg/L, respectively. Mixtures of the two pesticides presented synergetic effects at environmentally relevant concentrations whilst antagonistic effects at high concentrations, showing concentration-dependent joint toxicity. Investigation on the expressions of 12 genes (cyt b, coi, cox1, cyp4, cyp12m1, cyp9au1, cyp6fv1, cyp315, gst, Zn/Cu-sod, Mn-sod, and cat) revealed that the two pesticides impaired mitochondrial respiration, detoxification, and antioxidant system of C. dilutus, and the joint effects of the two pesticides were likely due to an interplay between their respective influences on these physiological processes. Collectively, the synergistic effects of the two pesticides at environmentally relevant concentrations highlight the importance to incorporate combined toxicity studies into ecological risk assessment of pesticides.

Neonicotinoid insecticides have posed a great threat to non-target organisms, yet the mechanisms underlying their toxicity are not well characterized. Major modes of action (MoAs) of imidacloprid were analyzed in an aquatic insect Chironomus dilutus. Lethal and sublethal outcomes were assessed in the midges after 96-h exposure to imidacloprid. Global transcriptomic profiles were determined using de novo RNA-sequencing to more holistically identify toxicity pathways. Transcriptional 10% biological potency values derived from ranked KEGG pathways and GO terms were 0.02 (0.01–0.08) (mean (95% confidence interval) and 0.05 (0.04–0.06) μg L−1, respectively, which were more sensitive than those from phenotypic traits (10% lethal concentration: 0.44 (0.23–0.79) μg L−1; 10% burrowing behavior concentration: 0.30 (0.22–0.43) μg L−1). Major MoAs of imidacloprid in aquatic species were identified as follows: the activation of nicotinic acetylcholine receptors (nAChRs) induced by imidacloprid impaired organisms’ nerve system through calcium ion homeostasis imbalance and mitochondrial dysfunction, which posed oxidative stress and DNA damage and eventually caused death of organisms. The current investigation highlighted that imidacloprid affected C. dilutus at environmentally relevant concentrations, and elucidated toxicity pathways derived from gene alteration to individual outcomes, calling for more attention to toxicity of neonicotinoids to aquatic organisms.

In this paper, the gas-phase and heterogeneous reactions of acrolein with ozone were studied comprehensively and deeply. Acrolein is one of the simplest unsaturated aldehydes found widely in the fuel combustion and industrial emissions. Mineral particles produced by frequent sandstorms have important effects on the tropospheric chemistry and the climate change. The content of silica in clay minerals is rich, thus three kinds of clusters (the monomeric model Si(OH)4, the linear model Si3O2(OH)8 and the cyclic hexamer model Si6O6(OH)12) were selected for the heterogeneous study. The reaction rate constant of acrolein with ozone at 298 K and 1 atm was 7.46 × 10−18 cm3 molecule−1 s−1, which was in agreement with the experimental value. SiO2 clusters interacted with acrolein via the hydrogen bonds and had good adsorption properties. The hydrogen bond between the oxygen of aldehyde group on acrolein and the hydrogen of silica surface was stronger and the adsorption energy was greater. The adsorption of silanol groups did not change the ozonation mechanism of acrolein, but had effects on the reaction rate. Among them, three silanol groups acted as positive catalysts. The kinetic data within the temperature range of 216.65–288.15 K corresponding to the height of the troposphere at 0–11 km showed that the rate constant of O3-initiated reaction of acrolein is positively correlated with the temperature. In addition, we also studied the reaction mechanism and kinetic of the Criegee intermediates reacting with atmospheric small molecules and isomerization process in gas-phase and heterogeneous processes.

A variety of chemicals are capable of provoking mitochondrial dysfunction and thereby contribute to metabolic disorder related effects in wildlife and human. For better identifying new mitochondrial toxicants and assessing mitochondria-related risk, an in-depth understanding of toxic mechanisms and biomarkers should be attained. In the current study, a representative mitotoxicant, azoxystrobin, was assessed for lethal and sublethal outcomes in Chironomus dilutus after 96-h exposure and the toxic mechanism was explored. Global transcriptomic profiles by RNA-sequencing revealed that ampk, acc1, atp2a, gsk3b, pi3k, fak, atr, chk1, and map3k5 were the key genes which involved in the toxic action of azoxystrobin and could serve as potential molecular biomarkers. A major network of common toxicity pathways was then developed for mitotoxicants towards aquatic insects. In particular, calcium ion-PI3K/AKT and cAMP-AMPK-lethality pathways were demonstrated, in addition to the well-known mitochondrial electron transfer-oxidative damage-apoptosis pathway. These analyses could help developing adverse outcome pathways that integrate toxicological information at various levels and support more effective risk assessment and management of mitotoxicants.

The corrosion inhibition of iron in 0.5 M H2SO4 solutions by alkyl quaternary ammonium halides (AQAH) inhibitors has been studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements. The correlation between inhibition efficiency and molecular structure of the AQAH compounds is investigated. The results show that besides the concentration, the structure of alkyl groups and the type of halide ions of these AQAH inhibitors greatly influence the inhibition efficiency. Data obtained from EIS measurements are analyzed to model the corrosion inhibition process through appropriate equivalent circuit models.

Platinum dispersed in polyaniline film is a better catalyst than bulk platinum for methanol electrooxidation in sulfuric acid solution. The effect of deposition modes of platinum particles on their electrocatalytic activity has been studied. Several electrodeposition methods, including constant potential, cyclic potential and double potential step, have been applied to characterize the performance of different electrodeposition modes. Besides the variation of the electrodeposition methods, rotating disk electrode technique is applied to disperse Pt particles under the control of convection–diffusion condition. The results show that the enhanced electrocatalytic activity may be due to the dispersion of Pt particles in the polyaniline film matrix and the synergistic effects between the dispersed Pt particles and the polyaniline film. Variables related to reaction kinetics, such as mass transport of species, concentration of methanol and acidity of solution, are investigated and reaction mechanism for methanol oxidation is discussed.

The composite electrode of platinum-modified polyaniline film is formed in 0.5 M H 2 SO 4 + 3 mM H 2 PtCl 6 solution by cyclic potential or constant potential deposition of platinum particles in polyaniline film. To make a comparison, the polyaniline film with the same initial thickness and structure is also treated with the cyclic potential or constant potential polarization in 0.5 M H 2 SO 4 solution. The electrochemical impedance spectroscopy (EIS) of the composite electrode of platinum-modified polyaniline film is studied in sulfuric acid solution and compared with the EIS of the polyaniline film without platinum dispersion. The results show that the different modes of potential polarization affect greatly the nature and distribution of the platinum particles, instead of the structure of the polyaniline film (matrix). The electrode reaction kinetics and mass transport process parameters involving charge transfer resistance (R c t ), double layer capacitance (C d l ), constant phase elements (CPE) and Warburg impedance in platinum substrate/platinum-modified polyaniline film/solution interface are discussed on the basis of the interpretation of the characteristic impedance spectra and connected to the electrocatalytic activity on the oxidation of methanol molecules.

The electrocatalytic properties of platinum particles incorporated into polyaniline films are investigated for oxidation of methanol in sulfuric acid electrolyte. It is found that the oxidation of methanol depends greatly on the nature of both polyaniline matrix and platinum particles which can be optimized by the electrochemical formation conditions, such as cycle numbers, sweep rates and potential limits.

The electrochemical impedance spectroscopy of a platinum-modified polyaniline film formed by cycling potential or constant potential deposition of platinum particles in polyaniline film is studied in sulfuric acid solution. The results show that compared with the pure polyaniline film ∣ H 2 SO 4 solution interface, the deposition of platinum in the polyaniline matrix greatly reduces the electrochemical charge transfer resistance ( R ct ) in the platinum-modified polyaniline film ∣ H 2 SO 4 solution interface. The surface morphology of the electrodes is observed by scanning electron microscopy. This shows that the different polarization modes affect the nature of the platinum deposits, such as their size, amount, real surface area and distribution in the polymer matrix. The electrocatalytic activity of platinum-modified polyaniline film electrodes for methanol oxidation is discussed on the basis of platinum loading and real surface area which result from varying electrodeposition modes, such as potential limits in cyclic potential polarization or selected potentials in constant potential polarization. Finally, the relationship between impedance characteristic and electrocatalytic activity has been suggested.