The chemical degradation processes of diethyl phthalate (DEP) induced by HO • and SO 4• − in aqueous solution were studied in a theoretical way. Not only radical addition and H-abstraction reactions but also singleelectron transfer processes of DEP were considered. The thermodynamic and kinetic results indicate that the more favorable pathways are the H abstraction occurring in aliphatic side chains for all HO • /SO 4• − -initiated degradation reactions of DEP. Subsequent reaction mechanisms of crucial primary intermediates were taken into account. At 298 K, the total rate constants for DEP degradation reactions induced by HO • and SO 4• − are 2.34 × 10 9 and 1.24 × 10 8 M −1 s −1 , respectively. They are in accordance with the experimental data. In comparison to SO 4• − , HO • has higher reactivity toward DEP in the research temperature range of 273−303 K. Considering the impact on the water ecoenvironment and human health, DEP and its 10 products have no bioaccumulation potential, but most products are developmentally toxic, except for (Z)-ethyl-2,5-dioxopent-3-enoate. Moreover, (Z)-ethyl-2,5-dioxopent-3-enoate is acutely toxic to fish; phthalic acid is mutagenicity positive; and we should pay more attention to them in the future.
The reaction mechanisms and kinetics of 4-methyl-3-penten-2-one (MPO) with atomic Cl have been studied using second-order Møller−Plesset perturbation theory (MP2) and canonical variational transition-state (CVT) theory with smallcurvature tunneling (SCT) correction methods. Eight different reaction paths are considered: two possible Cl addition reactions and six possible hydrogen abstraction reactions. The results of the theoretical investigation indicate that Cl addition dominates the initial reactions of MPO with Cl atoms, and the most energetically favorable pathway is the Cl addition to the double bond carbon adjacent to the carbonyl in the molecule. Among all of the six Habstraction paths, the H abstraction from the two methyl groups linked to the double bond is predicted to occur readily according to the calculated data. In addition, the 1,5-H shift isomerization process, involving the Cl addition mechanism, was proposed and found to be feasible. The major possible products that were detected in experiment and derived from our theoretical study have been identified. The rate constants and branching ratios of the main reaction paths have been obtained over the temperature range of 180−380 K. The total rate constants are dependent on temperature and the Arrhenius equation is fitted as k total = (2.99 × 10 −13 )exp(1795.60/T). The atmospheric lifetime is also estimated and shows a positive temperature dependence.
In recent years, the ever-changing climate has caused natural disasters in various countries to occur frequently. Climate change has become one of the factors that have caused this country to be vulnerable. This article mainly quantitatively studies how climate change affects regional instability. A comprehensive indicator evaluation method is used to establish a PSA model. The country's vulnerability is defined in terms of the dimensions of pressure, sensitivity, and adaptive capability. This article selected Philippines as the research object, and based on the data processing by PSA model, we obtained the Fragile State Index (FSI) of Philippines in the past ten years. It has found that the flooding in 2012 has made it more vulnerable to Philippines and the results of the analysis are in line with the actual situation. Then, the K-means clustering algorithm is used to get a tipping point (0.5) that can define whether it is fragile or not. What's more, the critical point is verified to be reasonable. Finally, under the guidance of the data of the three dimensions and first-class indicators, the intervention measures that the country should take to address climate change are proposed to reduce regional instability.
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