Environmental context. Atmospheric particulate NH₄⁺, primarily produced from the reaction of NH₃ and acids, is an important component of PM_2.5. In this study, nitrogen stable isotope analyses and an atmospheric chemistry model were used to estimate the contribution of major NH₃ sources to particulate NH₄⁺ in Tianjin, a megacity in North China Plain (NCP). Our research has implications for investigations of NH₃ emission sources and relevant pollution control in Tianjin and NCP. Photograph by Libin Wu.

This article belongs to the collection Dedication to Roy Harrison.

Environmental context. This manuscript focuses on the introduction of the conventional and modified Solvay processes. The Solvay process is used to produce sodium carbonate and sodium bicarbonate, while also providing brine management and CO₂ capture. Optimal values must be used for reactant contents, temperature, salinity of the brine and stirring rate to enhance efficiency. (Image of the schematic diagram reproduced from Mourad et al. 2021 with permission.)

Environmental context. The widespread use of pesticides leads to a large amount of residues in natural waters where photochemical degradation is the main removal process. The factors influencing the photodegradation of pyrimethanil were investigated in different aqueous matrixes, and a chlorinated product was found in saline water, indicating a higher ecological risk of residual pyrimethanil in estuarine and nearshore water than in fresh water. A better understanding of the natural degradation mechanisms for pesticides will inform their safer use in agriculture. (Image credit: Jiayun Zhao.)