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With the vigorous implementation of the Clean Air Action since 2013, the atmospheric particle pollution in China has been substantially reduced, but ozone concentrations have been increasing. Moreover, tropospheric ozone can make a difference in meteorology and air quality through its radiative forcing as an important greenhouse gas. A coupled regional meteorology-chemistry model (WRF-Chem) was used to reproduce an ozone pollution event that occurred in North China in June 2017. The impact of tropospheric ozone radiative forcing on local meteorological fields and its feedback effect on ozone air quality were analyzed through sensitivity experiments. The results revealed the excellent performance of the WRF-Chem model for meteorological parameters and ozone pollutant concentrations. Tropospheric ozone radiative forcing (TORF) increased the average near-surface temperature by 0.23 K in the Beijing-Tianjin-Hebei-Shandong Region (the maximum temperature increase could reach 0.8 K), reduced the relative humidity by 1.84%, and elevated the height of the boundary layer by 27.73 m. TORF had a weaker effect on wind speed (-0.02 m·s -1 ), but the generated anomalous southwestern wind was more liable to transport ozone and its precursors from upstream polluted areas to North China. Under the impacts of ozone radiation feedback, the ozone volume fraction in the study area increased by an average of 1.7% (1.23×10 -9 ), whereas in the heavily polluted Beijing and Tianjin areas, the increase reached up to 5×10 -9 . Furthermore, the enhanced gas phase chemical reactions were identified as the dominant cause worsening near-surface ozone pollution by progress diagnostic analysis.

Tropospheric ozone (O 3 ) is a phytotoxic pollutant that leads to a reduction in crop yield. Nanotechnology offers promising solutions to stem such yield losses against abiotic stresses. Silver nanoparticles are major nanomaterials used in consumer products however, their impact on crops under abiotic stress is limited. In this study, we evaluated the anti-ozonant efficacy of biogenic silver nanoparticles (B-AgNPs) and compared them with a model anti-ozonant ethylenediurea (EDU) against ozone phyto-toxicity. Growth, physiology, antioxidant defense, and yield parameters in two wheat cultivars (HD-2967 & DBW-17), treated with B-AgNPs (25 mg/L and 50 mg/L) and EDU (150 mg/L and 300 mg/L), were studied at both vegetative and reproductive stages. During the experimental period, the average ambient ozone concentration and accumulated dose of ozone over a threshold of 40 ppb (AOT40) (8 h day -1 ) were found to be 60 ppb and 6 ppm h, respectively, which were sufficient to cause ozone-induced phyto-toxicity in wheat. Growth and yield for B-AgNPs as well as EDU-treated plants were significantly higher in both the tested cultivars over control ones. However, 25 mg/L B-AgNPs treatment showed a more pronounced effect in terms of yield attributes and its lower accumulation in grains for both cultivars. DBW-17 cultivar responded better with B-AgNPs and EDU treatments as compared to HD-2967. Meanwhile, foliar exposure of B-AgNPs (dose; 25 mg/L) significantly enhanced grain weight plant -1 , thousand-grain weight, and harvest index by 54.22 %, 29.46 %, and 14.21 %, respectively in DBW-17, when compared to control. B-AgNPs could enhance ozone tolerance in wheat by increasing biochemical and physiological responses. It is concluded that B-AgNPs at optimum concentrations were as effective as EDU, hence could be a promising ozone protectant for wheat., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Tropospheric ozone is a major air pollutant that significantly damages crop production. Crop metabolic responses to rising chronic ozone stress have not been well studied in the field, especially in C 4 crops. In this study, we investigated the metabolomic profile of leaves from two diverse maize ( Zea mays ) inbred lines and the hybrid cross during exposure to season-long elevated ozone (~100 nl L -1 ) in the field using free air concentration enrichment (FACE) to identify key biochemical responses of maize to elevated ozone. Senescence, measured by loss of chlorophyll content, was accelerated in the hybrid line, B73 × Mo17, but not in either inbred line (B73 or Mo17). Untargeted metabolomic profiling further revealed that inbred and hybrid lines of maize differed in metabolic responses to ozone. A significant difference in the metabolite profile of hybrid leaves exposed to elevated ozone occurred as leaves aged, but no age-dependent difference in leaf metabolite profiles between ozone conditions was measured in the inbred lines. Phytosterols and α-tocopherol levels increased in B73 × Mo17 leaves as they aged, and to a significantly greater degree in elevated ozone stress. These metabolites are involved in membrane stabilization and chloroplast reactive oxygen species (ROS) quenching. The hybrid line also showed significant yield loss at elevated ozone, which the inbred lines did not. This suggests that the hybrid maize line was more sensitive to ozone exposure than the inbred lines, and up-regulated metabolic pathways to stabilize membranes and quench ROS in response to chronic ozone stress., Competing Interests: The authors declare no conflict of interest associated with the work described in this Manuscript., (© 2021 The Authors. Plant Direct published by American Society of Plant Biologists, Society for Experimental Biology and John Wiley & Sons Ltd.)

Japanese larch ( Larix kaempferi (Lamb.) Carr.) and its hybrid are economically important coniferous trees widely grown in the Northern Hemisphere. Ground-level ozone (O 3 ) concentrations have increased since the pre-industrial era, and research projects showed that Japanese larch is susceptible to elevated O 3 exposures. Therefore, methodologies are needed to (1) protect Japanese larch against O 3 damage and (2) conduct biomonitoring of O 3 in Japanese larch forests and, thus, monitor O 3 risks to Japanese larch. For the first time, this study evaluates whether the synthetic chemical ethylenediurea (EDU) can protect Japanese larch against O 3 damage, in two independent experiments. In the first experiment, seedling communities, simulating natural regeneration, were treated with EDU (0, 100, 200, and 400 mg L -1 ) and exposed to either ambient or elevated O 3 in a growing season. In the second experiment, individually-grown saplings were treated with EDU (0, 200 and 400 mg L -1 ) and exposed to ambient O 3 in two growing seasons and to elevated O 3 in the succeeding two growing seasons. The two experiments revealed that EDU concentrations of 200-400 mg L -1 could protect Japanese larch seedling communities and individual saplings against O 3 -induced inhibition of growth and productivity. However, EDU concentrations ≤ 200 mg L -1 did offer only partial protection when seedling communities were coping with higher level of O 3 -induced stress, and only 400 mg EDU L -1 fully protected communities under higher stress. Therefore, we conclude that among the concentrations tested the concentration offering maximum protection to Japanese larch plants under high competition and O 3 -induced stress is that of 400 mg EDU L -1 . The results of this study can provide a valuable resource of information for applied forestry in an O 3 -polluted world., (© The Author(s) 2020.)