Hourly emissions of air pollutants and greenhouse gases from open biomass burning in China during 2016-2020.

Open biomass burning (OBB) is a significant source of air pollutants and greenhouse gases that have contributed to air pollution episodes in China in recent years. An accurate emission inventory is critical for the precise control of OBB. Existing OBB emission datasets are commonly based on MODIS observations, and most only have a daily-scale temporal resolution. Daily OBB emissions, however, might not accurately represent diurnal variations, peak hours, or any open burning processes. The China Hourly Open Biomass Burning Emissions (CHOBE) dataset for mainland China from 2016 to 2020 was developed in this study using the spatiotemporal fusion of multiple active fires from MODIS, VIIRS S-NPP and Himawari-8 AHI detections. At a spatial resolution of 2 km, CHOBE provided gridded CO, NOx, SO2, NH3, VOCs, PM2.5, CO2, CH4 and N2O emissions from OBB. CHOBE will enhance insight into OBB spatiotemporal variability, improves air quality and climate modelling and forecasting, and aids in the formulation of precise OBB preventive and control measures.

Combined Effects of Elevated O3 Concentrations and Enhanced UV-B Radiation of the Biometric and Biochemical Properties of Soybean Roots.

Enhanced ultraviolet-B (UV-B) radiation and elevated tropospheric ozone alone may inhibit the growth of agricultural crops. However, research regarding their combined effects on growth and biochemical properties of roots is still scarce. Using open top chambers, we monitored the response of growth, secondary metabolites, endogenous hormones and enzyme activities of soybean roots to elevated O3 and enhanced UV-B individually and in combination at stages of branching, flowering and podding. Our results indicated that the root biomass decreased by 23.6, 25.2, and 27.7%, and root oxidative capacity declined by11.2, 39.9, and 55.7% exposed to elevated O3, enhanced UV-B, and O3 + UV-B, respectively, compared to the control treatment. Concentrations of quercetin and ABA were significantly increased, while concentrations of total polyphenol and P-coumaric acid responded insignificantly to elevated O3, enhanced UV-B, and O3 + UV-B during the whole period of soybean growth. Elevated O3, enhanced UV-B and O3 + UV-B showed significant negative effects on superoxide dismutase (EC 1.15.1.1) activity at flowering stage, on activities of peroxidase (EC 1.11.1.7) and catalase (EC 1.11.1.6) at podding stage, on ascorbate peroxidase activity during the whole period of soybean growth. Moreover, compared to hormones and enzyme activity, secondary metabolisms showed stronger correlation with root growth exposed to elevated O3 and enhanced UV-B individually and in combination. Our study concluded that combined effects of O3 and UV-B radiation significantly exacerbated the decline of soybean root growth, and for annual legumes, the inhibited root growth exposed to O3 and/or UV-B radiation was mostly associated with secondary metabolisms (especially flavonoids).

Combined effects of O3 and UV radiation on secondary metabolites and endogenous hormones of soybean leaves.

Enhanced ultraviolet radiation (UV) and elevated tropospheric ozone (O3) may individually cause reductions in the growth and productivity of important agricultural crops. However, research regarding their combined effects on important agricultural crops is still scarce, especially on changes in secondary metabolites and endogenous hormones, which are important protective substances and signal components that control plant responses to environment stresses. In this study, using an experimental setup of open top chambers, we monitored the responses of seed yield per plant, leaf secondary metabolites and leaf endogenous hormones under the stress of elevated O3 and enhanced UV radiation individually, as well as their combined stress. The results indicated that elevated O3 (110 ± 10 nmol mol-1 for 8 hours per day) and enhanced UV radiation (1.73 kJ h-1 m-2) significantly decreased seed yield per plant. Concentrations of rutin, queretin and total flavonoids were significantly increased under the elevated O3 treatment or the enhanced UV radiation treatment or the combination treatment at flowering and podding stages, and concentrations of rutin, queretin and total flavonoids showed significant correlations with seed yield per plant. Concentrations of ABA and IAA decreased under the three treatments. There was a significant positive correlation between the ABA concentration and seed yield and a negative correlation between the IAA concentration and seed yield. We concluded that the combined stress of elevated O3 and UV radiation significantly decreased seed yield per plant. Yield reduction was associated with changes in the concentrations of flavonoids, ABA and IAA in soybean leaves. The effects of the combined O3 and UV stress were always greater than those of the individual stresses alone.