Drought has been one of the most important limiting factors for crop production, which deleteriously affects food security worldwide. The main objective of the present study was to quantitatively assess the effect of drought on the agronomic traits (e.g., plant height, biomass, yield, and yield components) of rice and wheat in combination with several moderators (e.g., drought stress intensity, rooting environment, and growth stage) using a meta-analysis study. The database was created from 55 published studies on rice and 60 published studies on wheat. The results demonstrated that drought decreased the agronomic traits differently between rice and wheat among varying growth stages. Wheat and rice yields decreased by 27.5% and 25.4%, respectively. Wheat grown in pots showed greater decreases in agronomic traits than those grown in the field. Rice showed opposite growing patterns when compared to wheat in rooting environments. The effect of drought on rice increased with plant growth and drought had larger detrimental influences during the reproductive phase (e.g., blooming stage, filling stage, and maturity). However, an exception was found in wheat, which had similar decreased performance during the complete growth cycle. Based on these results, future droughts could produce lower yields of rice and wheat when compared to the current drought.

Food safety is a major concern for the Chinese public. This study collected 465 published papers on heavy metal pollution rates (the ratio of the samples exceeding the Grade II limits for Chinese soils, the Soil Environmental Quality Standard-1995) in farmland soil throughout China. The results showed that Cd had the highest pollution rate of 7.75%, followed by Hg, Cu, Ni and Zn, Pb and Cr had the lowest pollution rates at lower than 1%. The total pollution rate in Chinese farmland soil was 10.18%, mainly from Cd, Hg, Cu, and Ni. The human activities of mining and smelting, industry, irrigation by sewage, urban development, and fertilizer application released certain amounts of heavy metals into soil, which resulted in the farmland soil being polluted. Considering the spatial variations of grain production, about 13.86% of grain production was affected due to the heavy metal pollution in farmland soil. These results many provide valuable information for agricultural soil management and protection in China.

It is well known that vegetation has cooling effect on urban land surface temperature (ULST). However, the influence of vegetation's structure, component, and spatial distribution on ULST has rarely been quantitatively studied. This paper, taking Landsat ETM+ data to retrieve ULST, and IKONOS data to obtain vegetation information, studied the relationship between ULST and vegetation patches. Results showed that in the urban environment, (1) ULSTs over tree and shrub, lawn, and weed patches were not much different, because of the edge effects of the vegetation patches and their fragmentized distribution pattern; (2) the relationship between ULST and area, perimeter, and shape index of vegetation patches exhibited positive, while LST and the ratio of perimeter/area presented negative linear relationship; (3) using land use polygons as units, area density had quadratic curve relationship to ULST, edge density and mean area density, had strongly negative relationship to ULST. These results indicated that not only the characteristics of vegetation patches, but also their spatial distribution had a great effect on ULST, which should be considered in urban ecological environment management.

Ammonia (NH₃), as an alkaline gas in the atmosphere, can cause direct or indirect effects on the air quality, soil acidification, climate change and human health. Estimating surface NH₃ concentrations is critically important for modeling the dry deposition of NH₃ and for modeling the formation of ammonium nitrate, which have important impacts on the natural environment. However, sparse monitoring sites make it challenging and difficult to understand the global distribution of surface NH₃ concentrations in both time and space. We estimated the global surface NH₃ concentrations for the years of 2008–2016 using satellite NH₃ retrievals combining vertical profiles from GEOS-Chem. The accuracy assessment indicates that the satellite-based approach has achieved a high predictive power for annual surface NH₃ concentrations compared with the measurements of all sites in China, the US and Europe (R²=0.76 and RMSE = 1.50 µg N m⁻³). The satellite-derived surface NH₃ concentrations had higher consistency with the ground-based measurements in China (R²=0.71 and RMSE = 2.6 µg N m⁻³) than the US (R²=0.45 and RMSE = 0.76 µg N m⁻³) and Europe (R²=0.45 and RMSE = 0.86 µg N m⁻³) at a yearly scale. Annual surface NH₃ concentrations higher than 6 µg N m⁻³ are mainly concentrated in the North China Plain of China and northern India, followed by 2–6 µg N m⁻³ mainly in southern and northeastern China, India, western Europe, and the eastern United States (US). High surface NH₃ concentrations were found in the croplands in China, the US and Europe, and surface NH₃ concentrations in the croplands in China were approximately double those in the croplands in the US and Europe. The linear trend analysis shows that an increase rate of surface NH₃ concentrations (> 0.2 µg N m⁻³ yr⁻¹) appeared in eastern China during 2008–2016, and a middle increase rate (0.1–0.2 µg N m⁻³ yr⁻¹) occurred in northern Xinjiang over China. NH₃ increase was also found in agricultural regions in the central and eastern US with an annual increase rate of lower than 0.10 µg N m⁻³ yr⁻¹. The satellite-derived surface NH₃ concentrations help us to determine the NH₃ pollution status in the areas without monitoring sites and to estimate the dry deposition of NH₃ in the future.