[Characteristics of Soil NO Emissions in the Yangtze River Delta Region for Year 2018].

Soil NO emissions represent an important source of atmospheric nitric oxide (NO) and play an important role in atmospheric chemistry. Based on the latest BDSNP algorithm, this study estimated the soil NO emissions over the Yangtze River Delta region for the year 2018 and further analyzed the associated temporal and spatial variations and uncertainties. The results showed that the annual soil NO emissions in 2018 over the YRD region was 213.6 kt, accounting for 7.3% of the total anthropogenic NOx emissions. Areas with high emissions were mainly concentrated in northern Anhui Province and most parts of Jiangsu Province. In terms of monthly variations, soil NO emissions peaked in June, accounting for 19.9% of the annual emissions and 19.7% of anthropogenic NOx emissions in June. In terms of daily variations, soil NO emissions peaked around 16:00 and accounted for 5.5% of daily emissions. Soil NO emissions came from three components:soil background, nitrogen fertilizer application, and nitrogen deposition. Nitrogen fertilizer application was the main source of soil NO emissions, accounting for up to 77.8%. With the in-depth reduction in NOx emissions from motor vehicles and industries, the importance of soil NO emissions will become increasingly prominent.

[Role of Land Use Changes on Ammonia Emissions from Agricultural Ecosystems in the Yangtze River Delta Region from 2000 to 2018].

Based on Landsat satellite remote sensing images, this study interprets land use changes in the Yangtze River Delta (YRD) region from 2000 to 2018. Combined with changes in nitrogen fertilizer application, the changes in ammonia emissions from farmland ecosystem due changes in land use and nitrogen fertilizer application were further investigated. The results show that along with the rapid urbanization process, the area of cultivated land in the YRD region has gradually decreased from 276269 km2 (49% of total land area) in 2000 to 244001 km2 (44%) in 2018. The effects of changes in land use and nitrogen fertilizer application on ammonia emissions from farmland ecosystems mainly include emissions from soil background and nitrogen fertilizer application. From 2000 to 2018, ammonia emissions due to the application of nitrogen fertilizer decreased from 690 kt·a-1 to 541 kt·a-1 (relative decrease by 22%), while the ammonia emissions from the soil background reduced from 32 kt·a-1 to 29 kt·a-1 (decrease by 9%). During the past 20 years, urbanization in the YRD region has accelerated, and the area of cultivated land and the total amount of nitrogen fertilizer application have significantly reduced, thus resulting in reductions in ammonia emissions from the farmland ecosystem.