Dry deposition of ammonia around paddy fields in the subtropical hilly area in southern China

Abstract

This study measured the ammonia (NH 3 ) concentration and dry deposition within 100 m around paddy fields (0.6 ha) with double rice cropping in the subtropical hilly area in southern China, with the aims to quantify the dry deposition of NH 3 around the emission source and to clarify its temporal and spatial variability. The results showed that high NH 3 concentrations were found during the 15 d after nitrogen (N) fertilizer application at downwind sites within 100 m around the paddy fields, and the NH 3 concentrations were 12-62, 2.8-7.3, 13-38, and 4.9-36 μg N m −3 during the 15 d after basal fertilizer application and topdressing in the early rice season and after basal fertilizer application and topdressing in the late rice season, respectively. The NH 3 concentrations were relatively low (1.5--3.8 μg N m −3 ) during other periods of the rice season at the downwind sites, which indicated that N fertilizer application in paddy fields highly affected the NH 3 concentration at downwind sites. The NH 3 concentrations at the downwind sites decreased significantly with the increase in distance from the paddy fields. The total NH 3 dry deposition around 100 m of the paddy fields accounted for approximately 79% and 81% of the emitted NH 3 from the paddy fields in the early and late rice seasons, respectively. The results indicate that dry deposition of NH 3 around emission sources may be an important way to remove the NH 3 volatilized from croplands in this subtropical hilly area.亚热带丘陵区稻田周边氨气干沉降研究 摘要 农业源在氨 (NH 3 ) 排放清单中占比较大, 但农业排放的NH 3 是否全部进入大气亟待评估。本文选 择亚热带丘陵区双季稻田为研究对象, 研究了农田排放NH 3 的去向和沉降过程。结果表明, 稻田 (0.6 ha) 下风向 100 m范围较高的NH 3 浓度主要出现在施用基肥和追肥后15 d内。随着距稻田距 离的增加, 下风向大气中NH 3 浓度呈指数下降。稻田下风向 100 m范围内NH 3 沉降量约占挥发量 的80%, 表明近源沉降是亚热带丘陵区稻田排放NH 3 的重要汇机制。该机制大幅减少了农业排放 NH 3 进入大气的总量, 应该在清单编制过程中予以考虑, 以期客观评价农业排放对大气污染的潜 在影响。 ARTICLE HISTORY

Toward a better understanding of cascading consequences of atmospheric reactive nitrogen along its transport pathway

“…Mitigation of atmospheric ammonia pollution can be achieved not only by decreasing emissions from sources, but also by increasing ammonia deposition around sources. Yi et al (2020) found that 80% of the emitted ammonia was dry deposited within 100 m of the studied paddy fields (0.6 ha) in the subtropical hilly regions of China. Thus, not all volatilized ammonia can enter the atmosphere to form aerosols.…”

Discovery of Brassica Yellows Virus and Porcine Reproductive and Respiratory Syndrome Virus in Diaphorina citri and Changes in Virome Due to Infection with ‘ Ca . L. asiaticus’

“…The complex interactivity between cloud feedback and aerosol-clouds may affect temperatures and humidity in orchards, which can be beneficial to the dispersal of viruses into plants mediated by plant transpiration ( 75 ). Furthermore, nitrogen deposition induces eutrophication and neutralizes the pH of the water, including groundwater and that in escape canals in the limestone mountains, which could increase the risk of microbial aggregation through bridging bacteria ( 74 , 76 ). Due to the lack of nutrition data required by different plants at different growth stages in different climatic regions and the absence of biosensors, even intelligent water and fertilizer integration facilities often cause excessive water and fertilizer irrigation.…”