Abstract
Atmospheric nitrogen deposition (AND) may lead to water acidification and eutrophication. In the five months after December 2019, China took strict isolation and COVID-19 prevention measures, thereby causing lockdowns for approximately 1.4 billion people. The Danjiangkou Reservoir refers to the water source in the middle route of South-to-North Water Diversion Project in China, where the AND has increased significantly; thus, the human activities during the COVID-19 period is a unique case to study the influence of AND to water quality. This work monitored the AND distribution around the Danjiangkou Reservoir, including agricultural, urban, traffic, yard, and forest areas. After lockdown, the DTN, DON, and Urea-N were 1.99 kg · hm−2 · month−1, 0.80 kg · hm−2 · month−1, and 0.15 kg · hm−2 · month−1, respectively. The detected values for DTN, DON, and Urea-N in the lockdown period decreased by 9.6%, 30.4%, and 28.97%, respectively, compared to 2019. The reduction in human activities is the reason for the decrease. The urban travel intensity in Nanyang city reduced from 6 to 1 during the lockdown period; the 3 million population which should normally travel out from city were in isolation at home before May. The fertilization action to wheat and orange were also delayed.
Highlights
The results show that the maximum concentration of dissolved organic nitrogen (DON) in rainwater is
In 2020, the DTN in the early lockdown period was 1.83 kg · hm−2 · month−1, and the monthly average DTN during the middle epidemic lockdown period was 1.99 kg · hm−2 · month−1, which is an increase of 8.7%
The Danjiangkou reservoir is located between Henan and Hubei province, which is the upstream of the Hanjiang River, a tributary of the Yangtze River
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Human activities have an important impact on atmospheric nitrogen deposition (AND). The Danjiangkou reservoir is located between Hubei and Henan province It is the water source of the middle route of the South-to-North Water Diversion Project in China. According to the data of Henan annual report on environmental quality, the total nitrogen content in the reservoir area is 1.0–1.5 mg/L, exceeding the class III water quality standard of surface water (applicable to the surface water source of centralized domestic and drinking water), which has become the main factor that affects the water quality safety of the Danjiangkou reservoir [18]. This work studies the impact of human activities on the AND before and after the COVID-19 lockdown in the Xichuan reservoir area in the Danjiangkou Reservoir. The early epidemic period is before January 2020, in which the cities were about to lockdown [22]. The nitrogen deposition data will be compared with the same period in 2019 to investigate the impact of human activity on the nitrogen deposition
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