Seminar

Nitrogen deposition plays an important role in both air and water quality. Nitrogen emissions in cities are high mainly due to transportation and industrial activities and predicted to further increase. As nitrogen is often the limiting nutrient in coastal waters, the excess nitrogen may enhance the phytoplankton growth, resulting in eutrophication and hypoxia. Thus, understanding the nitrogen sources and its potential impacts are crucial to mitigate the nitrogen pollution in coastal waters. Therefore, multi stable isotope analysis of dry deposition (δ15N, δ34S, δ13C) were measured in Hong Kong to identify the atmospheric sources of nitrogen and the seasonal trend. Furthermore, dual isotopes of nitrate from the atmospheric deposition was analyzed which is useful for partitioning N sources in seawaters. The δ15N of the atmospheric deposition exhibited a seasonal pattern in Hong Kong, which indicated a shift of N sources between winter and summer. This might be driven by the Asian monsoon system. In addition, I examined the impact of the future trend of nitrogen deposition in China on the oxygen budget. Specifically, I used a biogeochemical model to estimate the future hypoxic area of such deposition, suggesting that reducing nitrogen deposition can reduce the hypoxic area. With the predicted increase in precipitation and atmospheric N deposition over Hong Kong, this may alter the local N cycling, thus monitoring of the atmospheric deposition is important for coastal cities. 

Zoom: https://tinyurl.com/y3r3ogqd 
(Meeting ID: 993 5674 8668)

Please contact Miss YAU Yu Yan u3511209@hku.hk  for zoom password