Coral carbonate-bound isotopes reveal monsoonal influence on nitrogen sources in Southeastern China's Greater Bay Area from the mid-Holocene until the Anthropocene.

Most anthropogenic nitrogen (N) reaches coastal waters via rivers carrying increasing loads of sewage, fertilizer, and sediments. To understand anthropogenic N impacts, we need to understand historical N-dynamics before human influence. Stable isotope ratios of N preserved in carbonates are one way to create temporal N records.

Elucidating sources of atmospheric NO pollution in a heavily urbanized environment using multiple stable isotopes.

Atmospheric deposition of nitrogen (N) from rain and aerosols can be a significant non-point source - particularly in urbanized coastal areas and contribute to coastal eutrophication and hypoxia. Here, we present geochemical and isotopic data from surface waters coupled with an 18-month time series of geochemical and isotopic data measured on wet and dry deposition over Hong Kong from June 2018. Dual stable isotopes of nitrate (δN-NO and δO-NO) of rain and total suspended particulates (TSP) were analyzed to trace the sources and understand seasonal pattern of atmospheric nitrate.

Substantial decrease in CO emissions from Chinese inland waters due to global change.

Carbon dioxide (CO) evasion from inland waters is an important component of the global carbon cycle. However, it remains unknown how global change affects CO emissions over longer time scales. Here, we present seasonal and annual fluxes of CO emissions from streams, rivers, lakes, and reservoirs throughout China and quantify their changes over the past three decades.

Investigating the link between Pearl River-induced eutrophication and hypoxia in Hong Kong shallow coastal waters.

We present geochemical analysis of 75 surface water samples collected in 2016 in Hong Kong coastal waters. We found that nitrogen distribution around Hong Kong can be characterized by two regimes driven by the influence of the Pearl River: 1) a regime where nitrate is the dominant species of nitrogen, associated with lower salinity and more faecal coliform and 2) a regime where dissolved organic nitrogen is dominant, associated with higher salinity and fewer faecal coliform. While the impact of the Pearl River on Hong Kong coastal waters is well characterized, we used the sharp contrast between the nitrogen regimes to produce new evidence about the role of the Pearl River on the generation of local hypoxia in Hong Kong.

Nitrogen sources and cycling revealed by dual isotopes of nitrate in a complex urbanized environment.

Elevated nutrient inputs have led to increased eutrophication in coastal marine ecosystems worldwide. An understanding of the relative contribution of different nutrient sources is imperative for effective water quality management. Stable isotope values of nitrate (δN, δO) can complement conventional water quality monitoring programs to help differentiate natural sources of NO from anthropogenic inputs and estimate the processes involved in N cycling within an ecosystem.