[Spatiotemporal Characteristics of Dissolved Oxygen and Control Mechanism of Hypoxia (Low Oxygen) in the Watershed-Coastal System in Fujian Province].

Dissolved oxygen is a key parameter to measure water environment quality and ecosystem health. Currently, the problem of hypoxia (low oxygen) is prominent in coastal areas in China, but there is a lack of research on the spatiotemporal characteristics of dissolved oxygen and the control mechanism of hypoxia in the watershed-coastal system. Based on the data of 135 surface water (including estuaries) and 66 coastal water monitoring sites in Fujian Province from 2011 to 2020, this study analyzed the spatiotemporal variation pattern of dissolved oxygen at seasonal and interannual time scales.

[Spatial and Temporal Distribution and Influencing Factors of Dissolved Trace Metals in Jiulong River Estuary and Xiamen Bay].

Trace metals play an important role in some biogeochemical processes in the marine system. The physical and hydrological conditions in estuaries and coastal seawater are complicated and significantly affected by human activities. Therefore, the biogeochemical behavior and influencing mechanism of trace metals in nearshore water have become a research hotspot.

[Sediment-water flux and processes of nutrients and gaseous nitrogen release in a China River Reservoir].

The key processes and fluxes of nutrients (N and P) and gaseous N (N2 and N2O) across the sediment-water interface in a river reservoir (Xipi) of the Jiulong River watershed in southeast China were studied. Intact core sediment incubation of nutrients exchange, in-situ observation and lab incubation of excess dissolved N2 and N2O (products of nitrification, denitrification and Anammox), and determination of physiochemical and microbe parameters were carried out in 2013 for three representative sites along the lacustrine zone of the reservoir. Results showed that ammonium and phosphate were generally released from sediment to overlying water [with averaged fluxes of N (479.

[Characteristics of sediment phosphorus in the Jiulong River-Reservoir system and its ecological significance].

Sediment phosphorus (P) content and component ratio from 16 sites along the North Jiulong River-reservoir system were analyzed using the Standard Measurement and Test (SMT) procedure. The spatial pattern and characteristics of sediment P and its ecological significance in the Jiulong River-reservoir system were examined in combination with water measurement and watershed information. Total P content in sediments ranged from 387 to 2092 mg x kg(-1) with an average of 1032 mg x kg(-1).

[Preliminary results concerning summer-time denitrification in the Jiulong River Estuary].

Denitrification is an important process mitigating nitrogen (N) pollution in aquatic systems. Water samples in 13 sites throughout the Jiulong River Estuary were collected in July, 2010 in a preliminary investigation of the denitrification rate in this area. As end-products of denitrification, dissolved N2 was measured by determining N2 : Ar ratios using MIMS (HPR-40), while the concentration of nitrous oxide (N2O) dissolved in water was determined by Purge and Trap-Gas Chromatography.

[Wet deposition of atmospheric nitrogen in Jiulong River Watershed].

Spatio-temporal distributions and sources of atmospheric nitrogen (N) in precipitation were examined for Jiulong River Watershed (JRW), an agricultural-dominated watershed located in southeastern China with a drainage area of 1.47 x 10(4) km2. During 2004-2005, 847 rain samples were collected in seventeen sites and analyzed for ammonium N, nitrate N and dissolved total N (DTN) followed by filtration through 0.