Submarine groundwater discharge (SGD) has been considered as a potential contributor to harmful algal bloom, coastal eutrophication, acidification and hypoxia. Natural radon (²²²Rn) is an excellent tracer for studying SGD and other oceanographic processes. In the past decades, radon measurement approaches for aquatic research have been fully developed but still suffer limitations. Here, based on our self-developed PIC radon detector, we not only refined the continuous integrated spatial survey measurement but also developed an automatic submersible radon determination approach to produce in-situ high data throughput at any water depth of interest. We demonstrate radon measurement efficiency of the PIC is 2-fold higher than a traditional RAD7 detector and is far less influenced by moisture. The radon degassing efficiency of the membrane contactor is comparable to the shower-head type air-water exchanger but is independent of operating position. We successfully deployed the submersible system in 3-meter water depth over a 100-hours period in an anthropogenic influenced bay. Based on high temporal resolution observations, the SGD flux was estimated to be 25.4±14.5 cm/d. Groundwater derived DIN and DIP occupied 74% of total DIN and 82% of total DIP input of this regions, respectively. The SGD fluxes pattern plotted together with the tidal variations revealed that tidal pumping may be the main driving force that affects nutrient, carbon and other dissolved matters dynamics in coastal aquifers.

Primary Presenter: Shibin Zhao, Ocean University of China (ouc_zshib@163.com)

Authors:

Shibin Zhao, Ocean University of China  (zhaoshibin@stu.ouc.edu.cn)

Meng Li, Ocean University of China  (limeng@ouc.edu.cn)

Chunqian Li, Ocean University of China  (cqli@qnlm.ac)

Jinjia Guo, Ocean University of China  (opticsc@ouc.edu.cn)

Wen Liu, Ocean University of China  (liuwenouc@163.com)

William Burnett, Florida State University  (wburnett@fsu.edu)

Natasha Dimova, University of Alabama  (ntdimova@ua.edu)

Zhigang Yu, Ocean University of China  (zhigangyu@ouc.edu.cn)

Bochao Xu, Ocean University of China  (xubc@ouc.edu.cn)