This dissertation, "Estimation of Submarine Groundwater Discharge Into Tolo Harbour" by Kiu-chung, Tse, 謝喬中, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled ESTIMATION OF SUBMARINE GROUNDWATER DISCHARGE INTO TOLO HARBOUR Submitted by KIU CHUNG TSE for the degree of Master of Philosophy at The University of Hong Kong in August 2006 The ecological impact of algal blooms in Tolo Harbour has received much attention. Nutrients such as N, P and Si are consented to be the limiting factors for algal blooms. This study aims to quantify the submarine groundwater discharge (SGD) flux discharging to Tolo Harbour and ultimately, to assess the ecological consequence of nutrient input through this underground route. SGD is assessed by radium isotopes and radon in this study. In 2005, seawater samples were collected for radium isotopic analysis in March and October, while a site in Plover Cove was selected for radon analysis in July 222 during the neap tide and spring tide periods. Temporal distributions of Rn 224 and Ra show an inverse relationship with the tidal height, which are 224 believed to reflect the tidal effects on SGD. Spatial distribution of Ra shows a prominent decreasing trend with distance offshore except for a site in Sha Tin Hoi, where SGD as the form of submarine groundwater spring is 224 suspected to exist at the bifurcation of two faults. Enrichment of Ra nearshore was speculated to be attributed to rivers and SGD. Based on the 224 Ra data, the residence time of radium in Tolo Harbour was estimated to be 46 days. Direct measurement by seepage meter in Plover Cove gives an average value of 0.08 m/day, which is very consistent with the SGD flux estimated by 222 Rn with SGD fluid represented by groundwater sample from Chim Uk private well (0.06 m/day). For a seepage area of 200 m x 3000 m in Plover 4 3 Cove, the volumetric SGD would be 3.6-4.8 x 10 m /day. In the Ra isotopes 4 3 approach, the volumetric SGD were estimated to be 6.87 x 10 m /day for 5 3 March and 1.53 x 10 m /day for October. Approximate estimate from water balance calculation places the value of terrestrial groundwater discharge to be 4 3 3.56 x 10 m /day. Nutrients in groundwater around Tolo Harbour were measured. Estimates of nutrient loading through the pathway of SGD ranged from 0 to 29.1 kg/day for nitrite, 32 to 2326 kg/day for nitrate and 0 to 71.9 kg/day for phosphate. 226 228 Limitations of this study mainly come from Ra and Ra data in which standards were not available for calibration. In radon analysis, there are two 222 abnormal Rn values which remain unexplainable. Also, the technique to install the seepage meter is still subject to improve. On the other hand, groundwater data are too sparse to represent the SGD fluid reasonably. Despite of the limitations, nutrient loading on Tolo Harbour through the pathway of SGD is doubtless significant. Unfortunately groundwater quality has been overlooked by the government in the management of red tides in Hong Kong. Based on the result from this study, the current practice for the management of red tides in Hong Kong has to be reviewed and the control measures of groundwater contamination are obviously required. DOI: 10.5353/th_b3823092 Subjects: Groundwater disposal in rivers, lakes, etc - China - Hong Kong Groundwater ecology - China - Hong Kong Groundwater disposal in rivers, lakes, etc - Tolo Harbour Groundwater ecology - Tolo Harbour