File Download
 
 
Supplementary

Postgraduate Thesis: Estimation of submarine groundwater discharge and nutrient loading of Tolo Harbour
  • Basic View
  • Metadata View
  • XML View
TitleEstimation of submarine groundwater discharge and nutrient loading of Tolo Harbour
 
AuthorsLee, Chun-ming
李進銘
 
Issue Date2012
 
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
 
AbstractTolo Harbour is naturally eutrophic with frequent algal blooms in the past. Water quality of the Harbour has been improved in past 20 years but the phytoplankton density is still high compared to other waters in Hong Kong. This study aimed to quantify submarine groundwater discharge (SGD) to Tolo Harbour and to show the important role of SGD in terms of nutrient loading with ecological effect. SGD was determined by one of the natural geochemical tracers, 226Ra. Mass balance of 226Ra was applied to quantify SGD and SGD was estimated to be 8.28 × 106 m3 d-1. A large portion of the SGD was recirculated seawater while the freshwater component of SGD, or submarine fresh groundwater discharge (SFGD), was only a small portion of that. SFGD was estimated to be 2.31 ×105 m3 d-1 using water balance. The flushing time of Tolo Harbour was estimated to be 77.9 d by using SFGD as one of the fresh water input components. Different nutrients including NH3—N, NO2—N, NO3—N, PO43-—P, SiO2—Si and dissolved inorganic nitrogen (DIN) were applied to nutrient mass balance analyses. The mass balance is based on non-point sources which include aerosol deposition (dry deposition), rainfall (wet deposition), diffusion from sediment, river, SGD and tidal exchange. Removal of nutrients was determined once all the non-point sources were estimated. SGD is the major source which contributes more than 88 % for different nutrients. Other sources contribute less than 10 % individually. The total nutrient loads of DIN, PO43-–P and SiO2—Si are 8.33 ×105, 1.03 ×104 and 1.28 ×106 mol d-1 respectively. The removals of DIN, PO43-–P and SiO2—Si are 6.87 ×105, 5.10 × 103 and 1.28 ×106 mol d-1 respectively. Assume the removal of nutrients was only due to consumption of phytoplankton, primary productivity was estimated to be 1.16g C m-2 d-1. Limitations of this study were about the determination of atmospheric depositions and diffusion from sediment. However, the contribution of nutrient loading from these sources was insignificant compared with SGD. Even if SGD is replaced by SFGD for the nutrient loading estimation, it is still the major contributor among all other non-point sources. In spite of the limitations, the important role of SGD in terms of nutrient loading is evident. Groundwater quality should be monitored and controlled as it has significant ecological impact to the Harbour.
 
AdvisorsJiao, JJJ
 
DegreeMaster of Philosophy
 
SubjectGroundwater disposal in rivers, lakes, etc. - China - Hong Kong.
Groundwater ecology - China - Hong Kong.
 
Dept/ProgramEarth Sciences
 
DC FieldValue
dc.contributor.advisorJiao, JJJ
 
dc.contributor.authorLee, Chun-ming
 
dc.contributor.author李進銘
 
dc.date.hkucongregation2012
 
dc.date.issued2012
 
dc.description.abstractTolo Harbour is naturally eutrophic with frequent algal blooms in the past. Water quality of the Harbour has been improved in past 20 years but the phytoplankton density is still high compared to other waters in Hong Kong. This study aimed to quantify submarine groundwater discharge (SGD) to Tolo Harbour and to show the important role of SGD in terms of nutrient loading with ecological effect. SGD was determined by one of the natural geochemical tracers, 226Ra. Mass balance of 226Ra was applied to quantify SGD and SGD was estimated to be 8.28 × 106 m3 d-1. A large portion of the SGD was recirculated seawater while the freshwater component of SGD, or submarine fresh groundwater discharge (SFGD), was only a small portion of that. SFGD was estimated to be 2.31 ×105 m3 d-1 using water balance. The flushing time of Tolo Harbour was estimated to be 77.9 d by using SFGD as one of the fresh water input components. Different nutrients including NH3—N, NO2—N, NO3—N, PO43-—P, SiO2—Si and dissolved inorganic nitrogen (DIN) were applied to nutrient mass balance analyses. The mass balance is based on non-point sources which include aerosol deposition (dry deposition), rainfall (wet deposition), diffusion from sediment, river, SGD and tidal exchange. Removal of nutrients was determined once all the non-point sources were estimated. SGD is the major source which contributes more than 88 % for different nutrients. Other sources contribute less than 10 % individually. The total nutrient loads of DIN, PO43-–P and SiO2—Si are 8.33 ×105, 1.03 ×104 and 1.28 ×106 mol d-1 respectively. The removals of DIN, PO43-–P and SiO2—Si are 6.87 ×105, 5.10 × 103 and 1.28 ×106 mol d-1 respectively. Assume the removal of nutrients was only due to consumption of phytoplankton, primary productivity was estimated to be 1.16g C m-2 d-1. Limitations of this study were about the determination of atmospheric depositions and diffusion from sediment. However, the contribution of nutrient loading from these sources was insignificant compared with SGD. Even if SGD is replaced by SFGD for the nutrient loading estimation, it is still the major contributor among all other non-point sources. In spite of the limitations, the important role of SGD in terms of nutrient loading is evident. Groundwater quality should be monitored and controlled as it has significant ecological impact to the Harbour.
 
dc.description.naturepublished_or_final_version
 
dc.description.thesisdisciplineEarth Sciences
 
dc.description.thesislevelmaster's
 
dc.description.thesisnameMaster of Philosophy
 
dc.identifier.hkulb4833020
 
dc.languageeng
 
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)
 
dc.relation.ispartofHKU Theses Online (HKUTO)
 
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.
 
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License
 
dc.source.urihttp://hub.hku.hk/bib/B48330206
 
dc.subject.lcshGroundwater disposal in rivers, lakes, etc. - China - Hong Kong.
 
dc.subject.lcshGroundwater ecology - China - Hong Kong.
 
dc.titleEstimation of submarine groundwater discharge and nutrient loading of Tolo Harbour
 
dc.typePG_Thesis
 
<?xml encoding="utf-8" version="1.0"?>
<item><contributor.advisor>Jiao, JJJ</contributor.advisor>
<contributor.author>Lee, Chun-ming</contributor.author>
<contributor.author>&#26446;&#36914;&#37528;</contributor.author>
<date.issued>2012</date.issued>
<description.abstract>&#65279;Tolo Harbour is naturally eutrophic with frequent algal blooms in the past. Water quality of the Harbour has been improved in past 20 years but the phytoplankton density is still high compared to other waters in Hong Kong. This study aimed to quantify submarine groundwater discharge (SGD) to Tolo Harbour and to show the important role of SGD in terms of nutrient loading with ecological effect.



SGD was determined by one of the natural geochemical tracers, 226Ra. Mass balance of 226Ra was applied to quantify SGD and SGD was estimated to be 8.28 &#215; 106 m3 d-1. A large portion of the SGD was recirculated seawater while the freshwater component of SGD, or submarine fresh groundwater discharge (SFGD), was only a small portion of that. SFGD was estimated to be 2.31 &#215;&#61472;105 m3 d-1 using water balance. The flushing time of Tolo Harbour was estimated to be 77.9 d by using SFGD as one of the fresh water input components.



Different nutrients including NH3&#8212;N, NO2&#8212;N, NO3&#8212;N, PO43-&#8212;P, SiO2&#8212;Si and dissolved inorganic nitrogen (DIN) were applied to nutrient mass balance analyses. The mass balance is based on non-point sources which include aerosol deposition (dry deposition), rainfall (wet deposition), diffusion from sediment, river, SGD and tidal exchange. Removal of nutrients was determined once all the non-point sources were estimated. SGD is the major source which contributes more than 88 % for different nutrients. Other sources contribute less than 10 % individually. The total nutrient loads of DIN, PO43-&#8211;P and SiO2&#8212;Si are 8.33 &#215;&#61472;105, 1.03 &#215;&#61472;104 and 1.28 &#215;&#61472;106 mol d-1 respectively. The removals of DIN, PO43-&#8211;P and SiO2&#8212;Si are 6.87 &#215;&#61472;105, 5.10 &#215; 103 and 1.28 &#215;&#61472;106 mol d-1 respectively. Assume the removal of nutrients was only due to consumption of phytoplankton, primary productivity was estimated to be 1.16g C m-2 d-1.



Limitations of this study were about the determination of atmospheric depositions and diffusion from sediment. However, the contribution of nutrient loading from these sources was insignificant compared with SGD. Even if SGD is replaced by SFGD for the nutrient loading estimation, it is still the major contributor among all other non-point sources. 



In spite of the limitations, the important role of SGD in terms of nutrient loading is evident. Groundwater quality should be monitored and controlled as it has significant ecological impact to the Harbour.</description.abstract>
<language>eng</language>
<publisher>The University of Hong Kong (Pokfulam, Hong Kong)</publisher>
<relation.ispartof>HKU Theses Online (HKUTO)</relation.ispartof>
<rights>The author retains all proprietary rights, (such as patent rights) and the right to use in future works.</rights>
<rights>Creative Commons: Attribution 3.0 Hong Kong License</rights>
<source.uri>http://hub.hku.hk/bib/B48330206</source.uri>
<subject.lcsh>Groundwater disposal in rivers, lakes, etc. - China - Hong Kong.</subject.lcsh>
<subject.lcsh>Groundwater ecology - China - Hong Kong.</subject.lcsh>
<title>Estimation of submarine groundwater discharge and nutrient loading of Tolo Harbour</title>
<type>PG_Thesis</type>
<identifier.hkul>b4833020</identifier.hkul>
<description.thesisname>Master of Philosophy</description.thesisname>
<description.thesislevel>master&apos;s</description.thesislevel>
<description.thesisdiscipline>Earth Sciences</description.thesisdiscipline>
<description.nature>published_or_final_version</description.nature>
<date.hkucongregation>2012</date.hkucongregation>
<bitstream.url>http://hub.hku.hk/bitstream/10722/173916/1/FullText.pdf</bitstream.url>
</item>