Nutrient release and sediment oxygen demand in a eutrophic land-locked embayment in Hong Kong

W. F. Hu, Wai Hung Lo, H. Chua, S. N. Sin, P. H.F. Yu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

106 Citations (Scopus)


Tolo Harbour is a large eutrophic land-locked estuarine embayment in Hong Kong. The rapid urbanization, commercio-industrial activities and lack of legislative control around the Tolo catchment produced large quantities of untreated or partially treated municipal sewage, agricultural wastes and cottage industrial effluents which were discharged into Tolo Harbour via rivers and watercourses. Control measures were implemented to reduce the external nutrient loading into the harbour since the early 1980s. Nutrient data for the period 1982 to 1997 were analyzed for temporal trends. Over the period of observation, the total inorganic nitrogen and total phosphorus both show an increasing trend, despite a decade of efforts in reducing nutrient loading. The release rates of potentially mobile nitrogen (N) and phosphorus (P) from the sediments collected from Tolo Harbour were determined by N and P release experiments under oxic conditions. The experimental results showed that the sediment released significant amount of nutrients, especially orthophosphates and ammonia nitrogen. The maximum release rates were 15.0 and 206.0 mg/m2/day, respectively. Although the external nutrient loading has been reduced, nutrients could gradually be released back into the water column from the contaminated sediments and delay improvement of the water quality.
Original languageEnglish
Pages (from-to)369-375
Number of pages7
JournalEnvironment international
Issue number5-6
Publication statusPublished - 1 Jan 2001


  • Estuarine pollution
  • Eutrophication
  • Hong Kong
  • Nitrogen pollution
  • Nutrient release
  • Nutrients
  • Phosphorus pollution
  • Sediment
  • Sediment oxygen demand

ASJC Scopus subject areas

  • Environmental Science(all)


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