Phosphorus retention and release by sediments in the eutrophic Mai Po Marshes, Hong Kong

• Published in: Marine pollution bulletin Vol. 57; no. 6; pp. 349 - 356
• Main Authors: Lai, Derrick Yuk Fo, Lam, Kin Che
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 2008; Elsevier
• Subjects: Adsorption; Aerobiosis; Anaerobiosis; Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Ecotoxicology, biological effects of pollution; Eutrophication; Fractionation; Freshwater; Fundamental and applied biological sciences. Psychology; Geologic Sediments - chemistry; Hong Kong; Mai Po; Marine; Marine and brackish environment; Phosphorus; Phosphorus - analysis; Phosphorus - metabolism; Sea water ecosystems; Seawater - chemistry; Sediment; Synecology; Time Factors; Water quality; Wetlands; Hong Kong; Asia; China; ISEW, China, People's Rep., Hong Kong, New Terr., Deep Bay; China, People's Rep., Hong Kong; Phosphorus; Fractionation; Sediment; Adsorption; Mai Po; Water quality; Pollutant behavior; Trophic status; Retention; Sediments; Eutrophication; Marine environment; Aquatic environment; Surface water; Marsh; Water pollution; Environmental monitoring; Speciation; Environment quality
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2008.01.038

This study examined the phosphorus retention and release characteristics of sediments in the eutrophic Mai Po Marshes in Hong Kong. Results of chemical fractionation show that the sum of inorganic P pools exceeded 50% of the total sediment P content, with the redox-sensitive iron-bound P (Fe(OOH) ≈ P) being the dominant P fraction. Given the considerable average Fe(OOH) ≈ P concentration of 912 μg g −1, Mai Po sediments demonstrated a great potential to release bioavailable P under low sediment redox potentials. This was further supported by the high mean anaerobic P flux of 31.8 mg m −2 d −1 recorded in Mai Po sediment cores, indicating the role of bottom sediments as a net P source. Although sediments in Mai Po had appreciable Langmuir adsorption maxima (1642–3582 mg kg −1), the high zero equilibrium P concentrations (0.02–0.51 mg L −1) obtained suggest that sediment sorption processes would contribute to sustaining the eutrophic conditions in overlying water column even with a further reduction in external P load. Concerted efforts should be made to reduce internal loading of P, especially under reducing conditions, to complement the implementation of zero discharge policy for Deep Bay for effective eutrophication abatement and long-term water quality improvement in the Mai Po Marshes.