Project's information

Project's title Study on increase in turbidity and sedimentation in the bottom of Ha Long Bay for contributing to protect and develop the values of the World Natural Heritage. Project's code: VAST06.03/14-15.
Project leader’s name Dr. Dang Hoai Nhon
Project duration 01/01/2014 - 01/01/2015
Project’s budget 600 000 000 VND
Classify Fair
Goal and objectives of the project

1. The rating the source, the status and forecast process turbidity, sedimentation rates in the Ha Long Bay by the radio isotope methods and sediment transport models.
2. Propose solutions to prevent and limitations increase turbidity, sedimentation rates in the Bay contribute to the protection and promotion of the values of the World Natural Heritage.

Main results

- Theoretical results
Increasing turbidity and sedimentation rates in the Ha Long Bay are going on under nature procceses and human activity. The nature procceses are supplied by rivers discharge the Ha Long Bay, human activities are supplied by waste sources from mining extraction, living, urbanization, and other activities.  
Increasing turbidity in rainy season is higher than dry season, in the rainy season turbidity of surface layer is higher than bottom layer, in the dry season turbidity of bottom layer is higher than surface layer, higher turbidity is in the west of the Ha Long Bay. The value average of turbidity in rainy season at surface layer is 17.39±20.00 mg/l and bottom layer 14.72±18.28 mg/l, the value average of turbidity in dry season at surface layer is 7.44±7.38 mg/l and bottom layer is 23.73±36.82 mg/l. Total solid suspened (TSS) in rainy season at surface layer is 14.59±18.20 mg/l and bottom layer is 40.92±76.29 mg/l, in the dry season TSS at surface layers is 20.3±64.8 mg/l and bottom 27.75 ± 57.12 mg/l. According to the forecast scenario for 2025 is that there is increased turbidity but mainly near the coast and near the estuary, but they are lower than Vietnamese Standand for aquaculture purposes.        
The process of sedimentation in basins is going on, sedimentation rate in Ha Long Bay range from 0.02 to 1.56 cm/year. The highest sedimentation rate in the northern Ha Long Bay, next to the central and western of Bay, these places near the sediment supply of Bach Dang estuary, waste area of Ha Tu Coal Mine. The other places sedimentation rate is low, they are distributed in the east and south of Ha Long Bay. The scenarios forecast on sedimentation rates show sedimentation rate fast for shallow in basin continues increasing to 2100 with conditions none and script tectonic uplift; the scenario with rise eustatic sea level and tectonic uplift show that some places in near shore are continue sedimentation rate but low, the other places in the east, south of Bay are deeper cause of sedimetation rate is lower than rise eustatic sea level; the scenario sea level rise by climate changes note by Ministry of Natural Resources and Environment published in 2012 with low level, almost places in the Bay are deeper because sedimentation rates lower than sea level rise.        
 Sources of organic matter in the sediments is determined through δ13C, δ15N and the ratio C/N shows that the role supply of terrigenous and marine materials are present and past with three groups. Group first is marine source but strong affect by terrigenous matterial by rivers with features δ13C=-17.47±7.11‰, δ15N=4.26±0.91‰, C/N = 15.53 ± 5,48. Group second is marine soure then weathered during degradation marine process, or marine origin but the strong affected by terigenous procceses, they are distributed in the deep layers of the Bay with the δ13C=-16.49±4.42‰, δ15N=2.28±0.72 ‰, C/N=7.54±2.89. Group third is marine soure less influenced by continental water mass but more affected by higher vegetation continent characterized by δ13C=-17.17± 5.25 ‰, δ15N=4.33±0.27 ‰ and C/N=26.33±9.95.

Under the impact of human activities, sedimentary environment has showed that increasing of concentration of pollutants over time are heavy metals, increase the concentration of heavy metals in sediment cores, increase concentration of heavy metals in surface sediments from offshore to onshore, they are potential risk to coastal ecosystems. These heavy metals exceeded Canadian Standards TELs are Cu, Pb, As..
The signs of the natural and human impact on the sedimentary environment of Ha Long Bay will reduce landscape, environmental quality makes sustainable development in the area affected. The solution for prevent increase turbidity and sedimentation in the Ha Long Bay are needed to be concerned, these are solutions construction and non-construction. The construction solutions build waste treatments for living waste, urban waste, industrial waste..., these works need to apply advanced technologies treatment the maximum of pollutants before discharged. The solution non-construction necessary build: manage industrial development and mining; manage port operations and navigation, manage fishing, aquaculture and product processing; manage tourism and services activities; manage sea reclamation construction, financial investment to ensure long-term sustainability of the development process.
Applied results
By using tracer and stable isotopes in sediment help us estimate sedimentation rates and identify sources organic matter on sediment in the Ha Long Bay for tracking nature and human activities over time.
Increase turbidity, distribution of turbidity, predict increasing turbidity in Ha Long Bay in future by DELF 3D model. The sedimentation rates in 150 year calculated by 210Pb is base for predict shallow and deep processes in Ha Long Bay by other scenario.
Environmental change before human activities are tracking by heavy metals in sediment are showed that increasing in recently  in some places near shore, some metals over TELs level in Canadian Standard.

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Novelty and actuality and scientific meaningfulness of the results

Estimate sedimentation rates in Ha Long Bay in 150 years range from 0.02-1.56 cm/year, high turbidity in surface layer distribute in west of Ha Long Bay, identify organic sources in sediment are supplied by marine and terrigenous. By using DELF 3D model and scenarios predict increase turbidity, increase sedimentation rate in future.