|
Toxic Substances Monitoring in Hong Kong
The Environmental Protection Department (EPD) initiated a toxic substances monitoring programme in 2004. The purpose is to monitor and assess the extent of toxic substances pollution in the Hong Kong marine environment, including marine water, sediment, biota and potential land-based pollution sources, such as river, sewage effluent and storm runoff. This webpage summarises the findings of the first 3 years of monitoring conducted between 2004 and 2006. It provides information on the type of toxic substances measured and their levels in the marine environment and pollution sources.
1. Why do we need to monitor toxic substances in the marine environment?
The Hong Kong Environmental Protection Department (EPD) has been monitoring marine water quality in Hong Kong since 1986. The monitoring programme covers 94 stations and measures over 40 water quality parameters, including organic matter, nutrients and inorganic pollutants. In addition to these, there are thousands of toxic chemicals known to persist in the environment and cause harm to the ecosystem and human health. They come from a variety of potential pollution sources such as domestic sewage, industrial discharges, river and storm runoff. To assess the extent of pollution of toxic chemicals in the marine environment, the EPD conducted a study on toxic substances pollution in Hong Kong during 1999-2003 (the Toxic Substances Study). The study, based on extensive literature review, field measurement and toxicological testing, concluded that while the Hong Kong marine environment was not widely contaminated with chemicals at levels of concern, a number of potentially problematic pollutants existed and warranted close monitoring. Based on the findings of the study, a comprehensive toxic substances monitoring programme was set up in 2004, focusing on marine water, sediment, biota and potential pollution sources.
2. What toxic substances are monitored?
Twenty-four chemicals of potential concern to the local environment and priority toxic substances controlled internationally are included in the monitoring programme. These include persistent organic pollutants (POPs), i.e. dioxins/furans; polychlorinated biphenyls (PCBs); pesticides, i.e. dichlorodiphenyltrichloroethane (DDT), Hexachlorocyclohexanes (HCHs); antifoulant, i.e. tributyltin (TBT); organic pollutants, i.e. polyaromatic hydrocarbons (PAHs) , phenol, nonylphenol, nonylphenol ethoxylates, polybrominated diphenyl ethers (PBDEs), methyl mercury; non-metallic inorganic, i.e. fluoride and 11 metals, i.e. As, Ba, Be, Cd, Cu, Hg, Se, Ag, Tl, Sn and Zn.
3. How do we monitor toxic substances and where do we collect samples?
The toxic substances monitoring programme runs on three-year cycles, with the first two years (2004-2005) focusing on the marine environment, i.e. water, sediment, biota and the third year (2006) on pollution sources. Marine water and sediment samples were collected from 10 locations throughout the territory and biota samples were collected from 6 locations. The pollution sources monitored included raw sewage (7 sites), storm run-off (5 sites), industrial and landfill discharges (2 sites), river flow (3 sites) and sewage treatment works effluent (3 sites). See map below for sampling locations.
[A map showing sampling locations in the Toxic Substances Monitoring Programme, 2004-2006]
| [Collecting marine water samples] |
[Collecting marine sediment samples] |
|
Collecting marine water samples
|
Collecting marine sediment samples
|
| [Sorting marine biota samples] |
[Collecting samples at pollution source] |
|
Sorting marine biota samples
|
Collecting samples at pollution source
|
4. What are the levels of toxic substances in the marine environment?
The results from 2004-2006 monitoring show that the levels of toxic substances in the Hong Kong marine environment were generally low compared with other parts of the Pearl River Estuary, and stayed largely within the range reported for the coastal waters of the Mainland and other countries. Higher concentrations of toxic substances, in particular heavy metals were found in marine sediments at some “hot spots” associated with historical pollution. The levels of toxic substances in marine water, sediment and biota generally met local and international standards for protection of marine life and human health. Summary statistics of the levels of toxic substances in marine water, sediments and biota are found in Tables 1-3.
Table 1 Levels of toxic substances in marine water in Hong Kong, 2004-2006
Table 2 Levels of toxic substances in marine sediments in Hong Kong, 2004-2006
Table 3 Levels of toxic substances in marine biota in Hong Kong, 2004-2006
5. What are the levels of toxic substances in potential pollution sources?
In general, the levels of most toxic substances in potential pollution sources, i.e. raw sewage, sewage effluent, storm runoff and river water were low and comparable with the levels in the marine water. A few chemicals, such as phenol, nonylphenol and nonylphenol ethoxylates were significantly higher in sewage effluent and stormwater runoff than in marine water. Sewage and stormwater were likely to be major sources of these chemicals in the marine environment. Summary statistics of the levels of toxic substances in various potential pollution sources are found in Table 4.
Table 4 Levels of toxic substances in potential pollution sources in Hong Kong, 2004-2006
Individual toxic substances and their levels in the arine environment and potential pollution sources are given below.
Persistent Organic Pollutants
Pesticides
Antifoulant
Organic pollutants
Non-metallic
Metals
6. What is the next step in toxic substances monitoring?
The results from the toxic substances monitoring conducted in 2004-2006 serve as a baseline for establishing and refining the methodology of the long-term monitoring programme. The next step is to implement the second phase of monitoring programme which started in 2007 and other eight POPs chemicals, i.e. Aldrin, Chlordane, Dieldrin, Endrin, Heptachlor, Hexachlorobenzene, Mirex and Toxaphene were also included in the monitoring.
|