Monitoring of Marine Water
The EPD's marine monitoring programme is designed
to assess the water quality of Hong Kong's marine waters. It does
this by testing samples taken from different locations for over
20 parameters, and assessing the extent to which these samples comply
with the key parameters of the WQOs (i.e. those that can be clearly
measured). These key parameters include:
[Photo of Taking water sampling
using an electronic crane]
- Of the physical and chemical aggregate properties:
dissolved oxygen (bottom and depth-averaged);
- Of the nutrients and inorganic constituents:
total inorganic nitrogen and unionised ammonia;
- Of the biological and microbiological features:
chlorophyll-a (for the Tolo Harbour and Channel WCZ only),
and E. coli (for all subzones of WCZs that are classified
as being for 'secondary contact recreation' or 'fish culture').
The EPD's marine monitoring programme was developed
in the 1980s and has since been further refined and augmented. The
EPD was first founded in 1986, when one of its tasks was to take
over the monitoring activities being run by different Government
departments, including the Marine Department and the (former) Agriculture
and Fisheries Department. The newly-established EPD consolidated
the various programmes into a single comprehensive monitoring programme,
which now includes monitoring of marine water, sediment and phytoplankton.
The programme is currently run by the Monitoring Section of the
EPD's Waste and Water Science Group, and is used to indicate the
health of Hong Kong's bodies of water, reveal long-term changes,
assess the effectiveness of pollution control measures, and plan
further water policies and strategies.
Monitoring of Marine Sediment
[Photo of Measuring electrochemical
potential of marine sediment collected by a grab sampler]
In addition to water testing, the quality of
the marine environment can be assessed by the monitoring and testing
of sediment. Sediment is the ultimate resting place of all pollutants
in the sea. Marine pollutants occurring at levels that are too low
to measure in water can be identified in sediment. Such toxic contaminants
not only affect a variety of organisms living within or on the surface
of the sediment, they can also build up in the food chain, for example
in fish or shellfish, and be harmful to humans or animals.
The EPD tests sediment in different parts of
Hong Kong for over 60 physical, chemical and biological parameters.
Using detailed Government guidelines ('Environment, Transport and
Work Bureau Technical Circular ETWB(W) No. 34/2002 - Management
of Dredged / Excavated Sediment'), the EPD compares any contaminants
in sediment against a 'Lower Chemical Exceedance Level' and an 'Upper
Chemical Exceedance Level'. Based on these two levels, sediment
is categorised into three types ranging from 'not contaminated',
through 'slightly contaminated', to 'heavily contaminated'. This
categorisation is important when it comes to activities like sediment
dredging or removal, because it affects how those involved in such
activities must handle and dispose of the sediment. Sediments are
sampled twice a year, and data is usually based on mean five-year
values.
Monitoring of Phytoplankton
[Photo of Phytoplankton analysis
using an inverted microscope]
Phytoplankton monitoring is designed to track
changes in phytoplankton populations at certain key locations. Phytoplankton
is the first biological component to respond to nutrient enrichment
of marine water, so monitoring them provides the EPD with essential
information for addressing the problem of nutrient enrichment. The
EPD's monitoring of phytoplankton has been a longstanding part of
its marine monitoring programme since the 1980s. Its scope was reviewed
and expanded in 1993 and 1994 to become more systematic and comprehensive.
It has been particularly important in providing data that has helped
respond to and control the adverse effects of excessive algal bloom
and red tides on Hong Kong's marine ecosystem.