THE ENVIRONMENT
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profitably re-used locally. The scope of such work is wide and is still in its infancy, but hopefully in time the wastes which are now thought of as nuisances will become assets.
Various pilot schemes are run by the department to determine suitable methods to treat and dispose of farm wastes. Pig and poultry manure still form the major sources of organic pollution in most of the streams in the New Territories, where the manure is often dumped by farmers. On-farm storage bunkers have been developed for pig manure in which the manure dewaters and becomes less noxious. The disposal of such manure is then easier than when it is in its raw state. The poultry manure drier at Pat Heung operated regularly throughout the year, turning manure into fertiliser. In addition, the Agricultural Development Foundation has sponsored the use of a batch type manure drier which seems well suited locally for use on pig manure. It will be located in Sai Kung.
Professor P. C. G. Isaac, the World Health Organisation consultant advising the government on the control of pollution from agricultural wastes, made his third visit to Hong Kong in March. He ran a course organised by the Environment Branch on the control of pollution from agricultural wastes. The course was attended by civil servants working directly with the rural community whose work is affected either directly or indirectly by such pollution problems.
Marine Pollution
In 1976 the marine pollution unit of the Agriculture and Fisheries Department completed its one-year study of Tolo Harbour, undertaken in collaboration with the marine science laboratory of the Chinese University of Hong Kong. The new town of Sha Tin and the old township of Tai Po, which is being developed, are both adjacent to the harbour. The results of the study indicate that the harbour is ecologically complex, and continued and more intensive research will be necessary if ecological problems, arising from increased sewage discharge, are to be avoided. An additional research officer has been appointed for this purpose.
An 18-month survey of the phytoplankton communities of Hong Kong coastal waters was also completed, in collaboration with the Public Works Department. From the results a 'safe level' of chlorophyll in sea water has been determined. This is often exceeded in areas around Hong Kong Island and further to the west, and more intensive research is being initiated into the dynamics of naturally occurring and pollution induced plankton blooms.
Benthic (sea-bottom) survey work is being carried out in collaboration with the University of Hong Kong, which has assigned a full-time research student to this project. A network of regular sampling stations has been established and additional surveys are made whenever possible. On rocky bottoms, progress has been made in co-operation with amateur divers and a survey of typical communities is being undertaken.
A preliminary survey of toxic metal loads in inshore fish and shellfish was carried out during the year and, while the results indicated that there appears to be no immediate risk to consumers' health, potential problems exist and are expected to