ENG-1993 — Page 462

THE ENVIRONMENT

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Another field of investigation is the impact of toxic chemicals in the environment. This leads to an assessment of the safety of specific materials for use in the local environment and to the refinement of effluent standards.

The department operates an air quality monitoring network consisting of 11 stations. The stations are equipped with continuous ambient monitoring instruments for measuring sulphur dioxide, nitrogen oxides, respirable and total suspended particulates (dusts), photochemical oxidants, carbon monoxide and lead.

The results of measurements at the Kwai Chung, Central and Western, and Mong Kok monitoring stations are reported and published each month. These stations broadly represent air quality in districts close to industrial areas, in combined commercial- residential districts, and near road traffic in built-up urban areas.

The department also operates a mobile air quality laboratory. In 1993, it was deployed to measure air quality in various semi-confined transport interchanges. Preliminary findings showed that the air quality at some of these locations was quite unacceptable.

In view of concerns about high nitrogen dioxide levels adjacent to roads, a territory- wide survey of nitrogen oxide concentrations was carried out to supplement measurements made at the fixed air quality monitoring stations. About 60 passive diffusion tube samplers were used to record nitrogen oxide levels. The results confirmed the previous findings that nitrogen oxide levels are generally high throughout Hong Kong's busy road network.

The department conducts surveys on municipal solid waste twice a year to collect up-to-date information for planning future waste disposal facilities. Compared to 1992 findings, total municipal solid waste quantities disposed of at the landfills and incinerators increased by 15 per cent to 9 100 tonnes per day. The increase was due to a nine per cent increase in the amount of domestic waste, and a 28 per cent and 30 per cent increase in the amount of industrial and commercial waste, respectively, delivered to the landfills and incinerators. Construction waste delivered to the landfills, however, decreased by nine per cent.

Local waste recovery activities continued to play an important role in waste management, resulting in the export of substantial quantities of recovered waste materials for recycling overseas. A total of 1.3 million tonnes of waste materials, including waste paper, metals and plastic, were exported in 1993, generating export earnings of $2.2 billion. About 500 000 tonnes of waste paper, used lubricating oil, metals, plastic scrap and glass were reprocessed locally.

The government encourages waste avoidance, which embraces waste minimisation, recovery and recycling, recognising that it is a useful means to bring about a reduction in quantities of waste requiring disposal. A Waste Reduction Study is being carried out to develop a strategic plan for waste avoidance in the territory. The plan would include various practical measures to facilitate waste prevention, minimisation, re-use, recovery through sorting, separation and recycling in the territory. The application of advanced technologies to reduce the bulk of municipal waste requiring disposal will also be examined.

A study conducted by the department in March found that a large proportion of construction waste could be used to create land after sorting and removal of undesirable materials, comprising mainly non-inert materials such as wood, paper, plastic, bamboo and general refuse. The survey ascertained that the sorting of construction waste at source is practical and achievable.