2               Air Quality

Monitoring Requirement


2.1               According to the EM&A Documents for HKLR listed in Table 1.1, baseline air quality monitoring shall be carried out for a period of fourteen days, in terms of 1-hour and 24-hour Total Suspended Particulates (TSP) at all the monitoring locations. Monitoring of 1-hour TSP shall be carried out at least three times per day while that of 24-hour TSP shall be conducted daily for 14 consecutive days.

Monitoring Locations


2.2               Baseline air quality monitoring was conducted at the two monitoring stations under the Contract, as shown in Figure 2.  Table 2.1 describes the locations of the air quality monitoring stations.


Table 2.1        Location for Air Quality Monitoring Locations

Monitoring Stations



Sha Lo Wan


San Tau

Monitoring Equipment


2.3               High Volume Samplers (HVS) were used to carry out 24-hour TSP monitoring. Direct reading dust meter were also used to measure 1-hour average TSP levels. The 1-hour sampling was determined periodically by HVS to check the validity and accuracy of the results measured by direct reading method.


2.4               Wind data monitoring equipment was set at Rooftop of Village Office at San Tau for logging wind speed and wind direction such that the wind sensors are clear of obstructions or turbulence caused by building. The wind data monitoring equipment is re-calibrated at least once every six months and the wind directions are divided into 16 sectors of 22.5 degrees each. The location is shown in Figure 2.


2.5               The equipment used in the baseline air quality monitoring programme and copies of the calibration certificates for the equipment can be referred to  the Baseline Environmental Monitoring Report for HKBCF.


Monitoring Parameters, Frequency and Duration


2.6               Table 2.2 summarizes the monitoring parameters, monitoring period and frequencies of baseline air quality monitoring.


Table 2.2        Frequency and Parameters of Air Quality Monitoring

Monitoring Station

Location for Measurement





Area in front of No. 9

Sha Lo Wan

1-hour TSP

24-hour TSP


24 hours

3 times/day



San Tau

(Rooftop of Village Office)


Monitoring Methodology and Quality Assurance / Quality Control (QA/QC) Procedure

2.7               Weather data was recorded during the baseline period can be referred to the Baseline Environmental Monitoring Report for HKBCF.  The air temperature, precipitation and the relative humidity data was obtained from Hong Kong Observatory where the wind speed and wind direction were recorded by the installed Wind Anemometer. The general weather conditions (i.e. sunny, cloudy or rainy) were recorded by the field staff’s observation on the monitoring days.

24 hour TSP and RSP Air Quality Monitoring


2.8               High volume Samplers (HVS) completed with appropriate sampling inlets were employed for air quality monitoring.  Each sampler was composed of a motor, a filter holder, a flow controller and a sampling inlet and its performance specification complies with that required by USEPA Standard Title 40, Code of Federation Regulations Chapter 1 (Part 50).

HVS Installation

2.9               The following guidelines were adopted during the installation of HVS:


·            Sufficient support was provided to secure the samplers against gusty wind.

·            No two samplers were placed less than 2 meters apart.

·            The distance between the sampler and an obstacle, such as buildings, was at least twice the height that the obstacle protrudes above the sampler.

·            A minimum of 2 meters of separation from walls, parapets and penthouses was required for rooftop samples.

·            A minimum of 2 meters separation from any supporting structure, measured horizontally was required.

·            No furnaces or incineration flues were nearby.

·            Airflow around the sampler was unrestricted.

·            The samplers were more than 20 meters from the drip line.

·            Any wire fence and gate, to protect the sampler, should not cause any obstruction during monitoring.

Filters Preparation

2.10           Fiberglass filters were used [Note: these filters have a collection efficiency of larger than 99% for particles of 0.3μm diameter].  A HOKLAS accredited laboratory, Wellab Ltd., was responsible for the preparation of 24-hr conditioned and pre-weighed filter papers for Cinotech’s monitoring team. 


2.11           All filters, which were prepared by Wellab Ltd., were equilibrated in the conditioning environment for 24 hours before weighing.  The conditioning environment temperature was around 25 °C and not variable by more than ±3 °C; the relative humidity (RH) was < 50% and not variable by more than ±5%.  A convenient working RH was 40%.


2.12           Wellab Ltd. has a comprehensive quality assurance and quality control programmes.


Operating/Analytical Procedures

2.13           Operating/analytical procedures for the air quality monitoring were highlighted as follows:


·            Prior to the commencement of the dust sampling, the flow rate of the HVS was properly set (between 1.1 m3/min. and 1.4 m3/min.) in accordance with the manufacturer's instruction to within the range recommended in USEPA Standard Title 40, CFR Part 50.

·            The power supply was checked to ensure the sampler worked properly.

·            On sampling, the sampler was operated for 5 minutes to establish thermal equilibrium before placing any filter media at the designated air quality monitoring station.

·            The filter holding frame was then removed by loosening the four nuts and carefully a weighted and conditioned filter was centered with the stamped number upwards, on a supporting screen.

·            The filter was aligned on the screen so that the gasket formed an airtight seal on the outer edges of the filter.  Then the filter holding frame was tightened to the filter holder with swing bolts.  The applied pressure should be sufficient to avoid air leakage at the edges.

·            The shelter lid was closed and secured with the aluminum strip.

·            The timer was then programmed.  Information was recorded on the record sheet, which included the starting time, the weather condition and the filter number (the initial weight of the filter paper can be found out by using the filter number).

·            After sampling, the filter was removed and sent to the Wellab Ltd. for weighing.  The elapsed time was also recorded.

·            Before weighing, all filters were equilibrated in a conditioning environment for 24 hours. The conditioning environment temperature should be between 25°C and 30°C and not vary by more than ±3°C; the relative humidity (RH) should be < 50% and not vary by more than ±5%.  A convenient working RH is 40%.  Weighing results were returned to Cinotech for further analysis of TSP concentrations collected by each filter.



2.14           The following maintenance/calibration was required for the HVS:


·            The high volume motors and their accessories were properly maintained. Appropriate maintenance such as routine motor brushes replacement and electrical wiring checking were made to ensure that the equipment and necessary power supply are in good working condition.

·            All HVS were calibrated (five point calibration) using Calibration Kit prior to the commencement of the baseline monitoring and thereafter at bi-monthly intervals.

1 hour TSP Air Quality Monitoring

Measuring Procedures

2.15           The measuring procedures of the 1-hour dust meter are in accordance with the Manufacturer’s Instruction Manual as follows:


·            The 1-hour dust meter is placed at least 1.3 meters above ground.

·            Set POWER to “ON” and make sure that the battery level was not flash or in low level.

·            Allow the instrument to stand for about 3 minutes and then the cap of the air sampling inlet has been released.

·            Push the knob at MEASURE position.

·            Set time/mode setting to [BG] by pushing the time setting switch.  Then, start the background measurement by pushing the start/stop switch once.  It will take 6 sec. to complete the background measurement.

·            Push the time setting switch to change the time setting display to [MANUAL] at the bottom left of the liquid crystal display.  Finally, push the start/stop switch to stop the measuring after 1 hour sampling.

·            Information such as sampling date, time, count value and site condition were recorded during the monitoring period.


2.16           The following maintenance/calibration is required for the 1-hour dust meter;


·            Check and calibrate the meter by HVS to check the validity and accuracy of the results measured by direct reading method at 2-month intervals throughout all stages of the air quality monitoring.


Results and Observations


2.17           Baseline air quality monitoring was conducted at two monitoring stations, namely AMS1 - Sha Lo Wan and AMS4 - San Tau in the period between 18th October 2011 and 31st October 2011. The detailed monitoring schedule is shown in Appendix A.


2.18           The monitoring data are summarized in Tables 2.3 and 2.4.  All monitoring data and graphical presentations of 1-hour and 24-hour TSP can be referred to Appendix G and the Baseline Environmental Monitoring Report for HKBCF respectively. Detailed weather conditions during the baseline monitoring period are shown in Appendix B.

Table 2.3        Summary of Baseline 1-hour TSP Monitoring Results

Monitoring Station

Average TSP Concentration, μg/m3


AMS1 - Sha Lo Wan


(67.6 – 353.5)

AMS4 - San Tau


(55.7 – 264.6)

Table 2.4        Summary of Baseline 24-hour TSP Monitoring Results

Monitoring Station

Average TSP Concentration, μg/m3


AMS1 - Sha Lo Wan


(39.0 – 87.8)

AMS4 - San Tau


(33.5 – 124.0)



2.19           The weather was generally sunny and fine during the baseline monitoring period. 


2.20           During the baseline air quality monitoring period, the influencing factors which may affect the results are summarized in Table 2.5:

Table 2.5        Influencing Factors at Dust Monitoring Stations

Monitoring Station

Influencing Factors


Shallow sand beach nearby



Action and Limit Levels


2.21           The Action and Limit Levels have been set in accordance with the EM&A Documents for HKLR, which are summarized in Table 2.6.

Table 2.6        Guidelines for Establishing Action and Limit Levels for Air Quality


Action Level

Limit Level


1-hour TSP Level in μg/m3


For baseline level ≤ 384μg/m3,

Action level = (Baseline level * 1.3 + Limit level)/2

For baseline level > 384μg/m3,

Action level = Limit level



24-hour TSP Level in μg/m3


For baseline level ≤ 200μg/m3,

Action  level = (Baseline level * 1.3 + Limit level)/2

For baseline level > 200μg/m3,

Action level = Limit level



2.22           Following the above guidelines, the Action and Limit Levels for air quality impact monitoring have been set, as presented in Tables 2.7 and 2.8.

Table 2.7        Action and Limit Levels for 1-hour TSP


Action Level, μg/m3

Limit Level, μg/m3






Table 2.8        Action and Limit Levels for 24-hour TSP


Action Level, μg/m3

Limit Level, μg/m3