2.1
1-hour
and 24-hour TSP levels at two designated monitoring stations were monitored in
the month in accordance with the EM&A Manual. Appendix C shows the established Action and Limit Levels for the
environmental monitoring works.
2.2
The
monitoring schedule for the month is shown in Appendix D. Air quality monitoring stations for 24-hour and 1-hour TSP
measurements are shown in Figure 2.1.
2.3
Portable
dust meter was used to carry out 1-hour TSP monitoring. High volume sampler
(HVS - Model GMWS-2310 Accu-Vol) completed with the
appropriate sampling inlets was installed for 24-hour TSP sampling. The HVS
meet all the requirements as specified in the updated EM&A Manual. Table
2.1 summarised the equipment that were used in the dust-monitoring programme.
Table 2.1 Air Quality Monitoring Equipment
|
Equipment |
Model |
|
Dust Meter (for 1-hour TSP measurement |
Laser Dust Monitor – Model LD-3 |
|
HVS (for 24-hour TSP measurement) |
GMWS 2310 Accy-Vol system |
|
Calibration Kit (for HVS) |
GMW 25 |
Monitoring Parameters, Frequency and Duration
2.3
Table 2.2 summarised the monitoring parameters, frequency
and duration of impact air quality monitoring.
Table 2.2 Air Quality Monitoring Parameters, Frequency and Duration
|
Parameter |
Duration |
Frequency |
|
1-hour TSP |
1 hour |
3 times every six
days |
|
24-hour TSP |
24 hours |
Once every six days |
2.4
In accordance with the EM&A Manual, two air quality
monitoring stations, as shown in Figure 2.1 were selected for 24-hour and
1-hour TSP sampling. Table 2.3 describes the location of the air quality
monitoring stations.
Table 2.3 Locations of Air Quality Monitoring Stations
|
Monitoring
Station |
Identity /
Description |
|
AM1 |
Correctional
Services Department Married Staff Quarters |
|
AM2 |
|
1-hour TSP Monitoring
Monitoring
Procedure
2.5
The measuring procedures of 1-hour TSP by a portable dust
meter are in accordance with the Manufacturer’s Instruction Manual as follows:
·
Set POWER to “ON”, push
·
Push the knob at MEASURE position.
·
Push “O-ADJ” button. (Then meter’s indication is 0).
·
Push the knob at SENSI ADJ position and set the meter’s
indication to S value described on the Test Report using the trimmer for SENSI
ADJ.
·
Pull out the knob and return it to MEASURE position.
·
Push “START” button.
Maintenance
and Calibration
·
The
1-hour TSP dust meters are verified at 1-year intervals throughout all stages
of the impact air quality monitoring.
·
Calibration
details for the dust meters are provided in Appendix E.
24-hour TSP Monitoring
Installation
2.6
The HVSs were installed in the
vicinity of the air sensitive receivers. The following criteria were considered
in the installation of the HVSs:
·
A horizontal platform with appropriate support to secure
the samplers against gusty wind was provided.
·
The distance between the HVS and any obstacles, such as
buildings, was at least twice the height that the obstacle protrudes above the
HVS.
·
A minimum of 2 meters separation from walls, parapets and
penthouses was provided for rooftop sampler.
·
No furnace or incinerator flues were nearby.
·
Airflow around the sampler was unrestricted.
·
Permission was obtained to set up the sampler and to
obtain access to the monitoring stations.
·
A secure supply of electricity was obtained to operate
the sampler.
Preparation
of Filter papers
·
Glass
fibre filters, G810 were labelled and sufficient filters that were clean and
without pinholes were selected.
·
All
filters 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%.
·
ALS Technichem
(HK) Pty Ltd. is
a HOKLAS accredited laboratory which has comprehensive quality assurance and
quality control programmes.
Monitoring
Procedures
·
The
power supply was checked to ensure the HVSs work
properly.
·
The
filter holder and the area surrounding the filter were cleaned.
·
The
filter holder was removed by loosening the four bolts and a new filter, with
stamped number upward, on a supporting screen was aligned carefully.
·
The
filter was properly aligned on the screen so that the gasket formed an airtight
seal on the outer edges of the filter.
·
The
swing bolts were fastened to hold the filter holder down to the frame. The pressure applied should be
sufficient to avoid air leakage at the edges.
·
Then
the shelter lid was closed and secured with the aluminum
strip.
·
The HVSs were warmed-up for about 5 minutes to establish
run-temperature conditions.
·
A new
flowrate record sheet was set into the flow recorder.
·
The
flow rate of the HVS was checked and adjusted at around 1.1 m3/min. The range was between 0.6-1.7 m3/min.
·
The
programmable timer was set for a sampling period of 24 hrs + 1 hr, and
the starting time, weather condition and the filter number were recorded.
·
The
initial elapsed time was recorded.
·
At
the end of sampling, the sampled filter was removed carefully and folded in
half length so that only surfaces with collected particulate matter were in
contact.
·
It
was then be placed in a clean plastic envelope and sealed.
·
All monitoring information was recorded on a standard
data sheet.
·
Filters were sent to ALS
Technichem (HK) Pty Ltd. for analysis.
Maintenance
and Calibration
·
The HVSs and their accessories were maintained in good working
condition, such as replacing motor brushes routinely and checking electrical
wiring to ensure a continuous power supply.
·
HVSs are calibrated at bi-monthly intervals
using GMW-25 Calibration Kit throughout all stages of the impact air quality
monitoring.
·
Calibration
details for the HVSs are provided in Appendix E.
2.7
Dust monitoring was conducted for both 1-hr TSP and 24-hr
TSP at all designated monitoring stations in the month. Air quality monitoring
results and graphical presentations are provided in Appendix F.
1-hour TSP Monitoring
2.8
All measured 1-hour TSP levels complied with the Action and
Limit Levels in the month. A summary of 1-hour TSP monitoring results is presented
in Table 2.4.
Table 2.4 Summary of Impact 1-hour TSP Monitoring Results
|
Monitoring Station |
1-hour TSP (mg/m3) |
Action Level (mg/m3) |
Limit Level (mg/m3) |
No. of Exceedance
|
|
|
Range |
Action |
Limit |
|||
|
AM1 |
95.8 – 102.7 |
311.2 |
500.0 |
Nil |
Nil |
|
AM2 |
94.9 – 101.6 |
368.6 |
500.0 |
Nil |
Nil |
24-hour TSP Monitoring
2.9
All measured 24-hour TSP levels complied with the Action and
Limit Levels in the month except one action level exceedance
recorded at AM1 on 6 December 2007. The exceedance
was considered not related to the Project due to no major construction works
was carried out by the Contractor near AM1 and bad ambient air quality was
recorded by the Hong Kong Observatory on that day.
A summary of 24-hour TSP monitoring results is presented in Table 2.5.
Table 2.5 Summary of Impact 24-hour TSP Monitoring Results
|
Monitoring Station |
24-hour TSP (mg/m3) |
Action Level (mg/m3) |
Limit Level (mg/m3) |
No. of Exceedance
|
|
|
Range |
Action |
Limit |
|||
|
AM1 |
64.6 – 258.5 |
177.4 |
260.0 |
1 |
Nil |
|
AM2 |
52.5 – 173.0 |
205.0 |
260.0 |
Nil |
Nil |