2.1 TSP levels were monitored in the reporting month in accordance with the EM&A Manual. Appendix B shows the Action and Limit Levels for the environmental monitoring works.
2.2 High volume samplers (HVS - Model GS-2310 Accu-vol) complete with the appropriate sampling inlets were installed for 24-hour TSP sampling. The HVS is composed of a motor, a filter holder, a flow controller and a sampling inlet and its performance specification complies with USEPA Standard Title 40, Code of Federation Regulations Chapter 1 (Part 50 Appendix B). A portable dust meter was used for the 1-hour TSP monitoring. Table 2.1 summarises the equipment used.
Table 2.1 Air Quality Monitoring Equipment
|
Equipment |
Model |
|
HVS Sampler |
GS 2310 Accu-vol system |
|
Calibrator |
GMW 25 |
|
1-hour TSP Dust Meter |
Laser Dust Monitor – Model LD-1 (L) |
Monitoring Parameter, Frequency and Schedule
2.3 The monitoring parameters and frequency are summarised in Table 2.2. The monitoring schedule for the reporting period is shown in Appendix C.
Table 2.2 Frequency of Air Quality Monitoring
|
Parameters |
Frequency |
|
24-hour TSP |
Once/6 days |
|
1-hour TSP |
Three times/6 days |
2.4
In accordance with the EM&A
Manual, five air quality monitoring stations, as shown in Figure 2.1, were
selected for 24-hour and 1-hour TSP sampling. With the consent from ER and IC(E), an alternative location was chosen for MA1 (
2.5 The locations for the air quality monitoring stations are summarised in Table 2.3
Table 2.3 Air Quality Monitoring Stations
|
|
Description |
Sensitive Receiver in vicinity |
|
MA1 |
|
SR19 |
|
MA2 |
|
SR20-3 |
|
MA3 |
|
SR58 |
|
MA4 |
Rivera Apartment |
SR25 |
|
MA5 |
|
SR28 |
24-hour TSP Monitoring
Operating/Analytical Procedures
2.6 Operating/analytical procedures for the operation of HVS are as follows:
·
The sampler was placed on a horizontal platform with appropriate
supporting structure such that:
-
the filter was at least 1.3 meters above ground;
-
no two samplers should be placed less than 2 metres apart;
-
the distance between the sampler and an obstacle, such as buildings,
would be at least twice the height that the obstacle protrudes above the
sampler;
-
a minimum of 2 metres separation from walls, parapets and penthouses
would be required for the rooftop samplers;
-
a minimum of 2 metres separation from any supporting structure, measured
horizontally would be required;
-
airflow around the sampler would be unrestricted;
-
no furnaces or incineration flues would be operating near the sampler;
-
the sampler would be more than 20 metres from the dripline;
and
-
any wire fence and gate, to protect the
sampler, should not cause any obstruction during monitoring.
·
Prior to the commencement of the dust sampling, the flow rate of the
high volume sampler was properly set (between
·
For TSP sampling, fibreglass filters (G810) were used [Note: these
filters have a collection efficiency of > 99% for particles of
·
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 monitoring
station.
·
The filter holding frame was then removed by loosening the four nuts and
carefully a weighted and conditioned filter was centred with the stamped number
upwards, on a supporting screen.
·
The filter was aligned on the screen so that the gasket formed an
air-tight 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 aluminium strip.
·
The timer was then programmed. Information was recorded on the record
sheeting, 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 transferred from the filter holder of the
HVS to a sealable plastic bag and sent to the laboratory for weighing. The
elapsed time was also recorded.
·
Before weighing, all filters were conditioned for 24 hours before
weighing under temperature of
·
All measurement procedures in section 2.3 of the EM&A Manual were
followed during the reporting period.
Maintenance
2.7 Proper maintenance would be provided for the HVS:
·
The HVS motors and their accessories have been properly maintained.
Appropriate maintenance such as routine motor brushes replacement (time
interval for replacement is about 500 hours) and electrical wiring checking
have been conducted to ensure that the equipment and necessary power supply
were in good working condition.
·
Initial calibration of HVS was conducted upon installation of equipment.
The subsequent calibration would be provided at 2-month intervals using GMW-25
Calibration Kit.
1-hour TSP Monitoring
Measuring Procedures
2.8 The measuring procedures of the 1-hour dust meter have been in accordance with the Manufacturer’s Instruction Manual as follows:
·
Set POWER
·
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.
·
All measurement procedures in section 2.3 of the approved EM&A
Manual are followed during the reporting period.
Calibration Details
24-hour TSP Monitoring
2.9 Calibration Procedures of HVS are as follows:
A certified orifice transfer standard with a
calibration curve shall be used for the calibration.
Ö[ H2O.(Pa/Pstd).(298/Ta) ] = m.Qstd
+ b (1)
where H2O is the manometer reading of the calibration orifice
Pstd = 760mmHg (
Qstd = standard volumetric flow rate, std m3/min at 760mmHg and 298K
Pa,
Ta are respectively the ambient pressure and
temperature during calibration.
m, b are respectively the slope and intercept of the
calibration line.
Connect the transfer standard to the inlet
of the sampler (without the filter or filter cartridge being installed).
Connect the orifice manometer to the orifice pressure port. Inspect the
manometer’s connecting tubing for crimps and cracks. Make sure that there are
no leaks between the orifice unit and the sampler. Open the manometer valves
and blow gently through the tubing. Watch for the free flow of fluid.
Check that the flow recorder is connected
properly. Inspect the flow recorder’s connecting tubing for crimps and cracks.
Zero the above manometers if necessary.
Disconnect the motor from the flow
controller and plug it directly to an AC power source.
Measure and record the ambient temperature,
Ta, and the barometric pressure Pa during calculation.
Adjust the variable resistance or, if
applicable, insert the appropriate resistance plate (or no plates) to achieve
the desired flow rate.
Let the sampler run for at least 2 minutes
to re-establish the run temperature conditions. Read and record the pressure
drop across the orifice (H2O) and the flow recorder reading (I)
during calibration.
Calculate [H2O.(Pa/Pstd).(298/Ta)]1/2. Then determine Qstd
from the orifice calibration curve either by direct curve or by calculation
using equation (1).
Repeat steps 7 - 9 for four additional flow
rates distributed over a range that includes 1.10 to 1.70
standard m3/min. Then turn off the power of the sampler.
Calculate I[(Pa/Pstd).(298/Ta)]1/2 and plot I[(Pa/Pstd).(298/Ta)]1/2 against Qstd.
Use a programmable calculator or a computer
to determine the best fit straight line by linear regression and find out the
slope (m1), intercept (b1) and correlation coefficient
(R) of the equation 2:
I[(Pa/Pstd).(298/Ta)]1/2
= m1.Qstd + b1 (2)
If r<0.990, rerun all the points or only
the point with the greatest deviation and then recalculate. Repeat steps 9 - 13.
·
The 1-hour TSP meter was checked at 3-month intervals and calibrated at
1-year interval throughout all stages of the air quality impact monitoring.
2.10 Calibrations certificates for the equipment employed for air quality impact monitoring are presented in Appendix D.
2.11 Dust monitoring was conducted for both 1-hour TSP and 24-hour TSP at all the monitoring stations in the reporting month. All monitoring data and graphical presentations of the monitoring results are provided in Appendix E. Key findings and observations are provided as below:
2.12 All monitoring data complied with the Action/Limit Levels in this reporting period. A summary of the 1-hour TSP levels at the five monitoring stations is given in Table 2.4.
Table 2.4 Summary of 1-hour TSP Impact Monitoring
Results
|
|
1-hour TSP (mg/m3) |
Action Level (mg/m3) |
Limit Level (mg/m3) |
|
|
Mean |
Range |
|||
|
MA1 |
83.7 |
74.8 – 88.7 |
425 |
500 |
|
MA2 |
85.6 |
75.0 – 91.7 |
412 |
500 |
|
MA3 |
85.7 |
75.1 – 95.4 |
424 |
500 |
|
MA4 |
81.6 |
76.0 – 88.6 |
425 |
500 |
|
MA5 |
89.4 |
77.4 – 102.2 |
428 |
500 |
24-hour TSP Monitoring
2.13 In the reporting period, all monitoring data complied with the Action/Limit Levels. A summary of the 24-hour TSP levels at the five monitoring stations is given in Table 2.5.
Table 2.5 Summary of 24-hour TSP Impact
Monitoring Results
|
|
24-hour TSP (mg/m3) |
Action Level (mg/m3) |
Limit Level (mg/m3) |
|
|
Mean |
Range |
|||
|
MA1 |
64.9 |
45.3 – 94.7 |
166 |
260 |
|
MA2 |
46.7 |
23.3 – 64.3 |
156 |
260 |
|
MA3 |
57.2 |
41.7 – 91.0 |
154 |
260 |
|
MA4 |
59.0 |
47.4 – 67.7 |
149 |
260 |
|
MA5 |
55.6 |
29.4 – 116.2 |
151 |
260 |
2.14 In the reporting month, all the air quality monitoring events were conducted in accordance with the schedule. Details of the monitoring schedule in the reporting month are provided in Appendix C.
2.15
All 1-hour and 24-hour TSP monitoring
results complied with the
2.16
Dust levels remained rather low
in the reporting month due to frequent drizzle and rainy days. Dust sources other than site activities
included road traffic along
2.17 Weather data including temperature, wind speed and wind direction is annexed in Appendix M. The information was obtained from Hong Kong Observatory Tuen Mun Meteorological Station.