6.1
According
to Section 7.5 of the updated EM&A Manual, an ambient
arsenic monitoring is required to be conducted in KTN during the clean-up
processes of arsenic containing soil and the construction phase.
6.2
The
Respirable Suspended Particulate (RSP, or PM10) was measured by High Volume Sampler
(HVS) equipped with PM10 selector following the "Reference Method for the
Determination of Particulate Matter as PM10 in the Atmosphere" Part 50
Chapter 1 Appendix J, Title 40 of the Code of Federal Regulations of the USEPA.
6.3
The
Dust-laden air was drawn through PM10 HVS fitted with a conditioned
pre-weighting filter paper, at a controlled rate. After sampling for 24-hour
(details on measurement period are provided
in Section 9.5.5), the filter paper
with retained PM10 particulates was collected and returned to the
laboratory for drying in a desiccators followed by
accurate weighting. 24-hour average RSP levels were calculated from the ratio of the
mass of PM10 particulates retained on the filter paper to the total volume of
air sampled.
6.4
The
weighted filter paper was prepared for arsenic testing through
a "Hot Acid Extraction Procedure". The extracted material was tested
for arsenic by using Inductively Coupled Plasma/Mass Spectrometry (ICP/MS). The
extraction and testing was referenced to the following methods:
l Compendium Method
1O-3.1 Selection, Preparation and Extraction of Filter Material, Center for
Environmental Research Information, Office of Research and Development, USEPA,
June 1999; and
l Compendium Method
1O-3.5 determination of Metals in Ambient Particulate Matter using Inductively
Coupled Plasma/Mass Spectrometry (ICP/MS., Center for Environmental Research
Information, Office of Research and Development, USEPA, June 1999.
6.5
Ambient
arsenic monitoring was conducted at the monitoring station(s)
under the Work Contract(s), as shown in Figure 5. Table
6.1 describes the location of the ambient arsenic monitoring station.
Table 6.1 Location of Ambient Arsenic Monitoring
station
|
EP. No |
Contract No. |
Monitoring Stations |
Location |
|
EP-466/2013/A EP-467/2013/A EP-468/2013/A |
ND/2019/01 |
KTN-DMS-4A[1] |
Temporary
Structure at Pak Shek Au |
|
EP-468/2013/A |
ND/2019/03 |
Remark:
[1]: Monitoring at the original location of KTN-DMS-4 (originally
proposed in the approved EM&A Manual) was denied as there was no
electricity supply. An alternative location (KTN-DMS-4A) was proposed.
6.6
Table
6.2 summarises the equipment used in the ambient
arsenic monitoring. Copies of calibration certificates are attached in Appendix
C.
Table 6.2 Ambient Arsenic
Monitoring Equipment
|
Monitoring Stations |
Equipment |
Model and Make |
Quantity |
|
KTN-DMS-4A |
Calibrator |
TISCH Model: TE-5025A |
1 |
|
HVS Sampler (RSP) |
TISCH
Model: TE-6070X |
1 |
6.7
Table
6.3 summarises the monitoring parameters and
frequencies of ambient arsenic during the clean-up processes of
arsenic-containing soil and construction. The ambient arsenic monitoring
schedule for the reporting month is shown in Appendix D.
Table 6.3 Impact
Ambient Arsenic Monitoring Parameters, Frequency and Duration
|
Parameters |
Frequency |
|
24-hr RSP
(Ambient Arsenic) |
Once/ 6 days |
24-hour
RSP Monitoring
Instrumentation
6.8
High
volume samplers (HVS) (GMW PM10 (TE6070X)) complete with appropriate sampling
inlets was employed for 24-hour RSP monitoring. The sampler was composed
of a motor, a filter holder, a flow controller and a sampling inlet and its
performance specification complied with that required by USEPA Standard Title
40, Code of Federation Regulations Chapter 1 (Part 50).
6.9
The
following guidelines were adopted during the installation of HVS:
l a
horizontal platform with appropriate support to secure the samplers against
gusty wind was provided;
l no
two samplers was placed less than 2 meters apart;
l the
distance between the sampler and an obstacle, such as buildings, was at least
twice the height that the obstacle protrudes above the sampler;
l a
minimum of 2 meters of separation from walls, parapets and penthouses was required
for rooftop samplers;
l a
minimum of 2 meters separation from any supporting structure, measured
horizontally was required;
l no
furnace or incinerator flue was nearby;
l airflow
around the sampler was unrestricted;
l the
sampler was more than 20 meters from the dripline;
l any
wire fence and gate, to protect the sampler, were not cause any obstruction
during monitoring;
l permission
was obtained to set up the samplers and to obtain access to the monitoring
stations; and
l a
secured supply of electricity was needed to operate the samplers.
Operating/analytical procedures for the operation
of HVS
l Prior
to the commencement of the dust sampling, the flow rate of the high volume
sampler 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.
l 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.
l The
filter holding frame was then removed by loosening the four nuts and a weighted
and conditioned filter was carefully centered with the stamped number upwards,
on a supporting screen.
l The
filter was aligned on the screen so that the gasket formed an airtight seal on
the outer edges of the filter. The
filter holding frame was then tightened to the filter holder with swing bolts.
The applied pressure was sufficient to avoid air leakage at the edges.
l The
shelter lid was closed and secured with the aluminum strip.
l 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).
l After
sampling, the filter was removed and sent to the Wellab
Ltd. for weighing. The elapsed time
was also recorded.
l Before
weighing, all filters were equilibrated in a conditioning environment for 24
hours. The conditioning environment
temperature was between 25°C and 30°C and did not vary by more than ±3°C; the
relative humidity (RH) was < 50% and did not vary by more than ±5%. A
convenient working RH was 40%. Weighing results were further analysis of RSP
concentrations collected by each filter.
6.10
The
following maintenance/calibration was required for the HVS:
l 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 were
in good working condition.
l High
volume samplers were calibrated at bi-monthly intervals using TE-5025A
Calibration Kit throughout all stages of the ambient arsenic monitoring.
6.11 Quartz filters of size 8” x 10” were
labelled before sampling. A HOKLAS accredited laboratory, Wellab
Ltd., was responsible
for the preparation of 24-hour conditioned and pre-weighed filter
papers for the monitoring team. The
balance for weighting filter paper was regularly calibrated against a traceable
standard.
6.12 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%.
6.13
Wellab
Ltd. (HOKLAS Registration No. HOKLAS083), was responsible for the extraction and
testing procedure for Arsenic and comprehensive quality assurance and quality
control programmes were conducted.
6.14 The ambient arsenic monitoring
results are summarised
in Table 6.4. Detailed monitoring results and test report are shown in Appendix
E.
Table
6.4 Summary
Table of 24-hour RSP Monitoring Results (Ambient Arsenic) during the Reporting Month
|
Monitoring Date |
Monitoring Station |
Concentration (ng/m3) |
Action
Level (ng/m3) |
Limit
Level, (ng/m3) |
|
04/04/2023 |
KTN-DMS4(A) |
1.89 |
9.36 |
11.7 |
|
06/04/2023 |
5.66 |
|||
|
12/04/2023 |
5.71 |
|||
|
18/04/2023 |
5.49 |
|||
|
24/04/2023 |
5.83 |
|||
|
28/04/2023 |
5.91 |
6.15
All
ambient arsenic monitoring was conducted as scheduled in the reporting month. During
the reporting month, around 1,054.62m3 of arsenic soil transported
to soil treatment plant and 631.57m3 treated. No Action/Limit Level
exceedances were recorded.
6.16
Should
any non-compliance of the criteria occur, actions in accordance with the Event/Action
Plan in Appendix N shall be carried
out.