6.
LAND CONTAMINATION (AMBIENT ARSENIC MONITORING)
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 |
Monitoring Parameters,
Frequency and Duration
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 |
Monitoring Methodology and
QA/QC Procedure
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.
Laboratory Measurement /
Analysis
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) |
|
03/12/2024 |
KTN-DMS4(A) |
6.15 |
9.36 |
11.7 |
|
09/12/2024 |
4.14 |
|||
|
13/12/2024 |
5.53 |
|||
|
19/12/2024 |
6.18 |
|||
|
23/12/2024 |
4.46 |
|||
|
27/12/2024 |
5.38 |
6.15
All ambient arsenic
monitoring was conducted as scheduled in the reporting month. During the
reporting month, 1,108.7m3
of arsenic soil transported to soil treatment plant and 0m3 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.