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) |
|
05/02/2024 |
KTN-DMS4(A) |
5.83 |
9.36 |
11.7 |
|
08/02/2024 |
6.07 |
|||
|
14/02/2024 |
6.01 |
|||
|
20/02/2024 |
5.99 |
|||
|
26/02/2024 |
6.22 |
6.15
All ambient arsenic monitoring was conducted
as scheduled in the reporting month. During the reporting month, 943.7m3
of arsenic soil transported to soil treatment plant and 842.1m3
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.