6                LAND CONTAMINATION (AMBIENT ARSENIC MONITORING)

Monitoring Requirements

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.

Monitoring Location

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

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.

Monitoring Equipment

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

KTN-DMS-4A

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.

Maintenance/Calibration

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.


Results and Observations

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)

03/08/2022

KTN-DMS4(A)

0.73

9.36

11.7

09/08/2022

0.12

15/08/2022

1.09

19/08/2022

0.97

25/08/2022

0.15

31/08/2022

1.09

 

6.15       All ambient arsenic monitoring was conducted as scheduled in the reporting month. During the reporting month, around 225.0m3 of arsenic soil transported to soil treatment plant and 1,052.6m3 treated. No Action/Limit Level exceedances were recorded.

Event and Action Plan 

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.