2.1 What is air pollution
Air problem is the phenomenon of harmful substances and gas which generate by artificial activities contaminate to air cause the air quality become worsen. Because air pollution can be appear no matter at indoor or outdoor places, so air pollution can be divide into indoor air pollution and outdoor air pollution, under indoor and outdoor air pollution, numerous of reason and effect will effect the air quality at indoor and outdoor place air quality, like “Street Canyon Effect”, weak ventilation at indoor place, harmful gas release by chemical substances etc. So indoor and outdoor air pollution will affect different aspect of human and environment, cause worsen of human health and environment quality. For this dissertation, air pollution at confined public transportation interchange belongs to indoor air pollution. The affective of indoor air pollution to human health are similar to general air pollution, and case “sick building syndrome” according to article “Indoor air pollution and exposure assessment of the gulf cooperation council countries: A critical review” indoor air pollution is a serious health which will case different diseases like lung cancer, pneumonia, ischemic heart diseases, stroke etc. The main factor of causing indoor air pollution is the pollutants on ambient air influent into indoor scape, poor ventilation at indoor environment and over-crowed. (Amoatey, et al., 2018)1. In addition, the air pollution at open-air public transportation belongs to outdoor air pollution. Compare to indoor air pollution, air quality at outdoor environment may be better because pollutants will be easier to dissipate, the barrier at outdoor environment are less than indoor environment lead the ventilation effective may be better than indoor environment.
2.2 Possible air pollution source
To view the pollution source of a interchange, it must be review the daily activities and the surrounding environment like the facilities nearby, some facilities like ventilation exhaust vent is one kind of air pollution source. Public Transportation Interchange is a place that let passenger vehicle to stay, pick up and drop off, so gas emission from passenger vehicles always is the main pollution source of interchange. Apart from this, ventilation exhaust vent mentioned above is a kind of air pollution source. Like Ping Shek Public Transportation Interchange, there are a MTR station ventilation facilities locate at the side of exit of interchange, and one exhaust vent is face to the exit of interchange and a bus waiting area, it is possible that exhausting of air ventilation is the main source of pollutants produce. For the aspect of Sze Mei Street interchange, the possible air pollutant source will be the construction site opposite to interchange. This is a public housing estate, railway station construction site, involve mining work, dust can be emit to environment nearby through airflow if that construction site do not conduct any dust control measure like watering and mud covering. For the aspect of Diamond Hill Station interchange,
2.3 Factor of causing indoor and outdoor air pollution
In a transportation interchange, there are numerous of factor, source that can case indoor or outdoor air pollution, it can be from movable and unmovable machine like vehicle and ventilation system, human activities like smoking, those activities are possible to produce air pollutants, chemical substances like SO2, NO2, PM2.5 etc. There are few aspect of factors that can causing indoor and outdoor. Poor ventilation, construction design and environment nearby.
Construction design
For the aspect of construction design, confined interchange will be have a higher risk on air pollution than semi-confined and open-air interchange because the effective of air circulation is bad, pollutants conduct at indoor space do not have air circulation to volatile, when human activities generate more and more pollutants, pollutants will be accumulate.
Surrounding environment
For the aspect of surrounding environment , environment that conduct gas emission and dust will be the culprit to outdoor interchange due to the fact that air or nature wind will contain those pollutants from pollution source to interchange. In addition, the layout of building nearby can be other factor that causing outdoor air pollution indirectly, this effect is “Street Canyon Effect”.
The principle of “Street Canyon Effect” is the high rise building locate at two side of road construct a “artificial canyon”, base on the circulates downwards direction of air convection, air pollutants will sink, let the air quality at low position will be worse than high position. On the other hand, circulates downwards direction of air convection will also confine the pollutants inside “artificial canyon”, let the pollutants looping inside the canyon constantly through airflow.
Human activities
For the aspect of human activities, it is mentioned above that smoking in transportation will be the main factor that influent the indoor air quality, hazard chemical substances like Tar, Ammonia etc. are colorless substances with sharp odor and toxic, not only influent to environment quality, but also human health. So, Hong Kong government has been set the anti-smoke area in indicate transportation interchange to decrease the influent level to environment quality and human health.
Literative Review
3.1 Situation in Hong Kong
The air pollution problem at public transportation interchange in Hong Kong is serious. According to “Report of the Panel on Transport for submission to the Legislative Council” point out that in 64 public transportation interchange which manage by Transportation Department ,the average value of NO2 concentration in 1 hour measured in half of the public transportation interchange were excessed the limit of Air Quality Objectives of Hong Kong. (Panel on Transport, 2017)2. Environmental Protection Department had announced the value of air pollution measure in 64 public transportation interchanges which manage by Transportation Department between February of 2016 to February of 2019. Among 64 public transportation interchanges, 9 interchanges are exceed the limitation of average NO2 concentration in 1 hour (300 ug/m3), the exceed percentage were between 9% to 129%. In the aspect of SO2 and CO, no interchange are exceed the limitation, but the different of SO2 and CO concentration value are great. It shows that the NO2 pollution is a main issue of air pollution in public transportation interchanges (Finance Committee Member, 2019). 3The reason of causing the situation of not fulfil the criteria of average value in 1 hour may be the ventilation system at individual interchange are bad, like low air volume, operation time of ventilation system are short etc.
3.2 Literative Review
3.2.1 The Practice Note on Control of Air Pollution in Semi-confined Public Transport Interchanges
Environmental Protection Department has established a practice note in 1998 called “The practice Note on Control of Air Pollution in Semi-confined Public Transport Interchange”. This practice note is a guideline on the design, operating and managing the ventilation system which install at semi-confined public transportation interchange and to manage the CO, SO2 and NO2 at semi-confined public transportation interchange, aims to protect public health and increase the air quality at interchange, Like practice note regulated that it is afford to build walls or barriers to brother the air flow to decrease the accumulate of air pollutants.4 Some of the citizens doubted that practice note is useless in manage the air quality at public transportation interchange because the air quality criteria of practice note is outdated.
3.2.2 The Air Pollution Control Ordinance
The Air Pollution Control Ordinance is a law that regulate the fixed source of air pollution from specified processes. In “The Air Pollution Control Ordinance” has already contain “Air Quality Objectives” that list out the air quality criteria, each air pollutant list out in “Air Quality Objectives” are having its upper limit of concentration at regulate average time, the detail of the criteria list at “Air Quality Objectives” have been shown in Appendix. Apart from the specified processes, “The Air Pollution Control Ordinance” have also regulate the vehicle emission in gas exhaust which must fulfil the gas exhaust standard which is the equal strict with United State, European Union and Japan; setting the decommissioning period to vehicles no matter before Euro 4 or register after The Air Pollution Control (Air Pollutant Emission) (Controlled Vehicles) Regulation available. 5
3.3 Comments from civil organizations
“Momentum 107” has been conducted an survey at 10 public transportation interchanges which have been indicated that the environment problem are exist. The items of air pollution surveying PM2.5 and CO2 were record. The result of survey shown that the index of PM 2.5 at 6 interchanges were exceed 25ug/m3 which is the 24-hour standard of WHO. Raymond Ho Man Kit, convener of Momentum 107 think that the poor air quality at interchanges is because the ventilation system are old and lack of maintenance, on the other hand, he also think that the situation of each does things in his own way of departments are also one of the reason that case poor air pollution at interchanges because this way lead the cleaning job of ventilation system stagnant. He will send the surveying result to government to expect the attention of government, and government can set the criteria which is about the environment quality of public transportation interchange. (Mingpao, 2019)6
Capture the article on the website www.inmediahk.net, “Clean Air Network” has posted a article to criticism the ordinances establish by government that the critical of concentration of air pollutants formulate in“ The Practice note on Control of Air Pollution in Semi-confined Public Transport Interchanges” are outdated base on the guideline relate to the upper limit of average NO2 concentration in 1 hour are no update for 30 years, let this ordinance loss the usage of protecting public health. Beside, “Clean Air Network” indicate that the air pollution situation at interchange are serious base on the result of their survey, at the waiting area after the exhaust vent of bus, the concentration of NO2 was 343ug/m3, it has already excess the Air Quality Objectives by 71.5%, criticism that this situation is a threat to public health. (健康空氣行動, 2018)7
3.4 Detection Method
| 污染物 | 室內 | 室外 | 檢測方法 |
|---|---|---|---|
| NO₂ | 被動式擴散管 (Passive Diffusion Tube) | 連續監測儀 (Continuous Monitoring Analyzer) | 化學發光法 (Chemiluminescence Method) |
| PM2.5 | ✔ | ✔ | PM2.5 偵測器：利用雷射光照射至 PM2.5 顆粒，顆粒散射後由光偵測器測量濃度，可偵測範圍為 3μm 至 2.5μm (Chloe, 2019) |
| SO₂ | ✔ | ✔ | 紫外螢光法：利用紫外光激發 SO₂ 分子，分子在振動弛緩過程中發出螢光，由光電倍增管偵測並電子化處理。 |
3.5 Treatment Technology
| 治理技術 | 方法與效益 |
|---|---|
| 車輛排放 — 氣體轉液體 (GTL/DME) | 利用天然氣轉化的液體燃料 (如 GTL、DME)，可減少重型車輛 NOx 排放 5–37%，PM 排放 10–38%。 |
| 氫燃料添加劑 | 改善燃燒循環並降低排放。英國測試顯示，將氫氣注入進氣口可提升燃油效率並減少 NOx、PM、碳氫化合物及一氧化碳排放。 |
| 光觸媒材料 | 在陽光下可去除環境污染物。環境產業委員會報告指出，將光觸媒技術應用於道路可有效降低 NOx 和 PM。 |
4. Methodology
For this project, NO2 and the wind speed of indoor space will be the surveying objectives, the main reason are NO2 are the main pollution substances at transportation interchange, monitor the concentration of NO2 to view the real situation to find out the indication of exceed the limitation of NO2 concentration from other organizations is true or not. On the other hand, wind speed is a main factor that will impact to the air quality at transportation interchange, so wind speed will also be survey for this project.
4.1 Sampling location (map, describe surrounding environment)
For this project, semi-confined,confined and open-air public transportation interchange will be chosen as the sampling location to conduct a comparison of the air pollution situation at 3 kinds of public transportation interchange. Semi-confined public transportation Ping Shek Public Transportation Interchange, confined interchange Diamond Hill Station Public Transportation Interchange and open air interchange San Po Kong (Sze Mei Street) Public Transportation Interchange will be chose as the surveying location base on the reason of to conduct the air pollution situation of 3 kinds of public transportation interchange that mentioned above, in addition, those public transportation interchange have been indicated by government, environmental protection organizations and residents that have the high level of air pollution like NO2 pollution, ventilation effective is not good and involve to different sensitive receivers and those interchanges are the main public transportation interchange of opposite district. So, there have the necessary to conduct the survey to understand the real situation of air pollution at those interchanges. The basic information and the description to the surrounding environment are shown below:
- semi-confined：Ping Shek Public Transportation Interchange
- confined：Diamond Hill Station Public Transportation
- Open-air：San Po Kong (Sze Mei Street) Bus Terminal
The basic information and the description to the surrounding environment are shown below:
| 建築類型 | 調查地點 | GPS 座標 | 基本資訊 | 周邊環境 | 通風方式 |
|---|---|---|---|---|---|
| 半封閉 | 坪石公共交通交匯處 | 22.334021, 114.210148 |
啟用於 2006 分為兩層，位於 Infinity 8 地面層，連接彩虹站 |
周邊為坪石邨住宅、交通道路及學校 | 機械通風 + 自然風 |
| 封閉 | 鑽石山站公共交通交匯處 | 22.340688, 114.201831 |
啟用於 1997 年 11 月 位於荷里活廣場地面層，對面為鑽石山站 鄰近 Rhythm Garden |
四周為牆壁及商舖，出口面向龍蟠苑；背面為荷里活廣場出入口；另有半封閉開口朝向常遠街，作為通風位置 | 機械通風 + 風扇 |
| 露天 | 新蒲崗四美街巴士總站 | 22.337630, 114.201677 | 無任何機械通風系統 | 周邊為住宅、學校及工業大樓；前方為工業大樓群，南側為小學，背面為住宅區；北側有施工場地，為主要污染源之一 | 自然風 |
4.2 採樣程序
| 程序 | 工作內容 |
|---|---|
| 規劃目標 | 確立測量地點、時間、方法、儀器與標準；完成職業健康與安全模組。 |
| 採樣 | 不同位置的數據由儀器紀錄，同時記錄 GPS 座標以便在論文中呈現。 |
| 採樣後 | 將儀器測量結果轉換為 Excel 檔案，方便後續數據處理。 |
| 數據處理 | 利用表格、地圖、圖表等方式呈現數據。 |
4.2.1 Record GPS location
GPS location (with latitude and longitude) of each measuring points and places should be record and present in report. It is convenient to represent the location of measuring points and drawing map by utilize GPS because GPS is a international universal positioning system, once enter GPS code (latitude and longitude), map with guide to the approximate location with match GPS code. So, GPS will be record and utilize to represent the approximate location of each measuring points.
4.2.2 Measurement steps
| 步驟 | 職責 |
|---|---|
| 調查前 | 設定測量儀器，特別是數據記錄間隔。 |
| 進入場地後 | 開啟 NO₂ 分析儀並運行程式。 |
| 測量後 | 保存數據至分析儀的日誌頁面；測量並手動記錄風速。 |
| 數據傳輸 | 返回實驗室，將 NO₂ 分析儀的數據傳輸至軟體，生成圖表與 Excel 檔案。 |
4.3 Result visualization
| 形式 | 動機 | 優點 |
|---|---|---|
| 折線圖 | 比較不同日期的數據 | 顯示數據的升降趨勢，適合展示不同日期的關係。 |
| 平面圖 + 測量點 | 展示測量點位置與潛在污染源 | 讓讀者清楚辨識測量點位置。 |
| 表格 | 清晰呈現每次調查結果 | 方便比較不同調查時間的結果，數據簡潔明瞭。 |
5. Ethics and risk assessment
學生姓名：容文達 導師：洪令豪
專案標題：公共交通交匯處空氣品質
活動日期：2019 年 12 月至 2020 年 4 月（待確認）
重大危害
- a) 吸入有害/毒性氣體
- b) 若測量位置過近道路，可能被車輛撞擊
受影響人員
- a) 調查員（本人）
- b) 司機與調查員
風險評估
| 危害 | 可能性 (1-6) | 嚴重性 (1-6) | 無控制措施風險 (/36) |
|---|---|---|---|
| a) 吸入毒氣 | 4 | 4 | 16/36 |
| b) 車輛撞擊 | 3 | 4 | 12/36 |
控制措施
- a) 在排氣口附近測量時佩戴口罩
- b) 提高測量位置，避免靠近車道