Project Description

The Hong Kong and Pearl River Delta Pilot Air Monitoring Project is divided into two parts: Project I (Ozone) and Project II (PM2.5). The sampling sites for both projects are shown in the below picture, with a yellow circle representing the Project I sampling site, and red circles the Project II sites.

Project I: Ozone

Pollutant background:

Ozone (O3) is a secondary pollutant, formed from a series of photolytic (initiated by the sun) chemical reactions between gases in the atmosphere and highly reactive molecules called "radicals". Past research has linked NOx (NO2 and NO) and VOCs (Volatile Organic Compounds) with the production of ozone. With NOx and VOCs both acting as ozone precursers, one could easily assume that the answer to lowering ozone levels would be to lower NOx levels, VOC levels, or both. However, this is not always the right answer! An interesting phenomenon of ozone production is it's tendency to be either NOx-limited or VOCs-limited - in which case lowering one of the compounds will have a much greater effect than lowering the other. Also, lowering the wrong gas phase species could even lead to an increase in ozone levels. Thus, the ozone problem is a complex one, and needs to be studied for the unique conditions in Hong Kong so that effective control strategies can be prescribed.

Project I Objectives:

1. Assess the accuracy of pollutant emission inventories for the Hong Kong and Pearl River Delta Region.
2. Identify specific VOCs and VOC-sources that contribute most to the formation of photochemical smog.
3. Quantify the relative contributions of local ozone production versus ozone that is transported from outside the region.
4. Complete a preliminary investigation of the relative benefits of various emission-control strategies for reducing the severity of photochemical smog.

Project II: PM2.5

Pollutant background:

PM2.5 (particles having diameters less than 2.5 micrometers) are directly emitted and and formed through secondary reactions in the atmosphere. PM2.5 in urban areas is typically composed of a variety of compounds including sulfate, nitrate, and elemental and organic carbon. The sources of these particles are generally related to fossil fuel combustion, although other sources include cooking, seaspray, and fugitive gas emissions. Once created, PM2.5 can stay in the atmosphere for days to weeks and thus can be transported over large distances.

Project I Objectives:

1. Analyze previous PM2.5 samples that were collected by the Hong Kong Environmental Protection Department at two heavily urbanized sites and one remote site over a one year period.
2. Set up a network of seven monitoring stations to measure PM2.5 for October (2002), December (2002), March (2003), and June (2003). The sites represent both urban and remote areas, as well as sites downwind of major source areas. The sampling sites are: Tap Mun (Hong Kong), Central and Western (Hong Kong), Tung Chung (Hong Kong), Shenzhen (China), Zhongshan (China), Conghua (China), and Guangzhou (China). At these sites, operators from Hong Kong EPD, Peking University, and Guangdong Research Section of Environmental Sciences have been trained to use the PM2.5 samplers installed.
3. The collected filter samples from the seven sites will be analyzed chemically to estimate which sources are the most important for the PRD PM2.5 pollution. Meteorology of the region will be studied to help estimate the degree to which PM2.5 is transported from one region to another versus being locally produced.

Nylon filters that were used during sampler set-up and testing in Shenzhen, China. The filters on the left were run for about 3-4 hours while the ones on the right were run for 24 hours, all at a flow rate of approximately 8 L/min. There was a lot of PM2.5 that day in Shenzhen!