Modeling Particulate Matter Dispersion in Metro Manila
Kaibigan ng Kaunlaran at Kalikasan (KKK) in partnership with Clean Air Asia and in cooperation with Manila Observatory and a Professional in Meteorology (1) has completed a 2-year Study on Air Dispersion in Metro Manila
An atmospheric dispersion model (2) is a:
The Project is essentially aimed to:
Improve the understanding of respirable particulate matter pathway in Metro Manila through an updated dispersion map based on emission inventory for mobile, stationary and area sources, validated by monitoring and source apportionment data;
Provide stakeholders including government agencies, the LGUs, oil players and the transport group with a science-based air quality management tool.
The project focused on primary PM10 and PM2.5 coming from major mobile, point, and area emission sources. The study domain includes the 16 cities and one municipality comprising Metro Manila.
The Air Dispersion Modelling (ADM) process includes the following basic steps:
1.) Data collection, covering
Terrain data (Guidelines from US Geological Survey)
Land use data (Guidelines from US Geological Survey and European Space Agency)
Gridded emission rates, for major mobile, stationary, and area sources
2.) Selection of dispersion model – the study used the CALPUFF (3) modeling system, an internationally acceptable model, which is among the models recommended by the EMB under its Memorandum Circular 2008-003.
3.) Determination of resolution of analysis– the dispersion model simulated the shortterm (1-hr and 24-hr) and long-term (annual) concentration levels and a 500m x 500m grid resolution for the modeling domain.
Emission Inventories (EIs) which are key inputs in estimation of emissions are derived from
Data collection, covering Traffic counts, industrial, commercial, and domestic fuel consumption, and
Emission Factorswhich estimates emissions based on activities, e.g. travel of a particular type of vehicle over a certain distance (i.e. traffic), involved.
Validation of the modeled concentrations was carried out by comparing the model results with air quality monitoring data in selected sites. The results show good comparisons.KEY RESULTS. These are depicted in the figures below.
Figure 1. Results of Modeled PM10Dispersion Map From All Sources of Pollution
Figure 2. Results of the Modeled PM2.5
From All Sources, Left Map. At the right are charts of 24-hour air quality in certain areas (Source: The NCR Air Quality Division)
(The triangles shown in the map are the monitoring stations of the Environmental Management Bureau)
The Meteorological Characteristics – Wind Vectors
These influence the quality of air in certain sectors of Metro Manila. The map of the Wind Vectors is shown in Figure 3.
Figure 4. Wind Vector Superimposed in Northern Domain of the ADM Study Area
OBSERVATIONS AND CONCLUSIONS
The air quality in Metro Manila varies depending on location and time of day or period of the year; Mobile sources contributes largest fraction to air quality.
Higher concentrations in the north are partly explained by the wind regimes such as during the Habagat season shown in Figure 4. Winds over Manila Bay are from the southwest, while winds near Laguna Lake are from the southeast. The converging winds help confine pollutants inside Metro Manila, and allow emissions from the south to add to those on the north. Additionally, industries in the North also contribute to air pollution.
Fuel, Vehicles, Topography and meteorology are the same in Metro Manila. This raises the question as towhy air quality vary in different sectors. Also, it is notable from Figure 2 that the air quality vary over a 24-hour period when in fact the same fuel and type of vehicles are involved.
"LOCAL SOLUTIONS TO LOCAL PROBLEMS"
There are good reasons to believe that local traffic impacts significantly on air quality of a particular area; and explains partly variations in air quality over different sectors of Metro Manila and over a 24-hour period for a specific site.
Restricting parameters in fuel quality should distinguish between the "nice" to have and the "compelled"-to-impose specifications. To illustrate the Phl ban on lead and restrictions in MTBE in gasoline was brought by compelling health reasons. The reductions in Sulfur concentrations in gasoline and diesel fuels were occasioned by the requirements of vehicle manufacturers for compatibility with OBDs (On Board Devices) that regulate emissions of conventional pollutants. The Philippine fuels are compliant with standards for these parameters.
"Euro" Fuels, Biofuels and Organic Pollutants
Robust discussions continue relating to "euro" fuels, organic pollutants and biofuels. Specifications relating thereto may impact on air quality and is expected to create definite implications on fuel cost and reliability with attendant impacts on the economy.
Strictly "Euro" standards refer to emission limits of the exhausts of vehicles, measured in weight pollutant per distance travelled by vehicle while air quality is measured in terms of concentration of pollutants in the ambient air, measured in weight of pollutant per volume of air. It is also notable that Euro standards e.g. as prescribed in the 1999 Philippine Clean Air Act were determined before the introduction of biofuels. The true measure of air quality is the concentration in the ambient air which is the parameter used in this ADM study.
Biofuels are recognized to result in lower fuel efficiency in terms of weight pollutants per distance travelled. Biodiesels are reported to result in cleanerexhaustgases. Bioethanols are suspected to cause aldehyde concentrations in the air. The value of an Air Dispersion Modeling is that it shows the overall impact in terms ofconcentrationsof pollutants in the ambient air as influenced by various factors among which is fuel quality.
Among the organic pollution parameters are aromatics, olefins, Polycyclic Aromatic Hydrocarbons (PAH). The challenge to regulators is how the concentration of such organic substances in the fuel will ultimately influence the quality of ambient air recognizing that these organics are burned in the engines. The products of combustion are carbon dioxide and water which are harmless to human health.
Without any doubt traffic is a big factor contributing to air quality. The Phl government recognizes the seriousness of traffic congestions in the urban areas from a holistic social impact. A shift from cars to mass transit should be a prime consideration in the master plan. Resolving the problem cascades into the improvement of air quality.
Traffic is integrated in this Study in the generation of the Air Dispersion Maps.
Among the regulatory aspects that the study suggests are:
The EMB NCR has recently set up Operations Center for AQM, the photographs shown below:
Online/Real time continuous monitoring of PM10/PM2.5 in twelve (12) stations in Metro Manila provide both immediate and medium term basis for action plans.
Photographs of the NCR Operations Center
NCR Air Shed Chair and Concurrent EMB NCR Director Ms. Vizminda Osorio shown above with Dr Ed Alabastro, Executive Director of KKK in the NCR Operations Center
Mr. Diosdado Doctor of EMB NCR pointing to the on-line monitoring results
LONG TERM APPROACH
These include the following which also results in other significant impacts management:
1.) Dr Emmanuel Garcia Anglo, Ph.D. in Meteorology, University of the Philippines Sr. Associate Air Quality Scientist, AMEC Foster Wheeler, Calgary, Alberta, Canada
2.) Guidelines for Air Dispersion Modeling Memorandum Circular 2008-003 Aug 14 2008
3.) CALPUFF is an advanced non-steady-state puff dispersion model that simulates the effects of time- and space-varying meteorological conditions on pollution transport, transformation, and removal. CALPUFF can be applied for long-range transport and for complex terrain.
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