29 Application of Geospatial Technology in Air Pollution Management

Dr. Puneeta Pandey

1. Objectives

The main objective of this module is to make the reader aware about how the geospatial technology, i.e., Remote Sensing (RS) and Geographical Information System (GIS) helps in monitoring and managing air pollution for its effective mitigation.

2. Introduction

Air pollution is one of the major concerns in all the countries that exist throughout the world, be it a developed or a developing country. This issue of air pollution is increasing continuously day by day. The need for a green and clean-living environment is increasing in the present times, with the advent of the socio-economic development. Air pollution has become an alerted global issue as large amount of pollutants are being discharged into the atmosphere everyday. Greenhouse gas emissions mainly from energy, agricultural land and transportation sector is causing change in the climate because of their high residence time in the atmosphere. Environmental pollution is our concern nowadays because all our daily activities are directly or indirectly related to the environment. Air pollution in the Asian countries are increasing at an unprecedented rate. Although higher level of air pollution level is mostly concentrated in the urban areas, but rural areas are also approaching these levels at a very fast pace. The World Health Organization (WHO) has reported that in developing countries, air pollution in the urban areas has resulted in over 2 million deaths per annum along with various cases of respiratory illness (WHO, 2005; Cities Alliance,2007; WHO, 2014). Major contributor of air pollution in these areas is transportation sector; although domestic, commercial and industrial activities also play their role to make the air quality worse in these areas. Apart from the gaseous air pollutants, particulate matter (PM) also plays an important role in the degrading the air quality. The particulate matter includes the solid or liquid particles that are suspended in air. These PM can be divided into 3 major categories:

(A) PM10 – These particles have aerodynamic diameter less than 10µm and are commonly called coarse particles.

(B) PM2.5 – The particles whose aerodynamic diameter is less than 2.5 µm, are commonly referred as fine particles.

Under the Air (Prevention and Control of Pollution) Act, 1981; Central Pollution Control Board (CPCB) has notified National Ambient Air Quality Standards (NAAQS) for 12 criteria pollutants. These are common pollutants which are considered to be very dangerous and have serious effects on human health. The Criteria Pollutants include PM10, PM2.5, Sulphur Dioxide (SO2), Nitrogen Dioxide (NO2), Ozone (O3), Lead (Pb), Carbon Monoxide (CO), Ammonia (NH3), Benzo(a)pyrene (BaP), Arsenic(As), and Nickel (Ni). Controlling these pollutants is very important as they pose serious threat to the human health.

2.1Air Pollution and its Health Effects

The magnitude of the London smog of 1952, which affected a large number of people, was the first incident that made people aware about the damage done to the atmosphere due to the process of industrialization. It caused a manifold increase in the Suspended Particulate Matter (SPM) levels and resulted in over 400 deaths. Air Pollution represents an enormous health hazard as it is one of the major reasons of death in India and all other countries around the globe. Every unusual suspended material in the air, which creates difficulty in breathing or normal functioning of the human organs, is known as air toxicant. The most common health problems caused because of the air pollutants are related to respiratory, cardiovascular, ophthalmologic, dermatologic, neuropsychiatric, hematologic, immunologic and reproductive systems. The most susceptible group of people to air pollution includes children and the elderly people as well as those who are suffering from respiratory or cardiovascular diseases; since, even small amount of the air toxicant can be very dangerous for them. Long exposure to the air pollutants can lead to some serious health problems such as chronic respiratory diseases and lung cancer. Even healthy people can experience health impacts from the polluted air including irritation in the respiratory tract or breathing difficulties during the exercise or outdoor activities. The current health status, types of pollutants, concentration and the length of exposure to the pollutants actually defines one’s actual risk to the adverse effects.

2.2 Air Pollution Sources and Monitoring of Pollutants

There are various sources through which the air pollutants enter into our atmosphere and then to our body. These sources can be classified into two major categories: natural and anthropogenic sources. Natural sources include events that pollute the air directly or indirectly; it includes events like forest fire, volcanic eruption, wind erosion, pollen dispersal, evaporation of organic compounds etc. However, the major part of the pollutant present in our present atmosphere is mainly because of the anthropogenic sources; which has a long list of contributors. Anthropogenic sources include pollution via transportation, industrialization, biomass burning, energy production, agriculture sector etc. Air pollution modelling helps in the apportionment of the sources by using different models such as dispersion and receptor modelling. This in turn helps to identify the possible sources which are causing pollution. But for this, monitoring of the pollutants is important. In India and several other countries, monitoring is done manually using several types of air samplers such as High-volume samplers, Fine Particulate sampler, Indoor and Handheld Samplers and Gaseous samplers. The monitoring is an expensive process and requires expertise of people handling the instrument, and large manpower. Geospatial technology can be used wisely to continuously monitor the air pollutants and identify the possible sources of pollutants for their effective management.

3. Geospatial Technology

The geospatial technology is a term used to describe various modern tools contributing to geographical mapping and analysis of earth and human societies. This technology has been evolving since first maps were drawn; during 19th century, first camera was sent aloft on balloons and pigeon to take some aerial photograph. In 20th century, the location of camera was shifted from birds and balloons to airplanes. With the invention of computers, storage and transfer of images together with the development of associated software, maps and datasets on socio-economic and environmental phenomena became possible. There are various Geospatial Technologies such as Geographic Information Systems (GIS), Remote Sensing (RS), Global Positioning System (GPS) and Internet Mapping Technology. Out of these, Remote Sensing and Geographical Information System have proven to be very useful in the air pollution studies.

3.1 Remote Sensing

Remote sensing is used for collecting information about the earth without making any physical contact with the surface. This technique utilizes sensors mounted on a platform that measures the energy reflected from the earth. These sensors can be mounted either on a plane or air-borne structure; or on satellite (Lim et al., 2009). There are two basic types of sensors: passive sensors and active sensors. Passive sensors do not have their own source of energy and detect the energy reflected energy from the sun (Fig 1). However, the active sensors use their own source of energy to detect the energy reflected back from the target (Fig 2). Remote sensing finds varied applications for studying earth’s surface features such as land cover/use mapping, urban planning, monitoring of forests and wildlife, transportation, watershed as well as wetlands management and so on.

3.2 Geographical Information System (GIS)

As the name suggests, GIS is a tool used for working with the geographic information. In simple words, GIS is computer software that links the geographic information with the descriptive information. GIS has rapidly developed since 1970s in terms of both technical and processing capabilities, and today are widely used all over the world for a wide range of purposes. GIS is a computer-based system that provides four sets of capabilities to handle georeferenced data that includes Data capture and preparation, Data management and management, Data manipulation and analysis, and Data presentation. GIS has a broad range of applications similar to remote sensing. GIS can be successfully applied to various sectors such as intelligence, environmental pollution, education, health and human services, natural resources, transportation etc.

4. Role of Geographic Information System (GIS) and Remote Sensing (RS) in air pollution management

The ultimate goal of any air quality management plan is to ensure minimal impact of pollutants on human health. Therefore, the exposure to pollutants and health assessment becomes the major component of a management plan; and to get information about these two parameters, continuous monitoring is very important (Gulia et al., 2015). Also, air quality model plays a very crucial role in formulating air pollution control and management strategies by providing information about better and more efficient air quality planning (Patania et al., 2009). Monitoring of air pollutants in most of the developing countries is done manually using air sampling instruments. This monitoring is usually done by regulatory monitoring authorities such as Environmental Protection Agency (EPA), Central Pollution Control Board (CPCB) and State Pollution Control Boards (SPCBs). The association of these air pollutants and the human health has relied on the ground measurements which are done by the CPCB or SPCBs. Although ground-based measurement is considered to be the most accurate, but this approach has certain weakness. The ground monitors cover sparsely and unevenly distributed area. Besides, in developing countries, the ground-based monitoring is mainly focused in the urban and some suburban areas. To overcome these issues and to get continuous data, use of GIS and Remote Sensing data has increased in recent past. Although the use of satellite remote sensing data has been used to track particle air pollution events since 1970s; the quantitative studies of atmospheric particles began after the launch of NASA’s Terra satellite in December 1999. Nowadays, many countries are using satellite data to monitor and manage air quality.

4.1 Management and monitoring of air pollutant using GIS

One of the effective tools in air quality management is Geographic Information Systems (GIS) because of its ability to capture, manipulate, analyse and map geographically referenced data. Map making ability of GIS by integrating database operations such as query and statistical analysis with the visualization and geographic analysis makes it a powerful tool to explain events, predicting possible outcomes and planning abatement strategies. The air automatic systems contribute to identify changes in the environmental quality continuously over time and space; helping to determine in a quick manner and detect early problems of environmental quality data serving for environmental management and protection. Among the basic parameter to know about the air quality, the required parameters measured in the field include wind direction, wind speed, temperature, relative humidity and pressure etc.; the other parameter includes SO2, NO2, CO, O3, PM etc. GIS can be integrated with different types of dispersion models such as AERMOD, CALINE-4, OSPM, CALPUFF, CALGRID, EDAMS, ADMS etc, which provide information about different pollutant and dispersion patterns of pollutants. For example, Elbir et al. (2004) developed a decision support system for air quality management in big Turkish cities. The GIS system was based on CALPUFF dispersion model and associated database to calculate emission from various sources. From the obtained data, the manager can give out timely warning and propose the appropriate measure to manage, control and protect the environment as well as identify the responsibilities of production facilities/ industrial zones and of cities.

4.2 Determination and management of air pollution using Remote Sensing Technique

In air pollution monitoring and management application, remote sensing is considered as an important tool. Its application is really important in the context of estimation of Aerosol Optical Thickness/Aerosol Optical Depth (AOT/AOD) using Moderate Resolution Imaging Spectro Radiometer (MODIS), the Multiangle Imaging Spectro Radiometer (MISR), or the Visible Infrared Imaging Radiometer Suite (VIIRS). Aerosol Optical Thickness/Aerosol Optical Depth (AOT/AOD) is defined as the integral of aerosol extinction coefficient along the entire vertical atmospheric column, it is considered as one of the Essential Climate Variable (ECV) that influences climate, visibility and quality of the air. Satellite derived AOD represent the amount of the particulate present vertically in the atmosphere of the earth and it can be considered as overall indicator of pollution in any urban area (Lim et al., 2009). Aerosol concentration can be measured directly by the ground-based sun photometer or estimated by sensors on the satellite (Figure 3).

Figure 3: Methods for measuring AOD (https://www.eol.ucar.edu/field_projects/ace-asia)

The ground-based measurements have high accuracy and temporal frequency but they represent a limited spatial range around the station. Conversely, data of the satellite provides information about the aerosols at larger scale with moderate quality and lower frequency (Nguyen et al., 2014).

The satellite data also provides data for other pollutants apart from PM; there are satellites that provide information near the surface on ozone’s chemical precursors and VOCs (Duncan et al., 2014).There are several instruments that measure infrared (IR) wavelength of light to infer the CO concentration. Instruments that observe thermal infrared (TIR) wavelength can measure CO in the free troposphere, although the vertical resolution is poor; data from these instruments are shown to be useful in tracking long range transport of pollutant. The management process requires information about the pollutant and after getting requisite information about the pollutant, it becomes easy to manage. The satellite remote sensing has an extensive application in identifying the aerosol columnar properties, especially in terms of optical depth, their composition, morphology and vertical distribution. This eventually provides the evidences which are used in establishing the source-transport-receptor relations of aerosols over a synoptic scale (Mhawish et al., 2018). Moreover, satellite data of atmospheric composition are often used to identify the pollution emission, transboundary movement of the pollutants, forecasting the air quality, and also relating the air quality with the human health.

Conclusion

The air pollution problem originates from various sources and has different types of pollutants; geospatial technology can help in providing information on how much exposed how many population affected and determine environmental impact from present to future developments. Therefore, it gives a chance to the decision makers to establish strategies that can minimize the pollution levels. This can also provide data about the population health risk status like information regarding cancer, allergy and respiratory problems and the data can be used effectively to tackle the root cause of the problems related to air pollution.

Reference

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