Table 1. Various Techniques for Air Pollution Monitoring
Over the years, the researchers have made inroads in the ways in which air pollution monitoring and its assessment has been carried out. The authors have reviewed and analyzed the different schemes or methodologies which have been proposed by different researchers concerned with air pollution monitoring and assessment with a goal of creating a customized system which caters to specific target groups who are armed with relevant information on air pollution on a periodic basis and specifically in form of alarms whenever the need arises. The review has been carried keeping in mind the advantage and the disadvantage of the proposed scheme. In this review, they have tried to analyze only those schemes or methodologies where the researchers have added to subsequent improvement in the existing methodologies and are cost effective and easily implementable. The review includes research papers, publications, web sources, and other available literature with an eye towards providing a comprehensive comparative analysis. Thus they put forward the insights gained from the review.
Products, commodities or substances which have the capacity to modify the physical or chemical properties of air gets introduced in air in sufficient quantity to produce a measurable effect on man or vegetation are considered as pollutants.
Many investigations have been carried out to come up with the relation between the pollutants and its effects on humans and vegetation, for these investigation to be carried out, there is a need to have the information about the level of these pollutants in air, advocating requirement of a system to measure the levels of the pollutants in air. A system which records and stores the information about the pollutants can be termed as an Air pollution monitoring system. A continuous assessment of such a system is termed as air pollution monitoring.
As a result of these investigations, a basic fact has been emphasized that the localized critical concentrations of pollutants have been affecting air quality and its effect on man, animals and vegetation has suggested the need for better understanding of the involved phenomena, specifically in urban and industrial areas.
Though the pattern of air pollution has not changed much lately, but better information due to investigations carried out has resulted in improved control technologies formulation and better legislative regulations.
With rapid progress in the industrialization, the world which is mostly done compromising the existing legislation has brought the human race at a stage where it has to act and act fast.
With air pollution affecting everybody seriously in the form of increased cases of respiratory disorders specifically asthma, frequent acid rains, and rapid changes in the air quality index of the areas. Air pollution monitoring has become the need of the hour and has to become more reliable, more approachable, and more informative so that everyone right from technocrats to layman are able to get information which can be directly put to use by them.
In the recent past, the air quality monitoring was prominently based on data gathered by official organizations through networks of fixed locations. Data produced by these networks is highly accurate; however, their sparseness does not allow to completely cover the areas where they are. As these analyzers are very costly, it is not possible to commission them in large numbers. With the advent of Fixed and/or mobile solid state multi-sensory device, air pollution monitoring is experiencing a changeover and are fast replacing or competing with the conventional analyzers.
In general, the availability of low cost, low power, portable personal analyzer and cooperative air quality monitoring models may help to significantly improve the density of the urban pollution monitoring networks, eventually enabling good policies relying on high quality and high accuracy assessments and forecasting. The present day air pollution monitoring systems have been revolving around the usage of the Wireless Sensors Networks to sense and accumulate the information. The accumulated information after processing is available at the public domain on the internet.
The basic advantage of the present day air pollution monitoring system is that they transformed themselves from being an inaccessible public domain system to being an easily accessible system which has helped the researchers to move their area of research in many unexplored domains.
Though the air pollution monitoring system have become more accessible, and more information is available than ever before, the information is limited to being available on the internet. A large section of human race still has no access or limited access to the internet. Even if it is able to access the net it is not able to translate the available information for their use.
In this study, an effort has been made to review and analyze various techniques which have been used over years to monitor Air Pollution. A comparative analysis is made between different techniques and related scopes and outcomes have been discussed.
This section discusses what an air pollution monitoring system is all about.
Air pollution monitoring is required to determine the existing quality of air, evaluation of the effectiveness of control program and to identify areas in need of restoration and their prioritization.
The major objectives for air quality monitoring are as below:
Data occupies prime importance in an air pollution monitoring system which relies heavily on the data being made available to the servers to carry out assessment. The background data serves as a tool to assess the existing level of contamination and its possible effects in future.
The objective is to determine air pollution status and trend information from any continuous air quality monitoring program. The information is used to determine, whether pollution control strategies as advised by implementing authority are giving acceptable values, that is lowering of pollution levels or new or additional control are required to achieve acceptable levels.
The air quality monitoring and survey concern with systematic study of considerable segment of environment to define inter-relationship of the source of pollution, atmospheric parameter, and measurable manifestations to evaluate the character and magnitude of existing problem.
To understand natural scavenging or cleansing process undergoing in the environment through pollution dilution, dispersion, wind movement, dry deposition, precipitation, and chemical transformation of pollutants generated.
To assess the present status and judge effectiveness of air pollution control strategies and also for long term management of air quality.
For setting up of any ambient air quality monitoring station, the most important thing to be considered prior to commencement of actual monitoring is to collect its background information.
The background information that should be gathered to include the information about sources and emissions, health status of the area, demography of the region of concerned, population growth, land use pattern, and epidemiological studies. Such pre hand information will be of great help in identifying the likely effects and in particular health impacts resulting from population exposure to air pollutants.
Vehicles, industries, domestic household form the different sources in a city. For an industrial area, the information to be gathered should include the type of industry, the fuel used in that industry, the composition of the fuel, the details of pollutants emitted. Information on number and distribution of sources should be collected. This information will help to identify the pollutants which can be expected in a particular area so that it should be measured. In industries if the raw material and fuel is stacked, then in such a case the monitoring station can be set near such stacks. Information regarding the vehicle used in the particular area along with its density should be collected. Information on the types of domestic fuel used in the household of particular area should be gathered. The total pollution load being generated from these sources should be calculated with an aim to identify the significant contributors of pollution in that particular area.
Surveys should be carried out based on the complaints related to air pollution received from public of particular area. If such survey reveals that pollution levels are high then that particular area can be considered for air quality monitoring. Densely polluted areas with population more than a million can be considered for setting up monitoring stations. Data on the age and socio-economic status of a particular area also provides an important insight to setting up of monitoring stations. Location of monitoring station in such areas will help in finding exposure levels to population which can be used further in epidemiological studies to evaluate health effects of air pollutants.
Data on temperature, relative humidity, wind speed, and direction should be collected subsequently data regarding predominant wind direction, land and sea breezes, and other local metrological data need to be gathered. The monitoring station should be located in areas that are downwind from the sources. Mixing height data should also be collected from the monitoring agencies. Information regarding various seasons in a particular area along with the data on seasonal variation should also be collected. The data collected should be able to provide information regarding annual average.
Topography plays a decisive role in Local winds and stability conditions. In river valleys, there is increased tendency of developing inversions. More monitoring stations should be located in areas where spatial variations in concentrations are large. Mountains, hills, and water bodies also have a bearing on the dispersion of pollutants.
Any previous relevant survey can serve as the basis for setting up monitoring station in a particular area. These surveys could be about any health studies carried out. Such survey may be used to estimate the magnitude of the problem. Once the background information is collected, the process of setting up an ambient air quality monitoring station can be initiated and then the type of pollutants to be monitored and the distribution of the station can be decided.
The following parameters need to be decided for carrying out ambient air quality monitoring.
Information about the existing air pollutants levels and pattern within the area are crucial in deciding the number and distribution of stations. Background information on the sources and the emission along with the population figures provides the insight about the variability of pollution concentrations. The numbers of station to be put up depends upon the area to be covered, the variability of the pollution concentration in the area to be covered, the data requirements, which are related to the monitoring, pollutant to be monitored, and population figures which can be used as indicators of criticality both from view of likely air quality deterioration as also health implications.
Site selection is very crucial as an incorrect location may render the results as useless or of very limited use. Location of the sampling stations is governed by many factors such as the method of instrumentation, available resources, physical access, and safety of equipments. Stations should be established at areas which are hotbed of pollutions such as an industrial zone, urban areas, traffic intersections, etc. One of the objectives of monitoring is to determine status and trends and the air quality monitoring should be done in metropolitan cities and other urban areas so as to compare their levels and determine trends.
Before moving on to select the pollutants to be monitored, an emission inventory study may prove to be quite fruitful or alternately if any previous study is available, it can also be put to use. The pollutants expected from the sources present should be monitored. In metropolitan areas the common air pollutants such as carbon monoxide, SO , 2 NO , SPM, and RSPM should be measured on a regular 2 basis. Resource availability can play a very important role in determining the pollutants to be measured in an area.
The pollutants vary diurnally and seasonally and these variations should be taken into account for determining frequency of sampling. The precision required in the data is also important in determining frequency of sampling. Sampling should be more frequent than the frequency of variation of pollutants. The period and frequency of sampling should be such that statistically reliable averages can be obtained with the data. National Ambient Air Quality Standards states that annual average should be computed of 104 measurements taken twice a week of 24 hours duration. Thus measurements should be conducted in all the seasons so that in annual average all the seasons are represented equally. In general minimum 20% of the reading should be taken in each season.
NAAQS states the measurement methods for various pollutants. These methods should be used for conducting ambient air quality measurements. Selecting the method among the various options depends upon the resources available to sustain the measurement over a long time, detection limit of the methods, degree of skill required, etc.
Metrological parameters such as wind speed and direction, ambient air temperature, relative humidity, rainfall, atmospheric pressure, and mixing height form the necessary set of measurements which are to be carried out.
The samples collected from site should be analyzed in the laboratory. So a lab or a small area is to be earmarked which is available with necessary equipments and facilities to analyze the samples which are being made available.
For a nation like India with its vast demography it would definitely need different agencies to collaborate to conduct monitoring at a number of locations spread across the country. It is necessary to ensure that the data which is being collected and analyzed is adequate and has been collected as per the guidelines that have been set up. Internal and external audits can be carried out to ensure the same.
The data so received from the monitoring station should be recorded so that the interpretation can be carried out. The monitoring station can be at different areas such as an industry or a traffic intersection, similarly the station may be located at a plain or a plateau or a hilly area. The data collected should be validated by rejecting erroneous entries and by suitable calibration if required. The data should be recorded in the prescribed formats with the help of a suitable database application tool and this data can then be presented with any available front end application tool. The data presentation should be such that the objectives of monitoring are met.
The various objectives may be to determine daily, weekly, monthly and yearly averages.
Setting up of an air pollution monitoring system requires lots of resources in terms of personnel, infrastructure in the field and lab, equipment and finance, etc. Enough resources should be available for purchase of instruments, hiring of manpower and establishing laboratory.
To effectively carry out the monitoring it is required to employ manpower competent to carry out the prescribed task. A person with environmental science background who is well aware about various environmental acts is to be employed, and he may carry out the data compilation and processing. The field monitoring may be carried out by personnel appointed for field monitoring. A laboratory assistant is to be employed for carrying laboratory analysis. Data entry operators with requisite qualification are to be employed to carry on the data processing as and when required.
Kavi K. Khedo, Rajiv Perseedoss, and Avinash Mungur in their work “A Wireless Sensor Network Air Pollution monitoring system” investigated the use of wireless sensor network for air pollution monitoring in Mauritius [1] .
They have been able to set up an air quality index for Mauritius and have proposed a new data aggregation algorithm named “Recursive Converging Quartiles (RCQ) which has been able to eliminate duplicates, filter out invalid readings and summarize them in a simpler form which significantly reduced the amount of data to be transmitted to the sink and thus saving energy.
Though the data aggregation algorithm has decreased, the processing time and information about the air quality is quickly available, the information available is still presented in complex terminologies and gives general information about the pollution levels.
Bruno Andò, Salvatore Baglio, Salvatore Graziani, and Nicola Pitrone in their work “Models for Air Quality Management and Assessment” have proposed several linear and non linear models using the metrological inputs and neural network identification method which have been helpful toward implementing an efficient control of the pollutant source specifically CO (Carbon Monoxide) and SO (Sulphar Oxide) [2].
The importance of environmental models in air quality management and assessment has been underlined. The proposed models are a useful tool allowing the enforcement of the air quality standards in both urban and industrial areas. The discussed methodology has been applied in two inhabited areas to test the efficiency of the proposed approach and good results have been obtained.
Though the models have been designed and tested and have provided fruitful results, but still the models do not provide much of an information to a layman who does not understands it terminologies.
Octavian A. Postolache, and P. M. B. Silva Girão, “Smart Sensors Network for Air Quality Monitoring Applications” have developed an air quality monitoring system that uses smart sensors in a wireless network and have embedded neural network processing blocks distributing the processing charge between the embedded systems (Web sensor), and the Web browser installed in a personal computer. The proposed air quality monitoring system based on a wireless smart sensor network and on neural network processing blocks embedded on the sensing nodes has presented the following advantages [3].
The system power requirement is around 8 W, which is sufficiently high and it needs battery which can recharge periodically. The output of a specific tin dioxide sensor arrays depends not only on temperature and humidity, but also on the concentration of other gases and vapors. The effect of this cross influence on the accuracy of the measurement is substantial and more so the system still does not provide any information in the form of some alerts to the end user specifically the layman.
Han Zhi-gang and Cui Cai-hui H Henan (University China) in their work “The Application of Zigbee Based Wireless Sensor Network and GIS in the Air Pollution Monitoring” have introduced a new method for air pollution monitoring [4]. They have discussed a schema in which they have proposed the use of Zigbee and GIS and have discussed the advantages of using the Zigbee protocol along with GIS system, but they have limited their work on a very basic system and there is a need to carry on large number of experiments to verify the validity of the schema.
Santosh Hariharan in his work “A Novel Integrated Instrumentation Technique for Air Pollution Monitoring” has proposed an integrated air pollution monitoring technique that will possibly allow a detailed estimate of the major air pollutants in air through a single instrument used at a larger scale. He has proposed the usage of ‘The Flame Photometry Detector’ and ‘Flame Ionization Detector ’ and ‘The Chemiluminescence method’ however the overall cost of the instrumentation technique is high and some work has to be done in this field to decrease the cost as far as possible [5].
A. R. Al-Ali, Imran Zualkernan, and Fadi Aloul, in their work “A Mobile GPRS-Sensors Array for Air Pollution Monitoring” have designed, implemented and tested a distributed mobile air pollution monitoring system using the GPRS public network. The system utilizes city buses to collect pollutant gases such as CO, NO2, and SO2. The pollution data from various mobile sensor arrays is transmitted to a central several that make this data available on the Internet through a Google Maps interface. The data shows the pollutant levels and their conformance to local air quality standards. However much more work would be required to put the system to commercial use. The information available is not readily available to the end user and the intended user is required to log on to internet to get the information [6].
James J.Q. Yu, Victor O.K. Li, Fellow and Albert Y.S. Lam in their work “Sensor Deployment for Air Pollution Monitoring using Public Transportation System” have proposed a novel air pollution monitoring system by deploying sensors in a public transportation system. A new optimization problem has been formulated for selecting the buses to deploy the sensors, called BSDP. The main idea was to install sensors on buses and with the movement of the buses; the sensors can cover a much larger area compared with stationary sensor stations. This raises the problem of selecting buses to install sensors and the system needs to be subjected to real time processing to give results which are useful to the end users [7] .
Abdullah Kadri, Elias Yaacoub, Mohammed Mushtaha, and Adnan Abu-Dayya in their work “Wireless Sensor Network for Real-Time Air Pollution Monitoring” have proposed an end-to-end system for ambient real-time air quality monitoring and prediction. The system has two main components, the multigas monitoring stations and the M2M platform. Four solar powered multigas monitoring stations have been deployed and the data of four months have been collected, cleaned, and analyzed. The monitoring stations communicate in an M2M fashion with a backend server using GPRS communications. The system has been able to provide a user friendly interface in the form of website where the end user logs in and is able to obtain the required information. Though the system is very user friendly still it needs the end users to log on to the net to access the data and the analysis has been done of very few deployed sensors [8] .
Vijay Sivaraman, James Carrapetta, Ke Hu, and Blanca Gallego Luxan in their work “HazeWatch: A Participatory Sensor System for Monitoring Air Pollution in Sydney” have worked upon building and deploying a low-cost participatory system for urban air pollution monitoring in Sydney. The aims of the project are noble, to get a better understanding of urban air pollution and to empower citizens with information about their personal exposure, and what steps they can take (e.g. route planning) to better manage their air pollution exposure. The end users are required to carry on a pollutant sensing unit which transmits data through Bluetooth to the end users’ mobile phone. A mobile app has been developed which provides information regarding levels of various pollutants to the end user. Though the system has been designed to provide information to the users on the mobile phones, the users are required to carry on the sensing unit along with them. The sensing unit may not be handy to many users and large scale testing is to be done before the system is validated [9].
Luca Capezzuto, Luigi Abbamonte, Saverio De Vito, Ettore Massera, Fabrizio Formisano, Grazia Fattoruso, Girolamo Di Francia, and Antonio Buonanno in their work “A Maker Friendly Mobile and Social Sensing Approach to Urban Air Quality Monitoring” have proposed the design of a framework for highly distributed, maker friendly and user centric air quality monitoring, aimed to involve the citizen in multiple stages of the monitoring process. At this stage, a prototype sensor box, mountable on bike or transportable in backpack, has been built; an application for Android devices to interact with the node has been developed, and a MongoDB backend server has been activated on ENEA-GRID/CRESCO facilities. Early tests conducted with current implementation account for the user's capability of qualitative assessment of their personal exposure. Social sharing possibility allows already for the widespread of pollution indexes obtained during mobility sessions [10].
The end users are required to take along with them the measuring module which then transfers the information through Bluetooth to the mobile phone. Though the system has been designed to provide information to the users on the mobile phones, the users are required to carry on the sensing unit along with them. The sensing unit may not be handy to many users and large scale testing is to be done before the system is validated.
S. Devendra K. Verma & P. K. Barhai in their work “Design & Development of WINGSNET (Wireless Intelligent GPS Based Sensor Network) System for monitoring Air Pollution and Radiation based on WiFi & WiMAX Communication Network” have designed & developed an air pollution monitoring system for monitoring NO2, NO, O3, CO, CO2, SO2, PM10, PM25 based on WiFi and WiMAX Communication Network. WINGSNET System is designed to monitor Air Pollution and Radiation Nano-Sensors spread over geographical area. The Sensor-Units/Nodes (SU) are intelligent and smart enough to process the Sensor-Data and determine the Status as Normal, Alert or Alarm Condition and report the Sensors ID, Location, Status, Date/Time, etc., to the Reporting Station (RS), which may be mobile/stationary. The RS will transmit the statusinformation through a Base Station (BS) to a Centralized Monitoring Station (CMS). The system proposed has not been put to practical implementation and validation [11].
Abdul Hadi Nograles H, Agbay, Christopher Paolo D, Flores, Ian Steven L., Linsangan, Manuel Jr. A., Salonga, and John Bethany C. in their work “Low Cost Internet Based Wireless Sensor Network for Air Pollution Monitoring using Zigbee Module” have developed a system based on MQ-2 which is commercially available in the market and is capable of detecting seven types of gas compounds thereby saving 1/7th of power consumption if multiple sensors were to be used. The functionality of the system was verified with lab testing for cigarette smoke as well as car exhaust emission. At the laboratory level, the system has shown promising performance, but the real test lies in the deployment of the sensors and its assessment in real time [12].
Suraj Hebbar, Karuppasamy V, Kiran G K, Amit Kumar, A. S Ashwini Kumari, Raghavendra Yasasvi, Amit K. Gupta, Vijay Mishra, Bharadwaj Amrutur, and Navakanta Bhat, in their work “System Engineering and Deployment of Envirobat- An Urban Air Pollution Monitoring Device” have designed an easy user interface with display and keyboard for setting up various parameters during measurement. They have added the capability to add up an SD card interface with which it is possible to immediately make the data available to the intended users. The user has option of creating his customized setting for transmitting data at appropriate inter vals. This version of Envirobat demonstrates monitoring urban air pollutants and logging the acquired data for online access. There is a great flexibility for user to access the data from the device. The online GUI provides better user experience by visualizing the graphs [13].
The researchers intend to include touch screen and Zigbee module to make it more user friendly and promote better intercommunication between the modules. Though the system has turned much more user friendly, still the data availability is at website only which provides a GUI interface and the end user again needs to have an access to the internet to view or obtain the available information.
Ryuji Koga Megumi Kosaka, and Hiroya Sano in their work “A Fast Local Monitoring of Dilute NO by a Tunable Laser” proposed a real-time non contacting, point monitoring system for nitrogen monoxide. The monitoring system uses a grating-tuned pulsed dye laser and a specially developed microcomputer assisted signal processor system. The system is sensitive for analyzing a gas concentration from 0.03 parts per million per meter (ppm/m) theoretically (which should be divided by an optical path length) to 0.4 ppm/m experimentally. The system was satisfactorily reliable in detecting sulfur dioxide and nitrogen monoxide. The system was prone to electronic noises and its reliability depended upon tuning of the dye laser which was done mechanically by a stepper motor [14].
Mohammad Jahangir Ikram, Agha Ali Akram, and Mannan Amin in their work “A Low-Cost Solution for Urban Air-Pollution Monitoring using Existing Infrastructure and Loosely Connected Ground Based Sensing Equipment” proposed a cost effective and generic solution for urban air pollution monitoring using existing computing resources and infrastructure. The design has been modularised into three subsystems - the Data Acquisition System (DAS), Data Transmission System (DTS), and the Data Collation System (DCS). The DAS is composed of ground-based sensing equipment attached to the PCs, of citizen-volunteers geographically spread out in a city, connected to a central server via the internet. The devices periodically send snap-shots of urban environmental conditions of their respective localities to the central server using the DTS. Here, the DCS seamlessly aggregates received data to build a comprehensive database (DB) of the history of environmental conditions in a given urban setting and allows internet users to view analyses run on that data. Air Pollution monitoring at a low cost using the existing infrastructure has been demonstrated. The system is web centric and requires that the users should log on to the internet at least once a day [15].
David C. Wolfe, Jr. and Robert L. Byer in their work “Air Pollution Monitoring by Computed Tomography” have shown the feasibility of laser scanned computed tomography for regional air pollution measurements. The requirements are quite modest, especially since the above ranges were obtained using a CW laser. The use of pulse techniques would allow an increase in effective power levels by factors of up to this would permit ranges that are limited by the destruction of the pulse by atmospheric turbulence and not laser input power. The system is quite complex and expensive and needed support from the existing government owned installations [16].
J.J. Wilting, and H. Van Den Berge in their work “Air Pollution Monitoring network in the Netherland” with support from Dutch National Institute of Public Health and Philips were able to develop an SO2 monitor and developed a nation- wide air pollution monitoring network in the Netherlands. The idea is to have one national centre, located centrally in the country, connected to a number of regional air pollution monitoring networks. The network was supposed to measure actual air pollution levels for the identification of critical concentration of pollutants for instant alerting purposes, to establish potential air pollution levels and to establish trends in the potential air pollution levels for long term prediction purposes. The system gave fairly good results, but concentrated only on pollution due to Sulfur Dioxide and needed support from the government as well as non government agencies [17].
Young Jin Jung, Yang Koo Lee, Dong Gyu Lee, Keun Ho Ryu, and Silvia Nittel in their work “Air Pollution Monitoring System based on Geosensor Network” have designed an air pollution monitoring system which involves a context model and a flexible data acquisition policy. The context model is used for understanding the status of air pollution on the remote place. It can provide an alarm and safety guideline depending on the condition of the context model. It also supports the flexible sampling interval change for effective tradeoff between sampling rates and battery lifetimes. The overall system was effective and gave information about temperature, humidity, illumination, dust, carbon dioxide, ultra violet, wind direction, wind speed, air pressure, and altitude. The system was again web centric and the end user is able to view alarms if they long on to the internet [18] .
Nihal Kularatna, and B. H. Sudantha in their work “An Environmental Air Pollution Monitoring System Based on the IEEE 1451 Standard for Low Cost Requirements” have discussed about an Environmental Air Pollution Monitoring System (EAPMS) for monitoring the concentrations of major air pollutant, complying with the IEEE 1451.2 standard. This system measures concentrations of gases such as CO, NO2, SO2, and O3 using semiconductor sensors. Further, the EAPMS is capable of warning when the pollutant levels exceed predetermined maxima. The environmental air pollution monitoring system has been successfully implemented in compliance with the IEEE 1451.2 standard, a standard interface has been provided to industry to efficiently connect transducers to microcontrollers and to connect microcontrollers to networks where the gas pollutant monitoring STIM can be moved from one NCAP to another. This capability provided by the standard is a great advantage to the system designers and sensor manufacturers, and it reduces the burden of designing various products to suit various networks.
The semiconductor gas sensors can be successfully used to monitor the target gas concentrations. The usage of the semiconductor sensors add several advantages to a system such as low cost, quick response, low maintenance, ability to produce continuous measurements, etc. The system has an alarm capability in term of sirens and the results are available on PC through network interface on a GUI, so the user is required to log on to the PC and need to have NCAP processor [19].
Zivorad Mihajlovic,Vladimir Milosavljevic, Vladmir Rajs, and Milos Zivanov in their work “Appliction of GPRS modules in Data Acquisition and control of devices for Air Quality Monitoring” have developed a modern GPRS based system for Air Pollution Monitoring which measures concentration of gases such CO, CO2, Nh3, CH4 and H2S. Development of mobile technology and GPRS modem, made it possible for this system to become a part of everyday life. The system consumes less power and requires less maintenance. The system needs to be subjected to more testing and it requires the users to log on to the PC to know about the status of pollution [20] .
Halit Eren, Ahmed Al-Ghamdi, and Jinhua Luo in their work “Application of ZigBee for Pollution Monitoring Caused by Automobile Exhaust Gases” have discussed the development of ZigBee based system which monitors the automobile exhausts using gas sensor array and the information from the sensor array has been transmitted to a remote location by ZigBee wireless technology. Quantitative and qualitative analysis of gases has been conducted at the remote location by a computer. Programs have been developed in Lab View and Excel to display data and alarm conditions. Results indicate that unlike the automobiles using natural gas, the unleaded and premium unleaded fuel automobiles can have significant effect on the environment conditions due to their high level of toxic gas emission. The system is suitably fine, but it again requires the users to log on to the PC to know the status of the pollution [21].
Jong-Won Kwon, Yong-Man Park, Sang-Jun Koo, and Hiesik Kimin in their work “Design of Air Pollution Monitoring System using ZigBee Networks for Ubiquitous-City” have discussed implementation of the air pollution monitoring system using ZigBee technologies and embedded system. As the ZigBee was applied to communication for monitoring system, available feasibilities are confirmed. The system possesses low cost, wide coverage using flooding routing protocol, especially mobility on wiring to remove the limitation of traditional wired network systems for U-City. Therefore research and development will affect positively for constructing U-City. The paper makes clearly concept of U-City and provides development model for successful U-City driven strategies. The system is suitably fine but it again requires the users to log on to the internet to know the status of the pollution [22].
Considering the above system which have been developed for air pollution monitoring over the years we can in a very broad spectrum divide the air pollution monitoring systems into three categories
Since the air pollution monitoring has been initiated, it has always challenged the researchers to look in for a cost effective option which could replace the conventional government owned systems. Many researchers have worked upon developing the new instruments and putting them to use. However, it has been found that such an option did not turned out to be much popular as it required the researchers to put in a lot of hard work and more, so the cost of the developed instruments were at the higher end more or less same as that of the government owned systems. As a result, a substantial headway has not been achieved using this technique.
This technique turned out to be a much better and a very cost effective option as compared to the scheme discussed above and it was possible to put into use the available data which was obtained by the government owned system. However, though this being a very cost effective options, it required the researchers to put in a lot of efforts in convincing the authorities about their intentions and to make them agree to part away with the available data. More or less it had to be a government funded project which gave access to very few researchers who were able to make themselves viable for such a project. Many a time due to lack of permission, a genuine research option was not able to move ahead. As a result this technique though popular than the one above has given just around satisfactory results.
This technique has turned out to be the better of the other two considering the variety of work that has been carried out. The scheme involves the use of Wireless Sensor Nodes as the data collectors and these sensors would then transmit information at a centrally located server. This server would then process the information as per the requirement.
This scheme scored above the other two schemes in terms of the cost and the time involved to get the system working. As cost of setting up the system was comparatively quite low, a lot of researchers have been able to put on quite a considerable research and have been able to present system which could replace or supplement the conventional government owned system effectively and easily. The government will be available with data at micro levels and would be in a better position to channelize the resources and to make necessary changes in the guidelines as per the area under consideration.
From Table 1, the authors concluded that air pollution monitoring scheme can be broadly divided into three categories. First category of Monitoring involves development of new analyzers which can then be used for air pollution monitoring. The second category involves using the data which can be accessed from the already existing systems and then processing it to achieve the desired results. Finally, third scheme covers usage of Wireless Sensor Network to carry on with the air pollution monitoring.
Table 1. Various Techniques for Air Pollution Monitoring
They have presented three categories in which the air pollution monitoring system can be categorized. From Table 2, and Table 3, they tried bringing out the issues concerning the three schemes.
Table 2. Work Done in Line of Developing New Sensors and Developing New System with Cooperation from Government or Local Authorities
Table 3. Work Done Towards Developing Web Based Monitoring System
From the first scheme depicted in Table 1, the researchers summarize that though development of new analyzers is essential, it doesn't convert into an economically viable option, and hence the findings and research have more or less remained confined at experimental levels. Secondly, working on data obtained from the government agency or authority is always a better proposition, but access and permission issues stall such an effort.
From the second scheme depicted in Table 3, we observe that hard wiring between the transmitter and receiver was eliminated and a Wireless Sensor Network was introduced, but we find that most of the systems need much more work before they can be put to commercial use, more so the desired information is not readily available and it is required to log on to PC with internet capability to access the information. From Table 4, we finally observe that wireless sensor based networks with more features which made the system more user friendly were introduced which allowed the users to interact effectively with the system at a specified interface with considerable ease. The system still remains web centric and it is still required for the user to log on to the internet and more, so the terminologies used are difficult to be understood for a layman.
Table 4. Work Done Towards Moving the System to be More User Centric
Having gone through the standard guideline prescribed for an Air Pollution Monitoring System, we can make a statement that setting up these systems is cumbersome and involves a lot of finances. Air Pollution monitoring has been seen as a responsibility of the government and has been largely confined to officials who have been appointed to see the system working. Though this has been done quite efficiently, but at large it has never allowed the common man to be concerned. Awareness about the environment has been on rise with more and more number of persons being increasingly concerned with the causes and effects of environment and the role they play as the stakeholders. Secondly, the available systems which have been designed and proposed by different researchers have been shifting the air pollution monitoring systems from being a government controlled, government operated system to systems which are being installed and executed by concerned researchers and organization. The monitoring systems have given suitable accuracy and their performance have been suitably validated. These systems have made the data readily available to the concerned user be it a technocrat or a layman. However, we still find that there is a gap in what has been developed and what is the need of the present times. With a highly developed communication scenario, there is a definite need to enhance the existing system to a level, where it presents itself as a user friendly system which can be operated with ease and the concerned user is able to understand its observations easily and is able to implement them effectively.