Devices for Measuring Carbon Dioxide Pollution - Essay Example

? Pollution by CO2 Introduction Carbon dioxide is a vital component of essential gases present in the earth-ocean atmosphere system. Carbon dioxide is produced by anthropogenic and natural sources. Within the carbon cycle, CO2 is essential in supporting numerous biological processes. Over last several decades, the concentration of CO2 in the atmosphere has increased significantly. This increase is as a result of increased combustion of oil, coal, natural gas, and other carbon compounds. Carbon dioxide being one of the greenhouse gases, scientists around the world express concern over the rising levels of CO2 in the atmosphere. Therefore, concentration of CO2 in the atmosphere is being monitored closely in order to prevent effects of global warming (Ramseur & Parker2008, p.27). The need to curb the effects of global warming due to increased greenhouse gases has led to the development of novel devices, which can monitor air pollution by CO2. However, it is worth to mention that some of the methods in use for the monitoring of CO2 tend to be highly sophisticated, and can only be used under exceptional circumstances. Today, majority of the devices that are in use for monitoring of atmospheric CO2 are constructed using Non-Dispersive Infrared gas analyzers. However, there are several other techniques, which use chromatographic and spectrum techniques. It is necessary to note that there is an internationally accepted calibration system that helps in giving a global standard for CO2 measurements (Nowakb & King 2002, p.246). Devices for measuring CO2 pollution Fourier Transform Infrared Spectroscopy (FTIR) This is one of the methods widely used for monitoring atmospheric pollution by CO2. This technique has been in use for decades, and its working principle is based on the identification of the absorption spectrum for different gases. Therefore, FTIR operates by monitoring the whole infrared spectrum in order to identify the different absorption spectrums for gases present. Infrared spectrums produce absorption spectrums for samples that have absorption peaks that correspond to frequencies of bond vibrations within an atom. Every material has a unique combination of atoms, hence the uniqueness in the infrared spectrum produced. Therefore, the use of infrared spectroscopy can help in the quantitative analysis of a material (Xinyi 2012, p. 225). The size of peaks produced by infrared spectrums provides a direct measurement for the quantity of substance present within the test sample, which goes to extents of 10% of CO2 concentrations in the sample. The use of software algorithms has made use of the infrared spectrum a vital tool for quantitative analysis. The use of FTIR has a number of advantages over other techniques that were in use earlier. These advantages include its nondestructive nature; it also gives precise measurements that do not need any external calibration, has a high operating speed and is of a high sensitivity. Other advantages include its high optical throughput, and its mechanical simplicity.With the help of an interferometer, FTIR measures different infrared frequencies simultaneously. Therefore, this technique is reliable for the identification of air pollution by CO2 based on its unique absorption spectrum (Griffith &Stephen 2000, p.218). Advantages FTIR provides the advantage of measuring up to 50 determinants. The other advantagesincludethe reduced number of interferences, lack of frequent calibration, and a typical range of 2.5-25µm. Disadvantages The main disadvantage associated with the use of FTIR is its potential to generate a large amount of data from inferograms, which makes data analysis process cumbersome. The other disadvantage relates to difficulties in obtaining a representative background. Gas chromatography This is an analytic technique that is used in the analysis of a number of gaseous substances. Analysis of gases using gas chromatography requires the gaseous compounds under analysis to have thermal stability and sufficiently volatile. The underlying principle in the use of gas chromatography is the use of mobile and stationary phases. In this case, the mobile phase is made of an inert gas. On the other hand, the stationary phase has a packed column whereby the solid support is the stationary phase on its own or is covered using a liquid stationary phase. In the detection of CO2, a thermal conductivity detector (TCD) is used as a detector for measuring CO2 (Maeda & Onodera1995, p.55). In situations where TCD is used as the detector, the sample under analysis is injected through a gas chromatography. The use of TCD has the advantage of not destroying the sample under investigation, which makes it suitable for preparative analysis. TCD works by comparing two gas streams, whereby one gas stream has the carrier gas while the second one has the carrier gas and the test sample. The carrier gas should be of high thermal conductivity in order to have a high thermal difference between two tungsten wires. The range, when using TCD, is determined by sample concentration. In most cases, the range usually approximates 10ppmv (Harrison 2001, p.136). In gas chromatography, available techniques for measuring CO2 allow for simultaneous measurement of three greenhouse gases. In cases where TCD is applied, the analytic technique can measure a wide range of CO2 concentration ranging from 0.2 ppm to 20%. Other advantages associated with gas chromatography include its fast speed in giving results, and the ability to analyze several greenhouse gases. Combining FID and ECD detectors in gas chromatography can give simultaneous measurements for main greenhouse gases within 4mins. In addition, the technique has high precision, resolution, and sensitivity (Harrison 2001, p.141). Advantages Gas chromatography has several advantages, which include its use of small samples (1ml of a sample mixture), ability to analyze compounds that can change into vaporand it’s the cheapest, easiest, and fastest method for separating and analyzing volatile compounds. Disadvantages The greatest limitation of gas chromatography is the requirement to volatilize the material under investigation at 250C without decomposition. The other major limitation is its destructive nature because the sample is lost after analysis. Non-Dispersive infrared (NDIR) This technique functions to analyze gases that can absorb infrared such as CO2, hydrocarbons, and other greenhouse gases. This technique has the disadvantage of having poor sensitivity, which makes it best suitable for the measurement of gases at the emission source. Therefore, measuring CO2 in ambient air using NDIR is less common. However, the technique is able to measure CO2 ranging from 0-2000 umol/mol. The working principle in NDIR is that the technique does not spread any light derived from an infrared source. This implies that light is not disintegrated into its component wavelength either by means of grating or prism. However, a broad band of light is generated through a band pass filter that is set to coincide with the absorption peak of a pollutant molecule (Kumar 2006, p.275). The main challenge associated with NDIR analyzers is that gases, which take light in similar spectra region as the pollutant, will give false positive results. For example, measurement of CO2 is highly likely to be interfered with by CO since the two gases absorb light in similar spectra. One notable thing about this technique is that the presence of water in the sample can be cleared through an inlet filter made silica gel or other desiccants. Measuring CO2 in ambient air using NDIR technique may not give significant results, but its use at the emission source gives the level of CO2 pollution at the emission source (Kumar 2006, p.281). Advantages NDIR technique is of low cost, and highly reliable is assessments of air pollution by CO2. It also has the advantage of reducing interferences associated with NDIR. Disadvantages NDIR comes with a number of limitations whereby the greatest limitation is the interference from gases that absorb light in similar spectra region as that of CO2. Such gases produce false positive results. The other limitation is that CO2 and water vapor strongly absorb in the IR region. The HS135 sensor This is a gas sensor that has a semiconductor component designed on a tin dioxide. It is designed purposely for the monitoring of atmospheric CO2. The main components that make up the HS135 sensor are 4 different sensing components, and a substrate of 3mm. The sensing elements are made of thin silicon membranes. The substrate is a component of two active layers whereby one layer, which is metallic in nature, acts as a temperature control and heating system. The second layer is critical because it is responsible for monitoring of gases. This layer has a semiconductor that has tin oxide, which is sensitive to gases. The working principle behind these sensors is to detect electrical resistance of tin dioxide. Changes in electrical resistance are influenced by the surrounding gases(Muller 2010,p. 11). Advantages The HS135 sensor has the advantage of having long periods of stability as well as its easiness in application. This makes it a suitable device for family use to measure levels of CO2 pollution at the household level. The device is capable of measuring CO2 concentrations of up to 9000ppm. Disadvantages The main disadvantage associated with HS135 sensor is its inability to detect minute amounts of CO2 pollution in the air. In addition, the sensor may lose its sensitivity over a prolonged period of use. Conclusion The increased concerns over global warming call for effective techniques to monitor the level of greenhouse gas emissions in the atmosphere. Continuous monitoring of CO2 level provides relevant information for tracking CO2 emission and at the same time helps in fighting climate changes. Techniques used to measure CO2 pollution use different principles, but the common objective is to provide reliable data on the trend of CO2 and air pollution by CO2. However, much needs to be done in the development of CO2 monitoring techniques. References List Griffith, S. & Stephene, R. (2000). Precision Trace Gas Analysis by FT-IR Spectroscopy. 1. Simultaneous Analysis of CO2, CH4, N2O, and CO in Air. Analytical Chemistry, 72 (1), pp. 206–215. Harrison, R. M. (2001). Pollution: Causes, Effects and Control, London, Royal Society of Chemistry. pp. 135-150. Kumar, A. (2006). Environmental Chemistry, New York, New Age International. pp. 85-104. Muller, G. (2010). Airpollutionmonitoring using tin-oxide-based microreactor systems. Sensors and Actuators B: Chemical, 69(1), pp.108–119. Maeda, S. &Onodera, T. (1995). On-site monitoring of volatile organic compounds as hazardous air pollutants by gaschromatography. Journal of Chromatography A, 710 (1), pp. 51–59. Nowakb, T. &King, P. (2002). Local-scale fluxes of carbon dioxide in urban environments: methodological challenges and results from Chicago. Environmental Pollution, 116(1), S243–S254. Ramseur, L. &Parker, B. (2008). Greenhouse Gases: Management, Reduction and Impact, Chicago, Nova Publishers.pp. 27-35 Xinyi, J. G. (2012). Methods to assess bioavailability of hydrophobic organic contaminants: Principles, operations, and limitations. Environmental Pollution, Volume 172, pp. 223–234. Read More