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Principle component analysis of flue gas exhaust and health risk estimates for the population around a functional incinerator in the vicinity of Rawalpindi Pakistan
⁎Corresponding author. Tel./fax: +92 5190643017.
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Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Peer review under responsibility of King Saud University.
Abstract
In this investigation, a long term monitoring of flue gas (FG) was performed, which was emerging from a point incinerator, situated in the vicinity of Rawalpindi city of Pakistan. It was aimed to analyze and correlate the spread of particulate matter, and that of exhaust gases in the surrounding residential areas. The study spanned three consecutive years of investigation. The principal component (PCA) and cluster analysis revealed two distinct groups of gasses from the exhaust i.e., CxHx, H2S, SO2 and CO and NOx, NO, NO2, and CO2 in PC 1 and 2, respectively. The distribution of Particulate matter 10 (PM10) remained constant over the period of three years. The concentration of PM10 remained higher than USEPA safe limits on all the sampling sites. PM10 on most of the sites correlated with the flue gasses emerging from the point source. The results indicate the influence of the flue gas exhaust on the surrounding environment, and a probable association with the public health.
Keywords
Rawalpindi
Flue gas analysis
Pakistan
Air pollution
Health hazards
- CO
-
carbon monoxide
- FG
-
flue gas
- O3
-
ozone
- SO2
-
sulphur dioxide
- PM
-
particulate matter
Abbreviations
1 Introduction
The incinerator is a major point source contributing to widespread air pollution. The major pollutants in flue gas emissions of incinerators include CO, SO2, NOx, CO2 and particulate matter (PM). According to Ahmad et al. (2011), many large cities around the world harbor massive air pollutants, which demand continuous monitoring of these pollutants in order to make better policies for their control. These issues have gained attention owing to their adverse effects on human health and ecological systems (Ghauri et al., 2007).
Incinerators are used for thermal decomposition of organic and inorganic solid wastes, although they release large concentrations of air pollutants. The incineration process is no doubt an effective way of solid waste management, but at the same time, it is also a source of air pollution, therefore, the process of incineration remains a highly controversial topic. A large amount of solid waste is generated in Pakistan, which is managed improperly. In Rawalpindi city, a few hospitals, have incinerators but, they are not functional. To combat the issue, a three-chambered incinerator was initiated in the vicinity of Morgah, in order to meet the requirements of waste management. This incinerator also provides a better waste management option for the hazardous hospital waste. A number of studies have been conducted in Pakistan to assess the air pollution from different sources, but there are scarce studies on comprehensive analysis of any FG exhaust. This study aims at monitoring air pollutants from point source, to adopt effective strategies for controlling air pollutants in addition to availing the benefits of solid waste incineration practice.
2 Materials and methods
2.1 Study area
Study area for PM10 measurement, included the surrounding areas of incinirator (point sources), detailed information on the study areas was obtained from field visits, and published/unpublished data of IEE reports of AGL Power Plant geological survey of Pakistan JICA-CDA Study, 1988 etc., in collaboration with Union council of Morgah, Kotha Kalan, of AGL Power Plant, ecological Survey of Pakistan. The settlement of Morgah village, harbors a population of around 16,000 individuals. Included in the union council of Morgah, are the Dhok Mistrian and Kotha Kalan site 1, (S1) in southern and eastern regions respectively. Other settlements in the sampling sites include the Lalazar Colony, in north east, Land Park in east, Fauji Foundation College (S2). Some notable localities in the same union council are Jhamra Abadi, Nai abadi, Dhoke Bareen (S3), Dhok Nawaz, Revenue Colony and Army Officers Colony (S4). The point sources of pollution fall within the Morgah, Rawalpindi
2.2 FG and PM10 analysis
The FG analysis was conducted with the help of a Portable FG Analyzer System Testo 350 equipped with an O2 measurement cell as a standard. The analysis spanned from May-2009 to July 2011. The readings were taken on monthly intervals. The equipment was fitted with a standard gas-sampling probe which had a length of 700 mm at a maximum temperature of 1000 °C. An infrared measurement module was used for the measurement of multiple gasses including SO2, NO2, NO, NOlow, CO, COlow, CO2, H2S, and CxHy. For the analysis of PM10, the GRIMM analyzer: 1) Model 1.108 2) with a flow rate of 1.2 L/min was used.
2.3 Statistical analysis
The statistical analyses were performed using Ms-Excel, Excel stat, and SPSS ver.13.0. The Principle component analysis (PCA) was performed on both Excel stat (vector) and SPSS (biplot) analysis (shown in Fig. 1) to identify the meaningful components of the FG data. The initial analysis showed that variable and number of observations were well suited for the PCA (KMO = 0.67, Bartlet test P < 0.005). The cluster analysis (CA) was performed to visualize the underlying groups.
Principle component and cluster analysis of flue gas exhaust.
3 Results and discussion
In the current study, the analysis of a FG exhaust from a prominent incinerator in the vicinity of Rawalpindi city of Pakistan was conducted. The average concentrations of FGs are presented in Table 1. Analysis showed that during the three years (2009–2011), there were non-significant changes in the average concentration of gasses in exhaust. However, the concentration of CO (with highest mean concentration of 419.5 ppb in the year 2010 and a mean total of 302.1 ppb) dominated the profile throughout this time. Concentration of NO and NOx had second highest gases in the exhaust profile of FGs (mean concentration ranging between 18.7–19.2 and 21.6–38.3 ppb, respectively) (Table 1). CO2 and CxHx were also concentrated in the exhaust as compared to rest of the gasses; their release remained almost the same over time.
Years of observation
CO
CO2
CxHx
H2S
NO
NO2
NOx
SO2
2009
Mean ± Std
248.3 ± 45
3.7 ± 1.4
0.3 ± 0.1
3.4 ± 0.7
18.7 ± 10
2.9 ± 1.0
21.6 ± 13.8
9.57 ± 0.3
Min
18
2.2
0.2
1
5
1
5
1.1
Max
745
5.8
0.5
18
34
14
48
28
2010
Mean ± Std
419.5 ± 43.9
3.6 ± 2.1
0.6 ± 0.1
3.3 ± 0.78
17.9 ± 4.9
0.4 ± 0.07
38.3 ± 6.23
7.47 ± 2.2
Min
68
0.4
0.1
1
1
0.1
1
4.3
Max
1490
6.2
1.4
25
45
0.8
212
12.3
2011
Mean ± Std
188.3 ± 22.1
4.6 ± 0.5
0.4 ± 0.2
1.0 ± 0.01
21.7 ± 9
1.5 ± 0.01
34.8 ± 9.9
6.9 ± 1.9
Min
165
4.1
0.2
1
20
1
15
3.3
Max
210
5
0.5
3
23
3
50
11.9
Total
Mean ± Std
302.1 ± 36
3.9 ± 1.6
0.4 ± 0.04
2.4 ± 0.62
19.2 ± 3.8
1.3 ± 0.8
32.4 ± 4.9
10.3 ± 2.6
Min
18
0.4
0.2
1
1
1
1
1.1
Max
1490
6.2
1.4
25
45
14
212
28
Highest values of CO were recorded during the year 2010, with an average release of 419.5 ppb. The non-significant change in the gas composition shows that the types of solid waste brought for incineration would have the same composition. However, the concentration of these gasses released into the environment was quite high. The particulate matters dispersed in the surrounding areas seemed to be associated with the incineration process, and had a similar trend of distribution over the sampling period.
According to world health organization, the over population and increased industrialization in south Asia, has made it one of the polluted regions, due to which, the emergency visits to the doctors are also increasing. Air pollution emerges from a variety of natural and anthropogenic activities. In either case, the pollution-exposed to the population is the most vulnerable group with imminent health risks. In the study area, as described in sampling site distribution, the exhaust emerging from the only available functional incinerator may be a factor contributing to the air pollution Table 2.
CO
R
P-value
CO
CO2
R
0.4
CO2
P-value
0.06
CxHx
R
0.51
0.16
CxHx
P-value
0.01
0.45
O2
R
−0.48
−0.98
−0.19
O2
P-value
0.02
<0.05
0.38
NO
R
0.37
0.82
−0.05
−0.84
NO
P-value
0.07
<0.05
0.83
<0.05
NO2
R
0.29
0.21
−0.02
−0.26
0.37
NO2
P-value
0.17
0.32
0.93
0.23
0.07
NOx
R
0.16
0.43
−0.08
−0.46
0.26
0.11
NOx
P-value
0.45
0.03
0.71
0.02
0.21
0.61
SO2
R
0.8
0.2
0.68
−0.26
0.2
−0.11
−0.08
SO2
P-value
<0.05
0.34
<0.05
0.23
0.34
0.61
0.70
H2S
R
0.57
0.21
0.49
−0.15
0.02
−0.18
−0.13
0.72
H2S
P-value
<0.05
0.34
0.01
0.47
0.93
0.41
0.53
<0.05
PM-S1
R
0.31
0.68
−0.06
−0.67
0.63
0.25
0.49
0.18
0.16
PM-S1
P-value
0.14
<0.05
0.77
<0.05
<0.05
0.23
0.02
0.41
0.46
PM-S2
R
0.23
0.73
0.28
−0.74
0.55
0.17
0.45
0.13
0.09
0.62
PM-S2
P-value
0.28
<0.05
0.19
<0.05
0.01
0.43
0.03
0.56
0.67
<0.05
PM-S3
R
0.26
0.43
−0.29
−0.43
0.61
0.3
0.34
0.1
−0.03
0.58
0.12
PM-S3
P-value
0.22
0.03
0.17
0.04
<0.05
0.16
0.1
0.64
0.87
<0.05
0.57
PM-S4
R
0.26
0.44
−0.3
−0.46
0.46
0.26
0.41
0.12
0.01
0.6
0.13
0.82
PM-S4
P-value
0.22
0.03
0.16
0.02
0.02
0.22
0.05
0.59
0.95
<0.05
0.54
<0.05
3.1 Major identified groups of gasses in exhaust
Principal component analysis (PCA) and cluster analysis revealed two distinct groups of pollutants in the FG. Both groups were almost constantly exhausted without any major changes in their concentration over the period of three years. The PC 1 accounted for 50.26% variability in the data set of pollutants alone. NOx, NO, and CO2 were clustered together, among which, CO2 and O2 (−0.94) had strong association with this component. NO and CO2 were more closely associated with each other, which showed their emergence from a similar source during the combustion process. Carbon and nitrogenous complexes are commonly present in biological samples. The incineration of biological samples from the hospital waste, and similar pathogenic sources may be an explanation of these gasses. PC 1 explained most of the variability of the data.
The second component (accounting form 27.7 percent data variability) comprised of CxHx (hydrocarbons) SO2 and CO, out of which SO2 dominated in its association with the component. The second component showed pollutant probably as a product of the combustion of the petroleum product. In this analysis NOx, NO and CO2 in the first component were a hazardous group of gases. Findings of PCA were in line with the cluster analysis; all of these groups were also seen in the cluster analysis (Fig. 1).
3.2 Distribution of particulate matter (PM10)
During the monitoring period, the presence of PM10 in the four selected areas was observed. With a minor variation, the large concentration of PM10 was probably related with the FG exhaust. However, contribution of other sources to PMs, cannot be ruled out. The data of PM10 recorded over the three years period are shown in Fig. 2. Except minor changes, the concentration of PM10 was elevated on most of the sampling sites. Results showed that during the year 2011, these values were high at the S3 site. Moreover, the PM10 concentration was slightly higher than the recommended USEPA limits for PM10 (i.e., 150 μg/m3) over the sampling period, on all four sampling sites (Fig. 2). These results indicate an underlying health risk for the local population. Most of these areas are under regular farming activities, it is possible that the spread of PM10 may also be a cause of food crops and drinking water contamination. An investigation on these lines is needed in future to focus on this particular aspect.
PM concentration at selected sites in the vicinity of incineration plant.
3.3 Public health implications
In Pakistan, following conditions are known to have a link with the exposure to PM: coughing, shortness of breath, asthma and other lung problems. These symptoms are recorded among individuals of all ages in dry and cold seasons. The human most frequently inhales PM10, and such exposures are more injurious for those, already suffering from some kind of heart and lung diseases (Ghauri et al., 2007). NO acts similar to CO and causes O2 binding failure with hemoglobin molecules, thus it can induce serious respiratory diseases, as it also promotes the formation of ground level O3 (EPA, 1999).
In the past both time series and cross sectional studies have been conducted to evaluate health effects of air pollution. These studies unveiled an increased rate of mortality and hospitalization associated with air pollution (Pope and Dockery, 2006). Nitrogen oxides (NOx) are formed when combustion takes place at a very high temperature. CO is most harmful for a cardiovascular patient. Other outcome of a long-term exposure to CO includes visual impairment, lack of learning, lethargy, and reduction in intellect (Air pollution control district, 2007). CO is a toxic gas; it is converted into CO2 after approximately one-month period (The Environmental Yellow Pages, 2010).
Investigating the exposure to suspended particulate matters (SPM), (NOx, CO, SO2) carries potential, because they are ubiquitously spread in the urban environment, and their high concentrations have already been observed in many cities (Ahmad et al., 2011). Air pollution affects both human health and environmental integrity. The PM10, is easily inhalable. PM10 is capable of causing inflammation of lungs, because they are penetrable into the thoracic region of the respiratory system in a human being (Dan Han, 2010). The issues related with public health can be resolved by adopting proper pollution mitigating strategies.
4 Conclusions and recommendations
Incineration is an important strategy to get rid of hazardous and infectious waste, still controlled release of exhaust gases can make incineration process a more beneficial practice. The above discussed incinerator is functioning to reduce most of the solid wastes generated from different sources, without which, there would have been many waste borne environmental and public health issues in the city. However, proper solid waste management is an important practice for a sustainable urban ecosystem. Waste management practices, must also be environment friendly. The point source of waste management, is veritably playing a progressive role in getting rid of the massive waste of the city. Still it may be a part of some environmental issues. Risk analysis, and mitigating strategies such as the use of FG treatment system, with ultra low dust emission, may be helpful in mitigating exhaust related hazards in future.
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