The rationale of this report is to present results of the Emissions Inventory conducted for Northern Arizona University’s (NAU) criteria pollutant emissions. The report shall be in terms of both the emissions trends for the university and the resulting impacts these emissions have on the surrounding environment and human health. Emissions data collected by Northern Arizona University Industrial Hygienist, Jim Biddle, was used to create a comprehensive report of nine years of emissions data for NAU over a thirteen year time span (1999-2012). No data was available for the years 2000, 2002, 2004, or 2006.
The four criteria pollutants that are measured by this emissions inventory are carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxides (SOx), and 10micron-sized particulate matter (PM 10). Jim Biddle did not include lead emissions in his reporting, so it cannot be included in this emissions inventory. Ozone is also not included because it is a secondary pollutant, meaning that it is formed in the atmosphere rather than being emitted into the atmosphere, and therefore cannot be quantified directly.
1.1 Discussion
1.2 Approach
The victory of the emissions inventory lies heavily in the approach used to systematize and present the vast amount of data into an understandable and quantitative design. Over the past three months a team of highly motivated individuals separated the emissions inventory into four tasks.
1.2.1 Establishing Significant Sources and Maximums
There are copious structures and sources on the NAU campus that emit the four criteria pollutants. To simplify the emissions inventory, significant sources were identified in the following manner. Within each emissions category, multiple buildings were identified and their campus zone determined as A, B, or C. The buildings were then grouped into the following categories: Steam Boilers, Hot Water Boilers, Heater, Paint Booth, Wet Cooling Towers, and Gas-Fired Kilns. After assembling the data and reviewing the emissions totals, it was determined that the Boilers and Wet Cooling Towers are the two significant sources. The heater, gas kilns, wood kilns, and the generators are combined as Combined Lesser Sources. The paint booth only emits VOCs which are not a criteria pollutant, so this source was ignored.
In order to establish maximum emissions values that will be used to model worst case scenario situations, temperature data for Flagstaff, Arizona was used. Average monthly temperatures, as graphically displayed in Figure 1.1.1-1, were used to make an analysis.
Figure 1.1.1-1: Average monthly High and Low Temperatures (°C) for Flagstaff, AZ
Because the boilers on campus were the source of heat in the winter and were found to be the major source of CO, NOx, and SOx pollutants, it was determined that the maximum emissions for these three pollutants occurs during the coldest month for which the campus is running at full operation, in February. Although January and December are colder than February, students are not present on campus for at least two weeks during each of these months, therefore reducing the use of the boilers.
The wet cooling towers, which are primarily used to release heat from air conditioning units on campus, are the major source of PM 10, so it was determined that the maximum emissions for this pollutant occurs during the warmest month, July. In addition to identifying the months, in which the maximums occur, the average monthly emissions were determined using the temperature data and the assumption that the boilers should operate more in winter and the wet cooling towers operate more in summer. Using percentages that equal 100% when summed for the twelve months, the annual emissions for each criteria pollutant were multiplied by a temperature-based factor, as shown in Table 1.1.1-1.
As shown in Table 1.1.1-1, monthly emissions factors were created for the criteria pollutants. These factors were applied to the annual emissions. The calculations and details of this method were presented in Task 2.
1.2.2 Conducting Dispersion Modeling
In order to determine the downwind concentrations for each of the four criteria pollutants, a modeling software program, SCREEN3, was used. The direction of the dispersion of these pollutants is based upon dominant wind directions for Flagstaff. The program allowed for NAU to be modeled as an area source. To simplify the dispersion models, this method was selected. Details on the modeling process were explained in Task 3 of this emissions inventory. However, the process is briefly reiterated here.
First, the pollutants for February were summed for each of the nine years of available data, providing a monthly February total. This total is composed of the maximum pollutant emissions for CO, NOx, and SOx, and the average monthly pollutant emissions for PM 10. Therefore, there are nine monthly February totals. Each of these totals was then multiplied by 12 to estimate what the worst case annual scenario would be based on a February emissions and dispersion model. Next, the pollutants for July were summed in the same manner, except that the maximum pollutant emissions for PM 10 and the average monthly pollutant emissions for CO, NOx, and SOx were used.
This provided a total of eighteen yearly estimates, nine estimates based on a July worst case model and nine based on a February worst case model. Theseeighteen yearly estimates were converted into the proper units to be used in Screen 3. Since the original units were tons/year, they were converted to lb/hr-ft2. This emissions rate is due to the choice to model the emissions as an area source, using the entire NAU campus as the area. The area for the NAU campus was determined to be 21,382,817.7ft2, based on measurements taken from Google Earth. Finally, two maximums were selected for modeling. Maximum total worst case scenarios for February modeling and July modeling were chosen from the nine years of data.
The February worst case scenario is based on the year 2010, with a total emissions rate of 2.82139 x 10-6 lb/hr-ft2. The July worst case scenario is based on the year 2011, with a total emissions rate of 1.52946 x 10-6 lb/hr-ft2. Along with the incorporation of the values from 2012, the results of these modeling scenarios were used to create pollution roses, which will assist in determining the impacts of NAU’s emissions. The assumptions used in each of the modeling runs can be viewed in Appendix 5.1.
2.0 Emissions Trends
Between the years 1999 and 2012, emissions for the criteria pollutants from the NAU campus have not been static. Rather, significant changes and trends can be seen. These emissions trends will be evaluated by comparing changes in emissions over the years.
Without studying the history of building construction and trends in student body population for the NAU campus, it is difficult to determine the reasons behind the increases and decreases in emissions over the years. In addition, it is possible that the methods used by NAU’s Jim Biddle to collect the emissions data differed over the years, thus resulting in variations in emissions data. Therefore, this trend analysis will focus solely on changes in emissions rather than the reasons why these changes occurred.
2.1 Trends for Criteria Pollutant Emissions for the Whole Campus
The data presented in Table 2.1-1 was used to create the graphs in Figures 2.1-1 and 2.1-2.
Figure 2.1-1: Graph Showing Change in Annual Criteria Pollutant Emissions from 1999-2011: CO, NOx, and PM 10.
Figure 2.1-2: Graph Showing Change in Annual Criteria Pollutant Emissions from 1999-2011: SOx
As shown in Figures 2.1-1 and 2.1-2, there have been significant changes in the emission rates of all four of the criteria pollutants for the total campus emissions from 1999 – 2011. A significant increase occurred between 2003 and 2005 for CO, NOx, and SOx. PM 10 saw a small increase between these years, as well.
- CO and NOx
CO and NOx follow the same trend. After 2005, they both decreased in 2007, but then increased between 2007 and 2010; whenboth reached their maximum emission rates. Then they both slightly decreased in 2011. Overall, it is difficult to say if CO and NOx will continue to decrease after 2011. However, their 2011 emission rates are significantly greater than when the inventory first began in 1999. CO emissions have increased tenfold, while NOx emissions have increased by a factor of three. This is an important and potentially alarming trend.
- SOxFrom 2007 onward, SOx has been on the rise. The maximum emission rate for SOx occurred in 2011. It appears that SOx will continue to increase. SOx have increased by a factor of 8.6 since the first emissions inventory in 1999.
2.2 Trends for Criteria Pollutant Emissions by Category Source
This data in table 2.2-2 was used to create the graphs in Figures 2.2-1 through 2.2-5.
Figure 2.2-1: Graph Showing Change in Annual Criteria Pollutant Emissions from Boilers from 1999-2011: CO, NOx, and PM 10.
Figure 2.2-2: Graph Showing Change in Annual Criteria Pollutant Emissions from 1999-2011: SOx
As shown in Figures 2.2-1 and 2.2-2, there have been changes in boiler emissions for all four criteria pollutants. Following the same pattern as emissions for all sources, the four criteria pollutants experience a large increase in emissions between 2003 and 2005.
- CO and NOxCO and NOx for boilers follow the same trend as CO and NOx for all sources combined.
- Sox
Between 2005 and 2007, SOxdecreased, but then rose again between 2007 and 2010 when it reached it’s maximum. It then decreased slightly in 2011. Despite this decrease in 2011, the SOx emissions in 2011 are four times greater than those in 1999.
Figure 2.2-3: Graph Showing Change in Annual Criteria Pollutant Emissions from Wet Cooling Towers from 1999-2011: PM 10
As shown in Figure 2.2-3, there have been changes in wet cooling tower emissions for PM 10. The wet cooling towers don’t produce any other pollutants. The PM 10 emissions were constant until 2005, increased between 2005 and 2007, and then declined between 2007 and 2009. However, since 2009, the PM 10 emissions have been on the rise again.
Figure 2.2-4: Graph Showing Change in Annual Criteria Pollutant Emissions from Combined Lesser Sources from 1999-2011: CO, NOx, and PM 10.
Figure 2.2-5: Graph Showing Change in Annual Criteria Pollutant Emissions from Combined Lesser Sources from 1999-2011: SOx
As shown in Figures 2.2-4 and 2.2-5, there have been changes in emissions for all four criteria pollutants from the combined lesser sources.
- CO The CO emissions remained relatively constant with one outlier year occurring in 2005, for which the emissions were seven times higher than the previous year. From 2007 onwards, CO has been increasing, with a slight decrease in 2011.
- NOxBetween 1999 and 2007, NOx emissions decreased. However, between 2009 and 2011, NOx emissions have been on the rise. The trend indicates that these emissions will continue to rise.
- SOxFrom 2005 onward, SOx has been increasing significantly for the combined lesser sources. This may be a cause for concern. The emissions in 2011 were 70 times greater than those of 1999.
2.3 Trends for Maximum Monthly Criteria Pollutants
As discussed in section 1.1.1, maximum monthly values were established for the criteria pollutants. The maximum monthly emissions for CO, NOx, and SOx occur in February whereas the maximum monthly emissions for PM 10 occur in July. Figures 2.3-1 through 2.3-3 depict the trends in the maximum monthly criteria pollutants.
Figure 2.3-1: Graph Showing Maximum Monthly Emissions for February: CO and NOx
As shown in Figure 2.3-1, the maximum monthly emissions for CO and NOx follow the same trend. Between 2003 and 2005, both criteria pollutants experienced a large increase in emissions. Between 2005 and 2007, the emissions slightly decreased. However, the emissions increased again between 2007 and 2010, but then slightly decreased in 2011. It is difficult to determine whether these maximum monthly emissions will increase or decrease in the following years. However, the maximum monthly amounts for February have increased significantly since 1999.
Figure 2.3-2: Graph Showing Maximum Monthly Emissions for February: SOx
As shown in Figure 2.3-2, the maximum monthly emissions for SOx appear to have an overall increasing trend. The maximum monthly emissions rate occurred in 2012 and is about thirteen times greater than the rate from 1999.
Figure 2.3-3: Graph Showing Maximum Monthly Emissions for July: PM 10
As shown in Figure 2.3-3, the maximum monthly emissions for PM 10 appear to have an increasing trend. Although the maximum monthly emissions remained constant for several years, they began increasing between 2005 and 2008. 2009 experienced a slight decrease in emissions, but an increasing trend is apparent between 2009 and 2011. It is likely the PM 10 maximum monthly emissions will increase in the following years as well.
3.0 Potential Impacts
The four criteria air pollutants generated by NAU have the potential to cause human and environmental health problems in the surrounding area. Meteorological trends, local geography, pollutant pathways, NAU emissions, and SCREEN3 modeling are used to help predict the areas in Flagstaff with the highest pollutant concentrations due to NAU emissions. In this section, the impacts caused by the emissions of CO, NOx, PM 10, and SOx on human and environmental health are presented. In addition, the impacts of the dispersion of these pollutants on the Flagstaff area will be addressed.
3.1 Health Concerns
The four criteria pollutants, CO, NOx, PM 10, and SOx, are regulated by the Clean Air Act which requires the U.S. Environmental Protection Agency to set National Ambient Air Quality Standards (NAAQS). These four pollutants are considered harmful to public and environmental health. CO has only primary standards, which are those that provide public health protection. NOx, PM 10, and SOx have both primary and secondary standards, which are those that provide public welfare protection, including protection against visibility changes and harm to animals, vegetation, buildings, or crops. The NAAQS are as follows:
Table3.1-1 NAAQS for CO, NO2, PM 10, and SO2
As a result of the SCREEN3 modeling runs conducted, maximum downwind annual concentrations for the four criteria pollutants were established. The maximum annual pollutant concentrations downwind from the NAU campus are summarized in Table 3.6-2. Conversions used to calculate these concentrations can be viewed in Appendix 5.2.
Comparing the maximum annual pollutant concentrations presented in Table 3.1-2, all four criteria pollutants emitted by NAU are in compliance with the NAAQS, and should therefore not be a cause for concern.
The maximum concentration for NO2, 3.06ppb per year, is far lower than the primary and secondary standard of 53ppb per year, which means that the amount of NO2 NAU emits is in compliance with the NAAQS. Comparing the CO maximum concentration of 0.00307ppm per year to the primary standard for CO, which is 9ppm, then NAU’s CO emissions are also in compliance. The maximum concentration for PM 10, 6.00µg/m3per year, is also far lower than the primary and secondary NAAQS of 150 µg/m3 over a 24 hour period. Finally, the maximum concentration for SO2, 0.015 ppb per year, is much less than the NAAQS primary standard of 75ppb over one hour and the secondary standard of 0.5ppm over 3 hours.
3.1.1 Human Health
Despite the fact that the criteria pollutant emissions from NAU are in compliance with the primary NAAQS, there may be a time in the future when these standards are exceeded. The following provides an analysis of the potential health impacts each of these pollutants could cause.
- CO: The harmful effects of CO include the reduction of oxygen delivery to organs such as the heart and brain, as well as body tissues due to a reduction in the oxygen-carrying capacity of the blood. People with heart disease would be more susceptible to experiencing complications, such as myocardial ischemia or angina while exercising or under stress. At extreme levels, CO can cause death.
- NOx: Short-term NOx exposure, between 30 minutes and 24 hours, is linked to respiratory problems such as airway inflammation in healthy individuals and increased respiratory trouble in people with asthma. Because NOx reacts with ammonia, moisture, and other compounds, small particles can form and penetrate deeply into the lungs, which can cause or worsen respiratory diseases like emphysema and bronchitis or intensify preexisting heart diseases.NOx can also interfere with defense mechanisms, causing people to be more susceptible to infections and disease.
d. SOx: Short-term exposure to SOx, ranging from 5 minutes to 24 hours, has been linked to several respiratory problems such as bronchoconstrictions and aggravated asthma, especially when exercising. Because SOx can react with other atmospheric compounds, small particles can form that have the ability to penetrate deeply into the lungs. Similar to NOx, this can cause or worsen respiratory illnesses like emphysema or bronchitis, aggravate heart disease, and potentially lead to premature death.
