2010 April 27: SC: South Carolina AIR QUALITY
Air Quality is defined as a measurement of the pollutants in the air; a description of healthiness and safety of the atmosphere (Dictionary 2010). South Carolina’s forests play a major role in filtering the air of pollutants (in other words, ozone and particulate matter), but can act as a source of particulate matter when wildfires rage through them. Forestry practices such as prescribed burning can reduce these fuel loads, thereby reducing the negative effects of wildfires. The forests also respond positively to carefully planned and executed prescribed burning with improved growth as competition for sunlight, water and minerals is reduced.
Trees sequester atmospheric CO
2 through the process of photosynthesis. This sequestration exceeds the CO2 emissions generated by events such as forest harvests, land conversions, and fires. Methane from forest fires amount to about 5 percent of the total. Forest fires also produce about 1 percent of the total nitrous oxide emissions. Forest fires in this context include prescribed burns and wildfires (USFS 2007).
New housing developments often lead to increased levels of air pollutants. For example, as the population grows and industry moves in to meet the population’s needs, increased levels of air pollutants such as sulfur dioxide, nitrous oxide and mercury are emitted into the atmosphere. In South Carolina, attainment levels for sulfur dioxide and nitrous oxide are met due in large part to strict air quality regulations. Landscaping with trees around industrial sources of pollution can help filter such pollutants, thus reducing the negative impacts on air quality (Tommy Flynn, pers. comm., SC Department of Health and Environmental Control (DHEC), January 6, 2010).
Other sources of air pollutants include vehicles. However, with new emissions equipment and standards, the quantity of these pollutants has actually been decreasing. And, with active urban forestry programs where tree planting and arbor care are implemented, additional reductions in the pollutants released by vehicular emissions can be achieved.
Urban tree plantings can also play a significant role in energy conservation especially in metropolitan areas where population densities are greatest. Trees tend to decrease the temperatures around these heat sources, resulting in less ozone being produced.
DHEC monitors air health impairments, non-attainment areas
1, and inversions. York County is the only area within the state that currently has non-attainment issues (Tommy Flynn, pers. comm., DHEC, January 6, 2010).
South Carolina has an average of 2,791 wildfires per year that burn a total of approximately 20,000 acres. The Southern Wildfire Risk Assessment is being used along with SC Forestry Commission historical records to classify and identify those communities at-risk to support wildfire planning and protection efforts. At the state level, the assessment is being used to increase awareness of the fire problem in South Carolina and to help the public understand fire management issues (Andreu et al. 2008).
Prescribed burning is one forest management tool used by forest managers to help reduce the hazardous fuel buildups that often accumulate in the forestlands around South Carolina. By 114 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94
conducting prescribed burns, fuel buildups are reduced lessening the chance of a disastrous wildfire. Prescribed burns also burn less intensely, produce less particulate matter and, therefore; have less of an impact on the atmosphere than wildfires (Hessburg and Agee 2003
The South Carolina Smoke Management Guidelines provide for minimizing the impact of smoke from vegetative debris burning operations for forestry, agriculture, and wildlife purposes. To do this, the Guidelines define smoke sensitive areas, amounts of vegetative debris that may be burned, and atmospheric conditions suitable for burning this debris. The SC Forestry Commission is responsible for administering the Smoke Management Guidelines. In doing so the Commission consults with and coordinates activities with the National Weather Service and the South Carolina Department of Health and Environmental Control (DHEC-Air Quality Division) to ensure compliance with air quality standards as outlined in the Memorandum of Understanding (SCFC 2006).
Prescribed burns and wildfires are a source of ozone and smoke (particulates). These pollutants have the greatest impact on air quality. Human activities are the primary cause (98 percent) of wildfires in South Carolina with about 40-45 percent due to escaped debris burns. This cause alone accounts for approximately 1,300 wildfires burning 8,400 acres per annually. A reduction in the number and size of human-caused wildfires can help reduce the negative effects on air quality (SCFC 2010a).
In South Carolina, forest managers prescribe burn an average of 527,000 acres annually (FY05 – FY09) for wildlife, forestry, and agriculture purposes. These prescribed burns are managed so that they produce limited amounts of smoke as compared to wildfires. The state’s Smoke Management Guidelines limit the amount of burning which can take place depending on how well the smoke will be dispersed that day (SCFC 2006).
It is unusual for ozone problems to occur during the prescribed burning season (late winter through spring, but can be a problem with summer wildfires when ozone levels are higher. Ozone is created during the combustion of nitrous oxide. High summer temperatures combined with burning of forest fuels can result in elevated amounts of ozone. In the last five years ozone levels have decreased due in large part to tighter emissions controls on power plants and automobiles. The outlook is for continued improvement even though new and more stringent standards will be implemented by the EPA sometime in 2010.
Figure xx: Concentration of Ozone
Particulate Matter, (PM 2.5) is measured in micrograms and since 2003 has been decreasing. This decrease in atmospheric particulate matter, especially over the last couple of years, may also be due in part to the downturn in the economy. (Tommy Flynn, pers. comm., DHEC, January 6, 2010). However, data is limited as there are only a dozen air quality stations statewide.
Figure xx: Concentration of Particulate Matter
Contributing to the amount of ozone produced are approximately 320,000 yard debris burns, as well as burns associated with the clearing of land for development and the maintenance and installation of highway rights-of-way. These burns are not regulated by the Smoke Management Guidelines, but are restricted by DHEC Regulation 61-62.2 – Prohibition of Outdoor Burning (SCFC 2006). 117 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148
When prescribed burning is conducted in the wildland –urban interface (WUI), the smoke that is produced can sometimes inconvenience people, and it can also cause serious health and safety problems. The public is unlikely to continue to tolerate the use of prescribed fire, regardless of the benefits, if burn managers cannot keep smoke out of smoke –sensitive areas (Wade et al. 2007, p.i).
Negative public reaction to smoke generated by prescribed and debris burns can lead to the passage of ordinances such as county–wide burn bans. Such burn bans may not consider the positive effects of prescribed burning. Therefore, they should be carefully scrutinized to ensure that forestry, wildlife and agriculture burns are exempt from such ordinances. The SC Forestry Commission’s continued collaboration with DHEC will keep the forestry, wildlife and agriculture burns in mind as regulations affecting air quality are pursued.
The SC Forestry Commission’s urban and community forestry grants provide opportunities for communities to address the care of urban forests and plan for green space to help offset the negative impacts of urban developments on air quality. For example, these grants provide funds for maintenance of the urban trees which absorb significant amounts of air pollutants and reduce surface temperatures. Refer to the chapter on community forests in South Carolina for additional information.
Literature Cited and References
Andreu, A. and L.A. Annie Hermansen-Baez. 2008. Fire in the South 2: The Southern Wildfire Risk Assessment. Southern Group of State Foresters. Available on line at http://www.southernwildfirerisk.com/reports/FireInTheSouth2.pdf.
Dictionary.com, LLC copyright 2010. Definition of air quality is available online at http://dictionary.reference.com
Hessburg, Paul F. and James K. Agee. 2003.
An environmental narrative of Inland Northwest United States forests, 1800-2000. Forest Ecology and Management 178: 23-59.
South Carolina Forestry Commission (SCFC). 2010. Available online at http://www.state.sc.us/forest/bweather.htm
South Carolina Forestry Commission (SCFC) Annual Reports. 2010a. Available online at http://www.state.sc.us/forest/ar.htm
South Carolina Forestry Commission (SCFC). 2010b.
Benefits of urban trees. Available online at http://www.state.sc.us/forest/urbben.htm South Carolina Forestry Commission (SCFC). 2006. Smoke management guidelines for vegetative debris burning operation in the state of South Carolina. Publication includes the Memorandum of Understanding between DHEC and the Forestry Commission (p.14), DHEC Regulation 61-62.2 (p.15), and the Air Stagnation Advisory and Ozone Alert (p.5). Available online at http://www.state.sc.us/forest/smg05.pdf118