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Regional Differences on Sources for Ozone and Particle Pollution
Region 6: Arkansas, Louisiana, Oklahoma, New Mexico, and Texas
Local Sources of VOCs
VOCs generated by human activity in this region include highway vehicles (32% compared with 29% nationally); off-highway vehicles (13% compared with 18% nationally); and solvents (20% regionally compared with a national rate of 27%). Region 6 had a higher rate of VOCs from petroleum and related products (10% regionally compared with 2% nationally), and storage and transport (9% regionally, compared with a national rate of 7%). This difference probably reflects the concentration of the petroleum industry in the region. Total VOCs inventoried in 1999 in Region 6 were 2.5 million short tons in 1999, the third highest.
Local Sources of NOx
Highway vehicles represented the largest source of NOx in this region at 27 percent, lower than national rate of 33 percent. The next highest source of NOx in the region is industrial fuel combustion, which, at 24 percent, is very high compared with the national percentage (12%). Off-highway vehicles produce 23 percent of NOx regionally, compared with 22 percent nationally. Electric utilities represented 18 percent regionally, compared with 23 percent nationally. Petroleum and related NOx, at 2 percent, is twice the national rate (1%), and probably reflects concentration of the petroleum industry in the region. Total NOx produced in Region 6 was 4.2 million tons in 1999 (the third highest region).
Local sources of Particle Pollution (PM2.5 )
Agriculture and forestry, and other combustion were the major sources of particle pollution in Region 6 (49%), only 2 percent above the national average for miscellaneous sources of particle pollution. Industrial fuel combustion (12%) was the second largest source of particle pollution emissions in the region. Other major sources of particle pollution in the region include off-highway vehicles (8%), and waste disposal and recycling (6%). Other fuel combustion, other industrial processes, and fuel combustion from electric utilities each contributed 5 percent of particle pollution in the region. Region 6 reported 571,036 short tons of particle pollution during the 1999 inventory.
Trends
Monitored ozone levels dropped by 11 percent between 1983 and 2002, a trend slightly behind the nation as a whole, which dropped 14 percent during the same period. Furthermore, the long-term decline could have been greater had not the region’s ozone levels increased by 8.9 percent from 1991-2000. Comparable trend data are not available for PM2.5 levels.
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