Table 6.

Total estimated pollution removal (kg yr–1) and associated monetary value (dollars yr–1) for 879 street trees in Iowa during nonprecipitation periods (dry deposition) in 2000. Monetary value of pollution removal by trees was estimated using the median externality values for the United States for each pollutant (Murray et al. 1994). Externality values for ozone were set to equal the value for NO2.

PollutantRemoval (kg yr–1)Value (US$ yr–1)
Particulate matter < 10 μz6.428.8
Nitrogen dioxidey2.516.7
Sulfur dioxide1.72.8
Carbon monoxide0.40.4
  • zAssumes 50% re-suspension of particles.

  • yBecause there was no complete data set on nitrogen dioxide (NO2) concentrations in Iowa, estimates of NO2 removal by trees in Iowa were based on removal rates for trees in Omaha, Nebraska in 1994 (0.73 g/m2 of canopy cover). This estimate is reasonable due to geographical proximity of Omaha to Iowa; also, removal rates in Omaha were relatively low compared to data from other cities in the United States.