Surface ozone concentration differences between urban and rural sites across US metropolitan areas and NDVI responses, 2000-2013
Surface ozone concentration is closely related with vegetation growth and human health. Surface ozone differences between urban and rural sites have been widely reported in environmental sciences (Stasiuk Jr and Coffey 1974, Kulkarni, Bortoli et al. 2013, Paoletti, De Marco et al. 2014). However, less attention has been paid to this phenomenon in urban ecological studies. Extensive research has determined the impact of ozone on plants (Wullschleger, Hanson et al. 1996, Chappelka and Samuelson 1998) but it is still controversial as to the relative impact of temperature and ozone on plant growth in urban and rural sites (Gregg, Jones et al. 2003, Searle, Turnbull et al. 2012).
In this study, we used US EPA surface ozone data to create a map of ozone distribution throughout the US. NASA Modis NDVI data and NOAA climate data were also used in multiple regression analyses to determine the relative impacts of ozone and temperature across large spatial scales and for specific urban – rural comparisons from 2000 to 2013.
The inverse distance weighted ozone map of the US showed holes of lower cumulative ozone exposures in all big metropolitan areas, e.g. New York City (NYC), Baltimore, Los Angeles etc. Initial analyses of two urban and four rural sites in the vicinity of NYC show that August NDVI was significantly negatively related to cumulative ozone exposures (May - Sept AOT40; P = 0.01) and there was no relationship with temperature whether summarized as the May – Sept. average, Tmin or Tmax. These results do not negate the importance of temperature for regulating plant growth, but point toward the need to continue to understand the detrimental impacts cumulative ozone exposures that are much higher in rural environments.