Surface ozone: A likely threat to crops in Yangtze delta of China

Observational surface ozone during a 16-month field experiment between 1999 and 2000 at six non-urban sites in the Yangtze Delta of China suggests that enhanced ozone concentrations were most prevalent during the spring, when the 90-day ozone-exposure indices SUM06, AOT40 and 7-h-daytime mean ranged from 27 to 43 ppmh (parts per million-hour), 17 to 27 ppmh, and 56 to 63 ppbv (parts per billion by volume), respectively. These observations, along with dose–response relationships derived from ozone-effects research carried out on crops in the United States and Europe, suggest that the yields of winter wheat grown in the Yangtze Delta in 1999 and 2000 were likely reduced by about 20–30% as a result of damage caused by exposure to ambient ozone.