Ozone in ambient air at a tropical megacity, Delhi: characteristics, trends and cumulative ozone exposure indices |
| |
Authors: | Sachin D Ghude S L Jain B C Arya G Beig Y N Ahammed Arun Kumar B Tyagi |
| |
Institution: | (1) PMA Division, Indian Institute of Tropical Meteorology, Pune, 411008, India;(2) Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi, 100012, India;(3) Indian Institute of Technology, Kharagpur, CORAL Division, Kharagpur, -721302, W.B., India |
| |
Abstract: | Seven year data of hourly surface ozone concentration is analyzed to study diurnal cycle, trends, excess of ozone levels above
threshold value and cumulative ozone exposure indices at a tropical megacity, Delhi. The ozone levels clearly exhibit a diurnal
cycle, similar to what has been found in other urban places. A sharp increase in the ozone levels during forenoon and a sharp
decrease in the early afternoon can be observed. The average rate of increase in ozone concentration between 09 and 12 h has
been observed to be 7.1 ppb h−1. We find that the daily maximum and daytime 8-h (10–17 h) ozone levels are increasing at a rate of about 1.7 (± 0.7) and
1.3 (± 0.56) ppb y−1, respectively. The directives on ozone pollution in ambient air provided by United Nations Economic Commission for Europe
and World Health Organization for vegetation (AOT40) and human health protection were used to assess the air quality. The
present surface ozone levels in the city are high enough to exceed “Critical Levels” which are considered to be safe for human
health, vegetation and forest. The human health threshold was exceeded for up to ~45 days per year. The AOT40 (Accumulated
exposure Over a Threshold of 40 ppb) threshold was exceeded significantly during winter (D-J-F) and pre-monsoon (M-A-M) (Rabi
crop growing season) season in India. Translating AOT40 exceedances during pre-monsoon into relative yield loss we estimate
yield loss of 22.7%, 22.5%, 16.3% and 5.5% for wheat, cotton, soybean and rice, respectively. |
| |
Keywords: | Surface ozone Megacity air quality Ozone pollution Ozone trends AOT40 |
本文献已被 SpringerLink 等数据库收录! |
|