High ozone at coastal sites in India

摘要

We present the field measurements of surface ozone (O3) made across the coast in five locations at three stations Poombuhar(l 1.14° N, 79.9° E), Tranquebar (11° N, 79.9° E) and TR Pattinam (10.46° N, 79.9° E) along the west coast of the Bay of Bengal, India in December 2000 and 2002 and in April 2001 and 2003. Measurements show a higher concentration of surface O_3 up to 4.0-6.9 parts per billion by volume (ppbv) at the coastline as compared to the concentration of surface O_3 at a distance 20 km inland. The higher coastline O_3 concentration is attributed to the short-lived chlorine species with a lifetime of less than 10 minutes generated from the chemical reaction of sea salt particles. Mean O_3 concentration decreases inland with distance from the coastline. Furthermore, the greatest difference between the coastline surface O_3 concentration and O_3 concentration 20 km inland was 4.8-6.4 ppbv, observed at 10 h in the morning, which is related to the morning peak of chlorine molecule (CI2) concentration. Measurements of nitrogen dioxide (NO_2) show concentrations between 4 and 10 ppbv, which are substantially higher than the critical limit of surface O_3 production.