Abstract
Investigations of air pollutants were conducted aboard a research vessel anchoring for several hours at several sites while cruising over Osaka Bay and the surrounding sea area in Japan. The concentrations of nitrogen oxides (NOx) within Osaka Bay sometimes exceeded 60 ppb (parts per billion by volume) and showed a clear diurnal variation pattern with a broad peak in the daytime. A similarity was observed between the variation patterns of NOx concentration and sea traffic on the bay. Outside the bay, NOx concentration was constant at about 13 ppb. Atmospheric monitoring from the rooftop of a skyscraper on the coast often showed high levels of NOx in air masses from Osaka Bay, seemingly affected by ship emissions. On the other hand, low NOx concentrations (< 5 ppb), which never appeared in the air masses from the urban area, were also often observed. The effects of NOx emissions from ships on inland air quality thus seem to vary widely depending on the density of sea traffic on the bay.
Highlights
Atmospheric oxides of nitrogen have been recognized as principal pollutants since the early history of industrialized countries (Seinfeld 1975)
Tively high nitrogen oxides (NOx) concentrations were observed at a site outside the bay (St_H)
During the high NOx concentration episode, which lasted from 0:00 to 17:00 JST, under stagnant weather conditions, research vessel (R/V) Shirafuji-maru anchored at two sites, St23 and St26
Summary
Atmospheric oxides of nitrogen have been recognized as principal pollutants since the early history of industrialized countries (Seinfeld 1975). Because many large cities face the sea and have ports, ship emissions would affect the air quality of these coastal sites (Isakson et al 2001; Saxe and Larsen 2004). From the results of this investigation, we discuss features of the temporal variation and spatial distribution of air pollutants, especially NOx. In addition to the on-board investigations, we conducted atmospheric monitoring from the rooftop of a 250-m-high skyscraper standing on the coast of Osaka Bay. In addition to the on-board investigations, we conducted atmospheric monitoring from the rooftop of a 250-m-high skyscraper standing on the coast of Osaka Bay Using this dataset, we present a preliminary study on the effect of ship emissions on the quality of inland air
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