Evaluation of Nitrogen Oxides Pollution in Takamatsu and Utazu Area in Kagawa Prefecture, Japan

Abstract

We evaluate nitrogen oxides pollution in Takamatsu and Utazu area in Kagawa prefecture, Japan. Annually observations for nitrogen oxides (nitrogen dioxide; NO 2 , nitric oxide; NO) (1990-2007) were obtained from data base of Ka-gawa prefecture, Japan. Changes in NO 2 and NO in Takamatsu and Utazu area were evaluated and compared. In 2007, NO 2 , NO and NO 2 + NO (ppm) in Takamatsu area were higher than those in Utazu area. However, NO 2 /(NO + NO 2) in Takamatsu area was lower than that in Utazu area. From 1990 to 2007, mean of NO 2 in a day over the level of 0.06 ppm was 30 days in Takamatsu area and only one day in Utazu area. Mean of NO 2 , NO and NO 2 + NO was significantly higher and NO 2 /(NO + NO 2)was lower in Takamatsu area than that in Utazu area. In addition, NO 2 , NO and NO 2 + NO were negatively correlated and NO 2 /(NO + NO 2) was positively correlated with years (1990-2007) in Ta-kamatsu area. The level of nitrogen oxides pollution in Utazu area was lower than Takamatsu area. Further observation is required for preventing nitrogen oxides pollution in Kagawa prefecture, Japan.