Human activities and urban air pollution in Chinese mega city: An insight of ozone weekend effect in Beijing

Ozone pollution has become a major environmental concern in China, especially in mega cities with intensified human activities, which can impact air quality and human health. This study explores the different characteristics of ozone and ozone weekend effect (OWE) in different seasons in places (e.g. urban center, inner urban areas, suburban areas and natural background areas) with different degree of urbanization and intensity of human activities and the effect of urbanization on ozone at different scales in Beijing. The annual daily average ozone concentration in Beijing was 56 mu g/m(3), with the maximum of 98.0 mu g/m(3) occurred in summer and the minimum of 27 mu g/m(3) in winter. Spatially, annual daily average ozone concentration increased along the urban-rural gradient. The annual ozone concentration was 6% higher at weekend than that on weekdays. Seasonally, the ozone concentration on weekend was 18% higher than that on workdays in summer, 4% in autumn, and 10% in winter, but was 10% lower in spring, indicating that the ozone production regime in different seasons could be different. Influence of urbanization on OWE varied by scale. At the city scale, OWE was more pronounced in urban centers than suburban areas, but at the local scale, OWE tended to decrease with the increase degree of urbanization.