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Airborne pollutant characteristics, potential sources, and variation trends of cause are investigated based on the hourly air concentrations of gaseous pollutants and particulate matter from 2013 to 2016 in Lanzhou. The mean concentration of SO, NO, CO, 8-hO, PM, and PM was 25.2 ± 16.0 μg m, 46.5 ± 21.1 μg m, 1.3 ± 0.7 mg m, 77.8 ± 45.5 μg m, 58.7 ± 32.9 μg m, and 131.1 ± 86.2 μg m, respectively. The concentrations of SO, PM, and PM present decreasing trends while NO, CO, and O present increasing trends. PM is the most frequent major pollutants with much higher value than standard limit. However, NO pollution had obvious trends to reach the limit and was more serious in Lanzhou compared with other Chinese cities. Relationship between air pollutants and meteorological parameters suggested that lower primary pollutants were associated with higher wind speed from north and west. Modeled back trajectory demonstrated that the transport of air masses from the Hexi Corridor and Inner Mongolia was responsible for the high concentrations of the air pollutants in wintertime, and high PM level in springtime was related to long-range transport of dust from desert areas of the Sinkiang and the Central Asia. Effects of local pollutant emissions and meteorological condition were preliminary analyzed. Improvement of air quality might be related to the decreasing of pollutant emissions due to strict emissions controls, and the contribution of meteorological condition was not explicit and should be further investigated.

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This paper is devoted to establishing the long-time behavior of extensible beam equation with the nonlocal weak damping on a bounded smooth domain of Rn with hinged (clamped) boundary condition. It proves the well-posedness by means of the monotone operator theory and the existence of a global attractor when the growth exponent of the nonlinearity f(u) is up to the critical case in natural energy space.