The concentrations of PM₁₀ within the 70 m height range at the South Second Ring of Xi'an were monitored for 4 days and nights in May 2013 by a microcomputer laser dust monitor. The results show that PM₁₀ concentration varied in 5 phases of the day.The first phase was at am 8:00-10:00, with an average concentration of 0.056 mg/m³. The second was at 12:00-14:00, with an average concentration of 0.075 mg/m³. The third was at pm 16:00-18:00, with an average concentration of 0.058 mg/m³. The fourth was at 20:00-22:00, with an average concentration of 0.070 mg/m³. The fifth one was in the night of 0:00-6:00, with an average concentration of 0.038 mg/m³. High resolution vertical observations indicate that Xian vertical variation of PM₁₀ concentrations can be divided into three types in May. The first type decreases as altitude increases PM₁₀ concentration increases was middle, the average increase rate for 0.048 μg/m. The second type as the altitude increases PM₁₀ concentration was the highest increase rate for 0.065 μg/m and volatile changes significantly. The third type as the height increases PM₁₀ concentration was the lowest and the increase rate for 0.013 μg/m. At the height of 70 m the mass concentration of PM₁₀ was the highest, the mean value being 0.56 mg/m³; the concentration at 1m height was the lowest, the average concentration being 0.048 mg/m³. In the range of 4-46 m height, the PM₁₀ mass concentration was the second lowest, with an average concentration of 0.051 mg/m³. In the scope of 49-67 m, the PM₁₀ mass concentration was the second highest, with an average concentration of 0.052 mg/m³, which presented a remarkable increasing trend. During the observation period, the mass PM₁₀ concentration and the temperature had a marked positive correlation at the height of 4 m (Correlation formula is y=240.73x +12.305). The mass PM₁₀ concentration and the humidity had a marked negative correlation at the heights of 4, 7, and 10 m (Correlation formula is y=-6.0668x+0.821).

PM₁₀ mass concentrations  /  phase change  /  vertical variation  /  South Second Ring of Xi'an