关键词: 黄瓜, 超微结构, 光合作用, CO₂加富, 水氮耦合

Abstract: Taking Heliekou Leisure Square in Wuxi City as an object, the diurnal concentration variation of atmospheric particulate matters with four diameters in street greenbelts were measured under typical weather conditions in spring. Meanwhile, the influence factors including micro-meteorological factors and traffic flow were also observed. The results indicated that: (1) The daily mean concentrations of TSP, PM₁₀, PM_2.5 and PM₁ in street greenbelts under different weather conditions were in order of sunny < cloudy < overcast. The particulate matter concentrations of the four diameters on overcast days were significantly higher than on cloudy and sunny days, and the concentrations of PM_2.5 and PM₁ on cloudy days were significantly higher than on sunny days. The increment percentages of PM_2.5 and PM₁ on cloudy and overcast days were far higher than that of the TSP and PM₁₀. (2) During the observation period, atmospheric particulate matter showed obvious diurnal variation under different weather conditions. It was consistent on sunny and cloudy days. Particulate matter concentration of the four diameters all presented one peak at 7:00 and one valley at 13:00-15:00, and it was higher in morning than in afternoon. On overcast days, it showed an increasing trend with time advancing for the four diameters. Daily variation of ratios of finer particles and atmospheric particulate matter concentration was consistent on sunny days, while that of both cloudy and overcast days was contrary. (3) The particulate matter concentrations all exceeded the secondclass concentration limits of China’s National Ambient Air Quality Standards except PM_2.5 concentration on sunny days. (4) 2.5-10 μm particle was the main pollutant on sunny days, being on a slight pollution level, while TSP, PM₁₀ and PM_2.5 were the main pollutants on cloudy and overcast days, being on a serious pollution. TSP pollution was mainly consisted of particle size <10 μm, PM₁₀ mainly of particle size <2.5 μm, PM_2.5 mainly of 1-2.5 μm. (5) Air relative humidity was the most important factor under humid environment in the studied region. On sunny days, the particulate matter concentrations of the four diameters were significantly negatively correlated with wind speed, air temperature, and light intensity, and significantly positively correlated with relative humidity and traffic flow. On cloudy days, they were significantly positively correlated with relative humidity, but significantly negatively correlated with relative humidity on overcast days.

Key words: cucumber, CO₂ enrichment, water-nitrogen coupling, ultrastructure, photosynthesis