Based on a pair of black and white standard A-type evaporation pans set under the same meteorological conditions, the dynamic characteristics of meteorological elements, water temperature and evaporation of the two pans were observed. The influence of water temperature on the evaporation of the evaporation pan was explored based on the existing 6 evaporation models. The results showed that 1) the designed observation method can be used to study the effect of water temperature on the pan evaporation. The water temperature and evaporation rate between the two pans were significantly different. During the 50-day observation period, the average water temperature difference between the two pans was 0.4°C, and the average daily evaporation difference was 1.1 mm/d. 2) 1°C increase in water temperature difference between black and white pans will produce an evaporation difference of 0.808 mm/d under the same conditions of solar radiation and other meteorological elements. 3) Under the condition of rising water temperature, the estimated value of the classical evaporation model without considering the water temperature would be smaller than the actual observed value, and the error of the estimation will also increase correspondingly.

Through three-dimensional observation and numerical analysis of evapotranspiration characteristics and cool island response of individual urban trees, the cause of vegetation cold island effect was analyzed quantitatively. The results show that 1) the absolute value of cool island intensity in various parts of Ficus microcarpa was basically above 3.0°C, while at surface front (SF), the temperature difference could reach the maximum of ?5.19°C and surface top (ST) can reach to ?3.57°C. 2) The evapotranspiration rate of leaves in the east, SF and SR (surface right), was start to rise firstly, and the leaves in the west, SL (surface left) and SBa (surface back), have the highest evapotranspiration rate at noon while the leaves in the west (SL, SBa) reached the peak later. The transpiration of all parts at night was very weak, less 0.05 mm/h. 3) The overall cool island effect intensity were positively correlated with evapotranspiration rate (pearson correlation coefficient was 0.70, with a significance lower than 0.01). For every 1 mm/h increase in evapotranspiration, the temperature of the whole tree decreased by 3.56°C. Evapotranspiration of surface top contribute obviously to the cool island effect of surface top itself with a correlation coefficient ?0.61. Evapotranspiration of surface top, surface front and surface right have the largest contribution to cool island effect of the whole tree (correlation coefficient absolute value is greater than 0.60). Contribution order of different parts’ evapotranspiration to overall cool island effect is: SF>ST>SR>SL> SBa>SBo (surface bottom), that means east and top side>west side>bottom.

Taking six most common garden plants in Shenzhen were used as research objects, the amount of dust retention per unit leaf area and the particle size composition of dust were studied. The microscopic morphology and the structure of leaf surface as well as the composition and distribution characteristics of the retained particles were investigated. The influence of meteorological factors on the dust retention characteristics of plants was clarified. The results showed that: 1) The dust retention amount per unit leaf area of different plant types was Ficus microcarpa (0.74±0.21 g/m²) > Schefflera arboricola (0.42±0.26 g/m²) > Ficus hispida (0.24±0.26 g/m²) > Ixora chinensis (0.20±0.07 g/m²) > Ophiopogon bodinieri (0.18±0.10 g/m²) > Plumeria rubra (0.15±0.10 g/m²). 2) The six types of garden plants were mainly composed of particles with particle size α>10 μm. The weight of particles with size α>10 μm accounts for 59.21%~88.92% (except for F. microcarpa) of the total weight. S. arboricola had the strongest dust-retaining ability for particles with size α>10 μm (0.34±0.20 g/m²). F. microcarpa had the strongest dust-retaining ability for particles with size 3 μm<α<10 μm (0.51±0.15 g/m²) and 0.15 μm<α<3 μm (0.14±0.07 g/m²). 3) Stoma, fold, groove, flocculent protuberance and villi on the surface were conducive to the retention of dust. The main elements of the retained particles were O, Si and Al. 4) The large particles (α>10 μm) detained by the leaves of the six garden plants were susceptible to wind speed and temperature. The results of this study can be used to guide the arrangement of garden plants in Shenzhen and provide a scientific evidence for the plant dust retention effect to improve air quality.