 The topic I'm going to present today is assessing the interaction between urban forest and the particular matter. The topic is also the basis of the detaining the potential opportunities and the existing challenges for using urban forest to achieve cleaner seating. I will elaborate on the topic from six aspects. We all know that with the acceleration of industrialization and urbanization, the increasing air pollution has received more and more social attention. Using urban forest as an air purification regulator to elevate the air pollution has received more and more focus in recent years. However, the interaction between urban forest and PM and its underlying mechanisms remains little known. To fill this knowledge gap, we first proposed a new classification of PM on plant leaves. The particular matter on leaves can be divided into two main categories. The first one is the PM embedded in the leaf wax layer. The other one is the PM on the leaf surface. This part can be further divided by different methods. The first method is to classify it into difficult to remove and easy to remove PM. The other method is to divide it into water-installable PM and the water-soluble in organic ends and the water-soluble organic matter. When we did this study, there was no good method to measure all of these types of PM accurately. Thus, we developed a novel plant PM return capacity evaluation method for this. This method was named AUSTONIC EWPA method. One of the key questions in this method is how to clean the particles on leaf surface completely. The traditional and commonly used method is to use water cleaning and brush cleaning. However, after observing the SEM image of this, we found it can't elute the particles completely. Therefore, we added the AUSTONIC CLEANING procedure to the traditional method and found that this additional procedure can wash off the particles completely. This also improved the evaluation accuracy of water-soluble PM and water-installable PM. We said another benefit of our new method is that it can lead to an accurate evaluation of the plant's retention of beta of wax-embedded PM. After updating the leaf cleaning procedure, we further proposed the procedure to measure easy-to-remove PM or on-gift surface. This part of PM can indicate the renewable PM retention of beta of plants under net conditions. Then we proposed another procedure to measure the difficult to remove PM. And this kind of PM can represent the difficulty of the renewable PM retention capacity. Although we can achieve an accurate estimation of these two parts, but it only indicates the beta of plants to capture water-installable particles. Consequently, we further developed two methods to measure the water-soluble components of PM. So, as the advantage and disadvantage of our method, we made a detailed comparison of our method with other similar methods and found the evaluation results of their methods differ greatly in terms of PM retention efficiency and its run-amount species. Among these methods, our approach can obtain the largest amount of information by its cost and the time requirement is the highest. Then we applied our methodology to investigate the PM retention, characterization characteristics, and the different conditions. The first study was conducted in Beijing. So, along air pollution, gradient with simple leaves of five species and the two periods, and the methods data to derive different evaluations in depth. We found that as a particle set distribution on leaf surface, change the market with increasing dust retention duration. And this variation was species specific and maybe dominately by the leaf microstructure and other external environment factors. As expected, all types of TSP on leaf surface increase greatly with increasing dust retention duration. As to different types of PM, the order in retention efficiency of different size PM among various species was different. This indicates that particle temp, damage class and assessment skill all should be considered for doing such kind of work. As to our study, trees in Sephora, Japonica showed the highest retention efficiency for PM 2.5 of TRP and CRP. And where Pino stablite formates had the ability to return light particles with the highest efficiency. The particle returned by the broad leaf and the needle leaf tree species were mainly composed of water soluble PM and the water insoluble PM respectively. The two PM parts have different size distribution which vary maximally with species and air pollution level. Relative to the water insoluble PM, the average relative capacity of different species in returning water soluble PM was more stable with temp. As expected, when using different evaluation indicators, we found the variation in each species retention capacity relative to that of other tree species was considerable. On the leaf surface of brother leaf species, we found the proportion of water soluble PM was the highest. On the contrary, the highest proportion was the order insoluble PM for coniferous species. We said conifers have higher proportion of wax embedded PM than broad leaf species. Our second study was also in Beijing, but it was within a small area around the two key three universities, and within folder the leaves of 27 species across three seasons for analysis. And we found the particle size distribution on plounder on leaf surface change maximally with season and the species. And the rank of different species in returning different types of PM also changes significantly with the season. Among different life forms, shrubs show the highest PM retention capacity and it's followed by trees and vans. It is generally believed that rougher leaf can have hair, can have stronger PM retention capacity. However, our data showed that the relationship between the surface roughness and the leaf of PM retention capacity is very weak. Except of evaluating the PM retention on small skills of leaf and the individual tree, we further assess the life skill effect of urban forest on elevating in particular matter. In the first case, the evaluation is on the max data scale. We use a different source of data and it was roughly estimated that the five trees species in the SCBD region could return 132 10 PM in total per day during study period. And it accounts for a large proportion of the delay after four months. In the second case, we did a similar evaluation but it was on a national scale. To achieve this, we simple the needle leaves in 13 provisional cities plus one big city in Tibet. Our data showed that the average PM load on needles in China was 554 milligram per gram meter but the PM load and the component preferred to the obvious special variation across the cities. And compared with South China, the PMR load in North China was generally higher. And consistent with our funding in Beijing, the water soluble components was the main part of the PMR in China. It also found that the dominant the water soluble ends on leaves were calcium end, potassium end, and the nitrate end. This indicates that red dust, biomass combustion and the traffic exhaust are significant sources of PM in China. Furthermore, we estimated that the annual amount of PMR on Zedros Theodora to be nearly 20 square kilometer square kilometer can be per year in China. In addition to understanding how urban trees affect the air pollution, we also concerned how air pollution influence the urban trees. Therefore, we selected one tree species and designed an experiment and get a two groups of leaves and then married the different kind of ecophysiological trees. And we found that increase PM on leaf surface should have no significant influence on most ecophysiological trees. But it could significantly increase the leaf submersible conductance. Based on these results, we derived the one-in-treating hypothesis that is PM pollution will increase the gas exchange rate of trees, but its effect on photosynthesis is higher, you hear than that on transpiration, subsequently leading to increase the water use efficiency. We all know urban trees and forests often receive daily management. This make us want to know whether forest cultivation measures can influence the PM retention of urban forests. However, contrary to our speculation, irrigation and coupling and propagation almost have no effect on the PM retention of plants. But the trees without irrigation and fertilization always had the lowest PM retention capacity value. Partly consistent with our speculation, the daily variation and the average concentration of PM 2.5 in the air was not affected by forest structure, but the PM retention amounts by unit standard area can be significantly affected. Besides, we found that the regulation affects our urban forests on PM concentration in the air included both increasing and decreasing effects. Okay, finally, I want to make a summary. The urban forests, urban trees play a significant role in marketing heat pollution in China, but it may be not feasible to use a load of PM on leaves to indicate the heat in the air, heat level in air. PM pollution may affect the water relations of urban forests, which need more detailed investigation in the context of increasing frequency and the intensity of global drought. Finally, the recovery measures may improve the air purification capacity of urban forests, but the more related works are needed for verifying this and the developing high-efficient measures. Okay, that's all, thank you.