Research On Urban Street Greening Based On Pollen Sensitization Control

As an important part of the urban ecosystem,urban street green space plays an important role in beautifying the environment,improving microclimate,alleviating heat island effect,reducing dust and noise,etc.,but at the same time,pollen allergy is also a negative impact.At present,pollen allergy has been listed by the World Health Organization as one of the three key diseases to prevent and control,and has become a seasonal epidemic with high incidence.Therefore,in the planning and design of urban street greening,plant sensitization should be considered,the generation,spread and harm of sensitized pollen should be controlled from the source,and the concept of "health" should be integrated into urban greening construction.In order to grasp the current situation of pollen sensitization of urban street green space,this paper selected street green space in three different construction periods in Xi ’an city as the research object.It was found that the common allergenic plants in Xi’an streets were mainly trees,and the allergenic plants in Beilin district,which was built earlier,were mainly sycamphus,with strong sensitization,large planting amount and single green layout.The sensitized tree species in the high-tech zone,which was established in 1991,were mainly koelreuteria koelreuteria and conifer.The sensitized plants in Qujiang New District,which was established in 2002,are mainly sophora acacia and koelreuteria,with the largest number of sensitized plants and rich species.The types of allergenic plants,the distribution of allergenic plants,the sensitization value and the influence of air flow on pollen distribution in each street were comprehensively analyzed,and the maximum allowable content of allergenic plants in the spatial layout of urban street green space was obtained under different species richness.According to the effect of air flow on pollen dispersal in street space,it is concluded that when the wind direction is close to the vertical street direction,the position of medium and small trees should be controlled to facilitate the pollen being swept away by the air flow and the residual pollen retention;when the wind direction is close to the parallel street direction,the underwood space of trees should be dealt with.Three results are obtained in this paper: first,more detailed exploration is carried out in the direction of controlling the use of allergenic plants,and the calculation method of street space green space allergenic calculation is simplified;Secondly,according to the characteristics of the dominant wind direction in Xi ’an,two types of streets and their cross section greening arrangement are proposed according to the law of pollen drift.Eight types of street greening structure models are obtained through combination.Third,the study finds that the street green space with high sensitization risk is the research object,and puts forward the design scheme or optimization suggestion to reduce the street sensitization risk through reasonable planning of green space.