Research On The Spread Of Airborne Pollen And Its Relationship With Meteorological Elements In Nanjing From 2015 To 2016

The study of airborne pollen is an important part of pollen modern process research The modern process of pollenis the basis of Quaternary palynotogy analysis,which plays an important role in the interpretation and quantitative restoration of the stratum pollen.In this paper we used Burkard to collect the airborne pollen from January 1st 2015 to December 31st 2016,identified and counted the numbers under a microscope.Based on the data of meteorological elements during this period,the distribution of airborne pollen and its relationship with meteorological elements were investigated by using statistical methods.We mainly draw the following conclusions:(1)A total of 47 taxa were determined fram 2015 to 2016,including 30 belonged trees and shrubs,14 herbs and 3 ferns.There was a difference in the taxa of airborne pollen in this two years.The type of airborne pollen in 2015 was mainly herbaceous,while in 2016,the air pollen type was dominated by shrub plants.The main types of airborne pollen are Humulus,Pinus,Poaceae,Ranunculaceae,Morus,Quercus(D),Cruciferae,Cupressaceae,Pterocarya,Artemisia,Alnus,Chenopodiaceae,etc,which are common plant species in Nanjing.The daily average concentration of airborne pollen was 0.13 grain/m3 in 2015,and that of trees and shrubs was 0.03 grain/m3 while that of herbs was 0.09 grain/m3.The concentration in 2016 of this three indexes are 0.05 grain/m3,0.03 grain/m3 and 0.02 grain/m3,respectively.(2)The spread ofairborne pollen has distinctly seasonal difference.During the year,the airborne pollen concentration has two peaks in spring(April-may)and late summer(August-September).The poflen assemblage of spring was dominated by the shrub plants,such as Pinus,Morus,Quercus(D),Pterocarya,etc while late summer was dominated by the herbs like Humulus,Poaceae,Artemisia,etc.(3)There was a nonlinear correlation between air pollen concentration and meteorological elements.The pollen concentration of Quercus(D)and Ranunculaceae has significantly negative correlation with temperature while the pollen concentration of Poaceae has significant positive correlation with temperature.The nonlinear relationship between the rest of the pollen concentration and meteorological elements was weak.The pollen concentration tend to appear the peak when the temperature is below 26?,relative humidity from 60%to 80%,wind speed in 1-4.5 m/s and no rainfall or less rainfalL The main types of airborne poflen are directly affected by the wind direction.In addition,the concentration of airborne pollen was significantly negatively correlated with PM2.5?PM10?SO2?CO?NO2,and was positively correlated with the concentration of O3.(4)Comparing the peak time of airborne pollen concentration from 2013 to 2016,we can found that in addition to spring in 2015,the peak of airborne pollen concentration in spring and autumn of the rest of the year showed an early trend.The peak time of airborne pollen concentration in 2015 was unnormal,it was speculated that the normal concentration peak time should be between April 5th and 25th,2015.(5)The sudden increase of precipitation in Nanjing from 2015 to 2016 was affected by the 2015/2016 El Nino events,resulted in heavy precipitation in this two years and it was the main reason for the precipitous decline of the airborne pollen concentration in 2015-2016.