Research On Composition And Release Regularities Of VOCs From Main Landscape Plants In Xi’an

This paper took ten main landscape plants in Xi’an which included five coniferous tree species and five broadleaf tree species as studying objects. The VOCs of ten landscape trees were collected by dynamic headspace air-circulation method,then the constituents and relative contents were identified with the gas chromatography-mass spectrometer technique(GC-MS),then calculated and compared the composition and content of VOCs in different tree species.Based on this,this paper studied the seasonal variation of VOCs from Pinus tabuliformis and Sophora japonica and diurnal variation of VOCs from Pinus tabuliformis in summer.Physiological characteristics of the trees and meteorological factors were also measured to reveal the factors of VOCs released.Finally,the influence of trees volatiles on consisting of air quality was analyzed.The results of this study provided theoretical basis for landscape application and exploitation of plant resources in Northwest China.The main results showed as follows:1.Five coniferous trees emitted 70 kinds of VOCs which contained 8 categories.Pinus bungeana emitted 32 kinds of VOCs which contained 8 categories,while the kinds of VOCs of the other four trees were 38(8 categories),29(6 categories),19(7 categories) and 36(8 categories).Terpenes,alcohols,ketones,aldehydes,alkanes and aromatics were all found in VOCs of the five coniferous tree species in which the relative contents of their terpenes were more than 70%. The five broadleaf trees emitted 51 kinds of VOCs which contained 8 categories.Sophora japonica emitted 31 kinds of VOCs which contained 8 categories,while the kinds of VOCs of the other four broadleaf trees were 36(8 categories),23(7 categories),25(8 categories) and 17(7 categories).Terpenes,alcohols,ketones,aldehydes,esters,alkanes and aromatics were all found in VOCs of the five broadleaf tree species in which the relative contents of terpenes were the biggest.2.The total volatiles concentration(TVOC) of Pinus tabuliformis and Sophora japonica varied with different seasons.The highest TVOC of Pinus tabuliformis was 98.13% for the summer,followed by autumn and spring,which TVOC was 54.75% and 44.93%,respectively. TVOC in winter was 37.14%,which was the lowest.The highest TVOC of Sophora japonica was 87.82% for the summer, followed by autumn and spring,which TVOC was 73.87% and 54.90%,respectively. TVOC in winter was 43.12%,which was the lowest.There were 77 kinds of VOCs in amount within a year of VOCs from Pinus tabuliformis,there were 13, 44, 31 and 34 kinds of compounds in four seasons.The main components of Pinus tabuliformis were terpenes and aromatics.There were 57 kinds of VOCs in amount within a year of VOCs from Sophora japonica,there were 31,23,36 and 31 kinds of compounds in four seasons.The main components of Sophora japonica were terpenes.3.There were 62 kinds of VOCs belonging to 8 categories in amount in Pinus tabuliformis of a summer day,in which terpenes beneficial to human health were the main VOCs.The diurnal variation curve of total volatile organic compounds(TVOC) appeared as“two peaks and three vales”,the peaks were at 13:00 and 16:00 while 8:30,14:30 and 17:30 were the vales.The content of healthful terpenes in the afternoon was higher than that in the morning,and harmful aromatic compounds emitted at 8:30-10:00 and 13:00-14:30 when the contents were still low.The TVOC concentrations of Pinus tabuliformis would be high when temperature was high,illumination was strong and humidity was low, conversely, it would be low.The diurnal variation of TVOC concentrations accorded with net photosynthetic rate,stomatal conductance and transpiration rate.The correlation between the concentrations of TVOC and meteorological factors was not significant,it showed a significant correlation between TVOC and stomatal conductance,a very significant correlation between TVOC and net photosynthetic rate as well as transpiration rate.4.49 kinds of VOCs was detected in campus atmosphere which contained 7 categories.In four sampling points we detected 30,28,24 and 29 kinds of compounds,respectively.The main component were terpenes,esters,aromatics and alcohols.The study showed that the content of terpenes which is good to human health was raised with the increasing amount of vegetation while the content of aromatics which is harmful to human health was reduced.Results showed that trees can play a role in purifying the air by releasing volatiles to change the composition of the air.