The Response Of BVOC Emission And Its Ozone Formation Potential To Temperature And Light Of Garden Plants In Fuzhou

In order to reduce the damage of urbanization to the urban ecological environment,the planting area of garden plants in the city is increasing day by day.However,the potential negative effects of garden plants have not yet received sufficient attention.Garden plants will release a large number of biogenic volatile organic compounds（BVOCs）,and the emission rates vary from plant to plant.BVOCs have a strong activity and once they enter into the atmosphere,it has a great impact on the atmospheric environment.On the one hand,nitrogen oxides（NOx）enter the urban atmosphere through vehicle exhaust,etc.,and nitrogen oxides in the urban atmosphere will react with BVOCs with the catalyst of suspended particulate matter under light conditions.The reaction will eventually produce near-surface ozone.On the other hand,temperature and light intensity are two important factors in urban ecosystems,which have a great impact on the release of plant BVOCs.Therefore,the production of ozone in the near-surface of the city has been aggravated,thus affecting human health.Basing on the analysis of BVOC emission rates of 17 city common garden plants,six garden plants which released main BVOCs largely（isoprene-released species:Loropetalum chinense and Nandina domestica;monoterpene-released species:Fagraea ceilanica,Photinia frasry Dress,Jasmine and Schefflera octophylla）were selected in this study.Different temperatures（25 ^OC and 30 ^OC,35 ^OC and 40 ^OC）and photosynthetically active radiation(PAR:0,500,1000,1500μmol·m^-2·s^-1)were simulated to study the emission rates of isoprene and monoterpenes from different plants.Their ozone formation potential（OFP）of the BVOCs and their response to temperature and PAR were also investigated.The results were as follows:1)L.chinense and N.domestica are high isoprene-released species,under the condition of light,isoprene emission accounted for more than99.8%.The amount of monoterpene released by F.ceilanica,P.frasry Dress,Jasmine and S.octophylla was more than 60.7%.As temperatures rised,L.chinense and N.domestica released of isoprene,S.octophylla released of monoterpenes growing exponentially,and highest at 35 ^oC,（8436.48±2322.94）,（15138.81±3038.18）and（8.62±1.16）pmol·m^-2·s^-1,respectively.F.ceilanica（γ-pinene）,P.frasry（β-pinene,limonene,3-carene）and Jasmine（α-pinene,limonene）also showed an increase trend with the increase of temperature.2)As light increases,isoprene in L.chinense and N.domestica to release a quantity to rise gradually,and highest at 1000μmol·m^-2·s^-1,（7355.17±1662.35）and（3279.21±1178.23）pmol·m^-2·s^-1,respectively.In terms of monoterpenes,the release amount of F.ceilanica and P.frasry rised first and then decreased,and the maximum were（42.97±11.10）and（18.62±2.52）pmol·m^-2·s^-1 at 500μmol·m^-2·s^-1.The release of Jasmine and S.octophylla gradually decreased.3)The effects of temperature and light on BVOCs emission are mutually reinforcing.Under the condition of high temperature,with the increase of light,the release amount of BVOCs shows an overall trend of increase.Under strong illumination,the change of BVOC emission is similar with the increase of temperature.The amount of isoprene and monoterpenes released by F.ceilanica was highest at 40 ^oC×1500μmol·m^-2·s^-1,reaching to（64.53±33.09）and（138.21±11.02）pmol·m^-2·s^-1,respectively.The release of isoprene was the largest when 30 ^oC×1500μmol·m^-2·s^-1（30.99±18.13）,and the release of monoterpene was highest at the condition of 40 ^oC×1500μmol·m^-2·s^-1,with the emission of（1206.25±249.09）pmol·m^-2·s^-1.4)With the increase of temperature,the contribution of plants to OFP gradually increases;enhanced with illumination,L.chinense and N.domestica and F.ceilanica rised gradually,the contribution of the Jasmine and S.octophylla decreased gradually.There was no significant change in the contribution of P.frasry under different temperature and light conditions.L.chinense and N.domestica are high isoprene-released and therefore high-OFP species,especially under the condition of high temperature and strong light（with the OFP of canopy reaching 18161.98ppb and 10527.15 ppb respectively）.Isoprene,α-pinene,andβ-pinene contributed the most to ozone production,accounting for more than73.93%,which significantly varied with temperature and light.In this experiment,the ozone generation in the dynamic chamber under different temperature and light conditions was restricted by BVOCs or NOx,which made the actual ozone generation far lower than the expected potential,while,the variation regulation with temperature and light was similar to the prediction.