Study On Biogenic Volatile Organic Compounds Emission Fluxes From Spring Wheat In Hetao Irrigation District Of Inner Mongolia

Recently,regional environmental pollution caused by ozone has become increasingly serious in northern China.Biogenic Volatile Organic Compound（BVOC）is one of the important precursors of ozone formation in the regional environment.To control ozone pollution in northern China,it is necessary to identify the impact of BVOC emissions from the Inner Mongolia Plateau ecosystem on regional ambient ozone pollution.There have been many studies on BVOC emissions from grassland and forest ecosystems in the Inner Mongolia Plateau,but few studies have been conducted on BVOC emissions and emission patterns from agricultural ecosystems.Agricultural ecosystems are an integral part of BVOC emissions from the Inner Mongolia Plateau ecosystem.In order to reveal BVOC emissions from spring wheat in the Hetao Irrigation District of Inner Mongolia and its emission patterns,improve the database of BVOC emissions from the Inner Mongolia Plateau and enrich the basic emission database of BVOC from farmland plants in China,this study used dynamic box sampling technique and automatic thermal desorption desorption-gas chromatography-mass spectrometry（ATD-GC/MS）to study the16 kinds of BVOC from spring wheat in the Hetao Irrigation District.The parameters of temperature,humidity and photosynthetically active radiation（PAR）were simultaneously recorded.The feasibility of the study was verified in September 2020 by cultivating potted plants in both sandy loam and loam soils.The results showed that:（1）Wheat grown in both sandy loam and loam soils in the pot experiment emitted 16 VOCs including Isoprene,α-pinene,β-Mycrene,β-pinene,3-Carene,P-Cymene,Limonene,γ-terpinene,Ocimene,Camphene,Benzene,Toluene,Ethylbenzene,p-xylene,m-xylene and o-xylene.（2）Sandy loam and loam cultivated wheat mainly emittedα-pinene,Toluene and Isoprene with emissions of（4.76～33.42）,（5.61～31.67）,（4.01～24.19）ng/（g·h）and（7.28～46.61）,（4.05～33.13）,（3.07～26.32）ng/（g·h）respectively;potted BVOC emissions were higher in wheat during the growing period than at maturity.On the basis of the pot experiment,field experiments on spring wheat in the Hetao Irrigation District were carried out with Hangjinhouqi,Linhe,Wulateqianqi and Wulatezhongqi regions as the study areas.The results showed that:（3）Spring wheat in the Hetao Irrigation District emits 16 VOCs including Isoprene,α-pinene,β-Mycrene,β-pinene,3-Carene,P-Cymene,Limonene,γ-terpinene,Ocimene,Camphene,Benzene,Toluene,Ethylbenzene,p-xylene,m-xylene and o-xylene.（4）Spring wheat in the Hetao Irrigation District mainly emits toluene,isoprene andα-pinene,with emissions of（4.03～42.51）,（0.67～17.89）and（0.88～7.28）ng/（g·h）respectively;total BVOC emissions are（10.76～116.81）ng/（g·h）,with Benzene emissions being the highest,followed by Monoterpene and Isoprene,with emissions of（7.35～76.66）,（1.93～21.82）and（0.67～17.89）ng/（g·h）.（5）Emissions of BVOC from spring wheat in the Hetao Irrigation District ranged from high to low in the senescence,growth and maturity stages,with emissions ranging from（2.08～187.73）,（15.13～129.72）and（11.88～92.44）ng/（g·h）,respectively.Emissions of Isoprene and Monoterpenes were higher in the senescence and growth periods than in the maturity period,and emissions of Benzene were higher in the senescence than in the growth and maturity periods.（6）Emissions of Isoprene,Monoterpene and Benzene,the main emissions of spring wheat in the Hetao Irrigation District during the study period,were exponentially related to ambient temperature and light intensity,with temperature dependence coefficients R~2 ranging from 0.6777～0.9462 and light intensity dependence coefficients R~2 ranging from 0.8618～0.9370.Spring wheat BVOC emissions in the Hetao Irrigation District show a strong temperature and PAR dependence as ambient temperature and light intensity rise over a range of ambient temperatures and light intensities.（7）Emissions of BVOC in spring wheat in the Hetao Irrigation District differed under different growth states（T=303K,PAR=1000μmol/（m~2·s））,in the order of senescence（127.57±37.79）ng/（g·h）>growth（74.81±12.25）ng/（g·h）>maturity（42.23±10.86）ng/（g·h）.The results of this study will provide scientific data for the study of the influence of BVOC emissions on regional environmental ozone pollution in the Inner Mongolia Plateau ecosystem and the improvement of the BVOC emission inventory of farmland ecosystems as well as the study of the spatial and temporal distribution characteristics of BVOC emissions from farmland ecosystems.