Study On Environmental Influence Factors Of Biogenic Volatile Organic Compounds In Grassland Ecosystem

Biogenic Volatile Organic Compounds（BVOCs）have high reactivity and are important precursors of ozone and secondary organic aerosols.And there are few studies on the emission patterns and environmental impact factors of BVOC from grassland ecosystems.In order to improve BVOCs emission inventory of grassland ecosystem,establish BVOCs estimation model of grassland ecosystem,and study the relationship between BVOCs emission flux of grassland ecosystem and environmental impact factors.Chenbalhu grassland,Ewenki grassland and Erguna grassland were selected as sampling sites from 2019.07 to 2020.08;Leymus chinensis,Stipa baicalensis,Medicago falcate,Artemisia frigida Willd.,Urtica cannabina,Iris lactea Pall.var chinensis,Cleistogenes squarrosaKeng,Artemisiascoparia Waldst.,Artemisia dacunculus and weeds were selected as the research objects;The BVOCs sampling and analysis of grassland ecosystem were conducted by dynamic box sampling and gas chromatography-mass spectrometry;Qualitative Quantitative analysis of BVOCs emitted from different species of grass in grassland ecosystems;environmental impact factors including temperature,photosynthetic active radiation and humidity were recorded at the sampling sites during the sampling period.To estimate the standard emission fluxes of BVOCs from different grass species by improving the empirical constant based on G95model.Combined with the measured data and model estimation data,the relationship between the emission flux of BVOCs from different grass species and environmental impact factors was analyzed.The results are as follows:（1）According to the results of qualitative analysis,19 kinds of BVOCs were identified,including Isoprene,α-Pinene,Camphene,β-Pinene,β-Mycrene,α-Phellandrene,3-Carene,α-Terpinene,P-Cymene,Limonene,Ocimene,γ-Terpinene,Terpiolene,Benzene,Methylbenzene,Ethlbenzene,o-xylene,p-xylene and m-xylene;（2）The isoprene emission flux of Leymus chinensis,Stipa grandis,Medicago falcate,Artemisia frigida Willd.,Urtica cannabina,Iris lactea Pall,Cleistogenes squarrosaKeng,Artemisiascoparia Waldst,Artemisia dacunculus and weeds were（1.10～282.30）、（0.17～317.39）、（26.39～1259.73）、（5.59～54.48）、（36.50～8553.00）、（2.40～56.72）、（42.46～432.71）、（0.20-6.07）、（0.63～8.61）and（11.37-90.19）μg/(g_dw·h)respectively;The monoterpene emissions flux of Leymus chinensis,Stipa grandis,Medicago falcate,Artemisia frigida Willd.,Urtica cannabina,Iris lactea Pall,Cleistogenes squarrosa Keng,Artemisiascoparia Waldst,Artemisia dacunculus and weeds were（0.77～263.59）、（1.73～172.57）、（0.01～757.27）、（12.43～100.73）、（2.20～66.87）、（1.33～24.16）、（8.04～54.24）、（11.58～30.15）、（6.84～47.86）和0.32～80.59μg/(g_dw·h)respectively.（3）The main components of BVOCs emitted by grass seeds were related to their genera and species.Monoterpenes were mainly distributed in Artemisia L.of Compositae.Grass species such as Gramineae and Leguminosae mainly discharge isoprene.（4）According to the analysis of G95 model and the measured data of BVOCs emission flux of grass seeds,the empirical constants=0.039,₁=0.0033,β=0.05 were determined;the modified empirical constant model and G95 model were evaluated,and the modified model was better than the original model.According to the revised model,the standard（30℃,1000μmol/（m²·s））emission fluxes of isoprene from Leymus chinensis,Stipa grandis,Medicago falcate,,Artemisia frigida Willd.,Urtica cannabina,Iris lactea Pall,Cleistogenes squarrosa Keng,Artemisiascoparia Waldst,Artemisia dacunculus and weeds were 50.37μg/(g_dw·h),97.32μg/(g_dw·h),540.40μg/(g_dw·h),119.98μg/(g_dw·h),3699.61μg/(g_dw·h)and 35.69μg/(g_dw·h),respectively.The standard emission fluxes of monoterpenes from Leymus chinensis,Stipa grandis,Medicago falcate,Artemisia frigida Willd.,Urtica cannabina,Iris lactea Pall,Cleistogenes squarrosa Keng,Artemisiascoparia Waldst,Artemisia dacunculus and weeds were 78.18μg/(g_dw?h),21.01μg/(g_dw?h),80.09μg/(g_dw?h),60.17μg/(g_dw?h),32.76μg/(g_dw?h),13.67μg/(g_dw?h),16.19μg/(g_dw?h),14.18μg/(g_dw?h),17.49μg/(g_dw?h)and59.01μg/(g_dw?h)respectively.（5）According to the correlation analysis,BVOCs of grass seeds were positively correlated with temperature and photosynthetically active radiation,and negatively correlated with humidity;the main influencing factor of isoprene was photosynthetically active radiation,and the main influencing factor of monoterpenes was temperature.（6）The fitting equation between isoprene,α-Pinene emission flux of Leymus chinensis and temperature,photosynthetically active radiation and humidity were y=γ_iso（-0.6357x²+405.74x–64660）（R2=0.4183）、y=δ_iso（12.449ln（x）-48.712）（R2=0.0361）and y=ε（-58.26ln（x）+302.77）（R2=0.1687）;y=γ_mon（-0.0483x²+30.327x-4745.6）（R2=0.2603）and y=δ_mon（13.688ln（x）-84.089）（R2=0.3374）.The fitting equation between isoprene,monoterpene emission of Stipa grandis and temperature,photosynthetically active radiation and humidity were y=γ_iso（-0.4905x²+310.82x–49152）（R2=0.5145）、y=δ_iso（36.642ln（x）-126.33）（R2=0.2031）and y=ε（-65.51ln（x）+335.81）（R2=0.2075）;y=γ_mon（-0.0515x²+31.2x-4694.5）（R2=0.3567）and y=δ_mon（34.013ln（x）-219.53）（R2=0.114）.The fitting equation between isoprene,monoterpene emission of Medicago falcate and temperature and photosynthetically active radiation were y=γ_iso（0.367x²-200.48x+27230）（R2=0.601）and y=δ_iso（18.031ln（x）-25.525）（R2=0.0117）;y=γ_mon（0.5755x²-348.42x+52789）（R2=0.5461）and y=δ_mon（54.532ln（x）-281.04）（R2=0.1817）.（7）γ,δandεin the fitting equations of BVOCs emission flux of different grass species with temperature,PAR and humidity were the seasonal variation coefficients of emission flux which corresponds to temperature,PAR and humidity.The seasonal variation coefficientsγof BVOCs emission flux and temperature isγ_iso=0.00 from January to April and from November to December,γ_iso=0.54 in May,γ_iso=0.86 in June,γ_iso=1.00 from July to August,γ_iso=0.58 in September andγ_iso=0.36 in October;γ_mon=0.00 from January to April and from November to December,γ_mon=0.43 in May,γ_mon=0.77 in June,γ_mon=1.00 from July to August,γ_mon=0.51 in September andγ_mon=0.23 in October.The seasonal variation coefficientsδof BVOCs emission flux and photosynthetically active radiation areδ_iso=0.00 from January to April and from November to December,δ_iso=0.33 in May,δ_iso=0.56 in June,δ_iso=1.00 from July to August,δ_iso=0.46 in September andδ_iso=0.12 in October;δ_mon=0.00 from January to April and from November to December,δ_mon=0.62 in May,δ_mon=0.65 in June,δ_mon=1.00 from July to August,δ_mon=0.76 in September andδ_mon=0.34 in October.The seasonal variation coefficientsεof BVOCs emission flux and humidity areε=0.00 from January to April and from November to December,ε=0.89 in May,ε=0.93 in June,ε=1.00 from July to August,ε=0.84 in September andε=0.56 in October.The results of this study provide the scientific data for studying the spatial and temporal distribution of BVOCs in grassland ecosystem and establish the prediction model of BVOCs in grassland ecosystem.