Study On The Air Pollutants Emitted From The Production Of Major Grain Crops In China And Their Human Health Effects

A strong agricultural country is the root of a strong socialist modernization country,and promoting agricultural modernization is an inevitable requirement for achieving high-quality development.Agriculture is the basis for ensuring human social development and national stability,but pollutants emitted from crop production are an important source of air pollutants,and a comprehensive analysis of the air pollution situation and health damage caused by them should be conducted.The rapid growth of China’s population in recent decades has led to a significant increase in demand for grain.Driven by a combination of policy and demand,grain production has expanded rapidly.Expanded agricultural production emits large amounts of particulate matter and gaseous pollutants,which can lead to degradation of air quality and harm human health.In previous studies on the estimation of crop pollutant emissions,the main focus has been on NH₃ emissions from the fertilizer application process,with less detailed estimation of the types of pollutants and emissions emitted from other production processes.To get a more comprehensive understanding of the impact of crop production on air pollution in China,this study estimated the pollutant emissions from three major crops（rice,corn and wheat）in 2017 in six agricultural production stages（fertilizer application,harvesting,grain handling,straw burning,agricultural machinery and land preparation）based on a bottom-up approach,and compiled their high-resolution air pollutant(CO,NH₃,NO_X,PM_2.5,SO₂ and VOCs)gridded（0.25°×0.25°）emission inventories.This paper analyzes the temporal trends of pollutant emissions from agricultural sources and the spatial distribution characteristics,and discusses the contribution share of emissions from different agricultural segments.To investigate the impact of pollutant emissions from agricultural crops on air quality.Based on the compiled emission inventories and combined with the WRF-Chem model,this study simulated and analyzed the effects of three major grain crops on atmospheric PM_2.5concentrations in China.Finally,exposure-response relationships were used to quantify the number of premature deaths due to crop pollutant emissions.The main findings derived from this paper are as follows:（1）The total emissions of CO,NH₃,NO_X,PM_2.5,SO₂ and VOCs from the production of major grain crops in China in 2017 were 8,099,400 tons,2,792,700 tons,1,123,500 tons,2,155,600 tons,120,400 tons and 1,652,000 tons,respectively.The emission of pollutants from major grain crops in China shows a spatial distribution pattern of East>Central>West,and the emission of pollutants is concentrated in the middle and lower reaches of the Yangtze River,the Yellow and Huaihai plains and the Northeast plains,and other agriculturally developed grain-producing areas.The emissions of various pollutants show strong seasonal changes and the trends are basically the same,showing autumn>summer>spring>winter,with CO,NO_X,PM_2.5,SO₂ and VOCs all peaking in June and October,and NH₃ emissions peaking in May.（2）For the air pollutant emission inventory related to the production of major grain crops compiled in this paper,in terms of crop contribution,the main crop contribution of NH₃ and NO_X is corn,the main crop contribution of PM_2.5 and VOCs is rice,and the main contribution of CO and SO₂ is wheat;in terms of the contribution of the production chain,straw burning has the largest contribution to the emissions of SO₂,CO,PM_2.5 and VOCs contributed the most,fertilizer application contributed the most to the emission of NH3,and agricultural machinery contributed the most to the emission of NO_X.（3）The annual average concentration of PM_2.5 contributed by total pollutant emissions in production of major grain crops in China is 1.88μg/m³,which shows a spatial distribution of high in the middle and east and low in the west,high in the south and low in the north,and the concentration in the middle and east is much higher than that in the west and north.Among them,the annual average PM_2.5 concentration contributed by pollutants emitted from rice in production was 1.46μg/m³;the annual average PM_2.5 concentration contributed by pollutants emitted from corn in production was 1.42μg/m³;and the annual average PM_2.5 concentration contributed by pollutants emitted from wheat production was 0.88μg/m³.In terms of temporal variation,the monthly average concentrations in January,April,July and October were 1.07μg/m³,1.4μg/m³,1.34μg/m³and 3.72μg/m³,respectively.（4）The contribution of air pollutants emitted from rice production to PM_2.5concentration in China is mainly concentrated in the south,with the most prominent contribution in July.The contribution of atmospheric pollutants emitted from wheat production to PM_2.5 concentrations in central,northern,northeastern and northwestern China is high,with the most prominent contribution in April,contributing more than40%to 80%.（5）PM_2.5 pollution caused by the production of three major food crops in China led to a total of 45,356（95%CI:31182～59227）premature deaths in 2017,mainly in areas with more concentrated food crop cultivation and production or dense population distribution,such as the Yellow and Huaihai Sea plain area,the middle and lower reaches of the Yangtze River,and the northeast plain area.Among them,PM_2.5 pollution from rice production caused the largest number of deaths,reaching 22,891（95%CI:15,627～30,097）,contributing 50.47%to the total number of deaths;PM_2.5 pollution from maize production caused 17,013（95%CI:11,668～22,263）premature deaths,contributing 37.51%to the total number of deaths;PM_2.5 pollution from maize production caused 37.51%to the total number of deaths.The PM_2.5 pollutants caused by wheat production contributed to 5453（95%CI:3718-7184）premature deaths,or12.02%.（6）Among the provinces in China,the province with the highest number of deaths due to PM_2.5 pollution caused by crop production was Henan Province,with a total of16725（95%CI:11450 to 22039）premature deaths,accounting for 36.87%.The contribution of different crops varied more significantly.Among them,PM_2.5 pollution caused by rice production contributed to more than 90%of premature deaths in the southern provinces of Jiangxi,Hunan and Anhui.PM_2.5 pollution caused by maize production contributed more to premature mortality in the central and northeastern provinces of China,contributing more than 70%to most provinces in the region;PM_2.5pollution caused by wheat production contributed the highest to premature mortality in Shaanxi,reaching 67%.