Simulation Of Agricultural Land’s Contribution To PM₁₀ And PM_2.5 In Wuhan

Atmospheric particulate pollution is one of the most serious problems of atmospheric environment in our country,such as PM₁₀and PM_2.5,can bring important effects on human health.The main source of PM₁₀and PM_2.5 are industrial combustion,motor vehicle exhaust,the dust and soil.Our country is a major agricultural country,and the soil structure of farmland was vulnerable to agricultural activities such as ploughing.The destroyed soil structure under the action of external such as wind was easily to generate atmospheric particulates,e.g.PM₁₀and PM_2.5.These particles carrying a large amount of chemical fertilizer,pesticide and heavy metal residues,have great harm to human health.Thereby,understanding the contribution of the agricultural soil to PM₁₀and PM_2.5 has an important scientific meaning.The soil sample was collected at Jiangxia base of the Chinese academy of sciences,used to conducted the laboratory simulation experiment.And then to discuss the effect of speed,ploughing,soil fractions and moisture content of soil on release of PM₁₀and PM_2.5 from the agricultural soil.The main conclusions are as follows:（1）The PM samples collected in the laboratory simulation experiment are monomer or aggregation with irregular structure,which are same as the morphology of the typical soil mineral particles.The chain,globular,cellular morphology of the combustion products did not be observed in the PM samples form the agricultural soil.（2）The soil was strongly crushed by ploughing.After ploughed,the particles size of<1 mm and 1～2 mm shifted to the smaller size.The distribution of 5～10μm particles were 62.57%in<1 mm soil particles sample and the 1.62～5μm particles were 83.9% when with the size of between 1 and 5μm contributed to 62.57%of the total amount of soil particles with the size of less than 1 mm.after the ploughing at the rate of 30 r/min,the soil particles with the size of between 1 and 5μm contributed to 83.9%of the total amount of soil particles with the size of less than 1 mm,and after the ploughing at the rate of 100 r/min,the soil particles with the size of between 1.10 and 3.14μm contributed to 88.8%of the total amount of soil particles with the size of less than 1mm.For soil particles with the size of 1-2 mm,after the ploughing at the rate of 30 r/min,the particle size distribution shifted to the smaller particle size between 30 and 300μm,and after the ploughing at the rate of 100 r/min,the soil particles with the size of 40μm had large quantity in the total soil particles.（3）The release amount of PM₁₀and PM_2.5 increased with the increase of air speed and ploughing strength.At air speed of 0.5 m/s and 3 m/s,the mass concentration of PM₁₀ and PM_2.5 from soil particles with the size of less than 2 mm were 56.8,48.1 and 304.5,175.1μg/m³,respectively.At ploughing strength of 0 r/min and 100 r/min,the mass concentration of PM₁₀and PM_2.5 from soil particles with the size of less than 2mm were 79.4,58.9μg/m³and 17140.5,130.8μg/m³,respectively.The ploughing had stronger influence on the release of PM₁₀and PM_2.5 than wind erosion. （4）The release amount of PM₁₀and PM_2.5 decreased as a power function of the moisture content of soil.The release amount of PM₁₀and PM_2.5 at 7%of the moisture content of soil were 17%,19%of the release amount of PM₁₀and PM_2.5at 3.4%of the moisture content of soil.The mass concentration of PM₁₀and PM_2.5 from soil particles were 2162.59 and 1254.83μg/m³,respectively,at 3.4%of the moisture content of soil.The mass concentration of PM₁₀and PM_2.5 from soil particles were 368.68 and 239.38 μg/m³,respectively,at 7.03%of the moisture content of soil.The threshold of the moisture content of soil was 21.5%,21.9%.（5）The release amount of PM₁₀and PM_2.5 increased with the increase of the initial friction wind speed in way of 4 times the power function.For soil particles with the size of less than 1mm,the initial friction wind speeds were 0.282 m/s and 0.245 m/s at ploughing strength of 0 r/min and 100 r/min,respectively.For soil particles with the size between 1 and 5 mm,the initial friction wind speed at ploughing strength of 100 r/min decreased by 23%than at ploughing strength of 0 r/min.The release amount of PM₁₀and PM_2.5 decreased as 4 times power function of the initial friction wind speed.（6）Considering the influence of wind on ploughing,the annual loss amount of overburden of agricultural soil in Wuhan city was expected to be 299.57 ton,in which the amount of PM_2.5 was around 169.14 ton.When air speed is static or slow,the annual loss amount of overburden of agricultural soil in Wuhan city was expected to be 290.51 ton,in which the amount of PM_2.5 was around 169.98 ton.