Characteristics Of Particulate Matter Emitted From Low Condensation Point Diesel Oil In Cold Region

Diesel engine is the main power mode of heavy trucks in China.According to the increasing contribution of diesel emissions to air pollution,the emission test of diesel engine is carried out to explore the variations associated with engine speed,engine load and fuel type.This study applied the dynamometer to run the engine emission test.Three types of diesel were selected,including 0#,-20#,and-30#.Samples of fine particles were collected in different size fractions,and were tested by DRI OC/EC analyzer and ICP-MS、ICP-OES,for carbonaceous matters and heavy metals,respectively.The research is aimed to compare emissions from low condensing diesel to the plain diesel.A model of health risks evaluation was established to calculate the exposure levels to heavy metals,and evaluate the risks to health.The proportions of carbonaceous matters in fine particles were similar for all types of diesel.The fraction of EC2 is the highest,which is significantly higher than other components.Under different working conditions,the proportion of elemental carbon in the total carbon is more than 70%.The low OC/EC ratios showed that the air-fuel ratios were low,hence,the fuel were not completely burned.In sum,the mean emission factor of PM_2.5is higher than that of PM_1.0.The highest emission factor of elemental carbon was appeared,when the low engine speed combined with high load.When the engine speed increased gradually,the content of elemental carbon decreased significantly.Under the same test cycle,the carbonaceous matters emitted from-20 diesel combustion was higher than that from-0 diesel and-35 diesel,for both particle sizes.The results showed that the inorganic element emissions from the three types of diesel were similar.The inorganic element emissions were the most severe,when the engine speed is low.It suggested that engines should not keep running at low speed for a long duration,in order to reduce the emissions of Cr,Ni,Zn,Ba,Mo and other heavy metals.The average emissions of heavy metals from 0#diesel were higher than that from–35#diesel and–20#diesel.There was a strong correlation between the elements,which pointed significant effects onto each other.The order of heavy metal exposure levels of three diesel was hand and mouth feeding>skin contact>breathing inhalation.Children’s exposure to heavy metals was higher than adults.The amount of PM_2.5-heavymetal exposure was slightly higher than that of PM_1.0-heavymetal exposure.The carcinogenic metal Cr was close to the critical value of carcinogenic risk,more attention should be paid,and the control criteria of Cr emissions from diesel combustion are needed.Although Mn had non carcinogenic risk to human,it had other risks to health,therefore,people should also pay attention to it.