Chemical Composition Of N-alkanes And N-alkanoic Acids In Three Types Of Agricultural Straw And The Smoke

Biomass burning as a global problem, is gaining widespread concern. Biomass burning is an important source of gaseous and particulate pollutants in the atmosphere and has a significant impact on global atmospheric chemistry, global climate and global ecosystem change.There is a large amount of biomass in China, where650millions tons of straw are harvested every year,31.5%of them were used as the residential energy source for cooking, and25%were burnt in the field for land-clearing. Farmland straw burning can significantly affect the concentration of pollutants in the air in a short time and a limited range.And it can transport gaseous pollutants and fine particulate matter, which is harmful to human’s health.Biomass burning problems have caused more concern, many scholars have estimated the emission factors of some pollutants, but very few reports on the organic composition of particulate matter. N-alkanes and n-alkanoic acids as important classes of organic pollutants in urban atmospheric aerosol, which are two of the biomass burning instructions substances can be used for biomass burning emission contribution of qualitative identification and assessment in atmospheric particulate matter. In this study, we not only studied n-alkanes and n-alkanoic acids’s composition features in three kinds of straw(rice straw, corn straw and wheat straw),but also used furnace to simulate open field burning of crop straw in the laboratory, analyzed and compared with the contents of n-alkanes and n-alkanoic acids samples gathered from the rice straw, corn stover and wheat straw flame burning and smoldering burning by the advanced characterization of measurement system. We summarized the composition of the three compounds from different straws in different combustion.The results reached the following conclusions:(1) The content of the straw’s n-alkanes:wheat straw> rice straw> corn straw, rice straw and wheat straw’s are C29in the main peak, corn straw’s is the C31in the main peak. And the highest CPI is wheat straw’s, rice straw and corn straw’s CPI are close. The content of the straw’s n-alkanoic acids:rice straw> corn straw>wheat straw, rice straw and corn straw’s are C16and C24in the main peak, wheat straw’s is C16in the peak.(2) The content of open flame combustion soot’s n-alkanes:rice straw> wheat straw>corn straw, n-alkanes show double peaks. And the highest CPI is wheat straw’s, corn straw and rice straw’s CPI are close. The content of open flame combustion soot’s n-alkanoic acids:rice straw> corn straw>wheat straw, rice straw and corn straw’s are C16and C24in the main peak, wheat straw’s is C16in the peak.(3) The content of smoldering soot’s n-alkanes:wheat straw>rice straw> corn straw, n-alkanes show double peaks. And the highest CPI is wheat straw’s, corn straw and rice straw’s CPI are close. The content of smoldering soot’s n-alkanoic acids:rice straw> corn straw>wheat straw, rice straw and corn straw’s are C16and C24in the main peak, wheat straw’s is C16in the peak.(4) Rice straw, corn straw and wheat straw smoldering soot’s n-alkanes content were2.0-4.8times,1.3-4.5times and10.3times than the fire burning soot’s; rice straw, corn stalks and wheat straw smoldering soot’s n-alkanoic acids content were2.6-11.1times,2.8-4.3times and5.2times than the fire burning soot’s.