Compound-specific hydrogen isotope composition of n-alkanes in combustion residuals of fossil fuels

The hydrogen isotope compositions (δD) of n-alkanes present in the combustion residuals of fossil fuels (coal, gasoline, and diesel) were measured using GC-IRMS to distinguish between coal soot and vehicle exhaust. The n-alkane δD values of industrial and domestic coal soot ranged from −95.3‰ to −219.6‰ and −128.1‰ to −188.6‰, respectively, exhibiting similar tendencies. The δD values of the C15–C18 n-alkanes in both types of coal soot were nearly consistent, and the δD values of the C19–C24 n-alkanes exhibited a zigzag profile. The δD values of C16–C22 n-alkanes in gasoline exhaust exhibited a saw-tooth distribution, decreased with the carbon number, and were more positive than the δD values of C16–C22 n-alkanes in diesel exhaust, which increased with the carbon number. However, the δD values of the C23–C29 n-alkanes in gasoline and diesel vehicle exhaust were mostly consistent. The weighted average δD values of the C16–C19 n-alkanes in industrial and domestic coal soot were similar to the average δD values in gasoline and diesel vehicle exhausts; however, the average δD values of the C21–C29 n-alkanes in vehicle exhausts were richer in D than those in coal soot.