[Chemical compositions of n-alkanols in smoke from rice and maize straw combustion].
Six genotypes of rice straw and four genotypes of maize straw were burned under different conditions, and the smoke was collected and n-alkanol in it was measured by GC-MS. Results showed that, in the smoke from rice straw flaming combustion, n-alkanol was composed of individual compounds from C14 to C34, and total contents(sigma) changed in the range of 1 604.4 to 13 889.7 mg x kg(-1). The ratio values of amount for n-alkanol with lower carbon number to that for one with higher carbon number (L/H) were in the range of 0.02 to 0.09. The values for C24/C30, C32/C30, C30/sigma, CPI, and ACL varied from 3.3% to 19.6%, 8.4% to 19.9%, 53.9% to 72.6%, 8.7 to 21.5, and 29.0 to 30.1, respectively. The abundance distribution for the compounds was bimodal with the maximal and the second peaks at C30 and C24, respectively. In smoldering smoke of rice straw, individual n-alkanol from C14 to C34 were also analyzed, with sigma values varying in the range of 1 688.7 to 5 168.2 mg x kg(-1). The ratios for L/H, C24/C30, C32/ C30, and C30/sigma ranged from 0.08 to 0.14, 31.0% to 70.5%, 6.9% to 17.6%, 39.5% to 57.8%, respectively. In addition, the CPI and ACL values varied from 10.7 to 17. 5, and 27.2 to 28.5, respectively. Moreover, the distribution pattern was similar to that in flaming smoke. In flaming smoke of maize straw, n-alkanol from C12 to C34 were identified, with sigma values being in the range of 852.3 to 2 667.9 mg x kg(-1). The values for L/H, C24/C28, C32/C28, C28/sigma, CPI, and ACL varied from 0.2 to 1.0, 104.3% to 293.3%, 42.2% to 61.4%, 7.3% to 16.5%, 5.6 to 9.7, and 23.1 to 26.9, respectively. Besides, the abundance distribution pattern was mainly bimodal with a maximal peak at C30, C24 or C22. In the smoldering smoke for maize straw, the same individual n-alkanols were found, and the sigma values changed from 1493.0 to 8386.9 mg x kg(-1). The values for L/H, C24/C28, C32/C28, C28/sigma, CPI and ACL were in the range of 0.2 to 0.3, 53.6% to 217.6%, 21.7% to 75.9%, 8.8% to 27.3%, 4.2 to 6.5, and 26.3 to 27.2, respectively. Furthermore, the distribution pattern was bimodal as well with the highest peak mainly at C30 and the second one at C24. In brief, obvious discrimination exists among chemical compositions of n-alkanol in the straw and smoke. C24/C30, C32/C30, and C30/sigma are useful proxies in distinguishing between n-alkanol in airborne aerosol deriving from rice straw and one released in rice straw combustion process. L/H, C24/C28, C32/C28, and C28/sigma may have a potential in discriminating the compounds from maize straw and its burning. L/H is possibly used to makea distinction between the organic compounds from rice and maize straws, and/or from combustion of the straws.