| 麦草及其烟尘中正构烷烃的组成 |
| 摘要点击 1820 全文点击 883 投稿时间：2013-03-02 修订日期：2013-04-23 |
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| 中文关键词 麦草 燃烧 烟尘 正构烷烃 CPI ACL |
| 英文关键词 wheat straw burn smoke n-alkane CPI ACL |
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| 中文摘要 |
| 在明火和闷烧条件下对6种麦草进行焚烧试验,用 GC/MS测定了秸秆和烟尘中正构烷烃的组成. 结果表明,从麦秆和烟尘中检出的正构烷烃主要是 C16~ C33. 麦秸中 正构烷烃的总含量变化范围是19.6~62.3 mg·kg-1, 平均值为36.0 mg·kg-1. 低碳数(碳数23)正构烷烃仅占总含量的1.4%~31.6%. C27/C29值分布于20.2%~47.4%之间,平均值为33.7%; C31/C29值分布于22.9%~48.1%之间,平均值为32.7%. 明火烟尘中正构烷烃总含量的变化区间为764.2~5304.1 mg·kg-1,平均值为2854.2 mg·kg-1. 低碳数正构烷烃在总含量中的占比为2.0%~19.4%,平均值为7.1%. C27/C29值的变化区间是10.0%~31.6%,平均值为20.2%; C31/C29比值的分布范围是47.1%~98.9%,平均值为71.2%. 闷烧烟尘中正构烷烃总含量为5126~15898 mg·kg-1,平均值为9220.8 mg·kg-1. 低碳数正构烷烃含量与总含量之比为1.9%~13.0%,平均值为5.5%. C27/C29的分布范围是8.6%~23.0%,平均值为13.8%; C31/C29的变化区间是42.5%~90.2%,平均值为62.2%. 麦草和烟尘中的正构烷烃均呈单峰式分布,其主峰碳数为 C29. 其高碳数(碳数≥C22)正构烷烃均具有明显的奇碳数优势. 麦草碳优势指数(CPI)的变化区间是4.0~33.6,平均值为19.2; C17~C33正构烷烃的平均碳链长度(ACL)的波动区间是25.2~29.0,平均值为28.0. 明火烟尘的CPI处于4.4~27.1之间,平均值为12.4; ACL值变化范围是27.6~29.4,平均值为28.8. 闷烧烟尘的CPI值分布于5.5~29.6之间,平均为18.0; ACL值在28.0~29.5之间变动,其平均值为28.9. 在麦秸与其烟尘之间,正构烷烃在化学组成上有明显的差别. 这有助于识别大气颗粒物中麦草燃烧来源的此类污染物. |
| 英文摘要 |
| Straw of six wheat species was burned under flaming and smoldering conditions. Chemical compositions of n-alkanes in the straw and its smoke were measured with GC/MS. The results showed, the main compounds in all samples were C16 to C33, and the total amounts of n-alkanes in the straw were between 19.6 and 62.3 mg·kg-1, with a mean value of 36.0 mg·kg-1. Moreover, the ratios of the contents of n-alkanes with low carbon number (23)to the total n-alkanes varied from 1.4% to 31.6%. The C27/C29 values in straws ranged from 20.2% to 47.4% with an average of 33.7%, and the C31/C29 values ranged from 22.9% to 48.1% with a mean value of 32.7%. In the flaming smoke, the total contents were 764.2 to 5304.1 mg·kg-1, with a mean value of 2854.2 mg·kg-1. And the contribution of the compounds with low carbon number to the total contents was 2.0% to 19.4%, the mean of which was 7.1%. Furthermore, the C27/C29 ratios changed from 10.0% to 31.6% with an average of 20.2%, and the C31/C29 values ranged from 47.1% to 98.9% with a mean of 71.2%. In the smoldering smoke, the total contents were in the range of 5126 to 15898 mg·kg-1, and the mean value was 9220.8 mg·kg-1. The ratios of the content of n-alkanes with low carbon number to the total n-alkanes varied from 1.9% to 13.0%, and the average value was 5.5%. In addition, the C27/C29 values ranged from 8.6% to 23.0% with a mean of 13.8%, and C31/C29 ratios varied from 42.5% to 90.2% with an average of 62.2%. In both the straw and the smoke, n-alkanes showed unimodal distribution with a peak at C29. The compounds with high carbon number (>C21) in all samples had evident odd to even carbon number predominance. The carbon predominance index (CPI) for the straw ranged from 4.0 to 33.6 with a mean value of 19.2, and the corresponding average carbon chain length(ACL)varied from 25.2 to 29.0 with a mean of 28.0. The CPI for flaming smoke was between 4.4 and 27.1 with a mean value of 12.4, and the corresponding ACL varied from 27.6 to 29.4 with an average value of 28.8. The CPI values for smoldering smoke ranged from 5.5 to 29.6 with a mean of 18.0, and the ACL was from 28.0 to 29.5 with an average value of 28.9. In short, there were visible differentiations among the chemical compositions of n-alkanes in wheat straw and its smoke, which are helpful for identifying the organic contaminants in ambient aerosol from wheat straw burning. |
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