城市化进程对地下河中溶解态正构烷烃来源的影响

为了探明城市化进程影响下地下河溶解态正构烷烃(D-ALK)的组分特征,于2014年11月至2015年4月,分别对受不同程度城市化进程影响的老龙洞与青木关两条地下河出口(老龙洞口、姜家泉)进行采样,利用气相色谱-质谱联用仪(GCMS)对样品中的D-ALK进行定量分析.结果表明,两地D-ALK碳数分布均为n C14~n C35.其中,姜家泉中的溶解态正构烷烃总量(DT-ALK)为102~356 ng·L~(-1),平均值为230 ng·L~(-1).2014年12月、2015年1月和4月,其正构烷烃碳数分布的峰型均为"单峰-前锋"型;LMH/HMH(n C-21/n C+22)为2.0~10;在n C14~n C25内碳优势指数(CPI14~25)为0.19~0.57,主碳峰均为C16(C_(max)16).2014年11月、2015年2月与3月,其碳数分布呈"双峰"形态,LMH/HMH与CPI14~25均小于1且C_(max)16;CPI24~35为1.2~23,C_(max)31或C_(max)33;Paq分别为0.2、0.7和0.1.其中,2014年11月与2015年3月的烷烃指数(AI)分别为0.95和0.98.老龙洞出口中的DT-ALK为110~697 ng·L~(-1),平均值为310 ng·L~(-1);各月碳数分布均呈现"单峰-前峰"峰型且C_(max)16,CPI14~25小于1.在旱季,由于受到不同人为活动的综合影响,以微生物输入为主的老龙洞中的溶解态正构烷烃在含量和组分的稳定性方面均大于以微生物和微生物、植物混合输入为主的姜家泉.

Impact of Urbanization on the Sources of Dissolved n-alkane in Underground River

To investigate the influence of urbanization on the component features of dissolved n-alkanes (D-ALK) in the underground river in the dry season, water samples were collected respectively at the outlet of the two underground rivers. Components of D-ALK in these samples were quantitatively analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that the distribution of D-ALK carbon number at the two sites ranged from nC₁₄ to nC₃₅ in dry season. The total concentration of D-ALK (DT-ALK) in Jiangjia spring ranged from 102 to 356 ng·L^-1, with an average of 230 ng·L^-1. The low-number carbons were predominant in December 2014, January and April 2015. The ratios of LMH/HMH (nC₂₁^-/nC₂₂⁺) ranged from 2.0 to 10. The carbon preference index (CPI) between nC₁₄ and nC₂₅ ranged from 0.19 to 0.57, with a maximum of C₁₆ (C_max16). However, in November 2014, February and March 2015, these samples had a bimodal distribution in n-alkane. All of the CPI_14-25 and the ratios of LMH/HMH were less than 1. The CPI_24-35 ranged from 1.2 to 23 with the C_max 31 or C_max33. During the three months, the values of Paq were 0.2, 0.7 and 0.1, respectively. The alkane indexes (AI) in November 2014 and March 2015 were 0.95 and 0.98, respectively. The values of DT-ALK in Laolongdong ranged from 110 to 697 ng·L^-1 with an average of 310 ng·L^-1. The carbon number distribution of each month had a low predominance, and the CPI_14-25 was less than 1. In the dry season, under the influence of different human activities, the content and component of D-AKL in Laolongdong which originated mainly from microorganisms was more stable than that in Jiangjia spring, which was mainly derived from microorganisms and a mixture of microorganisms and plants.