加拿大阿萨巴斯卡地区泥炭正构烷烃与正烷酮地球化学特征

Geochemical Characteristics of n-alkane and n-alkan-2-one in Mildred Peat Bog from the Athabasca Region,Canada

通过对泥炭正构烷烃和正烷酮的地球化学特征的系统分析,以探讨阿萨巴斯卡地区Mildred泥炭沼泽的物源输入特征,以及正构烷烃和正烷酮的内在成因关系,从而揭示研究区泥炭记录的生物信息和植被演化特征。结果表明:Mildred泥炭正构烷烃和正烷酮均以高分子量C23~C33为主,呈后峰型分布,奇碳优势明显,物源以原地堆积的陆源高等植物为主,少量苔藓类、水生植物也有一定程度的贡献。根据主成分分析和正构烷烃指标,Mildred泥炭分子指示物源输入具有分段性,上段(地表至-17 cm)成炭植物以锈色泥炭藓为主,中段(-17 cm至-41 cm)沉积有机质主要来源于木质树根、杜鹃花科、黑云杉和莎草科等,下段(-41 cm至底部)莎草科类富集,少量松柏、杜鹃花科等木质植物发育。正构烷烃和正烷酮的分布极具相似性,同奇碳数正构烷烃与正烷酮极高的相关性论证了两者的内在成因联系。泥炭中正烷酮类化合物主要来源于相应正构烷烃的微生物氧化作用,剖面上部锈色泥炭藓的富集对正烷酮有一定程度的贡献;结合FT-MS资料,脂肪酸的微生物β-氧化和脱羧基作用是形成正烷酮的另一种有效路径,但不是主要的成因路径。

The geochemistry of n-alkane and n-alkan-2-one in the Mildred peat bog of the Athabasca region is systematically analyzed in order to determine the source material of organic matters in peat,and explore the genetic correlation between n-alkane and n-alkan-2-one,which reveals some biological information and vegetation evolution characteristics in the study peat bog.The distributions of n-alkane and n-alkan-2-one are characterized by high molecular weight and post peak pattern,with strong odd over even predominances,which indicates that the peat organic materials are primarily derived from in situ terrigenous higher plants,whereas the contribution from sphagnum and aquatic plants seems to be small.In accordance with principal component analysis(PCA)and n-alkane proxies distributions,the Mildred peat profile is divided into three intervals,the peat-forming plant in the upper interval(living layer to-17 cm)containing mainly Sphagnum fuscum;the middle interval(-17 cm to-41 cm)with woody plants,Ericaceae,piece needles and minor Cyperaceous as the in situ accumulated plants;and the deeper interval(-41 cm to the bottom)containing a number of Cyperaceous plants increased with some woody debris and Ericaceae grow.The similar distribution between n-alkane and n-alkan-2-one suggests microbial oxidation of related n-alkanes as the primary source of n-alkan-2-one in the Mildred peat bog.A direct input from peat-forming plants also contributes to n-alkan-2-one formation,particularly in the top profile.Microbialβ-oxidation and decarboxylation of n-fatty acids can be also considered as an alternative origin of n-alkan-2-ones but its contribution is not significant.