Composition of Lipid Compounds in the Peat Deposit in Mildred Bog from the Athabasca Region, Canada

doi:10.19657/j.geoscience.1000-8527.2018.05.07

Abstract

Abstract:

A total of 37 peat samples from Mildred bog in the Athabasca Region, Canada, were analyzed with GC-MS to reveal the compositional characteristics and origins of peat lipids. The results show that long-chain components predominate in the n-alkanes, n-alkan-2-ones, n-alkanals, n-alkanols, n-fatty acids and fatty acid methyl esters, with strong odd or even carbon predominance. Polar compounds of steroids and terpenoids are also present in relatively high abundances. According to molecular geochemistry of the peat samples, the organic matter in Mildred peat profile was mainly derived from the in situ vascular plants, and also from Sphagnum and aquatic plants. Woody plants of conifer, woody debris and Ericaceae, herbaceous plants of Cyperaceous, and Sphagnum are the main peat-forming plants. Among polar compounds, γ-lactone is considered to be a self-oxidation product of tocopherols. A series of sesquiterpene, pentacyclic triterpenoid ketones, pentacyclic triterpenoid alcohols and pentacyclic triterpenes are abundant in the top interval,and their formation are associated with Sphagnum or higher plants. Most steroids are not origin-specific, and the distributions of C₂₈, C₂₉ and C₃₀ steroids are assigned to a higher plant source. γ-Sitosterol, campesterol and stigmastan-3,5,22-triene are effective biomarkers for terrigenous higher plants.

Key words: peat, lipids, material source, steroid, terpenoid

CLC Number:

P593
TE122

HE Dashuang, HUANG Haiping, HOU Dujie, ZHANG Penghui. Composition of Lipid Compounds in the Peat Deposit in Mildred Bog from the Athabasca Region, Canada[J]. Geoscience, 2018, 32(05): 938-952.

Figures/Tables 13

Fig.1 Mass chromatograms (m/z 85) and dominant carbon number of n-alkanes in the Mildred peat profile

Fig.2 Distributions of n-alkane proxies in the Mildred peat profile

Fig.3 Mass chromatograms (m/z 59) and dominant carbon number of n-alkan-2-ones in the Mildred peat profile

Fig.4 Distributions of n-alkan-2-one proxies of K27/(K29+K31) and ACL-ket in the Mildred peat profile

Fig.5 Mass chromatograms of n-alkanals in the Mildred peat profile (m/z 82)

Fig.6 Mass chromatograms of n-fatty acids in the Mildred peatland (m/z 73)

Fig.7 Mass chromatograms of n-fatty acid,methyl ester in the Mildred peatland (m/z 74)

Fig.8 Diagram of total ion chromatogram and the identification of polar compounds in the Mildred peatland(Sample: -0.82 cm)

Fig. 9Mass spectra of representative terpenoids and their molecular configurations in the Mildred peatland

Fig.10 Distributions of α-, β-, γ-tocopherol and γ-lactone, and the γ-lactone/tocopherol ratio in the Mildred peat profile

Fig.11 Distributions of representative pentacyclic triterpenoids in the Mildred peat profile

Fig. 12 Mass spectra of representative steroids and their molecular configurations in the Mildred peatland

Fig.13 Distributions of representative steroids in the Mildred peat profile

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