Abstract Aliphatic hydrocarbons in the sediments of the estuarine mangrove forests of Cochin region, Southwest coast of India were characterized to assess the sources of organic matter (OM) and to validate the effectiveness of the various geochemical indices to identify multiple OM sources and the complex geochemistry of these tropical coastal environments. The total concentration of the n-alkanes varied from 606.39 to 826.25 µg/g [dry weight (dw)] in mangrove sediments, to values between 230.10 and 287.67 µg/g in estuarine sediments. The n-alkane distribution in the study region indicated a strong odd over even predominance in both mangrove and estuarine sediments. Assessment using terrestrial OM indices such as Carbon Preference Index (CPI), Terrigenous Aquatic Ratio (TAR), and Terrestrial Marine Discriminant (TMD) suggested that a large fraction of OM in the mangrove sediments was derived from mangrove plant litter and a better preservation of mangrove OM in the sedimentary environment has occurred. These findings are supported by the higher content of total lipid, tannin, and lignin, as well as by the depleted δ13C values. Low ratios of CPI, TAR, and TMD at estuarine sites E2 and E3 indicated a mixed origin of OM. Natural or biogenic indices such as natural n-alkanes ratio (NAR), Σn-alkanes/n-C16, n-C29/n-C17, and LMW/HMW revealed that all the mangrove stations and the estuarine station E1 received OM from natural or biogenic sources, whereas a significant anthropogenic input was noticed for estuarine stations E2 and E3. Indices like Pr/Ph, Pr/n-C17, Ph/n-C18 further confirmed the mixed nature of OM accumulated under the anoxic environment.

中文翻译：

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热带红树林河口脂肪烃清单：生物标志物方法

摘要 对印度西南海岸科钦地区河口红树林沉积物中的脂肪烃进行表征，以评估有机质 (OM) 的来源，并验证各种地球化学指标识别多种有机质来源和复杂地球化学的有效性。这些热带沿海环境。红树林沉积物中正构烷烃的总浓度为 606.39 至 826.25 µg/g [干重 (dw)]，河口沉积物中的值介于 230.10 至 287.67 µg/g 之间。研究区域的正构烷烃分布表明，红树林和河口沉积物中的正构烷烃呈强奇数超过偶数优势。使用陆地 OM 指数进行评估，例如碳偏好指数 (CPI)、陆源水生比 (TAR)、和陆地海洋判别式 (TMD) 表明，红树林沉积物中的大部分 OM 来自红树林植物凋落物，并且在沉积环境中红树林 OM 得到了更好的保存。这些发现得到较高含量的总脂质、单宁和木质素以及耗尽的 δ13C 值的支持。河口站点 E2 和 E3 的 CPI、TAR 和 TMD 的低比率表明 OM 的混合来源。天然正构烷烃比 (NAR)、Σn-烷烃/n-C16、n-C29/n-C17 和 LMW/HMW 等自然或生物指数表明，所有红树林站和河口站 E1 都收到了来自天然或生物源，而在河口站 E2 和 E3 中注意到显着的人为输入。Pr/Ph、Pr/n-C17 等指数，