摘要
pH是环境中影响生物地球化学过程的关键因子之一,其变化能够影响土壤肥力、改变环境微生物群落结构、影响海洋生物形成钙质骨骼和介壳等。不同沉积环境中pH的变化受控于不同的因素。对于地质历史时期一些重建起来难度较大的环境因素,如降雨量和大气CO_(2)浓度等的变化,pH能够充当“桥梁”的作用。通过重建沉积物或者水体中pH的变化进而间接实现对这些环境因子变化的反演。通过调查现代环境中生物脂类与环境关系等手段,已经逐渐发展起来一系列的环境pH代用指标,包括细菌支链型甘油二烷基甘油四醚化合物(GDGTs)的环化指标(CBT、CBT5ME、CBT6ME)和异构体指标IR(IR6ME、IBT等)、革兰氏阴性菌3-羟基脂肪酸的RIAN、Branched Index、RIN指标、C31藿烷的ββ/(αβ+ββ)立体异构体指标、长链正构2-烷基酮指标等。本文总结了基于生物脂类的pH指标其建立过程及应用原理,并对这些指标在古环境中的应用进行概述,归纳各自优缺点和应用范围,并提出了这些指标未来的研究方向。
pH is one of the key factors affecting biogeochemical processes in diverse environments.For example,soil pH can affect soil fertility and exert a significant impact on the microbial community structures in soils.The seawater pH could influence the growth of marine calcareous planktons.Thus,pH records in the geological past could be useful in biogeochemical studies.In addition,pH could be used as a‘bridge’to reconstruct other environmental variables that are not readily reconstructed,e.g.,mean annual precipitation(MAP)and pCO_(2).To date,a series of pH proxies have been developed based on the investigation of the relationship between the distribution of lipid biomarkers and pH in a variety of geological settings.These proxies include the cyclization index of branched glycerol dialkyl glycerol tetraethers(brGDGTs;CBT,CBT5ME,CBT6ME,CBT'),the isomerization index of brGDGTs(IR6ME,and IBT,etc.),3-hydroxyl fatty acid-derived indices(RIAN,and Branched Index,etc.),C31 hopaneββ/(αβ+ββ)ratio,and long-chain n-alkan-2-one-derived proxies.In this paper,we summarized the rationale for how these pH proxies were developed.The brGDGT-based pH proxies could be used in soils,lake sediments,stalagmites,as well as marine sediments.However,other lipid-based pH proxies could only be used in sediments where these proxies were initially developed,and it remains to be determined whether their applications could be extended to other geological settings.The pH range reconstructed from 3-hydroxyl fatty acid-derived proxies appears to be wider than GDGT-based pH proxies,suggesting that they could be used as pH proxies in extremely acid or alkaline sediments.Some lipid-based pH proxies,including TEX86,and isoGDGTIsomerIndex,could only be used to reconstruct environmental pH qualitatively because factors other than pH might also affect these indices.The brGDGT-based proxies have an advantage over other pH proxies,i.e.,brGDGTs were ubiquitous in diverse environments but the distributions of other lipids,e.g.hopanes,MAGEs,n-alkan-2-one,w
作者
黄钰莹
裴宏业
李婧婧
党心悦
钱施
赵世锦
杨欢
HUANG Yuying;PEI Hongye;LI Jingjing;DANG Xinyue;QIAN Shi;ZHAO Shijin;YANG Huan(Hubei Key Laboratory of Critical Zone Evolution,China University of Geosciences(Wuhan),Wuhan 430074,Hubei;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences(Wuhan),Wuhan 430078,Hubei;State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,Jiangsu)
出处
《第四纪研究》
CAS
CSCD
北大核心
2021年第4期1094-1114,共21页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:41830319)资助。
