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Assessing spatial variability of C, Fe and Al concentrations in gleyed soils as a means of understanding the stabilisation of soil organic carbon.

评估土壤中 C、Fe 和 Al 浓度的空间变异性，作为了解土壤有机碳稳定性的一种手段。

基本信息

批准号：
NE/G010102/1
负责人：
Clare Wilson
金额：
$ 8.1万
依托单位：
University of Stirling
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FG010102%2F1
关键词：
Assessing spatial variability Fe Al

项目摘要

Globally soils store more carbon than the atmosphere and vegetation combined; this carbon could otherwise be present as greenhouse gases in the atmosphere. Maintaining soil conditions such that they continue to store organic carbon is very important; however, our understanding of how carbon is stored in soils is incomplete. It is thought that certain minerals in the soil, including iron and aluminium oxides, help stabilise organic carbon preventing microbial attacking and its conversion to carbon dioxide or other green house gases. However, it is not clear how exactly iron oxides and organic carbon interact to prevent organic carbon being metabolised by soil organisms. Gleyed soils occupy ca. 900 million ha globally, and are soils that are subject to permanent or temporary waterlogging; this results in distinctive patterns whereby iron oxides are concentrated in some areas and are absent from others. This spatial patterning of iron oxide minerals makes these soils useful for researchers trying to understand the mechanisms of organic carbon stabilisation. Bulk chemical analysis can provide valuable information about total concentrations of organic carbon, iron, and aluminium, and about the nature of the organic matter that is present, but these traditional bulk chemical approaches do not provide information about the small scale spatial differences in carbon and iron oxide concentration. Microscopic analysis of such soils would allow us to directly examine the concentration of iron oxides and organic carbon, thus helping to elucidate the mechanisms of organic carbon stabilisation by iron oxides in soil over small distances. However, the microscopic scale of these measurements can make it difficult to extrapolate the findings to whole soil profiles and larger soil volumes. The proposed pilot project aims to bring together for the first time specific bulk and microscopic analytical techniques in order to study the mechanisms of organic carbon stabilisation in gleyed (waterlogged) soils. Undisturbed and bulk samples will be taken from soils at Harwood Forest, Northumberland with contrasting drainage conditions. Bulk samples will be analysed to determine background soil conditions, total concentrations of carbon, iron and aluminium oxides, and the nature of the organic matter present. A sequential series of increasingly aggresive extractions will be carried out on the soils, and the solution recovered after each extraction will be analysed again to determine the nature of the organic carbon bound to different types of iron oxide minerals (weakly crystalline and strongly crystalline). Undisturbed blocks of soil will be stabilised in resin, sliced and lapped to create thin sections which can be examined using petrological and electron microscopes. Areas of iron oxide concentration and depletion can be mapped and the ratio of Fe, Al, O, and C determined across cm, mm and micrometer scales. These sections will then be subjected to the same treatments as the bulk soils in order to remove iron, aluminium and organic carbon associated with first weakly and then strongly crystalline iron oxides. This novel approach will add to our understanding of how carbon is stabilised in gleyed soils and how sensitive it might be to changing soil conditions as a result of climate change. This will provide valuable information for modellers of soil carbon turnover. The project will also refine the analytical methods available to researchers which will be useful for the study of similar processes in different soils; this could be particularly useful for the study of carbon storage and soil processes in agricultural systems, which make a significant contribution to global greenhouse gas emissions.

在全球范围内，土壤储存的碳比大气和植被的总和还要多；否则，这些碳可能会以温室气体的形式存在于大气中。保持土壤条件，使其继续储存有机碳是非常重要的；然而，我们对碳是如何储存在土壤中的理解是不完整的。人们认为，土壤中的某些矿物质，包括铁和铝氧化物，有助于稳定有机碳，防止微生物攻击并将其转化为二氧化碳或其他温室气体。然而，目前还不清楚氧化铁和有机碳到底是如何相互作用，以防止有机碳被土壤生物代谢的。全球潜育化土壤约占9亿公顷，是永久性或临时性内涝的土壤；这导致了独特的模式，即氧化铁在一些地区集中，而在其他地区则不存在。氧化铁矿物的这种空间模式使这些土壤对试图了解有机碳稳定机制的研究人员很有用。整体化学分析可以提供关于有机碳、铁和铝的总浓度以及存在的有机物的性质的有价值的信息，但这些传统的整体化学方法不能提供关于碳和氧化铁浓度的小范围空间差异的信息。对这类土壤的微观分析将使我们能够直接检测氧化铁和有机碳的浓度，从而有助于阐明土壤中氧化铁在小距离内稳定有机碳的机制。然而，这些测量的微观尺度可能使其难以将结果外推到整个土壤剖面和更大的土壤体积。拟议的试点项目旨在首次将特定的总体和微观分析技术结合在一起，以研究GLEYED(淹水)土壤中有机碳稳定的机制。未受干扰的大量样本将从诺森伯兰郡哈伍德森林的土壤中提取，排水条件截然不同。将对大量样本进行分析，以确定背景土壤条件、碳、铁和铝氧化物的总浓度，以及存在的有机物的性质。将在土壤上进行一系列越来越强烈的提取，每次提取后回收的溶液将再次进行分析，以确定与不同类型的氧化铁矿物(弱结晶和强结晶)结合的有机碳的性质。未受干扰的土块将在树脂中稳定，切片并重叠，形成可以用岩石学和电子显微镜检查的薄片。可以绘制氧化铁浓度和耗竭区域的地图，并确定跨厘米、毫米和微米尺度的铁、铝、氧和碳的比率。然后，这些部分将受到与散装土壤相同的处理，以便首先去除与弱结晶氧化铁有关的铁、铝和有机碳，然后再去除与强结晶氧化铁有关的有机碳。这一新的方法将增加我们对GLEYED土壤中碳是如何稳定的，以及它对气候变化导致的土壤条件变化的敏感性的理解。这将为土壤碳周转的模型者提供有价值的信息。该项目还将完善研究人员可用的分析方法，这将有助于研究不同土壤中的类似过程；这可能对研究对全球温室气体排放有重大贡献的农业系统中的碳储存和土壤过程特别有用。