中文摘要：

珠江三角洲平原具有上千年的围垦历史,其土壤发生演变过程深受人为作用影响,开展此区域不同种植年限土壤中铁氧化物形态特征和分布规律的研究,能够揭示人为耕种下土壤发生演变过程。以珠江三角洲平原不同种植年限的土壤剖面为对象,研究了滨海沉积物、河流冲积物和三角洲沉积物发育的土壤及黏粒中全铁、游离铁含量变化及其影响因素。结果表明：随着种植年限的增加,河流冲积物、三角洲沉积物发育土壤中游离铁（Fed）向土体下部淀积深度逐渐增加,黏粒中游离铁（Fe（d（clay）））含量在水耕氧化还原层中呈减小趋势,而滨海沉积物发育的土壤Fed含量及淀积深度均有所减小。随着种植年限的增加,滨海沉积物发育的土壤全铁（Fet）和游离铁（Fed）在黏粒中的富集程度呈增大趋势,而河流冲积物、三角洲沉积物发育的土壤Fet和Fed富集程度逐渐减小。土壤Fed与Fet、黏粒游离铁（Fe（d（clay）））与黏粒全铁（Fe（t（clay）））均呈极显著正相关;全铁富集率（Fe（t（clay））/Fet）、游离铁富集率（Fe（d（clay））/Fed）均与Fe（t（clay））、Fe（d（clay））、黏粒铁游离度（Fe（d（clay））/Fe（t（clay）））呈极显著正相关,与Fet、Fed、土壤铁游离度（Fed/Fet）、黏粒含量呈极显著负相关,且Fe（t（clay））/Fet与Fe（d（clay））/Fed呈极显著正相关,表明土壤铁氧化物在黏粒中的富集以Fed为主,且铁氧化物的富集程度受土壤黏粒含量的影响。

英文摘要：

[Objective] The Pearl River Delta Plain, located in South China, has a more-than- one-thousand-year cultivation history, so that the soil therein has been subjected to impacts of intensive anthropogenic activities in its evolution. The knowledge of how the soil evolves under anthropogenic activities is sure helpful to sustainable utilization and management of the soil resources. Being highly active and geochemically sensitive, iron oxides in soil tend to be affected by any slight change in environmental condition in formation and property, so they are often used as an indicator of soil pedogenic process, and considered as a function of soil genesis and development. Therefore, characterization of soil iron oxides has been one of the major fields of the study on soil genesis. In this study an investigation was performed of characteristics of iron oxides in bulk soil and soil clay relative to cultivation age and affecting factors in the Pearl River Delta Plain, in an attempt to reveal how the soil forms and evolves under anthropogenic cultivation in the region. [ Method] Samples were collected from genetic horizons of the soils derived from marine deposits with cultivation age being 30 a, 100 a, 600 a and 1 000 a, separately, of the soils derived from fluvial deposits with cultivation age being 200 a, 400 a, 900 a and 1 000 a separately and of the soils derived from delta deposits with cultivation age being 50 a, 90 a, 150 a and 350 a, separately, in the Pearl River Delta Plain for analysis of physicochemical properties, and total iron （Fet） , free iron （ DCB-extractable iron, Fed） , ratio of Fed to Fe, （ Fed / Fet ） in bulk soil and clay （ Fea （clay）/Fet （clay）） , Fed sedimentation coefficient （ ratio of Fed in the genetic horizon beneath the surface horizon to Fed in surface horizon ） and enrichment rates of Fet and Fed in clay （Fet -chy）/Fe, and Fed （clay）/Fed ） - [Result] Results show that： （ 1 ） Among the soils derived from marine deposits, those, 30 a in cultivation