Differences in chemical composition of soil organic matter in natural ecosystems from different climatic regions - A pyrolysis-GC/MS study

Soil organic matter (SOM) is a key factor in ecosystem dynamics. A better understanding of the global relationship between environmental characteristics, ecosystems and SOM chemistry is vital in order to assess its specific influence on carbon cycles. This study compared the composition of extracted SOM in 18 topsoil samples taken under tundra, taiga, steppe, temperate forest and tropical forest using pyrolysis-GC/MS. Results indicate that SOM from cold climates (tundra, taiga) still resembles the composition of litter, evidenced by high quantities of levosugars and long alkanes relative to N-compounds and a clear odd-over-even dominance of the longer alkanes. Under temperate conditions, increased microbial degradation generally results in a more altered SOM chemistry. SOM formed under temperate coniferous forests shows an accumulation of aromatic and aliphatic moieties, probably induced by substrate limitations. Tropical SOM was characterized by an SOM composition rich in N-compounds and low in lignins, without any accumulation of recalcitrant fractions (i.e. aliphatic and aromatic compounds). Lignin composition moreover varies according to vegetation type. Results were validated against 13 new samples. The humic signature of topsoil organic matter formed under different biomes indicates a dominating effect of (i) SOM input composition related to vegetation, and (ii) SOM breakdown reflecting both climate and input quality. No evidence was found for a chemically stabilized SOM fraction under favorable decomposition conditions (temperate or warm climate with broadleaved vegetation).     

中亚干旱区土壤地球化学和环境

首先论述了中亚干旱区的土壤形成环境和土壤地球化学特点,剖析了该区广泛分布的盐渍土、石膏土和碳酸盐土的成土特点和地球化学元素分异规律;根据当前土地利用中面临的土壤退化和环境问题,提出了若干因地制宜的利用土壤资源战略的建议。同时,还对加强我国和中亚5国学术交流,促进互利共赢提出了建议。     

Stoichiometry of base cations and silicon during weathering of a deep soil profile derived from granite

Evaluation of the stoichiometry of base cations (BCs, including K⁺, Na⁺, Ca²⁺, and Mg²⁺) and silicon (Si) (BCs:Si) during soil mineral weathering is essential to accurately quantify soil acidification rates. The aim of this study was to explore the differences and influencing factors of BCs:Si values of different soil genetic horizons in a deep soil profile derived from granite with different extents of mineral weathering. Soil type was typic acidi-udic Argosol. Soil samples were collected from Guangzhou, China, which is located in a subtropical region. To ensure that the BCs and Si originated from the mineral weathering process, soil exchangeable BCs were washed with an elution treatment. The BCs:Si values during weathering were obtained through a simulated acid rain leaching experiment using the batch method. Results showed that soil physical, chemical, and mineralogical properties varied from the surface horizon to saprolite in the soil profile. The BCs:Si values of soil genetic horizons during weathering were 0.3-3.7. The BCs:Si value was 1.7 in the surface horizon (A), 1.1-3.7 in the argillic horizon (Bt), and 0.3-0.4 in the cambic (Bw) and transition (BC) horizons, as well as in horizon C (saprolite). The general pattern of BCs:Si values in the different horizons was as follows: Bt > A > Bw, BC, and C. Although BCs:Si values were influenced by weathering intensity, they did not correlate with the chemical index of alteration (CIA). The release amounts of Si and BCs are the joined impact of soil mineral composition and physical and chemical properties. A comprehensive analysis showed that the BCs:Si values of the soil derived from granite in this study were a combined result of the following factors: soil clay, feldspar, kaolinite, organic matter, pH, and CIA. The main controlling factors of BCs:Si in soils of different parent material types require extensive research. The wide variance of BCs:Si values in the deep soil profile indicated that H⁺ consumed by soil mineral weathering was very dissimilar in the soils with different weathering intensities derived from the same parent material. Therefore, the estimation of the soil acidification rate based on H⁺ biogeochemistry should consider the specific BCs:Si value.     

出生缺陷高发区土壤微量元素含量特征的空间信息分析

    从土壤元素含量分布与出生缺陷发生率高低的相关性入手,探讨出生缺陷高发区土壤元素含量的异常特征,为筛选诱发出生缺陷的敏感因子提供科学依据和新的途径.选取出生缺陷高发的山西省中阳和交口两县为研究区,根据流行病调查路线和村镇,逐村采集土壤样品,分析测定土壤样品中Al、As、Ca、Cu、Fe、K、Mg、Mo、Na、Ni、Pb、Se、Sn、Sr、V、Zn等16种元素含量.运用ArcGIS 9.0软件,绘制研究区内96个采样点的出生缺陷发生率和土壤中16种元素含量分布的专题图,并进行Kriging插值和叠加分析.结果显示,出生缺陷发生率高低的空间变异趋势与土壤元素含量分布趋势具有一定的相似性.其中元素V、Se、Mo、As、Mg、Na含量与出生缺陷发生率变化的空间相关性较大.土壤中V、Se的低含量和Mo、As的高含量可能是造成出生缺陷高发的原因.说明土壤元素含量异常与出生缺陷发生率之间存在相关关系.     

典型城市城郊土壤重金属含量对比研究

选取成都经济区内成都、德阳、蒲江彭山3类典型城市作为研究对象,对其城郊土壤中Cd,Hg,As,Zn,Cr,Cu,Pb 7种重金属元素含量作了对比研究.与国家土壤二级质量标准比较,成都、德阳、彭山蒲江Cd含量均超标,超标率分别为11.67%,70.67%,39.00%,彭山蒲江Cr含量超标,超标率为20.25%,其它元素含量均未超标.比较3类不同城市城郊土壤重金属含量.成都城郊Hg,As,Zn,Pb含量最高,Cd,Cr含量相对最低;德阳Cd,Cu最高;蒲江和彭山Cr相对最高,Hg,As,Zn,Cu,Pb含量则相对最低.与国内其他城市比较,成都、德阳城郊土壤Hg含量,彭山蒲江、德阳Cr含量在全国处于较高水平;成都的As,Cd含量,德阳的Cd,Zn含量,蒲江彭山的Hg,As,Zn,Pb含量处于全国较低水平.     

淮河上游全新世黄土-古土壤序列元素地球化学特性研究

在野外考察研究的基础上,对河南禹州全新世风成黄土-古土壤剖面系统采样,利用X-荧光光谱仪测定了常量元素和微量元素的含量及其变化,并与磁化率曲线、粒度变化曲线对比分析发现:常量元素氧化物比值钾钠比、残积系数和以Rb为代表的微量元素含量等随剖面层次呈规律性变化,即在古土壤层(S0)中含量最高,表土层(MS)中次之,在黄土层(L1、Lt、L0)中最低。硅铝率和Sr的含量表现出相反的变化规律。表明在全新世古土壤层和表土层形成时期,气候温暖湿润,成壤作用和次生粘化作用较强;在黄土堆积时期,气候比较干旱,沙尘暴频繁,成壤作用微弱。这些化学参数与磁化率曲线可以进行对比,表明成土过程中元素的迁移变化受全新世以来气候变化和成壤环境变化的控制。与黄土高原腹地的洛川剖面相比,淮河上游禹州剖面中绝大多数常量元素的含量较高,而绝大多数微量元素的含量偏低,磁化率也显著偏低,绝对值差别很大,粒度组成当中细沙成分含量很高,这说明淮河上游黄土物质来源与黄土高原地区明显不同。联系全新世时期黄河频繁泛滥、改道、沉积与黄淮平原盛行东北风形成流沙地的事实,认为淮河上游的黄土是黄河泛滥沉积物质经过风沙活动改造,由东北风力系统搬运而来的近源粉尘堆积,再经过就地风化或者成土改造而形成。     

西天目山自然保护区森林土壤的地球化学特征

本文从土壤地球化学角度探讨西天目山自然保护区森林土壤的发育演化。在南坡自上至下挖掘土壤剖面8个,分层采样,带回室内作理化分析。结果表明,粘粒明显在心土层淀积,SiO_2、Fe_2O_3与K_2O均有在表土层相对积聚的迹象。心土层的粘粒硅铝率较表土层小。自高海拔至低海拔均有SiO_2的淋失,且淋失量比较接近,亦在不同气候条件下脱硅程度的一致。     

海南二甲金矿戈枕韧性剪切带的构造地球化学研究

戈枕韧性剪切带的变形过程中，岩石发生了体积亏损，产生了构造岩流体对岩石的浸滤作用，导致岩石中ＳｉＯ２和碱质的流失；随变形作用的加强，岩石中轻稀土元素的含量显著降低，轻、重稀土元素间发生了一定的分馏作用．另外，构造环境的变化不仅直接控制着包裹体气液成份的变化，而且使包裹体的氢、氧同位素，岩石的硫、铅同位素组成间产生了明显的分异作用     

典型小城市土壤重金属空间异质性及其风险评价—以临安市为例

目的了解石家庄市区及周边土壤中的铅元素(Pb)在2004年至2013年10年内的空间分布变化情况。方法分别在2004和2013年,大密度采集石家庄市及周边区县表层(0 ~ 20 cm)土壤样品,测定Pb含量;统计对比10年间Pb元素的基本参数数据;利用ArcGIS 9.3软件进行空间分析,对比2个年份Pb的空间分布变化;利用地累积指数法评价2个年份的Pb污染状况。结果(1) 2004和2013年石家庄市区及周边区县土壤Pb含量均值变化较小,分别为23.04和24.31 mg/kg,但最大值和变异系数变化较大,最大值从59.50 mg/kg增长到82.50 mg/kg,变异系数从20.23 %增长到23.45 %。(2)从2004到2013年,Pb的低含量土壤面积在缩小,高含量区域增加。显著低值区和低值区面积从545.10 km²减少到388.08 km²,高值区和显著高值区面积从545.10 km²增长到594.00 km²。(3)研究区Pb污染状况相对较轻但有所发展,2004年主要在石家庄市区存在轻度污染,但2013年时,正定新区出现了少量的中度污染,轻度污染在郊县地区也有所扩大。结论石家庄市区及周边土壤Pb的分布与当地主要经济建设活动有密切联系,Pb分布在时间序列上的变化反映了石家庄10年间的经济社会变化。     

模拟酸雨淋溶下不同母质发育雏形土矿物风化中的盐基离子与硅计量关系

土壤矿物风化过程中释放的盐基离子(BC)与硅(Si)的比值(BC︰Si)是定量评估土壤矿物风化对土壤酸化过程缓冲作用的基础,是准确估算当前环境下土壤酸化速率的依据。本研究以云母片岩、片麻岩和安山岩3种母质发育的湿润雏形土为研究对象,测定了其土壤物理、化学和矿物学性质。通过洗脱实验除去土壤交换性盐基以消除土壤胶体吸附的交换性盐基离子对矿物风化计量关系的影响,再利用模拟酸雨淋溶实验,采用Batch方法获取3种不同母质发育土壤的盐基离子和硅的释放量,进一步估算BC︰Si值。结果表明,由于母岩不同,土壤黏粒、pH、有机质、交换性盐基(K⁺、Na⁺、Ca²⁺和Mg²⁺)、阳离子交换量(CEC)和土壤矿物含量存在差异。在模拟酸雨淋溶实验条件下,未洗脱盐基土壤的BC︰Si值为洗脱盐基土壤的3倍以上,因此只有洗脱土壤交换性盐基才能获得来自风化过程的BC︰Si值。同一母质发育土壤的腐殖质表层(Ah)BC︰Si最小,母质层(C)最大。不同母质发育土壤的BC︰Si值表现为：片麻岩>云母片岩>安山岩,土壤中斜长...