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1.
Pasture degradation effects on soil quality indicators at different hillslope positions in a semiarid region of western Iran 总被引：1，自引：0，他引：1
Shamsollah Ayoubi Nazanin Emami Nasrin Ghaffari Naser Honarjoo Kanwar L. Sahrawat 《Environmental Earth Sciences》2014,71(1):375-381
A study was made to determine the influence of pasture degradation on soil quality indicators that included physical, chemical, biological and micromorphological attributes, along the hillslope positions in Chaharmahal and Bakhtiari province, western Iran. Soil samples from different slope positions were collected from 0 to 30 cm depth for physical and chemical properties and from 0 to 15 cm depth for biological properties at two adjacent sites in the two ecosystems: natural pasture and cultivated land. Soil quality indicators including bulk density, mean weight diameter, soil organic carbon (SOC), particulate organic material (POM) in aggregate fractions, total nitrogen, available potassium, available phosphorus, cation exchange capacity, soil microbial respiration (SMR) and microbial biomass C and N were determined. The results showed that SOC decreased cultivation from 1.09 to 0.77 % following pasture degradation. The POM decreased by about 19.35 % in cultivated soils when compared to natural pasture; also, SMR and microbial biomass C and N decreased significantly following pasture degradation. Furthermore, aggregate stability and pore spaces decreased, and bulk density increased in the cultivated soils. Overall, our results showed that long-term cultivation following pasture degradation led to a decline in soil quality in all selected slope positions at the site studied in the semiarid region. 相似文献
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Soil water conservation is essential to the sustainability of sandy farming. In this paper, long-term observation of soil water, dry soil thickness and soil chemical changes are evaluated at eight locations in sandy soil. This paper subdivides the sandy lands and deserts of China into three climate zones: arid (hyperarid and extremely arid), semiarid, and humid (subhumid and subtropical humid), with respect to the bioclimatic zone, aridity, soil water content, and soil chemical characteristics. The water movement conditions, and chemical variations in each zone are analyzed. The paper also estimates the spatial and temporal correlation function of arid soil thickness and soil moisture. Sandy soils organic matter content, CaCO3 content, soluble salts content are investigated. Afforestation and selection of tree species in different sandy areas are suggested to regulate sandy land soil moisture. Sandy land in China can be divided into the four sand stabilization regions according to the shifting sand conditions and the techniques advanced: regions I, II, III, and IV. These results have important implications for remote sensing of soil moisture and soil organic carbon, and soil moisture parameterization in climate models. 相似文献
4.
吉林西部不同土地利用类型的土壤有机碳垂向分布和碳密度 总被引：3，自引：0，他引：3
土壤碳库在陆地生态系统碳循环中起着关键性的作用。在对吉林西部进行为期6年（2004－2009年）的环境调查基础上,采集了217个土壤剖面,获取了2 170个土壤样品的平均容重、含水率和有机碳含量,分析了不同土地利用类型下土壤有机碳（SOC）的垂向分布特征、原因和机理。结果表明：不同土地利用类型的土壤有机碳垂向分布表现出截然不同的特征,大致可分为“下降型”、“上升型”和“不变型”3种。呈下降型的草地、农田、湿地等SOC含量主要富集在0~30 cm耕作层,并随深度增加而快速下降;滩地为上升型,良好的水文条件和相对茂盛的植物为有机质提供了有利条件;不变型包括盐碱地、林地和沙地,SOC含量处于全区最低水平。不同土地利用类型的土壤有机碳密度差异很大,从大到小依次为水田、草地、旱田、湿地、退化草地、滩地、林地、沙地、盐碱地,其中水田为（169.25±17.70） t/hm2,盐碱地为 （26.50±10.00） t/hm2。植被生物量和土壤理化性质是影响土壤有机碳含量的主要因素。 相似文献
5.
Michel Brossard Gustavo Adolfo de Freitas Fregonezi Maria de Fátima Guimarães Cristiane de Conti Medina Amarildo Pasini Lourival Vilela Miguel Angel Ayarza 《Comptes Rendus Geoscience》2012,344(1):41-49
Ferralsols are characterized by poorly-defined horizons, weak macrostructure and strong development of a fine granular structure comprising subangular micro-aggregates. In this study, the morphological and physical modifications caused by earthworm activity in a clayey ferralsol were analysed. After describing soil structures, undisturbed samples were taken for evaluating aggregates and determining clod bulk density and particle density. Soil water retention properties were measured and an inventory of soil invertebrate macrofauna was created. The structural and porous transformations were due to aggregates created by earthworm activity. Changes in bulk density can be associated with pore modifications caused by a change in the proportions of aggregate types, and a notable reduction of total porosity was measured, tending to increase soil volume with dense aggregates. Structural modifications affected the topsoil down to 0.5 m and water retention between −1 and −33 kPa, the principal water compartment of these soils. 相似文献
6.
H. G. Wilshire J. K. Nakata Susan Shipley Karen Prestegaard 《Environmental Geology》1978,2(5):295-319
The impacts of off-road vehicles on vegetation and soil were investigated at seven representative sites in the San Francisco
Bay area. Plant cover of grass and chaparral (with shrubs to 4 m tall) have been stripped by the two- and four-wheel vehicles
in use. Impacts on loamy soils include increased surface strength (as much as 275 bars), increased bulk density (averaging
18%) to depths of 90 cm or more, reduction of soil moisture by an average 43% to 30 cm depths, greatly reduced infiltration,
extension of the diurnal temperature range by as much as 12°C, and reduction of organic carbon by an average 33% in exposed
soils. Very sandy soils respond similarly to vehicular use except that moisture is increased and surface strength of beach
sand is decreased.
These physical and chemical impacts reduce the land's capability of restoring its vegetative cover, which in turn adversely
affects animal populations. Both the loss of plant cover and the physical changes caused by vehicles promote erosion. Measured
soil and substrate losses from vehicular use zones range from 7 to 1180 kg/m2. The estimated erosion rate of the Chabot Park site exceeds the rate of erosion considered a serious problem by a factor
30, it exceeds United States Soil Conservation Service tolerance values by a factor of 46, and it exceeds average San Francisco
Bay area erosion rates by a factor of 17. The resulting soil losses are effectively permanent. Neither the increased sediment
yield nor the increased runoff is accomodated on the sites of use, and both are causing adverse effects to neighboring properties. 相似文献
7.
为了探究高级氧化技术对土壤中有机氯代烃的氧化降解作用,为ISCO（in situ chemical oxidation）技术体系提供重要的理论依据和数据支撑,考察了热活化过硫酸盐（persulfate,PS）氧化降解不同类型土壤（砂类土壤、黏土类土壤）中挥发性氯代烃污染物（三氯乙烯（TCE）、三氯乙烷（TCA）、顺式-1,2-二氯乙烯（cis-1,2-DCE）、1,2-二氯乙烷（1,2-DCA））的效能;同时,通过硫酸盐与土壤相互作用过程研究,探究了不同土壤介质中有机质和无机组分在过硫酸盐消耗中所占比例。结果表明：在50℃时,热活化过硫酸盐可有效降解土壤中1,2-DCA、cis-1,2-DCE、TCA和TCE,砂类土壤介质中4种氯代烃降解效果依次为25%、89%、5%和61%,黏土类土壤介质中4种氯代烃降解效果依次为35%、86%、8%和63%;4种氯代烃的降解效果从高到低顺序依次为cis-1,2-DCE、TCE、1,2-DCA、TCA,砂类土壤中的氯代烃总体降解效果优于黏土类土壤中氯代烃的降解效果。另外,土壤中过硫酸盐氧化降解氯代烃反应研究发现,砂类和黏土类土壤介质组分中有机质消耗率分别为81.3%和72.6%,铁元素消耗率分别为80.5%和38.6%,表明土壤介质组分与过硫酸盐发生了氧化还原反应,从而导致过硫酸盐自身的大量消耗。由此可知,土壤介质中的有机质、铁元素等矿物质均参与过硫酸盐的消耗过程,且土壤有机质、铁元素与氯代烃之间在消耗过硫酸盐反应上存在竞争关系,土壤组分过多地消耗了过硫酸盐,导致了氯代烃的氧化降解效率较低。因此,针对实际有机氯代烃污染场地,采用过硫酸盐氧化技术进行修复时,过硫酸盐的实际投加量要远高于化学计量值,需充分考虑到土壤组分对过硫酸盐自身的消耗作用。 相似文献
8.
Disturbances have the potential to reduce soil water and nutrient retention capacity by decreasing soil organic matter (SOM), which is particularly true for sandy soils characterized by an inherent low capacity to retain nutrients and water. To restore degraded areas, several works have shown positive effects of organic matter inputs on soil properties and plant growth. Despite these promising results, it is still unclear how organic matter inputs and plant growth modify the balance between soil nutrient and water supply. The objectives of the present work were (1) to evaluate the effects of biosolids compost and municipal compost addition on plant available water (PAW), soil moisture and soil temperature in a burned sandy soil of NW Patagonia (Argentina), and (2) to relate PAW and soil moisture with bulk density, soil organic carbon, nutrient availability (inorganic and potential mineralized nitrogen (N), extractable phosphorous) and aboveground phytomass. An experiment with excised vegetation and watering was also conducted. Compost application increased SOM, but it was insufficient to increase PAW. The increase in potential mineralized N in the amended soils indicated that during moist periods (and adequate temperatures), N uptake was increased, enhancing plant growth. As a consequence, higher plant water consumption in amended treatments resulted in lower soil moisture than in non-amended plots during the vegetative growth period that coincides with decreasing precipitation. Results indicate that a relatively high dose of compost (40 Mg ha?1) applied to a sandy soil, contributed to increase nutrient availability and consequently, aboveground phytomass and water consumption. 相似文献
9.
由于黏性土表面带有丰富的负电荷,孔隙水溶液化学状态的变化对黏性土的物理力学特性存在明显影响。随着化学-力学耦合的相关岩土工程问题日益突出,进行有效的化学-力学耦合行为的数值分析评价显得尤为重要。因此,建立一个简单有效的考虑化学-力学耦合的本构模型是非常关键的。基于传统的修正剑桥模型,提出了一个简单的化学-力学耦合模型。该模型采用渗透吸力π描述孔隙水的化学状态,建立了前期屈服应力,临界状态线斜率M和弹性刚度与渗透吸力π之间的关系式,从而实现了模型对盐溶液饱和黏性土的变形和强度特性的有效模拟。通过与试验数据的对比和分析,说明该模型能有效地模拟孔隙盐溶液饱和黏性土的等向压缩行为、 状态下压缩行为以及 状态下化学-力学循环加载行为。此外,通过对黏性土三轴压缩试验的模拟,说明该模型能反映黏性土三轴应力状态下的基本力学特征。 相似文献
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天然沉积中间土的力学特性研究 总被引：3，自引：2，他引：1
长江口北岸天然沉积土主要由粉粒和细砂粒组成,其渗透系数介于10-7～10-3 cm/s之间,既不属于完全排水的砂性土,也不属于完全不排水的粘性土,针对这样的天然沉积中间土的我国研究并不多见。通过大量的物理力学试验,探讨了天然沉积中间土的物理力学性状,结果表明天然沉积中间土具有类似于软粘土的物理性质,但原位静力触探试验显示其天然沉积中间土的原位强度却与天然含水量分布在塑限附近的硬粘土差不多。研究结果亦表明颗粒分布对天然沉积中间土的原位强度有较大的影响。同时采用灰理论中的关联度分析,对这类中间土物理状态指标与力学特征指标间相关性进行了分析,认为孔隙比用于亚砂土稠度划分,含水比用于亚粘土、粘土稠度划分更加合理 相似文献
12.
E. A. Elkhatib Ph.D. A. M. Mahdy Ph.D. M. E. Saleh Ph.D. N. H. Barakat M.Sc. 《International Journal of Environmental Science and Technology》2007,4(3):331-338
Desorption of Cu and low molecular weight dissolved organics are the primary factors that impact fate and transport of Cu in soils. To improve predictions of the toxicity and threat from Cu contaminated soil, it is critical that time-dependent desorption behavior be understood. In this paper, the effect of organic ligands citrate, malate, and succinate on the kinetics of Cu desorption from contaminated soils varying widely in soil characteristics was investigated at 25° C and the soils used were referred to as clay, calcareous and sandy soils. The amount of Cu released by the used organic ligands varied greatly with physicochemical properties of the soils. The rate of Cu release by different extractants was in the order citric > malic > succinic, which was consistent with the stability constants of Cu complexes with these ligands. The modified Freundlich and the Elovich and Parabolic diffusion models were used to describe dsorption of Cu2+ from the three studied soils as affected by the organic ligands. All of the models fit the data well with correlation coefficients ranging from 0.83 to 1.00 (P < 0.01). Each Model has a set of assumptions for the different physical and chemical properties of the systems to which they are being applied. The uses of these equations yield different magnitudes for the calculated variable, but the relationships between the soil + organic ligands and their effect (i.e., increase or decrease) on these variables are the same. Such information is critical, since Cu is used in a variety of industrial and manufacturing processes and is one of the most common contaminants found at hazardous waste sites. 相似文献
13.
Selenomethionine (SeM) is an organic toxicant that is present in seleniferous environments. No kinetic data is yet available
regarding SeM reactions in coal mine environments, where selenium (Se) toxicity is a potential concern. A kinetic study was
conducted on two reclaimed coal mine soils (Typic Torriorthents) from Wyoming having sandy and clayey textures. Four levels
of SeM treatments (0, 50, 100 μM, and plant amendment from the mine vegetation) were reacted with the soils for 4, 7, 14,
28, 42, 56, and 84 days to characterize the kinetic behavior of overall SeM disappearance from soil solutions. Detection of
SeM in soil solutions at the control level (0 μM SeM) indicated occurrence of indigenous SeM in the soils. In the plant-amended
soil solutions, much greater concentrations of SeM were observed as compared with the soil-only systems. This indicated the
plant material was a more potential source of SeM than the mine soils. A time-dependent loss in solution SeM concentrations
was observed for both soils under 0, 50, 100 μM SeM treatments. For the soil-plant mixtures, the solution SeM concentration
increased initially, reached a maximum after 14 days, and then decreased thereafter. In the plant-amended soil solutions,
SeM concentrations at all time intervals were higher for the sandy as compared to the clayey soil. At 50 and 100 μM SeM treatments,
the solution pH was linearly related to the percentages of SeM disappeared from the solutions; greater percentage of SeM was
removed from solutions at comparatively lower pH levels, which was ≥90% at pH 7.7 for both soils. Solution SeM concentrations
decreased exponentially with time following first-order kinetic reactions. Under all applications (except for the control),
C
0 (SeM concentration at t=0) values for the sandy soil were greater than those determined for the clayey soil, indicating higher solution SeM availability
for the former and more SeM retention by the latter at t=0. Comparison of C
0 in controls (0 μM SeM addition) suggested greater indigenous SeM in the clayey soil. For both soils, C
0 values under different treatments followed the order, (soil+100 μM)>(soil+50 μM)>(soil+0 μM). The specific reaction rate
constants (K
r) of SeM for both soils were similar (0.031 and 0.029 day–1 for sandy and clayey soils, respectively); low K
r values indicated that SeM loss from our reclaimed coal mine soil solutions would follow rather slow kinetics. The half-life
(t
0.5) of SeM varied from 15 to 55 days depending on treatment level. The knowledge obtained from this study should contribute
in developing time-based Se reclamation strategies in coal mine environments.
Received: 18 September 1995 · Accepted: 28 December 1995 相似文献
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桂林毛村岩溶区自然植被土壤团聚体中腐殖质组成初步研究 总被引：1，自引：0，他引：1
探索土壤有机碳物理保护与化学保护的关系,有助于揭示土壤固碳和培肥机理,明确不同粒级团聚体和不同腐殖物质组分对土壤固碳和肥力的贡献。本研究对岩溶区自然植被土壤团聚体中腐殖质含量进行了研究,结果表明:(1)灌丛和林地土壤团聚体中有机碳含量总体上均表现为随着土层深度的增加逐渐下降,而在不同土层深度随着团聚体粒径范围的变化则有机碳含量的变化规律则不同,无明显一致的规律;(2)两种土地利用方式各粒径团聚体中胡敏酸和富里酸均比全土小。这可能是由于在湿筛分离团聚体的过程中溶于水的那部分胡敏酸和富里酸成分被损失掉;(3)各腐殖质组分随着团聚体粒径范围的减小在两种自然植被上均无明显一致的规律,但胡敏酸和富里酸总量则基本表现为随着团聚体粒径范围的减小而逐渐升高,即在0.25mm和0.5~0.25mm粒径范围团聚体中最大;(4)两种自然植被土壤各土层中和各团聚体中胡敏酸/富里酸(HA/FA)基本上表现为小于1,这主要是因为研究区温度相对较高,湿度较大,植被覆盖度大,微生物降解作用强所致。 相似文献
16.
《Applied Geochemistry》1997,12(3):243-254
Column flow-through experiments reacting wastewater solutions with sandy loam soil samples were performed to study heavy metal attenuation by two soils with different physical and chemical properties. Reacted soil columns were leached with synthetic acid rain to study the mobility of attenuated heavy metals under leaching conditions. This study demonstrates that cation exchange, surface adsorption, chelation with solid organic material, and precipitation were the important attenuation mechanisms for the heavy metals (Cd, Cr, Cu, Mo, Ph, and Zn). Adsorption on soil hydrous oxide surfaces was the primary attenuation mechanism for Cd and Zn in both soils, and for Cu in a soil with low organic matter content. Wastewater solution pH is also an important factor that influences the retention of heavy metals. Cadmium, Cu, Cr, and Zn became mobile after prolonged application of spiked wastewater solution, either through saturation of soil adsorption sites or due to decreasing pH. Only Cr, Pb, and Mo, which are attenuated primarily through precipitation, show significant net retention by soil. Acid rain water removed heavy metals left in the column residual pore solution and weakly sorbed heavy metals in the soils, and has the ability to mobilize some strongly attenuated heavy metals, especially when the soil organic matter content is high. The results have important applications in predicting heavy metal mobility in contaminated soil, the disposal of acid mine drainage, and assessing the risks of landfall leachate leakage. 相似文献
17.
Evangelos I. Stavridakis 《Geotechnical and Geological Engineering》2006,24(2):379-398
Major geotechnical problems in construction involving silty–clayey soils are due to their low strength, durability and high
compressibility of soft soils, and the swell–shrink nature of the overconsolidated swelling soils. Confronted with these problems,
a suitable ground improvement technique is needed, for deep excavations in soft clays, for stability, durability and deformation
control. Cement-stabilization is one of the alternatives. An increase in strength and durability, reduction in deformability
are the main aims of this method. Conventional cement-stabilization methods are used mainly for surface treatment. However,
the use of cement has recently been extended to a greater depth in which cement columns were installed to act as a type of
soil reinforcement (deep cement–soil mixing and cement jet grouting). In situ engineering properties of these silty–clayey soils are often variable and difficult to predict. For this reason cement-stabilization
methods have a basic target to control the aforementioned engineering properties of these clays so that the properties of
a silty–clayey soil become more like the properties of a soft rock such as clayey shale or lightly cemented sandstone. So
cement-stabilization of these soils is essential to control their engineering properties and to predict their engineering
behaviour for construction. In an effort to predict, classify and study the suitability of silty–clayey soils for cement-stabilization
both slaking and unconfined compressive strength tests were carried out on clayey–sand mixtures consisted of two types of
clays, kaolin and bentonite. Finally diagrams were prepared to study the variation of slaking and strength due to compaction,
curing time and cement percentage and also to predict areas of efficient cement-stabilization. 相似文献
18.
Sabine Goldberg Scott M. Lesch Donald L. Suarez 《Geochimica et cosmochimica acta》2007,71(23):5750-5762
The constant capacitance model, a chemical surface complexation model, was applied to selenite, Se(IV), adsorption on 36 soils selected for variation in soil chemical properties. The constant capacitance model was able to fit Se(IV) adsorption by optimizing one monodentate Se(IV) surface complexation constant and the surface protonation constant. A general regression model was developed for predicting these surface complexation constants for Se(IV) from easily measured soil chemical characteristics. These chemical properties were inorganic carbon content, organic carbon content, iron oxide content, aluminum oxide content, and surface area. The prediction equations were used to obtain values for the surface complexation constants for four additional soils, thereby providing a completely independent evaluation of the ability of the constant capacitance model to describe Se(IV) adsorption. The model’s ability to predict Se(IV) adsorption was quantitative on one soil and semi-quantitative on three soils. Incorporation of these prediction equations into chemical speciation-transport models will allow simulation of soil solution Se(IV) concentrations under diverse non-calcareous agricultural and environmental conditions without the requirement of soil specific adsorption data and subsequent parameter optimization. 相似文献
19.
The sequestration of terrestrial organic carbon in Arctic Ocean sediments: A comparison of methods and implications for regional carbon budgets 总被引：1，自引：0，他引：1
A variety of approaches have previously been developed to estimate the fraction of terrestrial or marine organic carbon present in aquatic sediments. The task of quantifying each component is especially important for the Arctic due to the regions’ sensitivity to global climate change and the potential for enhanced terrestrial organic carbon inputs with continued Arctic warming to alter carbon sequestration. Yet it is unclear how each approach compares in defining organic carbon sources in sediments as well as their impact on regional or pan-Arctic carbon budgets. Here, we investigated multiple methods: (1) two end-member mixing models utilizing bulk stable carbon isotopes; (2) the relationship between long-chain n-alkanes and organic carbon (ALKOC); (3) principal components analysis (PCA) combined with scaling of a large suite of lipid biomarkers; and (4) ratios of branched and isoprenoid glycerol dialkyl glycerol tetraether lipids (the BIT index) to calculate the fraction of terrestrial organic matter components preserved in Arctic marine sediments.Estimated terrestrial organic carbon content among approaches showed considerable variation for identical sediment samples. For a majority of the samples, the BIT index resulted in the lowest estimates for terrestrial organic carbon, corroborating recent suggestions that this proxy may represent a distinct fraction of terrestrial organic matter; i.e., peat or soil organic matter, as opposed to markers such as n-alkanes or long-chain fatty acids which measure higher plant wax inputs. Because of the patchy inputs of n-alkanes to this region from coastal erosion in the western Arctic, the ALKOC approach was not as effective as when applied to river-dominated margins found in the eastern Arctic. The difficulties in constraining a marine δ13C end-member limit the applicability of stable isotope mixing models in polar regions. Estimates of terrestrial organic carbon using the lipid-based PCA method and the bulk δ13C mixing model approach varied drastically at each site, suggesting that organic matter fractions such as amino acids or carbohydrates may affect bulk organic matter composition in a manner that is not captured in the lipid-based analysis. Overall, terrestrial organic matter inputs to the Chukchi and western Beaufort Seas using the average of the methods at each site ranged from 11% to 44%, indicating that land-derived organic matter plays a substantial role in carbon dynamics in the western Arctic Ocean. 相似文献
20.
文章在分析不同类型的人为土壤形成过程及其特点的基础上研究了人为土壤有机碳含量、分布年龄与同位素组成特征。结果表明,人为土壤中有机碳的含量分布不同于起源土壤或者相应的非人为土壤,主要体现在有机碳含量降低的缓慢和不规则性以及有机碳含量的相对富集。通过计算证明人为土壤的有机碳密度高于相邻土壤或起源土壤。放射性碳测定表明人为土壤中的有机碳年龄较老,说明了有机碳在这些土壤中存在的相对稳定性。土壤有机碳的稳定同位素组成分析表明,土壤中深层的有机碳与现代有机碳来源不同,也表明了土壤中有机碳的稳定存在。文章还分析了人为土壤中有机碳富集和稳定的可能机制,包括物理、化学和生物学机制,认为就有机碳的固定而言,人为土壤是一种具有最佳管理方式的可持续利用的土壤资源 相似文献