季节性冻融作用对土壤吸附稀土元素镧的影响

通过室内模拟,研究冻融作用对土壤理化性质的影响,并分析不同冻融频次对土壤吸附稀土元素镧的影响,探究其影响机制。结果表明,随着冻融频次的增加,土壤pH升降变化幅度不大;有机质在冻融频次为二次时,达到最大值42. 61 g/kg,且随着冻融频次的增加呈现下降趋势;游离氧化铁由7. 67 g/kg下降到3. 62 g/kg后上升到13. 47 g/kg。同时,土壤对稀土元素镧的吸附量随冻融频次的增加而逐渐减小。经过8次冻融,土壤对镧的最大吸附量由1. 89 mg/g下降到1. 09 mg/g,说明冻融作用对土壤吸附稀土元素镧有抑制作用,这与冻融作用改变了土壤的理化性质有关。冻融作用改变了土壤对稀土元素镧的吸附机制,使专性吸附向非专性吸附转变,促进了稀土元素镧向土壤中的解吸和释放,增加了土壤中镧的生态风险。     

季节性冻融作用对土壤吸附稀土元素镧的影响

通过室内模拟,研究冻融作用对土壤理化性质的影响,并分析不同冻融频次对土壤吸附稀土元素镧的影响,探究其影响机制。结果表明,随着冻融频次的增加,土壤pH升降变化幅度不大;有机质在冻融频次为二次时,达到最大值42. 61 g/kg,且随着冻融频次的增加呈现下降趋势;游离氧化铁由7. 67 g/kg下降到3. 62 g/kg后上升到13. 47 g/kg。同时,土壤对稀土元素镧的吸附量随冻融频次的增加而逐渐减小。经过8次冻融,土壤对镧的最大吸附量由1. 89 mg/g下降到1. 09 mg/g,说明冻融作用对土壤吸附稀土元素镧有抑制作用,这与冻融作用改变了土壤的理化性质有关。冻融作用改变了土壤对稀土元素镧的吸附机制,使专性吸附向非专性吸附转变,促进了稀土元素镧向土壤中的解吸和释放,增加了土壤中镧的生态风险。     

冻融作用对土壤中总磷含量的影响

我国对土壤冻融作用研究主要集中在自然环境条件下冻土环境变化。对齐齐哈尔市南郊污水处理厂附近的氧化塘中的冻融土壤进行研究,论述了冻融作用对土壤中总磷含量的影响。研究表明,季节性冻融作用对土壤总磷含量有较大影响。     

冻融作用对土壤中氨氮的影响

我国对土壤冻融作用研究主要集中在自然环境条件下冻土环境变化.本文是对齐齐哈尔市南郊污水处理厂附近的氧化塘中的冻融土壤进行研究,论述了冻融作用对土壤中氨氮的影响.研究表明,季节性冻融作用对土壤氨氮有较大影响.     

温度对不同有机质含量土壤CO_2排放速率的影响

在农田生态系统中,植物通过光合作用固定大气中的CO2,同时土壤微生物活动不断的分解土壤有机质,使其一部分成为土壤腐殖质,另一部分则以CO2形式被释放到大气中,因此,土壤中有机碳储量是进入土壤的植物残体量以及在土壤微生物作用下分解损失量相互作用的结果。这个过程受到气候条件、土壤性质、土地利用方式、耕作制度等人为和自然因素的综合影响。而黑土作为重要的农田土壤,无论是农业生产,还是碳素平衡都起着重要的作用,为了有效管理土壤有机碳库的储量,使土壤有机碳成为大气CO2积累的库而不是排放的源,本试验通过培育东北黑土,设置不同有机质含量和温度条件,测定CO2排放速率的变化,明确单一因素温度对不同有机质含量土壤CO2排放速率的影响。     

漆酶与土壤腐殖质的形成

<正> 腐殖质(Humus)是有机质残体在土壤中通过微生物的作用而新合成的一类高分子化合物。其含量多少,直接关系到土壤肥力的高低,影响农作物的生长。因此,研究土壤腐殖质的形成机制,人为提高土壤腐殖质含量,对农业生产具有十分重要的意义。漆酶不仅存在于生漆中而对漆膜形成具有催干作用,而且还存在于很多生物体中参与很多生物化学过程,如有机质残体的生物降解。本文力图通过讨论土壤腐殖质的形成过程,阐明漆酶在此过程中的重要作用。     

溶解性有机质对土壤中TNT迁移行为的影响

溶解性有机质是环境中广泛存在的有机混合物,对污染物的环境行为具有重要影响,能够通过离子交换、吸附、络合、氧化还原等作用影响各类物质在环境中的迁移转化。近年来,利用溶解性有机质处理环境中的污染物受到越来越多学者的关注。TNT在军事当中的大量使用,造成军事场地环境的污染,并且TNT能够通过皮肤接触、呼吸作用等途径对人体造成伤害。阐述了溶解性有机质的特性和理化性质以及TNT在土壤中的迁移过程。综述了国内外溶解性有机质影响土壤中TNT迁移转化的研究现状,对利用溶解性有机质促进TNT污染场地的修复提出了研究展望。     

土壤溶解性有机质的结构特性对土壤重金属行为的影响

对土壤中溶解性有机质(DOM)的概念、组成及分类进行了系统的介绍,总结了DOM对土壤中重金属的三大影响行为:DOM对重金属溶解和沉淀的影响,对重金属解析-吸附的影响和对重金属生物有效性的影响,并提出土壤中溶解性有机质研究中存在的问题及今后的研究方向.     

影响精喹禾灵在土壤中降解的因素研究

为探索精喹禾灵在不同土壤中降解的影响因素,采用室内模拟降解试验,建立了LC-MS/MS检测土壤中精喹禾灵残留量的方法。分别探究了土壤中以下影响因素:含水率、微生物、有机质对不同土壤中精喹禾灵降解的影响。结果表明:在0.02~2.00 mg/kg添加水平范围内精喹禾灵在土壤中的添加回收率为85.10%~97.81%,相对标准偏差(RSD)为2.81%~3.99%,土壤中持水量越高,微生物越多,有机质含量越多,精喹禾灵在土壤中的降解越快。精喹禾灵在土壤中的降解主要受微生物和有机质含量影响。     

丙环唑土壤降解影响因素研究

建立了高效液相色谱串联质谱(LC-MS/MS)检测土壤中丙环唑的方法。采用室内模拟实验,对不同土壤及含水率、微生物、有机质和pH等因素对丙环唑降解的影响进行了研究。结果表明:土壤中有机质和微生物不是丙环唑在土壤中降解的主要影响因子。含水率和pH对丙环唑的降解产生显著影响,土壤的含水率越高,pH越小,土壤中丙环唑的降解越快。丙环唑在土壤中的降解主要受pH的影响。     

高强度模拟酸雨淋滤珠江三角洲地区潮土的有机质含量变化研究

采用高强度（平均离子强下10年、20年、30年雨量）模拟酸雨淋滤珠江三角洲地区的潮土,用重铬酸钾滴定法测定淋滤后土壤的有机质含量。研究表明：高强度模拟酸雨对土壤有机质含量的影响不大。各层土有机质含量变化最大的为下降13.04%,最小的为-1.33%。     

有机肥料中有机质检测影响因素探讨

有机肥料在农作物生长过程中起着非常重要的作用。通过合理施加有机肥料,可以有效提升土壤肥力,提高农作物的产量和品质。土壤中有机质的含量是判断土壤肥力的重要依据。所以,在农业种植中要特别重视测定有机肥料中有机质的含量。作为检测有机质的一线人员,在检测过程中发现采用不同的标准、方法都会对检测结果产生影响。主要分析了有机肥料中有机质的检测方法以及应该注意的事项。     

影响霜脲氰在土壤中降解的因素研究

建立了超高效液相色谱(UPLC)检测土壤中霜脲氰的方法。分别对贵州、湖南、天津土壤中霜脲氰的降解进行了研究。探讨了土壤中主要因素:有机质、微生物、含水率以及pH值对霜脲氰降解的影响。结果表明:土壤中有机质含量越高,微生物越多,含水率越多,pH越大,霜脲氰在土壤中的降解越快。霜脲氰在土壤中的降解主要受pH值的影响。     

Problems with and local solutions for organic matter management in Vietnam

Soil organic matter plays a major role in sustainable agricultural development in Vietnam. A general soil evaluation shows that the content of organic matter in most soil units in Vietnam ranges between 0.5 to 3.0% soil organic matter (in the A and B horizon only) with lower levels especially on sloping land. Most upland soils (70% that contain ≤ 2% soil organic matter) are in danger due to imminent soil erosion. Soil organic matter is lost very quickly due to erosion, lack of organic manure and poor farming techniques in these areas. Using green hedgerows along contour lines and intercropping with legume species to cover the soil are technological options to control soil erosion and improve soil organic matter content on sloping land. Green hedgerows significantly reduce soil and organic matter loss by 50–70%, compared to sloping land without hedgerows. Intercropping with legume species reduces soil loss by 40–50%, and can provide the soil with 2.5–12 tons of green manure/ha/year. However, more studies are needed to identify the best technologies for managing soil organic matter in upland areas. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of organic matter on the physical and the physicochemical properties of an illitic soil

The main thrust of this study is to investigate the effects of organic matter on the physical and the physicochemical properties of illitic soils. For this purpose, organic matter (peat) was added to inorganic illitic clayey soil at eight levels (0%, 5%, 10%, 12.5%, 15%, 17.5%, 20%, and 30% by weight). The physicochemical properties of the resulting soils were determined using a Grain Size Analyzer (GSA) with specific surface area measurement, Scanning Electron Microscopy (SEM), and Infrared Spectroscopy (IR). The physical properties of the mixtures were determined by conducting a series of laboratory tests including Atterberg limits, compaction, unconfined compressive strength, and swell characteristics tests. The results showed that at low organic contents (in general less than 15%) the soil particles tend to aggregate, whereas at higher organic contents the soil particles tend to disperse. Also, the IR tests showed that direct chemical interactions took place between the organic and the inorganic fractions of the mixtures. The tests on the physical properties showed that at low organic content (up to 10%) the plasticity index slightly increased then after, the plasticity index decreased with increasing organic content. Organic matter has shown to decrease the maximum dry density and increase the optimum water content, nevertheless, although organic matter decreased the soil's compactability, the feasibility of compaction of slightly organic content soils still exists. Moreover, it was shown that organic matter decreased the peak strength values and increased the water contents at these peak strengths. The final free swell for illitic soils increased with increasing levels of added organic matter.     

Structural equation modeling for the estimation of interconnections between the P cycle and soil properties

The aim of this study was used a basic hypothetical structural model with latent variables to analyze the interconnections between the pools of stable P (inorganic P (Pi) and organic P (Po)), labile P (Pi and Po) and available P (Mehlich-1 P) and the pools of organic matter (OM) content and physicochemical properties in tropical soils of differing pedogenesis. We used structural equation modeling for designing models for two groups of soil: (1) mineral soils with low to medium organic matter content and (2) mineral soils with high organic matter content and organic soils. The proposed structural models were consistent with the hypothesis of dependence between the pools of P and organic matter as well as physicochemical properties in tropical soils. In general, stable and labile P pools acted as P sources for the available P pool; furthermore, the strength of these structural relationships was strongly associated with soil organic matter content. Yet the pool of physicochemical properties behaved as a sink of P for the labile P pool, however with a beneficial effect in maintaining the stable P pool. The pools of P and OM are strongly bonded in tropical soils under different pedogenesis. All structural models evidenced that various forms of P in different levels of lability could contribute in keeping the supply of bioavailable P, yet its magnitude would be regulated by P buffer capacity of each soil.     

Development of a fungal pre‐treatment process for reduction of organic matter in contaminated soil

BACKGROUND: Combustion at high temperature is a common treatment method for heavily contaminated soils. The capacity of the combustion process is negatively correlated with organic matter content of the soil. Thus, by reducing the amount of soil organic matter, batch size could be increased and the combustion process improved. In this study, the possibility to pre‐treat soil containing high levels of organic matter with white‐rot and litter‐decomposing fungi was examined and scaled up. RESULTS: Calculations based on the CO₂ production in laboratory experiments indicated that 20% of the soil organic carbon would have been degraded in 6 months when treated with Sphaerobolus stellatus and 10% when treated with Stropharia rugosoannulata. In a pilot‐scale experiment with S. rugosoannulata mass loss due to degradation of soil organic matter accounted for 10% of the total weight of the soil in 6 months. CONCLUSION: A fungal pre‐treatment process for contaminated soils with high organic matter content was developed. Good results were obtained with S. stellatus and S. rugosoannulata and the process was successfully scaled up to 300 kg scale. Copyright © 2009 Society of Chemical Industry     

Plant availability of inorganic and organic selenium fertiliser as influenced by soil organic matter content and pH

The objective of the present study was to investigate the influence of soil organic matter content and pH on plant availability of both inorganic and organic selenium (Se) fertilisers. Further, the risk of Se leaching after application of inorganic Se fertiliser was evaluated. A new interpretation of an older field study at different sites in Southern Norway showed that organic C was correlated with grain Se concentration in wheat, barley and oats, explaining up to 60% of the variation in Se concentration. Pot experiments with a peat soil, a loam soil and a peat/loam soil mixture were conducted for the present study at a range of pH values between pH 5 and 7. Below pH 6, Se uptake from added Se fertiliser was higher in the soil types with high organic matter content than in the loam. The opposite occurred at a soil pH above 6, where Se uptake was higher in the loam than in the peat soil. A simple leaching experiment after one growing season confirmed the findings of the pot experiments that Se availability in the loam soil with a relatively low organic matter content increased with increasing pH, whereas it decreased in the peat soil. Neither Se yeast, nor pure Se methionine, used as organic Se fertiliser, resulted in any significant uptake of Se when added at concentrations similar to the inorganic Se applications.     

Carbon sequestration potential of organic agriculture in northern Europe – a modelling approach

Decline in carbon content in agricultural soils contributes both to climate change and to soil fertility problems. The CENTURY element dynamics simulation model was tested and adapted for Northern European agricultural conditions using long-term datasets from Askov experimental farm in southern Denmark. The part of the model dealing with decomposition was tested in isolation using a bare fallow experiment and it could predict soil organic matter levels with high accuracy. In the cropping experiments predictions were less accurate. The crop production was not accurately predicted. Predictions were more accurate on loamy than on sandy soils. The model was used to predict the effect of conversion to organic agriculture on carbon sequestration as soil organic matter. It predicted an increase in soil organic matter during the first 50 years of about 10–40 g C m^–2 y^–1, and a stable level after about 100 years. The use of grass-clovers in the rotation and as cover crops was particularly important for the increase in organic matter.     

Relationships between soil urease activity and other properties of some tropical wetland rice soils

Ten Philippine wetland rice soils differing widely in pH, texture and organic matter were studied to determine relationships between urease activity and other soil properties. Simple correlation analyses of urease activity with soil properties indicated that urease activity was correlated highly significantly with total N (r = 0.91)^**, and organic C (r = 0.89^**) but was not significantly correlated with CEC, Clay, pH active Fe or active Mn content. From multiple regression analyses it was observed that organic matter content of soils measured by organic C and total N accounted for most of the variation in urease activity.