土壤中胡敏酸的光化学降解及其对苯并[α]芘结合性质的影响

在不同光照时间、pH和溶解氧浓度下,研究了土壤中胡敏酸经模拟太阳光照射后对苯并[α]芘结合性质的影响.结果表明胡敏酸经模拟太阳光照射后,其与苯并[α]芘的结合系数Koc下降.光化过程中胡敏酸的分子量或SUVA270 与Koc之间有较好的指数回归关系.在pH 4.1～8.0 范围内,在光照后pH条件下测定经光照处理样品的Koc值平均下降34.3% ± 4.1%,在光照前pH条件下测定经光照处理样品的Koc值平均下降33.8% ± 8.3%.溶解氧浓度的升高能加速胡敏酸的光氧化降解过程,与相应的未经光照处理样品相比,在空气饱和与氧气饱和条件下光照后的Koc分别下降37.2% 和47.1%.     

蒙脱石对不同施肥处理土壤胡敏酸及其级分的吸附特征Ⅰ.蒙脱石对胡敏酸的吸附特征

以17年不同施肥处理土壤胡敏酸为材料,研究了不同性质胡敏酸与钙饱和蒙脱石的 吸附特征。结果表明,钙饱和蒙脱石对土不同施肥处理胡敏酸的吸附曲线可用单表面Langmuir方程、双表面Langmuir方程以及Freundlich方程来描述。由单表面Langmuir方程计算的有机肥处理（厩肥、秸秆）胡敏酸的吸附量和吸附强度大于无肥、化肥处理。温度升高各处理胡敏酸吸附量增加,但吸附强度下降。双表面Langmuir揭示,蒙脱石对胡敏酸的吸附呈现高低两种能位的吸附。高能点位的吸附以化学吸附为主,是吸热反应,低能点位的吸附以物理吸附为主,是放热反应。有机肥处理和无肥、化肥处理相比,高能点位吸附相对减弱,低能点位吸附相对增强。     

水田土壤富里酸组分的结构表征及对多环芳烃芘的吸附特征

本文依次用pH4．8、pH7．0及pH11．0的通用缓冲液、水和乙醇,梯度淋洗吸附富里酸的XAD-8树脂,根据其不同解离程度及亲水性质将富里酸细分为5个组分（包括3个亲水性组分和2个疏水性组分）;利用元素分析、红外光谱和核磁共振等分析方法确定各组分的理化特征,并研究各组分对特定多环芳烃（芘）的吸附特性。结果表明,按照淋洗次序,后分离的组分其羧基碳含量低于先分离的组分,烷基碳含量则高于后者;芘在被水和乙醇淋洗出的两种组分上的吸附等温线体现出良好的线性;组分中的烷基组分对吸附有促进作用,相反,羧基和羰基不利于芘的吸附,表明梯度淋洗分组方法对研究芘与富里酸的作用机理是十分有效的。     

铁氧化物-胡敏酸复合物对磷的吸附吸附

本试验通过设置不同磷酸根浓度、 pH和不同电解质及电解质强度梯度,研究磷酸根在针铁矿-胡敏酸（HA）复合物和赤铁矿-胡敏酸（HA）复合物表面的吸附特性。X射线衍射（XRD）、 扫描电镜（SEM）和红外光谱（FTIR）图谱显示: 铁氧化物包覆胡敏酸后其内部结构特性保持不变; 氧化铁与胡敏酸通过氢键形成粒径大、 表面光滑的铁氧化物-HA复合微粒,且复合物比表面减小; 形成的氧化铁-胡敏酸复合物对磷的吸附能力增强,且针铁矿复合物的吸附能力大于赤铁矿复合物,均为多层吸附过程; pH增高抑制铁氧化物复合物对磷的吸附,同时电解质浓度增加促进复合体对磷的吸附,且反应后体系pH随之降低。     

不同施肥处理土壤胡敏酸及其级分与蒙脱石的吸附特征 Ⅱ. 蒙脱石对胡敏酸不同级分的吸附

采用酒精沉淀法，反不同施肥处理土壤胡敏酸分7个级分，研究了胡敏酸不同级分与钙饱和蒙脱石的吸附特征。结果表明，蒙脱石对胡敏酸各级分的吸附可用单表面Langmuir、双表面Langmuir和Freundlich方程来描述。各级分的吸附量和吸附强度不是随级分数变化单一递增或递减，在7个级分中，级分4、3的吸附量和吸附强度较大，是吸附最佳级分。说明级分4、3具有与蒙脱石胶体最佳的成键吸附状态，是吸附最佳分子状态，有机肥处理，吸附最佳级分的吸附性状（吸附量和吸附强度）优于化肥、无肥处理。     

不同施肥处理土壤胡敏酸及其级分与蒙脱石的吸附特征 Ⅱ. 蒙脱石对胡敏酸不同级分的吸附

采用酒精沉淀法，把不同施肥处理土壤胡敏酸分为7个级分，研究了胡敏酸不同级分与钙饱和蒙脱石的吸附特征。结果表明，蒙脱石对胡敏酸各级分的吸附可用单表面Langmuir、双表面Langmuir和Freundlich方程来描述。各级分的吸附量和吸附强度不是随级分数变化单一递增或递减，在7个级分中，级分4、3的吸附量和吸附强度较大，是吸附最佳级分。说明级分4、3具有与蒙脱石胶体最佳的成键吸附状态，是吸附最佳分子状态。有机肥处理，吸附最佳级分的吸附性状（吸附量和吸附强度）优于化肥、无肥处理。     

诺氟沙星在胡敏酸上的吸附热力学与动力学特征研究

根据OECD Guideline106批平衡实验,研究了诺氟沙星在胡敏酸上的吸附热力学和动力学,并探讨了其可能吸附机理。结果表明,诺氟沙星在经过约12h的快速吸附阶段后,进入缓慢吸附阶段,其吸附平衡时间为48h。伪二级动力学方程能够较好地描述不同pH条件下诺氟沙星在胡敏酸上的吸附动力学特性。诺氟沙星在胡敏酸上的吸附等温线符合Freundlich方程,该方程的拟合系数1/n〈0.5,表明诺氟沙星在胡敏酸上为非线性吸附。ΔH0=-48.85kJ·mol-1和ΔG0〈0,表明诺氟沙星在胡敏酸上的吸附是自发进行的放热过程,且离子交换是其主要吸附机理,同时也可能存在着偶极间作用力、氢键力和电荷转移等吸附机理;ΔS0〈0表明吸附过程中熵在减小。吸附位点的能量随着吸附量的增大而降低,也表明胡敏酸的异质性和吸附的非线性。     

蒙脱石对不同施肥处理土壤胡敏酸及其级分的吸附特征Ⅰ.蒙脱石对胡敏酸的

以１７年不同施肥处理土壤胡敏酸为材料,研究不同性质胡敏酸与钙饱和蒙脱石的吸附特征。结果表明,钙饱和蒙脱石对娄土不同施肥处理胡敏酸的吸附曲线可用单表面Ｌａｎｇｍｕｉｒ方程、双表面Ｌａｎｇｍｕｉｒ方程以及Ｆｒｅｕｎｄｉｃｈ方程来描述。由单表面Ｌａｎｇｍｕｉｒ方程计算的有机肥处理（厩肥、秸秆）胡敏酸的吸附量和吸附强度大于无肥、化肥处理。温度升高各处理胡敏酸吸附量增加,但吸附强度下降。双表面Ｌａｎｇｍｕｉｒ揭示,蒙脱石对胡敏酸的吸附呈现高低两种能位的吸附。高能点位的吸附以化学吸附为主,是吸热反应,低能点位的吸附以物理吸附为主,是放热反应。有机肥处理和无肥、化肥处理相比,高能点位吸附相对减弱,低能点位吸附相对增强。     

秸秆深还对土壤团聚体中胡敏酸结构特征的影响

秸秆深还(Deep application of straw,DAS)是指将玉米秸秆施入土壤亚表层(20~40cm),可以解决秸秆焚烧的问题,同时提高土壤肥力、蓄水能力和作物产量。本文采集了吉林农业大学试验站玉米连作耕地试验田中的秸秆深还土壤和未秸秆深还土壤,采用湿筛法将其分为2 mm、2~0.25 mm、0.25~0.053 mm和0.053 mm 4个粒级,定性分析提取胡敏酸(HA),通过元素组成、红外光谱和差热分析研究了秸秆深还对黑土各粒级团聚体中HA结构特征的影响。结果表明:黑土团聚体中的优势粒级为2~0.25 mm粒级,优势粒级的团聚体含量和有机碳含量均是表层较亚表层低,DAS有利于优势粒级团聚体的形成,促使优势粒级团聚体中有机碳增多;与亚表层相比,表层各粒级团聚体HA的缩合度、氧化度和热稳定性普遍较低,脂族碳/羧基碳和脂族碳/芳香碳较高;DAS促使土壤表层和亚表层各粒级团聚体中HA的缩合度、氧化度和热稳定性下降,其中表层HA的缩合度降低更明显;而亚表层氧化度和热稳定性的降低幅度较大。表层中HA的分子结构较亚表层的简单、年轻,秸秆深还促使土壤中有机碳含量增加,HA的结构简单化、年轻化。     

雪被斑块对高山森林凋落叶腐殖化过程中胡敏酸和富里酸累积的影响

高山森林凋落叶腐殖化过程中胡敏酸(Humic acid,HA)、富里酸(Fulvic acid,FA)等腐殖物质的累积是土壤形成和碳吸存的重要途径,并可能受到冬季不同厚度雪被斑块的影响,但一直缺乏必要关注。本文采用凋落物网袋法,于2012/2013年冬季研究了川西高山森林天然形成的不同厚度雪被斑块(厚雪被、中雪被、薄雪被和无雪被)下优势树种岷江冷杉(Abies faxoniana)、方枝柏(Sabina saltuaria)、四川红杉(Larix mastersiana)、红桦(Betula albo-sinensis)、康定柳(Salix paraplesia)和高山杜鹃(Rhododendron lapponicum)凋落叶在不同雪被关键期(雪被形成期、雪被覆盖期和雪被融化期)腐殖化过程中胡敏酸和富里酸累积特征。结果表明:经过一个冬季,6种凋落叶胡敏酸碳和富里酸碳含量在各雪被关键期均表现出随雪被厚度减少而增加的趋势,而净累积量表现出在雪被形成期和融化期随雪被厚度减少而增加、在雪被覆盖期随雪被厚度减少而减少的趋势,且均受到凋落叶初始酸不溶性组分含量的影响。同时,不同雪被斑块下6种凋落叶胡敏酸碳均累积且净累积量为四川红杉康定柳岷江冷杉高山杜鹃红桦方枝柏,而除红桦外的其他5种凋落叶富里酸碳均出现不同程度的降解且降解量为四川红杉高山杜鹃康定柳方枝柏岷江冷杉红桦。这些结果清晰地表明,未来气候变暖情景下冬季雪被的减少可能促进高山森林凋落叶腐殖质累积,但在雪被覆盖不同时期受到雪被斑块特征和凋落叶基质质量的调控。     

Sorption of phosphorus by some surface soils from Quebec in relation to their properties

Abstract

Surface horizons from Podzolic and Gleysolic soils were collected in various parts of the province of Quebec, Canada, and equilibrated with various amounts of KH₂PO₄ in 0.01 M CaCl₂ for 48 hours. P sorption data conformed to the linear form of the Langmuir and Freundlich equations. P solubility isotherms showed evidence of hydroxyapatite formation in most samples studied, whereas equilibration solutions of only few samples were saturated with respect to either dicalcium phoshate dihydrate or octocalcium phosphate. These reaction products were associated to soil pH and levels of added phosphate. The average values of the Langmuir sorption maximum for these studied Gleysolic and Podzolic samples were 763 and 1096 μg/g respectively. These values were higher than those obtained by the segmented and modified Freundlich models.

Relationships between the soil characteristics and P sorption parameters were evaluated by regression analysis. Among all variables, oxalate‐extractable Fe plus Al content of the Podzolic samples and the ratio of oxalate—extractable Al to clay of the Gleysolic samples gave the best significant correlation coefficients. Furthermore, soil pH and various ratios such as pyrophosphate‐extractable Fe and Al, oxalate‐extractable Fe and organic matter to clay were found to be significantly correlated only with the P sorption parameters of the Gleysolic samples.     

Release and Sorption Pattern of Monosilicic Acid from Silicon Fertilizers in Different Soils of Louisiana: A Laboratory Incubation Study

The amount of monosilicic acid (H₄SiO₄), which is the plant-available form of silicon (Si), released from fertilizers can be influenced by Si source and soil properties. A series of laboratory experiments were conducted using six soil series from Louisiana to document the differences in the release characteristics of H₄SiO₄ from wollastonite and slag. Monosilicic acid in solution released from slag declined with time while wollastonite consistently increased its concentration across all soil suspensions well above 40 µg mL^?1. Among these soil series, soils high in organic matter and clay were seen to have maximum percent sorption (up to 79%) with minimum polymerization of H₄SiO₄. The presence of ions like aluminum (Al) and magnesium (Mg) enhanced the process of H₄SiO₄ polymerization, which led to a decrease in H₄SiO₄ concentration in solution. Evident relationships were observed between H₄SiO₄ concentration in solution with added Si sources and sorbed quantity from soil solutions.     

Effects of Goat Manure and Lime Addition on Phosphate Sorption by Two Soils from the Transkei Region,South Africa

More than 40% of soils in the Transkei region, South Africa, have high phosphorous (P) fixation capacities that necessitate application of high P fertilizer rates. This incubation study compared the effectiveness of goat manure (GM) and lime to minimize P sorption in two such soils. Manure application reduced P sorption in both soils, which was partly attributed to the liming effect of GM that resulted in marked reductions of exchangeable aluminum (Al). The liming effect of GM rates followed the order 20 t GM ha^?1 > 10 t GM ha^?1 > 5 t GM ha^?1. Therefore, GM can be cost‐effectively used to lime acid soils in the region and reduce their Al toxicity potential and P fertilizer requirements. Liming reduced P sorption on the Chevy Chase soil soon after application, but P sorption was reduced after 2 months on the Flagstaff soil, suggesting that the timing of liming for improved P availability could be critical for some soils.     

The Use of Goats Grazing to Restore Pastures Invaded by Shrubs and Avoid Desertification: A Preliminary Case Study in the Spanish Cantabrian Mountains

Spanish mountains have been affected by the expansion of shrubs and forests since the mid‐20th century. This secondary succession in vegetation has some positive effects, but also drawbacks, such as an increase in fire risk, loss of diversity in land use, a reduction in landscape and cultural value, less water available in river channels and reservoirs, constraints on livestock farming, a reduced number of local species and loss of biodiversity. This paper analyses the potential for grazing domestic goats to help control the spread of several species of shrubs such as the common broom (Cytisus scoparius), red raspberry (Rubus idaeus) and roses (Rosa sp.) that are commonly found in degraded pastures in the Cantabrian Mountains of northern Spain. Using experimental plots, the effects of two levels of stocking density (4·5 and 9 goats ha⁻¹ y⁻¹) are compared with other land management systems used in the region: burning, mechanical clearing and trimming. The combined use of goats with support from burning, clearing and trimming controls the spread of shrubs. The most efficient treatment was found with nine goats ha⁻¹ y⁻¹. Goat grazing also changes the distribution of shrubs, transforming a dense and continuous coverage into separate clumps and thereby enabling livestock to graze more easily. Maintaining a mixed structure of shrubs and pastures is the best treatment due to the low population density of the Cantabrian Mountains, as this enhances the biodiversity, controls fire risk and enriches the landscape; it also allows extensive livestock grazing as a main economic resource. Copyright © 2013 John Wiley & Sons, Ltd.