微纳米增氧水添加对土壤中溶解氧耗散的影响

微纳米增氧灌溉可缓解作物根区氧气限制,促进作物代谢活动和生长发育。为探究微纳米增氧水添加后土壤溶解氧耗散规律及其增氧效果,该研究以初始干旱土壤和初始湿润土壤为研究对象,使用微氧电极技术,监测不同微纳米增氧水平下淹水土壤溶解氧浓度变化规律。结果表明：1)土壤溶解氧浓度随时间呈现快速下降阶段、缓速下降阶段两段式规律,其中快速下降阶段土壤溶解氧耗散以气体扩散为主,耗散曲线符合对数函数规律;缓速下降阶段土壤溶解氧耗散以微生物消耗为主,耗散曲线符合Logistic函数或线性函数规律;2)在初始干旱土壤试验的快速下降阶段,与常规对照处理CK(O₂浓度：8～9 mg/L)相比,O1(O₂浓度：15 mg/L)、O₂(O₂浓度：20 mg/L)处理溶解氧留存时间分别延长了40.11%和189.62%;在初始湿润土壤试验的快速下降阶段,O₁、O₂处理溶解氧耗散时间分别延长了445.16%和2741.94%;3)在微生物活性较低的土壤(初始干旱土壤)中,氧气与底物都是溶解氧消...     

Fe-Co尖晶石型复合氧化物电催化检测牛奶中过氧化氢

为了高效检测牛奶中H₂O₂含量,该研究提出了一种基于ZnFeCoO₄催化还原H₂O₂的非酶电化学传感器。首先,通过溶胶-凝胶燃烧法合成ZnCo₂O₄,再利用Fe部分取代Co合成ZnFeCoO₄。采用透射电子显微镜、X射线衍射及X射线光电子能谱对催化剂的晶体结构和形貌进行表征,并采用循环伏安法对该电极的电化学性能进行研究。结果表明：ZnFeCoO₄具有较好的晶型,基于ZnFeCoO₄的电化学传感器对H₂O₂有良好的电催化性能,检测限为0.5μmol/L;过氧化氢浓度在0.5～2.5mmol/L范围内与还原峰电流呈线性关系,决定系数为0.989。此外,传感器对H₂O₂具有优异重现性和选择性。在实际牛奶样品的加标试验中回收率达到98.60%～101.23%。研究可为液态食品中检测H     

壳聚糖基碳量子点的制备、表征及其对过氧化氢的荧光检测研究

为制备可用于分析过氧化氢(H₂O₂)的荧光传感器,本研究利用壳聚糖与DL-酒石酸为反应前体,水热处理制备了新型氮掺碳量子点(CDs),能够高效、简便地检测食品中的H₂O₂含量;并采用透射电镜(TEM),以及傅里叶变换红外光谱(FTIR)等方法进行分析表征。结果表明,CDs的荧光量子产率约为5.22%,粒径约为20 nm,而且具有石墨烯结构,其表面也含有较丰富的羟基、氨基和羧基等功能性官能团。此外,Fe³⁺可以猝灭CDs溶液的荧光,而Fe²⁺几乎不影响;按照CDs与Fe³⁺混合后荧光几乎消失时的浓度配比,将Fe³⁺替换成同等浓度Fe²⁺再分别加入不同浓度的H₂O₂,快速混均后测量其在320 nm激发光下的荧光发射图谱,绘制标准曲线,H₂O₂浓度在0~60 μmol·L^-1内线性关系良好,相关系数R²约为0.990 0,检测限约为0.65 μmol·L^-1。本研究结果为快速检测食品中的H₂O₂提供了一定的理论依据。     

氮添加对亚高山针叶林土壤结构及水分入渗性能的影响

为探究大气氮沉降增加导致的土壤团聚体结构变化规律及其对土壤水分入渗性能的影响,在贡嘎山针叶成熟林和中龄林内分别设计2种氮肥形态[(NH₄)₂SO₄、KNO₃]和4个浓度水平(0,10,20,40 kg/(hm²·a)N)的添加试验,研究不同形态大气氮沉降对亚高山森林土壤团聚体结构和土壤水分入渗特征的影响。结果表明：(1)随施氮量增加,中龄林土壤大团聚体含量逐渐增加,土壤持水量、孔隙度和水分稳定入渗率逐渐增大;成熟林土壤大团聚体含量、土壤持水量、孔隙度和水分稳定入渗率均表现出先增加后降低的趋势;(2)不同形态氮添加对土壤团聚体结构、孔隙度及水分稳定入渗率的作用无显著差异;(3)土壤持水能力、孔隙度和团聚体结构是土壤入渗性能的主要影响因子,外源氮添加增加中龄林土壤持水量和孔隙度,改善中龄林土壤团聚体结构稳定性和水分入渗性能。     

施磷对镉胁迫下黄瓜苗期光合作用及抗氧化酶系统的影响

  目的  探究石灰性土壤中施磷对镉胁迫下黄瓜苗期光合作用及抗氧化酶系统的影响,为合理施用磷肥、缓解镉毒害提供依据。  方法  采用盆栽完全组合设计方案,研究了不同土壤镉添加水平（0、1、3和5 mg kg?1土）下施加不同浓度磷（0、50、100、150和200 mg P₂O₅ kg?1土）对黄瓜苗期生物量、叶片光合作用及抗氧化酶系统的影响。  结果  随着施Cd量的增加,黄瓜生物量先增后降,黄瓜叶片的净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）显著降低,胞间CO₂浓度（Ci）呈上升趋势。施加适量磷（≤ 150 mg P₂O₅ kg?1）能够显著提高黄瓜生物量、Pn、Gs、Tr、叶绿素总量和类胡萝卜素含量（Car）,降低叶片中Ci。对于抗氧化酶系统来说,随着施Cd量的增加黄瓜叶片中过氧化物酶（POD）、过氧化氢酶（CAT）活性显著降低,丙二醛（MDA）含量明显增加。施磷后,能够明显增强抗氧化酶系统。施Cd量为1 mg kg?1,施磷量为50和100 mg P₂O₅ kg?1时,CAT活性增加了1.9% ~ 9.6%。施Cd量为3和5 mg kg?1时,随着施磷量的增加,POD和CAT活性出现不同程度增加,与不施磷相比,POD活性分别增加了149.1% ~ 197.8%和150.4% ~ 252.0%,CAT活性分别增加了5.8% ~ 16.6%和0.55% ~ 19.4%,其中施磷量为100 mg P₂O₅ kg?1时黄瓜叶片POD和CAT活性达到最大。同时,施P能够降低叶片中MDA含量,且随着施磷量的增加而降低。  结论  在石灰性土壤中,施磷量为100和150 mg P₂O₅ kg?1时,能够明显缓解镉毒害,增强黄瓜叶片的光合作用及抗氧化酶系统,而施磷量达到200 mg P₂O₅ kg?1时则对黄瓜生长产生抑制作用。     

艾叶挥发油对H2O2诱导鲤鱼肝脏氧化损伤的保护作用

为探讨艾叶挥发油对H₂O₂诱导的鲤鱼肝脏氧化损伤的保护作用,本试验以H₂O₂为诱导剂构建鲤鱼肝脏氧化应激损伤模型,分别投喂添加0.1、0.2和0.4 g·kg^-1艾叶挥发油的饵料对其进行保护。试验进行30 d后,采集鲤鱼的血清和肝脏,检测谷丙转氨酶(ALT)、谷草转氨酶(AST)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GPx)活性和总蛋白(TP)、白蛋白(ALB)、丙二醛(MDA) 含量;采用组织学方法对鲤鱼肝组织切片进行显微观察;使用实时荧光定量PCR (qRT-PCR)技术检测Cu/Zn-SOD、Mn-SOD、GPx、CAT和核转录因子(Nrf2) mRNA的相对表达量。结果表明,H₂O₂暴露30 d后,鲤鱼血清中ALT、AST活性升高,TP、ALB含量下降;血清和肝脏中SOD、CAT、GPx活性降低,MDA含量上升,H₂O₂导致肝脏组织病理损伤,抗氧化基因表达受到抑制。而艾叶挥发油能够抑制ALT、AST活性的上升和TP、ALB含量的下降,提高机体的抗氧化能力,缓解肝脏组织的病理损伤,激活Nrf2诱导细胞抗氧化基因的表达。综上所述,艾叶挥发油对H₂O₂诱导的鲤鱼肝脏氧化损伤具有一定的保护作用。本研究可为进一步探究艾叶挥发油作为绿色安全的抗氧化剂提供思路和基础资料。     

黑土区坡耕地侵蚀沟演变对土壤粒径分布及蓄水性的影响

[目的]研究侵蚀作用对黑土区坡耕地侵蚀沟表层土壤的影响,为该区土壤资源合理运用和区域水土流失治理工作提供理论支持。[方法]以黑龙江省哈尔滨市延寿县不同发育程度侵蚀沟为研究对象,对切沟沟头的沟坡和沟底土壤的粒径分布及蓄水性进行定量描述。[结果](1)不同深度处土壤容重、最大吸持贮水量、最大滞留水量、总库容、死库容、最大有效库容差异显著(p<0.05)。随土层加深,土壤容重增大,贮水量、持水性、有效水分下降。各层最大吸持贮水量占饱和贮水量均约90%,有效水分利用率分别为44.79%和41.87%,侵蚀沟发育对土壤有效水分影响明显。(2)入渗特征总体表现为：初始入渗速率>30 min入渗速率>稳定入渗速率,3者在不同编号沟道的A₂—A₄间随土层的加深,入渗性能下降。在20—40 cm层A₁—A₄的入渗特征均表现为：CK(对照)>A₁>A₄>A₂>A₃,呈先下降后上升趋势。随着侵...     

γ-Fe2O3纳米材料与甲基营养型芽孢杆菌对大豆生长及产量的协同促进机制

  【目的】  探究氧化铁纳米材料 (γ-Fe₂O₃ NMs) 与甲基营养型芽孢杆菌叶面配施对大豆生长、产量及籽粒品质的影响及其协同作用机制,为γ-Fe₂O₃ NMs在农业生态系统中的应用提供新思路及理论支持。  【方法】  以大豆为供试作物,纳米材料处理组设置0、1、10、30和50 mg/L 5个浓度,纳米材料与甲基营养型芽孢杆菌复合处理组中包含甲基营养型芽孢杆菌悬液以及对应4个浓度的纳米材料,施用方式为叶面喷施,大豆生长至40天时测定光合作用参数,在成熟期测定植株生物量、植株总糖含量、产量等参数。利用LB平板体外培养实验及分光光度法 (OD₆₀₀)测定γ-Fe₂O₃ NMs对甲基营养型芽孢杆菌生长的影响,利用单颗粒电感耦合等离子质谱仪测定甲基营养型芽孢杆菌对γ-Fe₂O₃ NMs生物可利用性的影响。  【结果】  γ-Fe₂O₃ NMs促进了大豆光合作用,显著提高了大豆生物量,且30、50 mg/L γ-Fe₂O₃ NMs明显提高了大豆产量及籽粒碳水化合物含量。与同浓度纳米处理组 (30、50 mg/L γ-Fe₂O₃ NMs) 相比,甲基营养型芽孢杆菌与γ-Fe₂O₃ NMs共施用的大豆产量分别增加了31.5%及13.4%。甲基营养型芽孢杆菌施用后相较于对照组显著提高了大豆根尖数,γ-Fe₂O₃ NMs单独处理对大豆根尖数没有显著影响,而γ-Fe₂O₃ NMs与甲基营养型芽孢杆菌共施用处理组中大豆的根尖数明显多于甲基营养型芽孢杆菌单独处理。甲基营养型芽孢杆菌发酵液明显降低了γ-Fe₂O₃ NMs的团聚作用。10、30和50 mg/L γ-Fe₂O₃ NMs均能够促进甲基营养型芽孢杆菌的生长,且能够使细菌发酵液中吲哚乙酸含量从3.8 mg/L增加至7.6～8.8 mg/L。γ-Fe₂O₃ NMs与甲基营养型芽孢杆菌配合施用,相较于对照组显著提高了大豆养分吸收及籽粒中营养元素 (Fe、Mn、S、Mg等) 的含量。  【结论】  γ-Fe₂O₃ NMs对光合作用的促进是其促进大豆生长、提高大豆产量的主要机制。γ-Fe₂O₃ NMs与甲基营养型芽孢杆菌配施后,两者对大豆生长、产量及果实品质呈现协同促进作用。其主要机制包括:1) 甲基营养型芽孢杆菌代谢产物能够有效降低γ-Fe₂O₃ NMs的团聚,增加了γ-Fe₂O₃ NMs的生物可利用性;2) γ-Fe₂O₃ NMs显著促进甲基营养型芽孢杆菌生长,提高其代谢产物中吲哚乙酸的含量。     

枯草芽孢杆菌对盐碱土水分运动和水稳性团聚体的影响

为探明微生物在盐碱地改良方面的应用,通过在盐碱土中加入枯草芽孢杆菌,研究不同浓度微咸水(0,1,2,3,4g/L)条件下,盐碱土中的水分运动和土壤水稳性团聚体的变化规律。结果表明:(1)枯草芽孢杆菌可以显著减少土壤的入渗能力,同时可减缓水分的迁移能力,添加枯草芽孢杆菌的土壤与相对应的对照组相比,累积入渗量和湿润锋推进距离均显著减少,其中在微咸水浓度为2g/L时,土壤累积入渗量减少幅度最大,为40.97%,其他处理减少程度依次为3,0,1,4g/L,湿润锋的推进距离也有类似的结果。(2)利用Philip和Kostiakov入渗模型拟合试验数据,发现Philip公式中的吸渗率S均小于相相应对照组,Kostiakov公式中的经验系数K均小于相应对照组,而经验指数β均大于相应对照组。(3)枯草芽孢杆菌可以增加土壤的保水能力,在微咸水浓度为2g/L时,对土壤水吸力的影响较大。与对照组相比,van Genuchten公式中土壤滞留含水率θr、饱和含水率θs及与进气值相关系数α均有所增大,形状系数n逐渐减小。(4)含有枯草芽孢杆菌的土壤,在微咸水入渗后其土壤团粒结构均有较大的改善。     

葛根素对小白菜镉损伤的保护作用研究

为探究葛根素(PUE)对小白菜镉(Cd)损伤的保护效果,采取外源添加不同葛根素处理,将小白菜植株随机分为7组,即对照组(CK)、PUE30组(葛根素30μmol·L^-1)、Cd4组(镉4 mg·L^-1)、Cd与PUE共处理组(4+15、4+30、4+45、4+60)。处理30 d后,观察小白菜植株生长状况、测定Cd富集量及抗胁迫生理活性物质,包括叶绿素、抗氧化酶(SOD、APX、CAT、POD)活性及过氧化氢(H₂O₂)、丙二醛(MDA)Vc、可溶性蛋白含量,并用实时荧光定量PCR(qRT-PCR)技术检测抗氧化酶基因(SOD、POD、APX及CAT)表达量。结果表明,与CK组相比,Cd4组小白菜根中Cd含量、H₂O₂和MDA含量显著升高,而地下部鲜重、地上部鲜重、抗氧化酶(SOD、POD和APX)活性和叶绿素含量整体显著降低(P<0.05)。与Cd4组相比,Cd+PUE共处理组小白菜氧化损伤程度减轻,H₂O₂     

通过土壤泥浆中的过氧化氢处理三氯乙烯污染的土壤

Chlordecone, one of the most persistent organochlorine pesticides, was applied between 1972 and 1993 in banana fields in the French West Indies, which results in long-term pollution of soils and contamination of waters, aquatic biota, and crops. As human exposure to chlordecone is mainly due to food contamination, early research was focused on chlordecone transfer to crops. Field trials were conducted to investigate chlordecone contamination of yam, sweet potato, turnip, and radish grown on a ferralic Nitisol polluted by chlordecone. We also carried out trials on yam, courgette, and tomato under greenhouse conditions with homogenized Andosol and Nitisol, polluted by chlordecone to various extents. Our results indicated that i) all tubers were contaminated in accordance with the chlordecone content of the soils; ii) the contamination capacity of the Nitisol was greater than that of the Andosol; and iii) whatever the soil type, tuber contamination was related to the soil volumetric content of dissolved chlordecone. Nevertheless, no tubers showed sufficient chlordecone uptake for efficient soil decontamination by means of plant extraction. Soil contact accounted for most of the root crop contamination, which was inversely proportional to the tuber size. Internal transfer might also increase root crop contamination when the root central cylinder contained raw sap flow, as in the case of turnip or radish. Courgette fruits showed high contamination without soil contact. Thus, further research is needed to explore the pattern of both below- and aboveground plant chlordecone contamination and assess the hypothesis of its correlation with sap flow. Finally, we used our results to build a decision-making tool for farmers, relating soil pollution with the maximal contamination of the harvested organs to predict crop contamination and thus assisting farmers in making crop choices at planting in order to conform with the European Union’s regulations.     

Oxygen enrichment with magnesium peroxide for minimizing hypoxic stress of flooded corn

Flooding/waterlogging is a major factor responsible for hypoxic stress in agriculture. The aim of this study was to develop an effective oxygen buffer with magnesium peroxide (MgO₂) to generate hydrogen peroxide (H₂O₂) and release bioavailable oxygen. MgO₂ provided a relatively stable level (approx. 300 µM) of bioavailable oxygen. The oxygen‐buffer system is adjustable and controllable by adding Mg²⁺ or EDTA to the aqueous system. Regular H₂O₂ was also able to provide bioavailable oxygen but the system was poorly buffered with respect to oxygen release. The accessibility of plants to bioavailable oxygen was indicated by the activity of alcohol dehydrogenase (ADHase, EC 1.1.1.1), an anaerobically induced enzyme of flooded plants. The application of MgO₂ to flooded soil reduced ADHase activity in corn‐root tips by 91.3%. This application of MgO₂ presents a novel pathway to significantly (P < 5%) minimize adverse impacts of hypoxia on flooded corn seedlings. This finding may have broad implications for addressing hypoxicity problems in crop science and technology.     

The Effect of Treatment with Hydrogen Peroxide and the Mehra–Jackson Reagent on X-ray Diffraction Patterns of Clay Fractions

X-ray diffraction patterns of clay fractions from the AEL and EL horizons of pale-podzolic soil before and after treatment with 10% H₂O₂ and the Mehra–Jackson reagent in different sequences have been examined. The successive treatment with 10% H₂O₂ and then with the Mehra–Jackson reagent causes dissolution of Al-hydroxy-interlayers in pedogenic chlorites and the respective increase in the content of labile minerals because of a dramatic decrease in pH upon the treatment with hydrogen peroxide. The rate of these changes depends on the degree of chloritization of pedogenic chlorites in the initial samples. The result of the reverse sequence of the treatments of clay fractions (initially with the Mehra–Jackson reagent and then with hydrogen peroxide) is opposite: the chloritization of labile minerals becomes more intensive. It is provided by pH values that do not drop below 7.5 at any treatment stage. At particular stages, pH values favors the mobilization of Al compounds and their subsequent polymerization in the interlayer space of labile structures. We suppose that hydroxyl-aluminosilicate layers may be formed in the interlayer space upon this treatment sequence.     

Kinetic and Thermodynamic Studies of Chlorinated Organic Compound Degradation by Siderite-Activated Peroxide and Persulfate

The efficacy of two oxidant systems, iron-activated hydrogen peroxide (H₂O₂) and iron-activated hydrogen peroxide coupled with persulfate (S₂O₈ ^2?), was investigated for treatment of two chlorinated organic compounds, trichloroethene (TCE) and 1,2-dichloroethane (DCA). Batch tests were conducted at multiple temperatures (10–50 °C) to investigate degradation kinetics and reaction thermodynamics. The influence of an inorganic salt, dihydrogen phosphate ion (H₂PO₄ ^?), on oxidative degradation was also examined. The degradation of TCE was promoted in both systems, with greater degradation observed for higher temperatures. The inhibition effect of H₂PO₄ ^? on the degradation of TCE increased with increasing temperature for the iron-activated H₂O₂ system but decreased for the iron-activated hydrogen peroxide-persulfate system. DCA degradation was limited in the iron-activated hydrogen peroxide system. Conversely, significant DCA degradation (87% in 48 h at 20 °C) occurred in the iron-activated hydrogen peroxide-persulfate system, indicating the crucial role of sulfate radical (SO₄ ^??) from persulfate on the oxidative degradation of DCA. The activation energy values varied from 37.7 to 72.9 kJ/mol, depending on the different reactants. Overall, the binary hydrogen peroxide-persulfate oxidant system exhibited better performance than hydrogen peroxide alone for TCE and DCA degradation.     

Oxygen and redox potential gradients in the rhizosphere of alfalfa grown on a loamy soil

Oxygen (O₂) supply and the related redox potential (E_H) are important parameters for interactions between roots and microorganisms in the rhizosphere. Rhizosphere extension in terms of the spatial distribution of O₂ concentration and E_H is poorly documented under aerobic soil conditions. We investigated how far O₂ consumption of roots and microorganisms in the rhizosphere is replenished by O₂ diffusion as a function of water/air‐filled porosity. Oxygen concentration and E_H in the rhizosphere were monitored at a mm‐scale by means of electroreductive Clark‐type sensors and miniaturized E_H electrodes under various matric potential ranges. Respiratory activity of roots and microorganisms was calculated from O₂ profiles and diffusion coefficients. pH profiles were determined in thin soil layers sliced near the root surface. Gradients of O₂ concentration and the extent of anoxic zones depended on the respiratory activity near the root surface. Matric potential, reflecting air‐filled porosity, was found to be the most important factor affecting O₂ transport in the rhizosphere. Under water‐saturated conditions and near field capacity up to –200 hPa, O₂ transport was limited, causing a decline in oxygen partial pressures (pO₂) to values between 0 and 3 kPa at the root surface. Aerobic respiration increased by a factor of 100 when comparing the saturated with the driest status. At an air‐filled porosity of 9% to 12%, diffusion of O₂ increased considerably. This was confirmed by E_H around 300 mV under aerated conditions, while E_H decreased to 100 mV on the root surface under near water‐saturated conditions. Gradients of pO₂ and pH from the root surface indicated an extent of the rhizosphere effect of 10–20 mm. In contrast, E_H gradients were observed from 0 to 2 mm from the root surface. We conclude that the rhizosphere extent differs for various parameters (pH, Eh, pO₂) and is strongly dependent on soil moisture.     

Part 2: A Field Study of Enhanced Remediation of Toluene in the Vadose Zone Using a Nutrient Solution

The objective of this study was to test the effectiveness of a nitrate-rich nutrient solution and hydrogen peroxide (H₂O₂) to enhance in-situ microbial remediation of toluene in the unsaturated zone. Three sand-filled plots were tested in three phases (each phase lasting approximately 2 weeks). During the control phase, toluene was applied uniformly via sprinkler irrigation. Passive remediation was allowed to occur during this phase. A modified Hoagland nutrient solution, concentrated in 150 L of water, was tested during the second phase. The final phase involved addition of 230 moles of H₂O₂ in 150 L of water to increase the available oxygen needed for aerobic biodegradation. During the first phase, measured toluene concentrations in soil gas were reduced from 120 ppm to 25 ppm in 14 days. After the addition of nutrients during the second phase, concentrations were reduced from 90 ppm to about 8 ppm within 14 days, and for the third phase (H₂O₂), toluene concentrations were about 1 ppm after only 5 days. Initial results suggest that this method could be an effective means of remediating a contaminated site, directly after a BTEX spill, without the intrusiveness and high cost of other abatement technologies such as bioventing or soil-vapor extraction. However, further tests need to be completed to determine the effect of each of the BTEX components.     

Physiological and biochemical effects of boron toxicity in mustard during the seedling stage

A study was conducted to determine the physiological and biochemical effects of boron in seedlings of mustard (Brassica juncea L. var Varuna). For this seeds were sown in petridishes with varying concentrations of boron (0, 0.33, 3.3, 33, 330 mM) in seed germinator. Seed germination and vigor index was found to be decreased and percentage phytotoxicity was increased in seeds with increase in the concentration of boron in germinating solution. There was accumulation of sugars and decreased starch concentration in cotyledons and embryonic axes of growing seedling with increasing boron stress. For the estimation of oxidative damage in cotyledons and embryonic axes of mustard seedlings, hydrogen peroxide (H₂O₂), thiobarbituric acid reactive substances (TBARS), phenols and activities of antioxidative enzymes- polyphenoloxydase (PPO), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were determined. Boron toxicity caused accumulation of H₂O₂, TBARS and phenols and affected the antioxidative enzyme activity in growing seedling components.     

Improved methods for selective dissolution of manganese oxides from soils and rocks

Hydroxylamine hydrochloride (NH₂OH‐HCl) and hydrogen peroxide (H₂O₂) have been used in the past for selective dissolution of manganese oxide minerals. The methods reported, however, give poor recoveries. We tried to improve the methods in this respect. By stoichiometry, incomplete dissolution of Mn oxides is due to the lack of NH₂OH‐HCl added or to the lack of acid added in the case of H₂O₂ treatment. By increasing the amount of solution for a given amount of solid in the case of NH₂OH‐HCl and by increasing the acid concentration in the case of H₂O₂ treatment, we obtained rapid and complete dissolution of synthetic Mn oxides. The dissolution of natural samples, however, was slower than that of synthetic ones. Based on the results obtained, the improved methods are: (i) 0.1 m NH₂OH‐HCl, non‐acidified, 2 hours' stirring, and 1 g solid in 2 litres solution; (ii) 30% H₂O₂ in 0.5 m nitric acid, 0.5 hours' stirring, and 1 g solid in 1 litre solution. The improved methods achieved almost complete release of manganese from samples without decreasing the selectivity of dissolution.     

肥液浓度和生物质掺混比例对微润灌溉湿润体内水肥分布的影响

微润灌溉作为一种新型地下连续灌溉节水技术,可为农业水肥一体化提供有效载体。为探明不同生物质掺混比例下竖插式微润灌溉施肥湿润体内水分和养分的分布规律,开展室内入渗试验,设置3个肥液浓度（清水F₀：0 g·L^-1;低浓度F_L：0.2 g·L^-1;高浓度F_H：0.4 g·L^-1）和4个土壤生物质（花生壳粉末）掺混比例（无掺混B₀：0;低掺混B_L：1.5%;中掺混B_M：3.0%;高掺混B_H：4.5%）,研究微润灌溉施肥湿润体内土壤含水率、硝态氮、速效磷和速效钾的分布特性。结果表明：掺混生物质后湿润体内水肥分布范围显著增大,而肥液浓度对水肥分布范围的影响不显著。土壤水肥含量随着与微润管水平距离的增加而逐渐减小,水肥含量最大值出现在微润管周围。在与微润管水平距离为0~10 cm范围内,土壤含水率和硝态氮分布较均匀,速效磷和速效钾则形成累积区。肥液浓度和生物质掺混比例对湿润体内水肥含量均值影响显著。与F₀相比,增加肥液浓度提高土壤含水率和养分（硝态氮、速效磷和速效钾）含量均值3.94%~14.09%和124.92%~458.05%;与B₀相比,增大生物质掺混比例提高土壤含水率和养分含量均值12.89%~33.32%和28.37%~115.44%。微润灌溉施肥湿润体内土壤含水率和硝态氮的分布均匀性较高,而速效磷和速效钾分布均匀性较低。增大肥液浓度和生物质掺混比例可提高湿润体内土壤含水率和硝态氮的分布均匀系数,而降低速效磷和速效钾的分布均匀系数。微润灌溉施肥湿润体内水肥含量均值与至微润管水平距离的关系符合四参数Log-logistic模型。总之,在土壤中掺混生物质有利于微润灌溉施肥下水分和养分的运移,增加肥液浓度和土壤生物质掺混比例可显著提高湿润体内的水肥含量,增大水分和硝态氮的分布均匀性,促使速效磷和速效钾在微润管周围的累积量增多。研究结果可为微润灌溉水肥一体化技术提供理论依据和实践参考。     

Apatite Control of Phosphorus Release to Runoff from Soils of Phosphate Mine Reclamation Areas

This study was initiated to explore the effects of ozone (O₃) exposure on potted wheat roots and soil microbial community function. Three treatments were performed: (1) Air with daily averaged O₃ concentration of 4–10 ppb (control situation, CK), (2) Air plus 8 h averaged O₃ concentration of 76.1 ppb (O₃-1), and (3) Air plus 8 h averaged O₃ concentration of 118.8 ppb (O₃-2). In treatments with elevated O₃ concentration (O₃-1 and O₃-2), the root and shoot biomass were reduced by 25% and 18%, respectively, compared to the control treatment (CK). On the other hand, root activity was significantly reduced by 58% and 90.8% in the O₃-1 and O₃-2 treatments, respectively, compared to CK. The soil microbial biomass was significantly reduced only in the highest O₃ concentration (O₃-2 treatment) in the rhizosphere soil. Soil microbial community composition was assessed under O₃ stress based on the changes in the sole carbon source utilization profiles of soil microbial communities using the Biolog? system. Principal component analysis showed that there was significant discrimination in the sole-carbon source utilization pattern of soil microbial communities among the O₃ treatments in rhizosphere soil; however, there was none in the bulk soil. In rhizosphere soil, the functional richness of the soil microbial community was reduced by 27% and 38% in O₃-1 and O₃-2 treatments, respectively, compared to CK. O₃-2 treatment remarkably decreased the Shannon diversity index of soil microbial community function in rhizosphere soil, but the O₃-1 treatment did not. In the dominant microorganisms using carbon sources of carbohydrates and amino acids groups were significantly reduced by an elevated O₃ concentration in the rhizosphere soil. Our study shows that the elevated ozone levels may alter microbial community function in rhizosphere soil but not in the bulk soil. Hence, this suggests that O₃ effects on soil microbes are caused by O₃ detriments on the plant, but not by the O₃ direct effects on the soil microbes.