冻融作用对土壤胶体及胶体结合态铅迁移的影响

以东北地区棕壤为研究对象,通过人工控温和土柱淋洗试验,研究了不同冻融处理下铅污染土柱中土壤胶体和胶体结合态铅的迁移特征。结果表明:土壤高含水量(田间持水量100%)条件下冻融作用促进土壤胶体的迁移;土壤低含水量(田间持水量10%)条件下冻融作用对土壤胶体的影响减弱。淋洗试验中,土壤胶体在前20 min内大量淋失出土体,随后淋失量急剧减少;且前20 min内的土壤胶体淋失量随着冻融次数的增加先增加后减少。污染土柱中铅主要以胶体结合态的形式迁移,其迁移特征和受冻融作用影响的趋势与土壤胶体类似。冻融处理后滞留在土柱深层的铅含量较高,表明冻融作用能够促进铅向深层土壤迁移。     

钼提高植物抗逆性研究进展

钼（Mo）作为植物必需的微量元素,在促进植物生长发育和增强植物抗逆性方面发挥着关键作用。植物对钼的吸收转运主要受到钼酸盐转运蛋白基因MOT1和MOT2调控,钼进入植物体内以含钼酶形式参与植物生长代谢,其中对植物抗逆性方面的调控主要表现为：钼通过含钼酶硝酸还原酶、醛氧化酶、黄嘌呤脱氢酶影响植物体内的光合碳氮代谢、激素合成和活性氧代谢进而调控植物抗寒性;钼通过硝酸还原酶和醛氧化酶介导的信号转导过程调控根系发育、养分水分利用及抗旱基因表达,进一步影响脂质合成与代谢调控植物抗旱性;最新研究还发现钼在植物适应盐胁迫、缓解重金属胁迫方面也具有重要作用。这些研究结果为通过钼营养调控提升植物的抗逆性提供了新思路。     

Impacts of Municipal Wastewater on The Transport Characteristics of Reactive Solutes Through Agricultural Soils

Reliable transport parameters of agrochemicals and soluble pollutants are crucial for modeling and management of soil and groundwater quality. This study investigated impacts of municipal wastewater on the transport parameters of five heavy metal/metalloid compounds (NaAsO₂, Cd(NO₃)₂, Pb(NO₃)₂, Ni(NO₃)₂ & ZnCl₂), two pesticides (cartap & carbendazim) and an inert salt (CaCl₂) in four agricultural soils of Bangladesh. Solute-breakthrough concentrations were measured in repacked soil columns with time-domain reflectometry (TDR) both before and after wastewater treatment. Transport velocity (V), dispersion coefficient (D), dispersivity (λ) and retardation factor (R) of the solutes, and pertinent soil properties were determined. Wastewater reduced bulk density (γ) of the soils (from 1.32–1.37 g/cm³ to 1.26–1.35 g/cm³) by increasing organic carbon (OC) (from 0.37%–0.84% to 0.40–0.93%), increased pore-size distribution index (n) (by 0.02 unit) and reduced soil pH (from 6.32–7.45 to 5.92–6.46). D and λ decreased while V and R increased after wastewater treatment; D decreased and R increased linearly with decreasing bulk density. The correlations of V, D, and R with n improved significantly (p < 0.05) after wastewater treatment. The correlation between λ and OC improved markedly for Ca, Pb, Ni, and cartap. The observed indicative results have practical implications in developing pedo-transfer functions for solute-transport parameters using basic soil properties, which are subject to progressive modification due to agrochemicals application and wastewater irrigation.     

涌泉根灌湿润体水氮运移特性试验研究

在陕北米脂山地微灌枣树示范基地原状土上进行了涌泉根灌肥液入渗试验,研究了湿润体特征值的变化规律及水氮运移特性.〖JP+1〗结果表明：涌泉根灌入渗能力随肥液质量浓度增大而增大,累积入渗量与入渗时间的关系符合Kostiakov模型;竖直剖面的水平和垂直方向上的湿润锋运移速度均随肥液质量浓度增大而增大,并与时间均呈良好的幂函数关系.肥液质量浓度越大,涌泉根灌相同时间内湿润体的湿润深度越深,相同位置处的土壤质量含水率越大.清水与不同肥液质量浓度的涌泉根灌土壤平均质量含水率分布规律类似,肥液质量浓度越大,相同土层深度的质量含水率越大.在一定施肥条件下,涌泉根灌肥液入渗相同深度处NO-3-N与NH+4-N质量比均随肥液质量浓度增大而增大,经过水分再分布,均于土层深度70 cm处接近本底值.     

蚯蚓粪对土壤团聚体组成和入渗过程水分运移的影响

通过室内土壤团聚体组成分析试验和土柱一维垂直入渗试验,探究蚯蚓粪对土壤团聚体组成、抗水蚀稳定性以及入渗过程中水分运移特性的影响。结果表明:(1)蚯蚓粪可以有效降低土壤容重,增加0.25~2 mm粒级大团聚体的数量,分形维数D从2.84减小至2.65,减小了6.69%,显著提高了土壤团聚体抗水蚀稳定性;(2)施加比例为1/20时,可以显著增加湿润锋的运移距离,而后随着施加比例的增大,湿润锋距离有不同程度的减小,但均大于未施加蚯蚓粪的处理,且各处理下的湿润锋运移距离与入渗时间的关系均可用幂函数描述;(3)蚯蚓粪比例的增大可以显著提高累积入渗量和稳定阶段的入渗速率,当施加比例为1/3时,累积入渗量较对照组增大48.74%;其中Kostiakov-Lewis模型对入渗过程的模拟准确度最高,也更接近实测值。     

马尾松幼苗光合产物的运输与分配特征

【目的】解析光合产物在马尾松幼苗植株中的运输和分配规律,揭示马尾松生产力形成过程,为探讨不同环境干扰下马尾松光合产物分配过程的变化提供参考依据。【方法】采用 13 C同位素脉冲标记法,对1.5年生马尾松幼苗进行标记,标记结束后第0、2、5、17、24、72、120、168、216和 360 h ,按不同部位对马尾松幼苗进行全收获取样,测定 13 C含量,以监测近期合成的光合产物在马尾松幼苗中的运输和分配规律,同时测定光合产物全碳、非结构性碳水化合物(NSC)在各个器官的积累量。【结果】1)标记的光合产物在针叶中合成后,向各库器官的运输量随着时间延长由多逐渐减少,具体表现为标记结束后0~24 h内最多,24~216 h逐渐减少,216 h之后运输完成,且59%以上标记的光合产物在0~24 h内运输到各库器官。2)光合产物运输趋于稳定后,在各器官的分配大小依次为1年生叶>当年生叶>根>茎干>1年生枝>当年生枝,与生物量的分配大小一致,但与库活力大小不同,其库活力依次为当年生叶>当年生枝>1年生叶>根>1年生枝>茎干。3)各器官全碳和NSC积累量的分配与近期合成光合产物的分配大小一致,依次为1年生叶>当年生叶>根>茎干>1年生枝>当年生枝。【结论】马尾松幼苗光合产物运输速率大于0.1 m ·h -1 ,59%以上标记的光合产物在合成后的0~ 24 h 内完成向各个库器官输出。新合成的光合产物在各器官中的积累量表现为功能器官(叶和根)居多,这一分配规律有利于马尾松幼苗阶段的生长。     

Relationship between greenhouse gas emissions and changes in soil gas diffusivity in a field experiment with biochar and lime

Reducing greenhouse gas emissions from arable soil while maintaining productivity is a major challenge for agriculture. Biochar is known to reduce N₂O emissions from soil, but the underlying mechanisms are unclear. This study examined the impact of green waste biochar (20 Mg ha^?1) and lime (CaCO₃; 2 Mg ha^?1) application on soil gas transport properties and related changes in these to soil N₂O and CO₂ emissions measured using automated chambers in a field experiment cropped with maize. In situ soil water content monitoring was combined with laboratory measurements of relative soil gas diffusion coefficient (D_p/D₀) at different matric potentials, to determine changes in D_p/D₀ over time. Cumulative N₂O emissions were similar in the control and lime treatment, but much lower in the biochar treatment. Cumulative CO₂ emissions decreased in the order: lime treatment > biochar treatment > control soil. When N₂O emissions were not driven by excess N supply shortly after fertilisation, they were associated with D_p/D₀ changes, whereby decreases in D_p/D₀ corresponded to N₂O emissions peaks. No distinct pattern was observed between CO₂ emissions and D_p/D₀. Cumulative N₂O emissions were positively related to number of days with D_p/D₀ < 0.02, a critical limit for soil aeration. These results indicate that improved soil gas diffusivity, and hence improved soil aeration, may explain the effect of biochar in reducing N₂O emissions. They also suggest that knowledge of D_p/D₀ changes may be key to explaining N₂O emissions.     

Periglacial transport distance of Pb derived from small-scale ore veins in the Rhenish Slate Mountains

The spatial extent of metal contamination caused by small-scale ore veins is increased by periglacial solifluction. Our objectives were (1) to examine the spatial distribution of Pb in cover beds that migrated over Pb ore veins, (2) to calculate the transport distance of ore-derived Pb, and (3) to determine controls on the transport distance.We examined six transects (320-775 m long) in the Rhenish Slate Mountains in West Germany. The transects included four west-exposed and two east-exposed slopes with inclinations between 2-20°. All transects were forest-covered and located at 280-450 m above sea level. Soils were Dystric Cambisols and Stagnic Luvisols. Samples of 120 B horizons developed in the sediments of the last ice age (Wuerm) were analyzed for total Pb concentrations and partly also ²⁰⁶Pb/²⁰⁷Pb ratios. The Pb concentrations ranged from 20 to 135 mg kg^− 1. The spatial Pb distribution suggested that 14 (out of 18) sampling points showing local Pb concentration maxima contained Pb from ore veins upslope. With a two-end-member-mixing model using ²⁰⁶Pb/²⁰⁷Pb isotope ratios of the ore (²⁰⁶Pb/²⁰⁷Pb ratio: 1.1828) as one end member and of the native substrate (a mixture of slate and loess; ²⁰⁶Pb/²⁰⁷Pb ratio: 1.2254 ± 0.0072) as the other we confirmed that the 14 Pb peaks originated from the ore, because they contained 76-100% of ore-derived Pb. By the use of a geographic information system, the transport distance of this Pb was determined to range between 30 and 110 m. Silt concentrations (Pearson r = − 0.69) and the relief curvature (Cramér's V = 0.60) were major controls on the transport distance. Our study demonstrates that Pb ore veins can increase native soil Pb concentrations in soil derived from the periglacial drift of the last ice age (Wuerm) up to a distance of more than 100 m.     

固体脂质纳米增强抗菌药物对胞内金黄色葡萄球菌活性的研究进展

金黄色葡萄球菌导致的乳房炎是危害奶牛养殖业最严重的疾病之一。抗菌药在胞内极易排出或失活,导致奶牛金黄色葡萄球菌乳房炎治疗效果差且容易复发。纳米粒子具有在巨噬细胞和上皮细胞等多种细胞中积累的能力,可提高药物在胞内的浓度和胞内停留时间,这使得它们可用于治疗细胞内感染。本文对固体脂质纳米抗金黄色葡萄球菌感染的研究进展进行综述,以指导和推动固体脂质纳米在治疗金黄色葡萄球菌乳腺炎方面的应用。