Detection of non‐equilibrium contaminant release in soil columns: Delineation of experimental conditions by numerical simulations

Robust and reliable laboratory methods are required to assess the rate of release of pollutants from contaminated materials. A widely used approach to determine release parameters are soil column experiments. Release rates are thereby obtained by the analysis of the concentration time profile measured at the column outlet, the so called breakthrough curve. Insufficient experimental information as a consequence of simple experimental designs, however, results in the non‐unique identification of the release processes. This is due to the equifinality, i.e., different processes result in the same breakthrough behavior. We analyzed column outflow experiments for their suitability for the identification of non‐equilibrium conditions by means of numerical simulations. Results show that non‐equilibrium conditions can be detected only in a small range of release time scale to transport time scale. Most frequently, non‐equilibrium remains undetected due to unmatched experimental conditions. Flow interruptions and modulation of the flow velocity are an important means to allow for better detection of possible non‐equilibrium release processes. The efficiency of flow interruptions sensitively depends on the experimental conditions, such as point of time and duration of the interruption and the imposed flow velocity. Column experiments are a suitable experimental tool to investigate non‐equilibrium. However, the course of the experiment has to be designed very carefully.     

利用低场核磁共振及其成像技术分析水稻浸种过程水分传递

为研究水稻种子浸种过程中内部水分流动情况,可视化内部水分传递过程,利用低场核磁共振及其成像技术,监测沈农9816号、七山占及秀子糯3个品种水稻种子48 h浸种过程。每6 h时间间隔利用自旋回波（spin echo,SE）脉冲序列获取样品的质子密度加权像,利用硬脉冲自旋回波（carr-purcell-meiboomgill sequence,CPMG）序列获取样品的横向弛豫时间T2反演谱,从而分析浸种过程对水稻种子内部水分分布的影响。试验结果表明：核磁共振是一种有效的水分检测技术,可以实现浸种过程中种子内部水分的快速、准确、无损的检测。利用水稻种子的质子密度加权像,能够直观检测到种子内部水分分布情况,动态的监测到种子内部水分流动过程,分析发现水分最初是从胚进入种子内部,继而通过种皮的渗透,最后到达胚乳部分。根据T2反演谱信号幅值计算得到的水稻种子吸水率,发现3个品种在相同浸种时间的各个监测点均反映出秀子糯吸水率最高,沈农9816号吸水率最低,试验结果验证了支链淀粉的吸水性优于直链淀粉。研究结果可以为水稻种子浸种过程中水分传递的理论模型构建提供数据支持。     

Surface distribution of pyrethroids following topical application to veterinary species: Implications for lateral transport

Pyrethroids like permethrin have been used as topical formulations for their ectoparasiticidal effects since the 1970s. There are numerous efficacy studies in dogs and livestock animals that indicate a fast spread of pyrethroids after topical administration onto rather confined areas of the skin. Some studies correlate the efficacy against ticks, fleas or lice with concentrations of pyrethroids in hair and, less frequently, stratum corneum samples. It is often stated that lateral transport is responsible for the distribution of the pyrethroids over the body surface. With this review, we attempt to demonstrate evidence for lateral transport of pyrethroids after topical administration in dogs, cattle and sheep and to present data gaps that should be addressed in follow‐up studies.     

冶河灌区农田土壤水分与硝态氮分布规律研究

为分析农业生产对农业生态系统和地下水环境的影响,2012-2013年在冶河灌区开展小麦、玉米轮作区农田土壤含水率和硝态氮田间试验,同时对地下水位和水质进行了监测。通过分析试验数据,结果表明:小麦、玉米轮作周期0~300cm土层范围内,土壤含水率变化呈X型。计划灌水定额相同,不同地块灌溉引起土壤含水率明显变化的土层深度不同,其原因是主要受土壤初始含水率和土壤空间异质性的影响;小麦、玉米轮作周期0~300cm土层范围内,土壤剖面硝态氮含量变化呈单调递减曲线。2013年3月土壤硝态氮累积量最高,2013年5月硝态氮的淋洗量最大。在地下水位埋深8~9m,灌水量为900~1 200m3/hm2时,硝态氮运移主要发生在耕层土壤,施肥和降水是土壤硝态氮向深层土壤淋洗、地下水质变化的主要影响因素。     

农用运输车后桥壳体的结构强度分析

运用有限元分析和应力电测技术对某农用运输车驱动后桥壳体的结构强度和刚度进行了研究，分析了农用运输车在直线行驶、倒车制动以及转向时后桥壳体在相应载荷作用下的变形和压力分布状况，并分析了后桥壳体上牙包和半轴套管过渡处的圆弧半径对该区域应力的影响及夹持钢板弹簧的U螺栓的预紧力对桥壳局部结构强度的影响。结果表明：在倒车制动时，后桥壳体上的应力数量最大；3种工况下桥壳上的高压力区均出现在过渡区域；加大过渡圆弧半径并不能普遍减小桥壳的应力，某些局部区域的应力还会有所增加。研究结果为桥壳结构设计提供了一定依据。     

宁夏银北干旱半干旱地区水盐动态和调控措施

通过对宁夏惠农县东永固试验区地下水盐动态和土壤水盐剖面分布变化的实际观测 ,分析得出以蒸发积盐为主要影响因素的宁夏银北干旱半干旱地区年内地下水和土壤水盐运动变化特征 ,并且就其对春小麦产量的影响和适宜本地区特点的水盐调控措施进行了初步探讨     

Sensitivity analysis and field testing of the RISK-N model in the Central Valley of Chile

We present the results from a sensitivity analysis and a preliminary short-term, site-scale performance assessment of the analytical soil and groundwater nitrate transport RISK-N. The study was carried out in the Central Valley of Chile, on a 2.6 ha corn (Zea mays L.) field underlain by a shallow unconfined aquifer during the cropping season 2000–2001. Nitrogen levels in soils as well as NO₃⁻–N irrigation water and groundwater concentrations were monitored through the crop-growing period, the latter by a network of 16 monitoring wells. A sensitivity analysis shows that both the nitrate flux from the vadose zone and NO₃⁻–N groundwater concentration are mainly influenced by the initial soil nitrogen levels, water input, and soil porosity. Also, simulated groundwater NO₃⁻–N levels are sensitive to changes on the saturated zone denitrification constant. An additional analysis further reveals the significance of the latter parameter, in conjunction with the amount of applied nitrogen fertilizer. We obtained a good agreement between observed average and simulated values. While the model performs well when spatially averaged values are used (root mean square error, RMSE = 1.4 mg l⁻¹ of NO₃⁻–N), the prediction error increases (RMSE = 1.9 mg l⁻¹ of NO₃⁻–N) when the concentration in each well is considered. This fact could be explained by the time and space scale of the experiment and the characteristics of the RISK-N model. The model is easy to use and seems appropriate for mid- and long-term studies of nitrogen contamination in groundwater for agricultural conditions in the Central Valley of Chile and under limited field data availability conditions. However, it needs to be tested for longer periods and under different climatic conditions, soil types, and aquifer characteristics, before its range of applicability can be fully established and recognized.     

The effect of vitamin E treatment on selected immune and oxidative parameters in Kivircik ewes suffering from transport stress

The study aimed to investigate the effects of vitamin E injection for the prevention of transport stress on ewes. Kivircik ewes (2–3 years old, n = 24) were randomly separated into three groups; G1 (Control) and G2 treated with 14 ml. saline as the placebo, G3 treated with 2100 IU/ind. DL-alpha-tocopherol acetate prior to transport. G2 and G3 were transported at 80 km/h for 4 h on a truck. Serum samples were obtained before (T0) and after (T1) transport. Serum cortisol, catalase, IgG, ceruloplasmin, C-reactive protein, complement component 4, interleukin-1 beta, tumour necrosis factor-alpha, glutathione peroxidase (GPx), superoxide dismutase, malondialdehyde analyses performed by ELISA, and serum alpha-tocopherol concentrations were evaluated by HPLC-UV. Wilcoxon and Kruskal–Wallis tests were used for statistical assessments (p < 0.05). Alpha-tocopherol concentrations were founded 1.22 ± 0.82, 0.27 ± 0.14 and 0.14 ± 0.07 µmol/L, respectively, in G1, G2 and G3 at T1. Alpha-tocopherol concentration decreased significantly in G2 between T0 and T1. GPx concentrations were increased twofold in G2 and G3 between T0 and T1 (p < 0.01). As a result, G2 alpha-tocopherol concentrations decreased but, the stress and oxidative parameters tested in this study were not affected by treating 2100 IU/ind. DL-alpha-tocopherol acetate before transport.     

重大件运输车辆安全性分析及基本流程框架图的建立

从可靠性、稳定性、通过性等方面分析重大件运输车辆的安全性，较详细阐述挂车可靠性中的挂车主梁弯矩、剪力和变形校核以及挂车的拼接校核、捆扎方式的稳定性、液压系统稳定性、挂车的三点支承稳定性、挂车的抗倾翻性以及抗侧滑性、塌点稳定性等问题，建立运输车辆的安全性分析基本流程框架图，指出保证重大件运输车辆安全稳定的要求。     

Response of some Andean cultivars of quinoa (Chenopodium quinoa Willd.) to temperature: Effects on germination, phenology, growth and freezing

This article presents various experiments conducted under semi-controlled conditions to determine the effects of temperature on germination, phenology, growth and freezing in Chenopodium quinoa, a pseudocereal originating from the cold and dry Andean altiplano. Traditional landraces and recently released cultivars from distinct geographical origins were compared in order to look for local adaptation or breeding improvement with respect to low temperatures. Germination was evaluated in 10 cultivars at temperatures between 2 and 20 °C. Plant growth and development were examined in three cultivars over the growing cycle, under minimum temperature between 8 and 13 °C and maximum temperature between 20 and 28 °C. The thermal time concept was used to compare the various treatments and estimate the phyllochron, as well as the base temperature and optimum temperature for leaf appearance, time to flowering and leaf width growth. Two cultivars at the vegetative stage were compared for night freezing tolerance down to −6 °C, registering leaf exotherms and plant survival rate. The influence of plant water status and the possible protective or detrimental role of leaf epidermal vesicles were also examined. Low temperatures down to 2 °C delayed germination without impeding it totally. Base temperature for germination varied between −1.9 and +0.2 °C, with negative values in 9 cultivars out of 10. Thermal sensitivity in germination was not related to the geographic origin of the cultivars. Leaf appearance and time to flowering showed similar base temperatures near 1 °C. Phyllochron varied from 12.9 to 17.2 °C d with lower values in the two recently released varieties than in the traditional landrace. Leaf width increased from a base temperature around 6 °C up to an optimum temperature between 20 and 22.5 °C. Freezing experiments showed that no plant could survive after 4 h at −6 °C, while no serious effect was noted down to −3 °C. Leaf exotherms confirmed that ice nucleation occurred between −5 and −6 °C in most of the plants, the traditional landrace showing a lower freezing tolerance than the selected line. Low leaf water status delayed the freezing process, while leaf vesicles did not seem to play any protective or detrimental role towards leaf freezing. Implications of these results for quinoa crop adaptation to the Andean environment are discussed.