首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 93 毫秒
1.
The spatial variation of soil erosion and deposition rates was studied in a small catchment cultivated by rainfed agriculture, in the Mouriki area, Viotia Greece, using the 137Cs technique. A 25 m grid was established parallel to the slope and the 137Cs inventories were defined for the grid points. After establishing the local reference inventory, the soil erosion and deposition rates were estimated using the 137Cs residuals for individual points on the grid in conjunction with the four conversion (calibration) models described by Walling and He (2001) [Models for converting 137Cs measurements to estimates of soils redistribution rates on cultivated and uncultivated soils]. The conversion models were validated by means of sensitivity analysis and using local experimental data. The resulting estimates of soil redistribution rates were interpolated by means of kriging, using Surfer Golden software. The magnitude of the soil erosion rates depend on many factors, including the location of the sampling point, the local slope, and the soil properties. The mass balance model 2 (MBM2) and mass balance model incorporating soil movement by tillage (MBM3) conversion models predict soil redistribution rates of the same order of magnitude as the experimental data and are able to take account of Chernobyl fallout. Predicted soil erosion rates for catchment grid varied from 6.71 to 85.55 t ha−1 per year using MBM2 and from 3.54 to 95.78 t ha−1 per year using MBM3. Deposition rates varied from 1.23 to 168.19 t ha−1 per year using MBM2 and from 3.24 to 189.18 t ha−1 per year using MBM3. High correlation was apparent between erosion/deposition rates (MBM2) and soil P (P<0.001), soil K (P<0.001), soil organic matter % (P<0.05), point slope (P<0.05), clay % (P=0.053) and altitude (P=0.057). The total soil losses from the catchment have been estimated at 18.34 t ha−1 per year using MBM2 and 22.12 t ha−1 per year using MBM3.  相似文献   

2.
本研究建立了检测牛肉中疯牛病特殊风险物质（主要是中枢神经组织）标记物GFAP mRNA的荧光RT-PCR检测技术。试验结果表明：该技术具有良好的种属特异性和组织特异性，只能从牛源和羊源的中枢神经组织中检测到GFAP，猪源和禽源检测结果为阴性，而且只有脑和脊髓等中枢神经组织产生阳性反应，其他内脏组织以及不同部位牛肉检测结果均为阴性；敏感性检测结果表明，该方法最低检测限达到0.001%以下；稳定性试验结果表明，100°C 加热处理30min对检测结果无明显影响，中枢神经组织在30°C以上室温可以稳定存放4天， 在4°C可以稳定冷藏2周，检测结果仍然为阳性。该结果显示，所建立的荧光RT-PCR技术用于牛肉中疯牛病特殊风险物质的检测具有特异性强、敏感性高、稳定性好及快速方便等优点，适合于在日常检测工作中推广使用。  相似文献   

3.
The occurrence of bovine spongiform encephalopathy (BSE) in Canada has resulted in the implementation of regulations to remove specified risk material (SRM) from the food chain. SRM includes the distal ileum of all cattle, and the skull, brain, trigeminal ganglia, eyes, palatine tonsils, and spinal cord and dorsal root ganglia of cattle ≥30 months of age. Composting may be a viable alternative to rendering for SRM disposal. In our study, two bulking agents, barley straw and wood shavings, were composted with beef manure along with SRM in passively aerated, laboratory-scale composters. Both composts heated rapidly, exceeding 55°C after 3 days with oxygen declining in the early composting stage with wood-shaving compost, but returning to near-original levels after 5 days. During composting the two matrices differed (P <0.05) only in water content, TC and bulk density. In the final compost, water content, TC and C/N ratio were higher (P < 0.05), while EC was lower (P < 0.05) in the wood shavings as compared to the straw compost. Approximately 50% of SRM was decomposed after 15 days of composting, with 30% of SRM being decomposed within the first 5 days. Phospholipid fatty acid (PLFA) profiles were used to characterize the microbial communities and showed that Gram positive bacteria were predominant in compost at day 5, a point that coincided with a rapid increase in temperature. Gram negative bacteria and anaerobes declined at day 5 but populations recovered by day 15. Fungi appeared to be suppressed as temperatures exceeded 55°C and did not appear to recover over the remainder of the composting period, with the exception of the straw compost at day 15. On day 5, Actinomycetes increased in the straw compost, but declined in the wood shavings compost, with this group increasing in both types of compost at day 15. Although temporal changes were evident, compost matrices or depth within the composter did not obviously influence microbial communities. Decomposition of SRM also did not differ between compost matrices or with depth in the composters. These results suggest that SRM decompose rapidly during composting and that both mesophilic and thermophilic microbial communities play a role in its decomposition.  相似文献   

4.
The commercialization of animal feeds infected by prions proved to be the main cause of transmission of bovine spongiform encephalopathy (BSE). Therefore, feed bans were enforced, initially for ruminant feeds, and later for all feeds for farmed animals. The development and validation of analytical methods for the species-specific detection of animal proteins in animal feed has been indicated in the TSE (Transmissible Spongiform Encephalopathies) Roadmap (European Commission. The TSE (Transmissible Spongiform Encephalopathy) roadmap. URL: http://europa.eu.int/comm/food/food/biosafety/bse/roadmap_en.pdf, 2005) as the main condition for lifting the extended feed ban. Methods based on polymerase chain reaction (PCR) seem to be a promising solution for this aim. The main objective of this study was to determine the applicability of four different real-time PCR methods, developed by three National expert laboratories from the European Union (EU), for the detection and identification of cattle or ruminant species in typical compound feeds, fortified with meat and bone meals (MBM) from different animal species at different concentration levels. The MBM samples utilized in this study have been treated using the sterilization condition mandatory within the European Union (steam pressure sterilization at 133 degrees C, 3 bar, and 20 min), which is an additional challenge to the PCR methods evaluated in this study. The results indicate that the three labs applying their PCR methods were able to detect 0.1% of cattle MBM, either alone or in mixtures with different materials such as fishmeal, which demonstrates the improvement made by this technique, especially when compared with results from former interlaboratory studies.  相似文献   

5.
In response to needs for analytical standards by researchers studying the exposure of humans to lead, a wide variety of environmental and "food" Standard Reference Materials have been prepared and certified for lead as well as for many other elements. Among the food types are SRM 1571, Orchard Leaves, 45 ppm; SRM 1575, Pine Needles, 10.8 ppm; SRM 1573, Tomato Leaves, 6.3 ppm; SRM 1566, Oyster Tissue, 0.48 ppm; SRM 1577, Bovine Liver, 0.34 ppm; SRM 1568, Rice Flour, 0.045 ppm; and SRM 1567, Wheat Flour, 0.020 ppm. These materials, intended for use in calibrating instruments and methods, have been certified by a definitive method, isotope dilution mass spectrometry. The advantages and disadvantages of this technique are discussed and some suggestions for the use of its isotopic selectivity in the study of lead in the human environment are presented.  相似文献   

6.
Meat and bone meal (MBM) is a high protein agricultural commodity that currently has few applications other than as an animal feed. Unmodified MBM has poor functional properties, due to its low solubility. Our results from pilot plant trials demonstrate that MBM can be extrusion-processed along with sodium caseinate to produce a useful plastic material. We developed this material for use as a dog chew toy. For this application, elastic modulus (stiffness) is a key characteristic. Our results detail the relationship between ambient relative humidity and equilibrium moisture content (MC) in the material. The influence of MC on the glass transition temperature and elastic modulus reflects the plasticization of this material by water. On the basis of a comparison to a commercially available dog chew, the range of stiffness achievable with our material, 0.25-2.50 GPa, encompasses the values appropriate for a dog chew. Our results show that a particular desired stiffness can be maintained by applying an edible moisture barrier to the surface of the material.  相似文献   

7.
应用美国的RBCA模型和荷兰的Csoil模型对某挥发性有机物污染场地中的2种主要污染物1,2-二氯丙烷和1,2-二氯乙烷进行健康风险评价。结果表明,2种模型计算出的健康风险基本一致,除14号采样点存在潜在的健康风险外,其余各采样点的健康风险均在可接受的范围内。由土壤污染引起的各暴露途径中,直接经口摄入途径引起的健康风险最大,占65%以上;皮肤接触途径次之;呼吸摄入途径最小。在呼吸暴露途径中,室内挥发暴露明显比室外挥发暴露的健康风险大。Csoil模型计算出的所有采样点由地下水暴露途径引起的健康风险都超过土壤,说明由地下水暴露引起的健康风险不容忽视。RBCA模型在考虑地下水暴露途径时仅考虑了饮水摄入这一途径,与RBCA模型相比,Csoil模型在进行健康风险评价时特别考虑了洗澡暴露途径,对于地下水受到污染的场地来说,Csoil模型考虑得更全面,使用Csoil模型进行健康风险评价更具有针对性。  相似文献   

8.
Abstract

The nitrogen and phosphorus contents of meat and bone meal (MBM) make it a potentially valuable nutrient source in agriculture. Its narrow N:P ratio, however, makes it a potential environmental risk if it is not utilized with caution. A column-leaching experiment was conducted to assess potential nitrogen and phosphorus leaching from bare soils fertilized with MBM. This should give an idea of the efficacy of autumn or early spring MBM application on land devoid of vegetation cover. Earlier greenhouse and field experiments have indicated that nitrogen mineralization after MBM application takes place relatively rapidly. The column experiment conducted here has indicated that spring application of MBM prior to planting can result in the loss of mineral nitrogen, reducing the total amount of N available to the crop. A higher initial loss (up to 47 mg l?1) of ammonium was found for the MBM treated soils, but this declined to less than 0.1 mg l?1 by the end of the experiment, 11 weeks later. Nitrate loss was highest at the onset of the experiment for the soils that received mineral N fertilizer. With time, however, the largest nitrate losses were associated with the MBM-treated soils. Nitrate leaching continued to well beyond the end of the experiment. The effect will most certainly be exacerbated when the crop N (rather than crop P) requirement forms the basis for MBM application. The amount of P leached as ortho-P is probably small but may also represent an environmental risk if N remains to be the basis of MBM application. Based on the results presented here and considering the dangers of elevated nutrient losses, autumn and early spring MBM application may not be recommended.  相似文献   

9.
解释结构模型在中国疯牛病风险识别中的应用研究   总被引：3，自引：0，他引：3  
疯牛病是一种严重危害牛类健康的疾病，它的感染因子可以传染给人类。因此这种疾病也威胁着人类的健康。我国目前还没有检测到疯牛病的存在。本文利用解释结构模型对疯牛病风险因素进行了定性评估。通过对模型进行运算求解得出清晰的结论：评估国反刍动物饲料中含有PrP^BS因子、评估国羊只患痒病和评估国牛患疯牛病包含在同一强连通域。  相似文献   

10.
Abstract

A 2:1 nitric/perchloric acid plant digest was developed and tested as a replacement of the standard Kjeldahl digest for determining phosphorus concentrations in Pinus ponderosa Laws. needles and roots. Time sequence studies using the National Institute of Standards and Technology (NIST) pine standard reference material (SRM #1575) showed increased recovery of phosphorus as digest time increased from 1.5 to 16 hours. Digest intervals greater than 16 hours did not increase phosphorus recovery; the phosphorus concentration leveled off within the NIST reference material certified range. Using P ponderosa needle and root samples, a linear regression comparison determined that two sets of nitric/perchloric digests yielded 3.4% higher phosphorus concentrations than the Kjeldahl digest. However, 99 sets of nitric/perchloric digests, each containing two NIST standard reference materials (SRM), yielded an approximately normal distribution of phosphorus concentrations, all agreeing with the Kjeldahl established concentration and within the NIST SRM certified range. The 3.4% difference in phosphorus concentrations was consistant with the observed variability among sets. In conjunction with new elemental combustion methods for determining plant nitrogen, the nitric/perchloric digest can replace a Kjeldahl digest for determining plant phosphorus while determining additional plant cations not available using a Kjeldahl digest method.  相似文献   

11.
This study was carried out to obtain a representative set of data on long-term erosion rates from a pilot area located close to the Jaslovske Bohunice village, in western Slovakia using the 137Cs-method. The study area chosen was representative of the hilly loess cultivated areas of Slovakia. The sampling strategy was based on a multiple transect approach. Analyses of the samples for 137Cs activity were made at the Nuclear Power Plant Research Institute, Jaslovske Bohunice. The 137Cs-method was used to obtain long-term estimates of soil erosion in the Jaslovske Bohunice site, a representative hilly loess cultivated area of Slovakia. The estimated reference 137Cs inventory was 2910 Bq m−2, with a coefficient of variation of 4.3%.Examination of the 137Cs redistribution in relation to the topography of the study area revealed that, within individual transects the 137Cs inventories were closely related to major landforms. The 137Cs inventories were considerably lower on the slopes than on the plateau and they were highest in the valley. However, when plotted against a selection of individual quantitative slope parameters, i.e. the S and the LS factors of the USLE or slope inclination, the correlations obtained were weak.Three conversion models, i.e. the proportional model (PM), the simplified mass balance model (MBM1) and the standard mass balance model (MBM2), from the set of models developed at Exeter University, Great Britain were selected to interpret the resulting 137Cs measurements into soil erosion/deposition rates. The mean erosion rates estimated with the PM were 22.4, 35.6 with MBM1 and 17.3 t ha−1 per year with MBM2. There was a good agreement between the average of these mean erosion rates (25.1 t ha−1 per year) for the Jaslovske Bohunice site and the estimated mean soil erosion rate obtained for small erosion plots (15 t ha−1 per year) for conditions similar to the study site. Nevertheless, further research on the application of the 137Cs-method, in particular the independent validation of the results obtained, is needed. Several issues requiring further study have been highlighted.  相似文献   

12.
For the detection of prohibited meat and bone meal (MBM) in animal feed, monoclonal antibodies (MAbs) were raised against heat-stable h-caldesmon purified from bovine intestinal smooth muscle. The obtained hybridoma cells were screened against extracts of the bovine MBM and heat-treated smooth muscle, and MAb 5E12 was identified as having the best performance. Antibody 5E12 did not react with animal feed, milk product, plant proteins, and other ingredients used for commercial animal feed except for the gelatin. This antibody diluted to 100-fold was able to detect MBM mixed in animal feed at 0.05% in an ELISA, and it showed strong affinity toward bovine smooth muscle autoclaved at 130 degrees C. Therefore, this antibody can be used in the ELISA system for field testing of the presence of MBM in animal feed.  相似文献   

13.
为了能更加快速准确的定性判别鱼粉中是否掺有肉骨粉（MBM）,该文收集中国常用的鱼粉和肉骨粉,制备定标集样品201个,其中111个为掺有不同肉骨粉质量分数（1%～33%）的样品,90个为纯鱼粉,并独立制备113个验证集样品,其中74个为掺有不同肉骨粉质量分数（1%～33%）的样品,39个为纯鱼粉。在400～2 498 nm波长范围内进行光谱扫描,选择合适的光谱预处理方法和光谱范围,采用DPLS方法建立判别分析模型。建立的判别分析模型：数学预处理方法为2-8-6-1,散射校正方法为变量标准化处理（SNV）,光谱范围为全谱（408～ 2 492 nm）,定标模型的正确判断率为95.7%,外部验证正确判断率为95.6%,对于掺入量≥5%MBM时,正确判断率为100%。研究结果证明近红外反射光谱可以提供一种快速鉴别鱼粉中MBM的方法。  相似文献   

14.
Trace element-contaminated soils (TECSs) are one of the consequences of the past industrial development worldwide.Excessive exposure to trace elements (TEs) represents a permanent threat to ecosystems and humans worldwide owing to the capacity of metal(loid)s to cross the cell membranes of living organisms and of human epithelia,and their interference with cell metabolism.Quantification of TE bioavailability in soils is complicated due to the polyphasic and reactive nature of soil constituents.To unravel critical factors controlling soil TE bioavailability and to quantify the ecological toxicity of TECSs,TEs are pivotal for evaluating excessive exposure or deficiencies and controlling the ecological risks.While current knowledge on TE bioavailability and related cumulative consequences is growing,the lack of an integrated use of this concept still hinders its utilization for a more holistic view of ecosystem vulnerability and risks for human health.Bioavailability is not generally included in models for decision making in the appraisal of TECS remediation options.In this review we describe the methods for determining the TE bioavailability and technological developments,gaps in current knowledge,and research needed to better understand how TE bioavailability can be controlled by sustainable TECS management altering key chemical properties,which would allow policy decisions for environmental protection and risk management.  相似文献   

15.
基于土地利用的陕西省生态风险分析   总被引：4，自引：2，他引：2  
刘引鸽 《水土保持通报》2011,31(3):180-184,189
土地利用变化对陆地生态系统产生了很大的影响。利用陕西省土地和社会经济环境资料,分析了土地利用变化趋势。采用层次分析法与综合指数法,建立了自然压力、社会环境压力、经济压力生态风险指标体系,估算了耕地、林地、牧草地、水域等土地利用结构生态风险以及综合风险。结果表明,绝对数量变化幅度最大的是耕地和林地,而且耕地生态风险最大,水域变化生态风险最小,不同土地利用类型生态风险指数大小顺序为：耕地〉林地〉居民点及工矿用地〉牧草地〉未利用地〉交通用地〉水利设施用地。土地生态压力风险中,以经济压力生态风险最大,其次是自然压力生态风险,社会环境压力生风险相对较小,土地生态综合风险呈增加趋势。生态风险变化与土地利用结构的不合理,人口增加,水资源量减少以及自然灾害增加密切相关。  相似文献   

16.
The removal of central nervous system (CNS) tissues as part of bovine spongiform encephalopathy (BSE) risk material is one of the highest priority tasks to avoid contamination of the human food chain with BSE. No currently available method enables the real-time detection of possible CNS tissue contamination on carcasses during slaughter. The fluorescent pigment lipofuscin is a heterogeneous, high-molecular weight material that has been shown to be enriched in high concentrations in neuronal tissues. In this study, lipofuscin fluorescence was investigated as a marker for real-time detection of CNS contamination. Front-faced fluorescence spectra of brain and spinal cord samples from 11 cattle gave identical, reproducible fluorescence signal patterns with high intensities. The specificity of these spectra was assessed by investigating 13 different non-CNS tissues enabling the differentiation of brain and spinal cord by signal intensity and structure of the spectra, respectively. Small quantities of bovine spinal cord were reliably detected in the presence of raw bovine skeletal muscle, fat, and vertebrae. The presented data are a fundamental basis for the development of a prototype device allowing real-time monitoring of CNS tissue contamination on bovine carcasses and meat cuts.  相似文献   

17.
The discovery of acrylamide (AA) in many common cooked starchy foods has presented significant challenges to toxicologists, food scientists, and national regulatory and public health organizations because of the potential for producing neurotoxicity and cancer. This paper reviews some of the underlying experimental bases for AA toxicity and earlier risk assessments. Then, dietary exposure modeling is used to estimate probable AA intake in the U.S. population, and physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) modeling is used to integrate the findings of rodent neurotoxicity and cancer into estimates of risks from human AA exposure through the diet. The goal of these modeling techniques is to reduce the uncertainty inherent in extrapolating toxicological findings across species and dose by comparing common exposure biomarkers. PBPK/PD modeling estimated population-based lifetime excess cancer risks from average AA consumption in the diet in the range of 1-4 x 10 (-4); however, modeling did not support a link between dietary AA exposure and human neurotoxicity because marginal exposure ratios were 50-300 lower than in rodents. In addition, dietary exposure modeling suggests that because AA is found in so many common foods, even big changes in concentration for single foods or groups of foods would probably have a small impact on overall population-based intake and risk. These results suggest that a more holistic analysis of dietary cancer risks may be appropriate, by which potential risks from AA should be considered in conjunction with other risks and benefits from foods.  相似文献   

18.
Different forms and solutions of the single root model (SRM) arise from: assumed functional relationships between the radius of the SRM soil cylinder and the rooting density (Lr); averaging modes of hydraulic conductivity (K); steady-state or steady-rate flow assumption; and methods of evaluating the root geometry factor (B). SRM forms and solutions, in particular B approximations, were evaluated by analytical comparison and by performance, when incorporated into a water uptake simulation model for oats. The approximation of B as a constant, or as an exponential function of rooting density (B′), had only a small temporary effect on soil water extraction rates and potentials at the soil—root interface. A combination of B′ with exponential rooting profile estimation is proposed as an optimal SRM form for water uptake analysis. It is shown (in appendices) that: (1) assuming SRM steady-state flow to originate on average from the volumetric middle of the SRM soil cylinder is nearly equivalent to the assumption of a steady-rate flow; and (2) utilizing a geometric mean K for the SRM soil cylinder may cause soil water extraction rates to be underestimated.  相似文献   

19.
北京市土壤重金属潜在风险预警管理研究   总被引：7，自引：0，他引：7  
区域土壤重金属的潜在环境质量风险预警研究是区域土壤重金属管理研究的热点之一。以北京市为研究区,在镇域尺度上建立土壤重金属输入-输出通量模型和重金属年累积率模型,计算2006年北京市各乡镇Cr、Ni、Zn、Hg、Cu、As、Cd、Pb八种重金属的通量和累积量。以2006年作为基期年,采用指示克里格法预测北京市未来30 a土壤重金属含量变化趋势和环境质量风险。研究表明,在当前发展趋势下,未来30a北京市Pb、Cr和Ni土壤环境污染风险较小,含量均处于国家土壤环境质量二级标准以下;Cu、As和Zn最高达到中警级别,Hg和Cd的污染风险变异较大,各预警级别均有出现,但概率大小不等,其中Cd的环境风险最为严重,高风险区部分位于北京市东部,呈带状分布;Hg的环境高风险区域随城市的扩张而蔓延。采用地统计学与区域物质流通量模型结合的方法,可为区域土壤重金属的宏观预警研究提供技术支撑。  相似文献   

20.
In this paper the risks that occur in testing compliance with air quality standards are defined and discussed. These risks result from the definition of suitable probability distribution parameters, from the substitution of ‘immission doses’ by ‘immission’ concentrations, from information theory aspects of the space-time assessment, and from the imperfection of measurement devices. In a similar way as has been followed up in an earlier paper concerning the derivation of air quality standards the procedure of testing complicance with standards has been divided into single logical steps. A global risk, defined as the probability for a wrong decision is derived from the risks occurring in the derivation of standards and those occurring in compliance tests. This global risk has to be accepted in monitoring air quality.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号