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放射性同位素示踪试验需要注意的若干问题 总被引：1，自引：0，他引：1
本文对目前国内放射性同位素示踪试验过程中有关示踪剂选择、引入量估算、示踪剂引入方法、放射性样品预处理以及放射性测量方法(尤其是液体闪烁测量)中所存在的常见问题进行了简要剖析,以期对从事放射性同位素示踪研究的人员有所助益。 相似文献
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成都经济区放射性环境评价分析研究 总被引：1，自引：0，他引：1
运用区域1/25万土壤化探数据中铀、钍、钾的含量数据,对成都经济区的放射性水平进行了评价。介绍了放射性核素含量分布情况和环境放射性水平,通过成都经济区地质情况和成都经济区放射性环境分布情况,分析了地质条件对成都经济区环境放射性的影响,并初步研究了地质条件影响放射性水平的原因。最后总结了成都经济区地质环境对天然放射性水平分布情况的影响规律:除龙门山褶皱带和峨眉山-瓦山断块少部分地区外,绝大部分地区γ射线内外照射指数都在国家建筑材料放射性核素限量标准控制式的范围内;地质构造、地表出露岩层和地表水对放射性水平有较大的影响。 相似文献
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利用液培方法研究胡敏酸钠等有机酸盐作用下玉米幼苗对放射性核元素137Cs和90Sr的吸收速率。研究结果表明:利用有机酸盐可以降低玉米幼苗对放射性核元素的吸收速率。1低活度放射性核素水平下,对照(不加有机酸盐)的玉米幼苗中发现了97%放射性核元素137Cs,而高活度放射性核素水平中为61%;有机酸盐不同程度地降低了玉米幼苗中放射性核元素137Cs的量。在低活度水平中四苯硼钠降低137Cs的量最多, 玉米仅吸收12%,而酒石酸钾钠处理中玉米吸收量最高,为45.5%。对137Cs的吸收率,在胡敏酸钠处理中为23.9%, EDTA-Na处理中为41.3%;在高活度放射性核素水平中吸收率的顺序为四苯硼钠11%,胡敏酸钠26%,酒石酸钾钠28.7%,EDTA-Na 37%。2低活度水平下,对照中放射性核元素90Sr的56%被玉米幼苗吸收,而高活度水平中达61%。有机酸盐在低活度水平中降低放射性核元素90Sr的顺序为胡敏酸钠 23.9%,EDTA-Na 26%,酒石酸钾钠28%和四苯硼钠36%;在高活度水平中为四苯硼钠11%,EDTA-Na 24%,胡敏酸钠26%,酒石酸钾钠 31%。3低活度和高活度水平中,四苯硼钠和胡敏酸钠降低玉米幼苗体内的放射性核元素性质为最佳。4所有有机酸盐处理与对照之间的差异都达到极显著水平。 相似文献
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利用放射性核素示踪研究土壤侵蚀已成为国际社会普遍关注的热点问题之一。7Be是一种在地球大气中由于宇宙射线轰击氧原子和氮原子靶核而产生的一种天然放射性核素,作为一种自然产生的、短寿命的放射性核素,它具有同137Cs2、10Pb、226Ra等放射性核素相似的示踪价值。介绍了7Be的应用背景、来源、示踪原理和7Be示踪技术现有的土壤侵蚀速率定量估算模型,提出了在我国应用7Be示踪技术开展土壤侵蚀的建议。 相似文献
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用放射性同位素￣３Ｈ－胸腺嘧啶核苷渗入法，研究Ｆｅ￣（１＋）注入与￣（６０）Ｃｏγ射线辐照条件下，小麦种子萌发早期种胚内ＤＮＡ的合成动态，以非按期ＤＮＡ合成为标志，比较重离子束与γ射线作用下ＤＮＡ损伤、修复程度的差异。同时采用扫描电镜Ｘ射线能谱分析法（ＳＣＥ－ＥＤＡＸ）对造成这种差异的机制进行了探讨研究。研究结果表明，γ射线辐照后，种胚内存在典型的非按期ＤＮＡ合成，但在重离子注入条件下，这一现象并未表现出来。因此重离子的作用过程和诱变机理与γ射线的作用有所不同。重离子对种子的诱变是一种间接的作用，因为ＳＣＥ－ＥＤＡＸ的结果证明离子注入种子的深度为１４μｍ，并未真正到达小麦种胚内部。 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(15-16):2737-2743
Abstract A method was devised in which plant roots can be easily and uniformly radiolabelled with 14C for use in soil decomposition studies. The roots were labelled from an exogenous sugar solution for a total period of 48 hours after which root decomposition studies could be performed. The method offers distinct advantages over the existing constant 14C‐CO2 atmosphere labelling method. 相似文献
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A procedure to measure the direction of translocation of solved pesticides in planted soil In an experimental pot, which permits the airtight isolation of the root region, the rooted and non-rooted soil compartment are separated by stainless steel wire nets. The translocation and mineralisation of a pesticide can be studied by alternative application of radioactive labelled compounds to either one of the compartments. As an example results with 14C-atrazine are discussed. 相似文献
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Fatih Büyüksönmez Robert Rynk Thomas F. Hess Edward Bechinski 《Compost science & utilization》2013,21(4):66-82
This paper reviews the findings of research reported in the currently available literature regarding the occurrence and transformations of pesticides through the composting process and the use of compost. Part I summarizes the composting process, pesticides and mechanisms of pesticide degradation. Part II reviews research studies concerning the occurrence and fate of pesticides during composting. Investigations of pesticide residues in composting feedstocks and finished compost detected few of the target pesticides. The compounds that were found occurred at low concentrations. The majority of the compounds detected were insecticides in the organochlorine category, including chemicals that have been banned from use in the U.S. for many years. Generally, organophosphate and carbamate insecticides and most herbicides were rarely detected. Comparisons of pesticide concentrations before and after composting also showed organochlorine compounds to be most resistant to biodegradation during composting. With some exceptions, pesticides in other categories decomposed moderately well to very well. Studies that followed the mechanisms of degradation indicate that mineralization accounts for only a small portion of pesticide disappearance. Other prominent fates include partial degradation to secondary compounds, adsorption, humification, and volatilization. In general the research results suggest that the pattern of pesticide degradation during composting is similar to the degradation observed in soils. With a few important distinctions, composting can be considered a biologically active soil environment in which degradation is accelerated. However, as some studies noted, composting does not always speed the degradation of all pesticides. The nature of the pesticide, specific composting conditions and procedures, the microbial communities present, and the duration of composting affect the extent and the mechanisms of degradation. 相似文献
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Fatih Büyüksönmez Robert Rynk Thomas F. Hess Edward Bechinski 《Compost science & utilization》2013,21(1):61-81
This paper reviews the findings of research reported in the currently available literature regarding the occurrence and transformations of pesticides through the composting process and the use of compost. Part I summarizes the composting process, pesticides and mechanisms of pesticide degradation. Part II reviews research studies concerning the occurrence and fate of pesticides during composting. Investigations of pesticide residues in composting feedstocks and finished compost detected few of the target pesticides. The compounds that were found occurred at low concentrations. The majority of the compounds detected were insecticides in the organochlorine category, including chemicals that have been banned from use in the U.S. for many years. Generally, organophosphate and carbamate insecticides and most herbicides were rarely detected. Comparisons of pesticide concentrations before and after composting also showed organochlorine compounds to be most resistant to biodegradation during composting. With some exceptions, pesticides in other categories decomposed moderately well to very well. Studies that followed the mechanisms of degradation indicate that mineralization accounts for only a small portion of pesticide disappearance. Other prominent fates include partial degradation to secondary compounds, adsorption, humification, and volatilization. In general the research results suggest that the pattern of pesticide degradation during composting is similar to the degradatiion observed in soils. With a few important distinctions, composting can be considered a biologically active soil environment in which degradation is accelerated. However, as some studies noted, composting does not always speed the degradation of all pesticides. The nature of the pesticide, specific composting conditions and procedures, the microbial communities present, and the duration of composting affect the extent and the mechanisms of degradation. 相似文献
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Jones RL 《Journal of agricultural and food chemistry》2005,53(22):8835-8839
Currently, regulatory practice in the United States is to estimate potential concentrations in drinking water from surface water by using an index reservoir scenario. This approach extrapolates results from the modeling of a single field with maximum application rates to the watershed scale, based on a percent crop area estimate. Since 1998, Bayer CropScience and its predecessor companies have conducted drinking water monitoring studies with a number of different compounds. The results from these studies show that the index reservoir scenario greatly overpredicts residues in surface water. The most important factor is the overestimation of use within a watershed. Other factors contributing to the overestimation of concentrations are the conservative procedures used to obtain the chemical fate related input parameters and the simplified hydrology. A new procedure based on the USGS WARP model, being developed by a group of scientists from the EPA, USGS, USDA, and industry, will provide more realistic estimates of concentrations of pesticides and their metabolites in drinking water. 相似文献
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C L Trichilo R D Schmitt 《Journal of the Association of Official Analytical Chemists》1989,72(3):536-538
The U.S. Environmental Protection Agency (EPA) is responsible for setting tolerances for pesticide residues in food, under the authority of the Federal Food, Drug, and Cosmetic Act. The residue chemistry data required to set tolerances include metabolism in plants and animals, analytical methods, magnitude of the residue, and concentration in processed foods. A key aspect of tolerance-setting procedures is the identity of the residue in the matrix of concern; without knowledge of the chemical moieties that occur as residues, it is impossible to develop suitable methods or generate meaningful residue data. For new chemicals, EPA carries out a single-laboratory validation of the analytical method needed to generate residue data and to enforce tolerances. Tolerance enforcement methods need to be rapid and inexpensive and to use commercially available equipment and reagents. Methods are more complex for many newer pesticides, which are polar compounds that leave low levels of residue. EPA now requires that the registrants of older pesticides, for which methods are not acceptable by today's standards, must develop better methods. 相似文献
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三唑类农药是一种广泛使用的防治植物病害的杀菌剂和植物生长调节剂，可通过抑制麦角甾醇的合成阻碍病原菌的细胞壁形成，从而起到防治作物病害的作用，也能抑制植物赤霉素合成延缓植物生长；但因大范围应用及其难以降解的特性，污染环境和影响人类健康。为给三唑类农药的微生物降解提供参考，基于文献研究，梳理总结了三唑类农药降解菌的种类、影响降解的环境因素和降解机理方面的研究进展，明确了微生物在不同环境中能有效降解三唑类农药，微生物降解技术有望应用于治理三唑类农药造成的环境污染。 相似文献
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Segura Carretero A Cruces-Blanco C Cortacero Ramírez S Carrasco Pancorbo A Fernández Gutiérrez A 《Journal of agricultural and food chemistry》2004,52(19):5791-5795
A test mixture of five pesticides and metabolites (naphthalene acetamide, carbaryl, 1-naphthol, thiabendazole, and carbendazime) has been investigated by capillary electrophoresis with an ultraviolet diode array detector. These compounds were separated in <10 min by micellar electrokinetic capillary chromatography (MEKC). MEKC was performed in 30 mM ammonium chloride/ammonia buffer (pH 9.0) containing 15 mM sodium dodecyl sulfate. The lowest detection limit was obtained for the insecticide carbaryl (0.22 microg mL(-)(1)) and the highest for its metabolite 1-naphthol (1.13 microg mL(-)(1)). This method was applied to the analysis of the pesticides in cultivated vegetables such as cucumbers, which were extracted with a liquid-liquid extraction procedure, obtaining recovery percentages ranging from 90.1 to 110.2%. 相似文献
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Surfactants have been used for environmental remediation to remove hydrophobic organic compounds (HOCs) in water and soil. However, there are limited studies on the use of surfactants in confined micelle arrays to remove pesticides and polycyclic aromatic hydrocarbons from water. We studied the recovery of HOCs using two confined surfactants: nonionic Triton X-100 and cationic 3-(trimethoxysily)propyl-octadecyldimethyl-ammonium chloride (TPODAC). The micelle arrays were confined on a mesoporous silica matrix deposited onto a magnetic iron core. These magnetic, dispersible sorbents can be used to recover HOCs, minimizing the application of surfactants when compared to soil-washing techniques. The TPODAC-based sorbent had better average recovery of the HOCs studied compared to the Triton-X sorbent, and was, in general, comparable to activated carbon. It performed well with the chlorinated pesticides, in part due to additional interactions between the cationic sites and the polar compounds. 相似文献
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B M McMahon J A Burke 《Journal of the Association of Official Analytical Chemists》1987,70(6):1072-1081
Foods analyzed for pesticide residues in the monitoring programs of the U.S. Food and Drug Administration (FDA) are most often examined by using one or more of the multiresidue methods developed for this purpose over the years. Because no single method can be used for all potential residues, each commodity is examined by a method or methods which will identify and/or determine the chemicals most likely to have been used. FDA conducts research to develop new multiresidue methods, which are included in monitoring programs as needed to cover additional chemicals. FDA's multiresidue methods have undergone continuous study over a 20 year period to ascertain which compounds can and cannot be recovered by them. FDA continues to perform tests to discover a compound's analytical characteristics. Protocols have been published to direct the testing of additional compounds so that new information can be added to the existing compilations. Methods capable of determining residues of single pesticides are used to analyze selected commodities for residues of high priority that cannot be determined by existing multiresidue methods. Pestrak, a computerized listing of pesticide analytical information, has been developed by FDA to keep track of the capabilities of multiresidue methods and the coverage of residues by the single residue methods used in FDA monitoring. 相似文献