放射性同位素示踪试验需要注意的若干问题

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。     

新型除草剂丙酯草醚的微量合成

从苯酚、对氨基苯甲酸和2-甲硫基-4,6-二氯嘧啶出发,建立了包含取代、氧化和缩合等7步反应的丙酯草醚除草剂微量制备方法。最终产物经制备HPLC纯化,其收率为53%,化学纯度大于98%,用MS(EI)、HPLC-MS1、H-NMR、UV等方法确认了丙酯草醚的结构。所建立的丙酯草醚微量制备方法,为放射性同位素标记丙酯草醚的合成奠定了基础。     

杀虫活性成分6β-丙氧基苦皮藤素Ⅴ的微量合成

苦皮藤根皮粉经苯回流提取、大孔树脂层析和硅胶层析后获得苦皮藤素Ⅴ。以正丙醇和苦皮藤素Ⅴ为原料,建立了基于无水碘代反应和威廉姆逊反应的6β-丙氧基苦皮藤素Ⅴ的微量合成方法,反应总收率约为17%。最终产物以HRMS、1H NMR和13C NMR确认为6β-丙氧基苦皮藤素Ⅴ。HPLC分析表明,该产物纯度大于98%。该方法为杀虫活性成分6β-丙氧基苦皮藤素Ⅴ的放射性同位素标记合成奠定了基础。     

杀虫活性成分6β-丙氧基苦皮藤素Ⅴ的微量合成

苦皮藤根皮粉经苯回流提取、大孔树脂层析和硅胶层析后获得苦皮藤素Ⅴ.以正丙醇和苦皮藤素Ⅴ为原料,建立了基于无水碘代反应和威廉姆逊反应的6β-丙氧基苦皮藤素Ⅴ的微量合成方法,反应总收率约为17%.最终产物以HRMS、1H NMR和13C NMR确认为6β-丙氧基苦皮藤素Ⅴ.HPLC分析表明,该产物纯度大于98%.该方法为杀虫活性成分6β-丙氧基苦皮藤素Ⅴ的放射性同位素标记合成奠定了基础.     

成都经济区放射性环境评价分析研究

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。     

花粉管通道法导入标记DNA在棉花胚珠内的分布

通过花粉管通道法将[α3-2P]dATP标记的DNA导入科棉1号,测量标记DNA在胚珠内的放射性活度并进行放射性自显影观察,以求获得陆地棉导入外源DNA的最佳时期和外源DNA在胚珠内的分布情况。结果表明,导入的外源DNA能进入到胚珠中;棉花授粉33h时通过滴涂和注射法导入标记DNA在胚珠内的放射性活度测量值均较高;而滴涂法的放射性活度明显低于注射法;胚珠内银粒的分布较明显,标记外源DNA的胚珠内银粒远多于对照。     

有机酸对液培玉米吸收137Cs和90Sr的影响

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。     

~7Be示踪技术在坡面土壤侵蚀研究中的应用

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。     

重离子注入与电离辐射作用下小麦种胚内非按期DNA合成的比较

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。     

花青素生物合成途径及关键酶研究进展

花青素是黄酮类多酚化合物,广泛分布于植物的果实、叶片、花瓣和种子中,使植物花和果实呈现出多种多样的色彩。作为纯天然的食用色素,花青素可以有效清除自由基,在抗氧化、抗衰老方面效果显著,同时,对于抗炎症、预防肥胖、预防慢性代谢性疾病、保护心血管、改善视力等也有良好的功效。近年来,关于花青素生物合成的研究已经成为植物次生代谢领域的热点问题,其中花青素的运输、积累以及体外合成有待深入研究。本文综述了花青素的结构、种类,重点对花青素的生物合成途径及合成关键酶研究进展进行总结,以期为后续进一步研究花青素在植物体内的合成机制及植物的分子改良提供参考。     

Simple method for 14C‐labelling root material for use in root decomposition studies

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.     

Ein Verfahren zur Messung der Verlagerungsrichtung von gelösten Pflanzenschutzmitteln im bewachsenen Boden

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.     

Occurrence,Degradation and Fate of Pesticides During Composting

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.     

Literature Review: Occurrence,Degradation and Fate of Pesticides During Composting: Part II: Occurrence and Fate of Pesticides in Compost and Composting Systems

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.     

Comparison of regulatory estimates of drinking water concentrations with monitoring data

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.     

Tolerance setting process in the U.S. Environmental Protection Agency

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.     

三唑类农药的微生物降解研究进展

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。     

Application of micellar electrokinetic capillary chromatography to the analysis of uncharged pesticides of environmental impact

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%.     

Investigation of Two Magnetic Permanently Confined Micelle Array Sorbents Using Nonionic and Cationic Surfactants for the Removal of PAHs and Pesticides from Aqueous Media

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.     

Determining organohalides in animal fats using gel permeation chromatographic cleanup: repeatability study

Evaluation of a previously published gel permeation chromatographic (GPC) procedure was undertaken to determine whether it can be used for additional organochlorine pesticides. After repeatability studies of many pesticides, the following compounds were approved for inclusion in the U.S. Department of Agriculture Domestic Residue Monitoring Program: coumaphos-S, stirophos, chlorpyrifos, ronnel, carbophenothion, chlorfenvinphos, phosalone, kepone, captan, linuron, and endosulfan I and II. Recoveries ranged from 54% for captan to 123% for ronnel. Ranges of CVs varied from 0-9.5% for carbophenothion to 7.1-47.7% for kepone. Although the minimum acceptable recovery of 50% was attained for all 12 pesticides, the anticipated CV of 20% was waived to include chlorpyrifos, endosulfan I and II, and kepone. For a multiresidue procedure involving approximately 40 compounds, these results were within the acceptable criteria.