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施肥对叶类蔬菜硝酸盐含量的影响 总被引:34,自引:1,他引:33
综述施肥种类、数量、时期、方法以及肥料配合等对叶类蔬菜硝酸盐含量的影响 ,重点讨论氮肥施用技术与蔬菜硝酸盐累积的关系 ,并提出今后在这方面的主要研究方向。 相似文献
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分析了硝酸镁法生产浓硝酸过程中稀硝酸镁含硝量高的危害性。通过采取加强对加热器的维护、优化硝酸镁沉降方法和改变硝酸镁投料方式等一系列优化改进措施,提升了浓硝酸装置连续运行能力,降低了装置综合能耗。 相似文献
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通过氮浓度调节塔玛亚历山大藻毒素产量的初步研究 总被引:5,自引:0,他引:5
初步研究了培养基中氮浓度及补加氮对塔玛亚历山大藻毒素产量的影响. 低氮(88.2 mmol/L)条件下藻细胞具有较高的比生长速率(0.60 d-1),是高氮(882 mmol/L)下的约1.2倍. 低氮下在藻细胞对数生长的末期(第10天)补加氮(至高氮水平)导致塔玛亚历山大藻的最大细胞密度(48.5′103 mL-1)明显增加,分别是低氮(6.28′103 mL-1)和高氮(21′103 mL-1)下的7.7和2.3倍;最大单位细胞毒素含量(1.26 pg/cell)和产量(43.51 mg/L)分别是低氮(1.09 pg/cell和6.49 mg/L)和高氮(0.88 pg/cell和13.18 mg/L)下的1.2, 1.4倍和6.7, 3.3倍. 结果显示,在培养基中低水平氮、磷条件下塔玛亚历山大藻细胞的毒素合成增加,其中特别是磷限制条件下,藻细胞的毒素含量增加更为显著. 通过低氮下补加氮源以维持培养基中的低氮水平,可以显著促进塔玛亚历山大藻细胞的毒素产量. 相似文献
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Philip M. Tucker Michael J. Waite Brian E. Hayden 《Journal of Applied Electrochemistry》2004,34(8):781-796
Electrodeposited rhodium films on titanium substrates have been electrochemically activated to produce a high area surface with a specific activity for nitrate electroreduction directly to N2. The activation process involves oxidation/reduction cycles in an alkaline, KCl electrolyte containing nitrate ions. Surfaces of up to 230 times the geometric area are achieved, together with a surface morphological modification. While the active surface, once formed, is intrinsically unstable during long-term nitrate reduction, its activity can be maintained in situ by an electrochemical cycling procedure. The high area rhodium has the form of a nano-structured sponge, with a surface area of ca. 19 m2 g–1. The morphological modification is evidenced by a change in the hydrogen UPD structure, changes in the surface redox behaviour associated with OH adsorption, and a reduction in the activation energy for nitrate reduction from ca. 47 to 20 kJ mol–1. The reduction in activation energy, however, is accompanied by a decrease in the pre-exponential factor, and this apparent compensation effect results in similar rate constants on the activated and unactivated surfaces. The enhancement in the catalyst's activity for nitrate reduction results from an increase in the relative activity of nitrate reduction over water reduction. The activated catalyst sustains steady state nitrate reduction at an increased over-potential before the reaction to N2 decays, and hydrogen evolution and reduction to ammonia take place. The presence of nitrate ions is essential for the formation of the active surface, and specifically adsorbed nitrate ions and reductive intermediates are present at the surface when it is reformed. A mechanism for the elementary surface reaction steps involved in nitrate reduction, and the apparent habit growth of the active surface phase in the nitrate containing solution is discussed. 相似文献
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蔬菜中硝酸盐累积现状与控制对策 总被引:1,自引:0,他引:1
本文概述了蔬菜中硝酸盐的污染现状和长期食用高含量硝酸盐食品对人体的危害,指出了蔬菜中硝酸盐的分布规律和影响蔬菜中硝酸盐累积的因素,提出了现阶段减少了硝酸盐污染的控制对策。 相似文献
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水体中的氮是引起富营养化的主要污染物,而分析监测水体中的硝酸盐和亚硝酸盐含量,控制水体中的氮污染物,对水资源循环利用和发展意义重大。文章概述了可见分光光度分析法和流动注射法测定水体中的硝酸盐和亚硝酸盐,就这两种方法在近十年来前人在测定硝酸盐和亚硝酸盐方面做过的工作和进行过的探讨做一个总结。 相似文献
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M. T. Adetunji 《Nutrient Cycling in Agroecosystems》1994,37(2):159-163
The effect of nitrogen fertilizer application on nitrate leaching and contamination of underground and surface waters in a continuously cropped lowland area of South Western Nigeria has indicated a high potential for nitrate leaching.It was estimated that with 100 kg N ha–1 applied, as much as 29.5 kg N ha–1 could be lost through leaching below the root zone of a maize crop, Over a 3 year period the applied nitrogen contributed to nitrate pollution of underground water significantly in excess of the maximum level accepted for potable water. This was particularly high in valley bottoms where the nitrate nitrogen content ranged from 12.8 to 24.6 mg L–1. Contribution to adjacent stream was, however, not significant. 相似文献
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提出了膨化硝铵炸药水分控制过程检测存在的问题,研究讨论了膨化硝铵炸药半成品和成品的水分检测方法,通过测定方法的改进,提高了检测效率和生产过程控制效果,解决了膨化硝铵炸药生产过程控制的一个难题. 相似文献
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从原材料水分、装药温度、半成品吸湿性与成品水分,在不同温度下的成品储存等方面,探讨2号岩石粉状铵梯油炸药结块硬化的原因。 相似文献
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三氨基硝酸胍的放大合成工艺及表征研究 总被引:3,自引:0,他引:3
介绍三氨基硝酸胍(TAGN)的多种化学合成方法,主要有双氰胺法、氰胺钙法、氰胺法、硝酸胍法;对硝酸胍法进行了优化改进,报道了硝酸胍一步法合成TAGN的公斤级放大合成工艺,可采用低浓度水合肼为原料,合成产率达94.8%,同时还提高了产物纯度;探讨了影响反应的多项因素;通过熔点测试、元素分析、红外光谱(IR)和X射线衍射(XRD)等对合成的TAON结构进行了表征和确认。 相似文献
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对烟浪丁片剂储存过程中的药物含量进行了追踪检测。结果表明,该制剂在存储过程发生了不同程度的分解,对存放 24 个月左右的药片,测定的标示含量仅是设计含量的一半。 相似文献
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