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71.
试验表明;组织未受损伤的新鲜蔬菜样品在20~30℃与4℃下可分别保存3天与7天其NO_3含量基本不变;捣碎的样品在4℃可保存4~6h;经100℃烘煮后,又在4℃处理可保存一夜;样品干燥后在干燥器中存放20天内含量不变,但受潮后极易变化。 相似文献
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74.
《Journal of Manufacturing Processes》2014,16(3):405-413
Significant amount of work is reported on development of vegetable oil based metalworking fluids (MWFs). Many also report on development and performance evaluation of vegetable based oils. For many of these water-based MWFs with vegetable oils, much effort is focused on stable emulsification of vegetable oil in water using a variety of surfactants. It has been found that surfactant-free stable emulsification of oil in water is possible through ultrasonic vibration. However, emulsification through ultrasonic atomization has not yet been considered, and the feasibility of emulsified metalworking fluids through ultrasonic atomization has not been investigated. In this paper, stable emulsification of vegetable oil in water has been achieved through ultrasonic atomization without using any surfactant. The emulsified vegetable oil in water is directly used to investigate its effectiveness as MWF in milling operations. Lower cutting forces, chip thickness, and burr amount are observed with vegetable oil-in-water emulsion compared to conventional MWF. The experimental results show strong potential for vegetable oil-in-water emulsion obtained through ultrasonic atomization as an effective MWF. 相似文献
75.
Ozone risk for crops and pastures in present and future climates 总被引:2,自引:0,他引:2
Jürg Fuhrer 《Die Naturwissenschaften》2009,96(2):173-194
Ozone is the most important regional-scale air pollutant causing risks for vegetation and human health in many parts of the
world. Ozone impacts on yield and quality of crops and pastures depend on precursor emissions, atmospheric transport and leaf
uptake and on the plant’s biochemical defence capacity, all of which are influenced by changing climatic conditions, increasing
atmospheric CO2 and altered emission patterns. In this article, recent findings about ozone effects under current conditions and trends in
regional ozone levels and in climatic factors affecting the plant’s sensitivity to ozone are reviewed in order to assess implications
of these developments for future regional ozone risks. Based on pessimistic IPCC emission scenarios for many cropland regions
elevated mean ozone levels in surface air are projected for 2050 and beyond as a result of both increasing emissions and positive
effects of climate change on ozone formation and higher cumulative ozone exposure during an extended growing season resulting
from increasing length and frequency of ozone episodes. At the same time, crop sensitivity may decline in areas where warming
is accompanied by drying, such as southern and central Europe, in contrast to areas at higher latitudes where rapid warming
is projected to occur in the absence of declining air and soil moisture. In regions with rapid industrialisation and population
growth and with little regulatory action, ozone risks are projected to increase most dramatically, thus causing negative impacts
major staple crops such as rice and wheat and, consequently, on food security. Crop improvement may be a way to increase crop
cross-tolerance to co-occurring stresses from heat, drought and ozone. However, the review reveals that besides uncertainties
in climate projections, parameters in models for ozone risk assessment are also uncertain and model improvements are necessary
to better define specific targets for crop improvements, to identify regions most at risk from ozone in a future climate and
to set robust effect-based ozone standards. 相似文献
76.
77.
Effect of liming on sulfate transformation and sulfur gas emissions in degraded vegetable soil treated by reductive soil disinfestation 总被引:1,自引:0,他引:1
Reductive soil disinfestation (RSD), namely amending organic materials and mulching or flooding to create strong reductive status, has been widely applied to improve degraded soils. However, there is little information available about sulfate (SO42 −) transformation and sulfur (S) gas emissions during RSD treatment to degraded vegetable soils, in which S is generally accumulated. To investigate the effects of liming on SO42 − transformation and S gas emissions, two SO42 −-accumulated vegetable soils (denoted as S1 and S2) were treated by RSD, and RSD plus lime, denoted as RSD0 and RSD1, respectively. The results showed that RSD0 treatment reduced soil SO42 − by 51% and 61% in S1 and S2, respectively. The disappeared SO42 − was mainly transformed into the undissolved form. During RSD treatment, hydrogen sulfide (H2S), carbonyl sulfide (COS), and dimethyl sulfide (DMS) were detected, but the total S gas emission accounted for < 0.006% of total S in both soils. Compared to RSD0, lime addition stimulated the conversion of SO42 − into undissolved form, reduced soil SO42 − by 81% in S1 and 84% in S2 and reduced total S gas emissions by 32% in S1 and 57% in S2, respectively. In addition to H2S, COS and DMS, the emissions of carbon disulfide, methyl mercaptan, and dimethyl disulfide were also detected in RSD1 treatment. The results indicated that RSD was an effective method to remove SO42 −, liming stimulates the conversion of dissolved SO42 − into undissolved form, probably due to the precipitation with calcium. 相似文献
78.
加强肥料规范化管理控制蔬菜重金属污染 总被引:11,自引:1,他引:11
总结了中国各主要城市郊区的蔬菜重金属的污染情况,从各种调查结果看出,中国蔬菜的重金属含量总体上还处在安全食用范围内,但在城郊结合部,蔬菜中重金属的污染比较严重。肥料是重金属污染的重要来源之一,从肥料的生产和管理的角度提出了控制肥料重金属含量的方法.为蔬菜食用的安全性提供保障。 相似文献
79.
酶抑制法检测蔬菜中的有机磷农药 总被引:6,自引:0,他引:6
对新型酶抑制检测蔬菜中有机磷农药残留量的方法进行了研究,介绍了胆碱酯酶的提取、纯化方法,以及用粗酶和纯酶检测蔬菜中有机磷农药残留量的测定效果,确定了最佳实验条件。对样品的预处理方法进行了改进,得出该法的检测限为1mg/L,对甲基对硫磷等几种常用农药的加标回收率为90.4%~112%,相对标准偏差为1.06%~9.83%,表明三项评价指标均符合全国农药残留科研协作组对农药残留分析方法的基本要求。 相似文献
80.
离子色谱法测定蔬菜中硝酸盐含量方法初探 总被引:1,自引:0,他引:1
蔬菜作为人们日常生活中必需的鲜活农产品,其食用的安全性日益引起重视。食品中的亚硝胺是大家公认的一种化学致癌物,其前体包括硝酸盐和亚硝酸盐。由于化肥的广泛使用,尤其是化学氮肥,使蔬菜中硝酸盐含量过大。分析蔬菜中硝酸盐含量也可以间接了解农田土壤的环境质量。文章阐述了离子色谱法测定蔬菜(如小白菜、葱、韭菜、莴笋叶及苋菜等)中硝酸盐含量的前处理方法与测定步骤。它可以作为测定蔬菜、水果等食品中硝酸盐含量的一种精密度高、简单快速的方法。 相似文献