基于Fortran程序对储粮通风温度水分和害虫演替的模拟研究

世界各国因储粮害虫对粮食造成的损失非常严重,为了降低粮食在储藏期间的损耗,所以研究储粮通风过程中害虫增长量的变化至为重要。文章基于多孔介质热湿耦合理论,建立了浅圆仓的粮堆内部热湿传递和流动的数学模型以及害虫和熏蒸经验模型,并基于Fortran语言编程,模拟分析了通风状态下粮堆温度、水分含量、储粮害虫增长量以及杀虫剂浓度衰减的变化。结果表明：通风对粮堆内部温度和水分以及害虫生长影响明显。粮堆的水分含量近似对称分布,而受太阳辐射的影响,粮仓不同方向壁面的温度分布并不对称。储粮害虫在粮仓内的数量分布与温度、水分等因素有关,在壁面附近害虫分布较多,且在筒仓中心区域出现分层现象。杀虫剂浓度衰减也受温度的影响,温度高会影响杀虫剂的降解,导致杀虫剂浓度较低     

Effect of grain storage and processing on chlorpyrifos-methyl and pirimiphos-methyl residues in post-harvest-treated wheat with regard to baby food safety requirements

A study was undertaken to assess the effects of storage intervals and of milling procedures on the dissipation of chlorpyrifos-methyl and pirimiphos-methyl residues in post-harvest-treated wheat grain and to obtain scientific data on the compliance of the processed products with safety requirements concerning baby foods. The insecticide formulations were applied on stored wheat at recommended rates (20 ml t^-1). The initial concentration levels in whole grain were determined in samples taken 1 h after treatment. The dissipation of residues and their distribution in different fractions of the milled grain were studied after various storage intervals, from 7 to 270 days after treatment. Samples of treated grain were milled in a fractionating laboratory mill and eight fractions — bran, semolina, three types of groats and three types of flour — were collected and analysed for pesticide residues. The residues were determined by an analytical method based on acetone extraction, graphitized carbon clean-up and GC-ECD, respectively, and GC-NPD determination of residues. The limits of determination of both pesticides were 0.005 mg kg^-1, which is high enough for enforcement of the European Commission Directive that established a maximum residue level of 0.01 mg kg^-1 for any pesticide in cereal-based baby food. The results showed that the pesticides chlorpyrifos-methyl and pirimiphos-methyl applied post-harvest on wheat as grain protectants were distinguished by relatively low rates of degradation in the grain under practical storage conditions. Milling did not significantly reduce the bulk of the chemicals but resulted in the distribution of residues in various processed products. The main part of the insecticides deposited on the grain remained in the bran and partly in semolina fractions. After 270 days of treatment, the residues of chlorpyrifos-methyl were within the range 0.8-2.1 mg kg^-1 and of pirimiphos-methyl — between 0.6 and 3.7 mg kg^-1 in the various types of flour.     

储粮环境中米象发生与CO2含量变化的关系研究

为阐明储粮环境中害虫发生与CO_2气体含量变化的关系,研究不同含水量的小麦感染不同虫口密度(0、2、5、10、20、30头/kg)米象后储藏环境中CO_2气体体积分数变化的情况。结果表明:对于含水量相同的储藏小麦,储藏环境中CO_2气体体积分数随虫口密度的增加和储藏时间的延长而显著增加。对于含水量12%的小麦,初始感染虫口密度为30头/kg的储粮环境中CO_2气体体积分数最初为0.413%,在第30天达到最大值为14.777%。对于含水量14%的小麦,初始感染虫口密度为30头/kg的储粮环境中CO_2气体体积分数最初为0.720%,在第15天达到最大值为17.197%。本研究结果为今后通过检测CO_2体积分数变化来监测粮堆中虫害发生情况提供了可靠信息。     

储粮生态系统热湿调控机理及在就仓机械通风中的应用

本研究基于多孔介质热质传递原理和粮粒吸湿/解吸湿理论,建立了通风过程中粮堆内部热湿耦合传递方程,并采用数量级分析的方法,获得了储粮通风过程中温度和水分时间变化率的关联式。依据所建立的方程和关联式,探究了储粮生态系统热湿调控机理,分析和讨论了温度差、湿度差、单位通风量和通风方向对储粮通风过程中粮温和水分的影响。提出了就仓降水通风、降温保水通风和调质通风的操作原则和策略。研究结果可以为我国的储粮生态系统热湿调控理论的建立和粮库智能化管理系统的建设提供借鉴。对于完善我国储粮就仓机械通风技术,避免无效和有害通风,实现精准通风,具有一定的指导意义。     

Literature review: Impact of climate change on pesticide use

Agricultural yields strongly depend on crop protection measures. The main purpose of pesticide use is to increase food security, with a secondary goal being increased standard of living. In view of a changing climate, not only crop yields but also pesticide use is expected to be affected. Therefore, an analysis of the detailed effect of changing climatic variables on pesticide use is conducted. Not only effects on cultivated crops, occurring pests and pesticide efficiency are considered but also implications for technological development, regulations and the economic situation are included as all of these aspects can influence pesticide use. The objective of this review is to gain insights into the specific effect of climate change on the consumer exposure caused by pesticide residues on crops. In terms of climate change, temperature increase and changes in precipitation patterns are the main pest and pathogen infection determinants. An increased pesticide use is expected in form of higher amounts, doses, frequencies and different varieties or types of products applied. Climate change will reduce environmental concentrations of pesticides due to a combination of increased volatilization and accelerated degradation, both strongly affected by a high moisture content, elevated temperatures and direct exposure to sunlight. Pesticide dissipation seems also to be benefitted by higher amounts of precipitation. To overcome this, pesticide use might be changed. An adapted pesticide use will finally impact consumer exposure at the end of the food chain.     

Safe storage guidelines for durum wheat

Storage conditions determine the safe storage period for any grain. Safe storage guidelines for durum wheat have not been developed, despite the fact that it is more susceptible to spoilage than other wheat classes. The rates of deterioration of durum wheat samples with 15, 16, 17, 18, 19 and 20% initial moisture content (wet basis) stored at 10, 20, 30 and 40 °C for 12 wk were studied. The grain deterioration parameters including seed germination, moisture content, appearance of visible mould, invisible microflora, free fatty acid value (FAV), and ochratoxin production were monitored at regular intervals. From these results, safe storage guidelines for durum wheat were developed with respect to the moisture content and storage temperature. Germination rates of the samples decreased with an increase in moisture content, temperature and storage period. Visible mould was found in all high moisture samples (17, 18, 19 and 20%) stored at high temperatures. FAV of the samples increased with moisture content and storage time.     

小麦储藏水分、温度和真菌生长危害进程预测的研究

对小麦储藏水分、温度、真菌最初生长时间和危害进程进行了初步探索性研究。采用喷雾着水方法将样品水分调至13.2%、13.6%、14.0%、14.5%、15.1%、15.5%、16.9%,分别于10、15、20、25、30、35℃恒温箱模拟储藏,定期检测各样品真菌生长变化情况,周期为120 d。结果表明,小麦在不同温度储藏,随着温度增加,真菌生长速度加快,30℃时达到最高,35℃时生长速度降低。在6个试验温度中,从安全和经济角度评价,最佳储藏温度为20℃;16.9%水分的小麦,由于出现一些青霉生长,即使低温储藏,这个水分仍存在着较大风险;根据上述研究结果,研究首次提出了小麦储藏水分、温度和真菌最初生长关系曲线,小麦在不同温度下储藏,真菌危害进程所需的时间。由于储粮真菌生长影响因素的复杂性,本试验数据仅供参考。     

Quantifying the effect of soil moisture on the aerobic microbial mineralization of selected pesticides in different soils

A standardized quantitative approach was developed to reliably elucidate the effect of increasing soil moisture on pesticide mineralization. The mineralization of three aerobically degradable and chemically different 14C-labeled pesticides (isoproturon, benazolin-ethyl, and glyphosate) was studied under controlled conditions in the laboratory at an identical soil density of 1.3 g cm(-3). The agricultural soils used are characterized by (i) large variations in soil texture (sand content 4-88%) and organic matter content (0.97-2.70% org. C), (ii) fairly diverse soil-water retention curves, and (iii) differing pH values. We quantified the effect of soil moisture on mineralization of pesticides and found that (i) at soil water potential < or = -20 MPa minimal pesticide mineralization occurred; (ii) a linear correlation (P < 0.0001) exists between increasing soil moisture (within a soil water potential range of -20 and -0.015 MPa), and increased relative pesticide mineralization; (iii) optimum pesticide mineralization was obtained at a soil water potential of -0.015 MPa, and (iv) when soil moisture approximated water holding capacity, pesticide mineralization was considerably reduced. As both selected pesticides and soils varied to a large degree, we propose that the correlation observed in this study may be also valid in the case of aerobic degradation of other native and artificial organic compounds in soils.     

Effects of Storage Conditions on the Total Aerobic and Yeast/Mold Bacterial Counts of Rough Rice During On-farm Storage

ABSTRACT: Total aerobic plate counts (APC) and yeast/mold counts on farm-stored rice ( Oryza sativa L.) were evaluated as a function of sampling position within a bin, storage treatment (aeration technique), and storage duration. Rough rice (cv. Cypress) was stored for 15 wk and sampled at time 0 and at 4-wk intervals thereafter. No significant differences were found for either APC or yeast/mold counts between sample locations within a bin. The APC were significantly lower in all bins after 15 wk (p < 0.05) by 1.5 log cfu/g, corresponding to the temperature decrease of the rice in the storage bins. Yeast/mold data varied significantly over storage duration in a pattern similar to the moisture content data. Aeration treatment did not affect yeast/mold counts, but APC were significantly lower at 15 wk for rice from controlled aeration. Results indicate that storage efforts aimed at reducing grain temperature can reduce microbial loads.     

A possible rapid method of determining the moisture content of high-moisture grain

A linear relationship was shown to exist between the moisture content of barley and of tick beans and the temperature rise obtained when a quantity of concentrated sulphuric acid was added to the grain. This relationship can be used to determine the moisture content of grain, particularly at the higher moisture levels which are often outside the upper limit of many existing rapid methods of moisture measurement. The ‘acid’ method is reasonably rapid, taking about 15 minutes, and gives a reproducibility of approximately 1.0% moisture content. If the initial temperature of the grain differs widely from the calibration temperature, a temperature correction must be applied.     

生物农药多杀菌素及其结构类似物的研究进展

在日益重视环保的今天，生物农药因其易降解、低残留、低污染、高安全性以及病虫害不易产生抗性等优点已成为世界各国农药学家研究的热点，将引领农药开发新趋势。多杀菌素及其结构类似物作为新型绿色生物农药，其特殊的化学结构决定了独特的作用机理，同时具有生物农药的安全性和化学农药的速效性。在防治农林害虫、储粮害虫、卫生害虫以及牲畜寄生虫上发挥重要作用。通过比较多杀菌素及其结构类似物的理化特性，总结其理化诱变、分子改造、产品研发与应用以及抗性研究等方面的进展，分析生物农药推广的现状和存在问题，提出解决思路，并对其发展前景进行展望。     

Stability of organophosphate and pyrethroid pesticides on wheat in storage

The pesticides chlorpyriphos-methyl, pirimiphos-methyl and permethrin were applied to wheat and stored for 52 weeks at 25, 30, 35 and 40 degrees C, and at 10 and 13% m.c. Rates of loss were calculated from the residue analyses of pesticides in treated wheat at monthly intervals during the storage period. Calculated half-lives and pseudo first-order rate constants of these pesticides are discussed with reference to temperature and moisture.     

Statistical analysis of decay of organophosphorus and pyrethroid insecticides and carbaryl on paddy rice, maize, sunflowers and field peas

A model is developed to describe the decay of seven insecticides on stored paddy rice, maize, sunflowers and peas, and is shown to be more precise than each of six literature models on pesticide decay. It relates residues (R), as a ratio of applied concentration (R(0)), to time after insecticide application (t), modifying the usual first-order kinetics equation lnR=lnR(0)-kt by assuming that the rate constant k has a mixture of values according to a gamma distribution with mean K. The resulting equation is lnR=lnR(0)-Kcln(1+t/c), where c is a constant determined empirically. For large c, this model reduces to the first-order model with K=k. The parameter K is further modelled as linear in temperature for maize and rice. The rate of loss of protectants was found not to be seriously affected by co-application with other insecticides, and this is a useful finding for future studies on rates of loss of grain protectants. The apparent rate of loss was also not seriously affected by the method of analysis, whether by gas chromatography or high-performance liquid chromatography, and this finding supports previous validation of the methods.     

基于数值预测的稻谷横向降温保水通风最佳湿度研究

本实验基于多孔介质热湿传递原理和粮粒吸湿/解吸湿理论,建立了通风过程中粮堆内部热湿耦合传递方程,采用数值预测的方法,研究了吨粮通风量不变、粮堆初始温度与通风空气温度差8℃情况下,粮堆初始平衡湿度与通风空气湿度差分别为-5%、0%和5%时,粮堆内部温度和水分随时间的变化规律。探究了通风湿度对稻谷横向保水降温通风过程中粮堆温度和水分的影响,分析了一定初始粮温和水分时通风空气温湿度对降温保水的效果,得到了稻谷横向降温保水通风的最佳湿度。研究结果可以丰富和完善横向降温保水通风工艺,同时也为横向降温保水通风的操作提供依据。     

大跨度平房仓上下行降温通风的数值模拟研究

基于多孔介质流动和传热传质理论,建立了仓储储粮通风过程中粮堆内部流动及热湿耦合传递的数学模型。采用计算流体动力学的方法,预测分析了双侧通风的大跨度平房仓在不同粮堆温度梯度方向、不同竖向通风方式的4种工况下粮堆内部温度和水分变化规律。同时探究了吊顶粮仓与未吊顶粮仓在4种通风工况下的降温保水效果。结果表明：粮仓未吊顶时,上行通风方式的降温保水效果优于下行通风;对于吊顶粮仓,上行通风与下行通风降温保水效果相差不大;粮面顶部的空气区域对降温通风时粮堆的温度变化、水分变化影响较大,对粮仓进行吊顶,具有更好的降温保水效果。     

储粮横向通风多尺度热湿耦合传递研究

温湿度是影响粮食安全储存的重要因素,为保证储粮安全,采用机械通风,使粮堆和粮粒的温度和水分含量可以得到有效控制。该文基于多孔介质的传热传质理论,建立了仓储稻谷通风过程中粮堆内部流动和热湿耦合传递的数学模型以及粮粒的热量传递和水分输运模型。采用计算流体力学的方法,从粮堆尺度和粮粒尺度,分析了机械通风过程中仓储粮堆和粮粒内部的温度、水分分布规律。研究发现,通风过程阶段,粮堆内部温度降温显著,粮堆整体平均水分呈降低趋势,且粮堆内部温湿度受外界环境温湿度的影响很大;研究还发现粮粒水分扩散速度远小于温度扩散速度。研究结果可以为储粮横向通风保水降温的工作以及粮堆局部霉变、发热和害虫的发育的预防提供参考。     

A comparison of the functional characteristics of wheat stored as grain with wheat stored in spike form

In this study, wheat grain and wheat spike with 12%, 14% and 16% moisture content were stored at 10, 20 and 30 °C for 0, 3, 6 and 9 months. After storage, wheat samples were investigated for hectolitre weight, gluten content, Zeleny sedimentation volume, enzyme activity, acidity, phytic acid and L colour value. Storage of wheat at different storage forms (spike and grain) and storage conditions showed considerable changes in grain quality. In general, the storage period of 3 months positively affected wheat quality. However, hectolitre weight, gluten, Zeleny sedimentation, enzyme activity, acidity and colour of wheat got worse at storage periods beyond 3 months. Hectolitre weight, wet and dry gluten, Zeleny sedimentation, phytic acid content and L Colour value of wheat stored in both spike and grain form significantly decreased during storage. However, the increase in grain moisture content, storage time and temperature resulted in significant increase in total titratable acidity and falling number values of wheat. Falling Number and phytic acid values of wheat stored in spike form were generally lower than wheat stored in grain form. Storage in spike form had a positive effect on especially wet gluten content of wheat stored at non-optimal storage conditions such as high grain moisture content and high temperature. Wet gluten of wheat stored in spike form was higher than that of wheat stored grain form after storage at 30 °C for 6 and 9 months. Wheat stored in spike form is more resistant than wheat stored in grain form against adverse storage conditions such as high moisture content and temperature and longer storage time.     

双扩散传热传质模型及在横向谷冷通风中应用

本文首先建立了单颗粒小麦内部水分迁移模型,基于有限元的方法数值模拟了颗粒内部水分变化规律,通过回归数值模拟数据,得到了颗粒平均水分模型和平均水分变化的干燥(或吸湿)速率模型。在此基础上推导出了谷物颗粒堆积床双扩散传热传质模型,并采用有限元的方法数值模拟分析了就仓横向(水平)谷冷通风时仓储粮堆内部热湿耦合传递规律。通过比较数值模拟和实验测定数据,验证了所建立的模型的合理性。分析了横向谷冷通风时粮粒温度和水分以及粮粒周围空气温度的变化规律,探讨了横向谷冷通风时粮堆内部降温效果。     

Modelling biological efficacy decrease and rate of degradation of chlorpyrifos-methyl on wheat stored under controlled conditions

Insecticide residue degradation and pest survival were observed in wheat treated with a low dose of chlorpyrifos-methyl. Treated wheat was stored in small batches at three controlled temperatures and two levels of moisture content of grain, in equilibrium with r.h. in order to stabilise the water activity in the grain during a storage period of 126 d after insecticide application. Every 3 weeks, samples were taken from treated and untreated control grain in each storage condition. Chlorpyrifos-methyl residues declined regularly with time of storage and an exponential negative regression was fitted with high correlation coefficients in most situations of storage temperature and grain water activity (Aw). A multivariate model to show the respective influence of controlled variables involved in the model of residues breakdown (time, Aw, and temperature) was built up through a multiple regression. This model showed the respective importance of the water activity of grain kernels, temperature and formulation of chlorpyrifos-methyl and their combinations on the decline of residues. Simultaneously, the effectiveness of the residues was checked through bioassays with two target species: Sitophilus oryzae and Tribolium castaneum. Taking into account the intentionally low initial applied dose of chlorpyrifos-methyl, the period after application achieving complete kill of the two test insects was rather short and did not exceed 105 d for S. oryzae in the best conditions for control, i.e. low moisture content and temperature. For high Aw (0.8) and storage temperature 30°C, T. castaneum was effectively controlled (more than 95% kill) only on the day after the treatment, survival occurring at the next test date 21 d after the application. High moisture content and temperature and their interactions were the main variables influencing the decrease in the biological effectiveness with time. The concentration threshold for insect survival was slightly below 1 ppm chlorpyrifos-methyl and was influenced by storage and grain conditions. Implications of these findings on storage pest management practices and on the ability to predict the period of biological effectiveness of residues of chlorpyrifos-methyl are discussed.     

冷藏与家庭处理对黄瓜中7 种农药残留的影响

通过对黄瓜中7 种农药及2 种代谢物的残留量来评价冷藏与清洗、烹饪处理对农药及其代谢产物的影响。结果表明,在5 ℃贮藏条件下,黄瓜中的农药残留量随着冷藏时间的延长越来越低,10 d后黄瓜中的7 种农药降解率达38.9%～58.3%;清水清洗后7 种农药降解率在27.17%～80.00%之间,而清洁剂清洗的降解率可达33.33%～90.00%,2 种清洗方式所产生的农药降解率的差异与农药的水中溶解度相关;蒸、煮、炒3 种处理均能有效降低黄瓜中的农药残留量,煮处理对黄瓜中的农药消除效果最好,降解率在22.76%～85.00%之间,炒处理次之,降解率在21.52%～75.00%之间,蒸处理最差,在10.13%～53.25%之间。在烹饪处理过程中,烹饪所产生的温度为农药降解的关键因素。