砖筒仓充二氧化碳安全储麦技术研究

二氧化碳被导入一管道系统并使其在砖筒仓的粮堆内逐渐均匀分布，直到其在粮堆中的浓度达70％以上，试验其间通过该管道系统进行二氧化碳环流，经过14天停止操作，仓内粮堆中二氧化碳气体浓度保持35％以上，该气控方法储存小麦可达保鲜、无虫霉损害，安全储粮目的。     

纳米二氧化硅/纳米纤维素复合材料制备及性能分析

使用造纸方法快速成功的制备了纳米纤维素,纳米二氧化硅复合材料,对并材料的力学性能,热性能和吸湿性能进行了分析。研究结果表明:随着纳米二氧化硅的添加量逐步提高,纳米复合材料的理论密度逐渐下降,材料的拉伸性能和模量值都有大幅度的下降。材料热解的初始降解温度和热解活化能随着纳米二氧化硅质量分数的增多提升,当纳米二氧化硅质量分数为20%时,材料初始热解温度为280℃。纳米复合材料的含水率随着吸湿时间的延长而增加,且随着纳米二氧化硅添加量的增多,材料的最终含水率不断提高,当纳米二氧化硅质量分数为20%时,纳米复合材料的最终含水率约26%,纳米复合材料的表面接触角值仅为40.4°。该研究结果可为制备了纳米纤维素/纳米二氧化硅复合材料提供参考。     

Effects of ambient air pollution on wheat and rice yield in Pakistan

Open-top chambers ventilated with ambient or chiarcoal-filtered air were used to assess the impact of air pollution on the yield of local cultivars of wheat and rice, at a site on the outskirts of Lahore. At this location, 6-h mean O₃ concentrations reach 60 ppb in certain months, and annual mean NO₂ concentrations are 20–25 ppb. The experiments showed significant yield reduction in two successive seasons which ranged from 33% to 46% in wheat and from 37% to 51% in rice. The major yield parameter affected was the number of ears or panicles per plant, although there was also evidence of small effects on 1000 grain weight and on the number of grains per ear/panicle. These results have significance in terms of the maintenance of agricultural yields as pollution emissions rise in south and south-east Asia.     

Organic chlorine and chloride in submerged paddy soil: a case study in Anhui province, southeast China

Abstract. Efforts to understand the fate of organochlorine compounds in arable soil have concentrated on anthropogenic compounds, in spite of the fact that organochlorine compounds are both produced and mineralized in soil through natural processes. In order to understand the fate of chlorinated pesticides, it is necessary to take account of the natural chlorine cycle. The present study is a first attempt to illuminate the relationship between the natural chlorine cycle and agricultural practices. The concentration and storage of organic chlorine (Cl_org) and chloride (Cl_inorg) were determined in topsoil of a paddy field compared to an adjacent afforested hill at a sampling site in the Meicun area, Anhui Province, China. The concentration of Cl_org, as well as the chlorine-to-carbon ratio, was significantly lower in the paddy field samples than in the forest soil samples. A weak relationship between the concentration of Cl_org and the organic carbon content was observed in the paddy field, in contrast to the observations made in the adjacent forest soil as well as those made in previous studies, which have suggested a positive correlation between organic carbon content and Cl_org. The similarity between our results at the forest site and the previous studies, which have been carried out in temperate regions, suggests that it is the land use rather than the climate that makes the current paddy soil results different. Our results suggest that the contribution of Cl_org to the paddy soil from above-ground litter and from production within the soil are small or negligible compared with the contribution from pesticide application and wet and dry deposition.     

基于EPANET的再生水滴灌系统余氯分布模型构建

加氯处理是保证滴灌系统安全的重要措施之一,但是氯与灌溉水及滴灌管壁发生反应而引起的衰减会对余氯分布均匀性造成不利影响。该研究采用EPANET软件构建了再生水滴灌系统水力性能及余氯运移、衰减和分布模型,基于试验数据对模型水力和水质模拟参数进行率定和验证,并应用该模型分析了加氯模式(浓度-时长:1.3mg/L-185min、3 mg/L-80 min、6 mg/L-40 min和8 mg/L-30 min)和毛管长度(10～150 m)对系统余氯分布特征的影响。结果表明,EPANET软件可以较好地模拟滴灌系统水力性能及余氯分布特征,沿毛管方向余氯浓度模拟值与实测值一致性指数达到0.75以上。当毛管长度由10 m增加至150 m时,灌水单元平均余氯浓度与毛管末端余氯浓度随毛管长度增加呈先升高而后降低趋势,高浓度加氯处理平均余氯浓度和毛管末端余氯浓度随毛管长度增加衰减速率相对较小。较短的加氯历时(40 min)和过低的加氯浓度(如1.3 mg/L)均易造成余氯质量偏差率升高和均匀系数降低;建议使用加氯浓度3 mg/L且加氯时长80 min的加氯模式,该模式毛管极限铺设长度达到66 m,余氯质量均匀系数超过90%。     

Long-term effect of chemical fertilizer,straw, and manure on labile organic matter fractions in a paddy soil

To assess the effect of long-term fertilization on labile organic matter fractions, we analyzed the C and N mineralization and C and N content in soil, particulate organic matter (POM), light fraction organic matter (LFOM), and microbial biomass. Results showed that fertilizer N decreased or did not affect the C and N amounts in soil fractions, except N mineralization and soil total N. The C and N amounts in soil and its fractions increased with the application of fertilizer PK and rice straw. Generally, there was no significant difference between fertilizer PK and rice straw. Furthermore, application of manure was most effective in maintaining soil organic matter and labile organic matter fractions. Soils treated with manure alone had the highest microbial biomass C and C and N mineralization. A significant correlation was observed between the C content and N content in soil, POM, LFOM, microbial biomass, or the readily mineralized organic matter. The amounts of POM–N, LFOM–N, POM–C, and LFOM–C closely correlated with soil organic C or total N content. Microbial biomass N was closely related to the amounts of POM–N, LFOM–N, POM–C, and LFOM–C, while microbial biomass C was closely related to the amounts of POM–N, POM–C, and soil total N. These results suggested that microbial biomass C and N closely correlated with POM rather than SOM. Carbon mineralization was closely related to the amounts of POM–N, POM–C, microbial biomass C, and soil organic C, but no significant correlation was detected between N mineralization with C or N amounts in soil and its fractions.     

Porous tubing for use in monitoring soil CO2 concentrations

The composition of the soil atmosphere is an indicator of biological processes, and soil CO₂ gradients have been used to estimate CO₂ efflux from the surface. Soil atmosphere samplers, constructed with gas-permeable materials, have been used to quantify soil CO₂ concentrations. The type of material used can influence the perceived real-time concentrations of CO₂ in the soil. Previous works have not directly compared different types of materials under the same conditions. The objective of this study was to determine the diffusion coefficient (D) and time of 95% equilibrium (t_eq) of CO₂ through several materials, and to evaluate the effect of long-term soil burial (183 days) on diffusion characteristics. Materials tested included silicone, expanded Teflon (ePTFE), and ultra high molecular weight polyethylene (PE) tubing. The D of each material was determined using a closed-loop system consisting of a CO₂-enriched (7800 ppm) chamber, a CO₂ analyzer and an inner tube (experimental tubing) placed inside the chamber. Air was re-circulated through the inner tube, and as CO₂ diffused from the chamber into the tubing, the analyzer recorded the increase in concentration. The silicone tubes had values of D ranging from 8.64 to 5.80×10⁻⁶ cm² s⁻¹ with corresponding t_eq between 3.9 and 9.7 h. Diffusion coefficients of the ePTFE (1.25×10⁻⁴ cm² s⁻¹) and PE (7.70×10⁻⁴ cm² s⁻¹) materials were 2 orders of magnitude greater, with t_eq<6 min. Exposure to the soil environment for 183 days did not visibly deteriorate the materials or significantly affect the D or t_eq values. Use of the ePTFE or PE materials, over the silicone materials, may allow for better characterization of dynamic CO₂ concentrations in the soil based on the greater D and lesser t_eq values of these materials.     

酸和氧化还原剂对二氧化锰溶解度的影响

由于土壤中锰的有效性随pH和Eh的变化而变化,利用土壤测试方法得到的锰素营养丰缺指标,通常难以代表田间锰素营养的实际状况.然而,在应用土壤pH和氧化锰溶解度的关系时,某些文献的不确切解释,引起一些误解.本实验研究了在浓HCl、HNO3和H2SO4及其稀溶液的不同浓度情况下对二氧化锰-水钠锰矿(MnO2)的溶解能力和机理,以及三种卤素还原剂(KCl、KBr和KI)在两种pH值条件下对MnO2的还原能力,从实验上和理论上进一步阐明了pH和Eh对MnO2溶解度的影响.实验结果表明,在浓HCl中,MnO2能被Cl-迅速还原而溶解.而在浓HNO3和H2SO4溶液中,MnO2不能被酸所直接溶解,只能被酸中的H2O缓慢还原,放置两年后反应仍未到达终点.在稀酸溶液中,当H+强度小于0.5 mol L-1(pH＞1.0)时,三种强酸对MnO2都无明显的溶解能力;当H+强度＞1.0 mol L-1时,HCl对MnO2的溶解能力显著地高于HNO3和H2SO4.三种卤盐溶液对MnO2的还原能力为KI＞KBr＞KCl,并随pH的降低和浓度的升高而增强.当pH＞3时,KCl对MnO2的还原能力极弱;而无论pH高低(pH3或pH5),KI在很低浓度(0.001 mol L-1)时都能有效地还原MnO2.上述结果说明,如果二氧化锰不被还原,仅改变pH则很难被溶解.然而,在较高pH条件下,如有强还原剂存在,也有相当量的MnO2被还原.低Eh和pH条件下最有利于MnO2的还原.     

实验条件下人工气候舱内的气体质量分析

为规范科研实验条件，更好地为现代畜牧业产业化服务，检验了农业部动物营养学重点开放实验室程控式人工气候舱（简称环控舱）的通风系统的功能，对装载动物的环控舱在正常运转５ｄ以上的气体成分进行分析。测定结果表明舱内的氨气和二氧化碳浓度分别为１１．３～１９．７ｍＬ／ｍ３和８９０～１４００ｍＬ／ｍ３，均低于家畜卫生标准，但鸡试验舱在上午开舱门清粪前的氨气浓度和猪试验舱的二氧化碳浓度较高，接近了卫生标准的上限值。