改性玉米秸秆吸附Cu^2＋的动力学和热力学

本研究用ZnCl2作为活化剂,使用功率640W的微波照射4min的方法制备改性玉米秸秆。考察投加量、pH、吸附时间对吸附性能的影响,并对等温吸附特征、吸附动力学和热力学进行了系统研究。结果表明：投加量为0．2g,pH为6,改性玉米秸秆对Cu^2＋具有很好的吸附效果,吸附在8h后达到平衡。该吸附过程符合Langmuir及Freundlich等温吸附模型和准二级动力学方程,其反应的吉布斯自由能△G〈0,为自发反应过程。     

玉米秸秆碳源释放特征及反硝化效果

通过静态和动态实验研究了玉米秸秆的碳源释放规律,并考察其浸出液作为反硝化碳源对高、中、低硝酸盐氮的去除效果。实验结果表明,玉米秸秆可有效地释放碳源物质,静态实验中,固液比为1∶30时单位质量碳源释放的COD最多达254 mg/g,释放速率最快为13.37 mg/(g·d);动态实验中,秸秆长度为3 cm、水力停留时间(HRT)为48 h时,单位质量碳源释放的COD最多达826.26 mg/g,COD的速率最快为26.65 mg/(g·d)。反硝化过程中p H变化不明显,在7.0~8.0范围之间浮动。以玉米秸秆浸出液为反硝化碳源对中、低浓度的硝酸盐氮具有较好的去除效果,去除率保持在80%以上,甚至高达94%,但对高浓度的硝酸盐氮去除率仅在60%~80%之间。研究表明,玉米秸秆有较强的持续供碳能力,是一种经济合适的碳源材料,采用玉米秸秆浸出液作为去除地下水中硝酸盐氮的生物反硝化碳源是可行的。     

生物质炭对溶液中Cd~(2+)的吸附

以玉米秸秆、稻壳在350~500℃制成的生物质炭作为吸附剂,研究其对溶液中Cd2+的吸附特性。通过模拟实验,考察了初始p H、生物质炭用量、吸附时间和Cd2+的起始浓度对吸附的影响。结果表明,2种生物质炭对Cd2+的吸附反应适应p H范围较宽(4.0~7.0);玉米秸秆炭和稻壳炭对Cd2+的吸附速度较快,分别在10和20 min时达到吸附平衡;玉米秸秆炭对溶液中Cd2+的吸附遵循Langmuir等温线模型,而稻壳炭对Cd2+的吸附遵循Freundlich等温线模型。在实验设定的条件下,玉米秸秆炭对溶液中Cd2+的吸附能力强于稻壳炭。     

基于氢氧稳定同位素的华北农田夏玉米耗水规律研究

农作物耗水规律的研究对提高农业用水效率,缓解我国华北地区的水资源短缺现状具有重要意义。论文基于水文监测与氢氧稳定同位素方法,以山西省运城市董村农场为例,研究了夏玉米在不同生长期的根系吸水深度变化,以及农田灌溉条件下SPAC系统的水分通量。研究结果表明,夏玉米拔节期、开花期和成熟期的主要根系吸水深度分别为0~20 cm(96%~99%)、20~50 cm(58%~85%)、0~20 cm(69%~76%),在整个生长期内存在着先由浅变深,后由深变浅的规律;夏玉米漫灌后,蒸腾量占蒸散发量的71.3%,深层入渗损失量占到灌溉水量的43.3%,灌溉水的利用率仅为40.4%,应采取措施减小深层入渗量以提高灌溉水利用率。     

改性玉米秸秆对水溶液中硝酸根的吸附动力学研究

为了将玉米秸秆资源化,成为一种能够有效去除水及废水中硝酸根的吸附剂,将玉米秸秆进行化学改性制备了阴离子交换剂.重点研究了改性玉米秸秆对硝酸根的吸附热力学及动力学特性.结果表明,改性玉米秸秆对硝酸根的吸附均符合Langmuir等温模式和Freundlich等温模式.在20℃和40℃条件下的最大吸附量分别为80.8407 mg·g-1和72.7273 mg·g-1.吸附过程放热,降低温度有利于吸附的进行.改性玉米秸秆对硝酸根的吸附为快速吸附过程,30min内即可达到吸附平衡.改性玉米秸秆对不同初始浓度硝酸根的吸附过程均为一级反应,吸附过程受液膜扩散和颗粒内扩散同时控制.研究结果表明,改性玉米秸秆是一种良好的硝酸根吸附剂.     

渔塘坝微地域中玉米硒的分布及其与土壤硒的关系

在渔塘坝０．０１ｋｍ＾２的微域内,玉米硒含量达到较高水平,其根,茎,叶,籽中的平均硒含量分别是４．３６±３．２７ｍｇ／ｋｇ,３．０８±２．２４ｍｇ／ｋｇ,９．７４±７．６２ｍｇ／ｋｇ和８．０７±５．０２ｍｇ／ｋｇ。渔塘坝中玉米硒分布类似土壤分布,也可分出相对低,中、高硒的分布区。     

黄淮平原不同多熟模式生产力特征与资源利用效率研究

对黄淮平原一麦三玉米、一麦二玉米和一麦一玉米三种多熟模式的产量、资源利用及经济效益状况进行了比较分析。结果表明，三种模式年亩产均超过吨粮，说明在集约栽培条件下黄淮平原亩产吨粮的现实性。三种模式产量梯度差异表明，在水肥供应基本充足的情况下，通过集约多熟种植并配合以合理调控技术是在高产基础上进一步提高产量的有效途径。一麦三玉米最高产量达２２０１ｔ／ｈm₂（亩产１４６７ｋｇ），是在现有技术条件下接近与突破亩产吨半粮的有效种植模式之一。全年玉米总穗数增加是增产的关键。一麦三玉米模式通过接茬移栽等综合措施的有效配合，能维持较高的同化功能，光热资源利用效率提高。经济效益上表现为高投入高产出，但部分产投经济指标有下降的趋势。从综合考虑公顷产量与公顷纯收入及物质费用、用工等因素上综合评判，一麦三玉米模式总体上表现优势。     

保氮增效剂调节氮肥施用量和利用率研究——Ⅰ.保氮增效剂在玉米生产中的应用效果

田间试验和示范表明,在玉米作物生产中施用兼具多元素复合和氮肥加价作用的保氮增效剂,可显著地改善植株性状,促果穗增长增粗,使秃尖率下降、穗粒数和百粒重增加。保氮增效剂用量为玉米施氮肥量的2.92%～4.99%,玉米增产51.5～68.4kg/亩。肥料报酬提高2.2～2.6倍,增收经济效益达34.1～44.7元/亩。     

试论黄淮海地区的自然资源及国家级作物商品基地的建设

根据中国主要农业区——黄淮海地区的自然和社会经济条件,分析了该区小麦、玉米、大豆、棉花等在气候-土壤生态适应性的基础上,采用逐级生产力估算方法,计算出四大作物的商品量,论证了该地区建设为全国性四大作物商品基地的可能性。     

Consumer response to integrated pest management and certification

This study investigated consumer awareness of integrated pest management (IPM) and the effects of two marketing strategies. Specific objectives were to find whether eastern Massachusetts farmstand and farmers' market customers purchasing sweet corn care how their food is grown, whether they are aware of IPM, whether they would prefer to buy IPM-certified sweet corn and why, and whether the marketing methods presently available to IPM-certified growers can enhance awareness of IPM. In 1993, the Massachusetts Department of Food and Agriculture in collaboration with the IPM Program at the University of Massachusetts began a pilot IPM certification program for sweet corn and strawberries, designated ‘Partners with Nature’ (PWN). This study compared a ‘passive’ and ‘active’ PWN marketing strategy with a control that did not have any PWN publicity. The passive strategy was simply display of a PWN certificate and poster. The active strategy also included newspaper advertisements, clear labeling of corn as IPM-certified at the point of selection, a PWN sticker placed on bags of corn at payment, personally thanking customers for ‘buying our IPM-certified sweet corn’, and IPM brochures available to customers. Thirty purchasers of IPM-grown corn were interviewed at each of six farmstands and six farmers' markets.The dominant reason why customers patronize farmstands and farmers' markets was convenience. As found by other northeastern surveys, awareness of IPM was low: only 19% had heard of IPM before the survey, and only 38% of these could mention a specific method used in IPM. Although 45% of the respondents initially said that they did not care how their food is grown, 85% said that they would prefer to buy IPM-certified sweet corn after hearing a short definition. The definition gave only environmental benefits, but 74% of the customers preferring IPM-certified corn said they would buy it because it is safer or healthier. Most of the respondents claimed that they would be willing to pay 10% more for IPM-certified corn. Simply displaying an IPM poster had no significant results on consumer preference for IPM-grown produce, but active marketing significantly raised awareness of IPM and the PWN program.This study demonstrated the willingness of customers to support IPM because they believe it will have positive consequences for human health and environmental quality. It is concluded that sweet corn marketing based on IPM certification positively influenced consumer reactions to IPM; and a more extensive, diverse marketing strategy would enhance consumer awareness and support.