以玉米秸秆为底物的纤维素降解菌与产电菌联合产电的可行性

利用单室空气阴极微生物燃料电池（MFC）反应器,以玉米秸秆为底物,以本实验室筛选和保存的纤维素降解菌Chaetomium sp.和Bacillus sp.,以及纤维素降解混合菌PCS-S和H-C为秸秆降解的生物催化剂,探讨了以汽爆秸秆固体为底物进行微生物产电的可行性.结果表明,在MFC系统内,纤维素降解纯菌和混合菌均能使纤维素降解,但产生的电压很低（<90mV,1000Ω）,升高温度（30～38.5℃）对电压输出无明显影响.单独以生活污水作为菌源不能直接降解秸秆产电.只有将H-C和生活污水（产电菌源）混合作为接种体,MFC才能获得较高的电压输出.此时得到的以汽爆秸秆固体作为底物时的最大功率密度为406mW·m-2,仅比葡萄糖作为底物时所得到的最大功率密度510 mW·m-2低20%.     

微波辅助酸预处理玉米秸秆水解条件研究

玉米秸秆由叶子、皮和髓组成, 这些组分含有不同的纤维素、半纤维素和木质素, 因而可以成为生产燃料乙醇的原料. 采用微波辅助的酸水解来脱除与纤维素和木质素紧密结合的半纤维素, 使得纤维素结构发生变化有利于后续酶解是值得探讨的. 本研究通过将玉米秸秆叶子、皮和髓分离, 分别对它们进行了微波(2450MHz, 1000W)酸预处理, 确定了玉米秸秆不同部分的最优水解条件, 并对其进行了生产燃料乙醇的潜力对比, 以选出最适合做燃料酒精原料的部分. 同时, 在实验中, 选取硫酸浓度、温度、处理时间、料水质量体积比及搅拌速度5个因素分别进行单因素试验和正交试验. 结果表明, 5个因素对微波酸预处理玉米秸秆叶子的影响顺序依次为: 硫酸浓度>温度>料水质量体积比>时间>搅拌速度, 最佳条件是硫酸浓度5.0%, 温度75 ℃, 时间30min, 料水质量体积比1∶15, 搅拌速度800 r·min-1; 对玉米秸秆髓的影响顺序依次为: 硫酸浓度>搅拌速度>预处理时间>料水质量体积比>预处理温度, 最佳条件是硫酸浓度4.0%, 温度75 ℃, 时间25min, 料水质量体积比1∶20, 搅拌速度1000 r·min-1; 对玉米秸秆皮的影响顺序依次为: 硫酸浓度>预处理时间>料水质量体积比>预处理温度>搅拌速度, 最佳条件是硫酸浓度9.0%, 温度72 ℃, 时间30min, 料水质量体积比1∶17.1, 搅拌速度2000 r·min-1. 通过实验可以进一步得出, 玉米秸秆叶子和髓更适合用于生产燃料乙醇. 该研究结果对玉米秸秆的燃料化利用有一定的指导意义.     

改性玉米秸秆材料的制备及吸油性能的研究

以粉末状玉米秸秆(Raw corn stalks,RCS)为基体,甲基丙烯酸丁酯和苯乙烯为单体,采用悬浮聚合法制备高吸油复合材料(Butylmethacrylate and styrene grafted corn stalks,BMS-CS).实验确定的最佳制备条件为:在50℃,引发剂硝酸铈铵为2.0mmol·L-1,单体甲基丙烯酸丁酯和苯乙烯浓度分别为0.6mol·L-1、0.012mol·L-1,交联剂N,N’-亚甲基双丙烯酰胺质量分数为0.1%(相对于RCS的质量)的前提下反应25h.同时,实验考察了吸附时间、吸附温度及保油时间等对材料吸油性能的影响,并通过傅里叶变换红外光谱仪、X-射线衍射和扫描电镜对改性前后样品的结构进行表征.结果表明,BMS-CS表面变得粗糙且呈毛刺状,具有较多不规则的褶皱;结晶度的下降也印证了粗糙度的增加;红外图谱中新出现的酯基和苯乙烯基的吸收峰说明亲油单体被接枝到RCS表面;两种原因共同促进了改性材料吸油性能的增加.吸油数据显示,常温下RCS和BMS-CS的吸油量分别为5.23g·g-1和20.12g·g-1,后者是前者的3.85倍,即改性后的材料吸油性能明显增加.     

城市污泥与煤或玉米秆混烧特性及动力学研究

利用热重分析法对城市污泥分别与煤或玉米秆混烧特性进行研究。结果表明:城市污泥燃烧过程存在挥发分析出和燃烧阶段及挥发分和固定碳燃尽阶段两个主要失重区间。城市污泥着火温度低,燃烧温度范围宽,失重速率低,燃尽性能特性指数Cb和综合燃烧特性指数SN性能均低于煤和玉米秆。掺混煤或玉米秆燃烧会改善城市污泥的燃尽特性和综合燃烧特性。采用积分法(Coats-Redfern方程)计算各阶段燃烧反应的动力学参数。混合试样中污泥含量增加,挥发分燃烧阶段活化能减小,固定碳燃烧阶段活化能增加。     

干旱对辽宁省玉米产量影响及风险区划

以辽宁省14个市1967-2006年降水量逐月数据和玉米产量数据为基础,应用滑动直线平均法、相关分析等数理统计方法,结合GIS技术对各地区玉米因旱减产程度及风险大小进行分析。结果表明,不同地区干旱对产量的制约程度不同,据此划分为两类地区:A类地区干旱是玉米产量的主要制约因素,B类地区干旱对玉米产量影响不明显。根据A类地区确定因旱减产指标:当降水负距平分别为20%、20%～40%、40%～60%时对应的玉米减产率分别为5%、5%～11%、11%～17%。综合产量波动、减产强度、抗旱能力三要素进行干旱灾害风险区划,结果显示辽宁省因旱减产风险由西向东逐渐减弱。     

UASB反应器处理淀粉废水的效果及影响因素

介绍了UASB反应器处理玉米淀粉废水的效果,分析了主要因素对处理效果的影响。淀粉废水处理实际工程的运行数据表明,UASB反应器处理玉米淀粉废水具有稳定的处理效果,COD去除率在83%以上,BOD5去除率在90%以上,出水满足后续好氧处理工艺的要求;有机负荷、pH值、碱度、出水循环、SO42-和悬浮物等是影响处理效果和颗粒污泥形成及其性质的几个关键因素。     

关于单株玉米耗水量的探讨

一株玉米一生究竟需要消耗多少水,目前尚无定论。国内外许多著作中,一株玉米一生蒸腾耗水量常常引用"200kg"这一数据。在《中国玉米栽培学》中,则提出了蒸腾耗水量为80kg/株,两者相差2.5倍。文章通过中国科学院禹城综合试验站大量的玉米农田蒸发实验数据,分析了生长在自然条件下单株玉米的蒸腾耗水量和玉米平均总耗水(包括蒸腾量和棵间蒸发量),得到如下结果:①单株春玉米的总耗水量为100kg/株左右,蒸腾耗水量为60kg/株左右;②华北平原夏玉米总耗水量为50~80kg/株,蒸腾耗水量为30~40kg/株;③只要土壤水分不出现长期干旱,土壤水分状况不会对单株玉米耗水量产生大的影响;④种植密度对单株玉米需水量产生重大影响,当玉米种植密度由5.0×10⁴株/hm²增至10.0×10⁴株/hm²时,总耗水量仅增加13.18%,而单株耗水量减少了44.48%。这些数据可供参考。     

Comparison of the Photodegradation of Imazethapyr in Aqueous Solution,on Epicuticular Waxes,and on Intact Corn (Zea Mays) and Soybean (Glycine Max) Leaves

A direct, controlled comparison of the photodegradation of imazethapyr has been made between imazethapyr in aqueous solutions, imazethapyr on the surface of epicuticular waxes of corn and soybean plants, and imazethapyr on the surface of intact corn and soybean plant leaves. In some experiments, the imazethapyr solutions were allowed to evaporate partially or fully after application to better model environmental conditions. The photodegradation of imazethapyr was fastest in aqueous solutions (k?=?0.16?±?0.02?h^?1) and slowest on the surface of corn and soybean plants (k_corn?=?0.00048?±?0.001?h^?1 and k_soy?=?0.00054?±?0.003?h^?1). Experiments allowing evaporation during irradiation have intermediate rate constants (e.g., k_corn?=?0.082?±?0.005?h^?1). Finally, identification of photoproducts was also examined on epicuticular waxes of corn and soybean plants for the first time.     

Influence of Bioenergy Crop Production and Climate Change on Ecosystem Services

Land use change can significantly affect the provision of ecosystem services and the effects could be exacerbated by projected climate change. We quantify ecosystem services of bioenergy‐based land use change and estimate the potential changes of ecosystem services due to climate change projections. We considered 17 bioenergy‐based scenarios with Miscanthus, switchgrass, and corn stover as candidate bioenergy feedstock. Soil and Water Assessment Tool simulations of biomass/grain yield, hydrology, and water quality were used to quantify ecosystem services freshwater provision (FWPI), food (FPI) and fuel provision, erosion regulation (ERI), and flood regulation (FRI). Nine climate projections from Coupled Model Intercomparison Project phase‐3 were used to quantify the potential climate change variability. Overall, ecosystem services of heavily row cropped Wildcat Creek watershed were lower than St. Joseph River watershed which had more forested and perennial pasture lands. The provision of ecosystem services for both study watersheds were improved with bioenergy production scenarios. Miscanthus in marginal lands of Wildcat Creek (9% of total area) increased FWPI by 27% and ERI by 14% and decreased FPI by 12% from the baseline. For St. Joseph watershed, Miscanthus in marginal lands (18% of total area) improved FWPI by 87% and ERI by 23% while decreasing FPI by 46%. The relative impacts of land use change were considerably larger than climate change impacts in this paper. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.     

Assessment of Bioenergy Cropping Scenarios for the Boone River Watershed in North Central Iowa,United States

Several biofuel cropping scenarios were evaluated with an improved version of Soil and Water Assessment Tool (SWAT) as part of the CenUSA Bioenergy consortium for the Boone River Watershed (BRW), which drains about 2,370 km² in north central Iowa. The adoption of corn stover removal, switchgrass, and/or Miscanthus biofuel cropping systems was simulated to assess the impact of cellulosic biofuel production on pollutant losses. The stover removal results indicate removal of 20 or 50% of corn stover in the BRW would have negligible effects on streamflow and relatively minor or negligible effects on sediment and nutrient losses, even on higher sloped cropland. Complete cropland conversion into switchgrass or Miscanthus, resulted in reductions of streamflow, sediment, nitrate, and other pollutants ranging between 23‐99%. The predicted nitrate reductions due to Miscanthus adoption were over two times greater compared to switchgrass, with the largest impacts occurring for tile‐drained cropland. Targeting of switchgrass or Miscanthus on cropland ≥2% slope or ≥7% slope revealed a disproportionate amount of sediment and sediment‐bound nutrient reductions could be obtained by protecting these relatively small areas of higher sloped cropland. Overall, the results indicate that all biofuel cropping systems could be effectively implemented in the BRW, with the most robust approach being corn stover removal adopted on tile‐drained cropland in combination with a perennial biofuel crop on higher sloped landscapes. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.