长春南湖富营养化进程中鱼类群落的变化

长春南湖原有鱼类20种。随着富营养化程度的加重,鱼类种类数减少,一些种类绝迹。1992年实施生态工程治理后,鱼类组成以人工放养种类为主。鱼产量波动幅度较大,自20世纪60年代以来呈下降趋势,80年代末达到最低点,90年代有所回升。目前以养殖鱼类为主体,产量较为稳定。鱼类以II龄和III龄个体所占比例最大,I龄和高龄个体较少。     

Enhancement of biomethane production from cattle manure with codigestion of dilute acid pretreated lignocellulosic biomass

It is well known that dilute sulfuric acid pretreatment of the lignicellulosisc biomass is an effective approach used for the production of the ethanol. However, there are less studies on the biogas production from the pretreated lignocellulosics and hardly data available on the codigestion of cattle manure with the pretreated lignocellulosisc material. The aim of this study was to evaluate biomethane production potential of codigestion of cattle manure with dilute acid pretreated lignocellulosic biomass. Sugarcane bagasse and rice husk was pretreated with dilute sulfuric acid or phosphoric acid at 121°C for 20 minutes and subsequently subjected to anaerobic digestion alone or codigested with cattle manure.

The results showed that codigestion of 1% phosphoric acid pretreated rice husk with cattle manure led to the highest methane production of 115 Nmlg^?1VS while monodigestion of cattle manure and phosphoric acid pretreated rice husk produced 98 and 87 Nmlg^?1VS, respectively. An inhibition was observed in anaerobic digestion of sulfuric acid pretreated rice husk and sugarcane bagasse during monodigestion and codigestion with cattle manure.

The study concludes that dilute phosphoric acid pretreated lignocellulosics like sugarcane bagasse and rice husk can be used as a cosubstrate with cattle manure in anaerobic digestion for enhanced methane production. Dilute sulfuric acid pretreatment, which is effective method for the bioethanol production, causes inhibition during anaerobic digestion of the pretreated lignocellulosics.     

Single-phase and two-phase anaerobic digestion of fruit and vegetable waste: Comparison of start-up,reactor stability and process performance

Single-phase and two-phase digestion of fruit and vegetable waste were studied to compare reactor start-up, reactor stability and performance (methane yield, volatile solids reduction and energy yield). The single-phase reactor (SPR) was a conventional reactor operated at a low loading rate (maximum of 3.5 kg VS/m³ d), while the two-phase system consisted of an acidification reactor (TPAR) and a methanogenic reactor (TPMR). The TPAR was inoculated with methanogenic sludge similar to the SPR, but was operated with step-wise increase in the loading rate and with total recirculation of reactor solids to convert it into acidification sludge. Before each feeding, part of the sludge from TPAR was centrifuged, the centrifuge liquid (solubilized products) was fed to the TPMR and centrifuged solids were recycled back to the reactor. Single-phase digestion produced a methane yield of 0.45 m³ CH₄/kg VS fed and VS removal of 83%. The TPAR shifted to acidification mode at an OLR of 10.0 kg VS/m³ d and then achieved stable performance at 7.0 kg VS/m³ d and pH 5.5–6.2, with very high substrate solubilization rate and a methane yield of 0.30 m³ CH₄/kg COD fed. The two-phase process was capable of high VS reduction, but material and energy balance showed that the single-phase process was superior in terms of volumetric methane production and energy yield by 33%. The lower energy yield of the two-phase system was due to the loss of energy during hydrolysis in the TPAR and the deficit in methane production in the TPMR attributed to COD loss due to biomass synthesis and adsorption of hard COD onto the flocs. These results including the complicated operational procedure of the two-phase process and the economic factors suggested that the single-phase process could be the preferred system for FVW.     

武夷山市生活垃圾处理能值分析

对武夷山市规划新建的生活垃圾处理工程,利用能值方法分析填埋-沼气处理工艺,通过绘制能值系统图辨析该系统的能值投入和产出.按照自然/社会、可再生/不可再生的标准将能值投入分成四类并列表计算能值指标:环境负载率(ELR)和能值产出率(EYR).能值指标表明:在目前情况下,填埋-沼气处理方式对环境压力小,"投入/产出"比高,是一种科学合理的处理方式.但是通过分析规划年限内能值指标的变化趋势发现该系统对环境的压力将逐步扩大,系统对外界的能值产出也会降低,这对未来城市发展留下了环境问题隐患.     

Influence of Llamas, Horses, and Hikers on Soil Erosion from Established Recreation Trails in Western Montana, USA

/ Various types of recreational traffic impact hiking trails uniquely and cause different levels of trail degradation; however, trail head restrictions are applied similarly across all types of packstock. The purpose of this study was to assess the relative physical impact of hikers, llamas, and horses on recreational trails. Horse, llama, and hiker traffic were applied to 56 separate plots on an existing trail at Lubrecht Experimental Forest in western Montana. The traffic was applied to plots at intensities of 250 and 1000 passes along with a no-traffic control under both prewetted and dry trail conditions. Soil erosion potential was assessed by sediment yield and runoff (using a Meeuwig type rainfall simulator), changes in soil bulk density, and changes in soil surface roughness. Soil moisture, slope, and rainfall intensity were recorded as independent variables in order to evaluate the extent that they were held constant by the experimental design. Horse traffic consistently made more sediment available for erosion from trails than llama, hiker, or no traffic when analyzed across wet and dry trail plots and high and low intensity traffic plots. Although total runoff was not significantly affected by trail user, wet trail traffic caused significantly greater runoff than dry trail traffic. Llama traffic caused a significant increase in sediment yield compared to the control, but caused erosion yields not significantly different than hiker traffic. Trail traffic did not increase soil compaction on wet trails. Traffic applied to dry trail plots generally resulted in a significant decrease in soil bulk density compared to the control. Decreased soil bulk density was negatively correlated with increased sediment yield and appeared to result in increased trail roughness for horse traffic compared to hiker or llama traffic. Differences described here between llama and horse traffic indicate that trail managers may want to consider managing packstock llamas independent of horses.KEY WORDS: Recreational impacts; Sediment yield; Trail degradation     

世界谷物产量与农业气候资源利用效率

世界谷物产量的农业气候资源利用效率有明显地区差异。谷物产量的综合气候资源利用效率以欧洲最高，为２．７８，其后依次是北美洲１．４３，大洋洲１．４３，亚洲１．４０，南美洲１．１２，非洲最低，为０．６１。相对光能利用率（％）从０．０３（安哥拉）至０．７６（荷兰），热量利用效率（ｋｇ／１℃·ｈａ）从０．０３至２．０３（荷兰、瑞典），降水量利用效率（ｋｇ／·ｈａ）从０．３５（安哥拉）至８．７１（荷兰）（表１－４）。光热、降水量与作物要求的条件配合较一致的地区，谷物转换效率高。干旱、半干旱地区水分容易发挥效率。世界农业气候资源谷物利用潜力很大。中国比高产国家利用效率低主要是单产利用效率低，应以提高单产的资源利用效率为重点。     

论“谁来养活中国”

本文从人口、耕地、单产潜力、消费水平等方面讨论和分析了“谁来养活中国”一文中提到的主要观点和结论,并提出了通过这些讨论和分析应该得到的有益启示。认为应唤起我们对发展农业的紧迫感与危机感,并采取切实措施,唯有如此,我们才能养活自己,我国的经济才能持续稳定发展。     

甘肃省玉米产量的气候特征及其与中国大陆OLR的关系研究

对甘肃省５５个站点的玉米气候产量经ＥＯＦ及ＲＥＯＦ分解后，通过对其载荷量的分析，表明陇东南地区是甘肃省玉米产量最具代表性的区域，并进一步将甘肃省玉米气候产量划分为５个自然气候区：陇东区、陇南区、中部及阴湿山区、干旱山区、河西灌溉农业区。玉米气候产量的第一主分量可代表甘肃省玉米气候产量的时间趋势。它与同年５～９月份ＯＬＲ有很好的相关关系。     

进水与曝气方式对SBR中活性污泥产率和性能的影响

在实验室SBR几种运行方式研究的基础上，分析了不同进水与曝气方式对SBR中活性污泥产率和性能的影响原因。结果表明：（1）在反应阶段分级曝气方式下，SBR反应器的污泥产率明显低；而短时进水方式下，反应器的污泥性能最佳。（2）克服了SBR反应初期的高需氧率，能大大加速此后的生化反应。