Soil Moisture Controls the Denitrification Loss of Urea Nitrogen from Silty Clay Soil

Relative control of soil moisture [30, 60, and 80 percent water-holding capacity (WHC)] on nitrous oxide (N₂O) emissions from Fargo-Ryan soil, treated with urea at 0, 150, and 250 kg N ha^?1 with and without nitrapyrin [2-chloro-(6-trichloromethyl) pyridine] (NP), was measured under laboratory condition for 140 days. Soil N₂O emissions significantly increased with increasing nitrogen (N) rates and WHC levels. Urea applied at 250 kg N ha^?1 produced the greatest cumulative N₂O emissions and averaged 560, 3919, and 15894 µg kg^?1 at 30, 60, and 80 percent WHC, respectively. At WHC ≤ 60 percent, addition of NP to urea significantly reduced N₂O losses by 2.6- to 4.8-fold. Additions of NP to urea reduced N₂O emission at rates similar to the control (0 N) until 48 days for 30 percent WHC and 35 days for 60 and 80 percent WHC. These results can help devise urea-N fertilizer management strategies in reducing N₂O emissions from silty-clay soils.     

2004 Mack MD11柴油机燃料加氢后NOx与微粒排放特性

为了降低柴油机的排放,氢作为柴油机燃料的研究正在引起研究者的关注。该文进行了在2004 Mack MD11柴油机中添加不同比例氢气(最高氢气比例达7%)与柴油形成混合燃料的NOx、微粒(PM,particulate matter)排放特性研究。研究表明:负荷工况不同,添加氢气对NOx排放特性的影响不同;随着添加氢的增加,有NO转化为NO2现象;NOx排放很大程度还与发动机可变截面涡轮增压系统(VGT,variable-geometry gas turbine)和废气再循环系统(EGR,exhaust gas recirculation)工作状况有关;添加氢气后即使在大、全负荷下,NOx排放量也没有明显增加。这主要归因于2004 Mack MD11采取了EGR,并且随着负荷增加,EGR率也在增加。在各种负荷工况下,添加氢气对降低PM排放量的作用明显,PM排放量减小率一般达50%以上,最高达75%。     

Spatial variability of nitrous oxide emissions in an unmanaged old‐growth beech forest

Nitrous oxide (N₂O) is a high‐impact greenhouse gas. Due to the scarcity of unmanaged forests in Central Europe, its long‐term natural background emission level is not entirely clear. We measured soil N₂O emissions in an unmanaged, old‐growth beech forest in the Hainich National Park, Germany, at 15 plots over a 1‐year period. The average annual measured N₂O flux rate was (0.49 ± 0.44) kg N ha^–1 y^–1. The N₂O emissions showed background‐emission patterns with two N₂O peaks. A correlation analysis shows that the distance between plots (up to 380 m) does not control flux correlations. Comparison of measured data with annual N₂O flux rates obtained from a standard model (Forest‐DNDC) without site‐specific recalibration reveals that the model overestimates the actual measured N₂O flux rates mainly in spring. Temporal variability of measured N₂O flux was better depicted by the model at plots with high soil organic C (SOC) content. Modeled N₂O flux rates were increased during freezing only when SOC was > 0.06 kg C kg^–1. The results indicate that the natural background of N₂O emissions may be lower than assumed by most approaches.     

规模猪场沼气工程泄漏监测

近几年,沼气工程发展迅速,随之产生的安全管理等问题越来越受到重视.该研究对北京某猪场沼气工程进行泄漏监测,研究泄漏占总产量的比例并与CDM方法学AMS Ⅲ.D中泄漏默认值10％进行对比,分析泄漏易发点,并研究欧洲标准是否适用于该猪场沼气工程.北京猪场沼气工程CSTR和USR的CH4泄漏比例分别为0.6％和3％,该猪场沼气工程运行管理良好,泄漏量较少.泄漏易发生的位置为储气罐处,易发生泄漏的设备有进油口、压力表等.     

铁岭市粮食干燥业发展分析与对策

通过对辽宁省铁岭市粮食烘干机使用情况进行调研,系统分析和总结了目前粮食干燥行业在能耗、环保措施等方面存在的问题,并针对行业资源管理、行业技术标准、节能减排新技术等内容,提出改进意见和发展设想。     

低碳减排对促进绿色农业农机的贡献和意义

近年来,由于全球经济突飞发展,碳过量排放引起温室效应,造成全球气候变暖,保护环境已成为时代主旋律,为此,沛县农机部门把握时代机遇,积极推进低碳减排,促进绿色农机化作业。     

笼养肉鸡不同季节CH4和CO2排放研究

为研究规模化肉鸡场温室气体排放系数,给我国畜牧业温室气体清单编制和选择减排技术提供依据,选择山东某商业化肉鸡养殖场,对肉鸡生产过程中CO2和CH4的排放情况进行了研究。利用多功能气体分析仪对肉鸡舍CH4和CO2的浓度进行测定,肉鸡舍通风量测定则采用风机风量现场测定系统,根据不同季节连续5d测试结果计算提出肉鸡的CH4和CO2排放因子。结果表明：肉鸡在36-42d龄间的CH4和CO2的排放因子分别为（0．276＋0．19）g·d^-1·bird^-1（58．9＋37．2g·d^-1·AU^-1）,154．4＋45．7g·d^-1·bird^-1（33．5＋8．0kg·d^-1·AU^-1）,不同季节CH4排放因子存在显著差异,夏季最高为0．552g·d^-1·bird^-1,冬季最低为0．111g·d^-1·bird^-1,春季和秋季分别为0．187g·d^-1·bird^-1和0．254g·d^-1·bird^-1;CO2排放因子夏秋季节差异不显著,分别为186．8g·d^-1·bird^-1和179．8g·d^-1·bird^-1,但显著高于春季（163．4g·d^-1·bird^-1）和冬季（87．4g·d^-1·bird^-1）;分析表明,鸡舍通风量与CH4排放因子呈现显著线性相关关系,以CO2形式损失的碳（C）占总饲料碳（C）投入的56．1％,是碳（C）损失的主要部分,仅有占饲料碳（C）投入0．27％的碳以CH4形式损失。     

柴油机的颗粒排放物与捕捉器

本文介绍了柴油机颗粒排放物的组成、成因、危害以及国际上主要的颗粒排放标准、试验工况和我国的现状,同时介绍了三种揣捉器(蜂窝陶瓷颗粒捕捉器、泡沫陶瓷颗粒捕捉器和金属丝网颗粒捕捉器)的构造、捕捉机理及其主要特点和影响捕捉器主要性能(捕集效率、捕捉器压差、捕捉器压力升高率等)的一些主要参数。     

Effects of nitrogen fertilization and irrigation on N2O emissions from a sandy soil in Germany

The aim of this study was to investigate the effect of supplemental irrigation on the amount of N₂O emissions on a sandy soil in north-east Germany. N₂O flux measurements were carried out over two vegetation periods from the emergence of plants to harvest. The level of N₂O emissions was low, which is typical for sandy soils in north-east Germany. In both periods, irrigation had no increasing effect on N₂O emissions. Relevant factors were the soil temperature and the soil water-filled pore space (WFPS), which were mainly influenced by weather conditions. This may indicate that nitrification was the main source of N₂O emissions. In conclusion, this study has confirmed that sandy soils under weather conditions of north-east Germany generally have a very low potential for N₂O emissions.     

Is burial of wheat straw in ditches a way to reduce CH4 emissions from rice cultivation?

Abstract

Burial of wheat straw in ditches and incorporation of wheat straw are the two main ways of returning wheat straw prior to rice cultivation in China. To examine the effect of burying wheat straw in ditches on CH₄ emissions from rice cultivation, a field experiment was conducted at Yixing, Jiangsu, China in 2004. CH₄ flux was measured using a closed-chamber technique in three treatments (CK, no wheat straw application; WI, evenly incorporating 3.75 t ha^?1 wheat straw into the 0.1 m topsoil; WD, burying 3.75 t ha^?1 wheat straw in 0.14-m deep by 0.25-m wide ditches). Seasonal CH₄ emissions ranged from 49.7 to 218.4 kg CH₄ ha^?1. The application of wheat straw in these two ways significantly increased CH₄ emissions by 4.0-fold and 4.4-fold, respectively (P < 0.05). Although CH₄ flux from the non-ditch area in the WD treatment was as low as that in the CK treatment, it was counter-balanced by extremely high CH₄ flux from the ditch, which was approximately 6.0-fold as much as that from WI, leading to comparability between treatments WI and WD in total CH₄ emissions (P > 0.05). No significant difference was observed between the three treatments in grain yield (P > 0.05). The results indicated that burial of wheat straw in ditches is not a way to reduce CH₄ emission from rice cultivation.