地膜覆盖和施氮对菜地CH4排放的影响

以位于西南大学农业部重庆紫色土生态环境重点野外科学观测试验站内辣椒-萝卜轮作菜地为研究对象,采用静态暗箱/气相色谱法,进行为期2 a的田间原位观测,探讨地膜覆盖和不同施氮处理对菜地CH_4排放的影响.本实验设置8个处理,分别为对照常规(NN0)、对照覆膜(FN0),低N常规(NN1)、低N覆膜(FN1),中N常规(NN2)、中N覆膜(FN2),高N常规(NN3)、高N覆膜(FN3),研究地膜覆盖和施氮对菜地CH_4的排放特征和影响因素以及土壤碳氮组分的变化规律.结果表明,覆膜与常规两种种植方式对于菜地CH_4的排放没有明显差异. 2014年5月～2016年4月,覆膜种植下无氮、低氮、中氮和高氮菜地CH_4年均累积吸收量分别为28. 96、51. 90、43. 43和34. 41 mg·m~(-2),常规种植下CH_4年均累积吸收量分别为40. 76、63. 56、62. 77和21. 92 mg·m~(-2).不同施氮梯度对于菜地CH_4的排放没有显著影响.菜地CH4的吸收量与土壤温度呈显著正相关关系,与土壤含水率则呈现为显著负相关关系.地膜覆盖在辣椒季加速了土壤碳素的矿化,而在萝卜季则没有显著影响.     

城市温室气体清单评价研究

城市消费了大量的能源,是全球人类活动温室气体的最大排放源,在应对气候变化中起到关键作用.城市温室气体清单评价成为重要的基础性工作,对于制定城市减排目标和计划、评估减排措施效果具有重要的意义.然而,城市开放的空间系统结构导致城市温室气体清单核算面临许多困难和挑战.本文对国内外城市温室气体清单方法和案例进行了回顾与展望,研究内容主要集中在比较城市清单和国家清单方法、联系和区别,分析清单编制的不确定性,在此基础上提出可借鉴的经验与启示,以期推动我国城市温室气体清单研究发展.     

二氧化碳的失汇

温室气体的大量排放所造成温室效应的加剧是全球变暖的基本原因。全球和区域碳循环已成为全球气候变化研究的重要内容之一。碳汇的巨大功能深受世人瞩目,影响碳汇增加因素的研究也越加必要。     

镉在不同土壤和蔬菜中残留规律研究

研究了镉在不同类型土壤和蔬菜中的残留积累规律.结果表明,含镉污水灌溉是造成农田土壤镉污染主要原因之一.土壤中镉残留量随污水镉浓度增加而增高.土壤镉含量与蔬菜中镉含量呈显著正相关.供试土壤及蔬菜可食部分镉的累积顺序为:粘土>壤土;壤土蔬菜>粘土蔬菜,小白菜(叶)>萝卜(根)>莴苣(茎)>辣椒(果)>豇豆(豆).     

新疆农业碳减排管理经验初探

研究了美国国际集团(AIG)注资新疆昌吉玛纳斯等3县开展温室气体减排项目的推进过程.这是在中国成功开展的第一例农业温室气体自愿减排项目,该项目共减排温室气体21×104t CO2当量.主要通过农户沼气推广、沙漠防沙林种植、农业滴灌灌溉等项目,达到温室气体减排、节约能源、防沙造林、改善当地的生态环境、增加农民收入等目的....     

发达国家温室气体减排现状及对我国的启示

气候变化是当前全世界关注的焦点问题,大气中温室气体浓度的不断升高与人类活动存在密切的联系.温室气体的历史排放主要是由发达国家产生的,发达国家对气候变化负有主要的责任.目前发达国家温室气体减排履约的整体情况不容乐观,主要发达国家的排放量呈上升趋势,但一些发达国家的减排经验还是值得借鉴的.本文在总结发达国家温室气体减排政策和措施的基础上,结合我国实际情况,提出了我国温室气体减排的可能对策.     

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.     

Comparing Forecasts of the Global Impacts of Climate Change

This paper utilizes the predictions ofseveral Atmosphere-Ocean GeneralCirculation Models and the Global ImpactModel to create forecasts of the globalmarket impacts from climate change. Theforecasts of market impacts in 2100 varyconsiderably depending on climate scenariosand climate impact sensitivity. The modelsdo concur that tropical nations will behurt, temperate nations will be barelyaffected, and high latitude nations willbenefit. Although the size of theseeffects varies a great deal across models,the beneficial and harmful effects areoffsetting, so that the net impact on theglobe is relatively small in almost alloutcomes. Looking only at market impacts,the forecasts suggest that while the globalnet benefits of abatement are small, thedistribution of damages suggests a largeequity problem that could be addressedthrough a compensation program. The largeuncertainty surrounding these forecastsfurther suggests that continued monitoringof both the climate and impacts isworthwhile.     

土壤有机质矿化与温室气体释放初探

通过土壤有机质的矿化作用，模拟估算温室气体在中国土壤中的释放量，结果表明，ＣＯ_２从土壤中的释放量为３７．５亿ｔ／ａ，ＣＨ_４从稻田中的释放量为０．２０亿ｔ／ａ，Ｎ_２Ｏ从稻田中的释放量为３．４５万ｔ／ａ。对土壤中温室气体释放估算提供了一种简便方法。由于掌握资料不足，准确估算需进一步研究。     

城郊菜园土污染状况调查与评价

南京市郊菜园土中Ａｓ、Ｈｇ、Ｃｄ、Ｐｂ四种元素的含量呈逐年上升趋势。除Ａｓ外，其余３种元素的含量均为土壤背景值的２￣３倍。综合评价表明，供试土样中约５０％以上的样点不再适宜种植蔬菜作物而只宜作林业用地或城建、道路及工矿用地。