温度与有机负荷对猪粪厌氧发酵过程的影响

为提高畜禽养殖场沼气工程能源利用效率,降低工程运行成本.该文通过全混式半连续试验,以猪粪为发酵原料,研究不同温度(20、28、38℃)和有机负荷(0.3、1.3、2.3、3.3、4.3 kg/(m3·d))条件下,甲烷产率、挥发性脂肪酸(volatile fatty acid,VFA)及总无机碳(total inorganic carbon,TIC)的变化特征.结果表明:20℃条件下,反应器启动缓慢,甲烷产率低.当有机负荷增加全1.3 kg/(m3·d)以上时,反应器运行不稳定,需外加NaHCO3调节pH值;在28℃与38℃条件下,各有机负荷甲烷产率无明显差异,但是在较高有机负荷3.3和4.3 kg/(m3·d)下运行时,28℃条件下产生挥发性脂肪酸积累的现象,系统缓冲能力缺乏,VFA/TIC值分别达到0.4和0.6.当实际沼气工程低负荷率运行时,可选择28℃作为发酵温度,以达到节省能源、提高沼气工程经济效益的目的.该研究可为实际沼气工程运行管理提供数据参考.     

Direct Measurement of CO2 Retention in Arable Soils with pH Above 6.5 During Barometric Process Separation Incubation

The barometric process separation(BaPS)technique is a well-established incubation method to simultaneously measure gross nitrification and respiration rates in soil.Its application,however,is still critical in soils with pH above 6.5.Here,a substantial part of microbial CO_2 production is retained in soil solution(CO_2,aq)due to shifts in the carbonate equilibrium.This may lead to substantial errors in gas balance calculation.Yet,utilization of the BaPS technique is only reliable if the critical term is adequately quantified.We present an easy,inexpensive,and direct method,the sterilization-CO_2-injection(SCI)method,to measure CO_2 retention during soil incubation.Sterilized soil was incubated in the BaPS system,and defined volumes of CO_2 were injected to stepwise increase CO_2partial pressure(p CO_2)inside the chamber and to analyse the physicochemical equilibration process.Five exemplary agricultural soils from Northeast China and Southwest Germany were used for method establishment,presenting pH values between 4.4 and 7.6 and carbonate contents between 0% and 3.9%.We observed that in soils with pH6.5,70%–90% of the injected CO_2 was taken up by the soil until the equilibrium inside the chamber was re-established.As expected,in soils with low pH(6.5),measured CO_2 retention was low.CO_2 retention patterns were sensitive to incubation temperature with tri-fold dissolution capacity at 5~?C compared to 25?C,but insensitive to variations in soil water content.The resulting soil-specific relationship between p CO_2 and CO_2,aq concentration allowed the quantification of CO_2,aq concentration as a function of headspace p CO_2.     

追忆国际卓越小麦育种家拉贾拉姆

拉贾拉姆博士从事小麦育种研究50多年,在布劳格博士创立的国际小麦育种的基础上,实现了CIMMYT小麦育种全球化,主要贡献包括四个方面:(1)大规模开展冬春杂交,在产量、抗性和适应性等方面取得了重大进展;(2)将慢锈性理念系统融入小麦育种项目,成功培育并在全世界推广高产慢病性品种;(3)耐酸性土壤和耐旱育种方面取得了显著...