Tillage, cropping systems, and nitrogen fertilizer source effects on soil carbon sequestration and fractions

Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0- to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH(4)NO(3) and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cotton-rye/cotton-corn than in cotton-cotton-corn and greater with NH(4)NO(3) than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm after 10 yr was greater with poultry litter than with NH(4)NO(3) in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH(4)NO(3). Poultry litter also increased PCM and MBC compared with NH(4)NO(3). Cropping increased SOC, POC, and PCM compared with fallow in NT. Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO(2) levels, and improve soil and environmental quality.     

微波法复合絮凝剂PAFC-PAM的制备及脱色性能

研究了以三氯化铝,三氯化铁和阳离子聚丙烯酰胺为原料,在微波辐照下制备PAFC-PAM复合絮凝剂的工艺条件,探讨了pH值、复合絮凝剂投加量对活性染料模拟废水脱色率的影响,并考察了其对实际印染废水的处理效果。结果表明:在PAM/PAFC质量比为0.25、微波合成功率150W、微波时间3min制得的复合絮凝剂,浊度去除率为98.8%。在pH=8,投加量为42mg/L的最佳絮凝条件下,复合絮凝剂对模拟染料废水脱色率高达97%。与PAFC和PAM相比,PAFC-PAM具有较宽的pH适宜范围和较低的投加量且对实际印染废水的处理效果优于PAFC和PAM。     

地铁运行引起的地面振动实测及传播规律分析

对地铁线路某区间段的地面振动进行实测,采集不同测线和不同测点处的水平方向、竖直方向加速度,并转化为傅里叶幅值谱对其进行衰减规律分析。利用公式将加速度记录换算为振级和分频振级,参照相关的国家标准分析不同距离处的振级和频率成分。对比同一加速度记录中的两对开方向列车引起的地面振动,进一步分析振动衰减的规律。所得到的结果可供地面建筑的隔振减振及城市轨道的规划和设计参考。