地表UV-B辐射增强对土壤-冬小麦系统呼吸速率和N2O排放的影响

通过室外盆栽实验,用静态箱-气相色谱法测定土壤-冬小麦系统的呼吸速率和N₂O排放通量,研究了UV-B辐射增强20%对土壤-冬小麦系统的呼吸速率和N₂O排放的影响.结果表明,相同的气象条件和田间管理下,UV-B辐射增强处理对呼吸速率和N₂O排放的季节变化模式无明显影响.在返青期,UV-B辐射增强显著降低了土壤-冬小麦系统的呼吸速率,但对N₂O的排放通量没有产生显著影响;在拔节孕穗期,UV-B辐射增强处理显著降低了土壤-冬小麦系统的呼吸速率和N₂O的排放通量;在抽穗-成熟期,UV-B辐射增强处理对土壤-冬小麦系统的呼吸速率和N₂O的排放没有显著影响.返青-齐穗期,UV-B增强处理显著降低土壤-冬小麦系统的N₂O累积排放量;但从齐穗开始至小麦成熟,UV-B增强处理对土壤-冬小麦系统的N₂O累积排放量没有显著影响.     

Emissions of SO2, NO and N2O in a circulating fluidized bed combustor during co-firing coal and biomass

This paper presents the experimental investigations of the emissions of SO2, NO and N2O in a bench scale circulating fluidized bed combustor for coal combustion and co-firing coal and biomass. The thermal capacity of the combustor is 30 kW. The setup is electrically heated during startup. The influence of the excess air, the degree of the air staging, the biomass share and the feeding position of the fuels on the emissions of SO2, NO and N2O were studied. The results showed that an increase in the biomass shares resulted in an increase of the CO concentration in the flue gas, probably due to the high volatile content of the biomass. In co-firing, the emission of SO2 increased with increasing biomass share slightly, however, non-linear increase relationship between SO2 emission and fuel sulfur content was observed. Air staging significantly decreased the NO emission without raising the SO2 level. Although the change of the fuel feeding position from riser to downer resulted in a decrease in the NO emission level, no obvious change was observed for the SO2 level. Taking the coal feeding position R as a reference, the relative NO emission could significantly decrease during co-firing coal and biomass when feeding fuel at position D and keeping the first stage stoichiometry greater than 0.95. The possible mechanisms of the sulfur and nitrogen chemistry at these conditions were discussed and the ways of simultaneous reduction of SO2, NO and N2O were proposed.     

Effects of long-term amendment of organic manure and nitrogen fertilizer on nitrous oxide emission in a sandy loam soil

To understand the effects of long-term amendment of organic manure and N fertilizer on N2O emission in the North China Plain, a laboratory incubation at different temperatures and soil moistures were carried out using soils treated with organic manure （OM）, half organic manure plus half fertilizer N （HOM）, fertilizer NPK （NPK）, fertilizer NP （NP）, fertilizer NK （NK）, fertilizer PK （NK） and control （CK） since 1989. Cumulative N2O emission in OM soil during the 17 d incubation period was slightly higher than in NPK soil under optimum nitrification conditions （25℃ and 60% water-filled pore space, WFPS）, but more than twice under the optimum denitrification conditions （35℃ and 90% WFPS）. N2O produced by denitrification was 2.1-2.3 times greater than that by nitrification in OM and HOM soils, but only 1.5 times greater in NPK and NP soils. These results implied that the long-term amendment of organic manure could significantly increase the N2O emission via denitrification in OM soil as compared to NPK soil. This is quite different from field measurement between OM soil and NPK soil. Substantial inhibition of the formation of anaerobic environment for denitrification in field might result in no marked difference in N2O emission between OM and NPK soils. This is due in part to more rapid oxygen diffusion in coarse textured soils than consumption by aerobic microbes until WFPS was 75% and to low easily decomposed organic C of organic manure. This finding suggested that addition of organic manure in the tested sandy loam might be a good management option since it seldom caused a burst of N2O emission but sequestered atmospheric C and maintained efficiently applied N in soil.     

Organic matter and concentrated nitrogen removal by shortcut nitrification and denitrification from mature municipal landfill leachate

An UASB＋Anoxic/Oxic （A/O） system was introduced to treat a mature landfill leachate with low carbon-to-nitrogen ratio and high ammonia concentration. To make the best use of the biodegradable COD in the leaehate, the denitrifieation of NOx^--N in the reeireulation effluent from the elarifier was carried out in the UASB. The results showed that most biodegradable organic matters were removed by the denitrifieation in the UASB. The NH4^＋-N loading rate （ALR） of A/O reactor and operational temperature was 0.28- 0.60 kg NH4^＋-N/（m^3-d） and 17-29℃ during experimental period, respectively. The short-cut nitrification with nitrite accumulation efficiency of 90%-99% was stabilized during the whole experiment. The NH4^＋-N removal efficiency varied between 90% and 100%. When ALR was less than 0.45 kg NH4^＋-N/（m^3.d）, the NH4^＋-N removal efficiency was more than 98%. With the influent NH4^＋-N of 1200-1800 mg/L, the effluent NH4^＋-N was less than 15 mg/L. The shortcut nitrification and denitrifieation can save 40% carbon source, with a highly efficient denitrifieation taking place in the UASB. When the ratio of the feed COD to feed NH4^＋-N was only 2-3, the total inorganic nitrogen （TIN） removal efficiency attained 67%-80%. Besides, the sludge samples from A/O reactor were analyzed using FISH. The FISH analysis revealed that ammonia oxidation bacteria （AOB） accounted for 4% of the total eubaeterial population, whereas nitrite oxidation bacteria （NOB） accounted only for 0.2% of the total eubaeterial population.     

2008年奥运期间华北区域大气污染物本底浓度变化与分析

为了解华北区域的大气背景状况,评估污染源限排对区域空气质量的影响以及污染物输送在区域污染中的作用,在2008年奥运期间(6～11月),对华北区域兴隆大气本底监测站主要污染物NOx、SO2、O3和PM2.5进行了连续在线观测,对不同时间段的污染物的浓度水平和日变化特征进行了比较分析,结合地面气象资料和后向轨迹模式初步探讨了污染物的区域传输过程,并对区域不同站点的污染情况进行了初步比较.结果显示,2008年夏季兴隆本底站NOx、SO2、O3与PM2.5平均浓度分别为8.4、10.5、126.0和59.8μg·m-3,秋季平均浓度分别为11.7、17.2、97.5和30.7μg·m-3.奥运时段(2008-08-08～2008-08-24),兴隆NOx、SO2、O3和PM2.5平均浓度分别为6.6、6.8、100.5和33.3μg·m-3,较奥运时段前后平均浓度分别降低了29.0%、46.9%、18.6%和36.5%,与2007年奥运时段同期观测结果相比,NOx浓度下降了62.5%,PM2.5浓度下降了29.0%,奥运时段华北区域空气质量明显改善.在污染物限排之前,兴隆主要污染物的日变化形势都是夜间浓度低,白天浓度不断升高,在傍晚17:00～20:00之间达到峰值,显示了污染物区域输送在兴隆的累积,而污染源排放控制期间污染物白天的积累过程明显减弱,区域输送的污染物含量降低,这些结果表明北京及周边地区污染源的联合控制取得了明显效果.兴隆夏秋季节主要受偏南方向的季风影响,在此方向上对应的污染物浓度值最高,偏南方向上的区域污染输送对兴隆影响较大.将京津冀区域不同站点间的污染物浓度进行比较分析发现,华北区域夏秋季NOx和SO2污染较轻,O3污染不容乐观,PM2.5污染严重,需要引起足够重视.     

夏秋季石家庄大气污染变化特征观测研究

研究了石家庄夏秋季节大气污染状况及2008奥运前后大气污染物浓度变化特征.2007和2008年夏秋季节,使用全自动在线观测仪器对石家庄大气环境质量进行连续监测,目的是阐明奥运期间石家庄污染物减排对当地大气环境的改变,探讨石家庄地区产生的大气污染物对北京及周边地区可能的影响.结果表明,除了氮氧化物,其他污染物均有超标情况出现,其中夏秋季节O3浓度较高,小时最大浓度值平均(O3-Max)分别为(177.2±63.0)和(105.8±61.7)μg·m-3,NO和NO2在夏秋季节的浓度分别为(4.5±4.0)、(32.7±12.4)μg·m-3和(21.5±16.9)、(60.5±16.9)μg·m-3,SO2浓度分别为(72.0±27.5)和(92.0±44.4)μg·m-3,PM2.5和PM10浓度达到(102.3±47.6)、(153.3±58.3)μg·m-3和(95.8±50.0)、(147.4±67.0)μg·m-3;奥运期间各类污染物浓度显著下降,NOx、O3-Max、SO2、PM2.5和PM10浓度分别为(43.8±15.0)、(142.0±54.9)、(52.4±18.8)、(76.7±35.1)和(116.5±38.8)μg·m-3,其中SO2、PM2.5和PM10分别较2008年监测期间平均值降低34.6%、22.8%和21.0%.本研究系统分析了夏秋季节石家庄大气污染状况,为评估当地大气污染控制措施提供了科学依据.     

活性炭纤维电极电还原产H2O2的实验研究

利用活性炭纤维作为阴极,比较了活性炭纤维电极和石墨板电极产H2O2的浓度,并对影响活性炭纤维电极产H2O2的因素(pH、电流密度和电解质浓度)进行了研究.研究发现,活性炭纤维电极电还原产生H2O2的浓度远大于石墨板电极.当实验在pH=3.00、电流密度8.89 mA/cm2和电解质(Na2SO4)浓度0.05 moL/...     

水钠锰矿的Mn（Ⅲ）分布及Na4P2O7溶液处理对其铅吸附性能的影响

以深入理解水钠锰矿结构中低价锰离子的含量及分布对其铅吸附性能的影响为目的,通过不同pH（pH为2、4、5）的焦磷酸钠溶液络合浸提酸性水钠锰矿结构中的Mn（Ⅱ）和Mn（Ⅲ）,研究了浸提锰离子的形态、含量、矿物的锰平均氧化度和Pb2＋的吸附量及其伴随Mn2＋、H＋释放量的变化.结果表明,锰平均氧化度为3.670的酸性水钠锰...     

不同氮、磷肥用量下双季稻田的CH4和N2O排放

以红壤双季稻田为研究对象,采用静态暗箱-气相色谱法对2009年水稻生长期内不施肥（CK）,平衡施肥（BF）、减氮磷一（DNP1）、减氮磷二（DNP2）和增氮磷（INP）等5个处理的CH4和N2O排放通量以及环境因素进行观测.结果表明,早稻生长期间BF、DNP1、DNP2和INP的CH4平均排放通量为4.57、5.42、...     

UV-B增强对稻田呼吸速率、CH4和N2O排放的影响

于水稻生长季进行室外盆栽试验,人工模拟UV-B辐射增强20%,采用静态箱-气相色谱法测定稻田生态系统的呼吸速率、CH4和N2O排放通量,研究UV-B辐射增强对稻田生态系统呼吸速率、CH4和N2O排放通量的影响.结果表明,UV-B辐射增强没有改变稻田呼吸速率、CH4和N2O排放通量的季节变化规律;与对照相比,平均呼吸速率...