黄浦江上游蔬菜田氮素流失规律测坑研究

通过测坑试验,研究了黄浦江上游蔬菜田渗漏水中氮素的变化动态和流失规律。结果表明,蔬菜田渗漏水中氮素以NO3^--N为主,NO3^--N作为氮素在土壤中流失的主要形态将成为施用氮肥造成地下水污染的重要来源;施用精制有机肥或粗猪粪代替部分化学氮肥有利于减少蔬菜田渗漏水中氮素的流失。     

Peroxyacetyl nitrate (PAN) concentrations in the Antarctic troposphere measured during the photochemical experiment at Neumayer (PEAN'99)

Because investigations of PAN at higher southern latitudes are very scarce, we measured surface PAN concentrations for the first time in Antarctica. During the Photochemical Experiment at Neumayer (PEAN'99) campaign mean surface PAN mixing ratios of 13±7 pptv and maximum values of 48 pptv were found. When these PAN mixing ratios were compared to the sum of NO_x and inorganic nitrate they were found to be equal or higher. Low ambient air temperatures and low PAN concentrations caused a slow homogeneous PAN decomposition rate of approximately 5×10⁻² pptv h⁻¹. These slow decay rates were not sufficient to firmly establish the simultaneously observed NO_x concentrations. In addition, low concentration ratios of [HNO₃]/[NO_x] imply that the photochemical production of NO_x within the snow pack can influence surface NO_x mixing ratios in Antarctica. Alternate measurements of PAN mixing ratios at two different heights above the snow surface were performed to derive fluxes between the lower troposphere and the underlying snow pack using calculated friction velocities. Most of the concentration differences were below the precision of the measurements. Therefore, only an upper limit for the PAN flux of ±1×10¹³ molecules m⁻² s⁻¹ without a predominant direction can be estimated. However, PAN fluxes below this limit can still influence both the transfer of nitrogen compounds between atmosphere and ice, and the PAN budget in higher southern latitudes.     

ASBR处理高浓度悬浮固体废物的工艺特性

在水力停留时间(HRT)分别为20、10、7.5、5d的条件下,进行了中温、高温厌氧序批式反应器(ASBR)处理热水解污泥的试验,在此基础上总结了ASBR处理高浓度悬浮固体废物的工艺特性.ASBR可以有效积累悬浮固体从而保持较高的固体浓度,但ASBR存在一“临界点”,即最大积累悬浮固体的能力,超过此临界点,反应器运行不稳.在稳态运行条件下,ASBR能保持较高固体停留时间(SRT)和微生物平均细胞停留时间(MCRT),在处理热水解污泥时,SRT和MCRT分别是水力停留时间(HRT)的2.53～3.73倍、2.03～3.14倍.因此,与传统的连续流搅拌反应器(CSTR)相比,ASBR的处理效率提高7.13%～34.68%.     

水、氮控制对短花针茅草原气体交换的影响

随着对气候变化日趋关注,人们对生态系统气体交换及其主要影响因素进行了大量研究。短花针茅草原作为荒漠草原的典型代表,是亚洲特有的一种草原类型,是最干旱的草原类型,生态环境异常严酷,系统极度脆弱,稳定性差,在自然和人为干扰下极易退化。以短花针茅（Stipa breviflora）草原为研究对象,通过控制降雨量以及氮素添加对生态系统气体交换进行监测,研究气体交换对降雨量和氮素添加的响应过程,揭示降雨量和氮素添加对生态系统气体交换的影响作用。该文在2012年自然条件下,采用自动CO2通量系统（Li-6400, Li-COR, Lincoln, NE, USA）野外测定短花针茅（Stipa breviflora）草原生态系统气体交换数据,比较研究了增雨施肥（WN）、增雨不施肥（W）、减雨施肥（RN）、减雨不施肥（R）、单独施肥（N）、自然状况（CK）条件下2012年气体交换变化规律。结果表明：整个生长季生态系统净 CO2交换（NEE）、总的生态系统生产力（GEP）、生态系统呼吸值（ER）都呈先升高后降低的趋势,并在生长旺盛期（8月）达到最大值。NEE在N、W处理下有升高,其他处理都降低。ER在N、WN处理下都有升高,其他处理都降低。GEP在W、N、WN处理下都有升高,其他处理都降低。NEE、ER、GEP都是在N处理中达到最大值。     

热带亚热带土壤氮素反硝化研究进展

热带亚热带独特的土壤性质可能使得反硝化机理有别于温带土壤.文章综述了热带亚热带地区土壤氮素生物反硝化的研究进展,试图更好地了解该地区土壤反硝化在全球氮（N）循环以及在全球环境变化和生态系统响应互作中的角色.热带亚热带土壤反硝化强度普遍较温带地区弱,且随着土地利用方式和耕作管理措施的不同而呈现较大的时空变异性.影响土壤水分状况和土壤碳（C）、N 转化特性和速率的因素即为区域和农田尺度上的反硝化影响因素.湿润型热带亚热带土壤由于含有丰富的氧化物而致使土壤氧化还原势较高,这也是导致该地区土壤反硝化势较温带地区较低的关键土壤因素之-.然而土壤pH 值不是该地区土壤反硝化势较低的主要限制因素.有机C 矿化过程较土壤全氮含量和土壤C/N 比在决定湿润型亚热带土壤反硝化势方面更为重要.愈来愈多的证据表明热带亚热带土壤反硝化的生态环境效应不同于温带地区,热带亚热带地区土壤反硝化对全球变暖的贡献应综合考虑其对其它温室气体（如CH4,CO2）排放和氮沉降的影响.热带亚热带土壤生态系统具有-些防止土壤氮素反硝化损失的机制和保氮策略.然而,热带亚热带生态系统对全球变化的响应机制及其生物地球化学调控机制仍然不清楚,这些研究对于反硝化和其它同时发生的氮转化过程模型的精确构建至关重要.     

Seasonal variations in leaf capturing of particulate matter, surface wettability and micromorphology in urban tree species

The seasonal changes in leaf particulate matter (PM) accumulation, surface wettability and micromorphology in urban tree species, including Sophora japonica (S. japonica), Platanus acerifolia (P. acerifolia) and Cedrus deodara (C. deodara), were studied during a single growing season. The three species showed distinct seasonal trends in PM accumulation, increasing from spring to autumn (or winter) even during the rainy season, but at different rates. During the study, the leaf PM retention amount of P. acerifolia, a species with ridged leaf surfaces, was significantly higher than that of S. japonica and C. deodara, species with waxy leaf surfaces. The contact angles of water droplets on leaves decreased with leaf age except on the abaxial surface of S. japonica, which remained non-wettable or highly non-wettable throughout the growing season; the decrease in the contact angle on adaxial surface of S. japonica was greater when compared with P. acerifolia and C. deodara. A significant and negative relationship existed between leaf PM retention amounts and contact angles on adaxial surface of leaves of all three species. The increase in wettability, probably caused when epicuticular wax was destroyed by mechanical and chemical abrasion, seemed to be the main factor leading to seasonal variations in leaf PM accumulation.     

Effects of hydraulic retention time on nitrification activities and population dynamics of a conventional activated sludge system

The effects of hydraulic retention time (HRT) on the nitrification activities and population dynamics of a conventional activated sludge system fed with synthetic inorganic wastewater were investigated over a period of 260 days. When the HRT was gradually decreased from 30 to 5 h, the specific ammonium-oxidizing rates (SAOR) varied between 0.32 and 0.45 kg NH4+-N (kg mixed liquor suspended solids (MLSS)·d)^-1, and the specific nitrate-forming rates (SNFR) increased from 0.11 to 0.50 kg NO3--N (kg MLSS·d)^-1, showing that the decrease in HRT led to a significant increase in the nitrite oxidation activity. According to fluorescence in situ hybridization (FISH) analysis results, the proportion of ammonia-oxidizing bacteria (AOBs) among the total bacteria decreased from 33% to 15% with the decrease in HRT, whereas the fraction of nitrite-oxidizing bacteria (NOBs), particularly the fast-growing Nitrobacter sp., increased significantly (from 4% to 15% for NOBs and from 1.5% to 10.6% for Nitrobacter sp.) with the decrease in HRT, which was in accordance with the changes in SNFR. A short HRT favored the relative growth of NOBs, particularly the fast-growing Nitrobacter sp., in the conventional activated sludge system.     

HRT对一体式PTFE膜生物反应器运行效果的影响

针对垃圾渗滤液高COD、高NH4-N,低生化性的特点,开发UASB/缺氧/好氧-膜生物反应器组合处理工艺.在不同水力停留时间(HRT)下,考察了系统对污染物去除效果及其膜污染特性.结果表明,在不同的HRT条件下,UASB/缺氧/好氧-膜生物反应器组合工艺处理垃圾渗滤液出水水质良好且稳定.出水COD除率随HRT的升高先增加后降低,且HRT为12.8h时达到最大值94.96%;系统对NH4-N的平均去除率随HRT的延长而升高; 膜污染实验结果显示: 较低的HRT条件下意味着膜通量较高,会加剧膜污染进程.通过实验得出结论当HRT=15h时,对膜污染的控制最为有利.对膜进行清洗,并进行扫描电镜分析.分析结果显示凝胶层的形成是膜透水性下降的主要原因.     

铁氧体对活性污泥法处理生活污水的强化作用

为了提高活性污泥法处理生活污水的效率,采用铁氧体与生物法相结合方式处理生活污水。在生物反应器中投加磁化后的铁氧体粉末,在一定条件下驯化活性污泥。通过试验,得出了铁氧体的最佳投加量为375 mg/L。同普通活性污泥法相比,投加了375 mg/L铁氧体粉末的活性污泥对生活污水中COD和NH3-N的去除率分别提高了4.7%和26.5%;在各自的最佳运行条件下,投加铁氧体后反应器的水力停留时间缩短1 h。