A Comparative Study of Pollutant Removal Stability in Hybrid Wetland Columns     

Tanveer Ferdous Saeed 《湿地科学》2012,10(2):142-148

This study investigated the effects of two alternative substrates(wood mulch and zeolite) on the performance of three laboratory-scale hybrid wetland systems that had identical system components and configurations.Each system consisted of a vertical flow(VF) wetland column,followed by a horizontal flow(HF) column and a vertical flow column.The substrates employed were wood mulch,gravel and zeolite,and Phragmites australis were planted in each column.The systems received synthetic wastewater,with pollutant loadings in the range of 8.5-38.0 g/(m2·d) total nitrogen(TN) and 4.0-46.4 g/(m2·d) biological oxygen demand(BOD5).Wood mulch and zeolite substrates showed higher efficiencies in terms of removing nitrogenous compounds and biodegradable organics.The supply of organic carbon from the organic mulch substrates enhanced denitrification,while adsorption of influent ammoniacal nitrogen(NH4-N) in zeolite played a major role in the removal of nitrogenous species in the wetland columns.Overall,the average percentage removals of TN and BOD5 reached >66% and >96% respectively,indicating stable performances by the hybrid wetland systems under the experimental loading ranges.Mathematical models were developed,based on the combination of Monod kinetics and continuously-stirred tank reactor(CSTR) flow patterns to describe the degradation of nitrogenous compounds.Predictions by the models closely matched the experimental data,indicating the validity and potential application of Monod kinetics in the modelling and design of treatment wetlands.  相似文献   

Methods for extraction of microorganism DNA from glacier surface snow     

PeiYing Yan  ShuGui Hou  Tuo Chen  ShuHong Zhang  WeiJun Sun 《寒旱区科学》2012,4(6):0484-0489

In order to thoroughly investigate the diversity of glacier microorganisms, four DNA extraction methods with different lysis patterns were tested and two screened methods (the Bosshard-Bano method and the Zhou method) were optimized for the most effective form of the filter membrane (cut vs. uncut), the DNA extraction method, and the precipitation method. The two optimized methods were then compared with the commercial Mo-Bio DNA extraction kit, and the results showed that the kit was generally suitable for extraction of microorganism DNA from glacier surface snow. Procedurally, it was found that a modified Bosshard- Bano method (i.e., cutting the filter membrane into pieces, using a specific lysis pattern [lysozyme (5 mg/mL)-protease K (1 mg/mL)-CTAB (1%)-SDS (1%)], performing the extraction only once by chloroform-isoamyl alcohol (24:1), and conducting DNA precipitation by pure ethanol) was also an effective and less expensive method for extraction of microorganism DNA from glacier surface snow.  相似文献   

An Observational Analysis of a Derecho in South China          下载免费PDF全文

XIA Rudi  WANG Donghai  SUN Jianhu  WANG Gaili  XIA Guancong 《Acta Meteorologica Sinica》2012,26(6):773-787

Derechos occur frequently in Europe and the United States, but reports of derechos in China are scarce. In this paper, radar, satellite, and surface observation data are used to analyze a derecho event in South China on 17 April 2011. A derecho-producing mesoscale convective system formed in an environment with medium convective available energy, strong vertical wind shear, and a dry layer in the middle troposphere, and progressed southward in tandem with a front and a surface wind convergence line. The windstorm can be divided into two stages according to differences in the characteristics of the radar echo and the causes of the gale. One stage was a supercell stage, in which the sinking rear inflow of a high-precipitation supercell with a bow-shaped radar echo induced a Fujita F0 class gale. The other stage was a non-supercell stage (the echo was sequentially kidney-shaped, foot-shaped, and an ordinary single cell), in which downbursts induced a gale in Fujita F1 class. This derecho event had many similarities with derechos observed in western countries. For example, the windstorm was perpendicular to the mean flow, the gale was located in the bulging portion of the bow echo, and the derecho moved southward along with the surface front. Some differences were observed as well. The synoptic-scale forcing was weak in the absence of an advancing high-amplitude midlevel trough and an accompanying strong surface cyclone; however, the vertical wind shear was very strong, a characteristic typical of derechos associated with strong synoptic-scale forcing. Extremely high values of convective available potential energy and downdraft convective available potential energy have previously been considered necessary to the formation of weak-forcing archetype and hybrid derechos; however, these values were much less than 2000 J during this derecho event.  相似文献   

Changes in soil organic carbon stocks as affected by cropping systems and cropping duration in China’s paddy fields: a meta-analysis   总被引：4，自引：0，他引：4  

Shan Huang  Yanni Sun  Weijian Zhang 《Climatic change》2012,112(3-4):847-858

Great uncertainties remain in the impact of cropping systems on soil organic carbon (SOC) stocks in paddy fields that hold a large potential for carbon (C) sequestration. In this study, a meta-analysis was performed to examine trends on SOC stocks in unfertilized and fertilized fields from three of the most common rice cropping systems in China. Results showed that rice cropping without any nutrient application (Control) significantly increased SOC stocks by 9% compared to the initial level in double rice cropping systems (DR), whereas no significant effects were observed in single rice cropping systems (SR) and rice-upland crop rotation systems (RU). Paddy soils sequestered C in all the three cropping systems under inorganic NPK fertilization, and the magnitude of the increase in SOC stocks was in the order DR > RU > SR. Soil C stocks increased with the increasing cropping duration. Continuous rice cropping for more than 20?years led to average SOC gains of 15% and 23% in the control and NPK treatments, respectively. Furthermore, it seems that C sequestration was still occurring in the longest fields from the included studies. Thus, no SOC saturation trend was found over the investigated cropping duration. However, the negative relationship between SOC changes and their initial C stocks suggests indirectly the possibility of SOC saturation in paddy fields.  相似文献   

内蒙古自治区主要城市空气质量状况分析   总被引：1，自引：0，他引：1  

刘克利  王旭东  孙红斌 《内蒙古气象》2012,(6):18-20

文章利用呼和浩特市、包头市、乌海市、赤峰市、东胜区2007年1月1日到2011年12月31日5a空气主要污染物SO2、NO2、PM10浓度资料,统计分析了各城区主要污染物的分布特征,得到:⑴总体来看,乌海市空气质量较差,其次是包头市,东胜区最好;⑵PM10浓度值变化幅度最大,日最大值均出现在3—5月的沙尘日中,SO2最大值都出现在冬季采暖期;⑶各地均是12月出现污染日数最多,其次是1月;⑷从2007年开始,空气质量状况逐年好转。  相似文献   

拉萨紫外辐射特征分析及估算公式的建立   总被引：2，自引：1，他引：1  

张兴华  胡波  王跃思  张武  何永涛  孙维 《大气科学》2012,36(4):744-754

本文利用2005~2010年的辐射观测资料对拉萨地区紫外辐射的时间变化特征及紫外辐射与总辐射比值的变化特征进行了分析,结果表明,紫外辐射与太阳总辐射的变化规律基本一致,日变化表现为正午大、早晚小;季变化特征是夏季6月最大,冬季1月最小.紫外辐射日累积值6年平均为0.87 MJ·m-2·d-1;紫外辐射有逐年递减的趋势.紫外辐射与总辐射比值也存在着明显日变化,表现为正午大、早晚小的规律;其季节变化也是夏季最大,冬季最小.紫外辐射与总辐射比值6年平均为0.0418;紫外辐射与总辐射比值也呈现逐年递减的趋势.利用2010年大气质量数和晴空指数,建立了适合于拉萨紫外辐射估量的公式,估算值的瞬时值与观测值的平均相对误差最大为8.66%,紫外辐射日累积重构值与观测值平均相对误差仅为5.5%.  相似文献   

西藏地区雷暴与大气热源关系研究     

朱克云  孙照渤  张琪  任景轩 《大气科学》2012,36(6):1093-1100

利用1979～2008年NCEP/NCAR全球再分析月平均资料和雷暴记录资料, 运用相关分析和合成分析等方法分别对西藏地区大气热源和雷暴日数的关系以及热源强弱不同时期雷暴日数变化特征进行了分析。结果表明, 大气热源与雷暴日数存在着明显的正相关关系, 月相关系数高达0.86。在雷暴高发区的那曲东部、拉萨、日喀则中部、山南地区东北部和林芝地区西北部, 相关系数均超过了0.4。进一步分析表明, 当大气热源强值年时, 整个日喀则地区、拉萨地区、山南地区、那曲中西部和东部地区以及昌都地区中西部, 雷暴日数是偏多的。当大气热源偏弱时, 雷暴日数在日喀则中部地区减少最为明显, 其次在日喀则南木林县东北部和林芝西北部地区。  相似文献   

天津武清地区云凝结核变化特征     

王婷婷  孙俊英  沈小静  邓兆泽  张养梅  安林昌  张晓春  颜鹏  梁文德  陈丽丽 《气象科技》2012,40(3):466-473

利用2009年11—12月在天津武清气象局测量的云凝结核(CCN:Cloud Condensation Nuclei)浓度资料以及气溶胶数谱分布的观测资料,分析了武清地区在不同过饱和度(0.1%～1.0%)下云凝结核浓度及活化率的变化特征。结果表明:武清地区冬季CCN数浓度变化范围很大,过饱和度1%时,浓度变化范围为4000～32000cm-3,且浓度受风速影响明显,风速2级以下CCN数浓度很高,过饱和度1%时,其平均浓度可达16000cm-3,但对于4级风速以上CCN平均浓度为4000cm-3左右;在过饱和度0.1%～0.4%间CCN浓度变化较大,过饱和度每增加0.1%,CCN浓度增加值平均约为过饱和度0.4%～1.0%间浓度增量的5倍。低过饱和度(0.1%、0.2%)下,活化率受风速影响明显,1级风速下的CCN活化率约为4级风速下的3倍,但在过饱和度1%时活化率则相差不大。CCN浓度的日变化呈双峰型,峰值时刻为北京时间08:00和18:00左右,活化率的日变化则呈双谷型,这主要是受局地排放影响的结果。利用指数函数拟合各风速下CCN浓度过饱和度谱,表明该地谱型为典型的大陆型。  相似文献   

江苏夏季气温异常的时空变化特征   总被引：7，自引：4，他引：3  

孙燕  张秀丽  唐红昇  尹东屏 《气象科学》2009,29(1):133-137

利用中国160气象观测站1951-2005 年和江苏省59气象观测站1961-2004年的月平均气温资料, 在分析江苏气温变化的季节-年际变化特征的基础上, 重点分析了江苏夏季气温的年际、年代际变化的时间和空间特征.发现:江苏夏季气温1970s到1990s前期基本上处在一个偏凉期,1960s及1990s中后期以后基本上处在一个偏热期;江苏夏季气温异常存在显著的准6 a、准9 a的年际周期和以16 a为中心的年代际周期;江苏夏季气温趋势自西北向东南呈现正负正的位相分布特点,即江苏西北部和东南部地区夏季气温呈现升高的趋势,其它地区呈现降低的趋势.  相似文献   

RegCM3对山东夏季气候高分辨率模拟   总被引：1，自引：1，他引：0  

张可欣   孙成武 《气象科学》2009,29(4):490-497

利用区域气候模式RegCM3及NCEP/DOE再分析资料,对山东地区1985-2000年夏季区域气候变化进行了高分辨率(20 km)的数值模拟试验.通过对模拟结果和山东地区较密集的观测资料的比较分析,检验了模式在该地区的模拟能力.结果表明:(1)区域气候模式RegCM3能够合理地模拟出山东区域中高层的主要环流特征;(2)数值模拟能够合理再现山东地区16 a夏季平均降水南高北低和地面气温西高东低的主要分布特征.同时也能够合理地模拟出1990和1998年山东地区夏季强降水的主要特征,以及1992和1999年的干旱;(3) 模式结果较好地反映了1985-2000年16 a夏季山东地区降水和地面气温变率的主要特征.  相似文献