检索结果-南通市图书馆

spatial and Temporal distributions of Soil Organic Matter in the Mixed Plantations of Alder and Cypress in the Hilly Areas of Central Sichuan Basin

在线全文

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural Sciences 2006年第4期11卷 1021-1027页

作者： WU Pengfei ZHU BO YANG Yuanli WANG Xiaoguo Institute of Mountain Hazards and Environment Chinese Academy ofSciences Chengdu 610041 Sichuan China Graduate University of Chinese Academy of Sciences Beijing 100049China College of Environmental Engineering Sichuan Agricultural UniversityYa＇an 625014 Sichuan China

The investigation was conducted on the spatial and temporal distributions of soil organic mater （SOM） in the mixed plantations of alder （Aluns crernastogyne） and cypress （Cupressus funebris ）（MPAC）, which distributed in the hilly areas of central Sichuan Basin （HACSB）. The results show that：（1） the spatial distribution of SOM among different sites at the same age are not significant before 15-year-old, but significant at 20-year-old, and not significant again after 25-year-old; （2） the SOM contents in 0-15 cm and 15-30 cm layers increase sharply from 10- to 15-year-old, and decline gradually from 15- to 30- year-old; the SOM contents of the 30-year-old PCP were 80. 38% and 78.42% higher than that of the 10-year-old, but 29.16% and 53.37% lower than that of 15-year-old in the 0-15 cm and 15-30 cm layers, respectively. The decrease of SOM contents would lead to the degradation of soil fertility and the decline of forest productivity.

关键词： hilly areas of central Sichuan mixed plantations of alder and cypress soil organic matter spatial distributions temporal dynamics

Differences in distributions, assembly mechanisms, and putative interactions of AOB and NOB at a large spatial scale

在线全文

学校读者我要写书评

暂无评论

Frontiers of Environmental Science & Engineering 2023年第10期17卷 55-64页

作者： Bing Zhang Chenxiang Sun Huimin Lin Wei Liu Wentao Qin Tan Chen Ting Yang Xianghua Wen College of Life and Environmental Sciences Minzu University of ChinaBeijing 100081China Environmental Simulation and Pollution Control State Key Joint Laboratory School of EnvironmentTsinghua UniversityBeijing 100084China Institute of Plant Protection Beijing Academy of Agriculture and Forestry SciencesBeijing 100097China

Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) play crucial roles in removing nitrogen from sewage in wastewater treatment plants (WWTPs) to protect water resources. However, the differences in ecological properties and putative interactions of AOB and NOB in WWTPs at a large spatial scale remain unclear. Hence, 132 activated sludge (AS) samples collected from 11 cities across China were studied by utilizing 16S rRNA gene sequencing technology. Results indicated that Nitrosomonas and Nitrosospira accounted for similar ratios of the AOB community and might play nearly equal roles in ammonia oxidation in AS. However, Nitrospira greatly outnumbered other NOB genera, with proportions varying from 94.7% to 99.9% of the NOB community in all WWTPs. Similar compositions and, hence, a low distance–decay turnover rate of NOB (0.035) across China were observed. This scenario might have partly resulted from the high proportions of homogenizing dispersal (~13%). Additionally, drift presented dominant roles in AOB and NOB assembling mechanisms (85.2% and 81.6% for AOB and NOB, respectively). The partial Mantel test illustrated that sludge retention time and temperature were the primary environmental factors affecting AOB and NOB communities. Network results showed that NOB played a leading role in maintaining module structures and node connections in AS. Moreover, most links between NOB and other microorganisms were positive, indicating that NOB were involved in complex symbioses with bacteria in AS.

关键词： Activated sludge spatial distributions Microbial assembly Co-occurrence patterns Nitrifying bacteria

Determination and ecological risk assessment of arsenic and mercury in sediments from the Changjiang River Estuary and adjacent East China Sea

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2021年第4期40卷 32-38页

作者： Yu'na Zhang Qianwen Wang Central Laboratory Qingdao Agricultural UniversityQingdao 266109China

Arsenic(As)and mercury(Hg)are pollutants presented in marine environment.A process of atomic fluorescence spectrometry was proposed for the simultaneous determination of As and Hg in marine sediment samples(n=38)collected from the Changjiang River Estuary and adjacent East China *** proposed method used an optimized pretreatment procedure in an aqua regia–H_(2)O digestion *** of As and Hg increased to97%and 98%,respectively,with suitable precisions(2.7%–4.1%)under optimized process *** and Hg were widely presented in these samples,with the ranges of content values were 2.39–8.77μg/g for As and48.03–410.8 ng/g for *** indicate that anthropogenic factors strongly influence the abundances of As and Hg in investigated *** preliminary environmental risk assessment was investigated using the Igeoaccumulation index(Igeo)and anthropogenic contribution rate(M).Findings reveal that Hg demonstrates a strong ecological risk(with average values of 1.3 and 72%for Igeo and M,respectively)in the sediments from the Changjiang River Estuary and adjacent East China ***,Hg should be considered in future investigations.

关键词： arsenic mercury marine sediment spatial distributions ecological risk

Mean properties of mesoscale eddies in the Kuroshio recirculation region

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Oceanology and Limnology 2014年第3期32卷 681-702页

作者：马利斌王强 Key Laboratory of Ocean Circulation and Waves Institute of OceanologyChinese Academy of Sciences University of Chinese Academy of Sciences

Using a 19-year altimetric dataset, the mean properties and spatiotemporal variations of eddies in the Kuroshio recirculation region are examined. A total of 2 001 cyclonic tracks and 1 847 anticyclonic tracks were identifi ed using a geometry-based eddy detection method. The mean radius was 57 km for cyclonic eddies and was 61 km for anticyclonic eddies, respectively, and the mean lifetime was about 10 weeks for both type eddies. There were asymmetric spatial distributions for eddy generation and eddy termination, which were domain-dependent. Mean eddy generation rates were 2.0 per week for cyclonic eddies and were 1.9 per week for anticyclonic eddies. Both type eddies tended to deform during their lifetime and had different propagation characteristics, which mainly propagated westward and southwestward with velocities 4.0–9.9 cm/s, in the Kuroshio recirculation region. Further discussion illustrates that the eddy westward speed maybe infl uenced by the combined effect of vertical shear of horizontal currents and nonlinearity of eddy. To better understand the evolution of eddy tracks, a total of 134 long-lived tracks(lifetime ≥20 weeks) were examined. Comparison between short-span eddies(lifetime ≥4 weeks and <20 weeks) and long-lived eddies is also conducted and the result shows that the short-span and long-lived eddies have similar time evolution. Finally, eddy seasonal variations and interannual changes are discussed. Correlation analysis shows that eddy activity is sensitive to the wind stress curl and meridional gradient of sea surface temperature on interannual timescales. Besides, the strength and orientation of background fl ows also have impacts on the eddy genesis.

关键词： mesoscale eddies spatial distributions temporal variations potential factors

Characteristics of high arsenic groundwater in Hetao Basin,Inner Mongolia,northern China

在线全文

学校读者我要写书评

暂无评论

Research in Cold and Arid Regions 2015年第1期7卷 104-110页

作者： YangChun Zhu XueYong Zhao Min Chen YongQing Luo Xin Zhou Naiman Desertification Research Station Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Sciences

It is well known that the Hetao Basin is one of the most seriously arsenic-affected groundwater areas in China. In order to understand the characteristics of high arsenic （As） groundwater in the Basin, a brief overview of arsenic in groundwater follows. High arsenic in the Basin commonly occurs in shallow groundwater and the total arsenic concentrations range from 0.58 to 572 μg/L （average 99.73 μg/L）, exceeding the maximum mandated value of 10 μg/L for drinking water in China; As（III） is the predominant species. The regional distribution pattern of arsenic in the groundwater increases from south/southeast to north/northwest. Hangjinhouqi and Wuyuan counties are considered as the most seriously affected areas, with high incidences of endemic arsenicosie diseases in the Hetao Basin. High groundwater arsenic correlates with the increase of well depth. Previous studies proposed that groundwater arsenic in the Basin is mainly originated from desorption of some natural solid materials in the sediments, under reducing condition. Generally, reducing condition is believed to be the primary factor for arsenic releasing from the sediment to groundwater in the region. Under inorganic Or bacterial processes, Fe2O3 changes to FeS and arsenic adsorbed to Fe（OH）3 dissolves into groundwater, and As（V） is re- duced to As（W）. Besides, reducing environments, groundwater hydraulic gradients, organic matter, pH, evapotranspiration, and soil texture are presumed to be the predominant factors that control arsenic mobilization.

关键词： spatial distributions source reducing condition influencing factor

Simulation of astronomical solar radiation over Yellow River Basin based on DEM

在线全文

学校读者我要写书评

暂无评论

Journal of Geographical Sciences 2004年第1期14卷 63-69页

作者： QIUXinfa ZENGYan LIUChangming WUXianfeng Dept.ofGeography NanjingInstituteofMeteorologyNanjing210044China Inst.ofGeographicSciencesandNaturalResourcesResearch CASBeijing100101China Inst.ofEnvironmentalScience BeijingNormalUniversityBeijing100875China

Based on the developed distributed model for calculating astronomical solar radiation (ASR), monthly ASR with a resolution of 1 km×1 km for the rugged terrains of Yellow River Basin was calculated, with DEM data as the general characterization of terrain. This model gives an all-sided consideration on factors that influence the ASR. Results suggest that (1) Annual ASR has a progressive decrease trend from south to north; (2) the magnitude order of seasonal ASR is: summer>spring>autumn>winter; (3) topographical factors have robust effect on the spatial distribution of ASR, particularly in winter when a lower sun elevation angle exists; (4) the ASR of slopes with a sunny exposure is generally 2 or 3 times that of slopes with a shading exposure and the extreme difference of ASR for different terrains is over 10 times in January; (5) the spatial differences of ASR are relatively small in summer when a higher sun elevation angle exists and the extreme difference of ASR for different terrains is only 16% in July; and (6) the sequence of topographical influence strength is: winter>autumn>spring>summer.

关键词： astronomical solar radiation (ASR) rugged terrains spatial distributions digital elevation model (DEM)

Distribution of possible sunshine durations over rugged terrains of China

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2003年第10期 41-44+81页

作者： ZENG Yan 1, QIU Xinfa 2*, MIAO Qilong 2 and LIU Changming 1(1. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China 2. Department of Geography, Nanjing Institute of Meteorology, Nanjing 210044, China) Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Department of Geography Nanjing Institute of Meteorology Nanjing 210044 China

Based on the digital elevation model (DEM), a new model for calculating possible sunshine duration (PSD) is completely described. Using this model, monthly PSD with resolution of 1 km×1 km for the rugged topography of China is calculated. Results suggest that terrain has robust effect on PSD, particularly in winter when a lower sun elevation angle exists. Besides, the proposed model taking the DEM data as the input has an ability to process mass of data and is applicable to satellite image processing platforms or Geographic Information System (GIS). The PSD (in hours) is provided in the same way as other kinds of spatial information and can be employed as basic geographic data for relevant studies as well.

关键词： possible sunshine duration (PSD) rugged terrains spatial distributions digital elevation model (DEM).