朝鲜族的迁入和东北水田的开发

文章概述了我国朝鲜族的渊源。十八世纪生存不下去的朝鲜边民为了活命不顾东北边疆的封禁纷纷潜越到我国东北地区居住,开荒种地,成为我国大家族的一部分。与我国满、汉等少数民族和睦相处,探索水稻种植,兴修水利,改良种子和工具,共同建设我国东北地区。开辟了我国东北地区水稻种植的新天地,推动了东北地区农业经济的发展。

近代朝鲜垦民移居东北与水田开发

清末民初,大批朝鲜垦民陆续移居中国东北地区。本文依据相关史料,阐述了朝鲜移民迁入东北的历史背景、阶段过程、迁入方式、垦居区域等情况,并对朝鲜移民对开拓东北边疆、特别是水田开发的开创性劳动和历史贡献做出积极评价。

文化视野下的东北水田开发与朝鲜族的民族交往

清末民初,朝鲜北部地区的贫苦农民不断跨境迁入我国东北,迁居于此的朝鲜移民开始试种水田农业,从而拉开了中国东北地区水田耕作的序幕,为中国东北地区农业经济的发展做出了重大贡献。虽然挖掘水渠、引水耕作过程存在或者引发矛盾和冲突,但是在历史演变过程中相互学习水田开发技术、共同劳作是占据主导,成就东北水田享誉全国乃至全世界的美名是朝鲜移民与中国东北地区其他民族共同努力的结果,也是各民族团结、奋斗的见证。本文将从文化的视角解读朝鲜移民在开发东北水田过程中与其他民族相互交流,从而促进东北地区各民族的交往。

Greenhouse Gas Emissions from Northeast China Rice Fields in Fallow Season

CH4, N2O and CO2 emissions from northeast Chinese rice fields were measured in the fallow season （November to March） to investigate the effects of freezing-thawing on the emissions. Both CH4 emission from and atmospheric CH4 oxidation by the soil occurred, but the flux was small. During the fallow season, rice fields acted as a minor source of atmospheric CH4, which accounted for about 1% of the CH4 emission during the rice growing period. The field was also a substantial source of atmospheric N20, which ranged between 40 to 77 mg m-2 and eu=counted for 40%-50% of the annual N20 emission. The largest N20 flux was observed in the thawing period during the fallow season. Laboratory incubation tests showed that the largest N20 flux came from the release of N20 trapped in frozen soil. Tillage and rice straw application （either mulched on the soil surface or incorporated in the soil） stimulated the CH4 and CO2 emissions during the fallow season, but only straw application stimulated N2O emission substantially.

Physico-chemical and elemental investigation of aqueous leaching of high sulfur coal and mine overburden from Ledo coalfield of Northeast India

Acid mine drainage （AMD） is one of the major problems in high sulfur coal mining areas generating acidic water. The acidic mine water generated contain hazardous elements in varying concentrations. The Northeastern Indian coalfield produces considerable amounts of AMD. The AMD and metal leaching from coal and mine over burden （OB） are the two important naturally occurring processes. In order to know the AMD potential, the aqueous leaching experiment of a few coal and OB samples from the Ledo colliery of the Northeastern coalfield, Mergherita （India）, at different time periods （1, 3, 5, and 8 h） and at different temperatures （25, 45, 65, and 90℃） were performed in the laboratory. The physico- chemical analysis of the aqueous leachates shows the pH, electrical conductivity （EC）, and total dissolved solid （TDS） in the range of 1.62-3.52, 106-2006 μs/cm, and 106-1003 ppm for the raw coal samples respectively. The OB samples produced pH, EC, and TDS in the range of 3.68-6.92, 48.6-480 μs/cm, and 69.5-240 ppm respectively. From the study, it was revealed that the concentrations of major （Si, A1, K, Na, Fe, Ca, Mg）, minor （Mn） and trace/hazardous elements （As, Ba, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se, Zn） considerably change with leaching time as well as with leaching temperature. Out of these elements As, Cd, Hg, Pb, Cr, and Se are of greater environmental importance. Alteration of the physico-chemical structure of the coal and OB samples resulting from leaching was also studied by field emission scanning electron microscope- energy-dispersive X-ray spectroscopy method. The release of the potentially hazardous elements from the raw coal and OB during leaching time periods to the leachates was detected by inductively coupled plasma-atomic emission spectroscopy and ion-chromatographic analyses. The major minerals found in coal and OB are quartz （SiO2）, pyrite （FeS2）, hematite, marcasite, and kaolinite. The association of different functional groups in minerals and their mode of association were studied by Fourier-transform infrared spectroscopy and X-ray diffraction analytical techniques. The present laboratory study will be useful in relating the characteristics of aqueous leaching from coal and mine OB with the natural weathering condition at the coal mine area.

Field Capacity in Black Soil Region, Northeast China

In this work, 23 black soil profiles were surveyed and 113 soil samples were collected to determine the field capacity (FC) of the black soil in Northeast China. The effectiveness of three methods measuring FC, the Wilcox method (WM), the undisturbed soil pressure plate method (PUM) and the air-dried sieved soil pressure plate method (PDM) were compared to select a suitable laboratory measurement method. Results show that the FC values measured by PDM are greater than those measured by PUM, and the values measured by PUM are greater than those measured by WM. PUM is more suitable for the determination of FC in the study area. One regression equation between PUM and PDM has been established through which undisturbed soil can be replaced by air-dried sieved soil, which is easier to get, to measure FC. FCs vary from 23.50% to 37.00%, with an average of 31.65%, which differ greatly among the 23 black soil profiles. FC is found to be significantly positively correlated with the silt content, clay content and bulk density of the soil, but significantly negatively correlated with the sand content. An empirical pedotransfer function is established to estimate the FC using available soil physical and chemical properties.

Internal thermal origin mechanism of Karstic collapse column with no smoothly extrinsic cycle

Huainan coal field as main object,investigation of Karstic hydrogeological con- ditions were developed in Huainan structureal unit,and the basic conditions,features and rules of Karstic growth were summarized.Geology background and causes of Karstic col- lapse columns were analyzed.Combined with ancient physiognomy,environment and li- tho-facies features.After studying synthetically Karstic collapse columns,shape of col- lapse body,filling feature,hydrodynamic condition and agglutinate material in Huainan area,considering mine hydrogeological conditions of Xuhuai coal field and referenced Karstic collapse columns characters of other mines in North China,the internal thermal origin theory is elementarily formed for Karstic collapse columns extrinsic cycle can not operate smoothly.Finaly,three aspects including distributing features of different kinds of Karstic collapse columns in north China type coal field,conditions of Karstic collapse col- umns origined from internal thermal with no smoothly extrinsic cycle,mechanics of causes were analyzed and demonstrated.

Narrow distribution of cyanophage psbA genes observed in two paddy waters of Northeast China by an incubation experiment

Dear Editor,Cyanophages are viruses that infect cyanobacteria.They play an important role in shaping the genetic and functional diversity of themselves and their hosts through genetic exchange and shuffling（Lindell et al.,2005;Singh et al.,2012）.