广西武宣县盘龙铅锌矿床地质特征及控矿因素分析

盘龙铅锌矿位于广西大瑶山西侧铅锌铜多金属成矿带的南段,是广西近10年来发现的中型沉积-热卤水改造型铅锌矿床.矿体主要赋存于泥盆系下统上伦白云岩层间破碎带中,以似层状、透镜状产出为主,具有多层特点,围岩蚀变较弱.矿石中金属矿物以硫化物形式存在,方铅矿、闪锌矿与黄铁矿、重晶石等共生.泥盆系上伦白云岩渗透性较好,铅锌丰度值较高,是矿区最有利的赋矿层位.矿体在时间和空间上与燕山早期岩浆活动有一定关联.矿床明显受地层岩性、构造等因素的联合控制,是与沉积作用和岩浆活动有成因联系的铅锌矿床.     

Impact of stress and disturbance factors on the phytoplankton communities in Northeastern Brazil reservoir

The ecology of phytoplankton reservoir communities plays a pivotal role in their management and in the development of inland fisheries in the water scarce semi-arid regions of Rio Grande do Norte State, Brazil. The hydrological conditions characterizing these reservoirs include infrequent rainfall and high evaporative loses. The phytoplankton assemblages in tropical climate are structured primarily on dry and wet cycles, not the annual temperature and light regime. The purpose of the current study was to investigate the ecological aspects of phytoplankton communities from three reservoirs during the period of July 2003–June 2004, which include atypical summer rainfall and reservoir overflow. The environmental data broadly divided into two categories, stress factors and disturbance factors. The stress factors deals with the impact of high particulate organic matter and low dissolved oxygen concentrations and disturbance factors, linked to water level fluctuation through flushing and reservoir drawdown, and these events are associated with the phytoplankton assemblages. Results indicated that the three distinct hydroperiods determined the structure of phytoplankton and chlorophyll levels and limited the presence and relative abundance of cyanobacterial species. Phytoplankton succession accompanied changes in clear and turbid water phase represented by the alternate dominance between diatoms and chlorophytes. Inundation and complete filling of reservoir stimulated “s” and “r” strategists species (<20 um) of unicellular and some colonial members of chlorophytes and cryptomonads in highly turbid water environment, and “c” strategist species in rest of the wet period following disturbance gradients. Statistical analysis elicited a significant relationship between particulate organic matter and relative abundance of smaller chlorophytes, which was deemed as stress factor. The flushing and reservoir drawdown indicate disturbance gradient and as a consequence high diversity. Furthermore, a substantial reduction in chlorophyll levels was registered in turbid water phase is related to the reduction of light penetration and re-suspension of sediments. Considering these results, it can be suggested that the well-managed reservoir drawdown can possibly maintain an environment free of eutrophication and cyanobacterial dominance.     

Variations of phytoplankton productivity and biomass over an annual cycle in Saanich Inlet,a British Columbia fjord

Saanich Inlet is a highly productive temperate fjord with the capability to record inter-annual patterns of water-column primary production in undisturbed laminated sediments. We investigated spatial and temporal variations in primary productivity, total and size-fractionated phytoplankton chl a, dissolved nutrients, temperature and salinity at the head and mouth of Saanich Inlet from May 2005 to November 2006. New primary productivity was also measured from May to October 2006. During the growing season (spring, summer and fall), primary productivity was 1.5 times higher at the mouth than at the head of Saanich Inlet and, averaged across stations, total productivity was 460 g C m⁻² y⁻¹. Average new productivity was 53% and 58% of total primary productivity at the head and mouth of the inlet, respectively, and during the growing season micro-phytoplankton (>20 μm; mainly diatoms) was the most abundant size-class of phytoplankton. These rates of primary production are as high as or higher than those measured in other fjords, possibly because of a tidally-driven fortnightly gravity exchange that supplies nutrients to surface waters that enhance biological production when nutrients would otherwise be limiting. This exchange delivers nutrients at least as far inland as the head station, while nutrients associated with an eddy near the mouth may be the cause of even higher productivity there. We discuss the impact of these nutrient sources to Saanich Inlet on the records of paleoproduction generated from two Ocean Drilling Program cores extracted from this fjord, and suggest that the fortnightly exchange buffers variations in nutrient supply occurring on sub-decadal or decadal scales.     

Deterministic Seismic Scenarios for Imphal City

In this article, the spatial variation of ground motion in Imphal City has been estimated by the finite-fault seismological model coupled with site response analysis. The important seismic sources around Imphal City have been identified from the fault map and past seismicity data. The rock level acceleration time histories at Imphal City for the 1869 Cachar (M_w 7.5) earthquake and a hypothetical M_w 8.1 event in the Indo-Burma subduction zone have been estimated by a stochastic finite-fault model. Soil investigation data of 122 boreholes have been collected from several construction projects in Imphal City. Site response analysis has been carried out and the surface level ground motion has been determined for Imphal City for these two earthquake events. The results are presented in the form of peak ground acceleration (PGA) contour map. From the present study it has been ascertained that the maximum amplification for PGA over Imphal City is as high as 2.5. The obtained contour maps can serve as guidelines for identifying vulnerable areas and disaster mitigation in Imphal City.     

中国东北农业生产适应气候变化的行为经济学解释

利用调查问卷和入户访谈的方法,以中国东北地区11个调查点为研究区.对554户农户进行调查研究.从行为经济学的视角出发,把农业实践者的粮食种植行为作为一种农业经济行为,分析20世纪80年代气候变暖以来,农业实践者在农业种植决策中的行为过程及其与传统经济学理性行为之间的差异.结果显示,在不确定条件下,农业决策行为符合行为经济学的一般规律,在认知偏差和思维定式等因素的影响下,会系统地偏离传统经济学理论,产生非理性行为,从而导致适应与变化之间存在时滞现象:①受启发式认知偏向的影响,农业实践者在作物种类选择、种植计划制定和粮食出售时间确定等方面均表现为非理性的特点:②受中国具体国情和农业生产固有特点的影响,出于"保障生活能够继续"的考虑,农业实践者判断"获得"和"损失"的参照点通常很低,对作物品种选择的行为更倾向于保守.     

基于RITE模型的东北老工业基地信息化水平分析

基于改进的RITE模型选取15个指标,计算了1998-2005年间东北老工业基地与全国的信息化指数:对比了东北老工业基地与全国平均信息化进程发展差异;并利用Pearson相关分析法探讨了东北老工业基地信息化水平各影响因子对区域整体信息化水平的贡献差异.结果表明:与全国平均水平相比,东北老工业基地整体信息化水平较高,年均高出全国平均水平8.40%;但就区域内部而言,地区之间发展不平衡,其信息化水平强弱依次为辽宁省＞吉林省＞黑龙江省;对于信息化测度指标,信息装备率(r2=0.991)和通信主体水平(r2=0.981)是东北老工业基地整体信息化水平提升的主要驱动力;相反,信息量是阻碍东北老工业基地信息化水平提升主要因子(r2=0.753).     

东北地区农业应对气候变化的策略与措施分析

气候变化的影响与适应已经成为农业生产面临的现实而紧迫的问题。1956-2005年东北地区增温1.5℃,幅度明显高于全国平均水平,给作物生产带来复杂的影响。东北是重要的国家商品粮生产基地,对国家粮食安全起着重要作用。探讨区域层面上适应气候变化的能力建设更具有针对性和现实性。文章分析了近50 a来东北地区气候变化的主要表现及其对农业生产的影响;针对气候变化过程中人类活动对土地利用和温室气体的影响,提出了东北地区适应和减缓气候变化的策略和措施,强调在农业生态、水资源利用、环境保护等多方面综合开展工作,积极采取行动,最终达到维护气候环境、充分利用气候资源的目的,为东北粮食生产安全、农业可持续发展做出贡献。     

东北地区国土资源大调查区域重力和区域地球化学调查成果综述

自2000年以来,在提高了区域重力调查技术要求,更新了区域化探方法技术后,极大地提高了东北地区基础地质工作程度,发现了众多重力异常,圈定和推断了隐伏岩体、盆地和断裂构造.特别是区域化探,获得的地球化学异常更加丰富,真实地反映了地质规律,提供了较多的成矿远景区和找矿靶区,发现了众多矿产地.首次开展的多目标区域地球化学调查,查明了松辽平原土壤元素区域地球化学分布特征,证实了松辽平原土壤环境质量是优良的.这些成果为东北地区的地质工作提供了丰富的地球物理和地球化学基础信息.     

基于作物空间分配模型的东北三省春玉米时空分布特征

利用1980-2010 年东北三省分县玉米播种面积与产量统计、耕地分布、农业灌溉分布以及作物适宜性分布等多源数据,结合基于交叉信息熵原理的作物空间分配模型（Spatial Production Allocation Model,SPAM）,在5'×5'的像元尺度模拟了春玉米种植面积与产量的时空分布,并重点分析了两者在纬向、经向,以及高程上的时空变化规律。结果显示：（1）玉米种植面积在2000 年前向北扩展至北纬44°~48°间,2000 年后在中南部出现大规模发展（北纬42°~44°）,并进一步向东扩展至东经123°~127°间,同时还表现为向低海拔（高程100 m以下）和较高海拔（高程200~350 m）扩展的态势;（2）单产在纬向上的增加区主要集中在北纬42°~48°,经向上的单产增加则相对均匀,高程上单产提升区主要集中在海拔350 m以下。（3）像元内玉米种植比例整体上由中低种植比例为主逐步演变为中高比例占据主体,并且中高种植比例像元对应的玉米单产水平整体上较高,反映了市场经济驱动下的玉米种植集聚化和规模化的发展趋势。     

一次东北冷涡暴雨的水汽输送特征和位涡分析

通过对2010年7月27~29日吉林省一次较大范围的冷涡暴雨、大暴雨过程进行诊断分析,建立了此类暴雨的天气概念模型：200 hPa呈现“两脊一槽”型,高空急流呈辐散状位于吉林省上空,急流中心最大风速≥60 m/s;500 hPa东北冷涡强烈发展,鄂海阻高稳定维持是此次强降水发生的重要天气系统,中心最大风速≥20 m/s的偏西风急流带横穿吉林省中部;850 hPa风速≥12 m/s的3条急流带在吉林省中东部地区交汇,形成低层辐合、高层辐散的气旋性涡度柱,较强的垂直上升气柱一直向上伸展到500 hPa附近,极有利于对流的发展和强降水的维持。通过计算整层水汽通量与吉林省逐6 h平均降水量的相关矢量场,结果表明：偏西、偏南及偏北3条水汽通道在吉林省中南部汇集是此次强降水发生的重要条件,暴雨落区与整层水汽通量汇合区密切相关,水汽输送以经向(南北方)水汽流入为主。暴雨期间具有较好的动力、热力及能量条件,特别是湿对流有效位能明显偏强,强降水出现在对流有效位能 (CAPE)值由极大值开始下降的过程中。干侵入是激发冷涡发生、发展的动力条件之一,≥1 PVU(位涡单位)的高位涡舌在下降的过程中,同时南移,与中部地区强降水落区自北向南移动相吻合。