200 resultados para 7140-216
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对贵阳市区到农村地区的石生藓类氮含量进行了系统分析,并根据藓类氮含量(y,%)和大气氮沉降(x,kghm^-2a^-1)的平均定量关系(y=0.052x+0.7325)计算了各采样点的大气氮沉降值。贵阳地区大气氮沉降的变化范围为0.91~44.69kghm^-2a^-1,市区大气氮沉降最高平均(29.21±6.17)kghm^-2a^-1,主要来自城市废水NH3释放;最低平均(11.95±3.95)kghm^-2a^-1,出现在城市和农村的结合地带,主要原因在于来自市区的氮污染物减少、且大量分布了环城林带、农业活动相对较低;20km以外的农村地区大气氮沉降略微升高(平均(14.31±5.11)kghm^-2a^-1),主要反映了农业施肥导致NH3释放的增加。结果表明,石生藓类氮含量是一种经济可靠的大气氮沉降监测工具,能够较准确地量化大气氮沉降的水平,并为深入研究大气氮沉降的生态环境效应提供基础资料。
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矿床的开采和选冶,常常将其中重金属有毒元素释放到环境中,铅锌矿造成的环境污染尤为严重。贵州都匀牛角塘矿床是国内外少见的富镉锌矿床,其中镉高度富集。本文通过对通过对矿区水、土壤及植物的分析和调查,发现其中镉和锌均已远远超过国家标准,矿区周围环境已受到严重污染。研究表明矿床的表生风化作用是镉等重金属释放的主要途径之一,更重要的是矿山的采矿和选矿更加剧了其释放量,虽在目前人群中没有明显中毒现象,可能是由于矿床开采时间较短,Cd等重金属元素在人体中积累不多所致。但矿山环境污染是污染元素长期积累造成的结果,即使在矿山关闭十年、上百年甚至上千年时间内,矿山尾矿淋滤液对环境生态的影响依然存在。因此,在矿山开发过程中必须注意矿床中有用元素的综合利用和重视环境保护,防患于未然。特别是对这类富含有毒污染元素的金属矿山的开采更应如此。
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应用高精度离子探针锆石U—Pb测年方法,获得普朗斑岩铜矿床中3件矿化石英二长斑岩的锆石年龄分别为228.4-3Ma、226.3±2.8Ma、226±3Ma。锆石形态和铀钍参数均属典型的岩浆锆石特征,年龄值在误差范围内近似一致,表明形成矿化斑岩的中酸性岩浆从岩浆房快速上升侵位。结合前人已发表的矿化斑岩的黑云母Ar—Ar坪年龄及辉钼矿Re-Os同位素年龄等数据,推测普朗斑岩铜矿的岩浆-热液系统从岩浆侵入至矿化阶段的持续时间可能长达lOMa以上,主成矿期约为216~214Ma。从岩浆房分异出的富含成矿物质和挥发份的岩浆流体在相对较晚阶段对普朗复式岩体发生了强烈的蚀变作用并可能进一步萃取了岩体中的成矿物质。
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通过对地质样品中Mo同位素测试前的处理方法的比较,对传统的阴、阳离子树脂交换法进行了改进研究。经改进后的方法实用范围较宽,Mo的回收率达到97.49%±0.27%,Mo同位素质谱分析过程中可能的同重干扰元素Zr、Fe、Mn等的去除效果理想,其它金属元素的去除效果也较理想,且在阴离子交换柱洗脱Mo的过程中总计约需的提取液(盐酸和硝酸)体积只有75mL,只需文献报道用量的45%,从而减少了试剂对样品,特别是对低含量地质样品可能带来的潜在污染.
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重金属是指比重大于或等于5.0的金属。随着城市化在全球范围内的飞速发展,以及城市人口的不断增长,客观上需要增加对城市生态环境的了解,以及研究城市生态环境与人类健康之间的相互关系。 大气沉降包括干沉降与湿沉降,大气的干、湿沉降是大气化学、环境化学和生物地球化学研究的重要内容之一,在重金属循环中扮演着重要的角色。大气沉降对土壤重金属地球化学过程有着重要影响。因此,准确把握环境中重金属的主要来源、行为及归宿,对有效控制重金属的污染、保护人类健康提供科学依据具有非常重要的意义。城市土壤是城市生态环境的重要组成部分,对城市的可持续发展有着重要意义。在城市环境中,各种各样的人类活动将大量的重金属带人城市土壤中,造成这些元素在土壤中的积累,并通过大气、水体或食物链而直接或间接地威胁着人类的健康甚至生命。 本研究以贵阳为例,对环境中的重金属进行研究。系统研究了贵阳市大气颗粒物重金属含量与形态、雨水重金属的含量与季节变化及土壤重金属含量与形态。主要结果如下: 1 贵阳市的干、湿沉降与气象因子关系密切。随温度的升高,贵阳市TSP浓度下降;相对湿度与TSP呈负相关性;风速对贵阳市区的TSP浓度的影响主要表现为扩散和稀释作用,随风速的增加,贵阳TSP浓度降低;雨水对贵阳市大气总悬浮颗粒物的有明显的清除作用。随着风速的增加,贵阳市雨水中重金属含量降低;雨量与雨水中的Cd、Cr、Cu、Pb与Zn的含量均呈一定的负相关关系,总体趋势为当降雨量较大的时候,雨水中重金属的含量较低。 2 贵阳市大气颗粒物中重金属含量有明显季节变化规律。Cd、Cr、Pb和Zn冬季的含量明显高于其它季节,而春季和夏季颗粒物中重金属含量相对较低,冬季的浓度是夏季的1.8-4.6倍。同样,贵阳市雨水中Cr、Cu、Zn的最高浓度都出现在冬季,这与贵阳市在冬季大量使用燃煤来取暖的时段相符合。 3与其它城市相比,贵阳市大气颗粒物重金属污染比较严重。同样,与地表水国家标准值相比较,贵阳市大部分样品Cd、Cu、Pb与Zn明显超过地表水国家标准,雨水中Cd、Cu、Pb与Zn的平均值分别国家标准的为2.7、2.2、6.0和1.3倍。贵阳市表层土壤已受到重金属不同程度的污染。表层土壤Cd的平均含量为0.66mg/kg,Co的平均含量为17.31mg/kg,Cr的平均含量为82.91mg/kg,Cu的平均含量为52.20mg/kg,Ni的平均含量38.76mg/kg,Pb的平均含量为71.03 mg/kg,Zn的平均含量为216.05mg/kg。土壤Cd、Co、Cr、Cu、Ni、Pb和Zn的平均含量分别我国土壤元素的背景值的6.8倍、1.36倍、1.36倍、2.31倍、1.44倍、2.73倍与2.98倍,其中以Cd和Zn 积累较明显。 4对贵阳市大气颗粒物、土壤重金属形态分别进行分析,结果表明:大气颗粒物中Cd主要以环境可迁移态存在,占61.4%;Cr和Cu主要稳定态存在,二者对环境不会造成直接影响;Pb主要以环境可迁移态、碳酸盐和氧化物结合态存在;Zn主要以环境可迁移态存在。土壤中,除Cd以外,Co、Cr、Cu、Ni、Pb和Zn元素的酸可提取态在总的元素含量中所占比例较小,均小于总量的3.0%,而Cd的酸可提取态含量为23.3%。相反,除Cd以外,其它6种金属元素的残渣态含量都比较高,Zn为96.8%,Cr为92.2%,Cu为83.4%,Co为69.2%,Ni为57.4%,Pb为41.9%。 5 贵阳市土壤剖面重金属元素的分布比较混乱,没有规律性,底土层含量仍然很高。城市土壤受到人为因素等影响,已发生严重改变。土壤中有许多不同来源物质的混入,土壤剖面经常受到人为扰动,自然土壤发生层被破坏,导致许多土壤剖面上下土层没有发生学上的联系。
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苔藓植物由于具有特殊的形态结构和生物学性质而被广泛应用于环境变化和大气沉降的指示和监测,而稳定同位素(如13C、15N、34S)是辨识环境体系中物源走向以及研究植物和环境关系的可靠技术。本论文正是结合苔藓生物指示方法和稳定同位素示踪技术,开展了苔藓碳氮同位素指示环境条件和大气氮沉降的初步研究。通过不同环境条件下苔藓同位素的对比研究,揭示了苔藓碳氮同位素对环境因子和氮沉降变化的响应机制。进而应用石生苔藓碳氮元素含量和同位素,并结合光合色素含量等参数,对贵阳地区的大气氮沉降进行了详细研究,深化了苔藓同位素方法在环境监测和大气氮沉降研究中的应用,并为城市氮污染的防治提供了地球化学依据。获取了一些有意义的发现和创新点。 1. 不同生长条件下苔藓元素含量和同位素的变化及其意义 即使在同一地点,苔藓13C会由于水分条件和光照条件的差异而发生明显变化,而树冠对大气沉降物质的长期截留吸收会使下方苔藓氮硫含量偏低以及同位素偏负,其同位素效应还与树冠类型和树冠厚度有关。因此,应用苔藓元素含量和同位素指示区域环境和大气沉降时应尽量消除生境差异的影响,受生长条件影响或歪曲了的苔藓指示信息可能导致在解释环境变化和大气沉降时得出错误的结论,相对而言,开阔地的石生苔藓是较可靠的指示工具。利用同位素方法探讨苔藓记录信息的差异是本研究的创新点之一,目前国内外尚无相关的报道,这深化了苔藓碳氮同位素对环境条件和大气输入响应机制的认识,同时还为苔藓同位素研究大气沉降提供了采样指导。 2. 不同地区苔藓新老组织碳氮含量和同位素组成特征 贵阳市区苔藓碳含量高于贡嘎山地区,而13C明显偏负,表明城市苔藓受人为CO2排放的影响,而非污染区苔藓13C能够响应海拔和年均温度的差异。贵阳市区苔藓氮含量较高反映其氮沉降高于贡嘎山地区,明显偏负的15N值主要指示了城市废水氨释放的影响。不同地区苔藓新生组织的碳氮含量总体高于衰老组织,但同位素没有明显变化,反映了生理功能的衰退和部分元素向新生组织迁移会导致老组织碳氮含量降低,但不会明显改变其碳氮同位素记录,新组织氮含量较可靠地反映了氮沉降的水平(贵阳市约为30.18 kg/ha/yr,贡嘎山地区约为8.46 kg/ha/yr)。本研究扩展了苔藓同位素对不同地区环境因子和氮沉降差异的响应状况,并首次探讨了苔藓衰老对其碳氮含量和同位素记录的影响,为深入理解非维管植物衰老过程的碳氮同位素分馏奠定基础。 3. 贵阳地区大气氮沉降的空间分布 根据大气氮沉降和苔藓氮含量之间的定量关系(y=0.052x+0.7325),可以利用石生苔藓氮含量(0.85% ~ 2.97%)计算贵阳地区的大气氮沉降。贵阳地区的氮沉降(0.91 kg/ha/yr ~ 44.69 kg/ha/yr)总体已经超过最易受影响的陆地生态系统的氮沉降负荷值(5 kg/ha/yr ~ 10 kg/ha/yr),市区氮沉降平均值(29.21±6.17 kg/ha/yr)与前期监测值(30.18kg/ha/yr)基本一致,高于酸性针叶林和落叶林的氮沉降负荷值(15 kg/ha/yr ~ 20 kg/ha/yr)。而农村地区氮沉降平均值(14.31±5.11 kg/ha/yr)与贵州农村地区铵沉降的平均值(14.3 kg/ha/yr)吻合。本研究首次根据石生苔藓氮含量量化了氮沉降的水平和空间分布,对大气氮沉降生态环境影响的评价以及喀斯特地区脆弱生态系统的保护具有重要意义。 4. 贵阳地区大气氮沉降的主要来源和主要形态 贵阳地区石生苔藓15N值(-12.50‰ ~ -1.39‰)呈明显的双峰分布模式(-12‰ ~ -6‰和-5‰ ~ -2‰),表明该地区的氮沉降存在两个主要来源。市区明显偏负的苔藓15N值(平均-8.87±1.65‰,<5km; -8.59±2.28‰,5 km ~ 10km)主要反映城市废水和人畜排泄物NH3的影响,而往外到农村较高的苔藓15N值(平均-3.83±0.82‰ ~ -2.48±0.95‰,>15km)主要指示了农业NH3的贡献。根据市区苔藓和雨水15N值计算,市区氮沉降中铵态氮的贡献约占76%,硝态氮约为23%,贵阳地区的氮沉降以铵沉降为主。本研究首次发现了以铵沉降为主的城市地区苔藓15N值市区偏负、农村偏正的变化规律,这与氮沉降以硝态氮为主的城市苔藓15N变化(市区偏正、农村偏负)相反。此外,根据苔藓15N随大气沉降中铵态氮和硝态氮比值的变化规律,贵阳地区苔藓氮含量和15N的变化主要由两种不同铵源(城市铵和农业铵)的变化所控制,贵阳苔藓氮含量和15N的空间变化可以进一步作为铵沉降变化的证据。 5. 贵阳地区主要大气氮源(铵)的沉降机制与模式 贵阳市区往外石生苔藓氮含量随离市中心的距离呈指数降低(y=1.5e-0.13x+1.26),而15N值随距离对数升高(y=2.54Ln(x)-12.23),揭示了城市来源的铵沉降从市区往外随距离指数降低,其分布模式为点源模式,贵阳市区可被视为贵阳地区的一个点状氨源。而农村地区苔藓氮含量不随距离而变化、15N值不存在明显差异,反映了农业氨的面源分布模式。通过极限法计算苔藓氮含量和15N随距离变化的函数,氮沉降在离市中心17.2km以内以城市铵为主,以外以农业铵为主,城市铵的影响范围总体小于41km,城市铵随离市中心距离的变化关系为y=56.272e-0.116x-0.481。此外,贵阳市区往外不同方向的苔藓氮含量和15N随距离的变化梯度存在差异,表明城市铵向周边不同方向的传输具有非均一性,这主要与不同方向的地形条件、地表植被状况、风向、城市化程度等差异有关。本研究首次通过苔藓监测证实以铵沉降为主的城市,城市铵沉降的分布呈点源模式,并通过苔藓氮含量和15N的变化得出了城市铵的定量分布、沉降机制和影响因素。 6. 贵阳地区石生苔藓碳含量和13C值的变化及其意义 贵阳地区石生苔藓碳含量(34.47% ~ 52.76%)从市区到农村随距离指数降低(y=9.206e-0.042x+38.024),并与氮含量存在正相关关系,表明大气氮输入具有增加苔藓碳含量的作用。苔藓13C值(-30.69‰ ~ -26.96‰)从市区到农村随距离逐渐升高(y=0.674Ln(x)-30.03),反映了城市人为CO2的影响逐渐减小。此外,苔藓13C随碳氮含量增加而降低,碳氮同位素存在正相关关系,反映了石生苔藓光合作用与氮素吸收相互制约,市区较高的氮沉降或铵沉降增强了苔藓光合作用和碳代谢,使苔藓在固碳过程中发生更大的13C分馏。本研究首次发现了城市地区较高的氮沉降能够促进石生苔藓光合固碳能力,苔藓13C值能够指示城市人为CO2的影响以及氮沉降的生物效应。 7.其它创新之处 为深入认识城市地区氮沉降的变化及其生物响应,本研究还对石生苔藓光合色素含量进行了分析,首次探讨了石生苔藓光合生理参数和碳氮含量、碳氮同位素之间的关系。市区苔藓光合色素含量高于农村地区,叶绿素含量与碳氮含量存在正相关关系,表明光合色素分析可以反映环境胁迫状况、苔藓固碳能力和氮素营养状况。叶绿素含量与13C值呈负相关关系指示了氮沉降增强石生苔藓光合作用的机制。
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Both perceived organizational support and job stresses have impact on employees’ work outcomes. Great progresses have been made in past researches. However, there are many disputes about the impact of perceived organizational support (POS) on job performance (especially, safety performance), the impact of job stresses on job performance (especially, safety performance) and job attitudes, as well as the interaction of subordinates’ POS and job stresses, and the impact of supervisor on subordinates’ POS et al.. Thus, the aim of the study is to explore the impact of supervisors’ POS, leader-member exchange(LMX) on subordinates’ POS, the direct impact of subordinates’ POS and job stressors from task and rewards on work attitudes(job satisfaction, turnover intention) and safety behaviors(safety compliance and safety participation), and the interaction of subordinates’ POS and job stresses. Analyses are based on the data from interviewing of 20 staff, posts of a Chinese civil aviation Bulletin Board System (BBS) and surveys of 216 subordinates and 42 supervisors from two Chinese civil aviation Air traffic control centers (ATC). The major findings are listed as follows: Firstly, the exchange relationship between supervisors and members has impact on subordinates’ POS by the fully mediating role of subordinates’ perceived supervisor support (PSS). But supervisors’ POS have no impact on subordinates’ POS. Secondly, subordinates’ POS has a direct and positive impact on their job satisfaction and safety behaviors, and a negative impact on turnover intention. Specifically, the higher the employees’ perceived organizational support, the higher job satisfaction and safety behaviors, as well as the lower turnover intention they have. Moreover, POS has stronger relationship with safety participation behaviors than that of safety compliance behaviors. Thirdly, task-related stressor has no significant impact on job satisfaction, turnover intention and safety behaviors. And compensation-related stressor has significant and positive impact on turnover intention and safety behaviors, which means that with the compensation-related stress increases, turnover intention increases, safety behaviors including safety compliance and safety participation also increases. Fourthly, POS and task-related stressor, POS and compensation-related stressor have significant interaction, respectively. Specifically, POS moderates the relationship between task-related stressor and job satisfaction, and between task-related stressor and turnover intention. Moreover, POS also moderates the relationship between compensation-related stressor and safety compliance behaviors.
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Obsessive-Compulsive Symptoms, which are one of common factors effected on mental health of secondary school students, have been rarely studied at home and abroad. In accordance with the problems existed in these literature up till now, the thesis had mainly studied the measured tool, contents and structure, developmental features, psychosocial risk factors and integrated model of obsessive-compulsive symptoms from them by means of investigation with quetionnaires. The entire research was divided into three phases. 3185 students(age 14.68±1.75 years) were firstly measured with the 20-item Leyton Obsessional Inventory-Child Version(LOI-CV) at four secondary schools including six grades in Beijing city, which was applied to revise LOI-CV, and to study the structure and contents, developmental features and screen of obsessive-compulsive symptoms. Then, 216 subjects with obsessive-compulsive symptoms, paired with controls in the light of school, grade and gender, were investigated with 10 self-rating scales on obsessive-compulsive symptoms, anxiety, depression, personality, coping and attributional style, negative life events, parent's rearing style, family environment and life adaptation in school, and with an inventory on social demography. The results were used to explore psychosocial risk factors and integrated model of obsessive-compulsive symptoms. The third survey was only carried out, about two months after the second, among 264 subjects with obsessive-compulsive symptoms through MMOCI and Negative Life Event Scale for Adolescents, in order to probe into the integrated model. The research had mainly found: (1) LOI-CV can be used as a screen tool for obsessive-compulsive symptoms in urban adolescents in China; (2) Total screening-out ratio of obsessive-compulsive symptoms was 13.6% (male:15.0%, female:12.2%). The most common manifestations of obsessive-compulsive symptoms were hating dirt and contamination, doing things in exact manner, angry if someone messes desk, bad conscience but no one else, worry about cleanliness, repeated thoughts or words; the least were favorite or special number, spending extra time on homework, special number or words to avoid, talking or moving to avoid bad luck, fussy about hands. The checking and repetition, cleanliness and tidiness, general obsessions were more common forms than numbers-luck; (3) No differences were existed in serious degree of obsessive-compulsive symptoms, but the screening-out ratio in male was higher than it in female; (4) No differences were detected in the serious degree of obsessive-compulsive symptoms except the scores of cleanliness and tidiness among grades, but the screening-out ratio of the grades justly entering secondary school or going to graduate were higher than other ones; (5) The main psychosocial risk factors for obsessive-compulsive symptoms included anxiety, mother's over-protecting and over-interfering, fantasy, flexibility, self-actualization, peers relationship, sense of responsibility, negative life events, mother's occupation, help-seeking, and (6) The integrated model on psychosocial risk factors suggested that the possible developed and sustained mechanism of obsessive-compulsive symptoms was that personality, coping and attributional styles constructed the developmental diathesis foundation of obsessive-compulsive symptoms; negative life events were promoting factors of them. There was a dynamic interaction between personality and environmental factors. Negative emotion played a core role in the developmental process of them. The continued existence of obsessive-compulsive symptoms was related to pre-existed obsessive-compulsive symptoms and negative life events experienced by an individual. Therefore, this research not only let us get a deeper understanding of obsessive-compulsive symptoms and more entirely find out psychosocial risk factors, firstly applied diathesis-stress theory to comprehend the psychological mechanism of obsessive-compulsive symptoms and, moreover, elaborate and expand it, but also has more important practice significance of treatment, prevent and education for obsessive-compulsive symptoms in secondary school students.