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91.
聚硅酸溶胶和凝胶的电镜观察   总被引:8,自引:1,他引:8  
艾子萍  高宝玉 《环境化学》1994,13(2):119-122
用透射电子显微镜(TEM)和扫描电子显微镜(SEM)观察了硅酸溶胶的聚合过程。在pH值与Na2O·nSiO2模数一定时,其聚合速度与温度有关,温度高聚合快。聚硅酸溶胶粒子主要是圆形或椭圆形颗粒,粒子由于聚集变大,硅酸凝胶具有毛刷结构,其间隙被水填充。反应时,聚集、聚合和溶解同时进行,最后聚集起主要作用,凝胶形成。  相似文献   
92.
Patterns of Genetic Diversity and Its Loss in Mammalian Populations   总被引:3,自引:0,他引:3  
Abstract:  Policy aimed at conserving biodiversity has focused on species diversity. Loss of genetic diversity, however, can affect population persistence, evolutionary potential, and individual fitness. Although mammals are a well-studied taxonomic group, a comprehensive assessment of mammalian genetic diversity based on modern molecular markers is lacking. We examined published microsatellite data from populations of 108 mammalian species to evaluate background patterns of genetic variability across taxa and body masses. We tested for loss of genetic diversity at the population level by asking whether populations that experienced demographic threats exhibited lower levels of genetic diversity. We also evaluated the effect of ascertainment bias (a reduction in variability when microsatellite primers are transferred across species) on our assessment of genetic diversity. Heterozygosity did not vary with body mass across species ranging in size from shrews to whales. Differences across taxonomic groupings were noted at the highest level, between populations of marsupial and placental mammals. We documented consistently lower heterozygosity, however, in populations that had experienced demographic threats across a wide range of mammalian species. We also documented a significant ( p = 0.01) reduction in heterozygosity as a result of ascertainment bias. Our results suggest that populations of both rare and common mammals are currently losing genetic diversity and that conservation efforts focused above the population level may fail to protect the breadth of persisting genetic diversity. Conservation policy makers may need to focus their efforts below the species level to stem further losses of genetic resources.  相似文献   
93.
本文介绍了地震动物试验场建立、动物观测、数据处理和饲养管理等方面的工作,为动物习性异常与地震关系的研究积累了可贵的观测资料,对于动物的行为异常预报地震具有一定的参考价值。  相似文献   
94.
为验证一种水稻田非点源污染原位观测方法的准确性和适应性,以北京市上庄镇某试验水稻田为例,应用原位观测方法分别在水稻田进水口附近(4#观测点)和出水口附近(2#观测点)安装水位计观测稻田水深,利用同步观测的降雨数据以及田内5个采样点定期采集的水质数据,进行非点源污染试验研究,探究基于同一块水稻田不同位置的水深观测数据是否对该方法的应用产生影响.结果表明:①晒田期间,由于4#观测点处于相对低洼的位置,其水深数据显示4 d的无水期,与实际晒田时间相符,而2#观测点水深数据显示10 d无水.②基于2#、4#观测点水深数据得到总蒸散发和渗漏损失、总径流量以及灌溉量的相对偏差分别为1.3%、1.0%、1.8%;应用原位观测方法估算出该水稻田的灌溉量在2 620~2 710 m3之间.③基于2#、4#观测点水深得到的TN、NH4+-N、NO3--N、TP、CODCr输出系数的相对偏差在0.8%~8.0%之间.研究显示:水位计安装位置对原位观测方法应用的影响不大,且主要体现在晒田期的水深观测,建议将水位计安装在稻田相对低洼处,以确保能够完整地监测水稻生长季的水深变化;应用该方法能准确识别水稻田的径流量和灌溉量,对具有多个径流出口的水稻田非点源污染试验具有较好的准确性和适应性.   相似文献   
95.
由于大气是一个复杂介质,低层大气中湍流的存在使物质和能量的交换很剧烈,污染物的扩散传输现象明显.对不同高度不同区域的低层大气做立体观测,获取气态污染物浓度分布最直接的资料很有必要.综合利用地面观测站点、系留气球和飞机平台,于2016年11月25—26日在天津武清高村一次污染天气条件下对NOx和O3进行立体观测,得到了污染物的地面、垂直和低空区域分布特征,并结合气象因子进行分析研究.观测结果表明,地面$\varphi $(NOx)水平较高,日均值为230×10-9,超过了GB 3095—2012《环境空气质量标准》二级标准的限值,反映了高村冬季较高的污染水平,主要受当地交通源排放的影响.$\varphi $(NOx)随高度的上升呈下降趋势,受风速的影响明显,主要积聚在逆温层以下.低空$\varphi $(NOx)市区高于郊区,而处于更远郊区的高村$\varphi $(NOx)与市区相当,也反映了高村本地较高的NOx污染.高村地面$\varphi $(O3)低,日最大8 h平均值为8×10-9,反映了冬季低温辐射弱、光化学反应强度低的特点.随高度增加$\varphi $(O3)呈上升趋势,垂直分布特征主要与温度层结有关.低空$\varphi $(O3)呈郊区高于市区,高村(远郊区)高于近郊区的特征.研究显示,$\varphi $(NOx)的升高导致$\varphi $(O3)下降,这可能与高村冬季的$\varphi $(VOCs)/$\varphi $(NOx)偏低有关,需要结合VOCs观测数据做进一步分析.   相似文献   
96.
Tetrabromobisphenol A (TBBPA) and its derivatives are now being highly concerned due to their emerging environmental occurrence and deleterious effects on non-target organisms. Considering the potential neurotoxicity of TBBPA derivatives which has been demonstrated in vitro, what could happen in vivo is worthy of being studied. Tetrabromobisphenol A bis(2-hydroxyethyl ether) (TBBPA-BHEE), a representative TBBPA derivative, was selected for a 21-day exposure experiment on neonatal Sprague Dawley (SD) rats through intranasal administration. The neurobehavioral, histopathological changes, and differentially expressed genes based on RNA microarray were investigated to evaluate the neurological effects of this chemical. The results indicated that TBBPA-BHEE exposure significantly compromised the motor co-ordination performance and the locomotor activities (p < 0.05). The neurobehavioral phenotype could be attributed to the obvious histopathological changes in both cerebrum and cerebellum, such as neural cell swelling, microglial activation and proliferation. A total of 911 genes were up-regulated, whereas 433 genes were down-regulated. Gene set enrichment analysis showed multiple signaling pathways, including ubiquitin-mediated proteolysis and wingless-int (Wnt) signaling pathway etc. were involved due to TBBPA-BHEE exposure. The gene ontology enrichment analysis showed the basic cellular function and the neurological processes like synaptic transmission were influenced. The toxicological effects of TBBPA-BHEE observed in this study suggested the potential neuronal threaten from unintended exposure, which would be of great value in the biosafety evaluation of TBBPA derivatives.  相似文献   
97.
成都市大气细颗粒物组成和污染特征分析(2012-2013年)   总被引:18,自引:4,他引:14  
陈源  谢绍东  罗彬 《环境科学学报》2016,36(3):1021-1031
为了解成都市大气细颗粒物的污染特征,于2012年5月-2013年5月在成都市城区开展了每6 d采集1次样品的长期颗粒物观测.利用十万分之一分析天平、热光碳分析仪、离子色谱、电感耦合等离子体质谱(ICP-MS)分别分析了颗粒物样品的质量浓度、有机碳/元素碳、水溶性离子、无机元素等,同步收集了污染物在线观测数据、气象数据和卫星遥感数据.结果表明,采样期间,成都市可吸入颗粒物(PM10)和细粒子(PM2.5)浓度颗粒物浓度分别高达(129.7±76.4)和(91.6±54.3) μg·m-3,PM2.5中以二次无机离子(SNA,43.6%)和有机物(OM,31.2%)污染最为突出,其次为土壤组分(Soil,13.8%)、元素碳(EC,5.0%)和微量元素(Trace,0.8%);1月、3月、5月和10月是污染较重的月份.通过比较揭示了不同污染源影响下的典型污染特征.生物质燃烧期间,成都城区PM2.5浓度达214.3 μg·m-3,PM2.5/PM10比达0.89,其中OM贡献增加至57.2%,K+浓度达8.7 μg·m-3,OC/EC比达8.3,SNA比重下降;而沙尘传输期间,PM2.5浓度为122.6 μg·m-3,仅占PM10浓度的0.28,PM2.5中土壤组分比例剧增至77.3%,SNA和无机元素的比重明显下降;静稳天气下PM2.5浓度为261.0 μg·m-3,各组分比重并无明显变化,硝酸盐和铵盐比例稍有增加.  相似文献   
98.
选取青海前兆台网的德令哈等5个井孔开展水温对比观测,对这五个井孔的水温原始观测数据和对比观测数据进行对比分析,从两组数据变化形态、差值、日变幅等方面发现不同的井孔两套数据的相似程度不同,其中以德令哈台为最好,湟源和格尔木次之,互助和佐署井则较差。分析认为主要原因有探头安装情况、仪器型号和仪器工作状态的影响。  相似文献   
99.
There has been little evaluation of anecdotal sightings as a means to confirm new incursions of invasive species. This paper explores the potential for equivocal information communicated by the media to account for patterns of anecdotal reports. In 2001, it was widely reported that red foxes (Vulpes vulpes) had been deliberately released in the island state of Tasmania (Australia), although this claim was later revealed to be baseless. Regardless, by 2013 a total of 3153 anecdotal fox sightings had been reported by members of the public, which implied their distribution was wide. For each month in 2001–2003, we defined a monthly media index (MMI) of fox‐related media coverage, an index of their relative seasonal abundance (abundance), and a factor denoting claims of fox evidence (claimed evidence) regardless of its evidentiary quality. We fitted a generalized linear model with Poisson error for monthly totals of anecdotal sightings with factors of year and claimed evidence and covariates of MMI, abundance, and hours of darkness. The collective effect of psychological factors (MMI, claimed evidence, and year) relative to biophysical factors (photoperiod and abundance) was highly significant (χ2 = 122.1, df = 6, p < 0.0001), whereas anticipated changes in abundance had no significant influence on reported sightings (p = 0.15). An annual index of fox media from 2001 to 2010 was strongly associated with the yearly tally of anecdotal sightings (p = 0.018). The odds ratio of sightings ranked as reliable by the fox eradication program in any year decreased exponentially at a rate of 0.00643 as the total number of sightings increased (p < 0.0001) and was indicative of an observer‐expectancy bias. Our results suggest anecdotal sightings are highly susceptible to cognitive biases and when used to qualify and quantify species presence can contribute to flawed risk assessments.  相似文献   
100.
在安全生产总体形势逐步好转的情况下,中国职业病危害致病因素中粉尘和噪声占有不可忽视的分量.本文通过对国内外在线监测技术的发展现状的详细分析,引入国内外先进的粉尘和噪声在线监测技术构建了职业安全健康在线监测系统基本架构,对其基本工作性能和实际能产生的工作效果进行描述,并对其产生的科技进步性进行阐述.  相似文献   
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