13 research outputs found

    Seasonal Variations in PM_(10) and Associated Chemical Species in Jiuxian Mountain in Fujian Province

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    于2011年3月~2012年1月期间在福建德化县九仙山气象站采集大气了PM_(10)样品,分析了九仙山大气PM_(10)中水溶性离子及二元羧酸,; 对其季节分布与来源进行了探讨。结果表明,九仙山大气PM_(10)、水溶性无机离子和有机二元羧酸的季节分布规律较为接近,都表现为春季的浓度显著高于; 其它季节,但9种二元羧酸对PM_(10)的贡献(0.51% 0.41%)显著低于水溶性离子(18.07 %; 8.73%)。其中,水溶性离子组成以NO_3~-和SO_4~(2-)的浓度为最高,其次为Na~+和NH_4~+;阴离子与阳离子当量浓度、NH_4; ~+与SO_4~(2-)当量浓度,以及NH_4~+与NO_3~-当量浓度之间都存在显著正相关关系。有机二元羧酸的组成以乙二酸的浓度为最高,占测量; 二元羧酸总量的75%左右,且随碳数增加呈逐渐递减趋势;来源特征比值(丙二酸/丁二酸、己二酸/壬二酸)、MODIS火点图及后向轨迹图显示,有机二元; 羧酸主要来自大气二次化学反应过程,生物质燃烧的直接贡献很小。PM_(10) samples were collected at the top of Jiuxian Mountain in Fujian; Province from March 2011 to January 2012 and were analyzed for inorganic; water-soluble ions and dicarboxylic acids to investigate their seasonal; variations and sources. The results showed that PM_(10) and its; associated species exhibited much higher levels in the spring than those; in other seasons but the total contribution of the nine species of; dicarboxylic acids to PM_(10) (0.51% 0.41%) was significantly lower; than that of the water-soluble ions (18.07% 8.73%). The water-soluble; ions were characterized by the highest concentrations of SO_4~(2-) and; NO_3~-,followed by Na~+ and NH_4~+. Significant positive correlations; were observed between cation and anion equivalents,as well as between; NH_4~+ and SO_4~(2-) or NO_3~-equivalents. Individual dicarboxylic acid; showed a monotonically decreasing trend with increasing carbon number in; which oxalic acid accounted for approximately 75% of the total; dicarboxylic acids. Characteristic ratios of malonic acid to succinic; acid and adipic acid to azelaic acid,MODIS fire spots,and backward; trajectories showed that dicarboxylic acids mainly originated from; secondary reactions in the atmosphere and that the direct contributions; of open biomass burning to dicarboxylic acid concentrations were; negligible.国家自然科学基金项目; 国家重点研发计划项目; 福建省自然科学基金计划资助项

    广义线性模型中极大拟似然估计的强相合性

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    广义线性模型中极大拟似然估计的渐近正态性与强相合性

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    小兴安岭沼泽甲烷通量日变化分析

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    利用静态暗箱—气相色谱法,研究了小兴安岭7种沼泽类型生长季初期、中期、末期甲烷(CH4)通量的日变化规律,结果表明:小兴安岭沼泽甲烷通量无统一的日变化规律,且与温度和水位两个环境因子的相关性较弱。7个沼泽类型中,仅毛赤杨(Alnus sibirica)沼泽和白桦(Betula platyphylla)沼泽甲烷通量峰值在生长季初期、中期、末期出现的时间大致相同,且都为单峰曲线;苔草(Carex schmidtii)沼泽、灌丛沼泽和落叶松(Larix gmelinii)—泥炭藓(Sphagnumspp.)沼泽甲烷通量的峰值在不同时期出现的时间不同,多数为单峰曲线;落叶松—苔草沼泽和落叶松—藓类沼泽甲烷通量速率较小,多数时间吸收甲烷,没有明显的日变化规律。不同类型沼泽和生长期之间甲烷通量没有统一的日变化规律,说明在进行区域甲烷排放总量的估测时,增加每天的观测频率,或者长期、大量的观测数据可能会对提高估测精度有很大帮助

    湘江长潭株段河床沉积物重金属污染Pb同位素地球化学分析

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    湘江长沙-湘潭-株洲(简称"长潭株")段是湘江流域重金属污染最严重的河段。以往研究得到沉积物严重受Cd、Cu、Pb、Zn、Mn等多种重金属的污染。但河流沉积物是一个复杂的环境单元,其物质组成既是流域岩石风化的产物,又是人为作用的反映。且湘江流域基岩(如花岗岩等)、土壤等环境介质本身就存在Cd、Cu、Pb、Zn、As等重金属元素高背景值。加上城市工业活动等人为排放,使得沉积物重金属的来源复杂化。因此,认识沉积物重金属

    Prediction of Energy Resolution in the JUNO Experiment

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    International audienceThis paper presents the energy resolution study in the JUNO experiment, incorporating the latest knowledge acquired during the detector construction phase. The determination of neutrino mass ordering in JUNO requires an exceptional energy resolution better than 3% at 1 MeV. To achieve this ambitious goal, significant efforts have been undertaken in the design and production of the key components of the JUNO detector. Various factors affecting the detection of inverse beta decay signals have an impact on the energy resolution, extending beyond the statistical fluctuations of the detected number of photons, such as the properties of liquid scintillator, performance of photomultiplier tubes, and the energy reconstruction algorithm. To account for these effects, a full JUNO simulation and reconstruction approach is employed. This enables the modeling of all relevant effects and the evaluation of associated inputs to accurately estimate the energy resolution. The study reveals an energy resolution of 2.95% at 1 MeV. Furthermore, the study assesses the contribution of major effects to the overall energy resolution budget. This analysis serves as a reference for interpreting future measurements of energy resolution during JUNO data taking. Moreover, it provides a guideline in comprehending the energy resolution characteristics of liquid scintillator-based detectors
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