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201.
Yu Zhong Yonghong Hao Xueli Huo Mingkun Zhang Qingyun Duan Yonghui Fan 《水文科学杂志》2013,58(11):2011-2023
ABSTRACTTo acquire better understanding of spring discharge under extreme climate change and extensive groundwater pumping, this study proposed an extreme value statistical decomposition model, in which the spring discharge was decomposed into three items: a long-term trend; periodic variation; and random fluctuation. The long-term trend was fitted by an exponential function, and the periodic variation was fitted by an exponential function whose index was the sum of two sine functions. A general extreme value (GEV) model was used to obtain the return level of extreme random fluctuation. Parameters of the non-linear long-term trend and periodic variation were estimated by the Levenberg-Marquardt algorithm, and the GEV model was estimated by the maximum likelihood method. The extreme value statistical decomposition model was applied to Niangziguan Springs, China to forecast spring discharge. We showed that the modelled spring discharge fitted the observed data very well. Niangziguan Springs discharge is likely to continue declining with fluctuation, and the risk of cessation by August 2046 is 1%. The extreme value decomposition model is a robust method for analysing the nonstationary karst spring discharge under conditions of extensive groundwater development/pumping, and extreme climate changes.
Editor D. Koutsoyiannis; Associate editor J. Ward 相似文献
202.
Lili Huo Yuanchun Zou Xianguo Lyu Zhongsheng Zhang Xuehong Wang Yi An 《中国地理科学(英文版)》2018,28(2):325-336
Content and density of soil organic carbon(SOC) and labile and stable SOC fractions in peat mire soil in wetland, soybean field and rice paddy field reclaimed from the wetland around Xingkai Lake in Northeast China were studied. Studies were designed to investigate the impact of reclamation of wetland for soybean and rice farming on stability of SOC. After reclamation, SOC content and density in the top 0–30 cm soil layer decreased, and SOC content and density in soybean field were higher than that in paddy field. Content and density of labile SOC fractions also decreased, and density of labile SOC fractions and their ratios with SOC in soybean field were lower than that observed in paddy field. In the 0–30 cm soil layer, densities of labile SOC fractions, namely, dissolved organic carbon(DOC), microbial biomass carbon(MBC), readily oxidized carbon(ROC) and readily mineralized carbon(RMC), in both soybean field and paddy field were all found to be lower than those in wetland by 34.00% and 13.83%, 51.74% and 35.13%, 62.24% and 59.00%, and 64.24% and 17.86%, respectively. After reclamation, SOC density of micro-aggregates( 0.25 mm) as a stable SOC fraction and its ratio with SOC in 0–5, 5–10, 10–20 and 20–30 cm soil layers increased. SOC density of micro-aggregates in the 0–30 cm soil layer in soybean field was 50.83% higher than that in paddy field. Due to reclamation, SOC density and labile SOC fraction density decreased, but after reclamation, most SOC was stored in a more complex and stable form. Soybean farming is more friendly for sustainable SOC residence in the soils than rice farming. 相似文献
203.
萃取—原子吸收法测定高纯氧化钐中的镍 总被引:3,自引:0,他引:3
在pH3的弱酸性介质中,用二乙基二硫代氨基甲酸钠_甲基异丁基酮萃取分离氧化钐以消除基体干扰,用4mol/LHNO3溶液反萃取后火焰原子吸收测定被富集的杂质镍。萃取时水相与有机相体积比为5∶1,反萃时体积比为1∶1,萃取时间5min,测定高纯氧化钐中杂质镍的回收率达98%。分离后的共存非稀土元素对测定镍无干扰。方法检出限为40μg/LNi,对w(Ni)=03×10-6的氧化钐测定6次,RSD=71%,试样加标回收率在93%~104%。 相似文献
204.
205.
Distribution and significance of C~_(40) alkanes in the extracts of Cretaceous source rocks from the Songliao Basin 总被引:3,自引:0,他引:3
Feng ZiHui Fang Wei Zhang JuHe Li ZhenGuang Huang ChunYan Wang Xue Zhao QinLing Huo QiuLi 《中国科学D辑(英文版)》2007,50(10):1510-1520
Source rock extracts and crude oils from the Songliao Basin were analyzed by high-temperature gas chromatography (HTGC), gas chromatography-mass spectrometry (HTGC-MS) and gas chromatography-isotope ratio-mass spectrometry (GC-IRMS), for high molecular-weight alkanes. The distributions of n-alkanes in the Nenjiang Formation extracts are in the C14―C63 range; a bimodal distribution occurs in the C-21 and C21―40 regions. The C30―C37 n-alkanes are accompanied by C29―C35 hopanes, whereas the high molecular-weight C45―C47 n-alkanes co-occur with abundant isoalkanes, alkylcyclohexanes and alkylcyclopentanes. The high δ 13C values of the n-alkanes and the microscopic maceral compositions indicate a highly diversified organic source input for the Nenjiang Formation source rocks, ranging from aquatic plants, blue alge-bacteria, to land plant material. In contrast, n-alkanes in the rock extracts of the Qingshankou Formation are characterized by a single modal distribution, with relatively low abundances of C29―C35 hopanes, but high molecular-weight isoalkanes, alkylcyclohexanes and alkylcyclopentanes. The relatively low δ 13C values of C22―C44 n-alkanes and organic material compositions indicate that the source rocks in the Qingshankou Formation contain dominantly type I algal organic matter. The relative abundance of C 40 compounds in source rocks changes little at low maturity stage, but decreases drastically at higher maturity levels, with a concurrent reduction in the odd/even carbon predominance. In crude oils, in contrast, the relative abundance of C 40 compounds appears to relate closely with the oil source and oil viscosity. 相似文献
206.
Tianen Zhai Jingtian Zhang Shouliang Huo Beidou Xi Mingzhou Su Chunzi Ma Zhuoshi He Jing Su 《Environmental Earth Sciences》2016,75(24):1496
Understanding the contents and reactivity of dissolved organic nitrogen (DON) is important for illustrating its productivity contribution in aquatic ecosystem. The primary objective of this study was to investigate the characteristics and algal activity of DON in the sediments of Lake Taihu. A series of experiments were carried out to evaluate the algal bioavailability of DON fractions in the sediments of Lake Taihu, Eastern China. DON extracted in the lake sediments was separated into hydrophilic and hydrophobic forms by DAX-8 resin, and ammonia nitrogen in raw sample and hydrophilic fraction was removed by cation exchange resin. 77.42–109.18% DON recovery rates were obtained after DON fractionation at ZSW and DPG stations. The hydrophilic DON was the main DON form contributing 62.74–76.33% of total DON concentrations. Selenastrum capricornutum was incubated for 15 days with different nitrogen forms (raw sample, hydrophilic and hydrophobic fractions). Approximately 33.69–79.23% DON of the three fractions was available for algal uptake in the incubation. The order of DON bioavailability was ranked as follows: raw sample > hydrophilic fraction > hydrophobic fraction, indicating that hydrophilic fractions and raw samples exhibited higher DON bioavailability for algae. Parallel factor analysis resulted in identification of tryptophan-like proteins, tyrosine-like proteins and humic acid (HA)-like substances during the incubation periods. During the growth phase, the relative fluorescent intensities of tryptophan-like proteins, tyrosine-like substance and HA-like substance accumulated greatly with 24.84–26.38, 27.82–62.73 and 0–28.92%, respectively. 相似文献
207.
于 1 999年夏季我国首次北极科学考察期间在楚科奇海采集了三个沉积物岩芯 ,并采用中子活化法 (INAA)测定了沉积物样品中稀土元素的含量。结果表明 ,其含量与东海大陆架细粒沉积物的稀土元素含量十分接近。稀土元素的含量沿沉积物岩心的垂直分布呈现出随深度轻微增大的趋势。页岩标准化的稀土元素配分模式相对平缓 ,Ce有轻度负异常 ,表明沉积物稀土元素除了陆源物质以外 ,也存在生物沉积作用的来源。稀土元素与指示陆源的元素Al具有良好的正相关关系 ,相对于地壳丰度所计算的富集因子接近于 1 ,进一步说明楚科奇海沉积物中的稀土元素以陆源物质输入为主 ,通过江河携带入海 ,最后随碎屑物质、悬浮物而沉积下来 ,并保持一种稳定的沉积状态。 相似文献
208.
1961—2010年桂北晚稻寒露风特征分析 总被引:6,自引:0,他引:6
利用广西融安1961—2010年逐日气温和降水量数据,按2008年中国气象局颁布的"寒露风等级气象行业标准",统计该地区近50 a寒露风发生情况。结果表明,近50 a晚稻寒露风屡年发生;从危害日数和天气过程次数来看,以轻度和湿冷型为主;从危害敏感期来看,抽穗开花期影响最严重,花粉母细胞减数分裂期次之,幼穗分化期影响相对较小;从寒露风出现早晚、危害日数和过程次数来看,寒露风年际变化较大,且自21世纪以来寒露风危害呈现减弱趋势。 相似文献
209.
1农业气象灾害预警技术研究 2002年是"十五"国家科技攻关计划项目"农林重大病虫害和农业气象灾害的预警及控制技术研究"之第13课题(编号:2001BA509B13)实质性研究的一年,在收集资料、田间试验和模型研制等方面取得了较好的阶段性进展.年内广泛收集了环流、海温、气候及田间试验等各类资料.开展了干旱对小麦影响盆栽试验和油菜盆栽淹水试验,并在荔枝和香蕉园建立自动气象站,进行小气候观测.初步研制出4种灾害的长期统计预测模型和华南寒害短期数值天气预报模式,建立了基于东北玉米、华北小麦和夏玉米以及江淮小麦、油菜生长过程的动态模拟模式,探讨了实现作物模型区域化的方法,开展了区域气候模式与东北下垫面嵌套,生成作物模式所需预报值的方法试验. 相似文献
210.
通过双差定位法,对江苏及邻域1990-2012年地震事件进行重新定位,其中包括部分人工爆破和塌陷事件。结果显示,重新定位后的爆破和塌陷事件震源深度均有明显改善;地震在空间分布上更加集中,部分地震有向构造带趋近的变化,较多地震呈丛集状出现,震源深度主要集中在5-25 km范围内。 相似文献