Composition and sources of organic matter in atmospheric PM10 over a two year period in Beijing, China

The solvent-extractable organic compounds of atmospheric PM₁₀ samples, collected over two years beginning in 2003 at urban and suburban sites of Beijing, were characterized using gas chromatography–mass spectrometry (GC–MS). The elemental carbon (EC) contents were determined and ranged from 4.3 to 42 μg m^− 3. Organic compounds in total extracts were identified and included unresolved complex mixture (UCM) and series of n-alkanes, n-alkanols, n-alkanoic acids, polycyclic aromatic hydrocarbons (PAHs); saccharides, alkanedioic acids, steroids, and other biomarkers and source tracers. The seasonal variations of their relative abundances are discussed. The abundance order for the major molecular classes in the particulate organic matter (POM) was the following: UCM > saccharides > n-alkanoic acids >n-alkanes > n-alkanols > PAHs > hydroxy-PAHs > other biomarker tracers. Based on the genetic significance of the molecular tracers, the dominant sources of POM are proposed for the two sampling sites. The emissions from fossil fuel use (both coal and petroleum products), biomass combustion, other pyrolysis sources, higher plant wax, and secondary products contribute > 98.0% of the POM mass. The fossil fuel use (average = 65% of POM) is the largest contributor and derives mainly from vehicular traffic.     

土地利用变化对气候影响的研究进展

为满足人类对食物、纤维、水和居住地的需求,全球土地利用格局发生了巨大的变化,IPCC 第四次评估报告（IPCC,2007）指出土地利用变化是人类影响气候的重要强迫之一。土地利用变化对气候的影响分为生物地球物理作用和生物地球化学作用。分别对有关生物地球物理作用和生物地球化学作用的研究进展以及研究热点进行了综述;并从定量评估两者对气候影响的相对贡献以及两者共同效应的角度,回顾了辐射强迫计算和耦合模式数值模拟两种方法的研究进展,及其在森林恢复、人工造林以及碳封存等气候变化应对措施可行性评估中的应用。最后分析和展望了当前土地利用变化对气候影响相关研究中的不确定性以及未来发展方向。     

外贝加尔大骨节病地区水文地球化学特征分析(英文)

本文通过对在外贝加尔大骨节病区水文地球化学研究结果表明,该地区天然水呈现出高浓度的磷(高达3.5mg/L),同时,锰、硅、铅等元素也呈现出高浓度的地球化学特征。分析水文地球化学数据,认为大骨节病可能与生物地球化学性质的多种因素有关系。进一步研究大骨节病的成因机制需要新的可靠的环境地球化学数据。     

同位素示踪技术在海洋环境研究中的应用

综合δD、δ18O、224Ra、226Ra、228R、钍系同位素和210Pb、14C等同位素示踪技术研究的最新成果,概述了同位素示踪技术在海洋水体运动、颗粒动力学、海洋生物生产力、沉积动力学、古海洋学等方面的研究进展,提出了在这一领域应重点发展的研究方向,以期推动同位素示踪技术在海洋环境研究中的应用。     

Residence time control on hot moments of net nitrate production and uptake in the hyporheic zone

The retention capacity for biologically available nitrogen within streams can be influenced by dynamic hyporheic zone exchange, a process that may act as either a net source or net sink of dissolved nitrogen. Over 5 weeks, nine vertical profiles of streambed chemistry (NO₃^? and NH₄⁺) were collected above two beaver dams along with continuous high‐resolution vertical hyporheic flux data. The results indicate a non‐linear relation of net NO₃^? production followed by net uptake in the hyporheic zone as a function of residence time. This Lagrangian‐based relation is consistent through time and across varied morphology (bars, pools, glides) above the dams, even though biogeochemical and environmental factors varied. The empirical continuum between net NO₃^? production and uptake and residence time is useful for identifying two crucial residence time thresholds: the transition to anaerobic respiration, which corresponds to the time of peak net nitrate production, and the net sink threshold, which is defined by a net uptake in NO₃^? relative to streamwater. Short‐term hyporheic residence time variability at specific locations creates hot moments of net production and uptake, enhancing NO₃^? production as residence times approach the anaerobic threshold, and changing zones of net NO₃^? production to uptake as residence times increase past the net sink threshold. The anaerobic and net sink thresholds for beaver‐influenced streambed morphology occur at much shorter residence times (1.3 h and 2.3 h, respectively) compared to other documented hyporheic systems, and the net sink threshold compares favorably to the lower boundary of the anaerobic threshold determined for this system with the new oxygen Damkohler number. The consistency of the residence time threshold values of NO₃^? cycling in this study, despite environmental variability and disparate morphology, indicates that NO₃^? hot moment dynamics are primarily driven by changes in physical hydrology and associated residence times. Copyright © 2013 John Wiley & Sons, Ltd.     

Variable source contributions to river bed sediments across three size fractions

Sediment tracing using geochemical properties is an efficient way to identify the spatial sources of transported sediments delivered to waterways. Here, the contribution of soil sources to river bed sediments has been quantified in Emu Creek, a headwater catchment in south eastern Queensland, Australia. Soil samples were collected from the eight major rock types present in the catchment and were related to river bed sediments collected from eight sites along the main channel. Geochemistry, as characterized by 39 elemental concentrations, was measured using inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Three particle size fractions were examined, <10, 10–63 and 63–212 µm, with the three resultant mixing models showing divergent results. We conclude that the results of sediment mixing models based on the analysis of one grain size should not be assumed to apply across the entire particle size range of transported sediment, emphasizing the need to match the size fraction used in tracing studies to that size fraction of interest in downstream sinks. Furthermore, we present results highlighting the control transport distance plays in source dominance, with this particularly evident in the coarser fraction, where local sources dominate over more distant sources. Copyright © 2015 John Wiley & Sons, Ltd.     

茶园生态系统铝的生物地球化学循环

根据近年作者及国内相关研究数据,分析茶园生态系统中各子系统Al的库容、循环流量和速率,提出茶园生态系统Al的生物地球化学循环模型.生态系统Al的惰性库、调节库和活动库之比为10 000∶200∶1;Al的内外循环量都很大,分别达51.89 kg.hm-2.a-1和33.48kg.hm-2.a-1;调节库和活动库Al的周转速率非常快,年更新率分别达0.34%和55.48%,体现了其他生态系统所没有的特别高的Al循环特征;茶园Al循环导致了土壤的加速酸化、无机态Al向有机结合态Al的转化和生态系统中有机结合态     

Towards a simple dynamic process conceptualization in rainfall–runoff models using multi‐criteria calibration and tracers in temperate,upland catchments

Empirically based understanding of streamflow generation dynamics in a montane headwater catchment formed the basis for the development of simple, low‐parameterized, rainfall–runoff models. This study was based in the Girnock catchment in the Cairngorm Mountains of Scotland, where runoff generation is dominated by overland flow from peaty soils in valley bottom areas that are characterized by dynamic expansion and contraction of saturation zones. A stepwise procedure was used to select the level of model complexity that could be supported by field data. This facilitated the assessment of the way the dynamic process representation improved model performance. Model performance was evaluated using a multi‐criteria calibration procedure which applied a time series of hydrochemical tracers as an additional objective function. Flow simulations comparing a static against the dynamic saturation area model (SAM) substantially improved several evaluation criteria. Multi‐criteria evaluation using ensembles of performance measures provided a much more comprehensive assessment of the model performance than single efficiency statistics, which alone, could be misleading. Simulation of conservative source area tracers (Gran alkalinity) as part of the calibration procedure showed that a simple two‐storage model is the minimum complexity needed to capture the dominant processes governing catchment response. Additionally, calibration was improved by the integration of tracers into the flow model, which constrained model uncertainty and improved the hydrodynamics of simulations in a way that plausibly captured the contribution of different source areas to streamflow. This approach contributes to the quest for low‐parameter models that can achieve process‐based simulation of hydrological response. Copyright © 2009 John Wiley & Sons, Ltd.     

BIOGEOCHEMICAL BEHAVIOR OF NUTRIENTS AND THEIR FLUXES IN THE MINJIANG RIVER ESTUARY

IMRODUcTlONThe577km1ongMinjiangRiver,thelongestriverinFujianProvinceofChina,hasa6O992km2drainagebasin.Thewaterdischargeislarge(meaninyearsis198Om/s).TheannualrunofffromtheMinjiangRiveris5.84xlOlom,WhichismorethanthatoftheHuangheRiver,andranksthirdintheannualrunoffofmaorChineseriversWhang,l994).SimdentnutrientSfromtheMinjiangRivertotheseaisanarisa-ryconditionforthefonnationandcontinuingexistenceoftheMindongFisheryGroundandtheMihahongFisheryGround.Inthendingareaofriverwaterwithseaw…     

氯离子质量平衡法应用问题刍议

氯离子质量平衡法(CMB)利用惰性示踪剂Cl-可以揭示区域地下水平均补给速率,补给事件和环境、气候变化事件等信息,可为相关研究提供可靠的信息。虽然该方法简单、有效,已经得到大量应用,但是也具有明显的局限性。综述了基于CMB法的相关研究,回溯了该方法的提出和演化,讨论了其主要假设条件和应用的局限性,阐明为了准确地应用该方法需要加强的方面。首先要重视氯离子干沉降的观测和研究。其次要加强氯离子沉降空间变化的观测和研究。在方法上要注意综合采用多种示踪剂、土壤理化性质和平行钻孔等手段来研究。最后要加强对氯离子平衡过程,及其相关的自然过程和人类活动的研究。对促进氯离子质量平衡法在地下水研究方面的应用和发展,具有一定的参考价值。