空白校正对元素分析仪测定海水中颗粒有机碳结果准确性的影响分析     

刘毅  刘群  吴文广  杨珺  刘越  姜雅斐  张继红 《海洋科学》2020,44(12):78-83

颗粒有机碳（POC）在海洋生态系统乃至全球碳循环中发挥着重要作用，其准确获取至关重要。目前，元素分析仪测定POC是最准确和常用的分析方法，但取样忽略了水体溶解有机碳（DOC）可能带来的影响。针对空白样品如何获取才能有效去除DOC影响的问题，本文设计比较了5种取样方法对POC测定结果的影响，以及滤膜对数据的影响。结果显示，1）5种样品取样方法所得的结果差异显著，不进行空白校正会对结果产生较大误差；2）文献和本文设计的空白样取样方法均出现了空白值大于样品值的异常情况；3）样品继续抽人工海水100 mL即可有效洗去滤膜上吸附的DOC；4）未过滤的滤膜450℃灼烧5 h后可以有效去除滤膜上吸附的碳，但是存放时间越久滤膜从空气中吸附碳的概率越大。本研究确定的人工海水法可以有效去除DOC对测定结果的影响，样品测定结果重复性、精密度高，可准确用于海水POC样品的测定。  相似文献   

长江口邻近海域氮同位素的周日变化特征及其对营养盐过程的指示     

王文涛  俞志明  宋秀贤  吴在兴  袁涌铨 《海洋与湖沼》2020,51(4):909-918

长江口邻近海域的氮循环过程一直是近海富营养化研究领域的热点问题, 然而目前较少有针对短周期的调查研究。本文调查了该区域氮、磷、硅等主要营养盐及多种形态的氮稳定同位素的在潮周期周日变化特征。结果显示, NO_3~-、NH_4~+、PO_4~(3-)和SiO_3~(2-)的浓度范围分别为 14.09—55.85、0.21—2.26、0.82—1.08 和 16.80—33.85μmol/L, 而δ~(15)N-NO_3~-、δ~(18)O-NO_3~-、δ~(15)N_P和δ~(13)C_P 等的分布范围分别为 4.7‰—11.1‰、-2.0‰—7.8‰、-1.2‰—7.9‰和-22.9‰— -14.7‰。NO_3~-、PO_4~(3-)和SiO_2~(3-)均与盐度呈现明显的负相关特征, 说明三者的主要来源为长江冲淡水; 4NH(10)则随盐度升高而浓度增加, 且在底层高浓度出现时刻与高盐水团输入时刻一致, 说明外海输入是该区域铵盐的主要来源。另一方面, 氮稳定同位素(δ~(15)N-NO_2~-和δ~(15)N_P)未表现出随盐度的变化规律, 而δ~(18)3O-NO_3~-和δ~(13)C_P 则随盐度升高而增加, 说明淡水输入的同位素值低于海洋水平。通过对比中、高浓度叶绿素水体中NO_3~-、δ~(15)N-NO_3~-、δ~(18)O-NO_3~-的变化特征可以看出, 随NO_3~-浓度降低, δ~(15)N-NO_3~-值升高, 且呈现 6.2‰的分馏系数, 且氧同位素也随之增大, 指示水体中浮游植物对硝酸盐的同化吸收作用。而另一方面, 两种同位素的增加差值表现出△δ~(18)O︰△δ~(15)N1 , 说明硝酸盐在被消耗的同时还发生着补充作用。在较高盐度的水体中, 发现4NH(10)呈现出向硝酸盐的转化趋势并引起δ~(15)N-NO_3~-降低, 指示了底部明显的硝化过程, 与此前的研究结果一致。本文结果以期丰富对河口区氮循环和迁移转化的认知。  相似文献   

Sources and variability of CO2 in a prealpine stream gravel bar     

Kyle S. Boodoo  Jakob Schelker  Nico Trauth  Tom J. Battin  Christian Schmidt 《水文研究》2019,33(17):2279-2299

Gravel bars (GBs) contribute to carbon dioxide (CO₂) emissions from stream corridors, with CO₂ concentrations and emissions dependent on prevailing hydraulic, biochemical, and physicochemical conditions. We investigated CO₂ concentrations and fluxes across a GB in a prealpine stream over three different discharge‐temperature conditions. By combining field data with a reactive transport groundwater model, we were able to differentiate the most relevant hydrological and biogeochemical processes contributing to CO₂ dynamics. GB CO₂ concentrations showed significant spatial and temporal variability and were highest under the lowest flow and highest temperature conditions. Further, observed GB surface CO₂ evasion fluxes, measured CO₂ concentrations, and modelled aerobic respiration were highest at the tail of the GB over all conditions. Modelled CO₂ transport via streamwater downwelling contributed the largest fraction of the measured GB CO₂ concentrations (31% to 48%). This contribution increased its relative share at higher discharges as a result of a decrease in other sources. Also, it decreased from the GB head to tail across all discharge‐temperature conditions. Aerobic respiration accounted for 17% to 36% of measured surface CO₂ concentrations. Zoobenthic respiration was estimated to contribute between 4% and 8%, and direct groundwater CO₂ inputs 1% to 23%. Unexplained residuals accounted for 6% to 37% of the observed CO₂ concentrations at the GB surface. Overall, we highlight the dynamic role of subsurface aerobic respiration as a driver of spatial and temporal variability of CO₂ concentrations and evasion fluxes from a GB. As hydrological regimes in prealpine streams are predicted to change following climatic change, we propose that warming temperatures combined with extended periods of low flow will lead to increased CO₂ release via enhanced aerobic respiration in newly exposed GBs in prealpine stream corridors.  相似文献   

Impact of the water salinity on the hydraulic conductivity of fen peat          下载免费PDF全文

Lennart Gosch  Manon Janssen  Bernd Lennartz 《水文研究》2018,32(9):1214-1222

Coastal peatlands represent an interface between marine and terrestrial ecosystems; their hydrology is affected by salt and fresh water inflow alike. Previous studies on bog peat have shown that pore water salinity can have an impact on the saturated hydraulic conductivity (K_s) of peat because of chemical pore dilation effects. In this study, we aimed at quantifying the impact of higher salinities (up to 3.5% NaCl) on K_s of fen peat. Two experiments employing a constant‐head upward‐flow permeameter and differing in measurement and salinity change duration were conducted. Additionally, a third experiment to determine the impact of water salinity on the release of dissolved organic carbon (DOC) of the studied peat type was carried out. The results show a decrease of K_s with time, which does not depend on the water salinity but is differently shaped for different peat types. We assume pore clogging due to a conglomerate of physical, chemical, and biological processes, which rather depend on water movement rate and time than on water salinity. However, an increased water salinity did increase the DOC release. We conclude that salinity‐dependent behaviour of K_s is a function of peat chemistry and that for some peat types, salinity may only affect the DOC release without having a pronounced impact on water flow.  相似文献   

BOOK REVIEWS     

《The Professional geographer》1985,37(1):104-132

Books Reviewed in this article: Lob Trees in the Wilderness . Clifford and Isabel Ahlgren . Satellite Microwave Remote Sensing . T. D. Allan , ed. Sunbelt Cities: Politics and Growth Since World War II . Richard M. Bernard and Bradley R. Rice , eds. Legacy of Minneapolis: Preservation Amid Change . John R. Borchert , David Gebhard , David Lanegran , and Judith A. Martin . Bloomington, MN: Preparing a Historic Preservation Ordinance. Richard J. Roddewig . The Mountains of Northeastern Tasmania, A Study of Alpine Geomorphology . Nel Caine . Introductory Cartography . John Campbell . Englewood Cliffs, NJ: Changing Climate . Manual of Remote Sensing, Second Edition . 2 Vols. Robert N. Colwell , ed.-in-chief; David S. Simonett and John E. Estes , vol. eds. Remote Sensing in Meteorology, Oceanography and Hydrology . A. P. Cracknell , ed. Multidimensional Scaling . Mark L. Davison . Environmental Karst . Percy H. Dougherty , ed. The Urban Environment . Ian Douglas . Geomorphology of Europe . Clifford Embleton , ed. An Introduction to South Asia . B. H. Farmer . Great Geological Controversies . A. Hallam . Hazardous Waste Management: In Whose Backyard? Michalann Harthill , ed. Energy for Subsistence . Margaret Haswell . Perspective on Ratzel's Political Geography . James M. Hunter . Economic Deposits and their Tectonic Setting . Charles S. Hutchison . Energy Risk Assessment . Herbert Inhaber . Discovering the Vernacular Landscape . John Brinckerhoff Jackson . Climate and Energy Systems: A Review of Their Interactions . Jill Jäger . Dilemmas in Regional Policy . Antoni Kuklinski and J. G. Lambooy , eds. California Farmland: A History of Large Agricultural Landholdings . Ellen Liebman . The Spatial Organization of New Land Settlement in Latin America . Jacob O. Maos . Dark Continent: Africa as Seen by Americans . Michael McCarthy . Westport, CT: Climatology: An Introduction . John E. Oliver and John J. Hidore . Columbus, OH: The Geography of Warfare . Patrick O'Sullivan and Jesse W. Miller . The Expanding City. Essays in Honour of Professor Jean Gottmann . John Patten , ed. Scotland's Environment During the Last 30,000 Years . Robert J. Price . Integrated Urban Models . S. H. Putman . Development and the Environmental Crisis: Red or Green Alternatives? Michael Redclift .  相似文献   

EVOLUTIONARY CHARACTERISTICS OF LAKES AND PALAEOCLIMATIC UNDULATION IN THE Q AID AM BASIN,CHINA     

黄麒  Teh-Lung Ku  Fred M.Phillips 《中国海洋湖沼学报》1993,11(1):34-45

The Qaidam Basin is. a tectonically controlled depression at 2700 m altitude on the northern margin of the Tibet Plateau. A succession of Neogene clastic sediments indicates lake depocentre migration from NW to SE. Towards late Pliocene, evaporative conditions developed with formation of gypsum, halite, celestite, mirabilite and bloedite. Continued deformation through Pleistocene developed a series of NW- SE trending domes and troughs. This setting continued to exert a controlling influence on basin and brine evolution and the progressive development of sulfate to chloride brines as, dry conditions intensified in late Pleistocene, at the end of which, extensive flat floors were formed in Dalangtan, Qarhan and other playas.The, model, which was set up based on the synthetic analyses, divides the fluctuating palaeoclimate since 750ka,B. P. into 11 warm and humid stages and 10 dry and cold stages. The water of the lakes evaporated during the dry-cold periods and were freshened during the warm-humid periods  相似文献   

Isotopic constraints on fluid infiltration from an eclogite facies shear zone, Holsenøy, Norway     

D. MATTEY  D. H. JACKSON  N. B. W. HARRIS  S. KELLEY 《Journal of Metamorphic Geology》1994,12(3):311-325

Granulite facies anorthosites on Holsenøy Island in the Bergen Arcs region of western Norway are transected by shear zones 0.1–100 m wide characterized by eclogite facies assemblages. Eclogite formation is related to influx of fluid along the shears at temperatures of c. 700d?C and pressures in excess of 1.7 GPa. Combined carbon and nitrogen stable isotope, ⁴⁰Ar/³⁶Ar, trace-element and petrological data have been used to determine the nature and distribution of fluids across the anorthosite-eclogite transition. A metre-wide drilled section traverses the eclogitic centre of the shear into undeformed granulite facies garnet-clinopyroxene anorthosite. Clinozoisite occurs along grain boundaries and microcracks in undeformed anorthosite up to 1 m from the centre of the shear and clinozoisite increases in abundance as the edge of the shear zone is approached. The eclogite-granulite transition, marked by the appearance of sodic pyroxene and loss of albite, occurs within the most highly sheared section of the traverse. The jadeite-in reaction coincides with increased paragonite activity in mica. The separation between paragonite and clinozoisite reaction fronts can be semiquantitatively modelled assuming advective fluid flow perpendicular to the shear zone. The inner section of the traverse (0.25 m wide) is marked by retrogressive replacement of omphacite by plagioclase + paragonite accompanied by veins of quartz-phengite-plagioclase. C-N-Ar characteristics of fluid inclusions in garnet show that fluids associated with precursor granulite, eclogite and retrogressed eclogite are isotopically distinct. The granulite-eclogite transition coincides with a marked change in CO₂ abundance and δ¹³C (<36ppm, δ¹³C=-2% in the granulite; <180 ppm, δ¹³C=-10% in the eclogite). The distribution of Ar indicates mixing between influxed fluid (⁴⁰Ar/³⁶Ar > 25 times 10³) and pre-existing Ar in the granulite (⁴⁰Ar/³⁶Ar < 8 times 10³). δ¹⁵N values decrease from +6% in the anorthosite to +3% within the eclogite shear. The central zone of retrogressed eclogite post-dates shearing and is characterised by substantial enrichment of Si, K, Ba and Rb. Fluids are CO₂-rich (δ¹³C ～ -5%) with variable N₂ and Ar abundances and isotopic compositions. Both Ar and H₂O have penetrated the underformed granulite fabric more than 0.5m beyond the granulite/eclogite transition during eclogite formation. Argon isotopes show a mixing profile consistent with diffusion through an interconnecting H₂O-rich fluid network. In contrast, a carbon-isotope front coincides with the deformation boundary layer, indicating that the underformed anorthosite was impervious to CO₂-rich fluids. This is consistent with the high dihedral angle of carbonic fluids, and may be interpreted in terms of evolving fluid compositions within the shear zone.  相似文献   

Preliminary Analysis of V and Hp Light Curves of 26 Carbon Miras     

Zdeněk MikulÁšek  TomÁš GrÁf 《Astrophysics and Space Science》2005,296(1-4):157-160

Light variations of a representative sample of 26 more or less periodically variable carbon stars were analyzed on the basis of 2220 individual observations made by the Hipparcos satellite and 33 544 visual observations listed in AFOEV and VSOLJ databases within the interval JD = 2 448 000 (1988) ±6 cycles. We found the osculating linear ephemerides of all stars and their mean light curves, as well. We found that the light curves of the carbon Miras in our set can be satisfactorily expressed as a linear combination of only two basic light curves. The analysis was done by an own method combining robust regression and principal component analysis.  相似文献   

Land restoration in food security programmes: synergies with climate change mitigation     

Dominic Woolf  Dawit Solomon  Johannes Lehmann 《Climate Policy》2018,18(10):1260-1270

Food-insecure households in many countries depend on international aid to alleviate acute shocks and chronic shortages. Some food security programmes (including Ethiopia’s Productive Safety Net Program–PSNP – which provides a case study for this article) have integrated aid in exchange for labour on public works to reduce long-term dependence by investing in the productive capacity and resilience of communities. Using this approach, Ethiopia has embarked upon an ambitious national programme of land restoration and sustainable land management. Although the intent was to reduce poverty, here we show that an unintended co-benefit is the climate-change mitigation from reduced greenhouse gas (GHG) emissions and increased landscape carbon stocks. The article first shows that the total reduction in net GHG emissions from PSNP’s land management at the national scale is estimated at 3.4 million?Mg?CO₂e?y^?1 – approximately 1.5% of the emissions reductions in Ethiopia’s Nationally Determined Contribution for the Paris Agreement. The article then explores some of the opportunities and constraints to scaling up of this impact.

Key policy insights

• Food security programmes (FSPs) can contribute to climate change mitigation by creating a vehicle for investment in land and ecosystem restoration.

• Maximizing mitigation, while enhancing but not compromising food security, requires that climate projections, and mitigation and adaptation responses should be mainstreamed into planning and implementation of FSPs at all levels.

• Cross-cutting oversight is required to integrate land restoration, climate policy, food security and disaster risk management into a coherent policy framework.

• Institutional barriers to optimal implementation should be addressed, such as incentive mechanisms that reward effort rather than results, and lack of centralized monitoring and evaluation of impacts on the physical environment.

• Project implementation can often be improved by adopting best management practices, such as using productive living livestock barriers where possible, and increasing the integration of agroforestry and non-timber forest products into landscape regeneration.

  相似文献   

城市开发区工业企业的碳排放效率比较 ——以南京江宁经济技术开发区为例     

刘英  赵荣钦  张战平  丁明磊  焦士兴 《热带地理》2018,38(1):103-111

以南京市江宁经济技术开发区为例,基于199家企业样本,采用碳排放强度、单位碳排放的用水效率、单位碳排放的废弃物排放强度指数及单位产品的虚拟水含量和隐含碳排放等指标,对27种不同类型工业企业的碳排放效率进行了评价和分析。得出的主要结论为：1）不同类型工业企业的碳排放强度差异明显。南京市江宁区27类行业的平均碳排放强度为0.35 t/万元,其中电力、热力生产和供应业的碳排放强度最高,而仪器仪表制造业碳排放强度最低。2）尽管企业碳排放效率和水资源利用效率有一定的行业关联,但企业碳排放效率主要受经济效益、生产工艺、原料和能源类型等因素的影响。3）不同企业单位产品的隐含碳排放和虚拟水含量具有较大的差异。其中,轿车、铁矿石、金属铸件和摩托车等产品的虚拟水和隐含碳排放明显高于其他行业产品。4）企业碳排放与相应的三废排放强度具有一定的关联性。其中,碳排放与废气排放强度的关联度最高。5）在对未来企业排放效率评估、碳核查及碳配额分配中,不仅要考虑企业碳排放的经济效益,也要考虑企业的资源消耗和废弃物排放效率,并建立基于碳排放综合绩效评估的企业碳配额分配方案,这对于落实碳减排、推动资源节约和生产方式转变以及加强环境治理的多重目标的实现具有重要意义。  相似文献