Major element chemistry of sediments from the Darling–Barwon river and its tributaries: implications for sediment and phosphorus sources

In 1991, one of Australia's longest rivers, the Darling–Barwon, experienced one of the world's largest recorded algal blooms. Nearly 1000 km of river were affected. At the time of the bloom phosphorus originating from anthropogenic sources was believed to be the principal cause. In this study we have used major element chemistry to examine the sources of sediment and sediment‐associated phosphorus delivered to the Darling–Barwon River. We show that the sediments are derived primarily from the sedimentary and granitic bedrock areas of the catchment, not the intensively farmed basalt areas. We also show that the sediment currently in transport in the Darling–Barwon does not originate from contemporary upland erosion, but is probably derived from lowland areas of the catchment that contain more weathered material. Phosphorus concentrations in the sediments are consistent with those in natural soils of the region, and evidence from two sediment cores indicates that phosphorus concentrations have not changed significantly in the last 200 years. The implications of these findings for algal growth control strategies are discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

Seasonal and event‐based drivers of runoff and phosphorus export through agricultural tile drains under sandy loam soil in a cool temperate region

Frequent algal blooms in surface water bodies caused by nutrient loading from agricultural lands are an ongoing problem in many regions globally. Tile drains beneath poorly and imperfectly drained agricultural soils have been identified as key pathways for phosphorus (P) transport. Two tile drains in an agricultural field with sandy loam soil in southern Ontario, Canada were monitored over a 28‐month period to quantify discharge and the concentrations and loads of dissolved reactive P (DRP) and total P (TP) in their effluent. This paper characterizes seasonal differences in runoff generation and P export in tile drain effluent and relates hydrologic and biogeochemical responses to precipitation inputs and antecedent soil moisture conditions. The generation of runoff in tile drains was only observed above a clear threshold soil moisture content (~0.49 m³·m^?3 in the top 10 cm of the soil; above field capacity and close to saturation), indicating that tile discharge responses to precipitation inputs were governed by the available soil‐water storage capacity of the soil. Soil moisture content approached this threshold throughout the non‐growing season (October – April), leading to runoff responses to most events. Concentrations of P in effluent were variable throughout the study but were not correlated with discharge (p > 0.05). However, there were significant relationships between discharge volume (mm) and DRP and TP loads (kg ha^?1) for events occurring over the study period (R² ≥ 0.49, p ≤ 0.001). This research has shown that the hydrologic and biogeochemical responses of tile drains in a sandy loam soil can be predicted to within an order of magnitude from simple hydrometric data such as precipitation and soil moisture once baseline conditions at a site have been determined. Copyright © 2016 John Wiley & Sons, Ltd.     

岩性和种植年限对火龙果地土壤碳、氮、磷生态化学计量特征的影响

以石漠化问题突出区域——广西平果县太平镇耶圩火龙果种植园不同岩性背景(白云岩、碎屑岩)和不同种植年限(1、3、5a)土壤为研究对象,采用相关性分析和冗余分析方法探讨了不同岩性背景和火龙果种植年限下土壤碳、氮、磷生态化学计量特征及其影响因素。结果表明：①白云岩区土壤全磷含量显著高于碎屑岩区,而土壤有机碳含量、生态化学计量比(C/N、C/P和N/P)显著低于碎屑岩区;且白云岩和碎屑岩背景下的生态化学计量比(5.96、11.78、1.96和8.71、19.78、2.28)均远低于全国水平。②随着火龙果种植年限的增加,土壤有机碳、全氮含量和C/N、C/P、N/P呈现出逐渐增加的趋势,而土壤有效氮、全磷和有效磷含量无显著变化规律。随着土层深度增加,土壤有机碳、全氮、有效氮含量和C/N、C/P、N/P均增加,而土壤全磷含量无明显变化规律。③土壤C/N和C/P与有机碳、有效氮均呈显著正相关(P<0.01),而与土壤水分、容重呈显著负相关,土壤N/P与全磷呈显著负相关。④冗余分析表明不同岩性背景和火龙果种植年限下土壤有效氮含量是土壤碳、氮、磷及其生态化学计量比的重要影响因子,且呈显著正相关关系(P<0.01)。白云岩背景下火龙果的生长受到氮元素的影响更大,长期火龙果种植有利于碳、氮元素固存,土壤有效氮含量是影响土壤碳、氮、磷及其生态化学计量比的关键因子。     

离子吸附型稀土矿床形成的矿物表/界面反应机制

华南离子吸附型稀土矿床提供了全球超过90%的重稀土,是我国优势的战略性关键金属矿产资源。掌握这类矿床的成矿机制和禀赋特征,可为增加稀土资源储量和高效利用稀土资源提供理论支撑。离子吸附型稀土矿床主要发育在富稀土花岗岩、浅变质岩及火山岩的风化壳中。基岩中的(含)稀土矿物是风化壳中离子态稀土的主要来源,其矿物组合很大程度上决定了稀土矿床的禀赋和分异特征。在物理-化学风化和微生物作用下,造岩矿物、含稀土矿物和稀土独立矿物逐渐溶解,使稀土元素活化和再富集。一方面,母岩风化形成的黏土矿物和铁锰氧化物具有较大的比表面积和一定的表面电荷密度,是稀土离子的主要载体;另一方面,稀土离子通过离子交换、表面吸附与络合、共沉淀,以及形成次生稀土矿物等途径富集在次生矿物表面,其富集-分异特征和赋存状态受矿物类型、pH、微生物活动等因素所控制。利用高分辨透射电镜结合选区电子衍射和电子能量损失谱,以及同步辐射X射线吸收精细结构谱,有望在原子级尺度查明稀土的微观赋存状态。未来研究需更多关注基岩中(含)稀土矿物组合及其演化路径的制约因素、微生物风化对离子吸附型稀土矿床成矿作用的约束,以及稀土元素的微观赋存状态等问题。     

Parmanu-Gunak: Data Reduction Software for Isotope Dilution Analysis

Isotope dilution (ID) is a widely used analytical technique to determine elemental abundance to a high degree of accuracy and precision, using a spiked isotope tracer. This technique also enables efficient correction of the inevitable phenomenon of analytical mass fractionation during mass spectrometric analysis. It is also used to determine stable isotope variations of an element in a sample relative to a reference material, using tracers enriched in two isotopes (popularly known as the double spike method). Isotope dilution data reduction can be performed in Microsoft® Excel™ using different algorithmic approaches. Additional software such as iolite and MATLAB® offer algorithm implementations to perform these calculations. These are however limited to use within particular laboratories/research groups, or either require additional cost-bound software or some degree of knowledge in computer programming languages for use, or all of these. To ease this situation, a graphical user interface-based software is proposed (here named Parmanu-Gunak, meaning Atom-Calculator in Sanskrit text) to invert both single and double spiked isotope data, with the aim of making it a standard tool for ID data reduction. Examples of Nd and Mo isotopes are used to demonstrate the robustness of the program.     

莱州湾西南部海域及其毗邻河流水体营养盐的分布特征及长期变化趋势

根据2012年9月对莱州湾西南部海域及其毗邻10条河流的调查结果,以及近30年来关于莱州湾海域表层水营养盐的调查资料,报道了各条河流和近海海域的营养盐状况及该海域营养盐的长期变化趋势,结果表明:(1)10条主要调查河流的总溶解态氮(TDN)平均含量在1.82~10.66mg/L之间,其中有8条河流超过河流总氮劣五类水质标准,6条河流硝态氮(NO3-N)含量高于氨氮(NH4-N)。(2)所调查的5个近海断面中小清河口近海断面、虞河口近海断面及溢洪河口近海断面的DIN平均含量超过海水无机氮第四类水质标准;除小清河口近海断面外其余近海断面活性磷(PO4-P)含量均属一类海水水质。(3)部分断面营养盐含量在河口混合区淡水端升高,可能与咸淡水混合动力作用相关;莱州湾西部区域营养盐含量高于南部区域,南部的堤河氮、磷含量极高;原油开采活动可能是影响附近水体中营养盐含量及形态的重要因素。(4)从20世纪80年代初至90年代中期,莱州湾表层水无机氮平均含量经历了由低到高的变化,到90年代后期已属劣四类海水水质;无机磷平均含量在该时段呈降低趋势,但到90年代后期也保持在较高水平,随后又波动下降。(5)所调查的莱州湾近海区域整体处于磷限制潜在富营养状态;氮磷摩尔比(N∶P)在所考察的大部分时段内高于Redfield阈值(16),净营养盐收支呈磷减少而氮增加的总体变化趋势,近年来磷限制程度有所减缓。     

Geochemical speciation and spatial distributions of phosphorus in surface sediments from the basin of the Marcus-Wake seamounts in the western Pacific Ocean

The concentrations of five forms of phosphorus(P) including exchangeable or loosely adsorbed P(Ex-P), Febound P(Fe-P), authigenic P(Auth-P), detrital P(Det-P), and organic P(Org-P) from the basin among the Marcus-Wake seamounts(19.4°–24°N, 156.5°–161.5°E) in the western Pacific Ocean were quantified using a sequential extraction method(SEDEX) to investigate the distribution and sources of different P species.Concentrations of total P(TP) varied from 14.0 μmol/g to 44.1 μmol/g, with an average of...     

基于SCS和USLE的程海总磷总氮参照状态推断

将流域入湖的氮磷负荷分为点源和非点源两部分,基于SCS模型和USLE模型,分别计算流域入湖的溶解态和颗粒态非点源负荷,根据工业、城镇生活及规模养殖废水排放,计算了流域入湖的点源负荷。通过计算的入湖负荷和现有的湖泊氮磷浓度数据,建立了湖泊氮磷质量守恒模型。根据计算的逐年入湖氮磷负荷和建立的湖泊氮磷质量守恒模型,逆推逐年的湖泊氮磷浓度,确定湖泊氮磷参照状态。应用建立的模型推断程海的TP、TN参照状态分别为0.014 mg/L和0.247 mg/L。构建的湖泊氮磷参照状态推断模型,所需资料少,概念清晰,在资料缺乏的其他湖泊流域具有推广应用价值。     

针对IPCC评估报告中海洋碳循环的疑问——δ13C收支平衡法的验证

通过对比IPCC历次评估报告中全球碳循环的收支发现,尽管评估报告在估算各主要碳库及其间的通量时差别不大,但表层至中深层海水间溶解无机碳通量却存在巨大差异。利用δ¹³C的收支平衡检验了这一通量的适用范围,结果表明：IPCC 1996年和2007年评估报告对此通量估计过大,而1990年和2001年评估报告估计偏小。     

Stratigraphic,sedimentological and palaeoenvironmental constraints on the rise of the Urgonian platform in the western Swiss Jura

Urgonian‐type carbonates are a characteristic feature of many late Early Cretaceous shallow‐marine, tropical and subtropical environments. The presence of typical photozoan carbonate‐producing communities including corals and rudists indicates the prevalence of warm, transparent and presumably oligotrophic conditions in a period otherwise characterized by the high density of globally occurring anoxic episodes. Of particular interest, therefore, is the exploration of relationships between Urgonian platform growth and palaeoceanographic change. In the French and Swiss Jura Mountains, the onset and evolution of the Urgonian platform have been controversially dated, and a correlation with other, better dated, successions is correspondingly difficult. It is for this reason that the stratigraphy and sedimentology of a series of recently exposed sections (Eclépens, Vaumarcus and Neuchâtel) and, in addition, the section of the Gorges de l’Areuse were analysed. Calcareous nannofossil biostratigraphy, the evolution of phosphorus contents of bulk rock, a sequence‐stratigraphic interpretation and a correlation of drowning unconformities with better dated sections in the Helvetic Alps were used to constrain the age of the Urgonian platform. The sum of the data and field observations suggests the following evolution: during the Hauterivian, important outward and upward growth of a bioclastic and oolitic carbonate platform is documented in two sequences, separated by a phase of platform drowning during the late Early Hauterivian. Following these two phases of platform growth, a second drowning phase occurred during the latest Hauterivian and Early Barremian, which was accompanied by significant platform erosion and sediment reworking. The Late Barremian witnessed the renewed installation of a carbonate platform, which initiated with a phase of oolite production, and which progressively evolved into a typical Urgonian carbonate platform colonized by corals and rudists. This phase terminated at the latest in the middle Early Aptian, due to a further drowning event. The evolution of this particular platform segment is compatible with that of more distal and well‐dated segments of the same northern Tethyan platform preserved in the Helvetic zone of the Alps and in the northern subalpine chains (Chartreuse and Vercors).