Impact of anthropogenic geochemical change and aquifer geology on groundwater phosphorus concentrations     

《Applied Geochemistry》2016

Geologic and geochemical variations across a 4200 km² area of south-central Wisconsin (USA) were used to examine their relationship to phosphorus concentrations in groundwater from more than four hundred private water supply wells. Surficial geology in the study area ranged from Cambrian sandstones to Ordovician dolomites. Groundwater phosphorus concentrations were higher in aquifers of older Cambrian age compared to the concentrations in aquifers of younger Cambrian and Ordovician age. Because iron concentrations were relatively low in these waters and agricultural land use was similar in all geologic regions, we propose that the differences in bedrock phosphorus and anthropogenic geochemical impacts explain the differences in phosphorus concentrations between aquifers. Within the older Cambrian aquifers, groundwater phosphorus concentrations were elevated in groundwater with higher nitrate-nitrogen concentrations. This finding is consistent with the presence of phosphorus within sediment in these strata and geologic conditions that weakly buffered pH reduction from anthropogenic acidification. In contrast, groundwater phosphorus concentrations in younger Cambrian and Ordovician aquifers were not elevated in samples with higher nitrate. Anthropogenic acidification in these carbonate-rich aquifers was neutralized through increased carbonate weathering, which led to higher groundwater calcium and alkalinity and would limit the dissolution of phosphate-rich minerals, such as apatite, where present. Low iron concentrations observed in most samples suggest that the phosphorus release in the Cambrian strata occurs beyond the zone of secondary mineral retention in the soil. These results have important implications for the eutrophication of inland surface waters in areas with bedrock phosphorus and anthropogenic acidity that is not neutralized before it contacts phosphatic rock.  相似文献   

同位素双稀释剂计算软件(DS_CAL)的开发及其地球化学应用     

赵严  温汉捷  周正兵  万建军 《地质学报》2021,95(5):1644-1653

二十一世纪以来,随着多接收电感耦合等离子体质谱仪(MC-ICP-MS)和热电离质谱仪(TIMS)的发展和广泛应用,多种非传统稳定同位素体系(Li、B、Mg、Ca、Mo、Cd、Fe和Zn等)的分析方法得到了快速发展,而仪器的质量分馏校正是进行准确同位素分析的关键因素之一.双稀释剂法被认为是最理想的仪器质量分馏校正方案,能够获得高精度的同位素比值.然而,复杂的计算推导和数据处理在一定程度上限制了双稀释剂法的使用和推广.在前人双稀释剂理论研究的基础上,本研究自主开发了双稀释剂数据处理平台(DS_CAL,基于Microsoft Excel VBA).该平台集合了测试数据的批量导入、目标元素参数的添加与修改、数据批量计算等操作,能够同时处理稳定同位素和放射性成因同位素体系的双稀释剂法数据计算,且不同实验室也能够根据所使用稀释剂的组成自主修改计算参数.本文还通过Mo同位素测试和计算实例,不仅显示出双稀释剂法具有高的测试精度,还展示了DS_CAL在双稀释剂法数据处理计算中的便捷性与高效性.DS_CAL能够应用于所有适用双稀释剂法计算的同位素体系,该平台的开发将有助于同位素双稀释剂技术的推广和发展.  相似文献   

Modeling the near-field effects of the worst-case tsunami in the Makran subduction zone   总被引：1，自引：0，他引：1  

Mohammad Heidarzadeh  Moharram D. Pirooz 《Ocean Engineering》2009,36(5):368-28

As a first step towards the development of inundation maps for the northwestern Indian Ocean, we simulated the near-field inundation of two large tsunami in the Makran subduction zone (MSZ). The tsunami scenarios were based on large historical earthquakes in the region. The first scenario included the rupture of about 500 km of the plate boundary in the eastern MSZ, featuring a moment magnitude of M_w 8.6. The second scenario involved the full rupture of the plate boundary resulting from a M_w 9 earthquake. For each scenario, the distribution of tsunami wave height along the coastlines of the region is presented. Also, detailed runup modeling was performed at four main coastal cities in the region for the second scenario. To investigate the possible effect of splay fault branching on tsunami wave height, a hypothetical splay fault was modeled which showed that it can locally increase the maximum wave height by a factor of 2. Our results showed that the two tsunami scenarios produce a runup height of 12-18 m and 24-30 m, respectively. For the second scenario, the modeled inundation distance was between 1 and 5 km.  相似文献   

A method to calculate the neutralization potential of mining wastes   总被引：3，自引：2，他引：3  

R. W. Lawrence  Michael Scheske 《Environmental Geology》1997,32(2):100-106

 The determination of neutralization potential (NP) of mining wastes is an essential part of waste characterization for acid rock drainage (ARD) prediction. Interpretation of NP values requires consideration of the mineralogical composition of the waste. Different minerals can neutralize acid drainage at different rates and in different pH ranges. The test conditions of widely used laboratory procedures to determine NP do not distinguish between such differences and overestimation of NP can often result. A simple procedure is proposed in which the effective NP is calculated based on mineralogical composition and the relative reactivities of component minerals. Mineralogical composition is calculated from easily determined analytical values using a CIPW normative procedure. Comparison of calculated NP values for 92 samples with experimentally determined values from tests designed to prevent the overestimation of NP indicates that the method is successful in predicting an effective NP value in most cases. The procedure is considered to be a cost-effective means of providing confident routine ARD prediction when used in combination with other tests and analyses. Received: 1 August 1996 / Accepted: 11 November 1996  相似文献   

Categorisation and Harmonisation of Probabilistic Earthquake Hazard Assessments with Respect to Statistic Representation of Input Data     

V. Schenk  Z. SchenkovÁ  P. Kottnauer 《Natural Hazards》1997,15(2-3):121-137

Probabilistic hazard calculations were tested with respect to input data uncertainties. Statistical approximations of input data allow the regression coefficients and their standard deviations to be determined. Since inaccuracies of the regressions closely depend on the input data uncertainties, the standard deviations of the individual coefficients were used as a measure of input data parametrisation. Differences in the hazard outputs, caused only by various combinations of the regression coefficients and their standard deviations determined for the cumulative recurrence graph and the attenuation law, were studied. It was concluded that the hazard calculation conditions should be (a) strictly defined and always quoted with every hazard assessment, and (b) standardized in order to establish a common liability of earthquake hazard calculations. The established categorisation of the earthquake hazard assessments divides the probabilistic hazard calculations according to their reliability and helps users to apply them in earthquake engineering practice. The credible hazard assessments corresponding to 90% probability can be recommended for common structures whereas the maximum credible hazard assessments coinciding with 95% probability yield values close to hazard assessments of important structures, hospitals, bridges, etc.  相似文献   

Investigation of Performance of Turret Assembly in Inboard Turret Mooring System     

Ma Peisun  Ma Lie  Lu Shunshou Associate Professor  Shanghai Jiaotong University  Shanghai Graduate  Shanghai Jiaotong University  Shanghai Engineer  Shanghai Jiaotong University  Shanghai 《中国海洋工程》1991,(4)

To fulfil the need of development of offshore oil floating production system, the performance of turret assembly in an inboard turret mooring system has been investigated in the paper. By means of systematic evaluation, the optimal structure of the turret for single-point mooring systems has been determined. Through model tests of a turret mooring system, several groups of data such as forces, moments and displacements under different environmental conditions have been obtained. Stresses and strains of the turret structure have been calculated by means of the finite element method corresponding to the situation in the model experiment. The study shows that the selected turret structure and the designed turret assembly are technically feasible.  相似文献   

Assessment of seismic resistance of masonry structures including boundary conditions     

Emília Juhsov  Milan Hurk  Zbigniew Zembaty 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):1193-1197

The paper is devoted to the investigation of seismic response of the masonry structure and describes experiences with modelling of boundary conditions during the test of large heavy model on 6DOF shaking table. The main aim of the research was how to increase dynamic resistance capacity of old masonry buildings including the medium and strong seismic effects. The results of theoretical and numerical analyses are compared including initial forecasting calculations made before any test started. The emphasis is given to the boundary conditions reached during the excitation of the large masonry model via shaking table. Strengthening and retrofitting procedures and their effects are discussed when special fibre mortar is used for repair and strengthening of masonry parts of structure.  相似文献   

Solving the kriging problem by using the Gram-Schmidt orthogonalization     

Marek Kacewicz 《Mathematical Geology》1991,23(1):111-118

This paper presents an approach to solve the kriging problem, defined in terms of projections, by using Gram-Schmidt orthogonalization. The Gram-Schmidt orthogonalization allows us to find an optimal approximationY* in then-dimensional subspaceH _n of any vectorY element of a Hilbert spaceH. This approach requiresO(n ³) multiplication operations to obtain an orthogonal basis, andO(n ²) multiplications needed to calculate kriging solution for a given point.  相似文献   

冬夏季海面风场和海洋表层流的数值计算   总被引：2，自引：0，他引：2  

钱永甫  王谦谦 《热带气象学报》1994,10(3):212-221

设计了一个海面风场的诊断模式和海洋表层流的数值计算模式。只要输入海面气压场并利用迭代方法，即可求得海洋表面的风场和海洋场。利用１月和７月多年平均的海平面气压场，对这两个模式的性能进行了检验。结果表明，无论冬夏，用海平面气压场诊断出的海面风场与观测到的海面风场很接近，而与地转风场有很明显的区别。用海面风场和海面气压场启动的海洋表面流，与实况也较一致。本文的试验结果还表明，计算海流时，不应忽略海平面气  相似文献   

Thermodynamic stability of various alkylated, dealkylated and rearranged 17α- and 17β-hopane isomers using molecular mechanics calculations     

Ewa Kolaczkowska  Nacer-Eddine Slougui  David S. Watt  Robert E. Maruca  J. Michael Moldowan 《Organic Geochemistry》1990,16(4-6)

The thermodynamic stability of selected alkylated, dealkylated and rearranged 17α- and 17β-hopane isomers in the C₂₇, C₂₈, C₂₉, C₃₀ and C₃₁ families were calculated using molecular mechanics (MM2) methods and, where possible, calculated equilibrium ratios of certain isomers were compared with observed ratios of isomers in thermally mature crude oil samples. Those calculated and observed ratios having similar values include: (1) the relative distributions among 17β(H)/17α(H) and 21β(H)/21α(H)-hopanes including the absence of the 17β(H),21β(H)- and 17α(H),21α(H)-hopanes; (2) the 22R/22S ratios in 30-methyl-17α-hopane and 30-methyl-17β-moretane; (3) the relative distributions among 17α(H)/17β(H)- and 21α(H)/21β(H)-28,30-bisnorhopanes and among 25,28,30-trisnorhopanes, including the relatively greater stability of 17β(H) isomers in contrast to the regular hopane series; and (4) the ratios of 28(18−17S)abeo hopanes with respect to their unrearranged counterparts including the C₂₇ compounds, Ts/Tm.  相似文献