The geochemistry of phosphate in the Mississippi River delta

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groundwater system by means

of hydrochemical facies distribution in a regiona

Latin Hypercube Approach to Estimate Uncertainty in Ground Water Vulnerability

A methodology is proposed to quantify prediction uncertainty associated with ground water vulnerability models that were developed through an approach that coupled multivariate logistic regression with a geographic information system (GIS). This method uses Latin hypercube sampling (LHS) to illustrate the propagation of input error and estimate uncertainty associated with the logistic regression predictions of ground water vulnerability. Central to the proposed method is the assumption that prediction uncertainty in ground water vulnerability models is a function of input error propagation from uncertainty in the estimated logistic regression model coefficients (model error) and the values of explanatory variables represented in the GIS (data error). Input probability distributions that represent both model and data error sources of uncertainty were simultaneously sampled using a Latin hypercube approach with logistic regression calculations of probability of elevated nonpoint source contaminants in ground water. The resulting probability distribution represents the prediction intervals and associated uncertainty of the ground water vulnerability predictions. The method is illustrated through a ground water vulnerability assessment of the High Plains regional aquifer. Results of the LHS simulations reveal significant prediction uncertainties that vary spatially across the regional aquifer. Additionally, the proposed method enables a spatial deconstruction of the prediction uncertainty that can lead to improved prediction of ground water vulnerability

Understanding the advanced manufacturing industry's e-marketplace stakeholder requirements : a case study of the Australian tooling industry

The proliferation of low cost imports from countries such as China and India and aggregated global supply chains are threatening the viability of Australia’s $1 billion tooling industry. The industry is characterised by numerous small owner-operators and few large firms. The literature suggests that e-marketplaces may increase the industry’s efficiencies and opportunities. This study identifies the requirements of the Australian tooling industry e-marketplace through an analysis of stakeholder requirements using in-depth interviews of 35 senior managers. Findings suggest that an e-marketplace will provide members and other stakeholders with access to information storage, manipulation and delivery capacities to increase efficiencies, enhance the development of collaborative programs, and increase export opportunities

Processes Governing Alkaline Groundwater Chemistry within a Fractured Rock (Ophiolitic Mélange) Aquifer Underlying a Seasonally Inhabited Headwater Area in the Aladağlar Range (Adana, Turkey)

The aim of this study was to investigate natural and anthropogenic processes governing the chemical composition of alkaline groundwater within a fractured rock (ophiolitic mélange) aquifer underlying a seasonally inhabited headwater area in the Aladağlar Range (Adana, Turkey). In this aquifer, spatiotemporal patterns of groundwater flow and chemistry were investigated during dry (October 2011) and wet (May 2012) seasons utilizing 25 shallow hand-dug wells. In addition, representative samples of snow, rock, and soil were collected and analyzed to constrain the PHREEQC inverse geochemical models used for simulating water-rock interaction (WRI) processes. Hydrochemistry of the aquifer shows a strong interseasonal variability where Mg–HCO3 and Mg–Ca–HCO3 water types are prevalent, reflecting the influence of ophiolitic and carbonate rocks on local groundwater chemistry. R-mode factor analysis of hydrochemical data hints at geochemical processes taking place in the groundwater system, that is, WRI involving Ca- and Si-bearing phases; WRI involving amorphous oxyhydroxides and clay minerals; WRI involving Mg-bearing phases; and atmospheric/anthropogenic inputs. Results from the PHREEQC modeling suggested that hydrogeochemical evolution is governed by weathering of primary minerals (calcite, chrysotile, forsterite, and chromite), precipitation of secondary minerals (dolomite, quartz, clinochlore, and Fe/Cr oxides), atmospheric/anthropogenic inputs (halite), and seasonal dilution from recharge

Conceptual model for landfill hydrologic transport developed using chloride tracer data and dual-domain modeling

Waste-derived chloride present in a landfill cell was used as a hydrologic tracer in conjunction with a mathematical model to better elucidate landfill hydrologic dynamics for a municipal solid-waste landfill in which the cover material is significantly more permeable than the waste material. Long-term temporal chloride data from a lined landfill cell in Florida were used to calibrate a variably saturated dual-domain model (originally developed for soil-science research) to landfill hydrology and solute transport. The model successfully simulated the chloride temporal trend. The dual-domain processes were needed to simulate the long-term decline in conservative chloride concentrations. However, the temporal variations about the general trend could only be simulated accurately by considering the variations in landfill recharge. The fitted value of Darcy flux (0.274 cm/day) was less than literature values, and the dispersion coefficient (900 cm2/day) was higher than simple estimates based on heterogeneous aquifers. The other fitted parameters, first-order mass transfer coefficient (0.0018/day) and fraction of mobile water (0.22), were within the range of values reported in the literature. Model sensitivity studies were conducted to assess the relative importance of each parameter. The most sensitive parameter was recharge rate to the landfill, a factor that can be measured with the proper instrumentation. Although the model performance was not as sensitive to the values of the dual-domain parameters, inclusion of these parameters was required to accurately simulate the long-term temporal trend