Multivariate analysis of spatial patterns: a unified approach to local and global structures

We propose a new approach to the multivariate analysis of data sets with known sampling site spatial positions. A between-sites neighbouring relationship must be derived from site positions and this relationship is introduced into the multivariate analyses through neighbouring weights (number of neighbours at each site) and through the matrix of the neighbouring graph. Eigenvector analysis methods (e.g. principal component analysis, correspondence analysis) can then be used to detect total, local and global structures. The introduction of the D-centring (centring with respect to the neighbouring weights) allows us to write a total variance decomposition into local and global components, and to propose a unified view of several methods. After a brief review of the matrix approach to this problem, we present the results obtained on both simulated and real data sets, showing how spatial structure can be detected and analysed. Freely available computer programs to perform computations and graphical displays are proposed.     

Serum concentrations of perfluorooctanesulfonate and other fluorochemicals in an elderly population from Seattle, Washington

Perfluorooctanesulfonyl fluoride (POSF, C₈F₁₇SO₂F) related-materials have been used as surfactants, paper and packaging treatments, and surface (e.g., carpet, textile, upholstery) protectants. A metabolite, perfluorooctanesulfonate (PFOS, C₈F₁₇SO₃⁻), has been identified in the serum and liver of non-occupationally exposed humans and wildlife. Because of its persistence, an important question was whether elderly humans might have higher PFOS concentrations. From a prospective study designed to examine cognitive function in the Seattle (WA) metropolitan area, blood samples were collected from 238 dementia-free subjects (ages 65–96). High-pressure liquid chromatography-electrospray tandem mass spectrometry determined seven fluorochemicals: PFOS; N-ethyl perfluorooctanesulfonamidoacetate; N-methyl perfluorooctanesulfonamidoacetate; perfluorooctanesulfonamidoacetate; perfluorooctanesulfonamide; perfluorooctanoate; and perfluorohexanesulfonate. Serum PFOS concentrations ranged from less than the lower limit of quantitation (3.4 ppb) to 175.0 ppb (geometric mean 31.0 ppb; 95% CI 28.8–33.4). An estimate of the 95% tolerance limit was 84.1 ppb (upper 95% confidence limit 104.0 ppb). Serum PFOS concentrations were slightly lower among the most elderly. There were no significant differences by sex or years residence in Seattle. The distributions of the other fluorochemicals were approximately an order of magnitude lower. Similar to other reported findings of younger adults, the geometric mean serum PFOS concentration in non-occupational adult populations likely approximates 30–40 ppb with 95% of the population’s serum PFOS concentrations below 100 ppb.     

A Parallel Computation Tool to Enable Dynamic Sensitivity and Model Performance Analysis of APEX: Evapotranspiration Modeling

Global sensitivity analysis can be used for assessing the relative importance of model parameters on model outputs. The sensitivity of parameters usually indicates a temporal variation due to variation in the environmental conditions (e.g., variation in weather or plant growth). In addition, the size of averaging window by which the outputs of a model are aggregated or averaged may impact parameter sensitivities. In this study, temporal variation of parameters sensitives, model performance, as well as the impact of the size of time‐averaging window on evapotranspiration (ET) prediction using the Agricultural Policy/Environmental eXtender (APEX) model are investigated. To achieve these goals, an open‐source package named PARAPEX was developed in R and used to perform dynamic sensitivity and model performance analysis of APEX using parallel computation. PARAPEX reduced the computation time from 5,939 to 379 s (using 20 and 1 computation nodes, respectively). The sensitivity analysis results indicated the parameters accounting for the reducing effect of plant cover on evaporation from the soil surface, the effect of soil on the plant root growth, and the effect of cycling and transformation dynamics of organic matter at the top soil layer as the top sensitive parameters based on the mean daily simulated ET and the Nash–Sutcliffe model performance measure. The dynamic performance analysis indicated poor ET predictions by APEX during the growing seasons. Editor's note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

A comparative study on arsenic and humic substances in alluvial aquifers of Bengal delta plain (NW Bangladesh), Chianan plain (SW Taiwan) and Lanyang plain (NE Taiwan): implication of arsenic mobilization mechanisms

Humic substances in groundwater and aquifer sediments from the arsenicosis and Blackfoot disease (BFD) affected areas in Bangladesh (Bengal delta plain) and Taiwan (Lanyang plain and Chianan plain) were characterized using fluorescence spectrophotometry and Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the mean concentration of As and relative intensity of fluorescent humic substances are higher in the Chianan plain groundwater than those in the Lanyang plain and Bengal delta plain groundwater. The mean As concentrations in Bengal delta plain, Chianan plain, and Lanyang plain are 50.65 μg/l (2.8–170.8 μg/l, n = 20), 393 μg/l (9–704 μg/l, n = 5), and 104.5 μg/l (2.51–543 μg/l, n = 6), respectively. Average concentrations and relative fluorescent intensity of humic substances in groundwater are 25.381 QSU (quinine standard unit) and 17.78 in the Bengal delta plain, 184.032 QSU and 128.41 in the Chianan plain, and 77.56 QSU and 53.43 in the Lanyang plain. Moreover, FT-IR analysis shows that the humic substances extracted from the Chianan plain groundwater contain phenolic, alkanes, aromatic ring and amine groups, which tend to form metal carbon bonds with As and other trace elements. By contrast, the spectra show that humic substances are largely absent from sediments and groundwater in the Bengal delta plain and Lanyang plain. The data suggest that the reductive dissolution of As-adsorbed Mn oxyhydroxides is the most probable mechanism for mobilization of As in the Bengal delta plain. However, in the Chianan plain and Lanyang plain, microbially mediated reductive dissolution of As-adsorbed amorphous/crystalline Fe oxyhydroxides in organic-rich sediments is the primary mechanism for releasing As to groundwater. High levels of As and humic substances possibly play a critical role in causing the unique BFD in the Chianan plain of SW Taiwan.     

Road safety in France: The hard path toward science-based policy

Very considerable advances have been made in road safety over the long term and especially in the recent years. This improvement was achieved in part due to the effectiveness of French decision-making system, even if it remained very perfectible. An analysis of the road safety management system is carried out in order to understand the strengths and weaknesses of the organisation of road safety in France.The organisation of road safety in France is extremely centralised. The basis of road safety policy at the national level rests on an extensive information system (covering accidents, risk exposure, speed, utilisation of mobile phones) and on analyses of road risk (the risks attributable to alcohol, speed and the use of mobile phones).This statistical information and these risk models are integrated in risk management tools such as monitoring, ranking and policing. Monitoring makes it possible to track the development of road safety, bench-marking to compare the performance of the country’s different departments with each other, and policy making to refine the details of a policy.The development of the governance of road risk is leading managers and decision-makers to perfect data-gathering procedures, standardise and simplify the analytical tools used, and broaden the range of risks covered.     

Land use and socioeconomic influences on a vulnerable freshwater resource in northern New England, United States

Land use and cover conversions as well as climatic factors drive current and future threats to freshwater systems. Research from the United States and across the globe has focused on already threatened and degraded freshwater systems, whose recovery requires significant investments. Attention must also be directed to monitoring freshwater systems that may appear robust, yet are likely to face enhanced vulnerabilities in the future due to climate and land use and cover changes. Such proactive monitoring can help identify problems early and provide potential solutions. In this study, we consider the case of Sebago Lake and its watershed in southern Maine; a region that has experienced significant population growth and development activity. Land use, socioeconomic change and water quality trends are monitored over a 20-year period using Landsat imagery, census, water quality and precipitation data. Our results indicate that Developed Land within the watershed has increased from 5.4 % of the total land area in 1987 to 8.9 % in 2009 with associated increases in population and housing activity. Sebago Lake’s water quality indicators from 1990 to 2010 show a directional trend concomitant with this change. The increase in Developed Land is likely to place additional pressures on water quality in the future. The analysis also indicates that precipitation trends play an important role in water quality variability for Sebago Lake. Predicted changes to climatic factors including enhanced spring time precipitation or earlier ice-out conditions combined with further land use change may play an influential role in determining water quality. The analysis highlights emerging areas of concern and reiterates the essential role of proactively monitoring vulnerable systems to help mitigate future threats.     

The effect of atmospheric mercury depletion events on the net deposition flux around Hudson Bay,Canada

Atmospheric Mercury Depletion Events (AMDE) occur in Arctic and Antarctic regions during polar sunrise. During AMDE, reactive gaseous Hg is rapidly formed through in-situ oxidation of gaseous Hg⁰ by halogens, notably atomic Br and radical BrO. This leads to high Hg deposition fluxes yet an unknown fraction of deposited Hg is reemitted to the atmosphere through subsequent photo-reduction, so that the net deposition flux related to AMDE is not well constrained. Here, Hg and halogens were measured in lichens hanging in tree branches around Hudson Bay where AMDE were reported. Hg concentrations are strongly correlated to halogen elements Br, Cl and I (r² of 0.91, 0.76, 0.81) and decrease with distance from Hudson Bay. We interpret this trend as the result of AMDE, supported by a 1D numerical Br and BrO oxidation model for Hg⁰. Organic carbon normalized Hg contents of down-core lake sediments reported in the literature also show a decreasing trend away from Hudson Bay. Combined observations suggest that at least 50% of Hg deposited during AMDE is reemitted to the atmosphere. Finally, the latitudinal Hg gradient observed in lake sediments suggests that AMDE were active in the Hudson Bay area during the last 90 to 200 years.     

Justice in development? An analysis of water interventions in the rural South

This paper explores a fruitful convergence between the distributive and procedural dimensions of environmental justice theory and current debates in the field of development studies over capitals and capabilities, institutions, and discourse formation to shed new light on natural resource management projects in the developing world. Specifically, we document the planning and implementation of two types of water interventions in two contrasting regions: watershed development programmes in northeast India and small reservoirs in sub‐Saharan West Africa. We find that there is a contradiction between the inherently political nature of water interventions and the fact that such projects remain grounded in apolitical, technical and managerial narratives. In contrast to the new semantic of development, this depoliticization results in the near absence of attention paid to procedural (participation and empowerment) and distributive (equity) justice concerns and in local actors having to revert to covert ways to achieve their ends. A constructive dialogue between development studies and environmental justice scholars can offer a fresh look on the society‐environment nexus in the developing world.     

Changing Species Richness and Composition in Canadian National Parks

Abstract: Canada's national parks and their surrounding areas differ markedly in size, climate, vegetation, and extent of human development. We tested the extent to which total species richness, native species richness, and the number of extirpations and introductions of terrestrial vertebrates were correlated with each of these factors. To do this, we used surveys of park fauna from the present and from the time of park establishment. Richness, extirpations, and introductions were all strongly related to climate. After we controlled for climate, smaller parks had higher rates of species loss than larger parks. Land-use patterns (forest cover and fragmentation, roads, etc.) within parks were strongly correlated with land use in the regions surrounding the parks, showing that parks have not been isolated from regional development. Richness and extirpations within parks were generally more strongly related to regional characteristics than to the characteristics of the parks themselves. Species richness and numbers of introduced species were higher in parks found in landscapes with greater fragmentation. Frequencies of extirpations were less clearly related to human-influenced habitat characteristics. Introductions and extinctions most often involved game species or species directly associated with human activities. There is little evidence of subtle ecological effects being responsible for species loss. Our results suggest that management should focus on direct human interventions, such as hunting, introduction of game species, and habitat fragmentation, in parks and surrounding areas.