Normal and lognormal data distribution in geochemistry: death of a myth. Consequences for the statistical treatment of geochemical and environmental data

Reimann, Clemens; Filzmoser, Peter

doi:10.1007/s002549900081

Cited by 562 publications

(260 citation statements)

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“…The concept of transforming data in order to reduce asymmetry of an empirical density distribution has been widely suggested in geochemical data analysis (Campell, 1982, andSinclair, 1983). Log-transformation of data is the most common numerical transformation used for geochemical or environmental dataset (Reimann and Filzmoser, 2000). However, in this study, the square root-transformed uni-elemental data subset better adjusted to the normal distribution compared to the log-transformation (data not shown).…”

Section: Outlier Detection and Background Determinationmentioning

confidence: 61%

Distribution and fractionation of the rare earth elements in Brazilian soils

Paye

Mello

Mascarenhas

et al. 2016

Journal of Geochemical Exploration

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The distribution and fractionation of Sc, Y and 14 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were investigated in 144 samples (topsoil and subsoil) from 88 sites distributed across Brazil. Although, a wide range of natural variability in REE content was observed, overall the REE median contents were relatively low compared with those reported in soils form other parts of the world. The REE contents in Brazilian soils showed significant correlation mainly with Fe, Mn and Ti oxides, as well as organic matter. REE distribution in soils basically depend on the parent material, while fractionation of individual REEs depend on soil characteristics that are partly influenced by pedogenic process. Soils developed from alkaline igneous rocks showed the highest average content of REEs followed by sedimentary rocks, unconsolidated clay sediments, metamorphic rocks, basic igneous rocks, unconsolidated sand and silt sediments, and acid igneous rocks. REE normalized patterns varied significantly within each geological formation, except for soils derived from alkaline igneous rocks. The greatest variations were observed in the light REEs. Graphic inspection using exploratory data analysis tools such as Q-Q normal plots and boxplots was effective to recognize patterns and identify different data groups, determine threshold values and thus define the range of the background REE variability. The data set generated in this study may be used as a preliminary reference for regulatory actions in the Brazilian environmental legislation.

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Section: Outlier Detection and Background Determinationmentioning

confidence: 61%

Distribution and fractionation of the rare earth elements in Brazilian soils

Paye

Mello

Mascarenhas

et al. 2016

Journal of Geochemical Exploration

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“…Log transformations failed to normalize data, so the Mann-Whitney nonparametric test for comparison of medians was used to assess differences between groups. For ferulic acid and caffeic acid, values that were below the range of detection were assigned a value of one half the minimum value [22].…”

Section: Discussionmentioning

confidence: 99%

Ecological and Chemotypic Analysis for Improved Growth and Management of Naturally Occurring Black Cohosh (<i>Actaea racemosa</i> L.) Populations in Western Maryland

Vickers¹,

Brosi²,

Howell³

et al. 2015

AJPS

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Black cohosh (Actaea racemosa L.) is a perennial herb native to deciduous woodlands in eastern North America with an extensive history of traditional use, most commonly for rheumatoid arthritis and female reproductive issues. Modern clinical research has maintained this herb's relevance into the 21 st century with a majority of authentic black cohosh raw material still harvested from naturally occurring populations in Appalachian woodlands for use in botanical supplements. Increased use and interest in black cohosh have led to increased wild harvesting, reports of adulteration, and stress on this important natural resource. In an effort to study this significant medicinal plant as part of an ecosystem, and to understand factors that would contribute to the more effective growth and maintenance of black cohosh, key chemical, physiological, and ecological aspects of two occurring populations in western Maryland were surveyed. Rhizomes were harvested from six populations of naturally occurring black cohosh in two state forests located in the Allegheny Plateau and Ridge and Valley physiogeographic provinces of Maryland. The concentrations of * Corresponding authors. A. Vickers et al. 3273five medicinal compounds found in black cohosh extracts, actein, 23-epi-26-deoxyactein, cafeic acid, ferulicacid, and N-methylserotonin, were compared with plant reproductive status as well as accompanying overstory and under story species, soil moisture, and soil pH at each site. Compound levels showed a complex dependence on physiography but were independent of reproductive state. The findings provide clues to guide efforts at effective growth and management of wild populations of black cohosh and other threatened medicinal plants.

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“…The performance of statistical analysis can be affected dramatically by data outliers (Reimann and Filzmoser 2000). We excluded two outliers from the raw dataset prior to statistical analysis processes, which had PAH concentrations 19 times higher than the standard deviations of the rest of samples apparently caused by local point sources rather than regional factors.…”

Section: Data Preparation and Statistical Analysismentioning

confidence: 99%

Distribution and risks of polycyclic aromatic hydrocarbons in suburban and rural soils of Beijing with various land uses

Peng

Wang

Zhao

et al. 2016

Environ Monit Assess

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We investigated the sources, distribution, and health risks of polycyclic aromatic hydrocarbons (PAHs) in soils of peri-urban Beijing. The mean concentrations of total 16 PAHs in suburban and rural soils of Beijing were 321.8 ± 408.2 and 219.2 ± 233.5 ng/g, respectively. The PAH concentrations decreased along the urban-suburban-rural gradient and varied with land use categories. The industrial areas had the highest soil PAH concentrations followed by the living areas, roadsides, green areas, and agricultural areas. The major sources of PAHs in these soils were coal and biomass combustion. Traffic emission was not the dominant source of PAHs in peri-urban Beijing. At a few sites, high soil PAH contents were caused by point sources such as iron and steel plants and a wood preservative factory. The incremental lifetime cancer risks (ILCRs) of adults and children exposed to PAHs in the soils were acceptable. However, cautions should be paid to the abandoned industrial sites, which might be converted to residential area during the urbanization process.

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Normal and lognormal data distribution in geochemistry: death of a myth. Consequences for the statistical treatment of geochemical and environmental data

Cited by 562 publications

References 0 publications

Distribution and fractionation of the rare earth elements in Brazilian soils

Distribution and fractionation of the rare earth elements in Brazilian soils

Ecological and Chemotypic Analysis for Improved Growth and Management of Naturally Occurring Black Cohosh (<i>Actaea racemosa</i> L.) Populations in Western Maryland

Distribution and risks of polycyclic aromatic hydrocarbons in suburban and rural soils of Beijing with various land uses

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Normal and lognormal data distribution in geochemistry: death of a myth. Consequences for the statistical treatment of geochemical and environmental data

Cited by 562 publications

References 0 publications

Distribution and fractionation of the rare earth elements in Brazilian soils

Distribution and fractionation of the rare earth elements in Brazilian soils

Ecological and Chemotypic Analysis for Improved Growth and Management of Naturally Occurring Black Cohosh (&lt;i&gt;Actaea racemosa&lt;/i&gt; L.) Populations in Western Maryland

Distribution and risks of polycyclic aromatic hydrocarbons in suburban and rural soils of Beijing with various land uses

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Ecological and Chemotypic Analysis for Improved Growth and Management of Naturally Occurring Black Cohosh (<i>Actaea racemosa</i> L.) Populations in Western Maryland