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Wang X.,Chinese Academy of Geological Sciences | Wang X.,International Center on Global scale Geochemistry | Chi Q.,International Center on Global scale Geochemistry | Zhou J.,International Center on Global scale Geochemistry | And 22 more authors.
Journal of Geochemical Exploration | Year: 2015

The China Geochemical Baselines Project (CGB) was launched in 2008, and sampling was completed in 2012. Its purpose is to document the abundance and spatial distribution of chemical elements covering all of China. The database and accompanying element distribution maps represent a geochemical baseline against which future human-induced or natural chemical changes can be quantified. The sampling methodology was updated or developed for China's diverse landscape terrains of mountains, hills, plains, desert, grassland, loess and karst in order to obtain nationwide high-resolution and harmonious baseline data. Floodplain sediment or alluvial soil was used as the sample medium in plain and hilly landscape terrains of exorheic river systems in eastern China. Overbank sediment was adopted as the sampling medium in mountainous terrains of exorheic river systems in south-western China. Methods of collecting catchment basin and lake sediments were developed in desert and semi-desert terrains, respectively, in endorheic drainage systems in northern and north-western China. Two sampling sites were allocated to each CGB grid cell of 1° (long.)×40' (lat.), approximately equal to 80×80km in size. At each site, two samples were taken; one from a depth of 0-25cm and a second, deeper sample from a depth greater than 100cm or the deepest part of horizon C as possible as we can take. A total of 6617 samples from 3382 sites have been collected at 1500 CGB grid cells across the whole of China (9.6million km2), corresponding to a density of approximately one sample site per 3000km2. In addition, 11,943 rock samples have also been collected to aid in the interpretation of geogenic sources of elements. Before chemical analysis, the soil and sediment samples were sieved to <10mesh (2.0mm) and ground to <200mesh (74μm), rock samples were pulverised to <200mesh (74μm). Seventy-six chemical elements plus 5 additional chemical parameters of Fe2+, organic C, CO2, H2O+ and pH were determined under strict laboratory analytical quality control. An Internet-based software named Digital Geochemical Earth was developed for managing the database and maps. Initial results show excellent correlations of element distribution with lithology, mineral resources and mining activities, industry and urban activities, agriculture, and climate. © 2015 Elsevier B.V. Source


Wang X.,Chinese Academy of Geological Sciences | Wang X.,International Center on Global scale Geochemistry | Chi Q.,International Center on Global scale Geochemistry | Zhou J.,International Center on Global scale Geochemistry | And 22 more authors.
Journal of Geochemical Exploration | Year: 2015

The China Geochemical Baselines Project (CGB) was launched in 2008, and sampling was completed in 2012. Its purpose is to document the abundance and spatial distribution of chemical elements covering all of China. The database and accompanying element distribution maps represent a geochemical baseline against which future human-induced or natural chemical changes can be quantified. The sampling methodology was updated or developed for China's diverse landscape terrains of mountains, hills, plains, desert, grassland, loess and karst in order to obtain nationwide high-resolution and harmonious baseline data. Floodplain sediment or alluvial soil was used as the sample medium in plain and hilly landscape terrains of exorheic river systems in eastern China. Overbank sediment was adopted as the sampling medium in mountainous terrains of exorheic river systems in south-western China. Methods of collecting catchment basin and lake sediments were developed in desert and semi-desert terrains, respectively, in endorheic drainage systems in northern and north-western China. Two sampling sites were allocated to each CGB grid cell of 1° (long.)×40' (lat.), approximately equal to 80×80km in size. At each site, two samples were taken; one from a depth of 0-25cm and a second, deeper sample from a depth greater than 100cm or the deepest part of horizon C as possible as we can take. A total of 6617 samples from 3382 sites have been collected at 1500 CGB grid cells across the whole of China (9.6million km2), corresponding to a density of approximately one sample site per 3000km2. In addition, 11,943 rock samples have also been collected to aid in the interpretation of geogenic sources of elements. Before chemical analysis, the soil and sediment samples were sieved to <10mesh (2.0mm) and ground to <200mesh (74μm), rock samples were pulverised to <200mesh (74μm). Seventy-six chemical elements plus 5 additional chemical parameters of Fe2+, organic C, CO2, H2O+ and pH were determined under strict laboratory analytical quality control. An Internet-based software named Digital Geochemical Earth was developed for managing the database and maps. Initial results show excellent correlations of element distribution with lithology, mineral resources and mining activities, industry and urban activities, agriculture, and climate. © 2014 Elsevier B.V. Source


Wang X.,Chinese Academy of Geological Sciences | Wang X.,Key Laboratory of Geochemical Exploration | Wang X.,International Center on Global scale Geochemistry | Liu X.,Chinese Academy of Geological Sciences | And 19 more authors.
Journal of Geochemical Exploration | Year: 2015

The China Geochemical Baselines (CGB) project provides nation-wide catchment sediment/alluvial soil geochemical baseline data for 76 elements including Hg from 3382 top (0-25cm) and 3380 deep sediment/alluvial soil samples (under a depth of 100cm) at 3382 sampling sites, corresponding to a sampling density of about 1 site per 3000km2. Mercury was determined by cold vapour generation atomic fluorescence spectrometry (AFS) under strict quality control using field duplicates, standard reference materials and analytical replicate samples. The 25th percentile is at 13 and 11μg/kg in top and deep sediment/alluvial soil samples, respectively; these concentrations are close to the crustal abundance in China. The median Hg value is at 26 and 18μg/kg in top and deep sediment/alluvial soil samples, respectively; the 75th percentile is 56μg/kg in top and 36μg/kg in deep sediment/alluvial soil samples. Mercury concentrations at the 50th (26μgHg/kg) and 75th (56μgHg/kg) percentiles exhibit systematic enrichment in the near-surface material. The Hg distribution maps show distinct increasing trends from northern to southern and from western to eastern China, which are primarily related to the distribution of parent rocks, including rocks associated with mineral resources of Hg, Sb, Au, As, Pb-Zn, and climate, resulting in different soil types, as well as to population density with accompanying industrial development. Anomalous Hg concentrations in top sediment/alluvial soil samples above the 85th percentile (87μg/kg) occur mainly in south and south-west and sparsely in north and east China; they most likely have a dual origin, natural and human-induced, with the latter having a greater contribution because of the intense industrial activities, and particularly mercury emissions from Hg, Sb, As, Au, Pb-Zn mining, coal combustion, and production of batteries, fluorescent lamps, thermometers and cement. The spatial distribution map of Hg ratios of top to deep sediment/alluvial soil samples displays higher values, suggesting that top samples are most likely polluted from human activities in the highly populated urban areas of eastern China. About 6.86% and 3.52% of top and deep sediment/alluvial soil samples, respectively, have Hg concentrations higher than the soil contamination limit of 150μg/kg set by the National Environmental Standards for Heavy Metals of the People's Republic of China. © 2015 Elsevier B.V. Source

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