Geochemical Characterization of Sedimentary Organic-matter By Means of Pyrolysis Kinetic-parameters

A new means to classify organic matter in rock samples using kinetic parameters is described. Kinetic parameters are computed for Rock-Eval comparative pyrolysis curves, using a single heating rate experiment. The kinetic parameters are computed by an improved Freeman-Carroll method, assuming an overall nth-order reaction. Kinetic parameters are used for characterizing the type and maturity of sedimentary organic matter. For kerogens, the kinetic parameters are obtained on extracted-rock samples. They provide a complementary determination of organic matter type, by using the S2 peak shape which is not described by the classical Rock-Eval parameters. For resins + asphaltenes, the kinetic parameters are computed on the S2' pyrolysis curve obtained by comparative pyrolysis. They allow the determination of the type of kerogen from which they were derived and also their maturity level. The kinetic characterization can be applied directly to current Rock-Eval analysis and used in routine analysis, without changing the standard procedures but care should be taken for bitumen rich samples

Comparative Rock-eval Pyrolysis As An Improved Tool for Sedimentary Organic-matter Analysis

An improved Rock-Eval pyrolysis method is described for the global and exhaustive characterization of kerogen and bitumen in rock samples. Comparative pyrolysis is derived from the original Rock-Eval method of Espitalie et al., it overcomes some of its inadequacies and allows a better exploitation of the pyrolysis data. This new pyrolysis method is proposed mainly for routine analysis of bitumen in rock samples, using a double analysis of each sample (on whole rock and extracted rock). The difference between these two pyrolysis curves corresponds to the bitumen pyrolysis curve and is used for estimating the total bitumen content. The bitumen yield obtained in comparative pryolysis as a good correlation with the bitumen yield obtained by the standard solvent extraction method with, however, some limitations due to the "mineral matrix effect". The bitumen pyrolysis curve is further subdivided into three fractions, which allow a quick and easy typing of bitumen products. This method has been successfully applied to basin analysis

High resolution mapping of soil geochemistry at a regional scale (Wallonia, South Belgium)

In many countries, government agencies rely on soil maps of trace metal background concentrations to implement soil protection policies. In Wallonia (South Belgium), regional regulation requires extremely detailed background concentration maps. The main obstacle to obtain these maps are the large variations in local background concentrations over short distances, mainly due to the high diversity of soil parent materials, and the atmospheric deposition of pollutants around former base metal smelters. Here we outline the developed methodology and we present an example of the achieved geochemical maps at land parcel scale. The methodology established for the geochemical mapping of soils involves three steps. In the first step, we divided the Wallonia (17,000 km²) in pedogeochemical units of soil based on (1) the soil map of the Wallonia (1:20,000), (2) geological maps (1:40,000 and 1:25,000), and (3) literature data and surveys results about soils and geology of Wallonia. In the second step, we gathered about 17,500 georeferenced soil geochemical data from environmental surveys (that we carried out) or from regulatory analyses (required for agricultural use of sludge from sewage plants). On the last step, we drew the maps by using geostatistical model based on the map of the pedogeochemical soil units and the georeferenced trace metals analyses. The resulting maps show that Wallonia has higher Ni background concentration in soil than average values in Europe (according to the values of Geochemical Atlas of Europe), principally because of elevated geogenic background levels. Also, higher Zn and Cd values are found, principally due to atmospheric deposition of pollutants originating from former base metal smelters. Thanks to their resolution, the maps make it possible to predict, for instance, the risk of exceeding threshold metal concentrations in any particular land parcel in Wallonia

Assessing the usability of geochemical data originating from multiple databases for mapping the background concentration of metal in soil at regional scale

When undertaking a mapping of trace metal concentrations in the soil at the regional level, it is often found that several databases already exist. These databases, usually quite large, were obtained for instance because of an environmental protection regulation which requested to perform soil analyses or in the course of geochemical characterization surveys. The use of all the available databases is often a necessity if one has to provide high resolution maps of the pedogeochemical background. However, analyses from these geochemical databases were generally carried out by different laboratories at different periods of time. Although these laboratories are required to follow strict protocols and quality control procedures, the precision and the accuracy of a particular laboratory can vary in time. This can be due to modifications regarding the analytical equipment, the analytical procedure or the analyst. In addition, there may also be interlaboratory biases. Exploiting multi-laboratory geochemical databases can therefore be a tricky task. Here we outline a generic procedure and caution rules that proved to be useful for this purpose. The procedure consists in two sets of checks: (1) relevance checks, and (2) accuracy checks. The latter also comprises the correction of the dataset, if needed. The checks for relevance pertain to the analytical protocol, the georeferencing, the temporal variability, the spatial structure and the presence of censored values. The checks for accuracy involve testing the existence of interlaboratory bias by a method that takes into account to the geochemical characteristics of the study area. An interlaboratory bias correction method is proposed and discussed. The procedure is illustrated with a soil geochemical database of about 17.000 georeferenced analyses of trace metal elements carried out by 13 different laboratories in Wallonia (South Belgium). The cases of Cd (atmospheric deposition), Ni (geogenic origin) and Zn (both origins) are discussed

POLLUSOL 2 project: large scale investigation of soil-to-plant and soil-to-human exposition pathways in urban areas near industry in Wallonia

Since 2007, SPAQuE, with the collaboration of four universities in Belgium (UCL-ELIE, UMONS, Ulg-GxABT and Ulg-Aquapôle), has investigated urban areas near industry in Wallonia (Belgium), collecting data in residential gardens, woodland and cultivated or grazing areas. The objectives of the project were to define urban background soil quality values and to investigate soil-to-plant and soil-to-human exposition pathways. 1126 soil samples, 1341 vegetables and 435 groundwater samples were collected and analyzed. Seventeen inorganic pollutants, 33 organic pollutants, 6 soil parameters and 5 major elements were analyzed in soil, 16 inorganic and 16 organic pollutants in vegetables and 20 inorganic pollutants and 74 organic compounds in groundwater. Furthermore, several laboratory experiments were carried out by the universities: - To study human bioaccessibility via the gastrointestinal tract, the Unified BARGE (Bioaccessibility Research Group of Europe) Method was applied to 307 soils samples for 8 inorganic pollutants; - To estimate the soil-to-plant transfer, several chemical extractives were tested: 480 soil samples with CaCl2 and 126 samples with EDTA, DPTA and Mehlich 3 method; - To develop an identification key, 96 samples of slag were analyzed by x-ray. The collected data were used to: - Map pollutants background concentrations in soils and groundwater ; - Develop tools designed to provide a better estimation of soil-to-plant, soil-to-human and soil-to-water transfers ; - Assess the human health exposure level. The POLLUSOL 2 results will be an important asset for the Walloon administration when implementing the legislation about potentially contaminated sites. The presentation will focus on the POLLUSOL 2 results regarding the soil-to-plant and soil-to-human transfers, and their impact on risk assessment studies

Mapping the soil metal No Effect Concentration for terrestrial organisms in European countries and comparison to national soil policies thresholds

High levels of metal concentrations in soils constitute a threat to terrestrial organisms leading possibly to a loss of biodiversity and/or soil functions. This is why most European countries have adopted soil protection policies each containing soil threshold values representing a limit above which remediation interventions will be possibly required. The toxicity of metals in soils has been assessed with the Predicted No Effect Concentration (PNEC) calculator methodology. This approach relies on chronic toxicity data for terrestrial organisms and Ageing/Leaching factors which take into account soil parameters such as organic matter content, clay content, pH and cation exchange capacity. The aim of this study is to map the PNEC in European countries in order to compare their soil threshold values with the observed PNEC values. The soil parameter dataset used for computing the PNEC is the Lucas Topsoil Dataset, which includes 20 000 soils parameter analyses similarly spatially sampled across Europe. Here we present maps and comparison results for Cu and Zn. The resulting maps show that the PNEC exhibits strong variations across Europe. This map allows to compare the level of the soil threshold values for each country with the observed distribution of PNEC. This approach highlights differences in soil environmental conservation level among the compared countries. Although it takes into account only the soil ecosystem receptors, this work provides a first approach toward consistent soil threshold values across Europe

Mapping the effect of soil metal concentration on terrestrial organisms at regional scale (Wallonia - Belgium)

High levels of metal concentrations in soils constitute a threat to terrestrial organisms leading possibly to a loss of biodiversity and/or soil functions. Ageing/Leaching factors and soil parameters such as organic matter content, clay content, pH and clay content are known to in uence the toxicity of the soil metal content. For years Wallonia has collected a large amount of georeferenced soil analyses and was able to constitute a database that covers the whole region with high spatial resolution. The rst aim of this study is to map the eect of metals on terrestrial organisms taking into account soil parameters as well as Ageing/Leaching factors. This is done by computing the species sensitivity distribution on each point of a grid of 70 000 points using the PNEC Calculator methodology, which relies on chronic toxicity data for terrestrial organisms and Ageing/Leaching factors derived from EU REACH reports. The second aim of this study is to compare the sensitivity distribution function to the predicted concentration of metals at each point of the grid to compute the potentially aected fraction (PAF) of organisms. The PAF due to zinc and copper concen- trations have been computed. For copper, the PAF is below 5% everywhere in Wallonia. For zinc, the PAF is higher than 10% in the Liege are

Using soil geochemical data as environmental records of past industrial activities(Wallonia, South Belgium)

Wallonia (South Belgium) has had an intense industrial activity during the 19th century including iron mills, steelmaking blast furnaces and non-ferrous metals smelting plants (Pb,Zn), which durably impacted soils pollutant concentrations on large areas. Here we outline the results of the modeling of the impact of the major former industrial plants on metal soil concentration at a regional scale. The methodology established for assessing the impact of each industrial plant involves three steps. In the first step, the pollutant dispersion from 89 former industrial plants each considered individually is modeled by a finite volume method. In the second step, the enrichment of atmospheric pollutants in 508 control points spatially distributed over Wallonia is estimated. In the last step the amount emitted by each of the industrial plants is calculated by fitting the 508 control points using a non-negative linear least squares model. For Cd, the results indicate that its presence in Wallonia soils is mainly due to atmospheric deposition originating from former base metal smelters. The methodology allow us to determine at any point of Wallonia the soil industrial plant(s)responsible for the soil Cd concentration. In the same way the total amount of Cd emitted by each industrial plant has been estimated. The results are based on strong assumptions and thereby contain uncertainties, but illustrate a promising methodology that can be used to trace the environmental impact of former industrial activities based on soil geochemical data