S.P. Vriend

Alkyldibenzofurans in terrestrial rocks: influence of organic facies and maturation

Abstract Dibenzofuran (DBF), dibenzothiophene (DBT), and phenanthrene (PHE) have been determined along with their methyl derivatives (MDBFs, MDBTs, MPs) in coals, carbonaceous shales, and mudstones of Lower Cretaceous to Upper Carboniferous ages from the Elmworth gas field (Canada) and from the Sakoa (Madagascar) and Ruhr coal (Germany) basins. The samples contained mainly terrestrial organic matter with thermal maturities in the 0.7–1.9% mean vitrinite reflectance (Rr) range. The pronounced predominance of MDBFs over MDBTs in the Sakoa samples is typical of plant debris deposited in lacustrine swamp environments. Onset of intense MDBF generation occurs at fairly low rank (0.77% Rr) as indicated by elevated concentrations of 50–120 μg MDBFs/g total organic carbon (TOC). Influences of lithology, organic matter type, and maturity on distributions of the target compounds were extracted from the molecular concentration data by multivariate statistical methods, such as Principal Components Analysis (PCA) and fuzzy c-means cluster analysis with nonlinear mapping (NLM). A specific source effect on 1-MDBT concentrations suggests that lichens contributed to the senescent coal-forming forest in the Sakoa coal basin. Alkyldibenzofurans hence are potential lichen biomarkers. MDBFs can be used as maturity indicators only beyond 1.0% Rr where Ruhr coals displayed a distinct increase in the 1−/4−MDBF ratio.

The application of fuzzy c-means cluster analysis and non-linear mapping to geochemical datasets: examples from Portugal

In the interpretation of relatively small multivariate datasets, deviations from homogeneity may cause severe problems. In these cases fuzzy c-means cluster analysis (FCM) and non-linear mapping (NLM) are conceptionally suited to discern structure in the datasets. Particularly, the combined use of FCM and NLM furnishes a powerful method to find meaningful data groupings within a dataset. This is illustrated with two case studies, for water and combined water and stream sediment analyses, respectively, where FCM and NLM were applied. The results are easily related to geology, mineral occurrences and environmental factors.

Fuzzy c-means cluster analysis of early diagenetic effects on natural remanent magnetisation acquisition in a 1.1 Myr piston core from the Central Mediterranean

Abstract The influence of early diagenesis on the natural remanent magnetisation (NRM) in sediments from the Calabrian ridge (Central Mediterranean) is analysed with the help of fuzzy c-means (FCM) cluster analysis and non-linear mapping (NLM). The sediments are variably coloured: white, beige, purplish, greenish and grey layers occur with occasionally intercalated sapropels. The NRM acquired depends on both depositional conditions and diagenetic processes. To describe these, FCM was performed with χin, ARM, CaCO3, Ba, Mn and S as variables. An eight-cluster model was derived with the clusters belonging to two categories: one expressing mainly diagenetic processes, i.e. dissolution and precipitation, and the other expressing mainly depositional conditions. The impact of diagenesis on NRM acquisition is profound and not restricted to the close vicinity of the anoxic sapropelitic layers. As a consequence, the influence of diagenetic processes on the NRM should be thoroughly assessed when selecting samples, e.g. for the determination of the relative palaeointensity of the geomagnetic field. Application of multivariate classification techniques appears to be useful because it links rock magnetic parameters to the geochemical environment. In the present piston core, three short reversed geomagnetic events in the Brunhes chron are preserved and, indeed, occur in clusters expressing no or minor diagenesis. The recording of the Blake event, however, has been prevented by later precipitation of magnetite in the corresponding interval.

Trace element concentrations and stable lead isotopes in soils as tracers of lead pollution in Graft-De Rijp, the Netherlands

Abstract Graft-De Rijp is a former village of whalers, situated twenty-five kilometres north of Amsterdam, the Netherlands. Since the foundation of De Rijp in 1612 a mixture of sludge, manure and town refuse (containing Pb-based household artefacts and Pb-based building materials) was used to raise and fertilise the land. Gasworks, coal storehouses, printing works and tanneries were started in the industrial area (after 1860). Surface soils in the “old” town centre of De Rijp are highly contaminated with Pb and, to a lesser extent, with Zn, Cu and As. Stable Pb isotopes combined with statistical analysis of the chemical dataset provided a tool whereby the sources of contaminant Pb, and related heavy metals were identified. Three major sources of Pb contamination could be distinguished: (1) remnants of the “old” town (building materials such as Pb sheets, glazed roof tiles and paint), (2) coal ashes and (3) alkyl-leaded petrol. In addition, high Zn, Cu and As are strongly related to Pb pollution, which is predominantly found in the topsoil (0–0.5 m) of the “old” town centre of Graft-De Rijp.

Hydrogeochemistry of the shallow dutch groundwater: Interpretation of the National Groundwater Quality Monitoring Network

Since 1979 the Dutch National Institute of Public Health and Environmental Protection (RIVM) has been developing the Dutch Groundwater Quality Monitoring Network (LMG). This network presently consists of about 350 monitoring sites. At each site, well screens are placed at two depths: 10 and 25 m below surface level. Samples are collected every year and are analyzed for all macrochemical parameters and some trace elements. Tritium contents were measured in the first sampling round. The geochemistry of Dutch groundwater is complex, due to the different sources (seawater, surface water and rainwater), complicated hydrogeology, and human impact on flow systems and pollution. Structuring or data analysis is required for the interpretation of the large number of hydrogeochemical data from such a monitoring network. An exploratory approach is to look within the data set for homogeneous groups, each with a typical (macro)chemistry. The selection criteria for the location of the monitoring sites of the LMG are mainly based on soil type and land use, and to some extent on the hydrogeological situation. However, a classification based on the two most reliable criteria, soil type and land use, does not result in chemically distinguishable homogeneous groups or water types. Fuzzy c means clustering was successfully used to discern structure and natural groups in the LMG data for 1 year. A seven-cluster model was adopted. The number of clusters was decided heuristically with the aid of nonlinear mapping, on the basis of the geographic distribution, the hydrogeochemical interpretability, and the unimodality of the distribution of the parameters per cluster. The consistency of the model is illustrated by the reproducibility of the clusters in different years. The clusters are related to geochemical processes, natural sources, and anthropogenic input and are designated as follows: (1) “seawater” in coastal areas, (2) “desalinization” in organic-rich Holocene marine and peat deposits, (3) “surface water” for downward seeping river water or surface water near the main rivers, (4) “carbonate/reduction” in peat areas or old groundwater in seepage zones, (5) “carbonate” for carbonate-dissolving “precipitation,” (6) acid “precipitation” water in sandy topographic highs, and (7) a “polluted” cluster characterized by agricultural contaminants. Although the influence of soil type and land use is noticeable in some of the clusters, the geochemical controls, which characterize the different clusters, appear to outweigh their anticipated influence on the hydrogeochemistry on the scale of the national groundwater network. Consequently, the homogeneous groups, obtained through the cluster analysis, present a better base for further statistical and hydrogeochemical evaluation than, e.g., a stratification of the data based on soil type and land use.

Geochemical studies in the drainage basin of the Rio Vouga (Portugal): II. A model for the origin of hydrothermal water in the Vouzela region

Abstract The hydrothermal waters in the Vouzela region (Portugal) have a temperature of 68°C and are characterized by a high content of F, Li, B, bicarbonate, sulphate and silica. Ninety-three water samples, including two hydrothermal waters, were analyzed for major and trace elements in order to investigate the genesis of the hydrothermal water. In the Vouzela region two Older Hercynian Granites are exposed, the Abas Granite and the Sao Pedro do Sul Granite. The Abas Granite is intersected by the Ribama fault. Albitization is ubiquitous. Other alteration effects are tourmalinization, K-feldspathization and muscovitization. These processes and the associated Sn—W deposits were induced by the intrusion of the Younger Viseu Granite. In the present situation rainwater penetrates into the Abas Granite especially via the Ribama fault and the greisenization zone. It becomes part of a hydrothermal system, leaches Li, F, B and silica, and rises via the Termas fault in the hydrothermal springs of Termas de Sao Pedro do Sul. Geothermal equilibrium calculations yield a temperature of 205 ± 10°C for the thermal reservoir. The percentage of mixing with cold groundwater near the surface in the circulation system is estimated at 73%. The circulation system is possibly maintained by the heat generated by the decay of U, Th, K and their daughter products, elements which are encountered in extremely high concentrations in the Sao Pedro do Sul Granite.

Hydrothermal processes and shifting element association patterns in the W—Sn enriched granite of Regoufe, Portugal

Abstract Combined research in geochemistry and mineral chemistry of the hydrothermally altered W-Sn specialized granite of Regoufe and its derivatives in Portugal was undertaken to gain insight in the mineralogical changes associated with hydrothermal processes within a single granite cupola. Over 1000 unpolished rock sections were analyzed by automated X-ray fluorescence spectrometry (XRF). On the basis of the XRF data, a small number of these same sections was selected for investigation by electron probe microanalysis. The study focuses on fourteen elements of interest that are measurable with the chosen techniques. Major pervasive alteration within the Regoufe granite is virtually contemporaneous with mineralization in the form of Sn- or W-bearing quartz veins. Two phases of hydrothermal activity are discerned, characterized by different element associations. Fluids of the first phase were especially rich in Sn, Cs and F, whereas the second phase was marked by a W-Ta-Nb-Rb association and presumably carried less F. Phosphorus probably was an important fluid component in both phases. The fluids are inferred to have fractionated from a related granitic magma at depth. Tin, W, Nb and Ta are mainly found as substitutions or inclusions in biotite in the least altered part of the Regoufe granite. Tantalo-niobian rutile is an important control for the distribution of Nb. Tin occurs in rutile and rarely as cassiterite. Muscovitization caused leaching of Ti and Zr from the granite. Tin, supplied or mobilized by the hydrothermal fluids, behaves differently from W, Nb and Ta. In the most altered rocks, muscovite hosts significant amounts of Sn. Whereas Sn is still related to Cs and Ti, elements that probably represent altered biotite, W, Ta and Nb are related to newly formed Rb-rich muscovite. Columbitetantalite was detected embedded in late muscovite. In contrast to Sn, the fluid-supplied W was predominantly deposited as wolframite in quartz veins and the altered granite is not enriched in W compared to the relatively unaltered rocks. Strontium is preferentially hosted by K-feldspar in the least altered granite; Ca in this rock is still partly contained in albite. With increasing albitization and muscovitization, Sr and Ca were released and are partly bound in newly formed apatite. The primary magmatic apatites have near-ideal formula compositions, but mobilization of P during hydrothermal activity resulted in the formation of Mn-rich apatite in all parts of the granite, and Sr- and probably Li-rich varieties in the most altered rocks. Eosphorite, and scorodite as the oxidation product of arsenopyrite, were also formed as a result of P mobilization. In the least altered rocks, Cs is mainly contained in biotite. In the most altered granite and aplitic rocks, enrichment of Cs and Rb is evenly distributed over K-feldspar and micas. The processes that lead to increased Rb are partly independent of Cs enrichment, and apparently related to the W-Nb-Ta mineralization event, separate from the preceding Sn mineralization.

Assessing environmental soil quality in rural areas : A base line study in the province of Zeeland, the Netherlands and reflections on soil monitoring network designs.

A base line study into the environmental quality of soils in the rural areas of the province of Zeeland, the Netherlands, was performed. The polder-landscape in this area was developed in a complex history of floodings and land-reclamation. Samples from 67 sites, at a density of roughly one per 25 km2, were analyzed for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in addition to a physicochemical characterization by pH(KCl), dry solids, organic matter, and clay content. At about 2/3 of the sites samples were taken at more than one depth. Fluoride and pesticides were determined in partly overlapping selections of 30 samples. Four land use classes were distinguished (arable land, grass land, orchards, uncultivated), and samples were labelled by region within the province. Data evaluation was aided by a recursive statistical approach, whereby statistical tests confirm and strengthen geochemical reasoning. Single- and multivariate statistics were used both as exploratory tools and as a measure of significance and relevance of conditions and processes. In general the environmental quality of the soils is satisfactory. Exceedence of the legal standards for natural background values at more than one site occurs for Cd, Cu, Hg and the pesticides DDT/DDE, dieldrin and HCH, at most by a factor of three. High levels of Hg appear related to arable land use; enhanced levels of Cu are found in orchards. High Cd levels primarily seem to follow a regional or geological pattern; yet, a relation with arable land use and clayey soils cannot be excluded. Pesticides are not detected in grass land, incidence is highest in orchards as well as in uncultivated areas. DDT levels appear to be generally inherited from the past. Variation in soil type as described by the macro physico-chemical characteristics is essential in explaining the variation in concentration level of the potential contaminants. Variations with depth also appear largely related to concurrent variation in soil properties. For As redox conditions and hydrological regime seem of importance, in addition to the geologic history. The influence of atmospheric input is inferred for Pb. The available data do not fully resolve the causes for the regional pattern that remains when the influences of soil type, geology, and land use have been taken into account. In addition to current concentration levels, the base line study offers general insight as to what degree variations in potential contaminants are of natural or anthropogenic origin. A succession of similar studies at suitable time intervals, each with a new selection of sampling sites, may constitute an evolving, flexible monitoring system. When putting up a monitoring system, authorities should weigh the advantages and disadvantages of a network composed of fixed sites against this alternative.

Environmental Monitoring in The Netherlands: Past Developments and Future Challenges

During the past three decades environmental monitoringsystems covering an immense variety of environmentalproblems emerged rapidly throughout the world. In The Netherlands the entire spectrum of monitoring systemsis present. Their development is especially interesting because of the Dutch complex environmental landscape: a result of the combination of a natural setting with a high small-scale variation and an intense use of the available space by both industry and agriculture. This necessitates a well balanced environmental policy wherein monitoring ofboth environmental compartments and environmental policy itself plays an important role. In this article we focus on abiotic systems, whereby the development of monitoring will be related to that of environmental policy in general. Some general lines emerge: from quantity towards quality, from single pollutants towards environmentally harmful processes as a whole, and from a focus on human health and safety towards integrated environmental management. Because The Netherlands is a highly organized and highly educatedsociety, reacting fast and flexible to new problems, this progression has happened quickly. However, still much remains to be desired and flexibility not necessarily guarantees optimal routes of development. Paramount is the development of sophisticated and robust monitoring systems that truly support integrated environmental management. This asks forclear objectives based on solid scientific insights.

Future trends, detectable by soil monitoring networks?

Abstract Recently some networks for monitoring the soil quality have enriched the world of environmental quality assessment. Formerly such networks were considered not worthwhile because the spatial variability of the soil compartment was regarded too large to detect trends in soil quality. However, research suggested that with a statistically sound network design it should be possible to detect relevant trends. As a result, national and provincial authorities in the Netherlands began to set up soil monitoring networks in the early 1990s. These networks cover the rural areas and mainly focus on three environmental aspects of the soil, namely: spread of contaminants (heavy metals, pesticides, PCB, etc.), and eutrophication and acidification. The goals are the assessment of the current soil quality of rural areas and the development of this quality. An evaluation of the first 5 years of monitoring yields much useful information. Naturally, after the evaluation of the first results, optimization of the organization and design of these networks must be considered. Topics discussed in this paper include sampling technique, sampling design and the maintenance of sample archives. Topics of a different category are the concept of homogeneous subregions, the idea of fixed monitoring locations versus a flexible network, seasonal variation and its influence on monitoring, and finally the choice of measured parameters.