P.F.M. van Gaans

High-resolution landform classification using fuzzy k -means

Previous attempts to devise automated methods of landscape classification have been frustrated by computational issues related to the size of the data set and the fact that most automated classification methods create discrete classes while ‘natural’ interpreted landscape units often have overlapping property sets. Methods of fuzzy k-means have been used by other workers to overcome the problem of class overlap but their usefulness maybe reduced when data sets are large and when the data include artefacts introduced by the derivation of landform attributes from gridded digital elevation models.This paper presents ways to overcome these limitations using spatial sampling methods, statistical modelling of the derived stream topology, and fuzzy k-means using the Distance metric. Using data from Alberta, Canada, and the French pre-Alps it is shown how these methods may easily create meaningful, spatially coherent land form classes from high resolution gridded DEMs.

Continuous classification in soil survey: spatial correlation, confusion and boundaries

This article traces the development of conceptual paradigms of soil classification and mapping from the pre-1960s model of crisp classes in attribute space linked to crisply delineated mapping units in geographical space, to modern approaches using fuzzy classification and geostatistical interpolation for simultaneously handling continuous variation in both attributes and location. Continuous classification yields a separate map of class membership values for every class the dominance of any class at each location can be expressed by a confusion index, CI. If spatial correlation is strong, zones of high CI are concentrated in narrow geographical transition zones between locally dominant classes: these zones can be refined to delineate automatically classspecific boundaries. If spatial correlation in membership values is weak then broad zones of large values of CI occur all over the map. Simulation modelling and two case studies demonstrate that contiguity in geographical space is more important for successful mapping than attribute class compactness. The studies show that soil information systems must take the spatial aspects of soil variation into account; further improvements in identifying and mapping significant soil groupings should be possible using numerical models of soil processes together with the methods presented here.

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.

SULPHATE-RELATED EQUILIBRIA IN THE HYPERSALINE BRINES OF THE TYRO AND BANNOCK BASINS, EASTERN MEDITERRANEAN

Abstract The Tyro and Bannock Basins, which are depressions in the eastern Mediterranean, contain hypersaline anoxic brines. These brines are of different composition: Tyro brine is primarily an early-stage halite (NaCl) brine, whereas Bannock brine includes the more soluble ions of late-stage evaporite minerals. Accordingly, the Bannock brine contains a much greater sulphate concentration than the Tyro Brine. This difference in sulphate concentration is reflected in the concentrations of ions such as Ca, Sr and Ba, which form sparingly soluble sulphate minerals. Equilibrium calculations using the Pitzer specific ion interaction model indicate that the brines in both basins are saturated with respect to gypsum (CaSO 4 -2H 2 O) and supersaturated to saturated with respect to dolomite (CaMg(CO 3 ) 2 ). The degree of saturation with respect to dolomite is greater in the Bannock Basin than it is in the Tyro Basin. Correspondingly, recent gypsum crystals and dolomite hardgrounds have been found in the Bannock Basin but not in the Tyro Basin. The Tyro brine is homogeneous in composition, whereas the Bannock brine demonstrates a clear two-layer brine structure. At the interface of the upper and the lower brine distinct positive anomalies occur in the total alkalinity and the concentration of phosphate, and negative anomalies occur in the concentrations of Mn 2+ and the rare earth elements (REE). These anomalies and the observed association of gypsum/dolomite in the sediments are all consistent with a recent precipitation of dolomite and gypsum in the Bannock Basin. The brines in both basins are also saturated with respect to barite (BaSO 4 ). The 87 Sr/ 86 Sr and δ 34 S ratios of the Bannock brines are amazingly consistent but differ dramatically from the values for modern or Messinian-age seawater. The Sr concentration and Sr and S isotope ratios in the gypsum crystals indicate that most of these crystals have resulted from precipitation/recrystallization from the brine and not from seawater. The observed variations between crystals are thought to reflect the recrystallization of (sub-) outcropping Messinian gypsum with a low 87 Sr/ 86 Sr ratio in the presence of seawater or brine fluids and with different extents of diagenesis.

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.

WATEQX—a restructured, generalized, and extended FORTRAN 77 computer code and database format for the WATEQ aqueous chemical model for element speciation and mineral saturation, for use on personal computers or mainframes

Abstract A FORTRAN 77 program, WATEQX, is presented for the modeling of (natural) aqueous solutions from 0 to approximately 1.0 ionic strength and a temperature range primarily between 0 and 100°C. In the model the speciation of the elements in solution among their various ionic or molecular forms is calculated on the basis of equilibrium constants and the degree of saturation of relevant minerals is determined. The program is a modified version of WATEQF. The directness of former WATEQ models is combined with better facilities for update and addition (or reduction) of reactions by a generalization of the program and a restructurization of the database, which now incorporates the definition of the pertinent reactions. The database, from which a formatted file is extracted, is sustained by a commercial database program to facilitate data management. The mean salt method for the calculation of activity coefficients, based on Pitzer parameters, is added to extend the ionic strength range. The program strictly follows the ANSI standard and can run on personal computers and mainframes.

The waste sulfuric acid lake of the TiO2-plant at Armyansk, Crimea, Ukraine. Part I. Self-Sealing as an environmental protection mechanism

Abstract The TiO2-plant at Armyansk, in operation since 1969, discharges its waste sulfuric acid and other effluents into an ‘acid collector’ of 42 km2 surface area. Under the semi-arid climatic conditions, such a surface represents the equilibrium between effluent production and evaporation. In the course of its operation, the pH of the lake has slowly decreased to a value of 0.85. At the bottom of the lake a layer of natrojarosite of between 10 and 50 cm has developed, which terminates in a thin crust of Fe oxides cemented by gypsum, separating the jarosite from the underlying clay. Below this Fe crust, that acts as a perfect seal, the pH of the pore-water jumps to a value around 6.2. Heavy elements from the effluent, notably As, V and Cr, are immobilized by isomorphic substitution in the Fe crust. It is suggested that similar self-healing seals can replace conventional isolation mechanisms in disposal sites.

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.