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Notes: The thermodynamic properties of silicate minerals can be described as a linear combination of the fractional properties of their constituent polyhedra. In contrast, given the thermodynamic properties of these polyhedra, the thermodynamic properties of minerals can be estimated, where only the crystallography of the mineral needs to be known. Such estimates are especially powerful for hypothetical mineral end-members or for minerals where experimental determination of their thermodynamic properties is difficult. In this contribution the fractional enthalpy, entropy and molar volume for 35 polyhedra have been determined using weighted multiple linear regression analysis on a data set of published mineral thermodynamic properties. The large number of polyhedra determined, allows calculation of a much larger variety of phases than was previously possible and the larger set of minerals used provides more confident fractional properties. The OH-bearing minerals have been described by partial and total hydroxide coordinated components, which gives better results than previous models and precludes the need of a S–V term to improve estimates of entropy. However, the fractional thermodynamic properties only give adequate results for silicate minerals and double oxides, and should therefore not be used to estimate the properties of other minerals. The thermodynamic properties of ‘new’ minerals are calculated from a linear stoichiometric combination of their constituent polyhedra, resulting in estimates generally with associated uncertainty of 〈5%. The quality of such data appears to be of sufficient accuracy for thermodynamic modelling as shown for meta-bauxites from the Alps and the Aegean, where the effect of Zn on the P–T stability of staurolite can be both qualitatively and quantitatively reproduced.

Notes: Thermodynamic calculations in petrology are generally performed at pressures and temperatures beyond the standard state conditions. Accurate prediction of mineral equilibria therefore requires knowledge of the heat capacity, thermal expansion and compressibility for the minerals involved. Unfortunately, such data are not always available. In this contribution we present a data set to estimate the heat capacity, thermal expansion and compressibility of mineral end-members from their constituent polyhedra, based on the premise that the thermodynamic properties of minerals can be described by a linear combination of the fractional properties of their constituents. As such, only the crystallography of the phase of interest needs to be known. This approach is especially powerful for hypothetical mineral end-members and for minerals, for which the experimental determination of their thermodynamic properties is difficult. The data set consists of the properties for 35 polyhedra in the system K–Na–Ca–Li–Be–Mg–Mn–Fe–Co–Ni–Zn–Al–Ti–Si–H, determined by multiple linear regression analysis on a data set of 111 published end-member thermodynamic properties. The large number of polyhedra determined allows calculation of a much larger variety of phases than was previously possible, and the choice of constituents together with the large number of thermodynamic input data results in estimates with associated uncertainty of generally 〈5%. The quality of the data appears to be sufficiently accurate for thermodynamic modelling as demonstrated by modelling the stability of margarite in the CASH system and the position of the talc–staurolite–chloritoid–pyrope absent invariant point in the KMASH system. In both cases, our results overlap within error with published equivalents.

Notes: Regional and national ground-water monitoring networks are used to inventory and to monitor diffusive (nonpoint) sources of ground-water contamination. The Dutch National Ground Water Quality Monitoring Network (LMG) is an example of such a network, and monitors the shallow ground water of The Netherlands at two depths (10 and 25 m below land surface) in 350 wells, giving an average density of one monitoring well per 100 km2. Once water-quality changes have been observed in time and space, the regional network is less suited to the study of the detailed chemistry, dynamics, and scale of the observed changes, because of the low density of sampling points.Two important threats to the quality of ground water that were identified by the regional network were studied in greater detail by use of multilevel observation wells along cross sections parallel to the direction of ground-water flow. The first detailed study evaluates the fate of nitrate and other agricultural contaminants in a sandy aquifer recharged by precipitation. The second detailed study evaluates the effects of recharge from IJssel river water in a sandy aquifer.The precipitation-recharged section consists of two hierarchically-related ground-water flow systems. A regional-scale, relatively unpolluted system, recharged within an ice-pushed ridge by rain water, is overlain by several local-scale, agriculturally contaminated flow systems, that extend from the water table to 25 m below land surface. Locally, denitrification by organic carbon occurs in or near the unsaturated zone. Within the regional system, ground-water composition changes over a distance of 5–6 km from aerobic infiltrating rain water to sulphate-reduced, calcite-saturated rain water. In the river-water infiltration section IJssel river recharges the aquifer within a distance of much less than 1 km from the river. The main part of the section consists of local-scale agriculturally contaminated flow systems.The varying compositions of ground water are controlled by the hydrological flow patterns, the composition of the aquifer sediments (e.g., presence of carbonate, clay minerals, and organic matter) and the composition of the source water (river water, rain water, agriculturally polluted). These controlling factors locally lead to relatively rapid transitions and heterogeneity of ground-water compositions. The transition zones are considerably smaller than the density of observation wells in the Dutch ground-water monitoring network, which limits the usefulness of regional monitoring networks for identifying chemically similar hydrologic zones or for effectively evaluating physical and chemical processes that affect the water quality. Regional patterns may evolve as a result of selective placement of monitoring wells, which show a specific facet of the ground-water quality of that region.To evaluate and optimize monitoring site information and to study geochemical processes in the ground water, it is recommended that local-scale sections be added to the national monitoring network program.

Notes: Abstract Multi-element lithogeochemical surveys of aureoles surrounding tin-tungsten-bearing quartz vein systems have been utilized infrequently in exploring for these deposits. At Panasqueira, Beira Beixa, Portugal, a Wrich quartz vein mineralization occurs in the Beira schists surrounding a greisenized cupola and offers a suitable test case for such lithogeochemical studies. Therefore, shale samples were collected at a density of about 6 samples per km2. Pronounced anomalies of tin and tungsten have been detected in these samples, together with those of other elements coeval with the mineralizing processes. The lithogeochemical anomalies at the surface coincide with the extent of the main ore fields. Statistical procedures have been applied to reveal interelement relationships, and contour maps were prepared for single elements and factor scores. Trace element analysis in combination with multivariate statistical data is an effective and rapid aid in locating such mineralizations, apparently also when hidden under a schist cover.

Notes: Abstract The detection of significant (short-term) time trends is one of the major goals of ground water monitoring networks. These trends can be used to recognize active geochemical processes and potential environmental threats. This paper presents a case history of time trend analysis on macrochemical parameters of ground water quality. It shows the difficulties and traps that are generally encountered in such studies. The data used originated from the Dutch National Groundwater Quality Monitoring Network. This network is operative since 1979, and keeps track of the ground water composition at 350 locations at two depths (ca. 10 and 25 m below surface; general density, one location per 100 km2). Prior to the trend analysis the data set was divided into geochemically homogeneous groups using fuzzy c-means clustering. Each group represents a specific ground water type, characterized by a distinct source (seawater, surface water or precipitation) and a unique combination of dominant geochemical processes (e.g. mineralization of organic matter, carbonate dissolution and cation exchange). To study trends qualitatively, the concentrations of the various macro-constituents in ground water are correlated with time of sampling. The nonparametric and outlier insensitive Spearman rank correlation coefficient is computed per well screen. A frequency distribution of correlation coefficients is formed by combining the Spearman correlation coefficients of all individual wells within a homogeneous group. This distribution is tested for trends against the appropriate theoretical distribution of zero correlation by use of the Kolmogorov-Smirnov one-sample test. The type of trend is derived from the shape of the distribution. Most ground water types show statistically significant qualitative trends, of which many, however, are caused by changes in the sampling and analytical procedures over the monitoring period. After elimination of differences in limits of detection for NO3, total-P, and NH4, most trends in these compounds disappeared. In some water types trends for alkalinity, apparent trends for pH, Ec, and total-P are caused by variations in the laboratory practice, e.g. varying storage procedures, leading to erroneous analyses. Other parameters showed statistically significant trends, related to geochemical processes. The most interesting and most substantial trends are observed in the water type characterized by infiltrating rainwater with agricultural pollutants. In this water type the lowering ground water table induces lower rates of evapotranspiration, giving lower concentrations in time of conservative parameters (Cl, Na, Ca). The aerated zone is enlarged, resulting in increased oxidation of organic material, less efficient nutrient (NO3, K) uptake by plant roots, leading to increased ground water concentrations of nutrients. In other water types trends are quantitatively small. However, trends are not necessarily linear, and all should be closely monitored in future.

Notes: Abstract 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.