The geochemical background

Commission, 2008). In this projected modification to the Directive, only 4 trace elements are listed Cd, Ni, Pb and Hg. For these elements, the values obtained in this study were compared with the maximum allowable concentrations (MAC-EQS) for inland surface waters when available (Table 4.5.2). In France, a Circulaire (2007) defines NQEp (which are the French translation of the European MAC-EQS). However, since there is still a need to evaluate the geochemical background for many trace elements in surface waters, it has to be borne in mind when comparing water quality data with NQEp values, that these are not yet the definitive values. Finally, data were compared with limits fixed for drinking waters (Decree, 2001). 

Although concentrations in soils did not exceed the geochemical background, zinc turned out to be more mobile than copper. Mobile (fraction 1) and exchangeable (fraction 2) fractions of both metals corresponded very well with each other, reflecting first of all soil texture and the clay content. However, while fractions 4 and 2 were the main fractions of copper in most soils, the predominant concentrations of zinc were found in fractions 7 and 6, in sandy soils in fractions 6 and 2. Detailed results of metal speciation are presented in Tables 6.4-6.6 (on the following pages). 

The global geochemical background and enormous industrial environmental pollution have increased, thus, there are all the bases to speak about the beginning of biogeochemical formation development which has a direct influence on the ecological system condition in general as well as on the population health. 

In order to assess natural soil geochemical background concentrations, samples were collected from various soil horizons and discrete depth intervals from hand-dug pits. A total of 72 sites were sampled during the 2007 and 2008 field seasons yielding an average density of approximately 1 site per 800 km2 that is double the nominal density of a site per 1600 km2 for the NASGLP. Samples were collected from the surface layer (0 to 5... 

In order to ensure effective land-use planning, geochemical sampling and mapping are required to identify areas where the natural background concentrations are elevated so that... 

Of the 30 lakes that were cored 9 reached geochemical background concentrations and had current concentrations and/or fluxes that are decreasing to present. Five additional lakes that did not reach geochemical background were included for comparison to current wet deposition. Linear models of recovery were estimated on the most recent decreasing trend of concentration and/or flux and by ignoring episodic or short term increases in fluxes or concentrations (Fig. 1). 

There are only about a dozen published studies on Se isotopes and only two on Cr isotopes. This chapter summarizes what has been learned thus far, and almost all of this work concentrates on aqueous reactions at earth surface temperatures. It also attempts to provide some geochemical background and reviews some relevant points from the sulfur isotope literature, which provides insight into the isotopic systematics of Se and Cr. 

The Student s t-test probability (TP) measures the geochemical contrast (essentially equivalent to precision) of an exploration method. This probability identifies the likelihood that anomalous and background concentrations, defined by a specific threshold, are derived from the same population by measuring the difference between the mean anomalous and background concentrations. The lower the TP e.g. the minimum TP for any threshold MTP), the more geochemical contrast and the more likely that random variations will not influence or change the results. 

In this chapter, the application of multifractal inverse distance weighted (MIDW) interpolation method and a fractal filtering technique, named spatial and spectral analysis or simply (S-A) method (Cheng, 2003), will be illustrated to evaluate geochemical background at the regional and local scale. For this purpose, two case studies will be discussed for two different Italian areas ... 

It is emphasized that by means of the statistical frequency analysis it is possible to separate dataset in populations, even if can be difficult to select one or two general threshold to utilize as reference to identify background values. In addition, the value distributions are not sufficient to divide the dataset into different populations, because they show an overlap, and give no idea of the spatial distribution and geometry of the geochemical anomalies. This is true both at local and regional scale. 

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