Institute of Mineralogy, Freiberg University of Mining and Technology

Brennhausgasse 14, D-09596 Freiberg/Saxony, Germany

submitted to Mineralium Deposita - March 1991

- Analysis of element speciation (form of chemical bindings): The determination of element speciation is a promising method, because the anthropo- genically emitted elements may have special chemical binding forms. It needs of course special analytical methods and equipments which require a large amount of research and development work.
- The investigation of selected soil profiles, which are characteristic and representative for a large area: The aim of this method is the detection of transport currents and the dynamics of trace elements in soils. This relatively expensive method does not allow widespread application.
- Univariate statistical comparison of element contents in top and sub-soils: This method is a simplification of method No.2, but it fails in areas with strong interactions of complex parameters. A further method - used the first time in such a case study -is the mathematical differentiation by application of multivariate statistics.

- Geogenic and anthropogenic anomalies are different in terms of their localities; they are distinguished by their spectrum of anomalous element contents. The statistical differentiation succeeds in producing a two-dimensional presentation of univariate data (e.g. z-scores), mostly by using cluster-points or factor-score maps. The interpretation of the resulting associations can be done on the basis of typical anomalous element spectrums.
- There is a local differentiation, but the anomalous element spectrum is similar so that statistical differentiation can be accomplished by the same method. For the interpretation of associations a-priori-knowledge is necessary (ore veins, man-made disposals etc.). Nevertheless the associations are not obvious in all cases.
- There are complex, locally superimposed anomalies of different genesis. Such anomalies are characterized by a uniform factor and consequently by the same class of cluster analysis. The explanation of anomaly reasons is possible only when they are characterized by different element associations (RENTZSCH et al. [1985]).
- There is a superimposition of complex anomalies with similar geogenic and anthropogenic element associations. This case has happened in the investigated area with simultaneous non-ferrous metals mining and metallurgy, but it occurs also in highly urbanized areas (WOPENKA [1981]).

Ci = concentration of element i in the analyzed sample mk = influence of source k n = number of samples xik = concentration of element i formed by source kThe equation for the special case of a superimposition of anomalies formed by veins and metallurgical emissions could be:

This model drastically simplifies the anthropogenic and geogenic relations. Also, the geogenic and the anthropogenic components could be subdivided into more detailed factors with different influences of the source and different element relations. It cannot be assumed that the element ratio of one source is equal over the whole area and time-independent. Related results were obtained by KLUGE [1985] from the investigation of aerosols. The following reasons can be considered for anthropogenic sources:

- different transportation distances of particular phases
- production-based time-related changes of the emission spectrum
- unification of emissions of different sources in the aerosols
- different fixation and dispersion of elements under different physico-chemical conditions

i=1,2,...,m j=1,2,...,m zij : standardized measuring value for feature i on sample j ail : factor loading of feature i on factor l plj : estimated value of factor l on sample j r : number of mathematically determined factors (from ÜBERLA [1971])The standardized values (z-scores) used as target value of (3) represent quantitative values reproducible for the starting data. In spite of the similarity of this estimation with the method of element balances, there is a fundamental difference. Instead of element concentration relations (xik in (1)) the factor loadings ail represent only correlation coefficients. The factor values plj differ from source influences mk first because of their vectorial behavior and secondly because of their relationship to concentration relations. This has the following consequences:

- Quantitative conclusions about the element spectrum cannot be drawn by factor analysis.
- The qualitative conclusions of the factor analysis concerning the characterization of trace element sources with similar element spectrum are reduced by the required single structure. Only elements with high factor loadings on one factor are stressed, which is characteristic for one, or at most two factors.
- If the same elements are characteristic for two factors then both sources show a uniform variance and cannot be distinguished.
- Should there be a relation of one (or more) features to two factors as result of factor analysis, the data set has to contain at least two features which correlate weakly with each other but have a high correlation to the common features.

- The anomaly caused by the smelters is the most powerful anomaly with a fraction of variance of 56.4%.
- The geogenically determined anomaly has a larger area than the anthropogenic area (at least 16 geogenically determined anomalous samples as composed to 12 anthropogenic anomalous samples).
- The anthropogenically caused anomalies reach up to the area around the Freiberg, Muldenhütten and Halsbrücke smelters and also to the forest area in a distance of 10 km from the smelters (see fig. 3).

**tin ore concentrate/lead and noble metal scrap -> smelting ->
aerosol -> deposition in the surrounding of the smelters or recombination
from aerosols in the forests -> fixation in the soil.**

The stronger binding of Sn to the anthropogenic anomalies can also explained in such a way that Sn is a minor element of the ore deposit (only in ore veins containing stannite in the Zn- Sn-Cu succession of the kb-formation and in form of cassiterite in the Sn-W-succession (BAUMANN [1958]). Also, the migration capability of Sn is reduced because of the fixation as cassiterite (SnO2). From the tin smelter Sn is emitted as SnO2. In the dust particles coming from the lead refining plants of Halsbrücke and Freiberg, SnO2 could be extracted as well (VOLAND et al.[1989]). SnO2 settles in the anomalous range and is enriched because of its low mobility in the top-soil. 4. Zinc is generally enriched in the atmosphere and with an atmospheric interference factor of 23 it is determined as obviously anthropogenic (VOLAND [1987]). Additionally the zinc and sulfuric acid production emits ZnO (VOLAND et al.[1987]). In comparison to Pb and Ag the zinc smelter has existed in Freiberg for a short period (direct smelting in Freiberg since 1886, VOLAND [1984]). For the soils above the ore deposit the anthropogenic zinc impact plays a minor role. The higher mobility of zinc from this deposit has a higher level of influence. A high zinc content shows most of all mineralization caused anomalies. In table 3 it is shown how an overweight or a superimposition of anthropogenic and geogenic influences bear upon the concrete measuring values of selected samples. It is evident that connections such as the distance to the emittents or the location of ore veins are reflected in factor values.

KLUGE, A.: Entwicklung von Rechnerprogrammen zur mathematischen Behandlung geochemischer Daten.- Freiberg: Bergakademie, Skt. Geow., Studienarbeit, 1988.

RENTZSCH, J.; SCHULZE, W.; BIRKE, M.; MÜLLER, H.; EICHBERG, M.; PILLATZKE, L.: Geochemische Prospektion in anthropogen beeinflußten Gebieten. - In: Z. angew. Geol., Berlin: 31 (1985) 12.- S. 290-295.

STORM, R.: Wahrscheinlichkeitsrechnung, mathematische Statistik und statistische Qualitätskontrolle.- 8.verb. Aufl. - Leipzig: VEB Fachbuchverlag 1986.

ÜBERLA, K.: Faktorenanalyse: Eine systematische Einführung für Psychologen, Mediziner, Wirtschafts- und Sozialwissenschaftler. -2. Auflage - Berlin - Heidelberg - New York: Springer Verlag 1971.

VOLAND, B.: Schwermetallemissionen der Hüttenindustrie.- In: Spurenelemente in der Umwelt/ Fiedler H. J. und Rösler H.J. - Jena: VEB Gustav Fischer Verlag 1987, S.130-135.

VOLAND, B.: Charakter und Genese anthropogener Veränderungen der Geochemie der Landschaft: Ein Beitrag zur Umweltgeochemie.- Freiberg: Bergakademie, Diss. B 1984.

VOLAND, B.; SCHLENKER, U.; KLUGE, A.: Multivariate Methoden in der Umweltgeochemie.- Freiberg, Vortrag auf dem XL. Berg- u. Hüttenmänn. Tag Freiberg 1989.

WAGENBRETH, O.; WÄCHTLER, E.: Der Freiberger Bergbau - Technische Denkmale und Geschichte.- VEB Deutscher Verlag für Grundstoffindustrie.- 2. Auflage, Leipzig 1988

WOPENKA, B.: Mathematische Methoden zur Erfassung atmosphärischer Aerosolquellen.- Wien: TU, IAC 1981.