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On the influence of the nugget effect on the efficiency of magnetometric soil surface screening

Zawadzki Jarosław, Fabijańczyk Piotr

Ecological Chemistry and Engineering. S

2022

Vol. 29, nr 4

525--535

The paper presents selected aspects of calculations and modelling of variograms from measurements of soil surface magnetic susceptibility for rapid screening of surface soil contamination with Technogenic Magnetic Particles (TMP). In particular, the methodology of variogram analysis in the case of multiple magnetometric measurements in one measurement location with the use of the MS2D Bartington sensor was discussed. A new approach to analysing such measurements was proposed that allows determining and using the nugget effect from standard, already existing measurements. This is of key importance for the quality of spatial analyses, and thus the screening results obtained by means of field magnetometry. In the paper, it was shown, step by step, that averaging the measurements performed at one measurement point during the calculation of the empirical variograms does not result in the loss of information on spatial variability in the microscale. As it was calculated non-averaged measurements were characterised by the nugget-to-sill ratio of about 96 % which was much higher than in the case of averaged measurements (close to 0 %). A range of correlation was similar in both cases and was equal to about 300 m - 400 m. The local variogram revealed a range of correlation of about 80 cm. As a result, the screening results are more reliable than is the case with the traditional procedure. An additional advantage of the work was the performance of all calculations in free R software.

Meandry modelowania złóż – na podstawie doświadczeń i obserwacji

Naworyta W.

Górnictwo Odkrywkowe

2017

R. 58, nr 4

4--9

W artykule przedstawiono subiektywny wybór problemów związanych z procesem modelowania złóż. Omówiono istotę modelowania oraz cechy informacji geologicznej wykorzystywanej w tym procesie. Na podstawie kilku wariogramów empirycznych wskazano znaczenie identyfikacji istnienia autokorelacji parametrów złożowych i jej zasięgu dla tworzenia map izoliniowych. Przedstawiono interpretację wariancji lokalnej i jej wpływ na dokładność modelu wykonanego metodą krigingu. Poddano pod dyskusję sens tworzenia modeli trójwymiarowych dla niektórych rodzajów złóż. Zwrócono uwagę na nadmierne zaufanie użytkowników do programów komputerowych i nieumiejętność właściwego wykorzystania pełnego potencjału nowoczesnych metod modelowania.

The article presents a subjective selection of problems associated with the process of modeling the deposits. It discusses the essence of modeling and features of geological information used in this process. Based on several empirical variograms, the significance of identifying the existence of autocorrelation of deposit parameters and the autocorrelation range for the creating of contour maps was indicated. The interpretation of local variance and its impact on the accuracy of the kriging model were presented. The meaning of creating three-dimensional models for some types of deposits was discussed. Attention has been paid to excessive trust in computer programs among users and the inability to properly utilize the full potential of modern modeling methods.