Geochemical mapping is a fundamental tool for environmental monitoring and land management. For this reason, regional-, national- and global-scale geochemical mapping projects have been carried out in various countries since the late 1960s. A high density regional stream sediment geochemical survey was carried out over an area of 4125km2 in the Romagna Apennines (Northern Apennines) by collecting 770 samples (1 sample per 5km2). The <0.180mm fraction was analysed for 30 elements by means of X-ray fluorescence spectrometry.The area has a complex geology dominated by sedimentary rocks, and characterised by various geological units, which belong to the Ligurian, Tosco-Umbrian and Padano-Adriatic palaeogeographical dominions. In the study area, the industrial sites and the largest towns are located on the plains, the agricultural areas are in the hills, and there is a wooded mountainous area in the upper reaches of the main streams.Various mapping techniques were used for presenting and interpreting the data: proportionally sized dots, Exploratory Data Analysis (EDA)-based symbols, Inverse Distance Weighted (IDW) interpolation and Sample Catchment Basin (SCB) mapping approach. Proportional dot maps indicate the lithological control of the geological units. EDA maps demonstrate that it might be easier to extract some information with relevant symbols and class divisions; moreover, the subdivision of a whole data set in separate populations, related to a specific grouping variable, highlights anomalous areas, which would not be visible in a general presentation. Finally, the comparison of IDW interpolation and SCB mapping techniques illustrates that significant anomalies related to geological and anthropogenic sources are better modelled when the geochemical landscape is represented as a discrete surface rather than a continuous surface. However, this study shows how the concentration of chemical elements cannot be presented properly with a standardised mapping technique in an area characterised by multiple factors. Indeed, the use of various mapping techniques highlights interesting features for understanding the effects of local geology or human impact. © 2014 Elsevier B.V.
Lancianese, V., Dinelli, E. (2015). Different spatial methods in regional geochemical mapping at high density sampling: An application on stream sediment of Romagna Apennines, Northern Italy. JOURNAL OF GEOCHEMICAL EXPLORATION, 154, 143-155 [10.1016/j.gexplo.2014.12.014].
Different spatial methods in regional geochemical mapping at high density sampling: An application on stream sediment of Romagna Apennines, Northern Italy
LANCIANESE, VALERIO;DINELLI, ENRICO
2015
Abstract
Geochemical mapping is a fundamental tool for environmental monitoring and land management. For this reason, regional-, national- and global-scale geochemical mapping projects have been carried out in various countries since the late 1960s. A high density regional stream sediment geochemical survey was carried out over an area of 4125km2 in the Romagna Apennines (Northern Apennines) by collecting 770 samples (1 sample per 5km2). The <0.180mm fraction was analysed for 30 elements by means of X-ray fluorescence spectrometry.The area has a complex geology dominated by sedimentary rocks, and characterised by various geological units, which belong to the Ligurian, Tosco-Umbrian and Padano-Adriatic palaeogeographical dominions. In the study area, the industrial sites and the largest towns are located on the plains, the agricultural areas are in the hills, and there is a wooded mountainous area in the upper reaches of the main streams.Various mapping techniques were used for presenting and interpreting the data: proportionally sized dots, Exploratory Data Analysis (EDA)-based symbols, Inverse Distance Weighted (IDW) interpolation and Sample Catchment Basin (SCB) mapping approach. Proportional dot maps indicate the lithological control of the geological units. EDA maps demonstrate that it might be easier to extract some information with relevant symbols and class divisions; moreover, the subdivision of a whole data set in separate populations, related to a specific grouping variable, highlights anomalous areas, which would not be visible in a general presentation. Finally, the comparison of IDW interpolation and SCB mapping techniques illustrates that significant anomalies related to geological and anthropogenic sources are better modelled when the geochemical landscape is represented as a discrete surface rather than a continuous surface. However, this study shows how the concentration of chemical elements cannot be presented properly with a standardised mapping technique in an area characterised by multiple factors. Indeed, the use of various mapping techniques highlights interesting features for understanding the effects of local geology or human impact. © 2014 Elsevier B.V.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
