Pedogeochemical mapping of Al, Ba, Pb, Ti and V in surface soils of Barcelona Province (Catalonia, NE Spain): Relationships with soil physicochemical properties

Abstract

We estimated the concentrations and distributions of Al, Ba, Pb, Ti and V in surface soils of the Barcelona Province (NE Spain). This province covers 7731 km 2. The geology is varied: granites and Paleozoic shales predominate in SE–E and Mesozoic and Cenozoic limestones, dolomites, marlstones, gypsum and sandstones in the remainder of the studied area. In all, 316 topsoil samples (0–20 cm) were collected at 5 km intervals on a regular grid. General soil properties were analyzed by standard methods. Aqua regia digests (DIN 38414-S7) of Al, Ba, Pb, Ti and V were determined by Inductively Coupled Plasma Spectrometry. Statistical data treatment was carried out using R statistical project. We applied Exploratory Data Analysis (EDA) techniques to statistically describe the data. Analytical data is represented using growing dot maps. The limits for the cartographic classes were chosen by the percentile method. We compared the behaviour of Al, Ba, Pb, Ti and V in different data sub-sets (by districts, texture, pH, organic carbon and CaCO 3). Some results are: Al mg kg − 1 min 4410, max 194,786, mean 18,146, sd 12,112, med 16,273; Ba mg kg − 1 min 7.3, max 1709, mean 128, sd 149, med 91.7; Pb mg kg − 1 min 2.8, max 486, mean 52.2, sd 46.3, med 46; Ti mg kg − 1 min 11.6, max 3540, mean 268, sd 421, med 132 and V mg kg − 1 min 2.2, max 289, mean 31.4, sd 25.7 and med 26. The highest mean values of Ba, Pb and V correspond to the Barcelonés district, which has mainly urban and industrial influences. The highest Al value is found in Garraf district, with abundant Luvisols located in karst landscape. Titanium highest mean value is found in the Maresme district, over a granitic batholite. The combination of EDA and pedogeochemical mapping is a useful tool for estimating the baseline and distribution of potentially toxic elements.