Application of lead isotopic methods to the study of the anthropogenic lead provenance in Spanish overbank floodplain deposits

Abstract

Changes in the principal sources of Pb in overbank sediment profiles have been documented for two Spanish areas by using Pb isotopes and Pb concentrations. These locations (Madrid and Tinto-Odiel basin) represent two of the most contaminated regions in Spain. The Community of Madrid is characterized by heavy industrial and urban activity, focused mainly in Madrid City. The Tinto-Odiel basin drains the Iberian Pyrite Belt, which hosts many polymetallic massive sulphides and is heavily affected by mining activities in their headwaters. It has been proven that the influence of anthropogenic activity is reflected in these overbank deposits by variations in Pb concentrations that, in general, correlate with shifts in the (206)Pb/(207)Pb ratio. Rivas profile (downstream of Madrid) was found to be the most anthropogenically influenced site. The sediments within this profile which were recently deposited (170 ± 40 years BP) have the least radiogenic signatures. (206)Pb/(207)Pb ratios ranged between 1.1763 and 1.1876 indicating significant contributions of anthropogenic Pb. In contrast, profiles upstream of Madrid possess an average (206)Pb/(207)Pb ratio of 1.2272. It is difficult to clearly identify the most prominent source as the sediments appear to be characterized by an input from several sources. The floodplain profiles in the Tinto-Odiel basin exhibit uniform (206)Pb/(207)Pb ratios ranging from 1.1627 (Odiel river) to 1.1665 (Tinto river). These ratios are similar to the ones possessed by sulphide ores in the area and differ from the ratios of other nonmineralized formations in the basin, indicating that mining activities are the primary, if not sole, source of Pb to the sediments.

Insights into a 20-ha multi-contaminated brownfield megasite: An environmental forensics approach

“…a common predominant Pb origin (s) for all the samples (see Table 4). Therefore, average values were used to establish comparisons with possible sources; in this regard, Adánez et al (2015) have recently reported Pb isotopic ratios in samples of the Odiel-Tinto basin in the SW of Spain that are notably similar to those measured in our study. That basin belongs to the Iberian Pyrite belt, one of the main metallogenic provinces in Europe, where pyrite and other sulphide ores have been exploited for centuries.…”

“…a Average of the 20 soil composite samples. b Data corresponding to the maximum highest Pb concentration within the 20 samples (4548 ppm).c Ranges obtained byAdánez et al (2015). dMarcoux (1998).…”