Sources analysis and health risk assessment of trace elements in urban soils of Hualpen, Chile

Urban soils are a key component of urban ecosystems as they support biodiversity, provide foundation for infrastructure and play an important role in maintaining the environmental quality, being both a sink and a source of pollutants that have an effect in human health. The objectives of this study were (1) to determine the concentrations background of As, Co, Cr, Cu, Ni, Pb, V and Zn in the urban soils of Hualpen (Chile); (2) to assess the level of contamination in the urban soil based on different pollution indices; (3) to identify natural or anthropogenic sources in order to determine a spatial pattern of the pollutants and (4) to assess the health risks of trace metals in surface soils of Hualpen. A total of 153 samples were collected from the study area as follows: 51 topsoil samples (TS) (0-10 cm), 51 subsoil samples (SS) (10-20 cm) and 51 deep soil samples (DS) (150 cm). Multivariate statistics combined with spatial analysis were implemented in order to distinguish the sources. Several simple and robust statistical methods were applied to datasets in order to explore their potential in the evaluation of a useful and robust background values. The degree of contamination along with pollution indices were also evaluated. The median soil pseudo total concentrations of the elements were as follows: As 3 mg kg(-1), Co 15 mg kg(-1), Cr 14 mg kg(-1), Cu 25 mg kg(-1), Ni 36 mg kg(-1), Pb 5 mg kg(-1), V 97 mg kg(-1) and Zn 51 mg kg(-1). Multivariate analysis suggests that Cr, Pb, V and Zn are contributed by external sources. The spatial distribution of these elements displays a spatial pattern extending along industrial environments and emission sources. While the other elements show a spatial pattern with a few anthropogenic hot spots dispersed across Hualpen, they were influenced by both anthropogenic and geogenic inputs. The estimate background values determined with the DS samples with median absolute deviation (MAD) method were for As 5 mg kg(-1), Co 20 mg kg(-1), Cr 18 mg kg(-1), Cu 33 mg kg(-1), Ni 45 mg kg(-1), Pb 3 mg kg(-1), V 108 mg kg(-1) and Zn 48 mg kg(-1). The ecological indices register a moderate to considerable contamination in some soil samples. It was noted that the soils of Hualpen pose no carcinogenic risk, neither by inhalation nor by ingestion.