Abstract

The Volturno River plain (Campania, Italy), is an extensive alluvial formation with large pedovariability, supporting valuable crop and livestock productions. The presence of illegal waste dumps with Potentially Toxic Elements (PTEs) could threaten both environmental safety and the agricultural activities. Research is currently underway aiming to evaluate the environmental conditions and present and potential agronomic quality of the soils. This study deals with the occurrence and distribution of Pb in soils with reference to different pedological features. An extensive survey of soil profiles and core top-subsoils was carried out. Soil genesis and evolution would appear to be affected by various, mainly natural, factors, such as the variability/dynamics of sediments connected with river digression, flow regime and flooding, but also human, through the land reclamation of marsh areas. Classified pedotypes vary from Entisols to Vertisols. The former are seen in the areas near the Volturno riverbanks — frequently rejuvenated by flooding materials — the latter in stabilized inner areas that are far from riverbed.
In the study area, several illegal waste dumps with toxic/harmful slag have been discovered causing a great stir and scaremongering and bringing the agricultural land image into disrepute. Despite this critical situation, soil Pb concentration in agricultural soils is low (range 0.4–90 mg kg⁻¹, mean value 21.8 mg kg⁻¹) consistent with the natural background, and below both reference literature and the contamination threshold (100 mg kg⁻¹) sanctioned by current laws. Our results also revealed that: i) Pb concentrations show wide spatial variability, and are randomly distributed among topsoils and subsoils; ii) Pb distribution along soil profiles is clearly irregular, linked to natural pedological heterogeneities, such as buried horizons and/or changes of soil organic matter (OM), clay and CaCO₃ contents, and, consequently, of Cation Exchange Capacity (CEC); and iii) OM and the fine-size fraction are the main natural sinks of soil Pb. The results achieved appear to refute the alarmism concerning widespread Pb contamination in agricultural soils of Volturno River basin.

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