Heavy metals and arsenic in sediments from the continental shelf of the Northern Tyrrhenian/Eastern Ligurian Seas

Arsenic, chromium, cobalt, copper, lead, nickel, vanadium and zinc distributions in surficial and core sediments of the marine basin between La Spezia and Livorno (Northern Tyrrhenian/Eastern Ligurian Seas, west-central Italy) have been investigated. Comparison of heavy metal distribution with grain size and mineralogical data allowed the identification of vast areas where the sediment fine fraction appears affected by heavy metal anthropogenic contamination. In the fine particulate As, Cr, Pb and Zn show the highest and most widespread enrichments with respect to natural background, while Cu and V have lower and more limited positive anomalies. Co and Ni distributions only exhibit few and small areas of moderate enrichment. For nearly all the analyzed elements the strongest positive anomaly is located off Livorno port, where the presence of the shallow Meloria Shoals induces slow circular water movements, which act as sediment sinks to the heavy-metal-bearing particulate. For some elements (particularly Cr), significant point anomalies also occur at the mouth of some streams, where flocculation phenomena cause near-shore deposition of contaminated silty clays.