Polychlorinated biphenyls in two salt marsh sediments of the Venice Lagoon

Abstract

Polychlorinated biphenyls (PCBs) were measured in two dated salt marsh cores of the Venice Lagoon to assess their input chronology and to evaluate the importance of atmospheric deposition as a source. Sampling sites were chosen in order to evidence the differences between areas located leeward and windward with respect to inputs originating in both the city of Venice and the industrial area. Concentrations of PCB indicators (0.13-15.6 ng g⁻¹) increased gradually from the 1930s, reached maxima from the 1950s to the late 1970s, and then decreased. PCB loadings to marshes are driven by both the atmospheric deposition and the resuspension of subtidal sediments, this latter being more important for heavier congeners. The downwind marsh recorded higher fluxes (0.06-9.72 ng cm⁻² year⁻¹) than the upwind one (0.01-0.53 ng cm⁻² year⁻¹). Recent fluxes are rather consistent with bulk deposition measurements. A higher contribution of CB-101 and CB-118 was detected in the intermediate layers of the downwind site, suggesting a different PCB source for the corresponding time interval. In the other marsh, PCBs showed a rather constant composition at all levels (mostly CB-153, CB-138 and CB-180), accounting for a regional influence. Deep layers showed an enrichment of higher chlorinated congeners at both sites, whereas recent samples conserve the patterns typical of surficial and subsurficial subtidal sediments. The scientific approach adopted in this research can be considered as a sort of methodological procedure for the determination of fluxes and pathways of PCBs through the study of marsh cores.

Polychlorinated biphenyls (PCBs) in sediments from the western Adriatic Sea: Sources, historical trends and inventories

“…Similar observations for PCB concentrations were extensively reported in previous works (e.g. Mai et al, 2005;Frignani et al, 2007;Piazza et al, 2009;Mugnai et al, 2011) and were ascribed to a number of factors, such as physical mixing of sediments, bioturbation, and/or downward migration of PCB congeners in the sediment column. Similarly to the results reported by Mai et al (2005), lowchlorinated PCBs were in general more abundant in sediments deposited before 1930 in the western Adriatic Sea, suggesting preferable post-depositional mobilization of lighter congeners.…”

“…PCB inventories in the Po River prodelta are higher than those detected in Venice Lagoon, Italy (32-80 ng cm −2 ; Mugnai et al, 2011) and in heavily polluted tropical bays in the Philippines and in the upper Gulf of Thailand (47-92 ng cm − 2 ; Kwan et al, 2014). On the other hand, PCB inventories as high as 1310 ng cm −2 were found in the Pearl River Delta, China, a well-known polluted site and active area for deposition of sediment-bound contaminants (Mai et al, 2005).…”

Recognizing different impacts of human and natural sources on the spatial distribution and temporal trends of PAHs and PCBs (including PCB-11) in sediments of the Nador Lagoon (Morocco)

“…In the same period, lower values of OC and higher values of total PAHs are observed. Contemporary total PCBs are low and start to increase just at the end of this time window, in accordance with the period of maximum PCB use that peaked in the late 1960s (Aguilar and Borrell, 2005;Mugnai et al, 2011). The most recent sediment layers of core Nad 1 (approximately from the beginning of the 21 st century, Fig.…”

The Role of Sediment Records in Environmental Forensic Studies: Two Examples from Italy of Research Approaches Developed to Address Responsibilities and Management Options

“…A series of published papers and documents issued by public authorities were reviewed in order to define the state of the art of scientific studies. References are reported in detail in [28,38,[45][46][47][48].…”

“…They are found mostly at middle to high latitudes and are common habitats in the Venice Lagoon, where they are called "barene". Among their many ecosystem services [42], Venetian salt marshes represent an important historical and scientific archive that is able to record important environmental parameters over many decades [23,47,48], when their average accretion rates are comparable to the long-term average rate of sea level rise (SLR) in the lagoon (~0.25 cm year −1 ; [23]).…”