Harmful Elements in Estuarine and Coastal Systems

Estuaries and coastal zones are dynamic transitional systems which provide many economic and ecological benefits to humans, but also are an ideal habitat for other organisms as well. These areas are becoming contaminated by various anthropogenic activities due to a quick economic growth and urbanization. This chapter explores the sources, chemical speciation, sediment accumulation and removal mechanisms of the harmful elements in estuarine and coastal seawaters. It also describes the effects of toxic elements on aquatic flora and fauna. Finally, the toxic element pollution of the Venice Lagoon, a transitional water body located in the northeastern part of Italy, is discussed as a case study, by presenting the procedures adopted to measure the extent of the pollution, the impacts on organisms and the restoration activities

Climate-related variations in atmospheric Sb and Tl in the EPICA Dome C ice (East Antarctica) during the past 800,000 years

A record of antimony (Sb) and thallium (Tl) from the European Project for Ice Coring in Antarctica (EPICA) Dome C Antarctic ice core provides the characteristics of climate-related natural changes in concentrations and fluxes of these toxic elements over the time period back to Marine Isotope Stage 20.2, similar to 800kyrB.P. A strong variability in concentrations and fluxes are observed for both elements, with considerably higher values during glacial maxima and lower values during intermediate and warm periods. Rock and soil dust accounts for, on average, 58% of Sb and 76% of Tl in ice during glacial maxima. This contribution remains significant during warm periods, accounting for 21% for Sb and 27% for Tl. The contribution from volcanoes appears to be very important particularly for Tl when climatic conditions become warmer, with an estimated volcanic contribution of 72% for Tl during interglacials. The sea-salt contribution is significant for Sb, particularly during intermediate climatic periods, with an average contribution of 17%. This sea-salt contribution is most likely caused by greater production of sea salt from highly saline frost flowers and relatively more efficient transport of Sb-enriched sea-ice salt from source areas on the East Antarctic Plateau. Our ice core data, along with snow data recently reported from the Antarctic snow layers at Dome Fuji, shows that the present-day Sb flux (6.6ng/m(2)/yr) is approximately double the highest natural level (2.8ng/m(2)/yr) during glacial maxima throughout the last successive eight glacial/interglacial cycles. This result indicates that human activity has induced the greatest perturbation of the atmospheric cycle of Sb ever experienced over a period of similar to 800 kyr in the most remote area on Earth

Siderophile metal fallout to Greenland from the 1991 winter eruption of Hekla (Iceland) and during the global atmospheric perturbation of Pinatubo

Ir and Pt are siderophile elements that are considered proxies of meteoric material of cosmic origin entrapped within polar ice layers. However, volcanic and anthropogenic fallouts have the potential to perturb their characteristic extraterrestrial signature even in remote polar areas. Here we show a record of Ir and Pt concentrations in snow samples collected from a 2.7 m pit, which was dug at Summit (Central Greenland), and covered five years from winter 1991 to summer 1995. A well-defined peak of Pt, and a spike of Ir, were found at the base of the snow pit record. These maxima occur in close concurrence with large concentration peaks in Al, Ag, Cd and Hg. Dating of the snow layers together with some geochemical evidence suggests that these peaks originated from the fallout to Greenland of volcanic ash emitted by the nearby Hekla volcano (Iceland), during the eruption of January-March 1991. Interestingly, an anomalous peak of methane sulfonic acid (MSA) in Greenland snow also corresponds to the Hekla ash fallout. This might point to an early biomass production in the North Atlantic Ocean during the first half of 1991, which was possibly stimulated by the fertilizing action of the Hekla ash fallout to seawater. During the following years (1992-1995) the global atmosphere was under the influence of the large perturbation produced by the eruption of Mt. Pinatubo (Philippines) in June 1991. Relatively high Ir and Pt concentrations with super-chondritic ratios are recorded especially during summer 1993. We discuss if this can be interpreted as the possible stratospheric input of Pinatubo's aerosol or fallout of extraterrestrial origin. During the same period the snow pit record was also influenced by the advection of air masses enriched in Pt with respect to Ir. One possibility is that this additional Pt contribution originated from widespread emissions into the troposphere produced by vehicles equipped with catalytic converters. In any case, Pt concentration levels found in recent Greenland snow are about two orders of magnitude lower than previously thought, pointing to a much lower anthropogenic contamination of the Arctic regions from Pt. This challenges the concept of an important hemispheric contamination of Pt from vehicles equipped with catalytic converters. © 2008