Bioturbation experiments in the Venice Lagoon

Short experiments (14–21 days) were carried out during autumn 1998 and spring 1999 at one selected site of the Venice Lagoon to measure bioturbation activities and mixing rates, as well as to obtain quantitative information on benthos functionality. Fluorescent sediment particles (luminophores, 63–350 μm) were introduced as pulse inputs at the sediment surface. The concentration–depth profiles of the tracer were simulated with a new advection– diffusion–non local model applied under non-steady state conditions. This allowed the quantification of the mixing parameters associated with different mechanisms: biodiffusion (Db), bioadvection (W) and non-local mixing (Ke,z1, z2). A parameter RS (removed sediment) was also calculated to account for the flux of sediment due to nonlocal transport. Results show that bioturbation was dominated by biodiffusion in autumn and by bioadvection in spring. Mean mixing parameters Db, W, and RS changed from 3.09 to 0.87 cm2 y−1, from 0.93 to 15.50 y−1 and from 5.85 to 7.79 g cm−2 y−1, respectively

Modelling Environmental Fate and Transport of POPs and Metal Usig the Fugacity/Aquivalence approach: Two Acquatic Environments as a Case Study.

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Identifying sources and pathways of persistant organic pollutants in aquatic environments

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Historical pattern and mass balance of trace metals in sediments of the northwestern Adriatic Sea Shelf

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Metals in Sediment Cores from Nine Coastal Lagoons in Central Vietnam

Problem statement: After being dramatically hit by war events, Vietnam is presently experiencing a huge economical and social development. However, very few data, relative to pollution levels and trends, are available for the correct management of critical areas such as coastal lagoons, where many economical activities are linked to high value environmental features. Approach: A set of sediment cores from nine coastal lagoons of central Vietnam (Lang Co, Truong Giang, An Khe, Nuoc Man, Nuoc Ngot, Thi Nai, O Loan, Thuy Trieu and Dam Nai) were sampled in 2008 and analyzed to assess metal and (Al, Cd, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, V, U and Zn) and As levels and historical trends. Results: Concentrations are generally low, with the exception of As, which often exceeds ERL guidelines and Ni that does the same at O Loan. In some cases, concentrations-depth profiles account for recent increasing trends but surficial values are still low when compared to both international guidelines and polluted sediments all around the world. Sediment grain size seems to affect the depth distribution of a number of metals and when normalized to the content of silt and clay, values are particularly high at Dam Nai and Thi Nai, due to the very coarse composition of surficial sediments. Conclusion: Metal concentrations in lagoon sediments derive from the composition of rocks and soils in the watersheds. However, recent increasing trends need for further monitoring

PCDD/Fs in sediments of Central Vietnam coastal lagoons: In search of TCDD

Samples from nine Central Vietnam coastal lagoons, together with three soils and sediments collected in 24 two freshwater reservoirs of the Thua Thien-Hué province, were analysed for polychlorinated dibenzo-p- 25 dioxins and dibenzofurans (PCDD/Fs). Total concentrations are low, from 192 to 2912 pg g1 and depth 26 profiles in Tam Giang-Cau Hai (TG-CH) sediment cores show only minor changes over time in PCDD/F 27 input and composition. Octachloro dibenzo-p-dioxin (OCDD) is the prevailing congener (approximately 28 90%), indicating combustion as the main PCDD/F source to these coastal systems, whereas natural forma- 29 tion might be partly responsible for the presence at depth. 2,3,7,8-Tetrachloro dibenzo-p-dioxin (TCDD), 30 largely sprayed together with Agent Orange over the study areas during the war (1961–1971), is absent 31 or very low. This result supports the hypothesis of strong degradation soon after spraying. Multivariate 32 statistical analyses account for the presence of local, short-range sources as observed in the northern part 33 of the TG-CH lagoon

Anthropogenic trace metals in the sedimentary record of the Llobregat continental shelf and adjacent Foix Submarine Canyon (northwestern Mediterranean)

15 pages, 7 figures, 3 tablesAnthropogenic trace-metal concentrations and inventories were studied on the Llobregat continental margin, from the Llobregat river mouth to the Foix submarine canyon. A prodelta sedimentary depocentre was identified along with a previously known canyon depocentre. Significant upward increases in trace-metal contents were detected in sediment cores of the prodelta and upper part of the canyon (down to 860 m depth). Metal enrichment factors ranged between 1.8 and 10 on the continental shelf and between 1.2 and 2.7 in the submarine canyon. These metal enrichments occurred during the 20th century and can be correlated with the period of maximum increase of population and industrial activities in the Barcelona area and the consequent anthropogenic metal inputs. Maximum trace-metal enrichments are located in the prodelta depocentre and significant enrichments were also measured in the southern prodelta and in the Foix upper canyon as a consequence of efficient shelf canyon sediment and metal transfer. Deeper in the canyon, at 1370 m depth, no metal enrichments were detected, probably because of particle dispersion and dilution with uncontaminated sediment within the canyon. This study shows that, in some Mediterranean sedimentation systems, anthropogenic trace metal contamination is affecting not only the littoral and the continental shelf, but also the adjacent continental slope sediments through submarine canyonsThis work received support from the projects AMB92-0251-CO2-01 funded by the CICyT, CTM2006-06919/MAR funded by the Dirección General de Investigación and the project MAS2-CT93-0053 funded by the EUPeer reviewe

A Multidisciplinary Approach to the Study of Contaminated Coastal and Fresh Water Environments.

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Bioturbation in the Venice Lagoon: Rates and relationship to organisms

International audienceExperiments were carried out during autumn 1998 and spring 1999 at four selected sites in the Venice Lagoon in order to estimate the major bioturbation modes, and for quantitative analysis of the contribution of various taxa to these modes. Fluorescent sediment particles (63-350 μm) were supplied as a tracer pulse input at the sediment surface. Tracer depth profiles obtained after 15 and 20 days were simulated with a diffusion-advection-non-local transport model. This allowed the rates of biodiffusion (Db), bioadvection (W), and RS, a non-local transport coefficient to account for the displacement of sediment by regeneration, to be estimated. A combination of fresh water and marine organisms were responsible for the recorded sediment reworking, which was dominated by both types of non-local transports (conveying and regeneration). Considering all the sampling sites and seasons, Db ranged from 0.87 ± 0.02 to 3.17 ± 0.92 cm2 y−1, W from 0.12 ± 0.09 to 27.41 ± 2.47 cm y−1 and RS from 0.00 ± 0.00 to 5.47 ± 1.09 g cm−2 y−1 (mean ± SE, n = 3). A multiple regression analysis was applied to identify the contribution from individual species to sediment transport types. Biodiffusion resulted from the combined activity of polychaetes such as Spio decoratus and meiobenthic harpacticoïd copepods, while the polychaete Hediste diversicolor was mainly responsible for regeneration. Conveying processes were driven by another polychaete, Capitella capitata. Despite heterogeneity in the benthic community composition, biodiffusion and regeneration rates did not vary significantly between sites or season, with only bioadvection found to be higher in spring than in autumn