Davide A.L. Vignati

Assessment of river Po sediment quality by micropollutant analysis.

Trace metals, PCB congeners and DDT homologues were determined in composite sediment samples collected from 10 representative sites along the river Po in two separate seasons. The aim was to identify the most anthropogenically impacted areas for future monitoring programmes and to aid development of Italian sediment quality criteria. The surface samples were collected during low flow conditions. Trace metal concentrations were assayed by electrothermal (Cd, Co, Cr, Cu, Ni, Pb), flame (Fe, Mn, Zn) or hydride generation (As) atomic absorption spectrometry after microwave assisted acid digestion. Hg was determined on solid samples by automated analyser. Organic microcontaminants were determined by gas-chromatography with 63Ni electron capture detector after Soxhlet extraction. Concentrations of trace metals, total PCB and DDT homologues showed two distinct peaks at the sites immediately downstream of Turin and Milan, respectively, and in each case decreased progressively further downstream. Principal component analysis identified three major factors (from a multi-dimensional space of 35 variables) which explained 85-90% of the total observed variance. The first and second factors corresponded to anthropogenic inputs and geological factors on sediment quality; the third included seasonal processes of minor importance. Sediment quality assessment identified Cd, Cu, Hg, Pb, Zn and organic microcontaminants as posing the most serious threats to river sediment quality. A reference site within the Po basin provided useful background values. Moderate pollution by organochlorine compounds was ascribed both to local sources and to atmospheric deposition.

Chromium(VI) is more toxic than chromium(III) to freshwater algae: A paradigm to revise?

The behavior and toxicity of Cr(III) and Cr(VI) to the green algae Pseudokirchneriella subcapitata and Chlorella kessleri were studied in a standard culture medium (ISO medium) and, for P. subcapitata only, in ultrafiltered natural water enriched with all ISO components (modified ISO medium). In all solutions amended with Cr(III), initial chromium concentrations decreased by 60-90% over 72h (the duration of algal tests) indicating that protocols for testing poorly soluble substances are required to properly evaluate Cr(III) toxicity. After accounting for its behavior in test solutions, chromium(III) was 5-10 times more toxic than Cr(VI) in both media. For P. subcapitata, the average 72h EC50 of Cr(III) in ISO medium was 17.4+/-4.7 microg/L (n=9); lower than corresponding hardness-corrected Continuous Concentration Criteria of the US EPA and well within the range of Cr concentrations found in waters impacted by tannery discharges. These results follow from intrinsic chemical properties of Cr(III) in circumneutral solutions, so that the actual toxicity of Cr(III) to aquatic organisms may be generally underestimated.

The role of coarse colloids as a carrier phase for trace metals in riverine systems

Abstract. In order to better understand the role of colloids in aquatic systems, better fractionation methods of environmental samples into particulate, colloidal, and truly dissolved phase are needed. An adequate fractionation procedure involves 1) prefiltration to remove large (i.e., settling) particles and 2) ultrafiltration to separate colloids from the truly dissolved compounds. Prefiltration is most commonly accomplished using filters with 0.45 or 0.22 μm pore size, which results in the inclusion of coarse colloids (size by definition up to about 1 μm) into the particulate phase. To evaluate the possible drawbacks of such operational procedures, the trace metal fraction associated with coarse colloids (size range 0.45-1.2 μm) was quantified in a number of rivers having different biogeochemical characteristics and degree of anthropogenic impact. Al, Pb, and Ti showed a strong association with coarse colloids (often over 50% of the total filterable metal at 1.2 μm) in all rivers. Other elements (Co, Cr, Cu, Fe, Mn, Ni, U, V, and Zn) had a more variable behaviour, possibly linked to differences in conductivity, oxygen saturation, and nature of colloids (mineral, organic, or mixed) among rivers. No overall statistically significant relationships could be found between the percentage metal fractions associated with coarse colloids and master environmental variables. However, when systems where classified according to the nature of colloids, Al and Pb showed statistically significant relationships with suspended particulate matter. Significant relationships were also observed between the metal pairs Mn/Co, Mn/Cu, Mn/V, Fe/Co, and Fe/Ni. The association of trace metals with coarse colloids has important implications as to their transport, fate and bioavailability in natural systems. These findings suggest that, at least in some cases, the use of the classical size limit of 0.45 μm as a boundary between the particulate and dissolved phases should be partially reconsidered and redefined.

Lanthanide ecotoxicity: First attempt to measure environmental risk for aquatic organisms

The geochemical cycles of lanthanides are being disrupted by increasing global production and human use, but their ecotoxicity is not fully characterized. In this study, the sensitivity of Aliivibrio fischeri and Pseudokirchneriella subcapitata to lanthanides increased with atomic number, while Daphnia magna, Heterocypris incongruens, Brachionus calyciflorus and Hydra attenuata were equally sensitive to the tested elements. In some cases, a marked decrease in exposure concentrations was observed over test duration and duly considered in calculating effect concentrations and predicted no effect concentrations (PNEC) for hazard and risk assessment. Comparison of PNEC with measured environmental concentrations indicate that, for the present, environmental risks deriving from lanthanides should be limited to some hotspots (e.g., downstream of wastewater treatment plants). However, considering the increasing environmental concentrations of lanthanides, the associated risks could become higher in the future. Ecotoxicological and risk assessment studies, along with monitoring, are required for properly managing these emerging contaminants.

Ecotoxicological assessment in the rivers Rhine (The Netherlands) and Po (Italy)

Abstract This paper compares several aspects of water and sediment pollution in the Rhine and Po rivers. The data were selected from previously published material following criteria that considered natural differences between the two river basins and also differences in the experimental approaches employed. One aim of the comparison was to highlight differences in approach between the Italian and Dutch water authorities and to assess the advantages of standardising methodologies for water quality assessment between Italy, The Netherlands, and other member countries of the European Union. Water quality in the Po and the Rhine was found to be similar; levels of trace metals, with the exception of copper, were below current environmentally acceptable targets, and the toxicity of water extracts to water fleas were closely similar. The main problem in both basins was diffuse inputs of nutrients and biocides from agriculture. By contrast, there were considerable differences between the rivers in terms of sedime...

Trace element contamination in the arms of the Danube Delta (Romania/Ukraine): Current state of knowledge and future needs

This paper provides the first critical synopsis of contamination by selected trace elements in the whole Danube Delta (Romania/Ukraine) to: identify general patterns of contamination by trace elements across the Delta, provide recommendations to refine existing monitoring networks and discuss the potential toxicity of trace elements in the whole Delta. Sediment samples were collected between 2004 and 2007 in the three main branches of the Delta (Chilia, Sulina and Sfantu Gheorghe) and in the secondary delta of the Chilia branch. Samples were analyzed for trace elements (Cd, Co, Cr, Cu, Ni, Pb, V, and Zn) and TiO₂, Fe₂O₃, MnO, CaCO₃ and total organic carbon. Cluster analysis (CA) and Principal Component Analysis (PCA) showed that levels of Cd, Cu, Pb, and Zn were influenced by anthropogenic activities. At the opposite, concentrations of Cr and Ni largely originated from the weathering of rocks located in the Romanian part of the Danube catchment and naturally rich in these elements. Data analysis using Self-Organizing Maps confirmed the conclusions of CA/PCA and further detected that the contamination tended to be higher in the Chilia and Sulina arms than in the Sfantu Gheorghe arm. The potential ecological risks due to trace element contamination in the Danube Delta could be identified as moderate and localized, provided that the presence of the natural sources of Cr and Ni was properly considered. The available results suggest that monitoring sediment quality at the mouths of Sulina and Sfantu Gheorghe arms is probably enough to get a picture of the sediment quality along their entire lengths. However, a larger network of monitoring points is necessary in the Chilia and secondary Chilia delta to account for the presence of local point sources and for the more complex hydrodynamic of this part of the Danube Delta.

Bioaccumulation kinetics and effects of sediment-bound contaminants on chironomids in deep waters: new insights using a low-disturbance in situ system

Effective assessment of sediment quality and associated risks requires further integration between laboratory-based studies and field observations. Tools for in situ exposure of laboratory-reared organisms are particularly suitable for this purpose. However, available tools suffer from technical drawbacks that limit their use in deep waters and their general ability to provide results linking laboratory and field observations. To overcome these limitations, we developed a new device (Sediment–Water Interface Study System – S-WISS1) for in situ exposure of fourth instar larvae of Chironomus riparius at depths up to 18 m. S-WISS1 allows minimum alteration of the sediment natural structure (upon both deployment and recovery) and, in a way analogous to laboratory tests, repeated delivery of food doses to the in situ exposed organisms. Results obtained in situ with S-WISS1 were compared with standard laboratory tests and simple caging systems (large-mouthed bottles partly filled with sand) used as field controlks. A first series of experiments (48 h, no food addition) showed that element bioavailability to chironomids was higher in laboratory settings than on-site or in situ. A second series of experiments (96 h, food addition every 24 h) confirmed that sediments rather than overlying waters acted as the principal source of contaminants and that exposure to field sediments reduced chironomids’ growth compared with on-site controls. S-WISS1 represents a new family of in situ tools capable of combining the environmental realism associated with field monitoring with the controlled experimental conditions typical of laboratory testing.

Total and methylmercury partitioning between colloids and true solution: From case studies in sediment overlying and porewaters to a generalized model

Tangential flow ultrafiltration was used to determine the partitioning of total mercury (THg) and monomethylmercury (MMHg) between colloids and true solution in sediment overlying and porewaters collected in Lake Geneva (Switzerland and France), Venice Lagoon (Italy), and Baihua Reservoir (China). Overlying water and porewater spanned different ranges of THg and MMHg concentrations, redox conditions, and salinity. Total Hg, MMHg, and dissolved organic carbon (DOC) concentrations were measured in filter-passing (<0.45 μm), colloidal (3 kDa-0.45 μm), and truly dissolved (<3 kDa) fractions. The percentages of filterable Hg and MMHg associated with colloids (arithmetic means ±1 standard deviation [SD]) were 29 ± 11% for THg (range, 4-60%) and 44 ± 17% for MMHg (range, 15-65%). Ultrafiltration DOC mass balances were often not satisfactory. However, this was apparently without consequences on THg/MMHg fractionation, suggesting that only a part of total DOC controlled THg/MMHg partitioning in overlying water and porewater. Linear relationships existed between filter passing and truly dissolved concentrations of THg and MMHg, suggesting that mechanisms controlling their partitioning are, at least partly, similar across aquatic systems. These linear relationships could be extended to data from published studies and ultrafilterable concentrations often could be predicted, within a factor of 2, from the measurement of filter-passing ones. The possibility to easily model THg/MMHg partitioning across aquatic systems will facilitate its consideration in general biogeochemical THg/MMHg models.

Sediment Quality Assessment in the Gulf of Gdańsk (Baltic Sea) Using Complementary Lines of Evidence

Sediments from Polish coastal environments were classified by a quality assessment approach that took into account trace metal and organic micropollutant concentrations, grain-size distribution, and organic carbon content. Generally, no benthic organisms were found at sites where sediments were classified as heavily polluted. However, areas characterized by a moderate contamination showed a variable composition of the benthic community and changing bioaccumulation patterns; therefore, no single species found in the Gulf of Gdańsk could be considered representative of the whole benthic environment. Although sediment monitoring must be considered a suitable tool to detect hot-spot pollution areas in coastal and inland waters, it should be complemented by bioaccumulation measurements to evaluate the actual risk posed by contaminants to benthic organisms. This “biological information” allows a better appreciation of the real benthic infaunal community exposure to chemicals and can usefully complement the existing sediment quality guidelines.

Public health benefits and risks of fish consumption: current scientific evidence v . media coverage

OBJECTIVE To evaluate if and how the current degree of scientific uncertainty about the safety of fish consumption is incorporated at the media level. DESIGN We used a dedicated software (TalTac®) to investigate the content of 169 news articles related to ‘mercury and fish consumption’ that appeared from 1990 to 2010 in the two Italian broadsheets with the highest circulation figures, in order to identify journalistic frames used in the coverage of benefits v. risks associated with fish consumption. Hypotheses were made on how the public might change fish consumption patterns as a result of media coverage. SETTING Italy. RESULTS The two newspapers have different agendas in covering the issue. La Repubblica appears to support the view that, besides health benefits, there may be risks associated with fish consumption, while Corriere della Sera emphasizes health benefits more than possible risks. Depending on the preferred information source, the public could: (i) reduce its fish intake; (ii) increase its fish intake; or (iii) become confused about the problem and sceptical towards the media, as a result of conflicting journalistic frames. CONCLUSIONS The Italian media, in cooperation with scientists, public health nutritionists and dietitians, should place more emphasis on the existence of a few fish species with high to very high Hg levels and relatively low contents of beneficial n-3 fatty acids (e.g. swordfish and shark). This would enable consumers to make more educated purchasing decisions to maximize the benefits of n-3 intake while reducing possible risks from consuming Hg-contaminated fish.