POPs in the Lagoon of Venice: budgets and pathways

Dioxins and furans (PCDD/Fs), polychlorobiphenyls (PCBs) and hexachlorobenzene (HCB) in the ecosystem of the Lagoon of Venice were studied, in order to provide a general picture of conditions in the lagoon in terms of contamination by persistent organic pollutants (POPs). We present here novel data on atmospheric deposition, water, sediment and clam samples collected in the lagoon during the period January 2001-December 2004. Atmospheric deposition was sampled monthly at six sites located both close and far from large industrial and urban sources. Water samples were collected monthly from fifteen stations, and twenty-five samples of sediments and clams (Tapes philippinarum) were collected in four areas where clams are farmed and harvested inside the lagoon. All samples were analysed for PCDD/Fs, PCBs and HCB by HRGC/HRMS in the same laboratory. All samples examined (atmospheric deposition and water) substantially confirmed the spatial pattern reported in previously published data on sediments and atmospheric deposition: the zone surrounding the Porto Marghera petrochemical plant always had the highest levels of POPs (i.e., PCDD/Fs: atmosphere approximately 6 pg of 2,3,7,8-TCDD equivalents (I-TE) m(-2)d(-1); water 0.37 pg I-TEl(-1); sediment: 300 ng kg(-1); clam 2.8 pg I-TE g(-1)), and the minima were found at points on the margins of the lagoon (PCDD/Fs: atmosphere approximately 1 pg I-TEm(-2)d(-1); water 0.05 pg I-TEl(-1); sediment: approximately 5 ng kg(-1); clam approximately 0.2 pg I-TE g(-1)). Intermediate values were often encountered in the historical city centre of Venice and in the central part of the lagoon. To confirm this, new data on correlation between levels of PCDD/F in sediments and clams are reported, both for absolute values and for the PCDD/F "fingerprint". There is always a clear fingerprinting signature (PCDF/PCDD>1) for samples collected near Porto Marghera, and the opposite (PCDF/PCDD<1) in the rest of the lagoon.     

Is the diversity of epiphytic lichens a reliable indicator of air pollution? A case study from Italy

This work provided additional information for a better interpretation of lichen diversity values in biomonitoring studies of air pollution. The effects of 12 predictive variables were estimated for the Genova province (NW Italy) by means of a non-parametric model. The diversity of epiphytic lichens was strictly correlated with mean annual rainfall and mean annual temperature. Different variables were found to affect the lichen diversity in urban vs. forested areas. In urban areas, air pollutants, mainly SO2, are still the main limiting factor, even if under ameliorating conditions this relationship becomes less significant. In forested areas, harvesting and forest fires showed a predominant effect, suggesting the need to develop a more defined sampling protocol to estimate atmospheric pollution in such ecosystems.     

Is Syllis gracilis (Polychaeta: Syllidae) a species complex? An allozyme perspective

The genetic relationships between morphologically indistinguishable marine and brackish populations of Syllis gracilis Grube, 1840 (Polychaeta: Syllidae) were studied by means of allozyme electrophoresis. Samples of S. gracilis from marine coastal and brackish-water habitats were examined for variation at 13 presumptive loci. In addition, a sample of the closely related species S. prolifera (Krohn, 1852) was analysed. Five loci were multiallelic in at least one population of S. gracilis and eight loci in S. prolifera. Low to moderate levels of within-population genetic variability were found, with average expected heterozygosity values ranging from H = 0.068 (±0.043 SE) to 0.187 (±0.069 SE) in the populations of S. gracilis; higher values were found in S. prolifera (H = 0.325 ± 0.076). The presence of various private alleles indicated a marked genetic divergence among populations of S. gracilis, with Nei's genetic distances ranging from D = 0.000 to 0.833 and a highly significant F _ST value. Furthermore, evidence for strong genetic heterogeneity between two sympatric marine populations was found. UPGMA cluster analysis and multidimensional scaling pointed out a clear genetic divergence between brackish and marine populations. At least two genetically divergent entities occurred in marine and brackish habitats. This could be due to local adaptation of individuals coming from marine populations to brackish habitats, but more presumably to the occurrence of a species complex within S. gracilis. Received: 6 June 1999 / Accepted: 7 February 2000     

Experimental analysis of open check dams and protection bars against debris flows and driftwood

Environmental Fluid Mechanics - The paper addresses the influence of intense sediment transport (bed load and debris flow) on the efficiency of the structures aimed at the interception of wood...     

Generation of PCDD/F in Fly Ash from Municipal Solid Waste Incinerators

Abstract

Fly ash from municipal solid waste incinerators (MSWIs) has been characterized in terms of polychlorinated dibenzyl-p-dioxin and polychlorinated dibenzofuran (PCDD/F) content. Increasing values of PCDD/Fs have been found to correlate with decreasing temperatures of sampling points in flue gas treatment lines of the plants, confirming other researchers’ findings about temperature as the major controlling parameter for the PCDD/F formation. Measured PCDD/F ratios show that de novo synthesis is the dominant formation mechanism. The increasing trends of particulate-bound PCDD/Fs can be explained not only through the dominant de novo synthesis process but also considering the adsorption of gaseous PCDD/Fs on fly ash deposits, even outside the typical de novo synthesis temperature ranges. The effective role of a post-combustor unit, imposed by Italian law to destroy PCDD/Fs, also needs to be carefully reconsidered.     

Chlorpyrifos residues levels in fruits and vegetables after field treatment

Chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate) was applied with three different formulations on oranges, peaches, tomatoes, wine and table grapes, and its behaviour was evaluated after field treatment. The formulations applied were emulsifiable concentrates (EC), microencapsulates (ME), and wettable granules (WG). The residues were similar in all crops studied in the EC and WG experiments, except peaches with WG treatment, the residue amount was lower than EC values. Tomatoes which were grown in greenhouse showed similar residues in all treatments just after treatment. Wine and table grapes showed different decline curves in the EC experiments ascribable to the different growing technology. Instrumental limit of determination (LOD) and limit of quantification (LOQ) for all matrices were 0.01, and 0.03 mg kg?1, respectively. Repeated treatments showed that Chlorpyrifos can accumulate leading to residue levels at the preharvest interval (PHI) over the maximum residue level (MRL), especially on oranges and peaches. Among the formulates used ME showed the higher risk of residues over the MRL at harvest.     

A decision framework for possible remediation of contaminated sediments in the River Kymijoki, Finland

Background, aim, and scope  The paper describes the spatial contamination of the River Kymijoki, South-Eastern Finland, and the coastal region of the Gulf of Finland with PCDD/Fs and mercury. The findings of ecotoxicologial and human health studies are also reported, including environmental and human risk assessments. Sediments from the River Kymijoki, draining into the Gulf of Finland, have been heavily polluted by the pulp and paper industry and by chemical industries. A wood preservative, known as Ky-5, was manufactured in the upper reaches of the river between 1940 and 1984 causing severe pollution of river sediments with polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Moreover, the sediments have been polluted with mercury (Hg) from chlor-alkali production and the use of Hg as a slimicide in pulp and paper manufacturing. Materials and methods  An extensive sediment survey was conducted as well as sediment transport modeling, toxicity screening of sediment invertebrates, and a survey of contaminant bioaccumulation in invertebrates and fish. Studies on human exposure to PCDD/Fs and the possible effects on hypermineralization of teeth as well as an epidemiological study to reveal increased cancer risk were also conducted. An assessment of the ecological and human health risks with a null hypothesis (no remediation) was undertaken. Results  The sediment survey revealed severe contamination of river and coastal sediments with PCDD/Fs and Hg. The total volume of contaminated sediments was estimated to reach 5 × 10⁶ m³ and hot spots with extremely high concentrations (max 292,000 ng g⁻¹ or 1,060 ng I-TEQ g⁻¹ d.w.) were located immediately downstream from the pollution source (approximately 90,000 m³). Sediment contamination was accompanied by changes in benthic assemblages, but direct effects were masked by many factors. The fish showed only slightly elevated PCDD/F levels in muscle, but orders of magnitude higher in the liver compared with reference freshwater sites and the Baltic Sea. The concentrations in human fat did not reveal high human exposure in the Kymijoki area in general and was lower than in sea fishermen. The relative risk for total cancer among farmers was marginally higher (RR = 1.13) among those living close to the river, compared with farmers living further away, and the possibility of increased cancer risk cannot be ruled out. A conservative risk assessment revealed that the present probability of exceeding the WHO upper exposure limit of 4 pg WHO-TEQ kg⁻¹ d⁻¹ for PCDD/Fs and DL-PCBs was 6%. The probability of exceeding the WHO limit value of 0.23 μg kg⁻¹ d⁻¹ for methyl mercury was estimated to be notably higher at 62%. Based on these studies and the estimated risks connected with different remediation techniques a general remediation plan with cost benefit analysis was generated for several sub-regions in the river. Dredging, on-site treatment, and a close disposal of the most contaminated sediments (90,000 m³) was suggested as the first phase of the remediation. The decision regarding the start of remediation will be made during autumn 2008. Conclusions  The sediments in the River Kymijoki are heavily polluted with PCDD/Fs and mercury from earlier chlorophenol, chlor-alkali, and pulp and paper manufacturing. A continuous transport of contaminants is taking place to the Gulf of Finland in the Baltic Sea. The highly increased PCDD/F and Hg levels in river sediments pose an ecotoxicological risk to benthic fauna, to fish-eating predators and probably to human health. The risks posed by mercury exceed those from PCDD/Fs and need to be evaluated for (former) chlor-alkali sites and other mercury releasing industries as one basis for remediation decision making. Recommendations and perspectives  The studies form the basis of a risk management strategy and a plan for possible remediation of contaminated sediments currently under consideration in the Southeast Finland Regional Environment Centre. It is recommended that a detailed restoration plan for the most seriously contaminated areas should be undertaken. Based on current knowledge, the restoration of the whole river is not feasible, considering the current risk caused by the contaminated sediment in the river and the costs of an extensive restoration project. The experiences gained in the present case should be utilized in the evaluation of PCDD/F- and mercury-contaminated sites in other countries. The case demonstrates that the historic reservoirs are of contemporary relevance and should be addressed, e.g., in the national implementation plans of the Stockholm Convention. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A soil sampling intercomparison exercise for the ALMERA network

Soil sampling and analysis for radionuclides after an accidental or routine release is a key factor for the dose calculation to members of the public, and for the establishment of possible countermeasures. The IAEA organized for selected laboratories of the ALMERA (Analytical Laboratories for the Measurement of Environmental Radioactivity) network a Soil Sampling Intercomparison Exercise (IAEA/SIE/01) with the objective of comparing soil sampling procedures used by different laboratories. The ALMERA network is a world-wide network of analytical laboratories located in IAEA member states capable of providing reliable and timely analysis of environmental samples in the event of an accidental or intentional release of radioactivity. Ten ALMERA laboratories were selected to participate in the sampling exercise. The soil sampling intercomparison exercise took place in November 2005 in an agricultural area qualified as a “reference site”, aimed at assessing the uncertainties associated with soil sampling in agricultural, semi-natural, urban and contaminated environments and suitable for performing sampling intercomparison. In this paper, the laboratories sampling performance were evaluated.     

A stochastic Lagrangian micromixing model for the dispersion of reactive scalars in turbulent flows: role of concentration fluctuations and improvements to the conserved scalar theory under non-homogeneous conditions

Several reaction schemes, based on the conserved scalar theory, are implemented within a stochastic Lagrangian micromixing model to simulate the dispersion of reactive scalars in turbulent flows. In particular, the formulation of the reaction-dominated limit (RDL) reaction scheme is here extended to improve the model performance under non-homogeneous conditions (NHRDL scheme). The validation of the stochastic model is obtained by comparison with the available measurements of reactive pollutant concentrations in a grid-generated turbulent flow. This test case describes the dispersion of two atmospheric reactant species (NO and O₃) and their reaction product (NO₂) in an unbounded turbulent flow. Model inter-comparisons are also assessed, by considering the results of state-of-the-art models for pollutant dispersion. The present validation shows that RDL reaction scheme provides a systematic overestimation (relative error of ca. 85% around the centreline) in computing the local reactant consumption/production rate, whereas the NHRDL scheme drastically reduces this gap (relative error lower than 5% around the centreline). In terms of NO₂ production (or reactant consumption), neglecting concentration fluctuations determines overestimations of the product mean of around 100% and a NO₂ local production of one order of magnitude higher than the reference simulation. In terms of standard deviations, the concentration fluctuations of both the passive and reactive scalars are generally of the same order of magnitude or up to 1 or 2 orders of magnitudes higher than the corresponding ensemble mean values, except for the background reactant close to the plume edges. The study highlights the importance of modelling pollutant reactions depending on the instantaneous instead of the mean concentrations of the reactants, thus quantifying the role of the turbulent fluctuations of concentration, in terms of scalar statistics (mean, standard deviation, intensity of fluctuations, skewness and kurtosis of concentration, segregation coefficient, simulated reaction rate). This stochastic particle method represents an efficient numerical technique to solve the convection–diffusion equation for reactive scalars and involves several application fields: micro-scale air quality (urban and street-canyon scales), accidental releases, impact of odours, water quality and fluid flow industrial processes (e.g. combustion).