Mercury in the Mediterranean. Part 2: processes and mass balance

Mass balance of contaminants can provide useful information on the processes that influence their concentrations in various environmental compartments. The most important sources, sinks and the equilibrium or non-equilibrium state of the contaminant in individual environmental compartments can also be identified. Using the latest mercury speciation data, the results of numerical models and the results of recent studies on mercury transport and transformation processes in the marine environment, we have re-evaluated the total mercury (HgT) mass balance in the Mediterranean Sea. New calculations have been performed employing three distinct marine layers: the surface layer, the thermocline and the deep sea. New transport mechanisms, deep water formation and density-driven sinking and upwelling, were included in the mass balance calculations. The most recent data have even enabled the calculation of an approximate methylmercury (MeHg) mass balance. HgT is well balanced in the entire Mediterranean, and the discrepancies between inputs and outputs in individual layers do not exceed 20 %. The MeHg balance shows larger discrepancies between gains and losses due to measurement uncertainties and gaps in our knowledge of Hg species transformation processes. Nonetheless, the main sources and sinks of HgT (deposition and evasion) and MeHg (fluxes from sediment, outflow through the Gibraltar Strait) are in accordance with previous studies on mercury in the Mediterranean Basin. Mercury in the Mediterranean fish harvest is the second largest MeHg sink; about 300 kg of this toxic substance is consumed annually with sea food.     

Transformation of a non-oestrogenic steroid metabolite to an oestrogenically active substance by minimal bacterial activity

The majority of oestrogenic material excreted from humans and wildlife, and therefore released into sewers, is in a conjugated form. However, the finding of “free” oestrogens in sewage effluent suggests that these metabolites are somehow converted back into an active form, before or during passage through a sewage treatment process. When male fathead minnows (Pimephales promelas) were continuously exposed to oestradiol-3-glucuronide, in a continuous-flow system, it demonstrated no inherent oestrogenic activity. However, when fish were exposed to effluent generated from laboratory simulations of sewage treatment processes, to which had been added oestradiol-3-glucuronide, oestrogenic activity was observed, suggesting microbial activity was capable of degrading the steroid metabolite into a more potent oestrogen. Oestrogenic potency was determined by measuring changes in plasma vitellogenin (egg yolk precursor) concentrations and gonadosomatic index. The results suggest that inactive metabolites of steroids are very readily biotransformed into biologically active oestrogens.     

Cancer incidence in people with residential exposure to a municipal waste incinerator: An ecological study in Modena (Italy), 1991–2005

We conducted a retrospective ecological study to assess cancer incidence during the period 1991–2005 in proximity of a municipal waste incinerator (MWI) in Modena (Italy). We identified three bands of increasing distance from the MWI, up to a radius of 5 km and used the residence as surrogate marker of the exposure. Residential history for Modena’s population was reconstructed and residents were associated to the most appropriate census unit. Age-standardized incidence ratios (ASR) and standardized incidence ratios (SIR) were estimated for all cancers and selected sites. Variations in cancer incidence were investigated using space and space–time scan statistic. Deprivation index was taken into account as potential confounding factor. During the 15-year study period, 16,443 new cases of cancer were diagnosed among residents in Modena. The space–time clustering test identified three significant clusters but their shapes were not associable to the MWI exposition. The purely spatial analysis not showed statistically significant clusters. The SIR computed for all cancers and selected sites did not show any excess of risk in the area closest to the plant. Higher SIR for leukaemia was found in the second band from MWI (2–3.5 km) for females (SIR, age and DI adjusted: 1.35, 95%CI: 1.01–1.79) and for both sexes (SIR, age and DI adjusted: 1.28, 95%CI: 1.03–1.57), but not a spatial trend was observed, thus excluding a possible link with MWI. In conclusion, bearing in mind the intrinsic limits of the study, the results suggest that there is no detectable increase of cancer risk for people living in proximity to the Modena MWI.     

Fate of the veterinary antibiotic 14C-difloxacin in soil including simultaneous amendment of pig manure with the focus on non-extractable residues

The fate of ¹⁴C-labeled difloxacin (¹⁴C-DIF) was studied in time course experiments after application on soil (Ap horizon of silt loam) and amendment of authentic DIF containing pig manure (146 mL kg^?1; 4.17 MBq kg^?1; 0.85 mg kg^?1) or water (124 mL kg^?1; 0.42 MBq kg^?1; 0.09 mg kg^?1) for 56 and 120 days of incubation, respectively.

Mineralization of ¹⁴C-DIF was below 0.2% in both experiments after 56 days or 120 days. In the course of the experiments, portions of extractable radioactivity (Accelerated Solvent Extraction (ASE); acetonitrile-water) decreased to 19–21% depending only little on manure amendment. Non-extractable residues of ¹⁴C-DIF increased to 70–74% after 56 days and 120 days, respectively, and therefore were the main route of ¹⁴C-DIF in soil. According to radioanalytical HPLC and LC-MS/MS, only the parent compound was found in all extracts over the whole time of the experiment. According to fractionation of the non-extractable residues (NER) into particle size fractions, ¹⁴C portions were associated to the water used for fractionation, the silt and clay fractions, whereas no radioactivity was detected in the sand fraction. The majority of ¹⁴C was found within the clay fractions.

Fractionation of humic components showed that radioactivity derived from ¹⁴C-DIF was associated with humic acids, fulvic acids, humins and minerals and very little with soluble, non-humic HCl fraction. The highest portions of radioactivity were found in the fulvic acid fraction. Results obtained by size exclusion chromatography (SEC) of the purified fulvic acids were similar for every sample analyzed. One large portion of ¹⁴C co-eluted with fulvic acids of a molecular weight below 910 g mol^?1. Both fractionation methods demonstrated that the parent compound DIF or initial metabolites were rapidly integrated into humic materials and, thus, were major components of NER.     

Comparison of different methods for extraction of polycyclic aromatic hydrocarbons (PAHs) from Sicilian (Italy) coastal area sediments

This paper describes a work aimed at improving the conditions of an extraction method, coupling GC-MS determination, for the analysis without cleanup phase, of polycyclic aromatic hydrocarbons (PAHs) from sediment samples. The automatic Soxhlet extraction in warm mode (using Extraction System B-811 Standard, Büchi) has demonstrated advantages for automation, reduced extraction time, and lower solvent use than for conventional Soxhlet extraction. Under these conditions, the recoveries are very good as they resulted greater than 85 % and, in most of the cases, near 100 %. The repeatability is also satisfactory (relative standard deviation less than 15 %). The detection limits are also acceptable and ranged from 0.001 to0.01 μg/kg dry weight. Fifty-four sediment samples were collected. The total concentration of the 17 compounds investigated, in samples of sediments collected from three Sicilian coastal areas, expressed as the sum of concentrations, varies from 99 to 11,557 μg/kg of dry matrix; concentrations of total PAHs in the sediments of Cala are two to three times higher than the other stations.