Metal speciation in sediments of polluted and non‐polluted lakes

A five‐step extraction procedure for metal speciation studies (copper, lead, nickel, manganese and zinc) was applied to the analysis of lake sediments characterised by different environmental features. A different partition of metals into the several metal forms was observed. Both the metal fraction sorbed or co‐precipitated on hydrous Mn‐oxides (especially lead and zinc) and that bound to organic matter (especially copper) are high in some samples. A prevalently anthropogenic origin of these metals may be hypothesised on the basis of existing knowledge of the equilibrium and change phenomena occurring among water, particulate and sediments. Conversely, the non‐solubilised forms of metals are abundant in the sediments of lakes that are certainly not polluted. The concentration of manganese is very high in the sediments of Antarctic lakes; sequential extractions show its lithogenic origin. In conclusion, a knowledge of the different types of metal associations in sediments and their percentage can facilitate understanding of both natural and anthropogenic metal enrichment of aquatic systems.     

Metal distribution in marine sediments of the Mar Piccolo in Taranto (Ionic Sea,southern Italy)

The spatial distribution of selected metals (Fe, Ni, Mn, Zn, Cu, Pb, Hg and Cd) and their partition in the different chemical forms (speciation) were determined in benthic sediments from Mar Piccolo, Taranto (Ionic Sea, southern Italy). The aim of this study was to assess the degree of sediment contamination and bioavailability of metals, very important for Italian mussel culture, in a semi-enclosed marine ecosystem. In sediments, grain size distribution, total organic carbon (TOC), and humic (HA) and fulvic (FA) acids contents were also determined. The compounds TOC, HA and FA, in fact, have a great influence on metal complexation. High concentrations of copper, lead, zinc and mercury were found, especially in sediments of the first inlet of Mar Piccolo. Statistical analysis of results shows significant correlation among Cu, Pb and Zn concentrations and the influence of organic matter on the sediment distribution of Cu, Pb and Zn. Metal speciation analysis, carried out with sequential extraction method, shows that Fe and Ni are present in sediments mainly as sulphides. Mn and Pb are present principally in an ion-exchangeable form or bound to carbonate and Cu is associated to organic matter. Metal pollution index (MPI), calculated as a weighed mean of the metal contamination factors in each station, shows that with regard to Cu, Ni, Pb and Zn, some stations investigated are unpolluted (MPI <1), whereas in other areas, pollution level is not very high. On the contrary, for mercury, the pollution level in the first inlet of the basin is very high.     

Bioaccessibility of metals in soils: comparison between chemical extractions and in vitro tests

It is well-known that the total metal content in soils is not a good indicator of their harmful effects, leading to an overestimation of risks. Toxicological and environmental hazards depend on the chemical species and on its bioavailability to target organisms. Because a good estimation of bioavailability is difficult, a good compromise is to assess bioaccessibility, defined as the maximum amount of a pollutant which is potentially absorbable by a target organism. This study presents a comparison of different strategies to measure metal bioaccessibility in soils. Three procedures were applied to real soil samples with different levels of metal contamination: pseudo-total metal attack, selective sequential extractions and in vitro tests (deliberately developed to simulate human or mammals digestion). Considering the first step of the selective extraction procedure, which can provide the bioaccessible fraction for deposit-feeder organisms, data obtained for each metal were lower than those obtained from in vitro tests. Therefore, it is possible to highlight that this extraction tends to underestimate metal bioaccessibility in soils for humans, while in vitro tests certainly will overestimate bioaccessibility for organisms as invertebrates. If the sum of first and second step of sequential procedure is considered, results are quite similar to those obtained from in vitro tests, but this kind of procedure would require two days of work rather than a few hours required to perform an in vitro test. Results highlight the diversity among the differently defined bioaccessible fractions and the need to apply the most suitable procedure depending on the target organism.     

A roadmap for the conservation of freshwater mussels in Europe

Europe has a long history of human pressure on freshwater ecosystems. As pressure continues to grow and new threats emerge, there is an urgent need for conservation of freshwater biodiversity and its ecosystem services. However, whilst some taxonomic groups, mainly vertebrates, have received a disproportionate amount of attention and funds, other groups remain largely off the public and scientific radar. Freshwater mussels (Bivalvia, Unionida) are an alarming example of this conservation bias and here we point out six conceptual areas that need immediate and long-term attention: knowledge, threats, socioeconomics, conservation, governance and education. The proposed roadmap aims to advance research, policy and education by identifying the most pressing priorities for the short- and long-term conservation of freshwater mussels across Europe.     

Organochlorine pesticide air-water exchange and bioconcentration in krill in the Ross Sea

Mean hexachlorobenzene (HCB) and hexachlorocyclohexane (HCH) concentrations, measured in seawater and air samples, confirmed the decline in levels of these compounds in Antarctic air and water. However, low α/γ-HCH ratios in air at the beginning of the sampling period suggest a predominance of fresh lindane entering the Antarctic atmosphere during the Austral spring probably due to current use in the Southern Hemisphere. Water-air fugacity ratios demonstrate the potential for HCH gas deposition to coastal Antarctic seas, while the water-air fugacity ratios for HCB imply that volatilization does not account for the observed decrease of HCB in surface seawater. HCH concentrations found in krill samples were correlated with seawater concentrations indicative of bioconcentration of HCHs from seawater.     

Municipal landfill leachate-soil interactions: a kinetic approach

On investigating the effects of municipal landfill leachates on soils, it is found that the adsorption of landfill leachate constituents creates a "new" soil surface able to enhance heavy metal uptake. In particular, the treatment of soil with the total leachates led to an increase in its metal retention capability that was much higher than for each individual fraction. Results show that the leachate sorption on soil is regulated by the presence of leachate constituents with low molecular weight cut-off since these fractions are able to "accelerate" the sorption of higher molecular weight fractions. The rapidly sorbed lower molecular weight fractions create a different soil surface that is able to accommodate the high molecular weight constituents.     

Meiofauna densities and gastrotrich community composition in a Mediterranean sea cave

During the past 5 decades, the large-sized biota inhabiting dark marine caves has attracted the attention of many marine biologists; in contrast, studies concerning the meiofaunal organisms of these peculiar biotopes remain scanty and mostly with a taxonomic aim. In this study, the nature and abundance of meiofaunal taxa living in a Mediterranean, semi-submerged sea cave was surveyed in relation to distance from the entrance and over two different seasonal periods. Particular attention was paid to the Gastrotricha taxocene. Research was carried out in a cave along the Ionian coast of Apulia (southern Italy), the “Grotta Piccola del Ciolo” which opens for approximately 120 m on the north-eastern side of a shallow fjord and has a bottom blanketed by fine to very fine sand, occasionally rich in detritus. Quantitative samples in four replicates were collected by SCUBA diving, in November 2000 and June 2001, coring the sediment with a hand-held piston corer in three light-free sites (stations 1–3) located at increasing distances from the entrance. At each site, two additional 500-ml sediment samples were collected for an in vivo study of the Gastrotricha. Faunistic analysis found a fairly high meiobenthic diversity, identifying representatives of more than 12 major groups, with total abundances ranging from 656 ind./10 cm² (10 cm²) in November to 1,069 ind./10 cm² in June. Station 1, the closest to the entrance invariably hosted the most abundant meiofaunal community (851 ind./10 cm² in November and 1932 ind./10 cm² in June), followed by station 2 or 3 depending on the season. While nematodes and harpacticoids appear as the most abundant taxa when the cave is considered as a whole, other taxa may prevail numerically in selected stations, e.g. priapulids, which are the second most abundant taxon at station 1 (30 ind./10 cm² in November and 83 ind./10 cm² in June). Although the density of total meiofauna and that of the single groups may not be very high, the cave is interesting by virtue of the peculiarity of the hosted fauna, e.g., species and genera new to science or new to the Mediterranean Sea. Regarding the Gastrotricha, we found 16 species, accounting for 1.3–2.6% of the total meiobenthos (density = 8.4 ind./10 cm² in November and 27.4 ind./10 cm² in June). Analysis of the gastrotrich community found, particularly in June, an assemblage of taxa quite different from those found in open habitats, even at the family level; differences that are probably due to the exploitation of different food resources by animals populating the two environments, i.e. algae in the open sea versus bacteria in the caves. Results indicate that for meiofauna, as happens for macrofauna, the marine caves may represent hotspots of biodiversity and endemism; the driving forces at the base of the trophic depletion hypothesis seem to be responsible for structuring the meiofauna community inside the cave.     

Spatial and seasonal variability of dissolved oxygen and nutrients in the Southern Adriatic coastal waters

The main objective of this paper is to present vertical and horizontal patterns of dissolved oxygen and nutrients found during four seasonal surveys (March, June, September and December 2000) in the Southern Adriatic Sea coastal waters. The multivariate technique Principal Component Analysis has been applied to our dataset considering the following parameters: seawater temperature, salinity, dissolved oxygen and nutrients (nitrate, nitrite, phosphate, silicate). The resulting plot shows in a self-explanatory way that a seasonal trend was not observable in the investigated period and that no significant differences occur between the stations sampled in the Taranto Gulf and those along the Adriatic coast. Water column stratification persists in all seasons, except in spring, in the shallowest stations. The surface layer is characterized by a low nutrient content. The influence of the Northern Adriatic Surface Water in the Southern Adriatic sub-basin seems to be very low and can be traced by nitrate and silicate only in spring and winter. Regarding deep waters, nitrate distribution shows an increasing gradient moving from the coast to the open sea, having the lowest concentration in the shelf area and the highest in the most offshore stations of the Otranto Strait. In the Otranto Strait area the vertical distributions of physical and chemical parameters show, at middle depths, the inflow of Levantine Intermediate Water, traced by both the maximum of salinity, nitrate and phosphate and the minimum of oxygen. The LIW signal is lost moving northward. The outflow of Adriatic Dense Water is less evident, being traced only in spring by an oxygen increase at the bottom layer in the shelf area. The N:P ratio is highly variable but in the range already observed in the Southern Adriatic, suggesting a P-limitation, which can both contribute to the low primary productivity of the area and support the N:P ratio anomaly of the Eastern Mediterranean.     

Spatial and seasonal variability of dissolved oxygen and nutrients in the Southern Adriatic coastal waters

The main objective of this paper is to present vertical and horizontal patterns of dissolved oxygen and nutrients found during four seasonal surveys (March, June, September and December 2000) in the Southern Adriatic Sea coastal waters. The multivariate technique Principal Component Analysis has been applied to our dataset considering the following parameters: seawater temperature, salinity, dissolved oxygen and nutrients (nitrate, nitrite, phosphate, silicate). The resulting plot shows in a self-explanatory way that a seasonal trend was not observable in the investigated period and that no significant differences occur between the stations sampled in the Taranto Gulf and those along the Adriatic coast. Water column stratification persists in all seasons, except in spring, in the shallowest stations. The surface layer is characterized by a low nutrient content. The influence of the Northern Adriatic Surface Water in the Southern Adriatic sub-basin seems to be very low and can be traced by nitrate and silicate only in spring and winter. Regarding deep waters, nitrate distribution shows an increasing gradient moving from the coast to the open sea, having the lowest concentration in the shelf area and the highest in the most offshore stations of the Otranto Strait. In the Otranto Strait area the vertical distributions of physical and chemical parameters show, at middle depths, the inflow of Levantine Intermediate Water, traced by both the maximum of salinity, nitrate and phosphate and the minimum of oxygen. The LIW signal is lost moving northward. The outflow of Adriatic Dense Water is less evident, being traced only in spring by an oxygen increase at the bottom layer in the shelf area. The N:P ratio is highly variable but in the range already observed in the Southern Adriatic, suggesting a P-limitation, which can both contribute to the low primary productivity of the area and support the N:P ratio anomaly of the Eastern Mediterranean.