Testing the use of juvenile Salmo trutta L. as biomonitors of heavy metal pollution in freshwater

Individual specimens of Salmo trutta were captured, from four sampling sites in Galician rivers (NW Spain) affected by different types of contamination: diffuse urban waste, run-off from an unrestored dump at a copper mine and waste from a fish farm. The ages of the captured trouts were established and only those belonging to the 1+ age class were selected for study. The liver and kidney were removed from each fish and analysed to determine the tissue concentrations of Cu, Fe and Zn. The results obtained showed that: (i) the use of 1+ individuals allowed differentiation of contamination scenarios on the basis of the tissue concentrations of metal; (ii) the use of 1+ individuals allowed standardization of the time of exposure, which was sufficiently long for differential uptake to have taken place; (iii) liver tissue provided the best results as, less effort was required than for processing kidney tissue, and significant differences between sampling sites were detected because the intrapopulational variability in metal levels was lower than for kidney, and (iv) the levels of elements detected were not affected by basal tissue concentrations or residual concentrations due to past contamination, which older trouts may have been exposed to. In addition, the use of 1+ trout may provide better results in annual environmental sampling surveys.     

Do differences between metal body residues reflect the differences between effects for Chironomus riparius exposed to different sediments?

Sediment characteristics are well known to interfere with toxicity, mainly through differences in terms of bioaccumulation. Here, with chironomids exposed to zinc in an artificial and a field sediment, we investigated the differences of zinc accumulation and of effects on the life cycle, at individual and population level. We used biology and energy-based modeling to analyze the data at all the levels of biological organization. This permits a reliable estimation of thresholds values for tissue residues. Differences in zinc tissue residues accounted for most of the differences between the results for both sediments (a factor of 11 for differences from 20 to 100 depending on the parameter which is considered). Taking into account accumulation and background variability, the differences relative to thresholds could be accounted for. However, it appeared that, once the threshold was passed, effects were much more pronounced for organisms exposed to artificial sediment compared to field sediment. We concluded that some sediment characteristics can enhance toxicity, in addition to their influence on the compound accumulation, even if the latter was the major source of differences in our study.     

Self-organizing feature map (neural networks) as a tool in classification of the relations between chemical composition of aquatic bryophytes and types of streambeds in the Tatra national park in Poland

Concentrations of the elements Al, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb and Zn were measured in the aquatic bryophytes Fontinalis antipyretica, Platyhypnidium riparioides and Scapania undulata. These bryophytes were sampled from streams flowing through granites/gneisses, limestones/dolomites and sandstones in the Tatra national park in Poland. The Self-organizing feature map (SOFM) or Kohonen network was used to classify the bryophytes according to the concentrations of the elements. This method was verified using principal component analysis (PCA) to check whether this well-known technique would give similar results. Both the self-organizing map and ordination by PCA yielded distinct groups of aquatic bryophytes growing in streams flowing through different types of rock, groups which differed significantly in the concentrations of certain elements. Bryophytes from granites/gneisses were distinguished by higher concentrations of Cd and Pb, while those from sandstones had a higher concentration of Cr and those from limestones/dolomites had higher concentrations of Ca and Mg. The SOFM and PCA ordinations thus yield identical classifications of bryophytes from the Tatra mountains streams.     

Bioavailability and plant accumulation of heavy metals and phosphorus in agricultural soils amended by long-term application of sewage sludge

Amendment of agricultural soils with municipal sewage sludges provides a valuable source of plant nutrients and organic matter. Nevertheless, addition of heavy metals and risks of eutrophication continue to be of concern. Metal behaviour in soils and plant uptake are dependent on the nature of the metal, sludge/soil physico-chemical properties and plant species. A pot experiment was carried out to evaluate plant production and heavy metal uptake, soil heavy metal pools and bioavailability, and soil P pools and possible leaching losses, in agricultural soils amended with sewage sludge for at least 10 years (F20) compared to non-amended soils (control). Sewage sludge application increased soil pH, N, Olsen-extractable-P, DOC and exchangeable Ca, Mg and K concentrations. Total and EDTA-extractable soil concentrations of Cu and Zn were also significantly greater in F20, and soil metal (Cu, Mn and Zn) and P fractionation altered. Compared to the control, in F20 relative amounts of acid-extractable (Mn, Zn), reducible (Mn, Zn) and oxidisable (Cu, Zn) metal fractions were greater, and a dominance of inorganic P forms was observed. Analyses of F20 soil solutions highlighted risks of PO4 and Cu leaching. However, despite the observed increases in metal bioavailability sewage sludge applications did not lead to an increase in plant shoot concentrations (in wild plants or crop species). On the contrary, depending on the plant species, Mn and Zn tissue concentrations were within the deficiency level for most plants.     

LC-MS-MS analysis and occurrence of octyl- and nonylphenol, their ethoxylates and their carboxylates in Belgian and Italian textile industry, waste water treatment plant effluents and surface waters

Alkylphenols (APs), alkylphenol ethoxylates (APEOs), ethoxycarboxylate metabolites (APECs) and bisphenol A were determined in surface water using solid-phase extraction (SPE) followed by triple-quadrupole LC-MS-MS. APs were separated by LC from APECs using an acetonitrile-water-gradient without the addition of any buffer. Nonylphenol ethoxycarboxylates (NPECs) interfere in the detection of nonylphenols (NPs) when using an acidic mobile phase, because they produce the same MS-MS fragment ions (219>133 and 147). 4n-NP shows the characteristic transition 219>106; it is well suited as internal standard. Nonylphenol ethoxylates NPE(n)Os (n=1-17) were analysed separately in a second run by positive ionization using an ammonium acetate mobile phase. Textile industry discharges, the corresponding wastewater treatment plant (WWTP) effluents and the receiving rivers in Belgium and Italy were analysed. Among the substances investigated, NPE1C and NPE2O exhibited the highest concentrations in the water samples, up to 4.5 microg l(-1) NPE1C in a WWTP effluent and 3.6 microg l(-1) NPE2O in a river. The highest NP levels were found in the receiving rivers (max. 2.5 microg l(-1)). The predicted no-effect concentration (PNEC) for NP of 0.33 microg l(-1) for water species was frequently exceeded in the surface waters investigated, suggesting potential adverse effects to the aquatic environment.     

Pteris umbrosa R. Br. as an arsenic hyperaccumulator: accumulation, partitioning and comparison with the established As hyperaccumulator Pteris vittata

The capacity of the Australian native fern Pteris umbrosa to function as an arsenic (As) hyperaccumulator (shoot:soil As concentration >1) was examined by growing plants under glasshouse conditions in an inert medium supplemented with As. Arsenic preferentially accumulated in the fronds, a trait of a hyperaccumulator. The As concentration of fronds decreased with age, being particularly high in the croziers and low in the senesced fronds. Below ground, rhizomes accumulated more As than adventitious roots. Uptake from a range of solution concentrations followed Michaelis Menten kinetics up to a soil solution As concentration of 400mgl(-1). The K(m) for As uptake by roots suggested the operation of a low-affinity carrier. The predicted Nernst membrane potential indicated that uptake was against the electrochemical gradient of As. At 600mgl(-1), the rate of As uptake increased and phytotoxic effects were indicated by a significant decline in biomass. Arsenic uptake and translocation in P. umbrosa and Pteris vittata were similar at low exposure to As. At higher exposure, As uptake and translocation by P. vittata increased more than in P. umbrosa. The growth rate of both ferns was similar, whereas the biomass distribution was not, with P. vittata having a much larger root mass. This suggests that As uptake by P. umbrosa roots was very efficient and may be improved by stimulating root growth to enhance its potential.     

Antimony distribution and mobility in topsoils and plants (Cytisus striatus, Cistus ladanifer and Dittrichia viscosa) from polluted Sb-mining areas in Extremadura (Spain)

A study about topsoil antimony distribution and mobility from the soils to the biomass has been afforded in three abandoned Sb mining areas located at Extremadura. Physico-chemical characteristics of the soils and total antimony levels were measured in soils and autochthonous plant species (Cytisus striatus, Cistus ladanifer and Dittrichia viscosa). Comparison with corresponding values in reference areas isolated from the mining activities is discussed. Antimony mobility in the soils was estimated by measuring the water extractable fraction; low results were obtained for the three soil areas, with no statistical differences. Plant ability to accumulate antimony was estimated by use of plant accumulation coefficients (PAC). Seasonal (spring vs. autumn) effects on the antimony content in the plant species. Cytisus striatus from Mari Rosa mine presented antimony excluder characteristics, whereas Dittrichia viscosa specimens growing in San Antonio mine showed a significant antimony bioaccumulation.     

Algal-bacterial interactions in metal contaminated floodplain sediments

The aim of the present study was to investigate algal-bacterial interactions in a gradient of metal contaminated natural sediments. By means of multivariate techniques, we related the genetic structure (denaturing gradient gel electrophoresis, DGGE) and the physiological structure (community-level physiological profiling, CLPP) of the bacterial communities to the species composition of the algal communities and to the abiotic environmental variables, including metal contamination. The results revealed that genetic and physiological structure of the bacterial communities correlated with the species composition of the algal community, but hardly to the level of metal pollution. This must be interpreted as an indication for a strong and species-specific linkage of algal and bacterial species in floodplain sediments. Metals were, however, not proven to affect either the algal or the bacterial communities of the Dutch river floodplains.     

Stomatal conductance of semi-natural Mediterranean grasslands: implications for the development of ozone critical levels

Intra-genus and intra-specific variation and the influence of nitrogen enrichment on net assimilation and stomatal conductance of some annual Trifolium species of Mediterranean dehesa grasslands were assessed under experimental conditions. Also gas exchange rates were compared between some Leguminosae and Poaceae species growing in the field in a dehesa ecosystem in central Spain. The results showed that the previously reported different O3 sensitivity of some Trifolium species growing in pots does not seem to be related to different maximum g(s) values. In addition, no clear differences on gas exchange rates could be attributed to Leguminosae and Poaceae families growing in the field, with intra-genus variation being more important than differences found between families. Further studies are needed to increase the database for developing a flux-based approach for setting O3 critical levels for semi-natural Mediterranean species.