The Contribution by the Study of the Algae Forms (Phytoplankton and Periphyton) as Integrators of Physicochemical and Microbiological Data in the Varenna Stream

Physico-chemical, microbiological, ichthyotoxicological conditions and microalgae of Varenna stream were studied in samples taken in 12 collecting stations. The data reported indicate a marked deterioration proceeding downstream e.g. an increase of bacterial population, concentration of suspended solids, COD and variations in the composition and abundance of phytoplankton and periphyton.     

Comparisons of genotype-tolerance responses in populations of <Emphasis Type="Italic">Hediste diversicolor</Emphasis> (Polychaeta: Nereididae) exposed to copper stress

The analysis of genotypic shifts in field-exposed populations has been proposed as a tool for monitoring the environmental impacts of contaminants. Previous laboratory experiments showed the occurrence of genotypic shifts induced by copper exposure in samples of Hediste diversicolor from the Pialassa estuary (North Adriatic Sea, Italy). In order to test if genotype-tolerance responses observed were consistent at larger spatial scales, populations of H. diversicolor were sampled in three haphazardly chosen estuaries along the Italian coast (Comacchio, Pialassa, Serchio) and exposed to 0.48 mg l⁻¹ Cu²⁺ under laboratory conditions. Survival analysis procedures were used to test for possible relationships between time-to-death and genotypes at three allozyme loci (ALD, FH, PGI). Genotype-tolerance responses observed at locus ALD were consistent among populations up to 2500 km distant, with genotype ALD ^102/102 associated with the shortest survival times. Comparisons with previous laboratory experiments showed that responses to copper stress at locus ALD were also consistent in time, with genotypes ALD ^102/102 and ALD ^100/102 associated with higher 96 h mortality ratios. Results suggested the occurrence of stable relationships between genotypes at locus ALD and tolerance responses of H. diversicolor to copper stress. Conversely, genotype-tolerance responses at loci PGI and FH were not consistent either in space (among populations from the three estuaries) or in time (between laboratory experiments), being possibly affected by site-specific features of populations or stochastic factors. Results show that genotype-tolerance responses should be carefully verified at different spatial and temporal scales, before considering genotypic shifts among the possible tools for monitoring the effects of environmental stressors.     

Atmospheric bulk deposition to the lagoon of Venice Part I. Fluxes of metals, nutrients and organic contaminants

First available data on atmospheric fall-out were provided by sampling monthly bulk depositions in four sites inside the Lagoon of Venice (550 km2). Sampling was carried out monthly during the period July 1998-July 1999, in one site near an industrial area (Porto Marghera; site D), another site in the city of Venice (site A), and the remaining two in the southern- and northernmost ends of the Lagoon (Valle Figheri, site C; Valle Dogà site B). The following determinations were carried out for each samples: pH, conductivity, grain-size, particulate load, and dissolved nutrients (N, P). Samples were then subdivided into soluble and insoluble fractions, and Al, Ca, Na, K, Mg, Si, Mn, Fe, Zn, Ni, Cr, Cu, Pb, Cd, As, Hg, Ti, V, S, P, Se and Sb were analysed on both fractions. Total organic micropollutants (PAH, PCB, HCB, DDT, PCDD/F) were measured. As regards particle size distribution, there was great variability among sampling sites. The percentage of the < or =2 microm grain-size fraction was higher in the southern and northern ends of the Lagoon. Small differences were found among sites for major elements, whereas higher variability was observed for inorganic and organic micropollutants, with standard deviations between 20% and 60% of the fluxes measured. Major differences in annual fluxes between the most polluted sites (mostly D and A) and background (site B) were seen for Cd (0.26 vs. 0.06 mg m(-2) year(-1)), Hg (41 vs. 15 microg m(-2) year(-1)), PCB ( approximately 2500 vs. approximately 500 ng m(-2) year(-1)) and HCB ( approximately 8000 vs. approximately 1000 ng m(-2) year(-1)). Comparisons with previous data, collected in the periods 1993-1994 and 1995-1997, were only available for a few trace metals. A definite decline in the annual Pb flux in the city of Venice was detected, from 18 to 13 mg m(-2) in 1996/1997 and 1995/1996 respectively, to approximately 5 mg m(-2) in the present study. Total annual deposition was calculated by means of two different methods, which gave very similar results: (i) the mean value of deposition in the four sites was multiplied by lagoon area (550 km2); (ii) the monthly rain isopleths were combined to normalize deposition values. The figures are: 15-34 kg of Hg and Sb, approximately 200 kg of As, approximately 100 kg of Cd and PAH, 0.7-1.3 tons of Cr, Ni and V, more than 2 tons of Cu and Pb, 17 of Zn, 55 of total P, approximately 200 of Al, and 3900 of DIN. Total fluxes of organics inside the lagoon were: PAH approximately 100 kg; HCB approximately 1 kg; DDT approximately 0.4 kg. PCB and PCDD/F fluxes were approximately 500 g and approximately 10 g, corresponding respectively to 0.1 and 0.4 g I-TE. The correlations between fluxes of inorganic micropollutants and grain-size were significant. Multivariate statistical analysis was applied to investigate more accurately relationships between the insoluble and dissolved fractions of inorganic micropollutants and grain-size fractions. In particular, significant correlations were highlighted between the dissolved fraction of As and the < or =1 mum particle size fraction. Relations between levels of SigmaPCDDF, SigmaPCDD, PCB and PAH congeners and grain-size revealed significant correlation coefficients for the remote sites (B, C), and none in the urban and industrial sites (A, D). In particular, significant correlations were highlighted between SigmaPCDDF, SigmaPCDD and particle size fraction < or =2 mum, and between benzo(a)pyrene and PCB 167 and particle size fraction 4-8 mum.     

Adsorption of eosin dye on activated carbon and its surfactant based desorption

The performance of activated carbon has been investigated for the adsorption of eosin dye dissolved in water. Eosin is anionic in nature and highly toxic. The effects of initial dye concentration, contact time, pH and temperature on adsorption of eosin by a fixed amount of activated carbon (1.0 g/L) have been studied in batch and column mode. The equilibrium data are successfully fitted to the Freundlich adsorption isotherm. The adsorption rate data are successfully explained by a pseudo second-order kinetic model. Breakthrough curves for column adsorption have also been studied. The regeneration of spent carbon by desorbing the dye has been experimentally investigated applying a surfactant enhanced carbon regeneration (SECR) technique using both cationic and anionic surfactants. An empirical kinetic model for dye desorption from the commercial activated carbon (CAC) using different surfactant and desorption techniques, viz. change in pH, has been proposed. The comparison between the model and the experimental results is found to be satisfactory.     

Clonal variation in heavy metal accumulation and biomass production in a poplar coppice culture. II. Vertical distribution and phytoextraction potential

Short rotation coppice cultures (SRC) are intensively managed, high-density plantations of multi-shoot trees. In April 1996, an SRC field trial with 17 different poplar clones was established in Boom (Belgium) on a former waste disposal site. In December 1996 and January 2001, all shoots were cut back to a height of 5 cm to create a coppice culture. For six clones, wood and bark were sampled at the bottom, middle and top of a shoot in August and November 2002. No significant height effect of metal concentration was found, but for wood, metal concentrations generally increased toward the top of the shoot in August, and decreased toward the top of the shoot in November. Phytoextraction potential of a clone was primarily determined by metal concentration and by biomass production. Shoot size and number of shoots per stool were less important, as a high biomass production could be achieved by producing a few large shoots or many smaller shoots. Clone Fritzi Pauley accumulated 1.4 kg ha(-1) of Al over two years; Wolterson and Balsam Spire showed a relatively high accumulation of Cd and Zn, i.e. averaging, respectively 47 and 57 g ha(-1) for Cd and 2.4 and 2.0 kg ha(-1) for Zn over two years.     

Canopy profiles of photosynthetic parameters under elevated CO2 and N fertilization in a poplar plantation

A poplar plantation has been exposed to an elevated CO2 concentration for 5 years using the free air CO2 enrichment (FACE) technique. Even after such a long period of exposure, leaves of Populus x euramericana have not shown clear signs of photosynthetic acclimation. Only at the end of the growing season for shade leaves was a decrease of maximum velocity of carboxylation (Vcmax) observed. Maximum electron transport rate (Jmax) was increased by FACE treatment in July. Assimilation rates at CO2 partial pressure of 400 (A400) and 600 (A600) micromol mol(-1) were not significantly different under FACE treatment. Most notably FACE significantly decreased stomatal conductance (g(s)) both on upper and lower canopy leaves. N fertilization increased N content in the leaves on mass basis (Nm) and specific leaf area (SLA) in both CO2 treatments but did not influence the photosynthetic parameters. These data show that in poplar plantations the long-term effects of elevated CO2 on photosynthesis do not differ considerably from the short-term ones even with N deposition.