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Tesi etd-11082012-001741


Thesis type
Tesi di dottorato di ricerca
Author
VANNI, GIACOMO
URN
etd-11082012-001741
Title
Quality monitoring of urban green areas of Pisa
Settore scientifico disciplinare
AGR/13
Corso di studi
SCIENZA DELLE PRODUZIONI VEGETALI
Commissione
tutor Prof. Saviozzi, Alessandro
tutor Dott. Guidi, Lucia
Parole chiave
  • Taraxacum officinale Web.
  • soil enzymatic activities
  • plant bioindicator
  • heavy metals pollution
  • geostatistical analysis
  • urban environment quality
  • urban soils
Data inizio appello
23/11/2012;
Consultabilità
completa
Riassunto analitico
The European Union, in the “Thematic Strategy on the Urban Environment” (2006),<br>has pointed out the importance of identification and monitoring urban environment<br>quality indicators. In this scheme, the quality of 31 urban green areas in Pisa was assessed<br>by monitoring topsoil physical, chemical and biological features and by using the plant<br>bioindicator Taraxacum officinale Web. Results were compared with an extra-urban area<br>(near S.Rossore-Migliarino-Massaciuccoli Natural Park) and with the quantitative limits<br>fixed by Italian Law (DLgs 152/2006). The soils of the green areas of Pisa were mostly<br>sandy, sub-alkaline, and lightly calcareous, with rather high organic matter content. They<br>showed a widespread pollution by hydrocarbons, probably caused by road traffic<br>incomplete combustion and by domestic heating. Only in few sites the total amounts of<br>Cd, Cr and Hg were significantly higher than the minimum value established by the<br>Italian Law. Probably due to the vehicular traffic, pollution by Pb, Cu and Zn was instead<br>widespread. A sequential extraction (BCR method) was performed for determining the<br>forms of heavy metals within the soil matrix. Instead of Zn and Pb, Cr and Cu showed the<br>absence in soil of the labile forms. As far as Cr forms were concerned, the most<br>represented one was the residual, while the anthropogenic addition of the element was<br>found in the oxidizable form. For Cu forms, the most represented was the residual, while<br>reducible and oxidizable forms were enriched by anthropogenic addition of the element.<br>Regarding Pb and Zn forms, the most represented one was the reducible, while the<br>anthropogenic additions of the elements were evenly distributed among the four fractions.<br>Principal component analysis revealed the existence of four different patterns of<br>distribution of the elements, whose differences have been attributed at the origin, each<br>composed of a different number of variables: the first one, consisting of As, Cd, Cr, Cu, Pb,<br>Sb, Sn, Sr, and Zn, whose main source was fit to identify in the traffic; as to the second<br>factor, consisting of Fe, Mn, and Ni, the main source was identified by pedogenic<br>substrate. Each of the third and the fourth factor was composed of a single element,<br>respectively Cr and Hg, which had a particular distribution, different from that of all other<br>HMs. Even the geostatistical analysis has identified the previous four patterns of<br>distribution of HMs, bringing back, through interpolation techniques, also their coarse<br>spatial distribution; according to this analysis, the central area of the city was identified as<br>the one having the most polluted green areas. Hierarchical clustering analysis identified<br>different groups of areas with different levels of contamination, both from the qualitative<br>and quantitative point of view. Platinoids (Pt, Pd), “new generation” pollutants, released<br>from recently introduced three way catalytic converters, absent in the substrate, showed a<br>beginning of accumulation in a limited number of areas. As to soil biological features,<br>cumulative respiration of monitored areas was evaluated during a 25 day incubation<br>period. Results showed that evolved CO2-C was different among the monitored areas and<br>influenced by soil carbon total content and pollution level. Community level physiological<br>profiling of soil microbial population of the monitored areas was performed by using Biolog Ecoplates. The relative data of AWCD, CMD and H (Shannon-Weaver index of<br>biodiversity) showed a limited variability among the monitored areas. Soil antioxidant<br>capacity was evaluated and showed changes among monitored areas, being correlated<br>with organic carbon content and, in particular, with phenolic substances. Soil enzymatic<br>activities vary among monitored sites and appear to be influenced by organic matter and<br>pollutants’ contents. The control site has shown the lowest rate of activities if compared to<br>all the other sites. Positive correlation was detected among all enzymatic activities except<br>for dehydrogenase. In spite of the presence of various pollutants, vegetal bioindicator<br>Taraxacum officinale Web. did not show any alteration in the photosynthetic process with<br>values of Fv/Fm, and FPSII, representing respectively the efficiency of PSII in conducting<br>photochemical events and photochemical yield of PSII, typical of the leaves of healthy<br>plants. Even photosynthetic pigment contents and qNP, representing mechanisms aiming<br>at dissipating excess excitation energy, did not show any alteration among the monitored<br>areas. That trend was confirmed by other parameters, monitored in order to understand if<br>the polluted urban environment is not dangerous for the plant or if vegetal put into<br>repairing actions. On the dissected aboveground and radical portions of the biomarker,<br>antioxidant capacity, phenolic content, heavy metals contents and metal chelating capacity<br>of vegetal tissues did not reveal any differences among the monitored sites, probably<br>showing the dandelion ability in non-absorbing pollutants. We can finally conclude that<br>the degree of pollution of the green areas in the city of Pisa, although present, does not<br>cause major problems to the utilized bioindicators. We need more sensible biomarkers to<br>effectively detect this degree of pollution.
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