Phytoextraction and hydrological phytocontrol in an industrial site contaminated by heavy metals and arsenic
Author(s)
Pietrosanti, Lucia
Date Issued
March 30, 2010
Type
Doctoral Thesis
Abstract
The aim of this study was to investigate the utility of some spontaneous and cultivated plants in a phytoremediation strategy and to analyse the capability of a poplar plantation in remediate soil and in water
control of an industrial contaminated site. Moreover an experiment was performed to investigate ex-situ the tolerance and accumulation capability of Pteris vittata L., an As-hyperaccumulator, to elevated Arsenic concentration with in order to introduce this specie in the contaminated site.
The experimental field is an island of the industrial zone of Porto Marghera (Venice lagoon, Italy), called “Isola dei Petroli, classified as one of the most important “contaminated sites of national interest”
(SIN) in Italy and considered as an area of high environmental risk which needs to be reclaimed. The island is 12 ha and has been used as an industrial landfill. Previous study described the island as highly
contaminated by As, Cd and Zn mainly in soil depth range of 1-2 m. Since 2008 the island was wholly separated from surrounding sea by a waterproof barrier to avoid environmental contamination. This manufacture bounds the contamination scattering bat also it modifies the water balance of the island,
annulling all exchanges island-sea.
In this context a vegetation cover could be useful to remove water in excess, but soil toxicity could affect the growth plants. So an investigation of species both spontaneous and cultivated grown in the island
are performed to analyse their utility in a phytoremediation and phytocontrol of hydrological balance strategy and their capability to survival in the contaminated site.
The laboratory analyses and the ex situ study are performed in the IBAF, in the CNR centre in Montelibretti.
It’s possible divide this work in 3 parts
PART I - A SURVEY ON THE METAL AND METALLOID PHYTOEXTRACTION ABILITY OF
SPONTANEOUS AND CULTIVATED PLANTS GROWING IN THE LANDFILL OF AN INDUSTRIAL SITE IN THE
VENICE LAGOON.
The aim of this part was to investigate the capability of different spontaneous and cultivated plant species growing on island to examine their potential use for a phytoremediation strategy. In particular this
part focused on the most abundant tree, shrub and herbaceous species in the island.
In soil of different depths and in the groundwater table, a large degree of heterogeneity in metal contamination, with values close to or higher than Italian guideline values (by Italian law D.Lgs 152/06), was found. Plants differed in pollutant accumulation. All spontaneous species, except for Amaranthus retroflexus
L. towards zinc, showed a higher ability to exclude rather than accumulate heavy metals compared with cultivated species, making them unsuitable for the in situ phytoremediation of a contaminated industrial area.
On the contrary, in cultivated species a valuable heavy metal concentration in above-ground organs was detected. In particular, good performances were evidenced for Chrysopogon zizanioides (L.) Roberty to
bioconcentrate Pb and for both Salix matsudana Koidz. and Salix alba L. to bioconcentrate Cd and Zn,
allowing the evaluation of the possible utilization of these species for the phytoremediation of contaminated
sites.
PART II - SITE REMEDIATION AND HYDROLOGICAL CONTROL IN LANDFILLS: STUDY ON A
POPLAR PLANTATION IN AN INDUSTRIAL SITE IN THE VENICE LAGOON.
This part aimed to verify if in the industrial site a poplar plantation was useful both in site reclamation strategy and in the hydrological control of the site. The plantation consisted of three poplar
clones: two Populus deltoides Bartr. Ex Marsch clones (Dvina, Lena) and one Populus x canadensis Moench clone (Neva). P..To investigate the poplar capability in accumulate As, Cd and Zn plant material, soil and groundwater table were sampled from 2006 to 2008 while to study the hydrological control by the plantation, plant transpiration was measured by Granier sensors during the three years.
The results showed as the poplar plantation was able to regulate the hydrological balance of the site during growing season, with the exception of occasional heavy thunderstorms at the end of summer.
Differences among clones were found for extraction efficiency of pollutants: Cd and Zn are more bioconcentrated than As and clone Neva seems to show the best performances.
PART III - A LONG-TERM EXPERIMENT TO TEST P. VITTATA L. UNDER HIGH AS
CONCENTRATION.
This study was aimed to investigate the tolerance and accumulation capability of Pteris vittata L. exposed to a remarkable As concentration in a long-term semi-hydroponic experiment, evaluating some
implications at physiological and biochemical level.
After 17 weeks in pre-treatment condition, Na2HAsO4·7H2O was added to solution in two times to reach a concentration of 7 mg/l in the acclimatizing phase of 13 days and then of 21 mg/l in the treatment phase for
seven weeks. At the end of treatment plants were sampled and divided into fronds, rhizome and roots.
Biomass, As concentration, Cys, GSH, PCs, chlorophyll fluorescence image and chlorophyll content analysis were performed.
It can be highlighted that organs developed during As treatment can maintain a valuable
physiological status despite of the elevated As concentration in their tissues and that the main changes in the chlorophyll fluorescence parameters due to As treatment were the large reduction in ΦPSII (45%) and the notable increase in NPQ (350 %).
Additional information
Dottorato di ricerca in Ecologia forestale
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