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Environmental Problem Targeted
The past century witnessed a relevant increase in global pollution due to the high production and use of petroleum derived compounds which were carelessly released into the environment. As a consequence numerous organic contaminants are now present in soils and water of terrestrial polluted sites. Furthermore industrial plants, mining industry, road transport and the unwise application of fertilizers (Lado et al., 2008) increased the extent of soil pollution by potentially toxic elements (PTEs), (Black, 1999; Glass, 1998) which represent a relevant environmental concern due to their potential accumulation in the food chain.

In Campania region, Southern Italy, (Napoli Orientale, Litorale Domitio-Agro Aversano NIPS L. 426/98, Napoli bagnoli coroglio L. 388/2000, Litorale Vesuviano L. 179/2002, Bacino idrografico del Sarno L. 266/05; Aree di Pianura DM 445/2008) there were identified four National Interest Priority Sites (NIPSs), for a total surface of about 200.000 ha, with different levels and sources of pollution. In urban areas included in Napoli Orientale and Bagnoli-Coroglio NIPSs, petroleum derived compounds storage, iron and steel industry and asbestos cement production are the main sources of pollution, while unwise municipal solid waste management was recognized as the main source for Litorale Vesuviano. Litorale Domitio-Agro Aversano NIPS includes a large part of the polluted agricultural land, belonging to more than 61 municipalities in the Naples and Caserta provinces. In this area a high level spotted soil contamination is moreover due to the legal and outlaw industrial and municipal wastes dumping, with hazardous consequences also on the quality of the water table. In example in Giugliano municipality the environmental national protection agency is carrying out the monitoring of 190 wells in order to assess the quality of the water for irrigation.

Previous analyses evidenced in some points high contents of tri- and tetrachloroethylene, organic pollutants with a very high cancerogenic potential. These compounds are bound to the dumping of about 1300000 Mg of wastes in the RESIT area and in Scafarea dumping area, including about the 50% of hazardous special wastes. It was also been identified an area of about 700 ha known as Laghetti di Castelvolturno in which high levels of lead and antimony were detected in soil since this area was a shooting range for a long period. On the other hand a spread and low level contamination is mainly due to the use of low quality compost and in surface depositions of particles from waste combustion. In both cases the agricultural activities could be compromised threatening the supply chains of PDO products such as the “Mozzarella di Bufala Campana”, with high economic, social costs for the population. Moreover there is a general perception of health risks due to the contamination of human food and air; recent studies carried by the Iinternational Society of Doctors for the Environment evidenced a 20% increase of human cancers in Naples and Caserta provinces. As known, “Environment and health” is one of four priority areas outlined in the 6th Environmental Action Programme, which defines the European Community environmental policy for the next ten years.

The fundamental objective is to promote a quality environment where levels of man-made pollutants, do not have a significant impact on or pose a risk to human health. In this regard, the action programmed calls to follow specific indications of Target EU Legislation about Nature protection and Biodiversity Directive of 92/43/EEC -"Conservation of natural habitats and of wild fauna and flora" (21.05.92); Council Decision 93/626/EEC -"Conclusion of the Convention on Biological Diversity" (25.10.93); COM (98) 42 final -"Communication on a European Community Biodiversity Strategy" (05.02.98); COM (2001)162 final -"Biodiversity Action Plan for the conservation of natural resources (vol. I ).

State of the art

Soil restoration by physicochemical techniques is so expensive that a large part of sites remains contaminated and leds to a strong reduction of soil fertility due to their toxicity that makes these soils not more suitable for agriculture thus changing their destination to residential, commercial and industrial. For these reasons there is a consistent need of agriculture-based soil restoration techniques. The reduction of soil disturbance due to the presence of long standing crops, together with the C inputs from belowground biomass and from compost fertilization, will allow a significant increase in soil organic matter. Garten et al (2011) reported an input of 6 Mg dw ha-1 from Poplar roots in a 7 year short forestry rotation and an annual increase of 1.8 Mg C. Mao et al (2010) found a 1 Mg SOC ha-1 yearly increase for a 20 year Poplar stand. Monti et al (2009) reported an input from Giant reed roots of about 14 Mg dw ha-1 y-1 corresponding to increase of about 1.5 Mg C y-1. For these reasons, an increase of 3 Mg C ha-1 seems to be an achievable target in the 5 years cropping long standing biomass crops.

BIOREMEDIATION represents a really attractive technology, for reducing concentration of organic pollutants (EPA-Guidelines, 2005), with a target of 40% removal of them form contaminated soils. However, an important limiting factor could be the slow degradation rate due to the harsh environmental condition. This drawbacks can be overcome by a biofilm-mediated approach. A biofilm is a “community” made up of a consortium of several species of bacteria, fungi, algae, yeasts, protozoa, embedded within a self-produced matrix of extracellular polymeric material, adhering to a living (roots, leaves, animal tissues) or non-living surface. Its main role is to act as a physical barrier between the environment and the microorganism, to ensure survival in harsh conditions by maintaining optimal conditions of pH, localized solute concentrations and redox potential in the vicinity of the cells.

The key factor of PHYTOEXCTRACTION is the metal accumulating ability of plants that remove heavy metals (HM) from soil. Rhizosphere could also detoxify organic pollutants, due to the positive effects of root exudates in the selection of specific soil microbiota able to breakdown contaminants. Phytoextraction has been tested for long periods using hyper accumulating plants able to extract unusually high amount of metal and efficiently translocate to shoots, but the low biomass accumulation (Kramer, 2005) disqualify them from commercial phyoremediation of HM polluted sites. Moving from this evidence, the use of high biomass plants tolerant to HM such as A.donax could be an interesting tool for clean up soils in a reasonable reclamation time (Lombi et al., 2001). Moreover high biomass crops allow profit making operations such as BIOENERGY PRODUCTION.

METALS BIOAVAILABILITY can be increased by synthetic chelate such as EDTA, but it is not practicable in open field since the high environmental persistence could led to HM leaching in watertable (Meers et al., 2004). As shown by Nascimiento et al 2006 low molecular organic acids such as citric and gallic acids are able to increase HM bioavailability without environmental risks, while Humic acids could be also an interesting tool to increase HM availability, soil fertility and degradation of organic pollutants, thanks to their positive effect on soil microbia and to the interaction with apolar compounds.

Interesting results could also be achieved by a modification of MICROBE-PLANT ASSOCIATION IN RHIZOSOIL. Fungi are well recognized for their ability to detoxify HM trough passive and active uptake. Among them Trichoderma spp., emerged for high detoxification potential, colonization ability and plant growth promoting activity (Vinale et al., 2003; 2009) that allowed a significant increase of metal uptake.

The Phytoextraction efficiency of high biomass crops is difficult to quantify, since it depends on the initial soil HM concentration, the adopted crop and the metal availability. Wang et al (2009) tested the poplar phytoextraction potential on soils with a Cd content of 1.6 mg kg-1, finding a total biomass content of 2.2 mg Cd kg-1 after two years. This value could increase at lest of one order of magnitude (25 mg kg-1) if soil Cd content is 5 mg kg-1 (Baum et al., 2006), that according to an average biomass production of 10 Mg dw ha-1 means 250 g Cd ha-1. For these reasons a target uptake of 125 g Cd ha-1 y-1, seems to be achievable for our pilot scale testing, since phytoexctraction will be also assisted increasing metal bioavailability with organic matter inputs and improving root uptake by mycorrization. According to a dataset from ARPAC, polluted agricultural soils of Campania region have usually HM content slightly higher than the legal threshold. Focusing on Cd, recognized as one of the most hazardous, a pollution level about 3 mg Cd kg-1 is the most frequent in agricultural soils. This value is 1 mg kg-1 above the legal limit, corresponding to 3 kg Cd ha-1 in the 0.20 m soil layer. In such a case, a SRF poplar based phytoextraction system will be able to remove about 20% (0.125/3 kg Cd ha-1) by harvesting aboveground biomass on a 5 year period. The removal could reasonably increase of 2% if roots are harvested at the end of that period.

The novelty of our project is the pilot scale validation of an assisted phytoremediation protocol at different soil contamination levels, to produce a technical instrument suitable for environmental policy in Litorale Domitio e Agro Aversano NIPS. This aspect is relevant if we consider that assisted phytoremediation is usually tested at lab scale or in controlled environments, improving the general knowledge of the remediation process without giving any information about is real effectiveness. Furthermore the link of the project with the main ecological and economic concerns of the Campania region is particularly emphasized. Referring to the long standing rubbish problem, the application of compost from municipal solid wastes and from residues of olive oil production, represents a key factor in the waste recycling allowing also an increase of the soil carbon content.