1
Abstract
The intense development and exploitation of the marine areas, with special reference to coastal zones, that date back to ‘50s, have caused sound changes to the environment, often associated to negative effects on various habitats and human beings.
Commercial activities, tourism and marine transports, in general, forced a rapid growth of ports and of the coastal infrastructures both in Italy (having about 8000 km of coasts) and in Europe.
A first and basic step to guarantee an efficient development of ports and marine coastal areas is a correct management of their bottom sediments.
This is necessary both for providing appropriate depths for the nautical traffic both for estimating the sediment quality from a chemical point of view.
The National Priority Sites (i.e. S.I.N.) have been established in the D.M. 471/99, related to the specific polluted site features, their extension, the population density of the area, the possible risks caused by a great amount of pollution and, last but not least, the human and ecological risks.
The 426/98 Italian law has drawn up a list of 15 sites, defined as S.I.N.. Among them Massa Carrara and Piombino are located in Tuscany, a region situated in the centre of Italy.
Up to today the S.I.N. in national territory are 54 and thanks to the last improvement plan from the Environmental Department, funds have been allocated to restore (when possible) in these zones the natural conditions.
This graduation thesis is a part of a wider project aimed at charactering the sediments of the S.I.N. Marina di Carrara.
The investigated area can be divided into a terrestrial zone and a marine area of about 1.902 ha, that is located between the harbour and the industrial plant of Marina di Carrara (northern border) and the area of Marina di Massa (southern border).
Hence, the study area extents for 3 km from the coast to the open sea.
The project includes the following analyses: grain size, water content, specific weight, pH, redox, Al, As, Cd, Cr, Fe, Hg, Ni, Pb, Cu, Zn, V, PCB, organic- clorinate-pesticides, IPA, total hydrocarbons (C>12, C<12), N, P, TOC;
2 BTEX, TBT, microbiological parameters, and biotest to estimate the sediment toxicity.
In this paper the attention has been focused on heavy metals. The first objective wasthe creation of marine thematic charts with “isoconcentration”
lines representing the metal concentration determined in the sediments. A thematic chart has been created for those metals whose concentrations exceed the law-limits (i.e. “Valori di Intervento” ICRAM) and for Cadmium and Mercury as well being considered prioritary and hazardous elements by the European law (2455/2001/CE).
The second objective was to search for the presence of spatial patterns according which the metals are distributed. Additionally correlations among them were calculated.
According to the sampling design, defined by ICRAM, the marine area up to 600 m from the coast, was divided in sub-areas 150x150 m wide where a sampling station was located. A total of 150 sampling points were set.
The area beyond 600m from the coast was investigated collecting three samples distributed along transects perpendicular to the coast.
In addition 17 sampling stations were planned to characterize the littoral sandy stretch included in the S.I.N.
Superficial samples were collected by Van Veen grab whereas the deeper ones by a vibro-core. In this second case is the core collected was divided into four sub-samples: 0-20cm, 30-50cm, 100-120cm, 180-200cm.
After the field activities, all the samples were frozen before the chemical analyses. Heavy metal concentration was determined by the standard procedure, such as EPA Method 3051a (modified) for ICP-AESPlasma Liberty AX-Sequential Varian (Al, Cr, Fe, Ni, Cu, V, Zn), EPA Method 7010 for Spettrofotometer AA220Z with grafite fournace (As, Cd, Pb), and EPA Method 7374 for AA Spectrometry with Mercury cold vapour Coleman 50B (Hg).
After the analyses a total of of 6600 records were obtained (150 cores * 4 levels * 11 metals) whose interpretation is very difficult.
Hence we firstly used the software Broadgard to subject the data matrix to P.C.A. “Principal Components Analysis” a multivariate procedure that provides an ordination of the sample points based on a subsequently variance
3 extraction. This procedure allows to identify an hypothetic spatial pattern related to a particular variable (metal) or linear combination of variables according which the sample points can be ordinated.
The same software was used to calculate the percent correlation between couples of metals.
Secondly the G.I.S. (Geographical Informatic Sistem) was used for georeferring the sampling stations in a geographical chart where the “iso- concentration” line of some metals were superimposed. The statistical interpolation of the data (G.I.S. Tool) allowed to create marine thematic charts using a chromatic scale choosen according to the range of concentrations of the various metals and taking into account the law-limits reported in the technical reports published by ICRAM (i.e. Vaore di Intervento, Baseline Chimical Level L.C.B., Limit Chimical Level L.C.L.).
The results suggested that a high level of correlation exists among these groups of elements: V, Zn, Fe, Al, Cu; Cd, As Hg, Pb; Ni, Cr. The highest values were recorded between Ni/Cr, always higher than 70%.
The PCA did not reveal a particular spatial pattern as well as the elaborations obtained by G.I.S.
All the results suggested that the sediments of the investigated area (Marina di Carrara) were slightly contaminated by heavy metals only Ni showed concentrations higher than the law-limits in all the sedimentary profile.
Moreover the contamination was more evident in the northern part of the investigated site, whereas the southern part and the zone more distant from the coast were almost uncontaminated.
The more interesting question is to discriminate the amount of Ni of natural origin from that coming out from anthropogenic activities. That is why it is desirable that in a near future the sequential extraction procedure will be included in these characterisation studies, because It is an appropriate tool separate the amount of Ni put into the environment by human activities from that naturally present in that area.
Although the Italian legislation has received a good pulse in the last ten years on these topics, there is still much to do. The LCB and LCL, for examples, should be revisited taking into account the local heterogeneities of the different areas distributed along the Italian coast.
