Alba Giacalone

POLYCYCLIC AROMATIC HYDROCARBONS IN SEDIMENTS OF MARINE COASTAL LAGOONS IN MESSINA (ITALY). EXTRACTION AND GC-MS ANALYSIS. DISTRIBUTION AND SOURCES.

The content of 21 polycyclic aromatic hydrocarbons (PAHs) were determined in 16 samples of sediments collected from Ganzirri and Faro marine coastal lagoons in Messina, Italy. Analysis was performed by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM) mode. The total concentration of polycyclic aromatic hydrocarbons (ΣPAHs) ranged from 74 to 5755 μg/kg of dry matrix. The resulting distributions and molecular ratios of specific compounds are discussed in terms of sampling location and origin of organic matter. The results obtained show that levels of contamination are not homogeneous throughout the stations, while the relative distributions of PAHs are homogeneous in most of the sampling stations. The organic matter content and PAH concentration were found to be correlated (r = 0.90). It is also shown that the pyrolytic origin is the main source of these compounds in Ganzirri and Faro Lakes sediments.

Speciation of Al3+ in fairly concentrated solutions (20–200 mmol L−1) at I=1 mol L−1 (NaNO3), in the acidic pH range, at different temperatures

Abstract The hydrolysis of Al3+ was studied in aqueous 1 mol L−1 NaNO3 solution at different concentrations (20–200 mmol L−1) and temperatures (283.15–343.15 K) by potentiometry (ISE-H+, glass electrode). Many different speciation models were considered in the calculations and it was found that the best model is represented by the following species: Al(OH)2+, Al(OH)45+, Al13(OH)327+. Hydrolysis constants and enthalpy changes at different temperatures are reported.

Metals distribution in the organic and inorganic fractions of soil: a case study on soils from Sicily

Abstract The content of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, has been determined in the organic and inorganic fraction of eight soil samples from Sicily. A modified type-Tessier sequential extraction procedure has been used to recognize metals in five different fractions categorised as follows: (a) exchangeable metals, (b) metals bound to carbonates, (c) metals bound to iron and manganese oxides, (d) metals bound to organic matter, and (e) metals in residual fraction. The mineralogical composition of soils samples was characterized by X-ray diffraction. Humic substances were extracted by means of an alkaline extraction procedure. It has been found that both the mineralogical composition and the different content of humic fraction of organic matter in the soils investigated are responsible for the observed trace metal distribution. The obtained data show that a significant amount of trace metals is bound to the organic fraction where different binding sites are present simultaneously. In particular, Pb and Cu seem to be the elements more tightly linked to the organic fraction of soils, whilst cadmium is mostly concentrated into the iron and manganese oxides fraction. The presence of clay minerals in soil is significant for metal distribution, playing a fundamental role in binding metal ions. Besides, it has been observed that the calcophile metal mobility is strongly dependent on the presence of sulfide phases. Applying the Risk Assessment Code to the analyzed soils, it appears that they contain, generally, less than 30% of metals in the exchangeable and carbonate fractions. Calcic brown soil from Piano Zucchi exhibits a medium up to very high risk for Pb, Cd, Co, Zn and Mn. It also been recognized the elevated presence of Cd in the exchangeable and carbonate fractions of andic brown soil on volcanites from Pachino.

Speciation of dimethyltin(IV) – and trimethyltin(IV) – carbocysteinate and – glutamate systems in aqueous media

Abstract The formation of complex species in the dimethyltin(IV) and trimethyltin(IV)-carboxymethyl-L-cysteinate (carbocysteinate) systems in NaClaq, at different ionic strengths, and in a multicomponent Na+, K+, Ca2+ ,Mg2+, Cl− and SO42-− medium representative of the seawater major composition, is discussed. Experimental results give evidence for the formation of the following species (L = carbocysteinate): [(CH3)2Sn(L)]0, [(CH3)2Sn(HL)]+, [(CH3)2Sn(OH)(L)]−, [(CH3)2Sn(OH)2(L)]2− in the DMT–CCYS system, and [(CH3)3Sn(HL)]0, [(CH3)3Sn(L)]− and [(CH3)3Sn(OH)(L)]2− in the TMT-CCYS system. The ionic strength dependence of formation constants was taken into account by an extended Debye Hückel type equation and by the SIT (Specific ion Interaction Theory). Measurements were carried out also on the dimethyltin(IV)-glutamate and trimethyltin(IV)-glutamate systems in NaClaq, owing the strict similarity of glutamate and carbocysteinate. Results obtained show the formation of complex species having the same stoichiometry as those formed in the DMT- and TMT-carbocysteinate systems, with very similar stability, confirming that carbocysteinate behaves as a dicarboxylic amino acid without involving the sulfur-bridge potential binding site in metal coordination.