Investigation on Pollution Level in Surface Sediments of Coastal Area, the Case of Naples and Salerno Gulfs, and in situ Laboratory Raman Researches

Abstract

Environmental geochemistry is a major branch of regional geochemistry. In this thesis are presented the environmental geochemical investigation of Campania Plain and Naples and Salerno Gulfs in South Italy, concerning potential toxic elements and organic compounds distribution. Multivariate and univariate analysis are used to illustrate distribution and sources of elements and organic compounds, both on land and in sea sediments for Naples and Salerno Gulfs. Different pollution impact factors and risk assessment factors are estimated for soils and sediments that easily comes to contact with human beings. The results suggest that Naples city territory, and Naples and Pozzuoli Gulfs are characterized by highly incremental lifetime cancer risk. An attempt of applying in situ Raman spectroscopic detection of pollutants started with a series of laboratory experiments. With the help of capillary high pressure optical cell, following results are achieved: 1) methane diffusion coefficients in water under high pressure and wide temperature range, and the relationship of diffusion coefficients with temperature was established; 2) Raman intensity ratio of asymmetric stretching vibration (ν3) and asymmetric bending overtone (2ν2) of methane were numerically described vs temperature, pressure and gas phase density; 3) reactions of goethite and magnetite with sulfide solutions under CH4 and/or CO2 atmospheres were monitored at room temperature. Pyrrhotite and mackinawite were observed in final products. A demanding of innovative approach to detect organic contaminants encourages various researches to improve in-situ techniques. A new substrate embedding silver nanoparticles into siloxane polymer is used as the platform to generate Surface-Enhanced Raman Scattering (SERS). Polymer serves as supporting material of silver nanoparticles as well as a stationary phase. After a short period of extraction, certain partition of organic compounds from aqueous solution accumulates into polymer. When silver nanoparticles is in touch with organic compounds, enhanced Raman scattering is obtained with 104~106 orders of magnitude. Raman scattering is obtained. Because of these two-steps amplification, SERS, which is typical applied strictly at lab condition, could be compromised when applied for field survey. Crystal violet (CV) is chosen to evaluate extraction properties of polymer. Color “transferring” indicates effective extraction of crystal violet into polymer. Intensive Raman bands include SERS effects and resonance scattering of CV. Low concentration of 4-nitrophenol (PNP) and 4-nitroaniline (PNA) in solution (as low as 10-7 M) are dropped onto substrate and generate SERS fingerprint. After subtracting Raman bands of polymer and silver salts, clear evidence indicates availability of macro SERS spectra. Micro SERS testifies compounds penetrating as depth as 200 µm from the surface.