Chitosan-Capped Au Nanoparticles for Laser Photothermal Ablation Therapy: UV-Vis Characterization and Optothermal Performances

We have reported on the synthesis and characterization of near-infrared- (NIR-) absorbing colloidal nanoparticles prepared by exploiting the one-step reaction of HAuCl4 and Na2S2O3, followed by their stabilization with chitosan. This reaction also produces a big amount of unwanted nanoparticles detuned with respect to the NIR spectral region. For this reason, it is usually assumed that the product has to be filtered and enriched to enhance its NIR absorption, and the possible exploitation of the simpler raw product has never been worthy to be considered. Aiming to investigate this missing aspect, we chose to avoid the purification steps and rather focused on the preparation of the unrefined colloid, identifying the synthesis conditions that maximize its NIR absorbance and, subsequently, testing it as an optothermal transducer by measuring its molar heating rate (MHR). As expected, we found that the performances of the raw colloid are indeed lower than those of its refined version, but only to a limited extent. Moreover, MHR is unexpectedly higher than that deducible for other classical NIR-absorbing nanoparticles, like Au nanorods or Au nanostars. Thus, the product of the simpler preparation protocol appears as a competitive trade-off solution between easy manufacturing and optothermal performances

Spatial distribution of biogenic sulphur compounds (MSA, nssSO4 2- ) in the northern Victoria Land-Dome C-Wilkes Land area, East Antarctica

AbstractDuring the 1992–2002 Antarctic expeditions, in the framework of the International Trans-Antarctic Expedition (ITASE) project, about 600 sites were sampled (superficial snow, snow pits and firn cores) along traverses in the northern Victoria Land–Dome C–Wilkes Land region. The sites were characterized by different geographical (distance from the sea, altitude) and climatological (annual mean accumulation rate, temperature) conditions and were affected by air masses from different marine sectors (Ross Sea, Pacific Ocean). Mean anion and cation contents were calculated at each site, in order to evaluate the spatial distribution of chemical impurities in snow. Here we discuss the distribution of non-sea-salt sulphate (nssSO42–) and of methanesulphonic acid (MSA) mainly originating from atmospheric oxidation of biogenic dimethyl sulphide; these compounds play a key role in climate control processes by acting as cloud condensation nuclei. The spatial distribution of nssSO42– and MSA is discussed as a function of distance from the sea, altitude and accumulation rate. Depositional fluxes of nssSO42– and MSA decrease as a function of distance from the sea, with a higher gradient in the first 200km step. There is an analogous trend with the site altitude, and the first 1600m step is relevant in determining the nssSO42– and MSA content in snow. The nssSO42–/MSA ratio depends on the distance from the sea and the biogenic source strength. At coastal sites, where biogenic inputs are dominant, this ratio is ~2. As biogenic input decreases (low MSA content) inland, the ratio increases, indicating the presence of alternative sources of nssSO42– (crustal, volcanic background) or advection of low-latitude air masses. By plotting total flux as a function of accumulation rate, dry depositional contributions were evaluated for nssSO42– and MSA in the Ross Sea and Pacific Ocean sectors. Non-sea-salt sulphate wet deposition prevails at sites where the accumulation rate (expressed as water equivalent) is higher than 70 kgm–2 a–1 (Ross Sea sector) or 370 kgm–2 a–1 (Pacific Ocean sector). MSA threshold values in these sectors are respectively 90 and 220 kgm–2 a–1

Aluminium and iron record for the last 28 kyr derived from the Antarctic EDC96 ice core using new CFA methods

AbstractSpectrofluorimetric and spectrophotometric continuous flow analysis (CFA) methods were developed and applied to the determination of aluminium and iron in EPICA Dome C (East Antarctica) ice-core samples (6–585m depth). The methods are able to measure the fraction of Al and Fe which can be detected once the sample is filtered on a 5.0 μm membrane and acidified to pH 2. Both the methods present high sensitivity (detection limit of 10 ng L–1 for Al and 50 ng L–1 for Fe) and reproducibility (5% at sub-ppb level). The Fe and Al profiles show sharp decreases in concentrations in the last glacial/interglacial transition, reflecting the decreasing dust aerosol load. The two elements show a different pattern during the Antarctic Cold Reversal (ACR) climatic change, with high iron concentrations (similar to the glacial period) and low but increasing Al content during the ACR minimum. In order to interpret the Al and Fe data obtained by CFA, a comparison with Al and Fe composition, as measured by inductively coupled plasma sector field mass spectrometry (ICP-SFMS), was performed for Holocene, ACR and glacial periods. The percentage of CFA-Al with respect to ICP-SFMS-Al in the three periods shows a lower variability than CFA-Fe (3% in the glacial period and 64% in the ACR). This pattern may be explained by the different dominant iron sources in the different climatic periods. During the Last Glacial Maximum, Fe is proposed to arise mainly from insoluble continental dust, while a variety of ocean-recycled Fe, mainly distributed in fine particles and as more soluble species, shows a higher contribution in the ACR and, to a lesser extent, in the Holocene

Sea-spray deposition in Antarctic coastal and plateau areas from ITASE traverses

AbstractSea-salt markers (Na+, Mg2+ and Cl–) were analyzed in recent snow collected at more than 600 sites located in coastal and central areas of East Antarctica (northern Victoria Land–Dome C–Wilkes Land), in order to understand the effect of site remoteness, transport efficiency and depositional and post-depositional processes on the spatial distribution of the primary marine aerosol. Firn-core, snow-pit and 1m integrated superficial snow samples were collected in the framework of the International Trans-Antarctic Scientific Expeditions (ITASE) project during recent Italian Antarctic Campaigns (1992–2002). The sampling sites were mainly distributed along coast–inland traverses (northern Victoria Land– Dome C) and an east–west transect following the 2100m contour line (Wilkes Land). At each site, the snow ionic composition was determined. Here, we discuss the distribution of sea-spray components (Na+, Mg2+ and Cl–) as a function of distance from the sea, altitude and accumulation rate, in order to discover the pulling-down rate, possible fractionating phenomena and alternative sources moving inland from coastal areas. Sea-spray depositional fluxes decrease as a function of distance from the sea and altitude. A two-order-of-magnitude decrease occurs in the first 200km from the sea, corresponding to about 2000ma.s.l. Correlations of Mg2+ and Cl– with Na+ and trends of Mg2+/Na+ and Cl–/Na+ ratios showed that chloride has other sources than sea spray (HCl) and is affected by post-depositional processes. Accumulation rate higher than 80 kgm–2 a–1 preserves the chloride record in the snow. Sea-spray atmospheric scavenging is dominated by wet deposition in coastal and inland sites

Volcanic Fluxes Over the Last Millennium as Recorded in the Gv7 Ice Core (Northern Victoria Land, Antarctica)

Major explosive volcanic eruptions may significantly alter the global atmosphere for about 2-3 years. During that period, volcanic products (mainly H2SO4) with high residence time, stored in the stratosphere or, for shorter times, in the troposphere are gradually deposited onto polar ice caps. Antarctic snow may thus record acidic signals providing a history of past volcanic events. The high resolution sulphate concentration profile along a 197 m long ice core drilled at GV7 (Northern Victoria land) was obtained by Ion Chromatography on around 3500 discrete samples. The relatively high accumulation rate (241 +/- 13 mm we yr (-1)) and the 5-cm sampling resolution allowed a preliminary counted age scale. The obtained stratigraphy covers roughly the last millennium and 24 major volcanic eruptions were identified, dated, and tentatively ascribed to a source volcano. The deposition flux of volcanic sulphate was calculated for each signature and the results were compared with data from other Antarctic ice cores at regional and continental scale. Our results show that the regional variability is of the same order of magnitude as the continental one

Source Apportionment of PM2.5 in Florence (Italy) by PMF Analysis of Aerosol Composition Records

An extensive field campaign was carried out in Florence (Tuscany) to investigate the PM2.5 composition and to identify its sources. The scientific objective of this study is providing a reliable source apportionment, which is mandatory for the application of effective mitigation actions. Particulate matter (PM) was collected for one year, simultaneously in a traffic site, in an urban background, and in a regional background site. While the use of two filter types (quartz and Teflon) allowed obtaining a comprehensive chemical characterization (elemental and organic carbon, ions, elements) by the application of different analytical techniques, the location of the three sampling sites allowed getting a better separation among local, urban, regional and transboundary sources. During shorter periods, the aerosol was also collected by means of a streaker sampler and PIXE (Particle Induced X-ray Emission) analysis of these samples allowed the assessment of hourly resolution elemental time trends. Positive matrix factorisation (PMF) identified seven main sources: traffic, biomass burning, secondary sulphate, secondary nitrates, urban dust, Saharan dust and marine aerosol. Traffic mass concentration contributions were found to be strong only at the traffic site (~8 μg·m−3, 33% of PM2.5). Biomass burning turned out to be an important PM2.5 source in Florence (~4 μg·m−3), with very similar weights in both city sites while at the regional background site its weight was negligible. Secondary sulphate is an important PM2.5 source on a regional scale, with comparable values in all three sites (~3.5 μg·m−3). On average, the contribution of the "natural" components (e.g., mineral dust and marine aerosols) to PM2.5 is moderate (~1 μg·m−3) except during Saharan dust intrusions where this contribution is higher (detected simultaneously in all three sites). High-time resolution data confirmed and reinforced these results

Chelators confined into 80pvac-borax highly viscous dispersions for the removal of gypsum degradation layers

AbstractIn this paper a new method for the removal of gypsum degradation layers from carbonatic matrices in cultural heritage conservation, using aqueous Highly Viscous Polymeric Dispersions (HVPDs) based on partially hydrolyzed poly(vinyl acetate) and borax, embedded with chelators, is presented. Due to their interesting viscoelasticity, these systems guarantee a good adhesion to the treated surface and easiness of removal in one step, minimizing the residues. Thus, they can potentially overcome the "residue question" limit associated to traditional methodologies that use thickened solutions of chelators. Here the rheological properties of HVPDs containing different amounts of selected chelating agents are explored and their efficacy in the extraction of gypsum is verified through cleaning tests onto artificially sulfated travertine tiles. The homogeneous removal of gypsum across the surface was checked non-invasively via Fourier Transform Infrared Spectroscopy (FTIR) 2D Imaging. An analytical protocol for the pre-treatment and the analysis of HVPD samples by means of Ion Cromatography (IC) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) was set up and the approximate amount of calcium sulfate removed was determined

Atmospheric deposition of organic matter at a remote site in the central Mediterranean Sea: implications for the marine ecosystem

Abstract. Atmospheric fluxes of dissolved organic matter (DOM) were studied for the first time on the island of Lampedusa, a remote site in the central Mediterranean Sea (Med Sea), between 19 March 2015 and 1 April 2017. The main goals of this study were to quantify total atmospheric deposition of DOM in this area and to evaluate the impact of Saharan dust deposition on DOM dynamics in the surface waters of the Mediterranean Sea. Our data show high variability in DOM deposition rates without a clear seasonality and a dissolved organic carbon (DOC) input from the atmosphere of 120.7 mmol DOC m−2 yr−1. Over the entire time series, the average dissolved organic phosphorus (DOP) and dissolved organic nitrogen (DON) contributions to the total dissolved pools were 40 % and 26 %, respectively. The data on atmospheric elemental ratios also show that each deposition event is characterized by a specific elemental ratio, suggesting a high variability in DOM composition and the presence of multiple sources. This study indicates that the organic substances transported by Saharan dust on Lampedusa mainly come from a natural sea spray and that Saharan dust can be an important carrier of organic substances even though the load of DOC associated with dust is highly variable. Our estimates suggest that atmospheric input has a larger impact on the Med Sea than on the global ocean. Further, DOC fluxes from the atmosphere to the Med Sea can be up to 6 times larger than total river input. Longer time series combined with modeling would greatly improve our understanding of the response of DOM dynamics in the Med Sea to the change in aerosol deposition pattern due to the effect of climate change

Chemical and isotopic snow variability along the 1998 ITASE traverse from Terra Nova Bay to Dome C, East Antarctica

AbstractIn the framework of the PNRA–ITASE (Programma Nazionale di Ricerche in Antartide–International Trans-Antarctic Scientific Expedition) project, during the field season 1998/99, surface snow (1m cores and pits) and shallow firn cores (10–50m) were collected along a traverse from Terra Nova Bay (northern Victoria Land) to Dome C (East Antarctic ice sheet). Results of chemical, tritium and stable-isotope composition are presented here for the 1 m cores, some snow pits and the first 2 mof some shallow firn cores. the δ18O values show a regular trend with altitude, and the regression line between δ18O and surface temperature is δ18O = 0.99T (˚C) – 0.67. Primary aerosol components such as Na+, Cl–, Ca2+,Mg2+ and K+ show high concentrations decreasing with increasing altitude in the first 250–350km from the coast. At greater distances, concentrations of these species remain more constant. NO3– concentration shows an irregular profile with a progressive decreasing trend as altitude increases. Non-sea-salt (nss) SO42– concentration decreases up to about 250 km from the coast, increases 250–770 km from the coast and remains relatively constant in the most remote stations. Methanesulphonate (MSA) concentration shows high variability. the MSA/nssSO42– ratio exhibits a decreasing trend 250–550km from the coast. With increasing distance, the ratio shows moderate oscillations. nssCl– concentration shows a progressive increase as distance from the coast increases, in agreement with the increasing influence of HCl on the Cl– budget of the inland Antarctic atmosphere. Post-depositional re-emissions of Cl– and NO3– were found at stations characterized at the surface by long-term accumulation hiatus (wind crusts). the chemical-species distribution is consistent with the presence in the studied area of local and long-range transport processes, post-depositional effects and snow-accumulation variations observed along the traverse