Copper deposition on TiO2 from copper(II)hexafluoroacetylacetonate

The authors have studied the adsorption of CuII(hfac)2 on the surface of a model oxide system, TiO2(110), and probed the molecular stability with respect to thermal cycling, using atomic scale imaging by scanning tunneling microscopy supported by x-ray photoemission spectroscopy. They find that at 473 K, the adsorbed metal-organic molecules begin to dissociate and release Cu atoms which aggregate and form Cu nanoparticles. These Cu nanoparticles ripen over time and the size (height) distribution develops into a bimodal distribution. Unlike other organometallic systems, which show a bimodal distribution due to enhanced nucleation or growth at surface step edges, the nanoparticles do not preferentially form at steps. The reduced mobility of the Cu islands may be related to the co-adsorbed ligands that remain in very small clusters on the surface.

Optimization of electroless copper plating on polyethylene films modified by surface grafting of vinyl ether of monoethanolamine

Metallized plastics have recently received significant interest for their useful applications in electronic devices such as for integrated circuits, packaging, printed circuits and sensor applications. In this work the metallized films were developed by electroless copper plating of polyethylene films grafted with vinyl ether of monoethanoleamine. There are several techniques for metal deposition on surface of polymers such as evaporation, sputtering, electroless plating and electrolysis. In this work the metallized films were developed by electroless copper plating of polyethylene films grafted with vinyl ether of monoethanoleamine. Polyethylene films were subjected to gamma-radiation induced surface graft copolymerization with vinyl ether of monoethanolamine. Electroless copper plating was carried out effectively on the modified films. The catalytic processes for the electroless copper plating in the presence and the absence of SnCl2 sensitization were studied and the optimum activation conditions that give the highest plating rate were determined. The effect of grafting degree on the plating rate is studied. Electroless plating conditions (bath additives, pH and temperature) were optimized. Plating rate was determined gravimetrically and spectrophotometrically at different grafting degrees. The results reveal that plating rate is a function of degree of grafting and increases with increasing grafted vinyl ether of monoethanolamine onto polyethylene. It was found that pH 13 of electroless bath and plating temperature 40°C are the optimal conditions for the plating process. The increasing of grafting degree results in faster plating rate at the same pH and temperature. The surface morphology of the metallized films was investigated using scanning electron microscopy (SEM). The adhesion strength between the metallized layer and grafted polymer was studied using tensile machine. SEM photos and adhesion measurements clarified that uniform and adhered deposits were obtained under optimum conditions.

Croig Cave: a late Bronze Age ornament deposition and 3,500 years of coastal foraging in NW Mull, Scotland

Activity within caves provides an important element of the later prehistoric and historic settlement pattern of western Scotland. This contribution reports on a small-scale excavation within Croig Cave, on the coast of north-west Mull, that exposed a 1.95m sequence of midden deposits and cave floors that dated bewteen c 1700 BC and AD 1400. Midden analysis indicated the processing of a .... 950 BC, a penannular copper bracelet a discrete ritual episode within the cycle of otherwise potentially mundane activities. Lead isotope analysis indicates an Irish origin for the copper ore. A piece of iron slag within later midden deposits, dated to c 400 BC, along with high frequencies of wood charcoal, suggest that smithing or smelting may have occurred within the cave. High zinc levels in the historic levels of the midden c AD 1200 might indicate intensive processing of seaweed.

Seasonal variations of the physical and optical characteristics of Saharan Dust: results from the Dust outflow and Deposition to the Ocean (DODO) experiment

North African dust is important for climate through its direct radiative effect on solar and terrestrial radiation and its role in the biogeochemical system. The Dust Outflow and Deposition to the Ocean project (DODO) aimed to characterize the physical and optical properties of airborne North African dust in two seasons and to use these observations to constrain model simulations, with the ultimate aim of being able to quantify the deposition of iron to the North Atlantic Ocean. The in situ properties of dust from airborne campaigns measured during February and August 2006, based at Dakar, Senegal, are presented here. Average values of the single scattering albedo (0.99, 0.98), mass specific extinction (0.85 m^2 g^-1 , 1.14 m^2 g^-1 ), asymmetry parameter (0.68, 0.68), and refractive index (1.53--0.0005i,1.53--0.0014i) for the accumulation mode were found to differ by varying degrees between the dry and wet season, respectively. It is hypothesized that these differences are due to different source regions and transport processes which also differ between the DODO campaigns. Elemental ratios of Ca/Al were found to differ between the dry and wet season (1.1 and 0.5, respectively). Differences in vertical profiles are found between seasons and between land and ocean locations and reflect the different dynamics of the seasons. Using measurements of the coarse mode size distribution and illustrative Mie calculations, the optical properties are found to be very sensitive to the presence and amount of coarse mode of mineral dust, and the importance of accurate measurements of the coarse mode of dust is highlighted.

Adsorption, orientation and thermal decomposition of copper(II) hexafluoroacetylacetonate on rutile TiO2(110)

We have investigated the adsorption and thermal decomposition of copper hexafluoroacetylacetonate (Cu-11(hfaC)(2)) on single crystal rutile TiO2(110). Low energy electron diffraction shows that room temperature saturation coverage of the Cu-II(hfac)(2) adsorbate forms an ordered (2 x 1) over-layer. X-ray and ultra-violet photoemission spectroscopy of the saturated surface were recorded as the sample was annealed in a sequential manner to reveal decomposition pathways. The results show that the molecule dissociatively adsorbs by detachment of one of the two ligands to form hfac and Cu-1(hfac) which chemisorb to the substrate at 298 K. These ligands only begin to decompose once the surface temperature exceeds 473 K where Cu core level shifts indicate metallisation. This reduction from Cu(I) to Cu(0) takes place in the absence of an external reducing agent and without disproportionation and is accompanied by the onset of decomposition of the hfac ligands. Finally, C K-edge near edge X-ray absorption fine structure experiments indicate that both the ligands adsorb aligned in the < 001 > direction and we propose a model in which the hfac ligands adsorb on the 5-fold coordinated Ti atoms and the Cu-1(hfac) moiety attaches to the bridging O atoms in a square planar geometry. The calculated tilt angle for these combined geometries is approximately 10 degrees to the surface normal.

Seasonality of modern pollen and sediment deposition in an estuarine context: the Severn Estuary Levels, southwest England

Recent sedimentological and palynological research on subfossil Holocene banded sediments from the Severn Estuary Levels suggested seasonality of deposition, registered by variations in mineral grain-size and pollen assemblages between different parts of the bands. Here we provide data that strengthen this interpretation from sampling of modern sediments and pollen deposition on an active mudflat and saltmarsh on the margin of the Severn Estuary, and comparison with a vegetation survey and contemporary records of climate, river and tidal regimes. The results of grain-size analysis indicate deposition of comparatively coarse-grained silts during the relatively cool and windy conditions of winter and comparatively fine-grained sediments during relatively warm and calm summer months. Pollen analysis demonstrates the significance of long-term storage of pollen grains and fern spores in the estuarine waterbody, superimposed on which seasonal variations in pollen inputs from local and regional vegetation remain detectable. Copyright (C) 2007 John Wiley & Sons, Ltd.

Effect of time and mode of depuration on tissue copper concentrations of the earthworms Eisenia andrei, Lumbricus rubellus and Lumbricus terrestris

Eisenia andrei, Lumbricus rubellus and Lumbricus terrestris were exposed to 250, 250 and 350 mg kg(-1) Cu respectively in Cu(NO3)(2(aq)) amended soil for 28 d. Earthworms were then depurated for 24 to 72 h, digested and analysed for Cu and Ti or, subsequent to depuration were dissected to remove any remaining soil particles from the alimentary canal and then digested and analysed. This latter treatment proved impossible for E. andrei due to its small size. Regardless of depuration time, soil particles were retained in the alimentary canal of L. rubellus and L. terrestris. Tissue concentration determinations indicate that E. andrei should be depurated for 24 h, L. rubellus for 48 h and L. terrestris should be dissected. Ti was bioaccumulated and therefore could not be used as an inert tracer to determine mass of retained soil. Calculations indicate that after 28 d earthworms were still absorbing Cu from soil. (C) 2006 Elsevier Ltd. All rights reserved.

The influence of mineral solubility and soil solution concentration on the toxicity of copper to Eisenia fetida Savigny

The OECD 14 d earthworm acute toxicity test was used to determine the toxicity of copper added as copper nitrate (Cu(NO3)(2)), copper sulphate (CuSO4) and malachite (Cu-2(OH)(2)(CO3)) to Eisenia fetida Savigny. Cu(NO3)(2), and CuSO4 were applied in both an aqueous (aq) and solid (s) form, Cu-2(OH)(2)(CO3) was added as a solid. Soil solution was extracted by centrifugation, and analysed for copper. Two extractants [0.01 M CaCl2 and 0.005 M diethylenetriminpentaacetic acid (DTPA)] were used as a proxy of the bioavailable copper fraction in the soil. For bulk soil copper content the calculated copper toxicity decreased in the order nitrate > sulphide > carbonate, the same order as decreasing solubility of the metal compounds. For Cu(NO3)(2) and CuSO4, the LC50s obtained were not significantly different when the compound was added in solution or solid form. There was a significant correlation between the soil solution copper concentration and the percentage earthworm mortality for all 3 copper compounds (P less than or equal to 0.05) indicating that the soil pore water copper concentration is important for determining copper availability and toxicity to E. fetida. In soil avoidance tests the earthworms avoided the soils treated with Cu(NO3)(2) (aq and s) and CuSO4 (aq and s), at all concentrations used (110-8750 mug Cu g(-1), and 600-8750 mug Cu g(-1) respectively). In soils treated with Cu-2(OH2)CO3, avoidance behaviour was exhibited at all concentrations greater than or equal to3500 mug Cu g(-1). There was no significant correlation between the copper extracted by either CaCl2 or DTPA and percentage mortality. These two extractants are therefore not useful indicators of copper availability and toxicity to E. fetida.

A Cu tolerant population of the earthworm Dendrodrilus rubidus (Savigny, 1862) at Coniston Copper Mines, Cumbria, UK

Dendrodrilus rubidus were sampled from a mine spoil soil at Coniston Copper Mine, an abandoned Cu mine in Cumbria, UK and a Cu-free control site. Earthworms were maintained for 14 d in both Kettering loam and a Moorland soil amended with Cu nitrate. Mortality, condition index, weight change and tissue concentration were determined. In both soils D. rubidus native to the mine site were able to tolerate significantly higher soil Cu concentrations (MWRT, p <= 0.001), and exhibited significantly less change in weight (t-test, p <= 0.001) and a lower loss in condition (t-test, p <= 0.001) than control earthworms. For a given soil Cu concentration tissue Cu concentrations were greater in the mine site earthworms. Low cocoon production and viability from the mine site population prevented the determination of toxicity parameters on the F1 generation and may be an indicator of the cost of tolerance to the population. (c) 2007 Elsevier Ltd. All rights reserved.

Soil mobility of sewage sludge-derived dissolved organic matter, copper, nickel and zinc

A soil (sandy loam) column leaching study aimed to determine the extent of mobility and co-mobility of Cu, Ni, Zn and dissolved organic matter (DOM) released from a surface-application (equivalent to 50 t ds ha(-1)) of anaerobically-digested sewage sludge. Leaching of DOM through It the soil column was found to be almost un-retarded. Decidedly similar behaviour was exhibited by Ni suggesting that it migrated as organic complexes. Whilst Cu was also found to be leached, significant retardation was evident. However, the importance of DOM in promoting the mobility of both Cu and Ni was evidenced by their lack of mobility when added to the soil column as inorganic forms. The presence of DOM did not prevent Zn from becoming completely adsorbed by the soil solid phase. In relation to WHO drinking water guidelines, only Ni concentrations showed potential environmental significance. due to the relatively poor retention of Ni by the sludge solid phase. (C) 2003 Elsevier Ltd. All rights reserved.

Complexation of copper by sewage sludge-derived dissolved organic matter: Effects on soil sorption behaviour and plant uptake

The complexation of Cu by sewage sludge-derived dissolved organic matter (SSDOM) is a process by which the environmental significance of the element may become enhanced due to reduced soil sorption and, hence, increased mobility. The work described in this paper used an ion selective electrode procedure to show that SSDOM complexation of Cu was greatest at intermediate pH values because competition between hydrogen ions and Cu for SSDOM binding sites, and between hydroxyl ions and SSDOM as Cu ligands, was lowest at such values. Batch sorption experiments further showed that the process of Cu complexation by SSDOM provided an explanation for enhanced desorption of Cu from the solid phase of a contaminated, organic matter-rich, clay loam soil, and reduced adsorption of Cu onto the solid phase of a sandy loam soil. Complexation of Cu by SSDOM did not affect uptake of Cu by spring barley plants, when compared to free ionic Cu, in a sand-culture pot experiment. However, it did appear to lead to greater biomass yields of the plant; perhaps indicating that the Cu-SSDOM complex had a lower toxicity towards the plant than the free Cu ion.

Seasonal deposition of Holocene banded sediments in the Severn Estuary Levels (southwest Britain): palynological and sedimentological evidence

Banded sediments outcrop widely in the intertidal zone of the Severn Estuary and have been suggested, on the basis of textural analysis, to have formed in response to seasonal variations in sea temperature and windiness (Holocene, 14 (2004) 536). Here palynological and sedimentological analyses of banded sediments of mid-Holocene date from Gold Cliff, on the Welsh side of the Severn Estuary, are combined to test and further develop the hypothesis of seasonal deposition. Pollen percentage and concentration data are presented from a short sequence of bands to establish whether textural variations in the bands coincide with variations in pollen content reflecting seasonal flowering patterns. It is shown that fine-grained band parts contain higher total pollen concentrations, and a higher proportion of pollen from late spring- to summer-flowering plants, than coarse-grained band parts. Pollen in the coarser deposits appears primarily to reflect deposition from the buffering `reservoir' of suspended pollen in the estuarine water-body and from rivers, when there is little pollen in the air in winter, while the finer sediments contain pollen deposited from the atmosphere during the flowering season, superimposed on these `background' sources. The potential of such deposits for refining chronologies and identifying seasonality of coastal processes is noted, and the results of charcoal particle analysis of the bands presented as an example of how they have the potential to shed light on seasonal and annual patterns of human activity. (C) 2004 Elsevier Ltd. All rights reserved.

Modelling stream and soil water nitrate dynamics during experimentally increased nitrogen deposition in a coniferous forest catchment at Gardsjon, Sweden

Increased atmospheric deposition of inorganic nitrogen (N) may lead to increased leaching of nitrate (NO3-) to surface waters. The mechanisms responsible for, and controls on, this leaching are matters of debate. An experimental N addition has been conducted at Gardsjon, Sweden to determine the magnitude and identify the mechanisms of N leaching from forested catchments within the EU funded project NITREX. The ability of INCA-N, a simple process-based model of catchment N dynamics, to simulate catchment-scale inorganic N dynamics in soil and stream water during the course of the experimental addition is evaluated. Simulations were performed for 1990-2002. Experimental N addition began in 1991. INCA-N was able to successfully reproduce stream and soil water dynamics before and during the experiment. While INCA-N did not correctly simulate the lag between the start of N addition and NO 2 3 breakthrough, the model was able to simulate the state change resulting from increased N deposition. Sensitivity analysis showed that model behaviour was controlled primarily by parameters related to hydrology and vegetation dynamics and secondarily by in-soil processes.