Suggested protocol for collecting, handling and preparing peat cores and peat samples for physical, chemical, mineralogical and isotopic analyses

For detailed reconstructions of atmospheric metal deposition using peat cores from bogs, a comprehensive protocol for working with peat cores is proposed. The first step is to locate and determine suitable sampling sites in accordance with the principal goal of the study, the period of time of interest and the precision required. Using the state of the art procedures and field equipment, peat cores are collected in such a way as to provide high quality records for paleoenvironmental study. Pertinent field observations gathered during the fieldwork are recorded in a field report. Cores are kept frozen at -18 degree C until they can be prepared in the laboratory. Frozen peat cores are precisely cut into 1 cm slices using a stainless steel band saw with stainless steel blades. The outside edges of each slice are removed using a titanium knife to avoid any possible contamination which might have occurred during the sampling and handling stage. Each slice is split, with one-half kept frozen for future studies (archived), and the other half further subdivided for physical, chemical, and mineralogical analyses. Physical parameters such as ash and water contents, the bulk density and the degree of decomposition of the peat are determined using established methods. A subsample is dried overnight at 105 degree C in a drying oven and milled in a centrifugal mill with titanium sieve. Prior to any expensive and time consuming chemical procedures and analyses, the resulting powdered samples, after manual homogenisation, are measured for more than twenty-two major and trace elements using non-destructive X-Ray fluorescence (XRF) methods. This approach provides lots of valuable geochemical data which documents the natural geochemical processes which occur in the peat profiles and their possible effect on the trace metal profiles. The development, evaluation and use of peat cores from bogs as archives of high-resolution records of atmospheric deposition of mineral dust and trace elements have led to the development of many analytical procedures which now permit the measurement of a wide range of elements in peat samples such as lead and lead isotope ratios, mercury, arsenic, antimony, silver, molybdenum, thorium, uranium, rare earth elements. Radiometric methods (the carbon bomb pulse of (14)C, (210)Pb and conventional (14)C dating) are combined to allow reliable age-depth models to be reconstructed for each peat profile.     

Improved interpretation of in-diffusion measurements with confined swelling clays

Diffusion is considered the principal transport mechanism of radio-nuclides and other low-molecular-weight pollutants in compacted clays used as barriers at various disposal and storage sites, for example, at projected deep repositories for radioactive waste. Porous filters are routinely used to confine swelling clays in diffusion studies of radio-tracers. The presence of the filter gives rise to considerable mass-transfer limitations at the clay boundary that result in erroneous diffusion parameters. We have solved the problem of in-diffusion with due account for this phenomenon by means of Fourier transforms. By using literature data on the in-diffusion of traces of radioactive cesium in an argillaceous rock (Opalinus clay) and a compacted bentonite (FEBEX bentonite), we have demonstrated that taking into account the mass-transfer limitations considerably improves the quality of the theoretical fit of the time evolution of radio-tracer concentration in the reservoir. Besides that, we have shown that ignoring the mass-transfer limitations leads to a noticeable underestimation of both the effective diffusion coefficient and the specific sorption capacity of the clay.     

Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths

Binary oxide systems (CuCr₂O₄, CuCo₂O₄), deposited onto cordierite monoliths of honeycomb structure with a second support (finely dispersed Al₂O₃), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine's gas exhausts (O₂, NO_x, H₂O, CO₂) and O³ as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO₂. Oxidants used can be arranged with reference to decreasing their activity in a following series: O₃ >> NO₂ > H₂O > NO > O₂ > CO₂. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O₃ occurs intensively (in the presence of copper chromite based catalyst) even at closing to ambient temperatures. Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem.     

Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths

Binary oxide systems(Cu Cr2O4, Cu Co2O4), deposited onto cordierite monoliths of honeycomb structure with a second support(finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine’s gas exhausts(O2, NOx, H2 O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3 NO2> H2 O > NO > O2> CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively(in the presence of copper chromite based catalyst) even at closing to ambient temperatures.Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem.     

Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths

Binary oxide systems (CuCr₂O₄, CuCo₂O₄), deposited onto cordierite monoliths of honeycomb structure with a second support (finely dispersed Al₂O₃), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine's gas exhausts (O₂, NO_x, H₂O, CO₂) and O₃ as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO₂. Oxidants used can be arranged with reference to decreasing their activity in a following series: O₃ ? NO₂ > H₂O > NO > O₂ > CO₂. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O₃ occurs intensively (in the presence of copper chromite based catalyst) even at closing to ambient temperatures. Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the “cold start” problem.     

Identifying the sources and timing of ancient and medieval atmospheric lead pollution in England using a peat profile from Lindow bog, Manchester

A peat core from Lindow bog near Manchester, England, was precisely cut into 2 cm slices to provide a high-resolution reconstruction of atmospheric Pb deposition. Radiocarbon and (210)Pb age dates show that the peat core represents the period ca. 2000 BC to AD 1800. Eleven radiocarbon age dates of bulk peat samples reveal a linear age-depth relationship with an average temporal resolution of 18.5 years per cm, or 37 years per sample. Using the Pb/Ti ratio to calculate the rates of anthropogenic, atmospheric Pb deposition, the profile reveals Pb contamination first appearing in peat samples dating from ca. 900 BC which clearly pre-date Roman mining activities. Using TIMS, MC-ICP-MS, and SF-ICP-MS to measure the isotopic composition of Pb, the (208)Pb/(206)Pb and (206)Pb/(207)Pb data indicate that English ores were the predominant sources during the pre-Roman, Roman, and Medieval Periods. The study shows that detailed studies of peat profiles from ombrotrophic bogs, using appropriate preparatory and analytical methods, can provide new insight into the timing, intensity, and predominant sources of atmospheric Pb contamination, even in samples dating from ancient times.