An X-ray photoelectron spectroscopy investigation of chromium conversion coatings and chromium compounds

Hexavalent and trivalent chromium based conversion coatings on zinc electrodeposited steel have been investigated using X-ray photoelectron spectroscopy (XPS) with the aim of elucidating their film chemistry. Furthermore, a monochromatic Al Kα X-ray source was utilised and the spectra produced evaluated using curve fitting software to elucidate oxidation state information. In addition, a number of chromium compounds were investigated and used to complement the curve fitting analysis for the conversion coatings. High resolution Cr2p spectra from chromium compounds exhibited multiplet splitting for Cr2O3. Additional satellite emissions can also be observed for Cr2O3 and Cr(OH)3. Curve fitting of hexavalent chromium conversion coating (CCC) 2p3/2 spectra contained both Cr(VI) and Cr(III) species with the content of the former slightly higher when the X-ray beam take-off angle (TOA) was reduced to determine more surface specific information. The Cr(III) content was determined to be mainly composed of Cr(OH)3 with some Cr2O3. In comparison, trivalent CCCs were largely composed of Cr2O3 as opposed to Cr(OH)3. Survey scans of both coatings revealed that the trivalent CCCs had a higher relative zinc content

Methods for the quantification of GHG emissions at the landscape level for developing countries in smallholder contexts

Landscape scale quantification enables farmers to pool resources and expertise. However, the problem remains of how to quantify these gains. This article considers current greenhouse gas (GHG) quantification methods that can be used in a landscape scale analysis in terms of relevance to areas dominated by smallholders in developing countries. In landscape scale carbon accounting frameworks, measurements are an essential element. Sampling strategies need careful design to account for all pools/fluxes and to ensure judicious use of resources. Models can be used to scale-up measurements and fill data gaps. In recent years a number of accessible models and calculators have been developed which can be used at the landscape scale in developing country areas. Some are based on the Intergovernmental Panel on Climate Change (IPCC) method and others on dynamic ecosystem models. They have been developed for a range of different purposes and therefore vary in terms of accuracy and usability. Landscape scale assessments of GHGs require a combination of ground sampling, use of data from census, remote sensing (RS) or other sources and modelling. Fitting of all of these aspects together needs to be performed carefully to minimize uncertainties and maximize the use of scarce resources. This is especially true in heterogeneous landscapes dominated by smallholders in developing countries