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The spike in carbon dioxide (CO2) observed after rewetting of dry soils, known as the 'Birch effect', can contribute substantially to total soil carbon (C) emissions, however, the exact mechanisms and timings underlying this sudden CO2 release remain unclear. The amount of applied water and duration of the previous dry period are considered the main factors affecting the magnitude of the CO2 peak, but the preceding change in soil wettability, triggered by low soil water content, could also be an important contributor.We investigated the effect of soil water repellency (SWR, assessed by water drop penetration time test) on the short-term release of CO2 upon wetting of dry soils with different water quantities. The experiments were conducted under laboratory conditions using homogeneous and autoclaved soil from two locations in South Wales (UK) in both wettable and extremely water-repellent states. The CO2 efflux was measured using chambers above and below the samples. Upon wetting, CO2 efflux was up to 10 times lower in water-repellent soils as a result of rapid percolation through preferential pathways, with only a small amount of water (up to 10%) retained in the soil. Total CO2 efflux was proportional to the water retained in the soil after infiltration, suggesting that the release of CO2 occurred only from limited pore-spaces of the soil. The quick CO2 release suggests that chemical or biochemical processes, rather than microbial respiration, is the main source of CO2 efflux in this study. Part of the CO2 released was transported to the bottom chamber, which under natural conditions could enhance the entrapment of gas in the subsoil. This study shows that alterations in 2 the water-filled pore-space as a result of SWR significantly reduced the CO2 efflux upon wetting and suggests that SWR could be a key factor when investigating and predicting C fluxes.

The experimental vaporÀliquid equilibrium (VLE) data for two ternary systems containing CO 2 + n-alkane + n-decane were measured using an online staticÀanalytic apparatus with a movable ROLSI sampler. The studied CO 2 + n-hexane + n-decane and CO 2 + n-octane + n-decane systems were measured at temperatures of (312.89, 342.50, and 376.20) K and (313.59, 344.28, and 373.49) K, respectively. The PengÀRobinson equation of state was used to predict the VLE data of the ternary systems from the temperatureÀindependent interaction parameters of the binary systems.

In 1997, a new thermodynamic laboratory was create from scratch. Throughout 20 years of work, this laboratory has performed and reported experimental determinations of thermophysical properties, such as phase equilibria (VLE, SLE, SLVE), critical points of pure fluids and mixtures, volumetric properties (PvT), dynamic viscosities, supercritical fluid extraction (SFE), and studies on the formation of gas hydrates. Over time, experimental systems have been designed, developed, and/or modified according to the experiments. Besides, molecular simulations have been carried out, resulting in the proposal of equations of state based on perturbation theory. All of the measurements that have been carried out have reported the experimental uncertainty according to the NIST technical note 1297. In this work, experimental determinations of each thermophysical property, VLE, solid solubility in supercritical fluids, PvT, dynamic viscosities, and gas hydrate dissociation data, are reported in the 293.15–353.15 K temperature range and at pressures up to 30 MPa. The experimental uncertainty of reported data was determined and is mentioned for each property.

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<p>Since withdrawal from the European Union a series of reforms of agricultural policy are under development in the United Kingdom. There is currently no dedicated soil policy in Wales and the reforms provide an opportunity to devise a new position on soils that sets an ambition for the sustainable use of soils for future generations. To maximise soil policy adoption, we learnt from previous unsuccessful attempts to launch soil policies and developed a completely different approach to co-designing soil policy. We reflect on our experiences as researchers working in placements directly within government policy teams as a mechanism for soil policy development. This involved several different aspects of policy development and a wide range of actors. Key activities included an independent evidence review to ensure current scientific knowledge provided the foundation for the draft soil policy statement. The embedded nature of the researchers within the policy teams meant effective and fluid dialogue, building trusted relationships and the opportunity to challenge the potential bias within the policy teams regarding key evidence. Building consensus towards a draft soil policy statement was a major barrier to overcome. We used the concept of co-design with the policy team and other stakeholders (other policy teams, regulatory bodies, non-governmental organisations, and farmers) to further the development of the draft soil policy statement and to select key objectives for sustainable soil management relevant to Wales. The main outcomes from the placements were: understanding the policy context and mechanisms for policy development; presenting clear and concise evidence; managing complex relationships and challenging institutional structures.</p>