Facilitating Sediment Budget Construction for Land Management Applications

Sediment budgets describe the production, transport, deposition and export of sediment in a catchment, and thus provide information useful for planning soil conservation, restoration and monitoring programmes and for evaluating existing and future environmental impacts. Five examples from New Zealand illustrate a variety of sediment budgeting approaches and their use in achieving goals relevant to land-use planning and management. Appropriate sediment budgeting strategies can be selected for a particular application only through careful consideration of the kinds of decisions that will follow from budgeting results. Sediment budget projects can be designed to incorporate the close co-operation between technical experts and clients that results in the most useful sediment budgets.

Using nutrient balance to estimate net C balance in landslide-prone pastoral hill country: testing the ‘‘dynamic equilibrium’’ hypothesis in New Zealand soft rock landscapes

Abstract: Given recent negotiations of the Committee of Parties to the United Nations Framework Convention on Climate Change, soil C accumulation related to soil conservation efforts may be counted as C credits in national C balance calculations under the Kyoto Protocol. It has been proposed that in some instances, erosion can establish a dynamic equilibrium that results in a C sink corresponding to ongoing recovery of C in eroded soils combined with ongoing C accumulation in terrestrial sediments. Given this hypothesis, full accounting for erosion and soil conservation in the C budgets of dynamic landscapes may represent a significant challenge due to indirect effects of burial and nutrient dynamics on the balance of plant production and decomposition of soil organic matter (SOM). As a method for evaluating the 'dynamic equilibrium' hypothesis, we examine the burial and availability of eroded C and nutrients using a combination of field data and models. Landslides represent a model system for studying erosional effects on C and N dynamics because they offer the ability to study easily identifiable events representing a known proportion of the landscape. We therefore investigate the C and N balance of pastoral land on soft-rock landscapes in New Zealand that commonly undergo shallow landslides. Soil cores driven to the bedrock interface indicate that 23-and 37-year-old landslides have recovered to -50% and 72% soil C stock, respectively, when compared with cores from uneroded sites on similar slopes and aspects. Locally, this upland soil loss represents the removal of 36 Mg/ha-90 Mg/ha. However, a portion of the eroded C may be retained on land if landslide debris is not fully evacuated by streams, and the eroded C can also become buried in marine environments. To determine whether the net effect of erosion can represent a sink for atmospheric CO 2 , we will combine the rate of upland soil C recovery with representations of the proportion of eroded C sequestered in sediments

Revisiting the Side Crushing Test Using the Three-Point Bending Test for the Strength Measurement of Catalyst Supports

International audienceNEXTLAB 2014-Advances in Innovative Experimental Methodology or Simulation Tools used to Create, Test, Control and Analyse Systems, Materials and Molecules NEXTLAB 2014-Innover dans le domaine de la méthodologie expérimentale et des outils de simulation pour créer, tester, contrôler et analyser des systèmes, matériaux et molécules Abstract — The side crushing test is commonly used to characterize the mechanical strength of catalyst supports. However its interpretation is complex for cylindrical supports due to their irregular geometry and the various fracture modes induced. A better analysis of the crushing test, altogether with a comparison of the results obtained with the three-Point Bending test (3PB) and an analysis of the defects present within the supports, provide a better interpretation of their crushing strength data. Experimental results show that two different fracture modes appear during the crushing test – one under bending configuration and one under crushing configuration – inducing a large scatter of the data. Moreover, a comparison with the 3PB test shows that the strength measured in crushing is lower and the scatter of the data is larger than the ones obtained in bending. This is a consequence of a Weibull size effect and of the presence of macro-defects within one type of the tested supports. It is concluded that an analysis of the fracture modes activated during crushing has to be carried out to obtain a correct distribution of the strength data. The presence of macro-defects within the micro-structure of the supports decreases drastically the crushing strength, while their influence on the bending strength is more limited. Re´ume´est d' e´rasement grain a` grain revisiteá l'aide du test de flexion trois points pour la me-sure de la re´istance des supports de catalyseurs — Le test d' e´rasement grain a` grain est couramment utilise´our caracte´iser la re´istance me´anique des supports de catalyseurs. Cependant, son interpre´ation est complexe pour les supports cylindriques du fait de leur geóme´rie irre´uliè re et des diffe´ents modes de rupture qu'elle induit. Une analyse de´ailleé du test d' e´rasement , ainsi qu'une comparaison avec les re´ultats obtenus par le test de flexion trois points et une analyse des de´auts pre´ents au sein des supports, permettent d' interpre´er plus pre´ise´ent les donneés de re´istance a` l' e´rasement obtenues. Les re´ultats expe´imentaux montrent la coexistence de deux diffe´ents modes de rupture lors du test d' e´rasement – un premier apparaissant sous configuration de flexion et un second apparaissant sous configuration de compression diame´rale – menant a` une large dispersion des valeurs. De plus, la comparaison avec le test de flexion trois points montre, d'une part, que la re´istance mesureé en e´rasement est plus faible et, d'autre part, que la dispersion des donneés est plus grande que celles obtenues en flexion. Ces caracte´istiques re´ultent d'un effet de taille ainsi que de la pre´ence de macro-de´auts au sein d'un des types de supports teste´i