Comparing Soil Nitrous Oxide and Methane Fluxes From Oil Palm Plantations and Adjacent Riparian Forests in Malaysian Borneo

Riparian forests are often kept as buffers between rivers and oil palm plantations. Many benefits of riparian forests, such as increasing biodiversity and providing a travel corridor for wildlife have been documented. Conversely, data on fluxes of the greenhouse gases nitrous oxide (N2O) and methane (CH4) from riparian forests are sparse. Nitrogen (N) from fertilizer applied in the oil palm plantations leached to the adjacent riparian forests, may increase emissions of N2O. Methane (CH4) fluxes might also differ between oil palm plantations and riparian forests due to carbon (C) availability. In this scoping study, we installed transects from three mature oil palm plantations to adjacent riparian forests within the SAFE project landscape in Sabah, Malaysia (https://www.safeproject.net) for measurements of greenhouse gases and associated parameters every 2 months for 13 months. Emissions of N2O were higher from riparian forests with 40.4 [95% confidence intervals (CI): 35.7–44.6] μg N2O-N m–2 h–1 than from an equivalent area of oil palm plantation 27.6 (CI: 23.1–32.3) μg N2O-N m–2 h–1. Methane uptake was significantly higher from the riparian forest with −14.7 (CI: −21.1 to −8.3) μg CH4-C m–2 h–1 compared to slight positive emission in the oil palm plantations of 6.3 (CI: 1.1–11.4) μg CH4-C m–2 h–1. We are contributing urgently needed flux data for less well studied riparian forests in the Tropics, however, additional long-term studies are needed to be able to draw wider conclusions than possible from this scoping study alone.

Modeling acidizing of carbonate formations with different reservoir properties

Introduction. The efficiency of matrix acidizing of the bottom-hole formation zone depends on many factors, the chief being the reservoir properties. The research aim is to assess the effect produced by the formation reservoir properties on the result of hydrochloric acid treatment. Experiments simulating carbonate formation acid treatment were carried out. Methods. The experiments were carried out using the UIK-1 core analysis apparatus. Carbonate cores with different porosity and permeability were selected. Some of the experiments modeled permeability reduction as a result of bottom-hole formation zone contamination with drilling mud. Results. The research has shown that during low permeability reservoirs acidizing, permeability increases to a greater extent than during high permeability cores acidizing. In low permeability cores, the acid solution mainly forms new channels, while in high permeability cores the expansion of existing ones mainly occurs. In the present paper, the equivalent surface area of the acid-formed channels was estimated. When acidizing low permeability cores, the equivalent area of the channels is larger than when acidizing high permeability cores. The outcome of acidizing of the core samples with impaired porosity and permeability and contaminated with model drilling mud is comparable to acidizing of low permeability samples not contaminated with drilling mud. Conclusions. Acidizing of low permeability reservoirs leads to a greater increase in permeability. The equivalent area of acid-formed channels is larger than that of high permeability cores treatment. This reveals that the impact of acid on low permeability reservoirs is more effective.

A series of equivalent area circle yield criteria based on unified strength theory

Unified strength theory considering the influence of the intermediate principal stress is widely used in geotechnical engineering, but the singularities bring inconvenience to the numerical calculation. A series of equivalent area circle yield criteria based on unified strength theory are derived. The parameters of the new yield criteria and Drucker-Prager criteria are discussed, and the flow vector coefficients of the new yield criteria are given. The new series of yield criteria are very convenient for numerical calculation and can be served as reference for the evaluation of the effects of strength theory.

Performance Comparison of High Strength Reinforced Concrete Circular and Square Columns Subjected to Flexural Controlled Cyclic Loading

In existing design practices selection of circular or square column shape mostly depends upon architectural needs rather than structural behavior. The behavior of equivalent area (circular and square), high strength reinforced concrete columns is reported to be same under monotonic loading conditions but their behavior under fatigue loading is not well-established. This paper presents the comparison of high strength reinforced concrete circular and square equivalent area columns’ performance (load-deflection behavior) under fatigue loading. Columns were casted in four configurations: square and circular shapes and with and without shear stirrups. Experimental results showed that in case of columns without shear stirrups, the square column resisted 38% more loading cycles as compared to circular column while the maximum deflection was 78% more than the circular column. Similarly, in case of columns with shear stirrups, square shaped column resisted 55% more loading cycles with only 5% more maximum deflections as compared to circular column. The results show that the square columns might be considered more ductile as compared to circular columns under the application of cyclic loading conditions like wind forces or seismic forces. Therefore, it might be concluded that square columns should be recommended for highly seismic regions as compared to circular columns with equivalent area. Doi: 10.28991/cej-2021-03091639 Full Text: PDF

The Effect of Glue Cohesive Stiffness on the Elastic Performance of Bent Wood–CFRP Beams

This paper presents experimental, theoretical and numerical studies of wood-CFRP beams bonded with polyurethane (PUR) adhesive. The analyses include two types of CFRP (carbon fibre-reinforced polymer) strengthening configurations and pure glue laminated timber beams as a reference. Through detailed analyses of a double-lap connection on blocks with and without CFRP strips, the authors state that neglecting the cohesive stiffness of adhesive layers may lead to an overestimation of an overall beam’s stiffness. This is significant with wood–CFRP connections, which showed values two times lower than with wood–wood connections. Theoretical modelling of the equivalent area used in a theory of composites provided much stiffer behaviour of the beams than in laboratory experiments. It proves that a PUR glue eliminates the possibility of using simple models that assume a perfect connection between bonded parts. These conclusions led the authors to use the finite element method (FEM) to take into account the cohesive stiffness. The FEM, based on the properties obtained from a double-lap joint analysis, allowed for the precise prediction of the elastic stiffness of the beams.

Green Manure Intercropped with Okra for Spontaneous Plant Suppression

Spontaneous plants are biological factors that compromise the yield of vegetables. The hypothesis is that green manure intercropped with okra suppress spontaneous plants and increase the production of this vegetable. The research aimed to evaluate the viability of green manure intercropped with okra to suppress spontaneous plants and increase vegetable productivity. The design was in randomized blocks with four replications and 10 treatments: cowpea [Vigna unguiculata (L). Walp.], sunn hemp (Crotalaria juncea L.), velvet bean [Mucuna nivea (L.) DC.] and dwarf pigeon pea [Cajanus cajan (L.) Huth] intercropping and monoculture with two controls without green manure. The green manure reduced the dry mass of spontaneous plants but did not increase the production of okra. The average values of the equivalent area index (EAI) in all intercropping were higher than one. Green manure is efficient in suppressing spontaneous plants, but to increase the productivity of the okra, adjustments must be made in the green manure-okra intercropping.

The influence of minisett size and time of planting on the yield of seed yam (Dioscorea Rotundata)

In traditional yam (Dioscorea spp.) production systems in West Africa, finding sole seed yam producers is rare and up to 30% of harvested tubers from the ware tuber crop is reserved to plant an equivalent area of the harvested crop during the next season. Many farmers typically must make a trade-off between food and seed in the use of available tubers. A study was carried out using a factorial experiment in a randomised complete block design to investigate the influence of planting different minisett sizes at different planting periods on the yield of seed yam with the aim of improving the availability of this expensive input and saving more ware tubers for food or sale. Results showed that by doubling or tripling the minisett size from 30 to 60 or 90 g, yields of seed yam increased by 61.1 and 103.3%, respectively. The 90 g minisetts had the highest values for all traits studied but had the least sett multiplication ratio. The early planted crop yielded 137% more than the late-planted crop. Significant interactions between minisett size, planting period and season were found. In 2016, although the highest yield of seed tubers was from early planted 90 g minisetts (35.6 t ha−1), the yield of early planted 30 g minisetts (23.8 t ha−1) was similar to those of 60 g planted mid-season (28.7 t ha−1) and 90 g planted late (20.0 t ha−1). To produce a high proportion of seed size tubers with less planting material, early planting of 30 g minisetts is recommended. Such practice will enhance seed tuber availability and food security by saving 1–2 t ha−1 of tubers that would have been used as seed instead of food.

Nature and origin of gas trapped in sediments in the Tagus River ebb-delta, off Lisbon, Portugal, the TAGUSGAS project

<p>The Tagus River ebb-delta is located near an important city center off Lisbon, Portugal. The Tagus delta hosts various kilometer scale landslides, the most important of which has been mapped and described with a presumable age of ~11 ky and 10 km in length, 4 km wide and 20 m of maximum thickness. An equivalent area of gas trapped in the sediments has also been reported (Terrinha et al., 2019).</p><p>The TAGUSGAS project aims at characterizing the nature and source of the gas. A multibeam and backscatter survey was carried out recently covering an area of 44 km<sup>2</sup>. Several morphologic artifacts were found. The magnetic survey carried out simultaneously allows at discriminating the anthropogenic origin of some of these artifacts. It also allows at distinguishing gas and igneous rock sources of acoustic blanking in the seismic reflection record.</p><p>The multibeam and backscatter basemap also serves as a tool to decide targets for seafloor sites for sample collection.</p><p>The authors would like to acknowledge the FCT financial support through project UIDB/50019/2020 – IDL and TAGUSGAS project (PTDC/CTA-GEO/31885/2017).</p>