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Abstract This conference report summarizes the current challenges of researching microplastics pollution in the ocean as debated by international experts and stakeholders at a workshop held in San Sebastian, Spain, 1–2 October 2019. The transdisciplinary, co-learning approach of this report stressed the need to incorporate multiple perspective in solving the problem of microplastics and resulted in three proposed actions: (i) filtering microplastics from waste waters; (ii) mandatory ecolabels on plastic products packages; and (iii) circular economy of packaging plastics.

A priority of the industrial applications of microalgae is the reduction of production costs while maximizing algae biomass productivity. The purpose of this study was to carry out a comprehensive evaluation of the effects of pH control on the production of Nannochloropsis gaditana in tubular photobioreactors under external conditions while considering the environmental, biological, and operational parameters of the process. Experiments were carried out in 3.0 m3 tubular photobioreactors under outdoor conditions. The pH values evaluated were 6.0, 7.0, 8.0, 9.0, and 10.0, which were controlled by injecting pure CO2 on-demand. The results have shown that the ideal pH for microalgal growth was 8.0, with higher values of biomass productivity (Pb) (0.16 g L-1 d-1), and CO2 use efficiency ([Formula: see text]) (74.6% w w-1); [Formula: see text]/biomass value obtained at this pH (2.42 [Formula: see text] gbiomass-1) was close to the theoretical value, indicating an adequate CO2 supply. At this pH, the system was more stable and required a lower number of CO2 injections than the other treatments. At pH 6.0, there was a decrease in the Pb and [Formula: see text]; cultures at pH 10.0 exhibited a lower Pb and photosynthetic efficiency as well. These results imply that controlling the pH at an optimum value allows higher CO2 conversions in biomass to be achieved and contributes to the reduction in costs of the microalgae production process.

The gas production behavior of methane hydrate in porous media using the huff and puff method was investigated in the Cubic Hydrate Simulator (CHS), a novel developed three-dimensional 5.8-L cubic pressure vessel. Three horizontal layers equally divide the CHS into four regions. A 9-spot distribution of the vertical wells, a single horizontal well and a 25-spot distribution of the thermometers are arranged on each layer, respectively. The vertical wells at the axis of the CHS were used as the injection and production wells. The huff and puff method includes the injection, soaking and production stages. The amount of water injected and produced, the gas production rate, the percentage of the hydrate dissociation and the gas-to-water ratio were evaluated. Under the thermodynamic conditions in this work, the gas production from the sediment in this work using the huff and puff method is economically profitable from the relative criterion point of view. The sensitivity analysis demonstrates the dependence of the gas production on the initial hydrate saturation, and the temperature and the injection rate of the injected hot water.

High-resolution stable isotope records obtained from Antarctic ice cores can be used as proxies to investigate past climatic changes in Antarctica, overcoming the spatiotemporal limitations of observational and instrumental records. Here, we used a new high-resolution ice core stable isotope record (1709–2001 AD) obtained from the Lambert Glacier Basin 69 (LGB69) site and a published stable isotope record (1757–1987 AD) from coastal Princess Elizabeth Land (PEL) to reconstruct temperature variability in the coastal region of PEL over the past three centuries. The dominant moisture source region for coastal PEL is mid-high latitudes of the South Indian Ocean (SIO) and this has remained stable over the past three centuries. Owing to non-climatic noise, no statistically significant isotope‒temperature relationship can be evidenced at annual-to-decadal scales. However, the ice core δD records do enable us to reconstruct multi-decadal temperature variability in the coastal region of PEL. The temperature reconstructions showed a consistent warming trend during the 20th century, whereas the cold periods prior to the 20th century may be related to the Little Ice Age (LIA). Our reconstructions exhibit high reliability, evidenced by their agreement with previous reconstructions from PEL. We also found that annual temperature variability is related to the Southern Annular Mode (SAM), whereas multi-decadal temperature variability is related to the Indian Ocean Dipole (IOD). However, the relationship between the SAM and temperature is unclear before the 1970s. The results of this study are helpful in understanding long-term temperature changes in Antarctica and provide an important reference for the attribution of temperature changes.

A cal. 20-year-resolution pollen record from Gonghai Lake presented the detailed process of mountain vegetation succession and East Asian Summer Monsoon (EASM) changes since the last deglaciation in Shanxi Province, North China. Modern vegetation distribution and lake surface pollen assemblages suggested that the fossil pollen mainly came from local and surrounding vegetation in Gonghai Lake, which reflected the elevational changes of plant communities in study area. From 14,700 to 11,100 cal. yr BP, open forests and mountain meadows dominated by shrubs and herbaceous species in surrounding area, suggesting a weak EASM with less precipitation. In the period between 11,100 and 7300 cal. yr BP, bushwoods and grasses were gradually replaced by mixed broadleaf-conifer forest, first developed by pioneer species of Betula and Populus and then replaced by Picea, Pinus, and Quercus, implying an enhanced EASM and increased temperature and precipitation. During the period of 7300–5000 cal. yr BP, warm-fitted trees became expanded and widespread, indicating a climax community of mixed broadleaf-conifer forest and warm and humid climate with higher temperature and sufficient precipitation and the strongest period of EASM. From 5000 to 1600 cal. yr BP, Pinus pollen increased, but Quercus pollen decreased, showing the breakup of the climax community and the recession of the EASM. Since 1600 cal. yr BP, under the threats of land reclamation and deforestation, forest cover sharply decreased, and mountain grass lands were developed. The EASM changes inferred from pollen record of Gonghai Lake were asynchronous to the oxygen isotope records of stalagmites from southern China. We suggest that the existence of remnant Northern Hemisphere ice sheets and relative low sea levels might hampered the northward penetration of the EASM in early Holocene, which caused the maximum monsoon precipitation to reach northern China until mid-Holocene.

Abstract Long term wave measurement is of vital importance for assessing the wave power resources, optimizing the productivity of wave energy devices, and determining the largest waves for the survivability of the wave energy device during its life time in sea. Among the technologies developed for measuring ocean waves, wave buoys may be one of the most popular used devices for long-term wave measurement. In order to investigate whether the wave characteristics can be accurately measured using the wave buoys, an experimental study was carried out on the performance of three wave buoy models, that is, Wavescan buoys and one ODAS buoy, in a wave tank using the European FP7-MARINET facilities. The wave measurements using the wave buoys are compared to the measured waves using the reference wave gauges in the tank so the accuracy of the wave measurements can be examined. This paper presents the analyzed results in both time and frequency domains and the comparison between the measurements by the wave buoys and wave gauges. The analysis results reveal that the wave buoys are reliable for measuring the scaled wave conditions, for both regular and irregular waves. Besides, the Wavescan buoys have better performances than the ODAS buoy in terms of accuracy and the correlation with the wave gauges.

Using rainbow wrasse as a model species, we evaluate the impact of protection on the relationship between body size and: i) trophic position (TP), based on δ15N; and ii) body condition (BC), based on weight-at-length. We found that the biomass of the rainbow wrasse, their predators and their competitors was higher inside the no-take marine protected area (NTA) than in the area open to fishing. The TP of rainbow wrasse was higher inside the NTA but the BC was lower. A domed relationship between TP and size was observed in both areas: the TP increased with size up to 12.6 cm total length, when all individuals shifted to terminal males, and then decreased. Although other confounding environmental variables may exist, the indirect effects of fishing on competition and predation risk are the most likely explanation for the changes in TP, BC and the ontogenetic dietary shift of the rainbow wrasse.

Gas production from hydrates induced by depressurization is a complex thermal-hydrodynamic-mechanical–chemical (THMC) coupled process. In this paper, we present a THMC coupled model to simulate the fluid flow in hydrate-bearing sediments (HBS) and the geomechanical behavior of HBS. The model is made of two subsystems, which are the fluid part of non-isothermal multi-phase flow with hydrate kinetic and solid part of geomechanical deformation. It accounts for two-way coupling effects between these two subsystems, i.e. the effect of pore pressure and hydrate dissociation on the solid mechanical behavior and the effect of stress on the hydraulic behavior. A new numerical method based on the hybrid control volume finite element method (CVFEM)-finite element method (FEM) is developed to solve the mathematical models. The local conservative CVFEM is used for the fluid part, and the standard FEM for the solid part. In the framework of hybrid CVFEM-FEM, the local conservation is reserved and the primary variables for the two subsystem are co-located. A multi-point flux approximation (MPFA) is adopted without orthogonal meshes so that it is very flexible to build complex geometrical models. The accuracy and reliability of the newly developed simulator QIMGHyd-THMC are tested by comparing with two experimental examples and a large-scale benchmark problem of other popular simulators.

Abstract Tight gas reservoirs always have a low natural gas recovery because of the poor reservoir properties. Effective means on achieving enhanced gas recovery (EGR) in this type of reservoir remain a challenging task. In this study, experimental investigations on supercritical carbon dioxide (SCCO2) sequestration and EGR in tight gas reservoirs were presented. Results of phase behavior testing revealed that the adsorption capacity of SCCO2 in tight sandstone is more than 50 % higher than that of natural gas in tight sandstone, and the diffusion coefficient of SCCO2 in natural gas is too low (