No abstract

No abstract

Thermochemical conversion of world top crops (rice and wheat) has been extensively investigated (TGA, DTF, SEM, XRD, BET, EA), and main insights are discussed in light of materials and process kinetics. Overall, the results show that the rice husk presents lower reactivity than the wheat straw for all thermal processes regardless of the final temperatures (300°C− 1300°C), residence times (0.6 s−300 min), and atmospheres (100−340 mL·min −1 N 2 /air). The higher reactivity of wheat straw is attributed not only to higher alkali and ash contents but also to differences in both silica morphology and graphitic structure after pyrolysis. Chars produced from slow pyrolysis present more homogeneous characteristics than those produced from fast pyrolysis. Combustion of the chars from slow pyrolysis (up to 900°C) show similar kinetic parameters with activation energies, E a , of 101.8 and 101.0 kJ·mol −1 with pre-exponential factor, A, of 4.3 × 10 7 and 9.6 × 10 7 min −1 for rice husk and wheat straw, respectively; while chars from fast pyrolysis (up to 1300°C) show a range of values. Reaction times at 90 wt % loss (min) and rate constants k o (min −1 ) gives a more clear difference in values even for chars from slow pyrolysis with 12.4 and 0.221 for rice husk and 4.3 and 0.499 for wheat straw, correspondingly. These results are discussed herein according to changes in the physical and chemical characteristics of the nascent chars and, consequently, on their reactivity.

Marine heatwaves (MHWs) are a major concern worldwide due to their increasing impacts in recent years, and these extreme events may trigger deoxygenation of coastal waters affected by sewage and eutrophication. Here we investigate the combined effects of MHWs and nutrient enrichment on the water quality and biodiversity of the Bay of Santa Catarina Island (Brazil). We used historical (1994–2020) sea surface temperature data from satellites and in situ physical, chemical and biological parameters to assess temporal trends. Oxygen levels have been decreasing whilst phosphorus levels have been increasing in the bay. During the austral summer of 2020 a regional sea surface heatwave was detected by satellite, lasting for 9 days and coinciding with our research cruise. During this period, seawater temperatures reached 29.8°C and anoxia was detected for the first time in the bay. A decrease in macrobenthic and phytoplankton community richness correlated with decreases in oxygen both through time and towards more urbanized areas. Overall, poor wastewater treatment is a key stressor that combined with MHWs to degrade coastal waters. Mitigation strategies are needed to minimize the impact of MHWs, including improved sewage treatment, restoration and conservation of wetlands and the use of nature-based technologies to promote coastal ecosystem recovery.

No abstract