Search

The dissolved nitrate is one of the major essential nutrients for primary production in the tropical ocean and it is brought to the surface though mixing. The depth of nitracline determines how much of nitrate enters to the upper ocean through mixing. The depth of nitracline is traditionally estimated using nitrate concentrations measured at standard depths that introduces significant error due to interpolation of data. Based nitrate profiles measured at 5 m interval using nitrate sensors onboard Argo, the exact depth of nitracline was derived in the Bay of Bengal that displayed a significant linear relationship with depth of 26°C isotherm (D26). Based on climatological D26, the temporal and spatial variations in the depth of nitracline was estimated for the entire Bay of Bengal. The depth of nitracline varied between 5 and 80 m with large spatial and temporal variability in the Bay of Bengal and it is 5–20 m deeper than simulations of numerical models. The relationship between the depth of nitracline and photic zone integrated primary production indicates that 7.5 ± 3 mgC m−2 d−1 of primary production increases due to shallowing of 1 m of depth of nitracline. Therefore, models seem to be over estimating the photic zone integrated primary production by 5%–25% in the Bay of Bengal. The numerical models may improve the simulation of primary production and carbon cycling by accounting the accurate estimation of depth of nitracline in the model initialization. Plain Language Summary: In the tropical ocean, nitrate mainly controls the primary production and identifying the depth of nitracline, where nitrate concentration was 1 μM from that of surface, is important in simulating primary production by numerical models. All the numerical models are using nutrietns profiles collected at the standard depth and estimated depth of nitracline. Since the data collected at standard depth, and interpolation between depth may result in large error in the computation of nitracline depth. We used high depth resolution nitrate data collected by sensors and estimated nitracline depth and the same compared with modeled data. It was observed that models are estimating shallow nitracline than actual as a result higher biological response is simulated than reality. This exercise would be useful in improving model simulation in future. Key Points: The depth of nitracline is strongly controlled by depth of 20°C isothermDeeper nitracline depth was noticed during spring and shallowers during summerModels estimate shallower nitracline depth by 5–20 m than measured [ABSTRACT FROM AUTHOR]

This paper aims to study the changes in the Indian Ocean seawater pH in response to the changes in sea‐surface temperature, sea‐surface salinity, dissolved inorganic carbon (DIC), and total alkalinity (ALK) over the period 1980–2019 and its driving mechanisms using a high‐resolution regional model outputs. The analysis indicates that the rate of change of declining pH in the Arabian Sea (AS), the Bay of Bengal (BoB), and the Equatorial Indian Ocean (EIO) is −0.014 ± $\pm $ 0.002, −0.014 ± $\pm $ 0.001, and −0.015 ± $\pm $ 0.001 unit dec−1, respectively. Both in AS and BoB (EIO), the highest (lowest) decadal DIC trend is found during 2000–2009. The surface acidification rate has accelerated throughout the IO region during 2010–2019 compared to the previous decades. Further, our analysis indicates that El Ninõ and positive Indian Ocean Dipole events lead to an enhancement of the Indian Ocean acidification. The increasing anthropogenic CO2 uptake by the ocean dominantly controls 80% (94.5% and 85.7%) of the net pH trend (1980–2019) in AS (BoB and EIO), whereas ocean warming controls 14.4% (13.4% and 7.0%) of pH trends in AS (BoB and EIO). The changes in ALK contribute to enhancing the pH trend of AS by 5.0%. ALK dominates after DIC in the EIO and, similar to the AS, contributes to increasing the negative pH trend by 10.7%. In contrast, it has a buffering effect in the BoB, suppressing the pH trend by −5.4%. Plain Language Summary: The oceans play a significant role in regulating the amount of CO2 in the atmosphere. The increasing oceanic uptake of CO2 counterbalances the increase in atmospheric CO2. This uptake has a considerable impact on marine biogeochemistry, leading to pH and alkalinity imbalances in the water column, commonly referred to as ocean acidification. In an acidic ocean, excess CO2 reacts with seawater to form carbonic acid, which is highly unstable and undergoes further reduction by releasing hydrogen ions (H+) and acidifying the seawater (reduces the pH). Several studies have projected a decline of upper ocean pH by 0.3–0.4 by the end of the 21st century, which has the potential to reduce oceanic biological production considerably. The number of available observations to study Indian Ocean acidification is limited. There is a critical need to understand the status of Indian Ocean acidification and identify its key drivers. This article consolidates the current level of understanding about the Indian Ocean acidification based on the available field observations, reconstructed data sets, and model simulations. Key Points: The Indian Ocean pH is decreasing at an average rate of 0.015 dec−1 from 1980 to 2019The trend of dissolved inorganic carbon primarily drives an increasing ocean acidification trend in the Indian OceanEl Ninõ and positive Indian Ocean Dipole events lead to an enhancement of the Indian Ocean acidification [ABSTRACT FROM AUTHOR]

Developing novel photocatalytic materials for removing organic contaminants has been a research focus. The current study reports the synthesis of third-generation photocatalysts perovskites and their photocatalytic efficacy. The lead-free cesium-based titanium halide Cs2TiI6 double perovskite was successfully synthesized via the solution processing method and characterized by various spectroscopic and morphological characterization techniques such as X-ray diffraction (XRD), UV-visible spectroscopy, Zeta potential, and Transmission Electron Microscope (TEM). The novel aspect of this study is to investigate the photocatalytic efficacy of the Cs2TiI6 double perovskite. Various morphology and spectroscopy characterization insights about synthesized photocatalysts were explored. Eosin Y (EY) and Eosin B (EB) were chosen as the model compounds for degradation in this work due to their wide applications in industry. The photocatalytic degradation efficiency of Eosin Y and Eosin B dye by Cs2TiI6 perovskite photocatalysts after exposure of 240 minutes to visible light was 85.08% and 13.66% respectively. The rate constant of degradation of Eosin Y is approximately 14.66 times larger than that of Eosin B. [ABSTRACT FROM AUTHOR]

The toxicity and stability concerns of lead based perovskite solar cells have limited the commercialization. The lead-free Cesium based double perovskite could be a viable answer to these issues. In this present work a theoretical analysis of Cesium based double perovskite solar cell using Spiro-OMeTAD as hole transport layer and effect of different ETLs such as SnO2, ZnO-NR, TiO2 and CdS has been studied. The optimized active layer thickness of 0.3 μm has been used and a device structure of FTO/ETLs/Cs2AgBiBr6/Spiro-OMeTAD/Cu was simulated. The Solar Cell Capacitance Simulator (SCAPS-1D) was used for one dimensional simulation and analysis. The maximum PCE of 5.62 % was found using SnO2 as ETL. The device performance has been optimized by employing various ETLs and the most suitable ETL for this structure was found to be SnO2. The maximum quantum efficiency of 86.09 % has been found for SnO2 electron transport layer. The simulation results obtained in this study are encouraging and will provide insightful guidance in replacing toxic Pb-based perovskite with eco-friendly inorganic perovskite solar cell. [ABSTRACT FROM AUTHOR]

To take precautionary measures for the environment to diminish the toxic gases emitted from fossil fuels; an alternative fuel has to replace fossil fuel. Biofuel an alternative fuel can replace the counterpart. In this work, biofuel is synthesized by using a novel organic-inorganic perovskite-based nanocomposite as a catalyst. The synthesized catalyst has been characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The transesterification method is used for biofuel synthesis. Researchers across the globe have mostly synthesized biofuel especially biodiesel by transesterification method where temperature plays a major role in the catalytic reaction. Most of the researchers reported the synthesis of biofuel by using heterogeneous catalysts at higher temperatures which is greater than 60 °C but in this study, the synthesis of biofuel at ambient temperature is attempted under the influence of UV light. The synthesized biofuel is characterized by Gas Chromatography Mass Spectrometry (GCMS). GCMS signifies the different fatty acid methyl ester compositions present in the biofuel which assured the presence of all the necessary compounds in a biofuel. [ABSTRACT FROM AUTHOR]