Ecosystem-scale insights into the dynamics of dissolved organic matter in an Asia's largest brackish water lagoon: Sources, fluxes, and biogeochemical significance.

A twenty-four month long observational study conducted in an Asia's largest brackish water ecosystem, Chilika Lagoon, India, aimed to unravel dissolved organic matter (DOM) dynamics in this tropical brackish water ecosystem. The study assessed the interplay between allochthonous and autochthonous DOM sources during lean and active flow periods based on regional rainfall. Dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) fluxes were analyzed, considering catchment runoff, phytoplankton production, benthic-pelagic interactions, and sea-lagoon exchanges as contributors. Contrary to conventional thinking, the study found autochthonous processes to be more significant than conservative mixing in shaping DOM dynamics. It introduced a novel conceptual model illustrating the multifaceted origins of DOM, encompassing catchment runoff, phytoplankton, benthic-pelagic interactions, bacterial activity, and sea-lagoon exchanges. These findings underscore the importance of holistic management strategies for Chilika Lagoon to preserve its ecological health, given its vital role in global carbon cycling, fisheries, and aquaculture.

Assessment of heavy metal distribution in seawater of Kakinada Bay, a tropical mangrove-rich coastal environment.

The main objective of the present study is to estimate the heavy metal concentrations and ecological risk index (ERI) in the seawater of Kakinada Bay. Turbidity, suspended particulate matter (SPM), pH, salinity, dissolved oxygen, along with heavy metals were recorded from twelve locations of the Bay to understand its hydrographical conditions. The distribution of environmental variables and heavy metal concentrations was noticed mostly from the south to north gradient. Significant positive correlations were detected in some pairs of metals such as Cu with Zn (R2 = 0.515; p < 0.05), Pb with both Cr (R2 = 0.810; p < 0.01) and Cd (R2 = 0.511; p < 0.05), and Cr with Ni (R2 = 0.573; p < 0.05) indicating their common origin. The ERI values (7.93-35.2) of seawater of Kakinada Bay in the present study were in the ecologically high-risk category. Industrial operations, domestic sewage, and natural processes are the major contaminant sources of Kakinada Bay leading its environment to a potential ecological concern.

Quantification and In Silico Toxicity Assessment of Nimesulide and its Related Substances.

Availability of analytical method which is compatible with both Ultra high performance liquid chromatography (UHPLC) and Liquid chromatography mass spectrometry to identify and quantify the impurities in pharmaceutical products is an advantage for drug product development; such analytical method was developed for Nimesulide using a fused core column. Ammonium acetate and methanol were used as mobile phase in the gradient elution at a detection wavelength 230 nm. Quality-by-design principles helped in identifying the critical method development parameters and design space. Limit of detection and the limit of quantification are 0.025 and 0.075%, respectively. Precision of the method is <0.4% RSD and correlation coefficient is >0.999 for Nimesulide and all related substances. Accuracy of Nimesulide ranged from 99.3 to 100.4% at assay concentration. Application of this method in stability analysis has been demonstrated by analyzing stressed samples. The method was validated for specificity, linearity, accuracy, precision and robustness in compliance with International Conference on Harmonization (ICH) Q2(R1). This is the first reported UHPLC method for the estimation of Nimesulide and its related substances. According to ICH M7 guidelines, all impurities were assessed for genotoxicity, LD50, skin sensitization, irritation potential and carcinogenicity using Derek and TOPKAT software. Combined knowledge of analytical and toxicology assessment will help in developing safe and quality product.