Delineation of submarine groundwater discharge and seawater intrusion zones using anomalies in the field water quality parameters, groundwater level fluctuation and sea surface temperature along the Gujarat coast of India.

Nature mediated processes like seawater intrusion (SWI) and its complementary processes like submarine groundwater discharge (SGD) often cause severe water stress on the coastal water resources worldwide. The present work attempts to delineate the SWI and SGD zones along the North-Western coast of India (constituting the entire coastline of Gujarat) which is currently facing severe water crises due to the freshwater salinization and water loss through the coastal aquifer system. In the present work site-specific water characteristics and groundwater level were used as a proxy for identifying the probable zones of SWI and SGD. For the delineation purpose, we have collected 540 water samples distanced at 5-10 km (seawater, porewater and groundwater; 180 each) from the entire coastline of Gujarat. Further, a three-tier validation system has been adopted for delineating the SWI and SGD zones followed by the physical verification of the locations through the integration of (i) Groundwater fluctuation dynamic, (ii) MODIS derived sea surface temperature (SST) anomaly, and (iii) Electrical conductivity (EC) based gradient mapping. The study has identified 9 out of 14 districts being vulnerable to SWI, whereas the remaining five districts from south Gujarat and the Saurashtra coast are suspectable for SGD. The present work will act as a preliminary basis for formulating a framework for the detailed investigation of the mixing process along the coast.

Evaluation, effect and utilization of submarine groundwater discharge for coastal population and ecosystem: A special emphasis on Indian coastline.

Submarine groundwater discharge (SGD) is an important process driven by marine and terrestrial forces. Low tide affects SGD the most, therefore the ideal time to detect SGD is the low tide, especially during spring tide. Techniques to detect and quantify SGD along with the understanding of the related aquifer characteristics is discussed in this study. Scientific community across the world is realizing the importance of studying and mapping SGD because in the scenario of climate change, this part of the global hydrological cycle is an important process and is known to have a significant effect on the marine ecosystem due to nutrient and metal inputs around the region of discharge. Therefore, understanding the processes governing SGD becomes very important. In this review, various components and processes related to SGD (e.g. Submarine Groundwater Recharge, Deep Porewater Upwelling, Recirculated Saline Groundwater Discharge), along with detailed discussion on impacts of SGD for marine ecosystem is presented. Also, it highlights the future research direction and emphasis is put on more research to be done keeping in mind the changing climate and its impacts on SGD.

Development of a rapid and ultra-sensitive RNA:DNA hybrid immunocapture based biosensor for visual detection of SARS-CoV-2 RNA.

The Development of reliable and field-compatible detection methods is essential to monitoring and controlling the spread of any global pandemic. We herein report a novel anti-RNA:DNA hybrid (anti-RDH) antibody-based biosensor for visual, colorimetric lateral flow assay, using gold nanoparticles, coupled with transcription-mediated-isothermal-RNA-amplification (TMIRA) for specific and sensitive detection of viral RNA. We have demonstrated its utility for SARS-CoV-2 RNA detection. This technique, which we have named RDH-LFA (anti-RNA:DNA hybrid antibody-based lateral flow assay), exploits anti-RDH antibody for immunocapture of viral RNA hybridized with specific DNA probes in lateral flow assay. This method uses biotinylated-oligonucleotides (DNAB) specific to SARS-CoV-2 RNA (vRNA) to generate a vRNA-DNAB hybrid. The biotin-tagged vRNA-DNAB hybrid molecules bind to streptavidin conjugated with gold nanoparticles. This hybrid complex is trapped by the anti-RDH antibody immobilized on the nitrocellulose membrane resulting in pink color signal leading to visual naked-eye detection in 1 minute. Combining RDH-LFA with isothermal RNA amplification (TMIRA) significantly improves the sensitivity (LOD:10 copies/µl) with a total turnaround time of an hour. More importantly, RDH-LFA coupled with the TMIRA method showed 96.6% sensitivity and 100% specificity for clinical samples when compared to a commercial gold standard reverse-transcription quantitative polymerase-chain-reaction assay. Thus, the present study reports a rapid, sensitive, specific, and simple method for visual detection of viral RNA, which can be used at the point-of-care without requiring sophisticated instrumentation.