On-site sanitation has emerged as a preferred mode of sanitation in cities experiencing rapid urbanization due to the high cost involved in off-site sanitation which requires conventional sewerages. However, this practice has put severe stress on groundwater especially its quality. Under the above backdrop, a study has been undertaken to investigate the impact of on-site sanitation on quality of groundwater sources in two mega cities namely Indore and Kolkata which are situated in two different geological settings. The parameters for the studies are distance of groundwater source from place of sanitation, effect of summer and monsoon seasons, local hydro-geological conditions, and physico-chemical parameters. NO(3) and fecal coliform concentrations are considered as main indexes of pollution in water. Out of many conclusions which can be made from this studies, one major conclusion is about the influence of on-site sanitation on groundwater quality is minimal in Kolkata, whereas it is significant in Indore. This difference is due to the difference in hydrogeological parameters of these two cities, Kolkata being on alluvium quaternary and Indore being on Deccan trap of Cretaceous to Paleogene age.

Variability of groundwater quality parameters is linked to various processes such as weathering, organic matter degradation, aerobic respiration, iron reduction, mineral dissolution and precipitation, cation exchange and mixing of salt water with fresh water. Multivariate statistical analyses such as principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied to the standardized data set of eleven groundwater quality parameters (i.e. pH, Ca2+, Mg2+, Na+, K+, Fe3+, alkalinity, NO3-, Cl-, SO4(2-), TDS) collected during the post-monsoon and the summer seasons in order to elicit hydrologic and biogeochemical processes affecting water quality in the unconfined aquifer beneath Puri city in eastern India. The application of PCA resulted in four factors explaining 73% variance in post-monsoon and 81% variance in summer. The HCA using Ward's method and squared Euclidean distance measure classified the parameters into four clusters based on their similarities. PCA and HCA allowed interpretation of processes. During both post-monsoon and summer seasons, anthropogenic pollution and organic matter degradation/Fe(III) reduction were found dominant due to contribution from on-site sanitation in septic tanks and soak pits in the city. Cation exchange and mineral precipitation were possible causes for increase in Na+ and decrease in Ca2+ concentration in summer. Fresh water recharge during monsoon and Sea water intrusion in summer are attributed as significant hydrologic processes to variations of the groundwater quality at the study site.

Sustainable land restoration is the key to restore degraded land, halt biodiversity loss, and reinstate ecosystem services for human well-being. Restoration needs to be planned and conducted with due recognition to growing climate uncertainty with an evolved understanding of the future restoration targets. The present opinion article attempts to provide an overview on an integrated climate sensitive restoration framework that recognizes the local participation in mapping degraded lands, identification of species for supporting species modeling to better understand climate uncertainty. Involvement of citizen sciencebased restoration monitoring tools can contribute to big data analytics for ecological monitoring and policy support. The Framework potentially helps in sustainable land restoration by transformative changes for achieving the UN Decade on Ecosystem Restoration (2021-2030), Sustainable Development Goals 15, and addressing the post-2020 Global Biodiversity Framework. However, to realize success, climate finance mechanisms to drive restoration should be seriously considered for reducing bias and enhancing opportunities of equitable sharing in the era of corruption, authoritarianism, and regulatory capture.

The Kovaya Limestone Mine is situated on the Saurashtra coast of India. Though the mine is dependent on the desalination plant installed in the plant for its domestic and industrial water requirements, there is significant withdrawal of groundwater by the large number of bore wells and open wells, which are present in the agricultural fields lying in and around the leased area of the mine. The heavy withdrawal of groundwater has led to intrusion of seawater. The present work entails study of possible seawater intrusion by chemical analysis of major cations and anions in selected groundwater samples. Very high total dissolved solids in the range of >1,000 mg/l and high chloride in the range of 103 mg/l to 3,899 mg/l have been measured in the groundwater samples. 'Resistivity Imaging Survey' has also been carried out on selected profiles in the study area. The Electrical Resistivity Tomography images indicate very low resistivity zones (~0-3 Omega m) in the bottom portion of the resistivity depth section. These low resistivity zones can be interpreted to be due to seawater intrusion. The resistivity sections on the excavated Pits, where mining is going on, indicate possibilities of seawater intrusion. Hence, protection from seawater intrusion is recommended through restriction of mining up to the safe level.

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Groundwater pollution in the vicinity of a landfill site in Nagpur, India is assessed with the help of resistivity imaging and GPR tools. The resistivity imaging survey indicates high conductive anomalies in the topsoil as well as the underlying fractured rocks. Significant reflections from the GPR records known as radargrams are extracted with the help of maximum peak module and Hilbert transform module in RADAN 6. These reflections can be attributed to presence of fractures, which are potential pathways for migration of the fluid. The geophysical findings are strengthened by the results of groundwater analysis from wells located close to the profile where resistivity and GPR survey have been carried out. The study has indicated the vulnerability of the unconfined aquifer underlying the predominantly clay layer.

On-site sanitation is increasingly adopted in urban cities in India. The adoption of on-site sanitation system puts the groundwater resources in the vicinity of the system at a greater risk. Microbial contaminants as well as chemical contaminants like Chloride and Nitrate are generated from human waste. These contaminants travel through the medium and ultimately get in contact with the groundwater. Hence, the groundwater sources are vulnerable to nitrate contamination near the on-site sanitation systems. The present study indicates significant Nitrate and Chloride contamination in samples collected close to on-site sanitation systems. The recommended limit set by the Bureau of Indian standards (BIS) limit of 45 mg/l for Nitrate concentration is also exceeded in few samples. The study indicates that Bacterial as well as Nitrate contamination is more in Monsoon as compared to Summer.