To obtain insightful knowledge of geochemical process controlling fluoride enrichment in groundwater of the villages near Shilabati river bank, West Bengal, India, multivariate statistical techniques were applied to a subgroup of the dataset generated from major ion analysis of groundwater samples. Water quality analysis of major ion chemistry revealed elevated levels of fluoride concentration in groundwater. Factor analysis (FA) of fifteen hydrochemical parameters demonstrated that fluoride occurrence was due to the weathering and dissolution of fluoride-bearing minerals in the aquifer. A strong positive loading (> 0.75) of fluoride with pH and bicarbonate for FA indicates an alkaline dominated environment responsible for leaching of fluoride from the source material. Mineralogical analysis of soli sediment exhibits the presence of fluoride-bearing minerals in underground geology. Hierarchical cluster analysis (HCA) was carried out to isolate the sampling sites according to groundwater quality. With HCA the sampling sites were isolated into three clusters. The occurrence of abundant fluoride in the higher elevated area of the observed three different clusters revealed that there was more contact opportunity of recharging water with the minerals present in the aquifer during infiltration through the vadose zone.

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Landfill biomining (LFBM) has been proposed as a viable method for the reclamation of legacy waste dumpsites as well as the subsequent recovery of valuable resources and land value spaces. Despite these advantages, the potential of LFBM faces a significant challenge due to the composition, characteristics and end-use of the excavated materials. This paper assesses the composition of the excavated waste obtained during the LFBM operation of the four legacy waste heaps at the Boragaon dumpsite in North-East India and determines the physicochemical characteristics crucial for the material and energy recovery from the key reclaimed fractions. The compositional analysis revealed that the proportion of combustible and non-combustible fractions decreases from the youngest heap HP4 to the oldest heap HP1 due to variations in the consumption habits of the local community and the inadequate recycling of recyclable materials. However, the proportion of fine fraction (FF) shows an increasing trend from HP4 to HP1, suggesting enhanced biodegradation of easily degradable waste over the years. The proximate and energy content analysis suggest that refuse-derived fuel (RDF) preparation is the most suitable valorization option for the combustible fractions since surface defilements are too high for good quality material recovery. The elevated amount of organic matter and leachable heavy metals indicate that unrestricted reuse of FF as earth-fill material can cause long-term settlements and groundwater contamination, respectively. Even though every dumpsite is different in characteristics, the findings of this case study can assist in developing new strategies for recycling excavated waste.

<p>The contamination of groundwater by geogenic sources is a major problem in many nations, especially those in the developing world. Fluoride (F) is one of the most pervasive and well-documented geogenic contaminants because of the severe health risks it poses due to its toxicity. F contamination in groundwater in India has been the subject of intense research over the past many decades. In this article, we describe the underlying geochemical process liable for F contamination as well as the factors controlling its spatiotemporal distribution in the Sedimentary Alluvial Plain (SAP) of Bankura District, West Bengal, India. To achieve the desired objective, representative groundwater samples were collected from tube wells and hand pumps at different locations of the study region during pre- and post-monsoon seasons. Collected samples were subjected to F and other hydrochemical analysis following standard test methods. Analysis shows that 37% of all groundwater samples collected during the pre-monsoon period have fluoride levels over 1.5 ppm (the limit specified by the World Health Organization, Geneva, 2004); however, the contamination level dropped to 30% during the post-monsoon period. The investigation of groundwater level changes indicates that, as water levels rise during the post-monsoon, F concentrations decrease due to the dilution effect. Piper trilinear diagram suggested Na-Ca-HCO<sub>3</sub> type of groundwater for both seasons. According to Gibbs diagrams, rock-water interactions (mineral dissolution) are responsible for major ion chemistry in groundwater samples. Factor analysis (FA) of hydrochemical parameters revealed that the occurrence of F in groundwater was due to the weathering and dissolution of fluoride-containing minerals. X-ray diffraction (XRD) analysis of SAP sediments further confirmed the presence of fluoride-bearing minerals (muscovite and fluorite) in the subsurface lithology of the region. A substantial positive loading (> 0.75) of F with pH and bicarbonate for FA demonstrates that F is being leached from the host material by an alkaline-dominated environment. To account for the spatial variability and seasonality to the spatial change of F concentration in groundwater of the SAP, geographical information systems tools and inverse distance weighting interpolation method were used. The results revealed that significant spatiotemporal variability of F contamination was mainly influenced by the recharging rainwater and the average recharge altitude of groundwater in the area under study. The contamination level is significant in the elevated region where replenishing rainwater is more likely to come into contact with fluoride-bearing minerals when it infiltrates and percolates through the vadose zone. This phenomenon increases the F leaching through chemical weathering along groundwater flow pathways. The findings of this study can serve as a scientific foundation for the efficient management of F-contaminated groundwater in the SAP.</p> <p> </p>

Non-engineered landfills or open dumpsites are the most common solid waste disposal facilities in developing countries. The absence of proper liner systems in these non-engineered landfills causes deterioration of the nearby surface and sub-surface water resources via leachate migration beneath and around the landfill site. Therefore, it is necessary to understand the contaminant transport mechanisms to predict the long-term impact of a landfill in the subsurface groundwater system for the development of possible remedial measures. The present research aims to simulate the subsurface transport of two heavy metals (Lead and Cadmium) from a non-engineered landfill situated at Boragaon, Guwahati, in North-East India, to the nearby eco-sensitive wetland, Deepor Beel (Ramsar site no. 1207). Based on the hydrogeological information collected from the central groundwater board (CGWB) and field investigation, a single-layer conceptual model of the study area was constructed using Groundwater Modeling Systems (GMS) software. Input parameters for the contaminant transport model were determined from laboratory batch and column experiments with the soil samples collected near the vicinity of the landfill. Numerical simulation of groundwater flow and advective–dispersive transport was then performed using MODFLOW and MT3DMS codes to understand the migration pathway and spatiotemporal variation of heavy metals concentration. The simulation results produced different size plumes of heavy metal contaminated groundwater, which are predominantly expanded in the longitudinal direction, indicating advection-dominated transport mechanism. Particle-tracking simulations further revealed that travel times for the plumes of Lead (Pb)and Cadmium (Cd) to reach the wetland were about 22 and 16 years, respectively. The trend of contour lines shows that, after reaching the wetland, the concentration of heavy metals will be enough to degrade its water quality within a few years. The results obtained from the current simulation study can be used for designing and installing engineered barriers to mitigate the migration of heavy metals into the wetland.