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The long-term average annual soil loss (A) and sediment yield (SY) in a tropical monsoon- dominated river basin in the southern Western Ghats, India (Muthirapuzha River Basin, MRB; area: 271.75 km²), were predicted by coupling the Revised Universal Soil Loss Equation (RUSLE) and sediment delivery ratio (SDR) models. Moreover, the study also delineated soil erosion risk zones based on the soil erosion potential index (SEPI) using the analytic hierarchy process (AHP) technique. Mean A of the basin is 14.36 t ha-1 year-1, while mean SY is only 3.65 t ha-1 year-1. Although the land use/land cover types with human interference show relatively lower A compared to natural vegetation, their higher SDR values reflect the significance of anthropogenic activities in accelerated soil erosion. The soil erosion risk in the MRB is strongly controlled by slope, land use/land cover and relative relief, compared to geomorphology, drainage density, stream frequency and lineament frequency. [ABSTRACT FROM AUTHOR]

Radon (222Rn) is a colourless, odourless, inert, and radioactive noble gas (t 1/2 = 3.8 days) that emanates from rocks and soils as a result of the alpha decay of its parent, radium (226Ra) in the decay series of uranium-238, is the focus of this study. Radon is produced in the crystal lattice of the minerals and emanates out through alpha recoil. It dissolves in water, and is also found in soil and air. Its distribution in water is more pertinent for scientific investigations. It can be measured by various methods. Certain properties of radon enable it to serve as an ideal tracer, viz., short-half life, inertness, high abundance in groundwater than surface water, preferential partitioning, sensitivity to sudden changes in subsurface conditions, non-invasiveness etc. This paper reviews the state-of-the-art techniques on the measurement of dissolved radon in water and its potential applications as a tracer and precursor in several hydrogeological and geological applications like understanding the surface water - groundwater interactions, hydrograph separation of streams, estimation of Submarine Groundwater Discharge (SGD), study of hydrodynamics and water balance of lakes, earthquake predictions, locating geological structures (faults/lineaments), geochemical explorations, NAPL contamination studies etc. Among the various applications presented, radon based approach is found to be more reliable in water resources domain than seismic precursory studies. The interpretations based on radon study in the above applications will pave the way for the improved understanding of the hydrological processes, and thus, help the planners and water managers for the sustainable development and management of water resources. [Display omitted] • The usefulness of radon (222Rn) as a tracer for geological and hydrogeological studies is systematically reviewed. • Summarized the analytical methods for the measurement of 222Rn. • The ubiquitous presence of 222Rn makes it a suitable tracer for studying surface water – groundwater interactions. • 222Rn application outshines the conventional time-consuming invasive techniques. [ABSTRACT FROM AUTHOR]

Studies on occurrence of radon in the environment are receiving growing attention worldwide due to its adverse impact on human health. Despite that, the dissolved radon in water is found to be a useful tracer in many hydrogeological studies. Although, several studies focused on the occurrence of high 222Rn in groundwater, the processes responsible for its variation is still not well understood. Hence, an attempt has been made in the present study to elucidate the underlying factors influencing the abundance 222Rn in hard rock (gneissic) aquifers of Karamana River Basin, southwest India. 222Rn in groundwater was analyzed in 71 dug wells during the pre-monsoon period of 2017. A large variability in 222Rn activities (170–68,350 Bq/m3) was noticed in groundwater and high activities were mainly seen in the khondalite formation. No significant dependencies between 222Rn activity and depth to water table, groundwater temperature and electrical conductivity were observed. However, majority of the presence of high 222Rn activity in groundwater matches with the location of lineaments. Furthermore, radium content in the host rock, degree of weathering and fracturing and the emanation coefficient of the rock were found to have an important bearing on the occurrence of radon in groundwater. The underlying factors influencing the abundance of radon in hard rock aquifers were also conceptualized. Thus, the study highlights the usefulness of 222Rn as a potential tool in delineating the macro-structural features like fractures/lineaments that are significant repositories of groundwater, which could be explored for groundwater development in hard rock terrains. Image 1 • Occurrence, distribution and factors influencing radon in groundwater were evaluated. • High radon activities were mainly observed in khondalite (gneiss) formation. • Radium content in rock and proximity to lineaments control the radon in groundwater. • Radon release mechanisms into the groundwater were conceptualized. [ABSTRACT FROM AUTHOR]

The backwater of Veli-Akkulam, adjoining the Arabian Sea in the south-west part of Indian Peninsula, is a coastal wetland system and forms an integral part of the local ecosystem. In addition to the usual marine interactions, this water body is subjected to anthropogenic interference due to their proximity to the Thiruvananthapuram City urban agglomeration. This paper showcases how an urban agglomeration alters wetland system located within a tropical monsoonal environment. Water samples from this lake together with different feeder streams reveal that the lake is under the threat to eutrophication. A spatio-temporal analysis has shown that the lake and adjacent wetlands are shrinking in a fast pace. Over a period of about seven decades, the lake has shrunk by 28.05 % and the wetlands by 37.81 %. And hence, there is a pressing requirement of eco-management practices to be adopted to protect this lake. [ABSTRACT FROM AUTHOR]

The present study on geochemical evolution of groundwater is taken up to assess the controlling processes of water chemistry in the Western Delta region of the River Godavari (Andhra Pradesh), which is one of the major rice-producing centers in India. The study region is underlain by coarse sand with black clay (buried channels), black silty clay of recent origin (floodplain) and gray/white fine sand of modern beach sediment of marine source (coastal zone), including brown silty clay with fine sand (paleo-beach ridges). Groundwater is mostly brackish and very hard. It is characterized by Na > Mg > Ca:HCO > Cl > SO > NO , Na > Mg > Ca:Cl > HCO > SO , and Mg > Na > Ca > or < K:HCO > Cl > or > SO facies. The ionic relations (Ca + Mg:HCO , Ca + Mg:SO + HCO , Na + K:TC, Na + K:Cl + SO , HCO :TC, HCO :Ca + Mg, Na:Cl and Na:Ca) indicate that the rock weathering, mineral dissolution, evaporation and ion exchange are the processes to control the aquifer chemistry. Anthropogenic and marine sources are also the supplementary factors for brackish water quality. These observations are further supported by Gibbs mechanisms that control the water chemistry. Thus, the study suggests that the initial quality of groundwater of geogenic origin has been subsequently modified by the influences of anthropogenic and marine sources. [ABSTRACT FROM AUTHOR]

The chemistry of groundwater in the coastal region between Chirala and Ongole of Andhra Pradesh, India shows pollution to varying extent. The relative contribution of ions in six zones divided based on TDS indicates unsuitability of groundwater here for drinking, irrigation and industrial use. The water is brackish except in first zone and further alkaline. TDS is less than 1,000 mg/L in first zone, while it is more in other zones. This classification of groundwater into zones is also investigated by hydrogeochemical facies, genetic classification, mechanisms of groundwater chemistry and geochemical signatures. Hydrogeochemical facies of Na+>Mg2+>Ca2+:HCO3- >Cl->SO42- is observed from zone I, while that of Na+>Mg2+>Ca2+:Cl->HCO3- >SO42- from second to sixth zones. The genetic classification of groundwater in first and second zones is HCO3- type and supported by good drainage conditions, while zones III to VI belong to Cl- category evident from poor drainage scenario. The location of six zones on mechanisms of groundwater chemistry supports sluggish drainage conditions of second to six zones, while predominate rock-water interaction in first zone. The geochemical signatures (HCO3- :Cl->1 and Na+:Cl- < 1) also endorse the pollution. The quantities of chemical species (Mg2+, Na+, K+, HCO3- , Cl-, SO2- , NO3- and F-) and TDS in all zones are far greater than the stipulated limits for drinking. The United States Salinity Laboratory plots discriminated the suitability of groundwater in second to sixth zones for irrigation after only special soil treatment. Higher concentrations of TDS, HCO3- , Cl- and SO42- in all zones render it unsuitable for industry too. This information is crucial for public and civic authorities for taking up strategic management plan for preventing further deterioration of hydrogeochemical environmental conditions of this part of the coastal region. [ABSTRACT FROM AUTHOR]

The article describes the transport phenomenon of some commonly used laboratory organic solvents which differ in their solubility parameter value through polymer blend nanocomposites membrane prepared by melt mixing. The three solvents that were used are hexane, toluene and xylene which differed widely in their solubility parameter values. The motivation for the study was to know the effect of solubility parameter on the diffusion transport properties of NR/NBR (natural rubber/nitrile rubber) blends. The solvent uptake, diffusion, sorption and permeation constants were investigated and were found to decrease with organically modified montmorillonite (OMt) content at lower loading. The mode of transport through NR/NBR nanocomposites was found to be anomalous. The difference in solubility parameter value greatly influenced the transport properties. The dependence of various properties on OMt content was supported by morphological analysis data. The effect of blend ratio, solvent size and OMt loading on the diffusion of aromatic and aliphatic solvents through NR/NBR blend systems were investigated. The swelling coefficient values also decreased upon the addition of fillers indicating the presence of hindered path for solvents to diffuse into the polymer matrix. The better reinforcement at lower filler loading was confirmed from the cross-link density values and mechanical properties. The transport data obtained were applied to mathematical models for predicting the diffusion behaviour through nanocomposite membranes and to elucidate the physical mechanism of transport. Graphical abstract: [Figure not available: see fulltext.]. [ABSTRACT FROM AUTHOR]

The preparation of manganese malonate crystals by gel method and its spectroscopic studies are reported. X-ray diffraction (XRD) pattern reveals the crystalline nature. The FTIR and FT Raman spectra of the crystals are recorded and the vibrational assignments are given with possible explanations. Diffuse reflectance spectroscopy (DRS) is used to measure the bandgap ( E) of the material. [ABSTRACT FROM AUTHOR]

Melt rheology and extrudate morphology of polystyrene (PS)/polybutadiene (PB) blends were studied with special reference to the effect of blend ratio and two different types of compatibilisers, the random copolymers and block copolymers. Uncompatibilized blends had viscosities approximately intermediate between those of the component polymers. In the case of uncompatibilized blends both positive and negative deviation was observed in the viscosity-composition curve at different shear rate range studied. The viscosity of the compatibilized blend was found to increase when a few percent of block copolymer was added. However, at high concentrations of the compatibiliser, the viscosity values leveled off. This is due to interfacial saturation. Morphological investigations indicated that the size of the dispersed phase initially decreased when a few percent of the block copolymer was added followed by a clear leveling off at higher concentration. However, the random copolymer was not an effective interface modifier in agreement with microscopy study. These experimental results supports the earlier investigations of solid state NMR studies on these blends ( Polymer (2005) 46(22):9385). [ABSTRACT FROM AUTHOR]

Hydrochemical investigation of open well and river water samples of Thuthapuzha Sub-basin of Bharathapuzha, Kerala, was carried out to determine the spatial and temporal variations in the physico-chemical parameters. The suitability of water for drinking and irrigation purposes and the processes controlling the water chemistry were also assessed. The study area experiences a humid tropical climate and heavy rainfall of ~ 3830 mm/year. Thirty-five open well and nine river water samples were collected during the pre-monsoon, monsoon and post-monsoon seasons. The chemical properties of the river water samples were dominated by alkaline earths and weak acids (CaHCO3 type). Even though majority of the open well samples belonged to CaHCO3 type, few samples belonged to NaCl, mixed CaMgCl and mixed CaNaHCO3 water type. The groundwater and river water chemistry of the region was influenced by the chemistry of the host rock rather than precipitation and evaporation. Except pH and the total iron concentration, all other physico-chemical parameters of the open well samples of the study area were within the acceptable limit of drinking purposes. The physico-chemical parameters of the entire river water samples were within the acceptable limit for drinking purpose. The entire open well and river water samples were suitable for irrigation purposes. [ABSTRACT FROM AUTHOR]