Hydromechanics of the Koyna–Warna Region, India

Continuous reservoir-induced seismicity has been observed in the Koyna–Warna region in western India following the beginning of impoundment of Koyna and Warna Reservoirs in 1961 and 1985, respectively. This seismicity includes 19 events with M ≥ 5.0 which occurred in 7 episodes (I–VII) between 1967 and 2005 at non-repeating hypocentral locations. In this study, we examined the first six episodes. The seismicity occurs by diffusion of pore pressures from the reservoirs to hypocentral locations along a saturated, critically stressed network of NE trending faults and NW trending fractures. We used the daily lake levels in the two reservoirs, from impoundment to 2000, to calculate the time history of the diffused pore pressures and their daily rate of change at the hypocentral locations. The results of our analysis indicate that Episodes I and IV are primarily associated with the initial filling of the two reservoirs. The diffused pore pressures are generated by the large (20–45 m) annual fluctuations of lake levels. We interpret that critical excess pore pressures >~300 kPa and >~600 kPa were needed to induce Episodes I–III and Episodes IV–VI, respectively, suggesting the presence of stronger faults in the region. The exceedance of the previous water level maxima (stress memory) was found to be the most important, although not determining factor in inducing the episodes. The annual rise of 40 m or more, rapid filling rates and elevated dp/dt values over a filling cycle, contributed to the rapid increase in pore pressure.     

Petrotectonic setting of the provenance of Lower Siwalik sandstones of the Himalayan foreland basin,southeastern Kumaun Himalaya,India

Detailed petrography and modal analysis of 35 sandstone thin sections was carried out to determine petrotectonic setting of the provenance of the Lower Siwalik molasse of southeastern Kumaun Himalaya. The sandstones are fine‐ to coarse‐grained (0.14–0.63 mm), poorly‐ to moderately‐sorted and comprise lithic arenites, sublithic arenites and lithic greywackes. The sandstones invariably belong to the quartzolithic QtFL (Qt, total quartz; F, feldspar; L, lithic grains) and QmFLt (Qm, monocrystalline quartz; Lt, lithic grains plus polycrystalline quartz) petrofacies, and indicate their derivation from a quartzose‐ and transitional‐recycled orogen provenance under sub‐humid climatic conditions. The framework composition of the sandstones comprises abundant monocrystalline and polycrystalline quartz and low‐ to high‐grade metamorphic rock fragments, along with subordinate feldspar, characterized by low ratios of plagioclase to total feldspar, and accessory minerals. The framework composition and petrofacies characters of these texturally submature sandstones suggest their derivation mainly from the nearby located Great Himalaya terrane and subordinately from the Tethys and Lesser Himalayan terranes. A comparison of the data presented here with the previous similar data from Lower Siwalik of northwestern Pakistan, northwestern India, south‐central Kumaun, western Nepal and southeastern Nepal reveals that like the Lower Siwalik rivers in other sections, the Lower Siwalik rivers of the southeastern Kumaun too drained large parts of the Great Himalayan terrane and some parts of the Tethys and Lesser Himalayan terranes.     

Retardation of Fin Regeneration in Freshwater Fish Oreochromis mossambicusby Zinc

Regeneration of partially amputated caudal fin was studied in freshwater fish Oreochromis mossambicus exposed to sublethal concentrations of zinc (5.0 mg L^—1 and 10.0 mg L^—1) under ambient laboratory conditions over a period of 20 days. Caudal fin regeneration was measured on 5th, 10th, 15th and 20th day of exposure and after amputation. Significant ( p < 0.05) retardation in fin regeneration was observed on day 5th and 10th in fish exposed to the nominal concentration of 5.0 mg L^—1 Zn, while retardation was found highly significant ( p < 0.01) at all the observations in 10.0 mg L^—1. The maximum inhibition in caudal fin regeneration (20.8 % and 24.3 %) was found during the initial observation at both of the concentrations (5.0 mg L^—1 and 10.0 mg L^—1) of zinc exposure. Later on the regeneration rate was almost as good as in the control group. Thus in this study fin regeneration was significantly inhibited at all time points following Zn exposure as a detrimental effect of Zn to fish. This study demonstrates that fish caudal fin regeneration is a simple assay, sensitive and easy to perform, and can serve as a model to determine the toxicity of pollutants in aquatic environment.     

A stochastic model describing the impact of daily rainfall depth distribution on the soil water balance

Simplified, vertically-averaged soil moisture models have been widely used to describe and study eco-hydrological processes in water-limited ecosystems. The principal aim of these models is to understand how the main physical and biological processes linking soil, vegetation, and climate impact on the statistical properties of soil moisture. A key component of these models is the stochastic nature of daily rainfall, which is mathematically described as a compound Poisson process with daily rainfall amounts drawn from an exponential distribution. Since measurements show that the exponential distribution is often not the best candidate to fit daily rainfall, we compare the soil moisture probability density functions obtained from a soil water balance model with daily rainfall depths assumed to be distributed as exponential, mixed-exponential, and gamma. This model with different daily rainfall distributions is applied to a catchment in New South Wales, Australia, in order to show that the estimation of the seasonal statistics of soil moisture might be improved when using the distribution that better fits daily rainfall data. This study also shows that the choice of the daily rainfall distributions might considerably affect the estimation of vegetation water-stress, leakage and runoff occurrence, and the whole water balance.     

Multifaceted Role of Microalgae for Municipal Wastewater Treatment: A Futuristic Outlook toward Wastewater Management

Municipal wastewater (MWW) or urban wastewater (UWW) is generated by the domestic consumption of freshwater, which contains a huge amount of nutrients. The release of unprocessed wastewater causes eutrophication and harms aquatic life. Moreover, ingestion of polluted MWW causes a severe negative impact on human health. Microalgae are unicellular, eukaryotic photosynthetic organisms and have the capability of nutrient assimilation in the presence of light. Moreover, the produced biomass can be used for the generation of value-added bioproducts such as bioenergy. However, conventional microalgae-based MWW treatment is not as sustainable on a commercial scale. Therefore, more advanced approaches using microalgae need to be integrated in wastewater cultivation systems to improve nutrient removal efficiency. Thus, the present review explores the use of microalgae for the removal of nutrients from MWW, provides an outlook of direct and indirect methods of nutrient uptake from wastewater and the effects of the influencing factors in biomass growth. Moreover, the review also gives insight into recent approaches used for MWW treatment and the applications of algal biomass resulting from treated wastewater. It is predicted that microalgae-based MWW treatment systems will be a significant green approach to help eliminate nutrient loads and implement circular economy.     

Soil and water conservation measures improve soil carbon sequestration and soil quality under cashews

Land degradation is becoming a serious problem in the west coast region of India where one of the world's eight biodiversity hotspots,the‘Western Ghats’,is present.Poor land management practices and high rainfall have led to increasing problems associated with land degradation.A long-term(13-year)experiment was done to evaluate the impact of soil and water conservation measures on soil carbon sequestration and soil quality at three different depths under cashew nut cultivation on a 19%slope.Five soil and water conservation measures-continuous contour trenches,staggered contour trenches,halfmoon terraces,semi-elliptical trenches,and graded trenches all with vegetative barriers of Stylosanthes scabra and Vetiveria zizanoides and control were evaluated for their influence on soil properties,carbon sequestration,and soil quality under cashews.The soil and water conservation measures improved significantly the soil organic carbon,soil organic carbon stock,carbon sequestration rate and microbial activity compared to the control condition(without any measures).Among the measures tested,continuous contour trenches with vegetative barriers outperformed the others with respect to soil organic carbon stock,sequestration rate,and microbial activity.The lower metabolic quotient with the measures compared to the control indicated alleviation of environmental stress on microbes.Using principal component analysis and a correlation matrix,a minimum dataset was identified as the soil available nitrogen,bulk density,basal soil respiration,soil pH,acid phosphatase activity,and soil available boron and these were the most important soil properties controlling the soil quality.Four soil quality indices using two summation methods(additive and weighted)and two scoring methods(linear and non-linear)were developed using the minimum dataset.A linear weighted soil quality index was able to statistically differentiate the effect of soil and water conservation measures from that of the control.The highest value of the soil quality index of 0.98 was achieved with continuous contour trenches with a vegetative barrier.The results of the study indicate that soil and water conservation measures for cashews are a potential strategy to improve the soil carbon sequestration and soil quality along with improving crop productivity and reducing the erosion losses.     

Science and technology based earthquake risk reduction strategies: The Indian scenario

Science and Technology (S & T) interventions are considered to be very important in any effort related to earthquake risk reduction. Their three main components are: earthquake forecast, assessment of earthquake hazard, and education and awareness. In India, although the efforts towards earthquake forecast were initiated about two decades ago, systematic studies started recently with the launch of a National Program on Earthquake Precursors. The quantification of seismic hazard, which is imperative in the present scenario, started in India with the establishment of first seismic observatory in 1898 and since then a substantial progress has been made in this direction. A dedicated education and awareness program was initiated about 10 years ago to provide earthquake education and create awareness amongst the students and society at large. The paper highlights significant S & T efforts made in India towards reduction of risk due to future large earthquakes.     

Arsenic distribution along different hydrogeomorphic zones in parts of the Brahmaputra River Valley,Assam (India)

The spatial distribution of arsenic (As) concentrations along three classified hydrogeomorphological zones in the Brahmaputra River Valley in Assam (India) have been investigated: zone I, comprising the piedmont and alluvial fans; zone II, comprising the runoff areas; and zone III, comprising the discharge zones. Groundwater (150 samples) from shallow hand-pumped and public water supply wells (2–60 m in depth) was analysed for chemical composition to examine the geochemical processes controlling As mobilization. As concentrations up to 0.134 mg/L were recorded, with concentrations below the World Health Organization and the Bureau of Indian Standards drinking-water limits of 0.01 mg/L being found mainly in the proximal recharge areas. Eh and other redox indicators (i.e., dissolved oxygen, Fe, Mn and As) indicate that, except for samples taken in the recharge zone, groundwater is reducing and exhibits a systematic decrease in redox conditions along the runoff and discharge zones. Hydrogeochemical evaluation indicated that zone I, located along the proximal recharge areas, is characterized by low As concentration, while zones II and III are areas with high and moderate concentrations, respectively. Systematic changes in As concentrations along the three zones support the view that areas of active recharge with high hydraulic gradient are potential areas hosting low-As aquifers.     

Tectonic Setting of the Kadiri Schist Belt, Andhra Pradesh, India

Plate tectonic activity has played a critical role in the development of petrotectonic associations in the Kadiri schist belt. The calc alkaline association of basalt, andesite, dacite and rhyolite(BADR) is the signature volcanic rock suite of the convergent margin. The N-S belt has gone below the unconformity plane of Cuddapah sediments. In the northern part geochemical and structural attributes of the Kadiri greenstone belt is studied along with microscopic observations of selected samples. Harker diagram plots of major elements generally indicate a liquid line of descent from a common source, such that BADR rocks are derived from a common parent magma of basaltic to andesitic composition. These calc-alkaline volcanic rocks are formed at convergent margins where more silicic rocks represent more highly fractionated melt. All the litho-units of this greenstone belt indicate crush and strain effects. The stretched pebbles in the deformed volcanic matrix with tectonite development along with associated greenschist facies metamorphism, alteration and hydration is remarkable. Flow foliation plane with N-S strike and very low angle(5° to 10°) easterly dip and N-S axial planar schistosity formed due to later phase isoclinal folding can be clearly identified in the field. Basic intrusives are quite common in the surrounding area. All the observations including the field setting and geochemistry clearly demonstrate ocean-continent subduction as the tectonic environment of the study area.