Paleoclimatic and diagenetic history of the late quaternary sediments in a core from the Southeastern Arabian Sea: Geochemical and magnetic signals

Geochemical and rock-magnetic investigations were carried out on a sediment core collected from the SE Arabian Sea at 1420 m depth in oxygenated waters below the present-day oxygen minimum zone. The top 250 cm of the core sediments represent the last 35 kaBP. The · ¹⁸O values of Globigerinoides ruber are heaviest during the Last Glacial Maximum (LGM) and appear unaffected by low-saline waters transported from the Bay of Bengal by the strong northeast monsoon and West Indian coastal current. The signatures of Bølling-Allerød and Younger Dryas events are distinct in the records of magnetic susceptibility, organic carbon (OC) and · ¹⁸O. Glacial sediments show higher OC, CaCO₃, Ba, Mo, U and Cd, while the early-to-late Holocene sediments show increasing concentrations of OC, CaCO₃, Ba, Cu, Ni and Zn and decreasing concentrations of Mo, U and Cd. Productivity induced low-oxygenated bottom waters and reducing sedimentary conditions during glaciation, and productivity and oxygenated bottom waters in the Holocene are responsible for their variation. The core exhibits different stages of diagenesis at different sediment intervals. The occurrence of fine-grained, low-coercivity, ferrimagnetic mineral during glacial periods is indicative of its formation in organic-rich, anoxic sediments, which may be analogous to the diagenetic magnetic enhancement known in sapropels of the Mediterranean Sea and Japan Sea. The glacial sediments exhibiting reductive diagenesis with anoxic sedimentary environment in this core correspond to reductive diagenesis and intermittent bioturbation (oxygenation) reported in another core in the vicinity. This suggests that the poorly oxygenated bottom water conditions during glacial times should not be generalized, but are influenced locally by productivity, sedimentation rates and sediment reworking.     

WETLAND TYPES AND ASSOCIATE VEGETATION IN NEPAL:AN OVERVIEW

The lands with water,in general,are consideredas wetlands.The wetlands are most complex andhighly productive but more vulnerable ecosystem inthe earth.The wetland systems directly support mil-lions of people and provide good and services to theworld.They …     

Bi‐Solute Sorption of Estrogens at Low Concentration: Two‐ and Three‐Parametric Analysis

Competitive sorption of estriol (E3) and 17α‐ethinylestradiol (EE2) was studied on activated charcoal. Better sorption of E3 (88.9%) and EE2 (69.5%) was observed with single‐solute sorption system than with bi‐solute sorption system. Single‐solute sorption kinetics of E3 and EE2 were evaluated with two (Langmuir and Freundlich) and three (dual mode and Song) parameter models. Freundlich model (R², 0.9915 (E3); 0.9875 (EE2)) showed good prediction compared to other models for single‐solute sorption. Adsorption capacity documented reduced efficacy (86.4% (E3); 65.9% (EE2)) due to induced competitive behavior between the estrogens in aqueous phase. Bi‐solute adsorption kinetics of E3 and EE2 were described by IAST with two and three parameter models. Among these models, IAST‐Freundlich model (R², 0.9765 (E3); 0.9985 (EE2)) was best in predicting bi‐solute sorption of E3 and EE2 by activated charcoal. All these models showed favorable representation of both single‐ and bi‐solute sorption behaviors.     

Two-dimensional interpretation of gravity anomalies over sedimentary basins with an exponential decrease of density contrast with depth

The decrease of density contrast with depth in sedimentary basins is approximated by an exponential function. The anomaly equation, in frequency domain, of a prismatic model with an exponential density function is derived. The method has been extended to derive the Fourier transforms of the gravity anomalies of the sedimentary basin, wherein the basin is viewed as vertical prisms placed in juxtaposition. The gravity anomalies of the sedimentary basin are obtained by taking the inverse Fourier transforms. Filon’s method has been extended for calculating accurate inverse Fourier transforms. The accuracy of the method has been tested using a synthetic example. A combination of space and frequency domain methods have been developed for inversion of gravity anomalies over the sedimentary basin. The method has been applied to interpret one synthetic profile and one field profile over the Godavari basin. The method developed in this paper to calculate the inverse Fourier transforms yields continuous spectrum with accurate values. The maximum depth deduced from the gravity anomalies is of the same order as the depth encountered to the basement at the Aswaraopeta borewell.     

Climate change and finger millet: Perception,trend and impact on yield in different ecological regions in Central Nepal

The views of local people on climate change along different ecological regions are relatively unexplored in Nepal. This study was conducted in 13 villages in central Nepal at different altitudes to document the views of small holder farmers and compare their perception with trends of climatic variables, finger millet yield, natural disasters, plant phenology(flowering and fruiting), status of forest and wild life, as well as the spread of diseases and pests. Analysis on the climatic data of stations for 36-41 years between 1975 and 2016 showed significant increases in the minimum temperature in lower tropical climatic region(500 m), upper tropical to subtropical climatic region(500-2000 m) and temperate climatic region(2000-3000 m) by 0.01, 0.026 and 0.054℃/year, respectively, and an increase of maximum temperature by 0.008, 0.018, and 0.019℃/year, respectively. Rainfall showed a strongly significant decreasing trend in all elevation regions. This result matches with the views of respondents except 38% respondent from temperate climatic region. People from the temperate climatic region also mentioned that current onset of snowfall is delayed but amount of snowfall remained the same. From the documented records, except events of wild fire, frequency of natural disasters events have increased in the recent years, which was in harmony with the views of local people. Multi-linear regression analysis showed that contribution of climatic variables on finger millet yield in lower tropical climatic region and upper tropical to subtropical regions was 23% and 57.3%, respectively, which was supported by increasing trend on average growing degree day(GDD) temperature at the rate of 0.01℃ in upper tropical to subtropical region and 0.007℃ in lower tropical climatic region yearly. Finger millet yield has been increasing at the rate of 7.39 and 36.9 kg/ha yearly in lower tropical climatic region and upper tropical to subtropical climatic region, respectively. This result provides deeper understanding of people's perception of causes and effects of climate change on diverse variables along different elevation and related magnitude which can contribute to policy making in Nepal.     

Predicting suitable habitat of an invasive weed Parthenium hysterophorus under future climate scenarios in Chitwan Annapurna Landscape,Nepal

Chitwan-Annapuma Landscape(CHAL)in central Nepal is known for its rich biodiversity and the landscape is expected to provide corridors for species range shift in response to climate change.Environmental assessments have identified biological invasions and other anthropogenic activities as major threats to the biodiversity in the CHAL.One of the rapidly spreading Invasive Alien Plant species(IAPs)in the CHAL is Parthenium hysterophorus L.,a neotropical invasive weed of global significance.This study aimed to investigate the current and future projected suitable habitat of P.hysterophorus in the CHAL using MaxEnt modelling in three"Representative Concentration Pathways"(RCPs 2.6,4.5 and 8.5)corresponding to different greenhouse gases emissiontrajectories for the year 2050 and 2070.A total of 288species occurrence points,six bioclimatic variablesmean diurnal range,isothermality,annual precipitation,precipitation of driest month,precipitation seasonality,precipitation of driest quarter and two topographic variables(aspect and slope)were selected for MaxEnt modelling.Potential range shift in terms of increase or decline in the suitable habitat areas under the projected scenarios were calculated.Slope and annual precipitation were the most important variables that explained the current distribution of P.hysterophorus.Twenty percent of the total area of CHAL was predicted to be suitable habitat for the growth of P.hysterophorus in the current climatic condition.Highest gain in the suitable habitat of this noxious weed was found under RCP 4.5 scenario in 2050 and 2070.whereas there will be a loss in thesuitable habitat under RCP 8.5 scenario in 2050 and2070.Out of four physiographic regions present in CHAL,three regions-Siwalik,Middle Mountain and High Mountain have suitable habitat for P.hysterophorus under current climatic condition.The mountainous region is likely to be affected more than the Siwalik region by further spread of P.fhysteropfhorus in the future under low(RCP 2.6)to medium(RCP 4.5)emission scenarios.The suitable habitat for this weed is likely to increase in the protected areas of mountain regions(Langtang National Park,Annapurna Conservation Area and Manaslu Conservation Area)in the future.The results have revealed a risk of spreading P.hysterophorus from present localities to non-invaded areas in the current and future climatic condition.Such risk needs to be considered by decision makers and resource managers while planning for effective management of this weed to reduce its ecological and economic impacts in the CHAL.     

Diatoms from surface sediments of Enderby Basin of Indian Sector of Southern Ocean

Diatoms from surface sediment samples collected from Enderby Basin of Indian Sector of Southern Ocean were analyzed to determine the relative abundance and distribution of seven key indicator diatom species viz. Sea ice related species Fragilariopsis rhombica, F. separanda, F. curta, F. ritscheri, Thalassiosira tumida and Actinocyclus actinochilus and Open Ocean species F. kerguelensis on the basis of modern physico-chemical parameters. The relative abundances of different species observed viz. F. rhombica — 6.25%; F. separanda — 12.5%; F. curta — 10.53–13.33%; F. ritscheri — 4.55–12.5%; F. kerguelensis — 6.25–63.64%; T. tumida — 3.13% and A. actinochilus — 9.38–13.33%. The increasing abundance of F. kerguelensis consecutively suggests the effect of Antarctic bottom water in the study area which is further substantiated by the presence and increasing abundance of F. ritscheri. The gradual decrease in abundance or absence of sea ice related species from the sampled stations indicates the summer and winter sea ice extent concentration in the study area. The nutrient concentration correlates with the distribution and abundances of diatom species.     

Effect of Co‐culture and Nutrients Supplementation on Bioremediation of Crude Petroleum Sludge

Ex‐situ bioremediation of real‐field crude petroleum sludge was evaluated to elucidate the role of co‐culture (bioaugmentation) and external nutrients supplementation (biostimulation) under anaerobic microenvironment. Maximum removal of total petroleum hydrocarbons (TPH) was observed by integrating biostimulation with bioaugmentation (R5, 44.01%) followed by bioaugmentation alone (R4, 34.47%), co‐substrate supplemented operations [R6, 23.36%; R3, 16.5%; R2, 9.88%] and control (R1, 4.36%). Aromatics fraction showed higher degradation in all the conditions studied. Fate of six selected polycyclic aromatic hydrocarbons (PAHs) was evaluated during bioremediation. Among these, four ring PAHs compounds showed good degradation by integration of biostimulation with bioaugmentation (R5) while bioaugmentation alone (R4) documented good degradation of three ring PAHs. Lower ring PAHs compounds showed good degradation with the application of biostimulation (R6). Fluorescent in situ hybridization (FISH) detected the presence of known PAHs degrading microorganisms viz., Bacillus, Pseudomonas, Acido bacteria, Sulphur reducing bacteria Firmicutes, etc. Application of biostimulation and bioaugmentation strategies alone or in combinations documented noticeable influence on the degradation of petroleum sludge.     

Role of dynamics in the advection of aerosols over the Arabian Sea along the west coast of peninsular India during pre-monsoon season: A case study based on satellite data and regional climate model

The circulation dynamics of an event marked by the formation of an aerosol cluster off the coast of Maharashtra on April 22, 2006, its southward migration along the Indian west coast with a mean speed of ~200 km/day and its final dissipation after reaching the end of the peninsula by April 28, 2006 as revealed by MODIS (Moderate Resolution Imaging Spectroradiometer) against the pre-monsoon conditions of April 2006 are examined in this study. The maximum aerosol concentration in the cluster was found getting confined to lower and lower altitudes during its southward movement. The NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis wind field indicates that the atmospheric circulation, especially the horizontal wind convergence is the major factor that guides the formation and the dynamics of the cluster. Fine mode fraction from MODIS suggests that the cluster mainly consists of coarse dust particles. The regional climate model, RegCM3 with an efficient dust generation module simulates the formation and movement of the cluster appreciably well. The simulations which also exhibit the altitudinally descending nature of the cluster during its southward movement confirm the mechanism which governs the cluster dynamics suggested based on MODIS and NCEP/NCAR reanalysis data.