Weathering and landslide occurrences in parts of Western Ghats,Kerala

The climatic condition of Western Ghats has influenced the process of weathering and landslides in this mountainous tract along the southwest coast of India. During the monsoon period, landslides are a common in the Western Ghats, and its intensity depends upon the thickness of the loose unconsolidated soil formed by the process of weathering. Debris landslides with a combination of saprock, saprolite and soil, indicate the role of weathering in landslide occurrences. This paper reports on how the weathering in the windward slope of Western Ghats influences the occurrence of landslides and the factors which accelerate the weathering process. Rock and soil samples were collected from the weathering profile of hornblende gniess and granite gneiss. The chemical analysis and the calculated Chemical Index of Alteration (CIA) indicate the significant weathering and its possible influence on landslide occurrences in the study area. Mainly, the CIA value of lateritic soil and forest loam indicated the extent of high chemical weathering in this region. Rainfall is the dominant parameter influencing the chemical weathering process. In addition, deforestation, land use practices and soil erosion are some of the other important factors accelerating the weathering process and landslide occurrences in the region. The locations of the previous landslides superimposed on geology and soil show that most of the landslide occurrences are associated with the highly weathered zone, particularly lateritic soil and the ‘severe’ (rock outcrop) erodability zone.     

A hydrochemical approach to estimate mountain front recharge in an aquifer system in Tamilnadu,India

Mountain-front recharge (MFR) is a process of recharging an aquifer by infiltration of surface flow from streams and adjacent basins in a mountain block and along a mountain front (MF). This is the first attempt in India to estimate MFR along the foothills of Courtallam using hydrogeochemistry and geostatistical tools. The estimation of MFR has been carried out by collecting groundwater samples along the foothills of Courtallam. Collected water samples were analyzed for major cations and anions using standard procedures. Hydrogeochemical facies show the existence of four water types in this region. Calcium-rich water derived from gneissic rock terrain indicates significant recharge from higher elevation. Log pCO₂ and ionic strength of the samples were also calculated to identify the geochemical process. Majority of the collected samples have sodium-rich water and weak ionic strength, which indicate foothill recharge and low residence time. Silicate and carbonate weathering have an equal interplay along the foothills with a relatively large fraction of Mg from the MF. The spatial diagrams of three factors show that the southern part of the study area is dominated by both weathering and anthropogenic processes, whereas the northern part is dominated by both leaching and weathering processes. Thus, the dominant weathering process represented by the second factor indicates the large recharge process along the foothills.     

Satellite observations of unusual dust event over North-East India and its relation with meteorological conditions

An unusual intense dust storm occurred over North-East region of India on 17 March 2009, which was analyzed using multi-satellite data sets. Terra MODIS AOD₅₅₀ showed high values on 17 March 2009 with low values of Angstrom exponent (α), suggesting coarse mode particle loading in the atmosphere. NCEP temperature and relative humidity anomalies showed high temperature and low humidity during March 2009. Dry weather conditions due to deficit rainfall during January–March 2009 and higher winds resulted in unusual dust storm over the region. Satellite observations of aerosol optical depth variations suggested increased aerosol loading in March 2009 due to dust storm.     

Benthic foraminiferal biofacies on the shelf and upper continental slope off North Kerala (Southwest India)

This study examines benthic foraminifera (>63 μm) both qualitatively and quantitatively, from 19 closely spaced surficial sediment samples covering 30 to 200 m water depths across the shelf and upper continental slope off north Kerala (SW India). A total of 59 species are recorded. The major constituents of benthic foraminiferal assemblages in the study area are fursenkoinids, bolivinids, nonionids, rotaliids, elphidiids, buliminids, miliolids, gavilinellids, amphestiginids, bagginids, vaginulinids, uvigerinids and various agglutinated taxa. Cluster analysis using Bray Curtis similarity index defines four sample groups, each typified by a characteristic assemblage representing a biofacies. The major benthic foraminiferal biofacies identified are: Biofacies I, Fursenkoina-Nonion-Ammonia beccarii s.l. (30–40 m); Biofacies II, Fursenkoina-Nonion (40–55 m); Biofacies III, Bolivina robusta-Hanzawaia-Cancris-Amphistegina and miliolids (55–115 m) and Biofacies IV, Bolivina persiensis-Uvigerina-Bulimina-Fursenkoina and agglutinants (115–200 m). Relict foraminifera, most commonly represented by shallow-water benthic taxa are concentrated on the outer shelf. The relict assemblage appears to be a product of late Pleistocene low sea level. The foraminiferal biofacies have a good correspondence with the bathymetrically distributed three major lithofacies across the shelf and the upper continental slope. We studied the distribution pattern of individual taxa constituting the biofacies. The study demonstrates a relationship between the pattern of distribution of major benthic fauna and the sediment-size and organic carbon content across the inner shelf to upper slope. Additionally, certain taxa appear to be sensitive to various hydrographic parameters, such as, Bulimina marginata to temperature and Fursenkoina complanata and Uvigerina ex gr. U. semiornata to dissolved oxygen level.     

Carcinogenic and Non-carcinogenic Risk Assessment of Metals in Groundwater via Ingestion and Dermal Absorption Pathways for Children and Adults in Malwa Region of Punjab

The concentration of trace metals was measured in groundwater samples collected from Malwa region of Punjab, India. The samples were analyzed by using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The results were compared with permissible limits prescribed by various health and environmental protection agencies. The concentrations of trace metals such as Mn, Se, Mo, Cd, Sb and Pb were higher than their respective permissible limits at some sampling sites. The total hazard index (HI_total) (summing the hazard index through ingestion and dermal routes) at all the sampling sites exceeded or nearing unity, indicating the presence of non-carcinogenic health effects from ingestion of groundwater and dermal contact with groundwater. The results reveal that the total excess lifetime cancer risk (ELCR_total) of metals exposure was in accordance with the acceptable lifetime risks for carcinogens in drinking water.     

Quasi-static deformation due to two-dimensional seismic sources embedded in an elastic half-space in welded contact with a poroelastic half-space

The Biot linearized theory of fluid saturated porous materials is used to study the plane strain deformation of a two-phase medium consisting of a homogeneous, isotropic, poroelastic half-space in welded contact with a homogeneous, isotropic, perfectly elastic half-space caused by a two-dimensional source in the elastic half-space. The integral expressions for the displacements and stresses in the two half-spaces in welded contact are obtained from the corresponding expressions for an unbounded elastic medium by applying suitable boundary conditions at the interface. The case of a long dip-slip fault is discussed in detail. The integrals for this source are solved analytically for two limiting cases: (i) undrained conditions in the high frequency limit, and (ii) steady state drained conditions as the frequency approaches zero. It has been verified that the solution for the drained case (ω → 0) coincides with the known elastic solution. The drained and undrained displacements and stresses are compared graphically. Diffusion of the pore pressure with time is also studied.     

Studying Land Use Travel Demand Interaction Using 3S Technology for Tiruchirappalli City

This paper gives an overview of a major application of modern geospatial tools such as remote sensing, GIS and GPS, i.e., 3S technology in estimating travel demand along Indian roads by considering the study area, Tiruchirappalli urban city in Tamil Nadu. In the study, an attempt was made to estimate travel demand based on the current land-use classification as the pattern of travel depends on the type of land use activity in a zone. IRS high resolution image Cartosat-1 of year 2009 was used to extract the land-use information required. The travel demand model developed was validated with the field obtained OD-matrix to understand the accuracy of the method considered.