Distribution of arsenic and mercury in subtropical coastal beachrock,Gulf of Mannar,India

An assessment of coastal pollution was made on the basis of trace element concentrations (arsenic — As, mercury — Hg) in the Gulf of Mannar. The beachrock samples were collected along the coastal tracts between Rameswaram and Kanyakumari. The samples were dried and digested to determine the As and Hg using atomic absorption spectrophotometer (AAS-air-acetylene and nitrous oxide method). The As and Hg accumulation status of the beachrock was assessed using geo-accumulation index values (I _geo). The accumulation of As and Hg in the beachrock ranges from 2.75 to 20.72 μg g⁻¹ and from 0.06 to 0.31 μg g⁻¹, respectively. The As and Hg concentrations in the beachrocks are compared with crustal average values and average of other region sediments. The possible source of the contamination is from atmospheric deposition and anthropogenic activities.     

Expected peak ground acceleration in Uttarakhand Himalaya,India region from a deterministic hazard model

A method of seismic zonation based on the deterministic modeling of rupture planes is presented. Finite rupture planes along identified lineaments are modeled in the Uttarakhand Himalaya based on the semi empirical technique of Midorikawa (Tectonophysics 218:287–295, 1993). The expected peak ground acceleration thus estimated from this technique is divided into different zones similar to zones proposed by the Bureau of Indian standard, BIS (Indian standards code of practice for earthquake-resistant design of structures, 2002). The proposed technique has been applied to Kumaon Himalaya area and the surrounding region for earthquakes of magnitude M > 6.0. Approximately 56000 km² study area is classified into the highest hazard zone V with peak accelerations of more than 400 cm/s². This zone V includes the cities of the Dharchula, Almora, Nainital, Haridwar, Okhimath, Uttarkashi, Pithorahargh, Lohaghat, Munsiari, Rudraprayag, and Karnprayag. The Sobla and Gopeshwar regions belong to zone IV, where peak ground accelerations of the order from 250 to 400 cm/s² can be expected. The prepared map shows that epicenters of many past earthquakes in this region lie in zone V, and hence indicating the utility of developed map in defining various seismic zones.     

The Nature and Distribution of Particulate Matter in the Mandovi Estuary,Central West Coast of India

Systematic seasonal variations of suspended particulate matter (SPM) along a 44-km transect of the Mandovi estuary reveal that the concentrations of SPM are low at river-end stations, increase generally seaward, and are highest at sea-end stations of the estuary. An estuarine turbidity maximum (ETM) occurs at sea-end stations during June–September when river discharge is high and also in February–May when river discharge is low. These are the two windiest times of year, the former associated with the southwest monsoon and the latter characterized by a persistent sea breeze. The salinity vs. SPM plot shows that high SPM is a seaward deposit and skewed landward. Suspended matter comprised of floccules, fecal pellets, and aggregates that consist of clay and biogenic particles occur everywhere in the estuary. Diatoms are the most common and are of marine type at the sea-end and freshwater-dominated at river-end stations of the estuary. SPM is characterized by kaolinite- and smectite-rich clay mineral suites at the river- and sea-end stations, respectively. Smectite concentrations increase seawards with the increase in SPM content and are not influenced by salinity. Wind-driven waves and currents and biogeochemical processes at the mouth of estuary likely play an important role in the formation of ETM in resuspension and transformation of SPM into floccules and aggregates and in their upkeep or removal.     

Mechanism and geochemical implications of the Late Holocene organic carbon burial event: an example from the southwest coast of India

Carbonaceous clay found in the palaeo-deposits of Meenachil River basin was analysed for the total organic carbon, nitrogen and textural characters. Radiocarbon dating of this clay formation and the embedded carbonized wood fragments was also done. The values obtained for the organic carbon, nitrogen and C/N ratio of the carbonaceous clay exhibited a very remarkable range, suggestive of different environmental conditions of formation. It is evident from the present study that since the lignin and cellulose are the dominant components of terrestrial higher plants, allochthonous and submerged organic matter have high C/N ratio. The radio carbon dating of the sediment and wood samples suggested that the palaeo-deposits of Meenachil River basin were formed as result of many transgrassive–regressive episodes, which had started even before the formation of Vembanad Lake. The formation of carbonaceous clay, as found sandwiched in palaeo-deposits, was due to the global eustatic sea-level fluctuations and tectonism.     

Geophysical and tracer studies to detect subsurface chromium contamination and suitable site for waste disposal in Ranipet,Vellore district,Tamil Nadu,India

A chemical factory near Ranipet town in Vellore district, in the state of Tamil Nadu, India produced chromium-based inorganic chemicals. The factory area in granite gnessic terrain receives an average annual rainfall of 1,000 mm. About 1.5 lakh tons of solid wastes rich in hexavalent chromium (Cr⁶⁺), spreading over an area of 14,000 m² (about 3.5 acres), having about 4 m thickness, is accumulated in an open yard within the factory premises. The soil and groundwater in and around the factory area are contaminated with Cr⁶⁺ leached from dump site. Cr⁶⁺ is carcinogenic in nature and when leached in water can lead to respiratory disorders. Resistivity surveys comprising vertical electrical sounding, multielectrode resistivity imaging, drilling of bore wells, chemical analysis of soil, formation and groundwater samples and bore hole tracer studies were carried out within the factory and adjoining areas to decipher subsurface geology, hydraulic behavior of dyke as natural barrier and lateral and vertical extent of pollution zone in and around the chromium dump site. The data obtained were integrated and interpreted for understanding the pollution migration and its impact on environment. Remedial measures are suggested for containing the contamination.     

Projected climate change impacts on spatial distribution of bioclimatic zones and ecoregions within the Kailash Sacred Landscape of China,India, Nepal

Rapidly accelerating climate change in the Himalaya is projected to have major implications for montane species, ecosystems, and mountain farming and pastoral systems. A geospatial modeling approach based on a global environmental stratification is used to explore potential impacts of projected climate change on the spatial distribution of bioclimatic strata and ecoregions within the transboundary Kailash Sacred Landscape (KSL) of China, India and Nepal. Twenty-eight strata, comprising seven bioclimatic zones, were aggregated to develop an ecoregional classification of 12 ecoregions (generally defined by their potential dominant vegetation type), based upon vegetation and landcover characteristics. Projected climate change impacts were modeled by reconstructing the stratification based upon an ensemble of 19 Earth System Models (CIMP5) across four Representative Concentration Pathways (RCP) emission scenarios (i.e. 63 impact simulations), and identifying the change in spatial distribution of bioclimatic zones and ecoregions. Large and substantial shifts in bioclimatic conditions can be expected throughout the KSL area by the year 2050, within all bioclimatic zones and ecoregions. Over 76 % of the total area may shift to a different stratum, 55 % to a different bioclimatic zone, and 36.6 % to a different ecoregion. Potential impacts include upward shift in mean elevation of bioclimatic zones (357 m) and ecoregions (371 m), decreases in area of the highest elevation zones and ecoregions, large expansion of the lower tropical and sub-tropical zones and ecoregions, and the disappearance of several strata representing unique bioclimatic conditions within the KSL, with potentially high levels of biotic perturbance by 2050, and a high likelihood of major consequences for biodiversity, ecosystems, ecosystem services, conservation efforts and sustainable development policies in the region.     

Appraisal of land use/land cover of mangrove forest ecosystem using support vector machine

Human activities in many parts of the world have greatly changed the natural land cover. This study has been conducted on Pichavaram forest, south east coast of India, famous for its unique mangrove bio-diversity. The main objectives of this study were focused on monitoring land cover changes particularly for the mangrove forest in the Pichavaram area using multi-temporal Landsat images captured in the 1991, 2000, and 2009. The land use/land cover (LULC) estimation was done by a unique hybrid classification approach consisting of unsupervised and support vector machine (SVM)-based supervised classification. Once the vegetation and non-vegetation classes were separated, training site-based classification technology i.e., SVM-based supervised classification technique was used. The agricultural area, forest/plantation, degraded mangrove and mangrove forest layers were separated from the vegetation layer. Mud flat, sand/beach, swamp, sea water/sea, aquaculture pond, and fallow land were separated from non-vegetation layer. Water logged areas were delineated from the area initially considered under swamp and sea water-drowned areas. In this study, the object-based post-classification comparison method was employed for detecting changes. In order to evaluate the performance, an accuracy assessment was carried out using the randomly stratified sampling method, assuring distribution in a rational pattern so that a specific number of observations were assigned to each category on the classified image. The Kappa accuracy of SVM classified image was highest (94.53 %) for the 2000 image and about 94.14 and 89.45 % for the 2009 and 1991 images, respectively. The results indicated that the increased anthropogenic activities in Pichavaram have caused an irreversible loss of forest vegetation. These findings can be used both as a strategic planning tool to address the broad-scale mangrove ecosystem conservation projects and also as a tactical guide to help managers in designing effective restoration measures.     

Impact of Doppler weather radar data on thunderstorm simulation during STORM pilot phase—2009

This study assesses the impact of Doppler weather radar (DWR) data (reflectivity and radial wind) assimilation on the simulation of severe thunderstorms (STS) events over the Indian monsoon region. Two different events that occurred during the Severe Thunderstorms Observations and Regional Modeling (STORM) pilot phase in 2009 were simulated. Numerical experiments—3DV (assimilation of DWR observations) and CNTL (without data assimilation)—were conducted using the three-dimensional variational data assimilation technique with the Advanced Research Weather Research and Forecasting model (WRF-ARW). The results show that consistent with prior studies the 3DV experiment, initialized by assimilation of DWR observations, performed better than the CNTL experiment over the Indian region. The enhanced performance was a result of improved representation and simulation of wind and moisture fields in the boundary layer at the initial time in the model. Assimilating DWR data caused higher moisture incursion and increased instability, which led to stronger convective activity in the simulations. Overall, the dynamic and thermodynamic features of the two thunderstorms were consistently better simulated after ingesting DWR data, as compared to the CNTL simulation. In the 3DV experiment, higher instability was observed in the analyses of thermodynamic indices and equivalent potential temperature (θ _e) fields. Maximum convergence during the mature stage was also noted, consistent with maximum vertical velocities in the assimilation experiment (3DV). In addition, simulated hydrometeor (water vapor mixing ratio, cloud water mixing ratio, and rain water mixing ratio) structures improved with the 3DV experiment, compared to that of CNTL. From the higher equitable threat scores, it is evident that the assimilation of DWR data enhanced the skill in rainfall prediction associated with the STS over the Indian monsoon region. These results add to the body of evidence now which provide consistent and notable improvements in the mesoscale model results over the Indian monsoon region after assimilating DWR fields.     

提孜那甫河流域地表太阳辐射估算及其影响因素分析

地表太阳辐射是地球表层主要能量来源,对地表能量平衡、能量交换以及生态水文过程等具有决定性意义。山区地形复杂,其地表太阳辐射时空差异较大且较难估算。采用适用于山区的地表太阳辐射模型对西北昆仑山提孜那甫河流域地表太阳辐射时空分布进行了估算,分析了该流域季节太阳辐射空间分布规律并探讨了地形和云2个重要因素对太阳辐射空间分布的影响。结果表明:（1） 地形因子中周围地形阻挡即地形开阔度（Sky view factor,SVF）与年总太阳辐射的关系最为显著,太阳辐射随SVF增加而增加。（2） 年总太阳辐射随着高程增加首先减少,再而随之增加。探究SVF随高程的变化,发现其与太阳辐射随高程的变化趋势较为一致,因此在山区复杂地形下地表太阳辐射估算中仅利用高程对其校正存在明显不足,需综合考虑地形效应。（3） 研究计算了季节云出现频率空间分布与太阳辐射空间分布的相关系数,结果表明夏季太阳辐射受云影响较其他季节显著。定量分析了地形因子以及云对地表太阳辐射空间分布影响的贡献率,周围地形阻挡SVF对地表太阳辐射空间分布的影响最大,高程和云次之。因此综合考虑地形和云对太阳辐射的影响在山区太阳辐射模拟中是非常必要的,研究可为山区地表太阳辐射模拟提供理论依据,并为山区生态水文过程研究提供方法支撑。     

Estimation of Nash's IUH parameters using stochastic search algorithms

In rainfall–runoff studies, it is often necessary to change the duration of a given unit hydrograph. Nash's Instantaneous Unit Hydrograph (IUH) is an ideal method that eliminates the hydrograph duration. This paper presents the results of the application of search algorithms, namely a genetic algorithm and hill climbing, to develop the IUH that minimizes the error between the observed and generated hydrographs. Also the performance of these methods has been compared with that of the classical method used for estimation of IUH, namely the method of moments. The genetic algorithm is a popular search procedure for function optimization that applies the mechanics of natural genetics and natural selection to explore a given search space. Hill climbing is an optimization technique that belongs to the family of local search and algorithms can be used to solve problems that have many solutions, with some solutions better than others. The results obtained from both the genetic algorithm and hill climbing algorithm for estimation of Nash's IUH parameters were compared with the results obtained by the method of moments for storms from two river basins that are located in different climatic regions. It was found that both the genetic algorithm and hill climbing provided improved and consistent results. Copyright © 2008 John Wiley & Sons, Ltd.