Seasonal variation in major ion chemistry of a tropical mountain river,the southern Western Ghats,Kerala, India

A comprehensive and systematic study to understand various geochemical processes as well as process drivers controlling the water quality and patterns of the hydrochemical composition of river water in Muthirapuzha River Basin, MRB (a major tributary of Periyar, the longest river in Kerala, India), was carried out during various seasons, such as monsoon, post-monsoon and pre-monsoon of 2007–2008, based on the data collected at 15 monitoring stations (i.e., 15 × 3 = 45 samples). Ca²⁺ and Mg²⁺ dominate the cations, while Cl^? followed by HCO₃ ^? dominates the anions. In general, major ion chemistry of MRB is jointly controlled by weathering of silicate and carbonate rocks, which is confirmed by relatively larger Ca²⁺ + Mg²⁺/Na⁺ + K⁺ ratios as well as Ca²⁺/Na⁺ vs. Mg²⁺/Na⁺ and Ca²⁺/Na⁺ vs. HCO₃ ^?/Na⁺ scatter plots. The relationship between Cl^? and Na⁺ implies stronger contributions of anthropogenic activities modifying the hydrochemical composition, irrespective of seasons. The water types emerged from this study are transitional waters or waters that changed their chemical character by mixing with waters of geochemically different ionic signatures. However, various ionic ratios, hydrochemical plots and graphical diagrams suggest seasonality over the hydrochemical composition, which is solely controlled by the rainfall pattern. Relatively higher pCO₂ indicates the disequilibrium existing in natural waterbodies vis-à-vis the atmosphere, which is an outcome of both the contribution of groundwater to stream discharge and anthropogenic activities. Hence, continuous monitoring of hydrochemical composition of mountain rivers is essential in the context of climate change, which has serious implications on tropical mountain fluvial-hydro systems.     

An information systems approach to the preservation of biological diversity

Abstract

Although biological diversity has emerged in the 1980s as a major scientific and political issue, efforts at scientific assessment have been hampered by the lack of cohesive sets of data. We describe, in concept, a comprehensive national diversity information system, using geographical information system (GIS) techniques to organize existing data and improve spatial aspects of the assessment. One potential GIS analysis, to identify gaps in the network of nature reserves for California, is discussed in greater detail. By employing an information systems approach, available data can be used more effectively and better management strategies can be formulated.     

MIT's Computer Resource Lab:

Abstract

The paper describes the curriculum on geographic information systems developed in the Department of Planning at the Massachusetts Institute of Technology for those studying for the Master in City Planning degree. Particular emphasis is given to the part played by the Computer Resources Lab in serving the needs of the architecture and planning departments, the interactions between teaching and research, and those between the course and professional practice. The required courses are outlined and the wide range of recommended courses, drawn from a number of departments in the Institute, are listed- The authors emphasize the necessity of their being at the forefront of research if they are lo maintain the flow of hardware and software from contacts and donations on which their research and teaching depend.     

Morphometrical analysis of two tropical mountain river basins of contrasting environmental settings, the southern Western Ghats, India

The morphometric analysis of river basins represents a simple procedure to describe hydrologic and geomorphic processes operating on a basin scale. A morphometric analysis was carried out to evaluate the drainage characteristics of two adjoining, mountain river basins of the southern Western Ghats, India, Muthirapuzha River Basin (MRB) in the western slopes and Pambar River Basin (PRB) in the eastern slopes. The basins, forming a part of the Proterozoic, high-grade, Southern Granulite Terrain of the Peninsular India, are carved out of a terrain dominantly made of granite- and hornblende-biotite gneisses. The Western Ghats, forming the basin divide, significantly influences the regional climate (i.e., humid climate in MRB, while semi-arid in PRB). The Survey of India topographic maps (1:50,000) and Shuttle Radar Topographic Mission digital elevation data were used as the base for delineation and analysis. Both river basins are of 6th order and comparable in basin geometry. The drainage patterns and linear alignment of the drainage networks suggest the influence of structural elements. The Rb of either basins failed to highlight the structural controls on drainage organization, which might be a result of the elongated basin shape. The irregular trends in Rb between various stream orders suggest the influence of geology and relief on drainage branching. The Dd values designate the basins as moderate- to well-drained with lower infiltration rates. The overall increasing trend of Rl between successive stream orders suggests a geomorphic maturity of either basins and confirmed by the characteristic I _hyp values. The Re values imply an elongate shape for both MRB and PRB and subsequently lower vulnerability to flash floods and hence, easier flood management. The relatively higher Rr of PRB is an indicative of comparatively steeply sloping terrain and consequently higher intensity of erosion processes. Further, the derivatives of digital elevation data (slope, aspect, topographic wetness index, and stream power index), showing significant differences between MRB and PRB, are useful in soil conservation plans. The study highlighted the variation in morphometric parameters with respect to the dissimilarities in topography and climate.     

Seasonal variations and trophic ecology of microzooplankton in the southeastern Arabian Sea

The seasonal ecological response of microzooplankton in the southeastern Arabian Sea is presented. During the spring intermonsoon period, stratification and depletion of nitrate in the surface waters (nitracline was at 60 m depth) cause low integrated chlorophyll a (av. 19±11.3 mg m⁻²) and primary production (av. 164±91 mgC m⁻² d⁻¹). On the other hand, nutrient enrichment associated with coastal upwelling and river influx during the onset and peak summer monsoon resulted in high integrated chlorophyll a (av. 21±6 mg m⁻² and av. 29±21 mg m⁻², respectively) and primary production (av. 255±94 mgC m⁻² d⁻¹ and av. 335±278 mgC m⁻² d⁻¹, respectively). During all three periods, diazotropic cyanobacterium Trichodesmium erythraeum dominated in the nutrient depleted surface waters. A general increase in abundance of larger diatoms was evident in the surface waters of the inshore region during monsoon periods. The microzooplankton abundance was found to be significantly higher during the spring intermonsoon (av.241±113×10³ ind m⁻²) as compared to onset of summer monsoon (av. 105±89×10³ ind m⁻²) and peak summer monsoon (av.185±175×10³ ind m⁻²). Microzooplankton community during the spring intermonsoon was numerically dominated by ciliates while heterotrophic dinoflagellate was the dominant ones during the monsoon periods. The high abundance of ciliates during the spring intermonsoon could be attributed to the stratified environmental condition prevailed in the study area which favors high abundance of smaller phytoplankton and cyanobacteria, the most preferred food of ciliates. On the other hand, the dominance of heterotrophic dinoflagellates during the monsoon periods could be linked to their ability to graze larger diatoms which were abundant during the monsoon periods. The overall results show low abundance of microzooplankton in the eastern Arabian Sea during the monsoon periods mainly due to a decline in ciliates abundance. This decline during the monsoon periods could be the result of (a) low abundance of smaller phytoplankton and (b) high stock of mesozooplankton predators (av. 245 ml 100 m⁻³).     

FACTOR ANALYSIS OF A SIMULATED DATA MATRIX INVOLVING AQUEOUS COMPLEX EQUILIBRIA

Abstract factor analyses were performed on databases consisting of simulated samples from aqueousequilbria.The program COMPLEX was used to generate equilibrium species in a system of three reactantmetals and five reactant bases.Reactant concentrations and pH were drawn from random-normaldistributions so that sample data vectors comprised a multivariate log-normal distribution of equilibriumconcentrations.In addition,sample groups were created containing different distributions for pH andreactant concentrations.Equilibrium species were shown to contain variance contributed by change in pH among samples aswell as change in reactant concentrations.Factor modelling revealed the qualitative relationships amongthe species and how the relationships change with pH.Factors also revealed those reactants containingvariance in the data matrix.In some cases,reactant variance obscured relationships between pH and theequilibrium species.Since factor modelling of a simulated data matrix revealed the expected chemical equilibriuminteractions,a potentially powerful tool exists for investigating the effects of outliers and error.     

Sapphirine+Forsterite and Sapphirine+Humite-Group Minerals in an Ultra-Magnesian Lens from Kuhi-lal, SW Pamirs, Tajikistan: Are these Assemblages Forbidden?

Sapphirine occurs with humite-group minerals and forsteritein Precambrian amphibole-facies rocks at Kuhi-lal, SW PamirMountains, Tajikistan, a locality also for talc+kyanite magnesiohornblendewhiteschist. Most of these sapphirine-bearing rocks are graphiticand sulfidic (pyrite and pyrrhotite) and contain enstatite,clinohumite or chondrodite, spinel, rutile, gedrite, and phlogopite.A phlogopite schist has the assemblage with X_Fe = Fe/(Fe+Mg)increasing as follows: chlorite (0-003)<phlogopite (0.004–0.005)sapphirine (0.004–0.006) enstatite (0-006)forsterite (0-006–0-007)<spinel (0-014). This assemblage includes the incompatiblepair sapphirine+forsterite, but there is no textural evidencefor reaction. In one rock with clinohumite, X_Fe increases asfollows: clinohumite (0-002) <sapphirine (0-003) <enstatite(0-004–0-006) <spinel (0-010). Ion microprobe and wet-chemicalanalyses give 0-57–0-73 wt.% F in phlogopite and 0-27wt.% F in chlorite in the phlogopite schist; 0-04, 1.5–1.9,and 4.4 wt.% F in forsterite, clinohumite, and chondrodite,respectively; and 0-0-09 wt.% BeO and 0-05–0-21 wt.% B₂O₃in sapphirine. Stabilization of sapphirine+clinohumite or sapphirine+chondroditeinstead of sapphirine+phlogopite is possible at high F contentsin K-poor rocks, but minor element contents appear to be toolow to stabilize sapphirine as an additional phase with forsterite+enstatite+spinel.Although sapphirine+forsterite is metastable relative to spinel+enstatitein experiments conducted at a_H2O=1 in the MgO-Al₂O₃-SiO₂-H₂Osystem, it might be stabilized at a_H2O0.5, P4 kbar, T650–700C.Textures in the Kuhi-lal whiteschists suggest a polymetamorphicevolution in which the rocks were originally metamorphosed atT650C, P 7 kbar, conditions under which sapphirine+clinohumiteand sapphirine+chondrodite are inferred to have formed, andsubsequently affected by a later event at lower P, similar T,and lower a_H2O. The latter conditions were favorable for sapphirine+forsteriteto form in a rock originally containing chlorite+forsterite+spinel+enstatite.